[Objectives]Based on a long-term experiment in black soil in Gongzhuling City,we analyzed the changes of maize yield and nitrogen fertilizer efficiency and the correlation between nitrogen use efficiency(NUE)and soil nutrient contents,aiming to provide scientific references for establishing manure fertilization mode and improving NUE.[Methods]Treatments of no fertilization(CK),N fertilization(N),P and K fertilization(PK)and NPK fertilization(NPK),combined with different manure rates(0,30 and 60 t/hm2),were chosen to research the effect of long term fertilization on nitrogen agronomy efficiency,annual nitrogen use efficiency and accumulated nitrogen use efficiency of maize.[Results]All levels of manure treatments and NPK significantly have increased maize yield.The treatments of NPK combined with manures(M30 + NPK and M60 + NPK) have reduced the variation of maize yield(CV) and improved the sustainable index of maize yield(SYI).The nitrogen agronomy efficiency,annual nitrogen use efficiency and accumulated nitrogen use efficiency show increase trends with longtime chemical fertilization,and the increases reach significant or extremely significant levels.The soil fertility is improved with the applications of manures,but the variation of nitrogen agronomy efficiency,annual nitrogen use efficiency and accumulated nitrogen use efficiency are not significant,and the variation trend is significantly decreased with the elongation of experiment time.The nitrogen use efficiency is negatively correlated with soil organic carbon,soil total nitrogen,soil total phosphorus,and soil available potassium.[Conclusions]In black soil with relatively high fertility,the nitrogen use efficiency of maize is stable,but shows significantly declining trend,which provide scientific references for the partial replacement of chemical fertilizer by manure.
【Objectives】The objective of this study was to clarify the response to nitrogen levels in the eating quality and textural characteristic of different rice cultivars and the relationship between the tasty and texture related indexes.【Methods 】 A field experiment was carried out with two japonica softer rice varieties. Four nitrogen application levels were designed: 0,150,225,and 300 kg / ha,and the eating qualities and mouthfeel of japonica softer rice were measured and their relationships with each other were calculated. 【Results】1) With the increment of nitrogen input levels,the aroma,gloss,taste,mouthfeel and comprehensive indices were decreased but theintegrity increased,the CV% of eating indexes was in order of mouthfeel gloss taste value taste aroma integrity; indicating that nitrogen levels affect mouthfeel and gloss more than aroma and integrity of rice. 2) With the increment of nitrogen levels,the hardness,cohesiveness,chewiness and resilience were increased at first and then decreased,the maximum value appeared at 225 kg / ha treatment; the adhesiveness of rice exhibited opposite trend,the minimum value appeared at 225 kg / ha treatment,springiness was not influenced by nitrogen fertilizer.The CV% of rice textural properties was in order of chewiness hardness resilience adhesiveness cohesiveness,indicating that nitrogen levels affect the chewiness and hardness more than cohesiveness. 3) The values of aroma,gloss,taste,mouthfeel and comprehensive indexes of cultivar Nanjing9108 was higher than those of Nanjing5055,but the integrity was opposite. The coefficient of variation of taste indexes of Nanjing9108 were higher than Nanjing5055,indicating the better eating qualities of Nanjing 9108 than Nanjing5055. Nanjing 9108 was more sensitive to nitrogen fertilizer than Nanjing5055. 4) The values of hardness,adhesiveness,springiness,cohesiveness of Nanjing 9108 were lower than those of Nanjing5055,but the adhesiveness was opposite. 5) The aroma was positively correlated with aroma,gloss,taste and mouthfeel,negatively with integrity; hardness was significantly negatively correlated with cohesiveness and chewiness; resilience was negatively correlated with adhesiveness and springiness. 【Conclusions】Nitrogen levels significantly impacted the eating quality and textural properties of japonica soft rice. Nanjing 9108 was more sensitive to nitrogen fertilizer than Nanjing5055,N fertilization decreased the taste,aroma,mouthfeel,but increased the integrity of the selected two rice cultivars.When the N application levels were lower than 225 kg / ha,the N fertilization increased the chewiness,hardness,resilience and adhesiveness of the rice. Therefore,N application levels should be considered carefully for keeping the good tasty quality of japonica softer rice.
【Objectives 】 Fertigation technology has a great potential to replace the traditional irrigation and fertilization methods in the protected cultivation in China. Soils,climate,and crops require different frequency of irrigation and fertilization. Therefore,effects of different water and nutrient treatments on soil moisture,nutrient uptake,yield and quality of autumn- winter tomato in Guanzhong Plain,Shaanxi was studied. Our aim was to setup the optimum rates of irrigation and fertilization in solar greenhouses. 【Methods】The field trial included three treatments,the conventional treatment( CK) in which irrigation rate equaled to 100% evapotranspiration and average rates of fertilizers used by local farmers were applied( conventional fertilizer treatment),and reducing 20%and 40% of water and fertilizer rates in comparison with CK( S1 and S2). The fertilizers were added into the irrigation system with Venturi tube during the crop growth. Soil moisture in 0- 20 cm and 20- 50 cm layers was continuously monitored by an automatic tension meter system( Skye Data Hog2,UK). Soil water content was calculated with soil water characteristic curve. water surface evaporation was determined with the evaporating dish method( diameter 20 cm),and its relationship with loss of soil available water was analyzed. The nutrient absorption,yield, quality, irrigation utilization of autumn- winter tomato in different treatments were also determined. 【Results】1) The soil relative water contents are higher 75% in 0- 50 cm soil layer in all the treatments throughout the whole growing period of tomato,indicating soil water supply is adequate for tomato growth. The soil water contents in 0-20 cm and 20-50 cm soil layers in the conventional treatment reach or exceed the field capacity after irrigation,which indicates that water infiltrated below 50 cm soil layer and would result in nutrient leaching. Compared with CK,the soil relative water contents in the treatment of reducing 40% of water and fertilizer rates are mainly in optimum range from 75% to 85%. 3) When reducing the irrigation rate,the water loss from 0-50 cm soil layer is decreased,and the loss of effective storage water equals 65. 4% of the canopy water evaporation,and also equals to the irrigation amount in the S2 treatment. 3) There are not significant differences in nutrient absorption,yield and quality of tomato among the different treatments. However,the use efficiency of irrigation water is increased from 55. 1 kg / m3 in the conventional treatment to 83. 2 kg / m3 in the water and nutrient saving treatments. 【Conclusions】The optimum irrigation rate for the solar greenhouse in the study region is 65%of water surface evaporation. The appropriate irrigation quota for the autumn- winter tomato in solar greenhouse is1057 m3/ ha,the irrigation amounts in August,September,October,November and December are 168,169,132,105,and 50 m3/ ha,respectively,and the time intervals of irrigation in August,September,October,and November are 20-30 days,8-13 days,8-13 days,and 20-30 days,respectively and the irrigation in December is dependent on climate,either less rate or no irrigation. No irrigation is needed in January.
【Objectives】Stable isotope13 C and15N tracer technology was used to study effects of different fruit load on characteristics of distribution and utilization of13 C and15N of apple. Based on the nutrient absorption,theory of the effects of fruit load on growth and development of apple was illustrated to provide evidence for fruit thinning and increasing N fertilizer utilization. 【Methods 】The materials were 5- year-old apple tree( Wanglin / SH38/ Malus robusta Rehd.),and the fertilizer was applied on March 27,2013. The method was annular groove fertilization:15N-urea 10 g,N 110. 33 g,P2O5143. 15 g and K2 O 151. 26 g each plant. After the fruiting,the fruits were thinned: control,2 /3 fruit load and 1 /3 fruit load. The trees were labeled with13 C at the fruit maturity( September6). 72 hours after labeled,the trees were sampled to determine13 C and15N abundance.13 C abundance was determined by DELTA V Advantage isotope ratio mass spectrometer,15 N abundance was determined by ZHT- 03 mass spectrograph. 【Results】Compared with the control,the average single fruit weights of the 2 /3 fruit load and1 /3 fruit load are increased by 17. 68% and 48. 57% respectively,root-shoot ratios are increased by 7. 69% and15. 38% respectively,however,the average yields per plant are significantly decreased to 50. 18% and 78. 60% of control,respectively. The unit area average dry yields of the three treatments are significantly different,0. 83 kg / cm2,0. 54 kg /cm2 and 0. 33 kg / cm2,respectively. When the fruit load increases,more13C- assimilate transports to fruit and results in the decrease of the13C- assimilation in roots. The13 C partitioning rates in fruits of the three treatments( control,2 /3 fruit load and 1 /3 fruit load) are 39. 81%,29. 25% and 16. 46%,and the rates of roots are 16. 79%,19. 98% and 24. 64%. The15 N use efficiencies of the three treatments are 8. 51%,10. 11%and 13. 23%. The Ndff values of the three treatments are consistent,and in order: fruit biennial root leaves branch of perennial trunk. With fruit load increasing,the Ndff values of the fruits are increased,and the values of the control is 2. 76%,which is 1. 17 and 1. 31 times of that of the 2 /3 fruit load and 1 /3 fruit load,respectively. The15 N partitioning rate is consistent with that of13 C,and when the15 N partitioning rates are high,the13 C partitioning rates are also high in organ. 【Conclusions】With fruit load increasing,more13C- assimilate is transported to fruits and results in the decrease of the13C- assimilate in roots,and the15 N utilization is decreased.It is good for apple production that the unit area average dry yield is 0. 54 kg / cm2.
【Objectives 】 The accumulation of calcium carbonate and higher p H in calcareous soil restrict the absorption of zinc( Zn) in wheat in northern China. However,because of highly exchangeable Ca contents in the calcareous soil,the research on crop calcium and zinc nutrition as well as their interaction usually was overlookedin this area. Therefore,a pot trial was carried out to investigate the effects of Ca Cl2 on winter wheat growth,the uptake and utilization of Ca and Zn,and to explore the interaction between Ca and Zn in winter wheat. 【Methods】The collected calcareous soil of 0- 20 cm layer topsoil at the Experimental Station One at Northwest AF University was used to cultivate winter wheat. The experiment with five treatments was designed by a randomized complete block design by four replications. The treatments included five Ca rates of 0,0. 3,0. 6,0. 9 and 1. 2 g / kg soil,based on the application of nitrogen,phosphorus and potassium at N 0. 3 g / kg,P2O50. 2 g / kg and K2 O 0. 3 g / kg,respectively. A widely used local winter wheat cultivar of Xiaoyan 22 was used,and sowed on October 15 in 2010,and as basal application,all the fertilizers were completely mixed with the soil before sowing. Plant samples were collected at maturity stage to determine the dry weights of straw,glumes and grain of winter wheat,concentrations of calcium and zinc in these different tissues or organs, soil p H, soil exchangeable Ca and available Zn concentrations,and the uptake and harvest index of Ca and Zn by plants were evaluated. Data analysis was performed using Excel software,and analysis of variance was performed by DPS software. 【Results】Data showed that grain yield and aboveground biomass of winter wheat increased with the application of Ca Cl2. The aboveground biomass in the treatments with supply of Ca 0. 6,0. 9 and 1. 2 g / kg significantly increased by 9. 8% to 17. 5%,and the grain yield in the treatments with supply of Ca 0. 9 and 1. 2 g / kg respectively increased by 10. 7% and22. 7% relative to the control. Application of Ca Cl2 significantly increased Ca concentration by 53% and 68% in wheat straw,respectively,when application rates were Ca 0. 9 and 1. 2 g / kg,and by 34%,36% and 51% in glume,respectively when the rates of Ca 0. 6,0. 9 and 1. 2 g / kg were supplied compared to the control treatment.However,the Ca concentration in grain was not significantly changed. Total uptake of Ca increased significantly by38. 6% to 91. 4% because of the increase in Ca Cl2 application rates. The concentration of Zn in grains was significantly increased from 33. 7 mg / kg in control to 42. 0 and 41. 6 mg / kg in the treatment with supply of Ca 0. 9and 1. 2 g / kg,respectively. Total Zn uptake was also found to be significantly increased with an increase in Ca Cl2 application rates,and was 47. 0% higher in the treatment with supply of Ca 1. 2 g / kg than that in the control.Application of Ca Cl2 showed no obvious effects on the exchangeable Ca and available Zn in the soil at harvest stage,but the soil p H respectively decreased from 8. 16 to 7. 93 and 7. 97 in the treatments with supply of Ca 0. 9 and 1. 2g / kg compared to the control treatment. 【Conclusions 】 Appropriate application of Ca Cl2 in calcareous soil significantly increased the aboveground biomass and grain yield of winter wheat under pot experimental condition.Total Ca uptake significantly increased with the increase of Ca Cl2 rates,whereas,the Ca concentration in grains was not affected. Application of Ca Cl2 significantly decreased the soil p H at harvest stage,and simultaneously promoted Zn uptake and transportation in winter wheat,indicating that this study provides an useful information for the understanding on the mechanism of zinc activation and exploration in promoting the absorption and utilization of Zn by crops under calcareous soil condition.
【Objectives】The experimental objective is to investigate the differences in N uptake and utilization in the machine- transplanted rice genotypes and explore an effective pathway improving uptake and utilization of N in the machine- transplanted rice genotypes. 【Methods】A field experiment was designed in randomized blocks to determine the N content,yields,the characteristics of N accumulation and dry matter weight,distribution and translocation of N in the different machine- transplanted rice genotypes at the growth stages of three medium-maturing varieties,three late- maturing varieties and four japonica rice cultivars,and explain the reasons causing the differences in the characteristics mentioned above. 【Results 】1) The accumulation dynamics of N in themachine- transplanted rice was exhibited by a logistic curve. 2) N content in the machine- transplanted rice decreased through the growth period. The content of N in japonica rice cultivars was higher than in indica hybrid rice cultivars during jointing- heading,then that was gradually decreased and became lower than in indica hybrid rice cultivars at maturity. The content of N in medium- maturing indica hybrid rice cultivars reached the highest value at maturity stage. 3) The ultimate N uptake in the japonica rice cultivars was 23. 0% lower than in medium- maturing indica hybrid rice cultivars,and 33. 1% lower than in late- maturing indica hybrid rice cultivars. 4)Medium- maturing indica hybrid rice cultivars exhibited the highest N accumulation during heading- maturity,and a highly N distribution ratio in the panicle,highly apparent N translocation rate in the leaf and stem- shead with a higher N grain production efficiency and N translocation efficiency,indicating that the accumulation and translocation efficiency of N in the medium- maturing indica hybrid rice cultivars were significantly higher than those in the late-maturing indica hybrid rice cultivars and japonica rice cultivars under the planting mechanization. Fyou498 from medium- maturing indica hybrid rice showed much higher N uptake than the others,and had an advantage of rapid N accumulation at the early growth stage and reasonable N distribution at the late growth stage. 5) Late- maturing indica hybrid rice cultivars demonstrated the biggest enhancement rate in N accumulation from 84 to 91 d,and a steady N accumulation during the whole growth period,and the highest N uptake,but which was not beneficial to yield formation. 6) Cultivar 69you8 has higher N uptakes and yield than the other japonica rice cultivars,and its N accumulation and translocation efficiency was significantly higher under the planting mechanization.【Conclusions】Different genotypes are significantly different in the characteristics of N accumulation and translocation under machine- transplanting condition. The accumulation and translocation efficiency of N in the medium- maturing indica hybrid rice cultivars is significantly higher than those in the late- maturing indica hybrid rice cultivars and japonica rice cultivars. Fyou498,a medium- maturing indica hybrid rice cultivar,demonstrates genetic advantages in the N accumulation,distribution and yield formation. Late- maturing indica hybrid rice cultivars have potential in high N accumulation,which,however,does not show good to yield formation. N accumulation in the japonica rice cultivars is relatively low. Among the japonica rice cultivars,69you8 has significantly higher N accumulation and yield under the planting mechanization,showing better suitability for planting mechanization.
[Objectives] Fertilization is one of the main approaches to increase crop yields and soil fertility . Assessment on the sustainability of farmland under long-term different fertilization modes will supply theoretical and practical supports for rational and sustainable fertilization in areas of Earth-Orthic Anthrosols .[Methods]Based ona long-term experiment of "National Monitoring Base of Soil Fertility and Fertilizer Efficiency on Loess Soil " in Yangling City, Shaanxi Province, samples were collected from the 9 treatment plots (CK, N, NK, PK, NP, NPK, SNPK, M1NPK and M2NPK), and totally 22 parameters were analyzed for the calculation of soil nutrient index (NI), microbial index (MI), crop index (CI) and sustainability index (SI), which were used to comprehensively assess the sustainability of the soil-crop system under different fertilization modes .[Results]1 ) The soil NI values in both the CK and N treatments were respective 0.75 and 0.87, lower than the threshold (1.00), and there was significant different between them ( P <0.05 ) .While those in other treatments were in range of 1.12-3.12 , higher than the threshold .The differences between NP and NK and between SNPK and PK were not significant , but significant among other treatments ( P<0.05 ) .2 ) The soil MI values in chemical fertilizer treatments ( CK, N, NK and PK) were all lower than the threshold (1.00) in range of 0.74-0.84 .The differences between NP and NK and between SNPK and PK were not significant , whereas significant between these two groups ( P<0.05 ) . The MI values in treatments containing NP ( NP, NPK, SNPK, M1 NPK and M2 NPK ) were in range of 0.98-1.21 , all close to or higher than the threshold 1.00 .The difference was not significant between M 1 NPK and M2NPK, nor between NP, NPK and SNPK, but significant between these 2 groups (P<0.05).3) The CI values in CK, N, NK and PK were in range of 0.52-0.60 , all lower than the threshold 1.00.Significant difference was only between N and PK ( P <0.05 ) .The CI values in treatments containing NP were in range of 0.98-1.02 , all close to or higher than the threshold , and there were not significant differences among them .4 ) The SI values in CK, N, NK and PK were 0.49, 0.54, 0.74 and 0.99 respectively, all lower than the threshold (1.30).The SI values in NP and NPK were respective 1.18 and 1.26 , close to the threshold , and there was no significant difference between the two treatments .The SI values in the combination treatments of chemical and organic fertilizers (SNPK, M1NPK and M2NPK) were respectively 1.55, 2.32 and 2.94, and were 19.5%, 78.8%and 126.3%higher than the threshold , and significantly different among them ( P<0.05 ) .5 ) The variability was 50.2%, 29.1%and 18.4%in NI, CI and MI.The variability SI, computed by NI, CI and MI, was 62.1%.[Conclusions] In winter wheat-summer maize rotation system , the soil fertility is unsustainable under long-term no fertilization or partial fertilization patterns , basically sustainable under balanced chemical fertilization ( NP and NPK) patterns, and the most sustainable under the chemical NPK fertilizer and straw return (SNPK), or manure (M1NPK) combination in areas of Eum-Orthic Anthrosols.
[Objectives] Conservation tillage is widely used in dry farmlands of northern China in recent years .A long term field experiment (2003-2013 ) was conducted to explore impact of the conservation tillage on soil organic carbon ( SOC) , spring maize yield and water utilization .We demonstrated the cause of yield improvement in the conservation tillage further , and then provided theoretical and technical support for dry farmland tillage .[Methods] There were three treatments, conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Annual variations of SOC (0-20 cm and 20-40 cm), soil moisture at 20 cm depth, crop water consumption, maize yield and water use efficiency were analyzed , and effect of the three tillage methods on above factors was also analyzed .Correlation analysis between maize yield and above factors was done in our study .[Results] 1 ) The conservation tillage can improve soil organic carbon (SOC) content, the annual SOC (0-20 cm) contents of the RT and NT treatments were increased by 11.2%and 3.4%compared with CT respectively , and the SOC (20-40 cm) of the RT and NT treatment were increased 5.53 and 3.29 g/kg.The increased rates of 0-20cm SOC stock of RT and NT were C 0.365 and 0.754 t/(hm2· a) respectively.2) The conservation tillage significantly increased crop yields:the average annual yields of 2003-2013 of the RT and NT treatments were 5.83 t/hm2 and 5.39 t/hm2 respectively, which are 14.7%and 6.1%higher than that of CT.3) The maize yield under the tillage had significant quadratic relationship with the soil 0-20 cm layer water content , and had significant power equation relationship with crop water consumption .4 ) The conservation tillage can increase soil moisture , reduce water consumption during maize growth and improve water use efficiency ( WUE ): compared with the CT and RT , NT increased the average moisture contents of 2003-2013 by 1.90 and 1.66 percentage points , whereas decreased annual water consumption by 16.1 mm and 7.6 mm;compared with CT , RT and NT increased WUEs by 16.1%and 10.2%, and precipitation use efficiencies ( PUE ) by 13.9% and 5.8% respectively .[Conclusions] The long-term conservation tillage can improve SOC and soil water content and decrease useless water consumption effectively, thus improve yield and water use efficiency .RT has the best performance , followed by NT.In general, promotion of conservation tillage is an effective way for increasing yield and water conservation in dry farmlands .
【Objectives】The drought in spring and low fertilizer utilization efficiency limit the high quality apple production in the Loess Plateau in northwest region of China. Fertigation is usually used in abroad to overcome the problem of low fertilizer utilization efficiency. But this technology is difficult to spread in China for its strict requirements of irrigation system and investment at the level of farmer household in the short run. In recent years,fertilization with injection to the rhizosphere is used broadly in many places of China. This technology needs low cost and is simple.15 N urea was used in this experiment as tracer to study the effects of fertilization with injection to the rhizosphere on nitrogen absorption and utilization,fruit yield and quality of apple in the Loess Plateau.【Methods】The 9- year- old Fuji trees[Malus pumila Mill cv. Red Fuji/M26 /Malus Sieversii( Ledeb) Roem]and15N tracer element which was measured by MAT- 251 mass spectrometer were used to calculate the fertilizer utilization efficiency of various tree organs and soil. SPAD-502 was used to determine the SPAD value of marked leaves. Sponge soaked in a solution of glycerol phosphate was used to measure the amount of field soil ammonia volatilization. Static chambers- gas chromatography was used to determine the soil N2 O fluxes. These methods were used to explore the effect of fertilization either with injection or traditional ring ditch on nitrogen absorption,distribution and utilization,fruit yield and quality of apple in the Loess Plateau.【Results】The results show that the advantages of apple orchard fertilization with injection to the rhizosphere in the Loess Plateau are as follows: 1)Within one month after fertilization,the gaseous nitrogen loss in apple orchard changed. The amount of soil ammonia volatilization of fertilization with injection to the rhizosphere was significantly less than the traditional ring ditch fertilization by 54. 9%,and the N2 O flux was 5. 0%. 2) After fertilization with injection to the rhizosphere,the distribution range of water and fertilizer increased at the same time,the volume of fertilizer absorbed by apple tree roots was expanded eventually,the percentage nitrogen derived from fertilizer( Ndff%) of new shoot leaves and fruits was always at a high level throughout the whole growing season. After the fruits were harvested,the absorption rate of the whole tree was 53. 04%,and 12. 25 percentage points higher than the control. This result indicated nitrogen was absorbed more quickly following fertilization with injection to the rhizosphere,and nitrogen utilization efficiency was significantly improved. 3) In the end of growth season,the 0-60 cm soil nitrogen residual rates of treatment of fertilization with injection and the control were 36. 55% and 43. 13%,respectively. And the former was significantly lower than the latter. 4) The chlorophyll content( SPAD value) of new shoot leaves was maintained in higher level than the treatment of traditional ring ditch fertilization in the whole growing season.Compared with traditional ring ditch fertilization,fruit weight and yield of per tree in treatment of fertilization with injection were higher than the control by 3. 8% and 19. 7%,respectively. 【Conclusions 】 The technology of fertilization with injection in the Loess Plateau region can increase tree nitrogen absorption,utilization and decrease soil nitrogen residual significantly. So the water and fertilizer distributed evenly in soil and the purpose to save water and fertilizer can be achieved eventually. Fertilization with injection also avoided the root damage caused by traditional digging and reduced labor costs at the same time. On the whole,fertilization with injection is an effective way to improve the fertilizer and water use efficiency in dryland apple production in the Loess Plateau.
[Objectives] Nitrogen use efficiency ( NUE) or apparent NUE ( ANUE) is the percentage of applied N uptaken by one season crop , which does not consider the N residue in soil .Long-term ferlilization experiment is able to reflect the variation of soil N storage .In this article , we analyzed the ANUE and real NUE ( RNUE ) in different fertilization trentments using long-term experiments to calculate real contribution and real loss of N fertilizer in agricultural production .[Methods] Four long-term experiments ( 31 years ) were chosen in this study , aqni-cinnamon soil in Beijing and fluvo-aquic soil in Kaifeng with cropping system of wheat-corn rotation , and purplish soil in Sichuan and yellow-brown soil in Hubei with cropping system of rice-wheat rotation .Crop and soil samples were collected from the treatments of no fertilizer (CK), chemical N(N), chemical N, P and K fertilizers(NPK), and NPK comlined with manure ( NPKM) .The aurnual N uptake by crop , soil total N content were analyzed , and the ANUE and RNUE were calculated .[Results] The average RNUEs are 47.6%, 56.6%, 57.0%and 56.3%in aqui-cinnamon soil , fluvo-aquic soil , purplish soil and yellow-brown soil under the three fertilization , respectively , which are significantly higher than ANUE ( 33.6%, 42.1%, 37.8% and 25.8%) .RNUEs in purplish soil and yellow-brown soil are 18.6%-32.9% higher, and in aqui-cinnamon soil and fluvo-aquic soil 10.9%-17.5% higher than ANUEs , indicating that the traditional NUE is underestimated at a higher extent in upland-paddy soil than in upland soil .The ANUE and RNUE are increased annually at rates of 1.76%-2.49%and 1.50%-2.29%, respectively, in upland soils, under the NPK applied treatments ( NPK and NPKM), attributed to the N 17.5-37.3 mg/( kg· a) increase of soil total N content , significant increases are observed at RNUE but not at ANUE during the fertilization period in yellow-brown soil , indicating that of the NPK and NPKM treatments could improve the N accumulation in soil with a higher extent in upland-paddy soils than in upland soils .[Conclusions] NUE is generally underestimated about 20%in China , especially in the paddy-upland rotation with a high change of soil total N .
[Objectives] The paddy rice system shows a great stability to climate and soil basic fertility which makes a great contribution to rice yield , so soil basic fertility represents a key contributor for high and stable rice yield.Therefore, investigating changing trends of paddy soil basic fertility in different regions under long -term fertilization can provide scientific basis not only for sustainable rice production but also for assessing and proposing proper fertilization strategy .[Methods] An experiment was designed to include two treatments , CK ( no fertilizer ) and NPK ( conventional fertilization ) .The rice yield under the CK represents soil basic fertility , and the proportion of the crop yield under the CK to that under the NPK represents soil basic fertility contribution .Seven long-term field experiments in paddy crop systems ( rice-rice , and rice-wheat rotation ) were selected to investigate dynamic trends in soil basic fertility and its contribution , and to examine relationships between soil basic fertility contribution and rice yield or other indicators .[Results] In general , the rice yields under CK remain constant with a mean change rate of-0.3 kg/( hm2 · a) only.Soil basic fertility trends show differences among paddy soil types , and soil basic fertility levels show a declining trend for reddish paddy soils and remain constant for purple paddy soils . Under CK, both the late-rice and single-rice yields show increasing trends with rates of 1.6 and 29.2 kg/(hm2· a), respectively, while the early-rice yields shows a declining trend with a rate of 20.0 kg/( hm2 · a).The declining rates of rice yields in the CK treatment are highest at Baisha (BS) and Wangcheng (WangC) sites, up to 47-82 kg/(hm2· a).Those of early-rice at Nanchang (NC) site and single-rice at the Wuchang (WuC) and Suining (SN) sites show increasing trends with the rates of 44-81 kg/(hm2· a).On average, the rice soil basic fertility contribution ranges from 42% to 68%, with a mean value of 59.7%.The contribution percentages are 55.1%, 67.1% and 54.9% for early-rice, late-rice and single-rice, respectively. Soil basic fertility is significantly positively correlated with sustainable yield index (SYI) in the CK treatment (r=0.655, n=13).The mean annual rice yield is 5100 kg/hm2 under the NPK treatment , which is significantly higher than that under the CK treatment (2911 kg/hm2 ) in the seven sites.The contribution of the NPK fertilization to rice yield is 40.3%.[Conclusions] Under no fertilizer , the yields show stable or increasing trends for late-rice and single-rice, but show a declining trend for early-rice especially in red paddy soils .The rice yields are most stable for the purple paddy soils.Under the fertilization, the rice yields are stable across all the sites.From a long-term view, increasing soil basic fertility can be effective in elevating rice yield sustainability .
【Objectives】Scab has become one of the major diseases affecting yield and quality of wheat. An experiment was set up to study effect of nitrogen fertilization on scab and to explore relations between nitrogen fertilizer and soil nitrogen,plant nitrogen concentration and scab under different nitrogen levels. 【Methods】A field experiment was conducted using 5 nitrogen rates( N 0,120,180,240 and 360 kg / ha) and a multi- spike cultivar Yu Mai49- 198( YM49- 198) and a large spike cultivar Zhou Mai16( ZM16) in randomized blocked,and scab was investigated by wheat scab forecasting technical specifications. 【Results】The soil nitrate nitrogen contents and accumulation amounts in 0- 90 cm soil layer are increased with the increase of N application rate. There are no significant differences in soil nitrate nitrogen contents at 0- 30 cm and the accumulation amounts in 0- 90 cm soil layer under N0,N120 and N180,and the contents and amounts aresignificantly lower than those under N240 and N360at the maturity. The morbidities and disease index( DI) of scab are increased with the increase of N application rate,and there are significantly differences among different treatments. The morbidities and DIs of YM49- 198 under the N treatments are higher than those under the N0 treatment by 29. 5%-132. 0% and 35. 9%-225. 2%,respectively,and those of ZM16 are 42. 4%-161. 8% and41. 7%-206. 9%. The morbidities and DIs of the two cultivars under N0,N120 and N180are not significant different,and are significantly lower than those under N240 and N360. However,the disease of ZM16 is more serious since the morbidities and DIs are higher than those of YM49-198 by 7%-25% and 28. 0%-63. 6%,respectively.The scab morbidity and DI are positively correlated with soil nitrate content,and linearly correlated with nitrate-nitrogen accumulation in 0-90 cm. The stem sap nitrate concentrations at the booting,anthesis and filling stages,the total nitrogen contents at the jointing and anthesis stages have significant differences among the treatments,and are significantly and positively linear correlated with the scab morbidity and DI. 【Conclusions】The soil nitrate nitrogen contents and accumulation amounts are increased with the increase of the N application rate. The soil residual nitrate is lower under conditions of nitrogen rate less than 180 kg / ha,and thus,the scab disease is lighter.The morbidity and DI of scab are increased with the N application rate,which illustrates that higher nitrogen fertilizer will aggravate scab disease at the jointing and anthesis stages. Therefore,to reducing the scab disease,appropriate nitrogen rate,soil nitrate and plant nitrogen concentration are needed during this period.Considering the residual nitrate in soil,the yield and scab,the appropriate nitrogen amount is N 180 kg / ha.
【Objectives】Nitrogen( N) and sulphur( S) are essential nutrients required for all living organism,which play important role in grain yield and quality of wheat. Insufficient S,especially physiological deficiency S caused by large amounts of N supply,will result in decreased grain yield and diminished S amino acid content of the grain protein. This paper aims to compare the effects of different N and S combined application on the N use efficiency and grain yield of winter wheat and to give some reasonable advices about N and S fertilization technology in the North China Plain. 【Methods 】 A wheat cultivar,Yumai 49-198,was used as test material. Field experiments were conducted with five N levels of 0,120,180,240 and 360 kg / ha( recorded as N0,N120,N180,N240,N360) and two S levels of 0 and 60 kg /ha( S0,S60) during wheat growth seasons. The dry matter accumulation( DMA),N accumulation and distribution,and grain yield formation were measured in 2012-2013 at Wenxian County in Henan Province,China. 【Results 】 The DMA at late growth stages is increased with the increase of N application rate. Under the same N application rates,S application could significantly increase DMA of winter wheat compared with no S application,in which at maturity stage the DMA of N180S60,N240S60 and N360S60compared with N180S0,N240S0 and N360S0increased 2225,3607 and 3120 kg / ha,respectively,showing the order of N180S60 N240S0,N240S60 N360S0,and the differences all reach significant level. The total N accumulation in wheat plant also increased with the increase of N application rate,the S application could significantly increase the accumulation under higher N application rates( 240 and 360 kg / ha). Compared with no S application,S application at five N application levels could also increase the grain yield by 10. 5%,18. 3%,5. 2%,5. 6% and4. 9%,respectively. N partial factor productivity gradually declined with the increase of N application rates,N recovery efficiency,agronomic efficiency and physiological efficiency are all the highest in the N180 treatment,and combined with S application could further significantly increase the N recovery efficiencies,and the increases in agronomic efficiency and N partial factor productivity are significant at N application rates of 120,180 and 240 kg / ha. 【Conclusions 】Comprehensively considering grain yield and N use efficiency in the current wheat production of North China,we conclude that combined N and S fertilization is effective technology for achieving simultaneously high grain yield and N use efficiency of winter wheat. N of 180-240 kg / ha combined with S of 60 kg / ha are recommended to obtain stable and high yield and high efficiency of winter wheat in the tested area.
The land reserves which can be potentially opened for farming purpose are extremely limited in China,the amelioration of farmlands with low productivity plays all important roles in the grain production increment. Low- yield rice paddy soils constitute high proportion in the total low fertility soils,many studies have been carried out to investigate their fertility characteristics and effective technologies for their improvements. However, these researches are scattered,lack of systematic integration,have not formed strategic management rules. Therefore,the types of low yield rice paddy soils, the novel technologies and approaches are reviewed, and the possible technological breakthrough is proposed. According to the data from the Ministry of Agriculture of the Peoples 'Republic of China,there are about 7. 67 × 107 ha low- yield rice paddy soil nationwide,which can be divided into four major groups: cold- gleyed paddy soil,bonded paddy soil,harden paddy soil and contaminated paddy soil,according to their intrinsic constraints or detrimental condition. The soil quality assessment was crucial for chosingsuitable improving method of low- yield rice paddy soil. Four approaches were commonly used to evaluate soil quality: dynamics method,integrated scoring method,multiple- variable indicator kring( MVIK) method,and relative quality method. Basically,the soil quality assessments are based on the employment of GIS and the soil biological properties. Through the use of new technologies including isotope probing,fourier transform infrared spectoroscopy( FTIR) and CPMS13C- NMR spectra,the analyses of soil organic C distribution in micro-aggregate,humus transformation and their binding mechanism with soil minerals have been deep into micro- level.Meanwhile,the application of new analytic methods such as high- throughput sequencing,soil macro genomics and macro transcriptome also made the relative researches to molecular level. Rrecommended fertilization based on yield response and agronomy efficiency will continually to be the core of nutrient management of paddy fields for exploring the yield increase potentials. For the assessment of soil quality,specific researches are still needed for individual limiting factors in different low- yield paddy soils. The criteria of soil biological properties are also need to be strengthened in the assessment of soil quality. For the amelioration of the low- yield paddy soils,studies related to the forming mechanism of soil barrier and the corresponding amendment ways still need to be carried out. The reformation of other types of low- yield paddy soils including new- reclaimed, salinized, calcified and contaminated paddy fields are also need concerning. The effects of long- term amendments on soil humus structure,enzymes,microbial diversity and functional gene in aggregate level are always need to be traced.Technologies including crop residue incorporation,recommended fertilization,selectivity of resistant cultivars and mass control deserve focused in agricultural management of low- yield rice paddy soil.
【Objectives】The cultivation areas and yields of Fuji apples in west Liaoning Province account for a larger proportion of the total apple production in Liaoning Province. The fertilizer managements are deficient in scientific base. The Compositional Nutrient Diagnosis method( CND) is preliminary used for the study of the status of ‘Fuji'apple nutrition in west Liaoning Province,and provides a guide for the orchards fertilization management.【Methods】Eighty six representative apple orchards were selected,the yields,fruit qualities and contents of nitrogen( N) 、phosphorus( P) 、potassium( K) 、calcium( Ca) 、magnesium( Mg) 、iron( Fe) 、copper( Cu) 、manganese( Mn) 、zinc( Zn) were measured. The CND method was adopted for dividing the samples into high and low production level subpopulation,and bringing the low production level subpopulation nutrient diagnosis into force. The yield cutoff value of high production level subpopulation was confirmed by CND,and the procedures of fruit quality evaluation composite scores cutoff value were as follows: firstly,the six indexes of fruit quality were normalized; secondly,the principal component analysis was carried out on the six indexes,composite evaluation scores of six indexes were determined; thirdly,by the method of CND,fruit quality composite evaluation scores cutoff value was obtained. Orchards which met with the CND and expert consultation method standards of yield and quality cutoff values at the same time were separated from the samples. CND norms were calculated according to the high level production subpopulation nutritional status. Based on which,leaf nutrient diagnosis was put into effect,and the condition of nutrient was present. 【Results】The leaf analysis with CND indicated that yield cutoff value of the high production level subpopulation was 44. 556 t / ha,the fruit quality evaluation composite scores cutoff value was 0. 792. There were 13 orchards which met the conditions,accounting for 15. 12% of the total orchards. The CND norms were VN*= 2. 776,VP*= 0. 212,VK*= 1. 884,VCa*= 2. 042,VMg*= 0. 814,VFe*=- 2. 470,VCu*=- 5. 090,VMn*=- 2. 631,VZn*=- 3. 867,VR*= 6. 330; SDN*= 0. 173,SDP*= 0. 144,SDK*= 0.155,SDCa*= 0. 266,SDMg*= 0. 307,SDFe*= 0. 189,SDCu*= 0. 474,SDMn*= 0. 467,SDZn*= 0. 325,SDR*= 0. 134; the low level production subpopulation fertilizer orders were Fe Mn P N Ca K Cu Zn Mg. 【Conclusions 】 The leaf analysis is established on the yield and fruit quality with CND. The investigation results obtained using the method show that in west Liaoning Province,the criteria for high yield is 38.451 t / ha,for good fruit quality is 0. 792. The number of orchards meet the two criteria is 13,only accounting for the 15. 12% of the total orchards. In ‘Fuji'apple of west Liaoning Province,Fe,Mn,P and N are in deficiency;soil available Fe and Mn contents are appropriate,soil N and P are deficient. Therefore,N and P fertilizers are recommended to be applied in small amount and several times,Fe and Mn could be foliar sprayed appropriately in the apple production of west Liaoning Province.
[Objectives] Based on principle of nutrient balanced method, parameters of balanced fertilization for winter wheat in cinnamon soil in Northern China were studied. A soil testing and fertilizer recommendation index system for winter wheat in cinnamon soil was established to guide fertilizer use and wheat production directly, quickly, scientifically and rationally in this region.[Methods]The parameters of balanced fertilization for winter wheat in cinnamon soil of Northern China were studied by field trials in multiple sites and years. The parameters as nutrient uptake per 100 kg grain, calibration coefficients of soil available nutrients and apparent recovery efficiency of applied fertilizer were calculated respectively in this study. The impact of soil environment factors and yield on the calibration coefficients of soil available nutrients and apparent recovery efficiency of applied fertilizer and their variation tendency was studied.[Results]The results indicate the nutrient uptakes per 100 kg grain of wheat for nitrogen(N), phosphorous(P2O5)and potassium(K2O)are 3, 1. 2 and 2. 8 kg respectively with small variation.The calibration coefficients of soil available nutrients relate significant negatively with soil available nutrients by power exponent. The apparent recovery efficiencies of the applied fertilizers have negative logarithmic relationship with soil available nutrients in different yield range. Based on the nutrient balanced method, a soil testing and fertilizer recommendation index system for winter wheat in cinnamon soil is established to guide fertilizer use and wheat production directly, quickly, scientifically and rationally in this region.[Conclusions]Based on the nutrient balanced model, the fertilizer rates are recommended by the differences between the fertilizer requirement amounts for a target yield and soil nutrient-supplying amounts. The key point for the fertilizer recommendation is how to accurately determine basic parameters as the calibration coefficients of soil available nutrients and apparent recovery efficiencies of the applied fertilizer, which can make model be popularized and applied widely. Finally, the soil testing and fertilizer recommendation index system with quantitative characteristics of N, P , and K for winter wheat in cinnamon soil of Northern China is established, which is based on the nutrient balanced method and the related soil testing.
[Objectives] Soil microbes play key functions in organic matter decomposition , nutrient cycling and regulation of plant growth . Investigating the effect of long-term chemical fertilizers application on microbial characteristics is critical for the improvement in rational fertilizer application , and provides theoretical understanding in sustainability of agricultural management .[Methods] The experiment was based on the long-term experiment in "National Monitoring Base of Soil Fertility and Fertilizer Efficiency on Loess Soil" in Yangling City , Shaanxi Province .Six treatments were chosen , including no fertilization control ( CK ) , nitrogen fertilizer only ( N) , nitrogen and potassium fertilizer ( NK) , phosphorous and potassium fertilizer ( PK) , nitrogen and phosphorous fertilizer(NP), and nitrogen, phosphorous and potassium fertilizer (NPK).Biolog Eco-plate was applied to test the effect of long-term chemical fertilization on soil microbial characteristics .Moreover, soil microbial biomass and soil microbial community functional diversity were determined .[Results] Compared to the control ( CK ) , the soil microbial biomass C (SMBC) and soil microbial biomass N (SMBN) did not change in N treatment.However, the microbial quotient ( qMB ) and the N utilization ( SMBN/TN ) were reduced significantly under N treatment . SMBC, SMBN concentration and qMB were increased in NP and NPK treatments , where the shift in soil microbial community structure was also found .But N utilization was not increased in these treatments .In NK and PK treatments, SMBC, SMBN concentration and qMB were slightly increased , while soil microbial community structure did not show much difference .Biolog analysis showed that soil microbial activity was increased under the treatments including P ( PK, NP and NPK) .At the initial stage of incubation , the metabolism activity was greater under the treatments with P than those without P ( CK, N and NK ) .Nitrogen application alone did not affect microbial community functional diversity , while other fertilization treatments improved the ability of carbon source utilization as indicated by substrate richness , Shannon richness index , and dominant index ( Simpson index ) of soil microbial community with the increase greatest in NP and NPK treatments .The evenness index of soil microbial community was not affected by different chemical fertilizer applications .Principal component analysis showed that the ability for carbon substrates utilization varied with the greatest difference caused by the application of inorganic N and P fertilizers.[Conclusions] Balanced chemical fertilization ( NP and NPK) largely improves soil microbial diversity under winter wheat-summer maize rotation in the anthropogenic loess soil area .
【Objectives】Photosynthetic characteristics of winter wheat after flowering play an important role in dry matter accumulation and transportation,and soil moisture is the most important environmental factor which affects the crop photosynthesis. Application of no- tillage could improve the soil environment and increase the crop production. To study role of water reserving and soil moisture keeping under no- tillage with straw mulch practicein a long- term experiment,and transfer characteristics of canopy photosynthetically active radiation and their effects on photosynthetic characteristics and dry matter transportation of wheat,we conducted this experiment in the long- term plots. 【Methods】These plots were established in a silt loam soil in the Loess Plateau of China in1992,and consisted of no- tillage with straw mulch( NT) and conventional tillage( CT) with three replications.The soil of this semi- arid area is a Chromic Cambisol,which is low in organic matter and slightly alkaline and which is subject to frequent drying and wetting cycles. The soil moisture,and photosynthetically active radiation,flag leaf photosynthetic characteristics,dry matter accumulation and yield components of wheat were measured during the fallow period and wheat- growing period under different tillage practices. 【Results】During the fallow period and wheat- growing period,a significant increase of water- storage capacity under the NT practice is found in 0-160 cm soil depth compared with CT,with an average increase of 12%. At its lowest point( at the pre-filling stage),soil moisture under the NT practice is 21% higher than that of the CT practice( P 0. 01). The canopy photosynthetically active radiation intercepted under the NT practice is 163 μmol /( m2·s) higher than that of the CT practice at the heading and filling stages,which reaches the maximum difference( 19. 3%) at the pre-filling stage( P 0. 05),and both upper and bottom wheat canopies under the NT practice have opportunity to use light energy. Compared with the CT practice,the NT practice increases the stomatal conductance with an average of39% at the pre- filling stage,enhances the ability of carbon dioxide utilization by 11%,and improves WUE by22%. From the heading to mature stages,the net photosynthesis rate under the NT practice is 39% higher than that of CT,the grain weight and total plant weight at the harvest stage are 57% and 46% higher than those of CT respectively( P 0. 01),and the contribution of dry matter accumulation into grain after the flowering reaches64%. From the point of view of yield components,the NT practice had the significant effect on wheat spike number and thousand grain weights,31% and 10% higher than the CT practice respectively. The yield under the NT practice was 41% higher than the CT practice( P 0. 01). The study indicates that the ability of water reserving and soil moisture keeping under no- tillage with straw mulch practice could alleviate the decline of net photosynthesis rate in midday due to the action of water stress,and keep wheat photosynthesis at a high level.Meanwhile,the NT practice enhances the ability of dry matter accumulation after the anthesis,and the dry matter accumulation after the anthesis is the main source of dry matter accumulation into grain under the NT practice,while under the CT practice the dry matter accumulated in vegetative organs before the anthesis is the main source of dry matter accumulation into grain. 【Conclusions】The results indicate that the long- term no- tillage with straw mulch practice could significantly improve soil moisture and light interception ability, enhance wheat photosynthesis characteristics, WUE and dry matter accumulation and transportation, coordinate relationship between the yield components and increase wheat production in the dryland of the south of Shanxi Province.
【Objectives】In rice-wheat rotation,rice-rape rotation and other multi-cropping regions in China,large amounts of wheat or rape straw or other straws of rice fore-rotation crop were discarded or burned,which causedserious environmental pollution and resource waste. Hence,it has significant meaning to investigate a win-win mode between straw mulch and nitrogen( N) management. To explore the optimal straw mulch and N management mode,effects of the straw mulch and N management on root growth,N uptake and utilization and dry matter accumulation in main growth stages of hybrid rice( Fyou 498) were evaluated in this research. 【Methods】The experiment was conducted in the experimental field of Rice Research Institute of Sichuan Agricultural University in 2013. A splitplot design was used,with the main plots under wheat straw mulch( S1),rape straw mulch( S2) and no straw mulch( S0),N management as sub-plots combined with three N management practices under N 135 kg /ha rate in this study. Three N application ratios were applied on different splits: a) 3 splits: 50% basal,30% 7 d after transplanting( 7 DAT),and 20% panicle N-fertilizer according to different leaf ages at 4th leaves emerged from the top( N1),b) 3 splits: 30% basal,30% 7 DAT,40% panicle N-fertilizer at 4th leaves emerged from the top( N2),c) 4 splits: 30% basal,10% 7 DAT,60% panicle N-fertilizer equally at 4th and 2nd leaves emerged from the top( N3),in addition,no N application( N0) was set as control. Root growth,morphological characteristics,dry matter and N accumulation,dry matter transportation in stems and sheaths,and N utilization on 20 DAT and 30 DAT and at the filling stage and ripping stage were studied. At the same time,the correlation coefficients among root growth,N uptake and utilization,and grain yield were also analyzed in this research. 【Results】The results showed that the wheat straw mulch generally improves the dry matter accumulation and N uptake of rice,promotes the root growth and N utilization efficiency,and increases the grain yield significantly. The rape straw mulch could also increase the grain yield remarkably,but not as much as the wheat straw mulch. As for the N management practice,the N 30% basal,30% 7 DAT and 40% panicle N management practice( N2) is the optimal N-fertilizer management practice in all straw mulch treatments. The optimal N-fertilizer management practice regulates the root growth at the main growth stage efficiently,improves dry matter transportation in stems and sheaths,promotes the N utilization efficiency,and increases the grain yield significantly. When the panicle N-fertilizer ratio increases to60%,the root growth is poor,especially at the heading stage,the grain yield and N utilization decrease. The correlation coefficients among the root growth,N uptake and utilization and grain yield are as follows: under the straw mulch and N-fertilizer management,the root dry weight,total root volume and total root length generally have significant or extremely significant and positive correlations with the grain yield and N uptake and utilization at the main growing stage of rice( r = 0. 38*- 0. 78**). 【Conclusions】Compared with the no straw mulch treatment,the straw mulch could promote the root growth,N utilization efficiency,dry matter and nitrogen accumulation and grain yield,especially for the treatments with the wheat straw mulch. The combination of the straw mulch and 30%basal,30% 7 DAT and 40% panicle N management practice( N2) could regulate the root growth,promote N utilization efficiency,and increase the dry matter and N accumulation and grain yield more efficiently. Among all the treatments,the wheat straw mulch with 30% basal,30% 7 DAT and 40% panicle N management practice( N2) is the optimal mode in this research.
【Objectives】Zinc deficiency is very often happened in maize in saline fluvo- aquic soils in Hexi Oasis Area of Gansu Province,the high soil magnesium levels have been regarded as a major contributor to thisdeficiency. The inhibition effect of magnesium to zinc in saline fluvo- aquic soils in Hexi Oasis Area were discussed in this paper. 【Methods 】 A pot experiment was conducted with maize as materials. Exchangeable magnesium contents of 287. 3,349. 2,411. 6,487. 9 and 755. 2 mg / kg were obtained by irrigating different amount of Mg SO4 solution. The maize plants were harvested at 46 days,the biomass of above and under ground parts were dried and weighed,the Zn contents were measured. The second leaf under the interior leaf was used for the determination of active oxygen and some enzyme activities. 【Results 】1) More high and extremely high exchangeable Mg level in soil inhibits the growth of maize seedlings. When magnesia applied levels is 221 mg / kg,i. e. the exchangeable Mg content in soil is over 487. 9 mg / kg,the growth of maize is stressed,when the Mg2 +applied level is 515 mg / kg,i. e. the exchangeable Mg content in soil is over 755. 2 mg / kg,the plant height is markedly decreased by 14. 5%,showing symptoms of magnesia poison and zinc deficiency,such as withered leaf margins and partial white stripes on the leaves( P 0. 01). 2) With the increase of or exchangeable Mg levels,the dry weight in the of Mg2 +addition maize are reduced by 11. 9%- 38. 3% and 4. 6%- 11. 9% respectively. The reduction in stem weight is significantly higher than in roots. 3) Maize leaf chlorophyll contents are reduced by 9.4%-45. 9% with the increase of the Mg2 +addition. The Mg level of 515 mg / kg would lead to withered and yellow leaves. The blade superoxide dismutase( SOD),peroxidase( POD) and catalase( CAT) activities are increased at first and then reduced quickly,the peak value appears at the exchangeable Mg levels of 147,74 and 147 mg / kg respectively. When the dose reaches 515 mg / kg,the values are reduced by 49. 75%,48. 06% and 32. 21%respectively. The malondialdehyde( MDA) contents are increased consistently in the range of 20. 39%-183. 58%.4) The exchangeable Mg levels significantly inhibit the uptake of Zn. Compared with the CK,the zinc contents in above ground parts are reduced by 4. 05%- 57. 09%,the uptake reduced by 15. 41%- 73. 55%; the root zinc contents are reduced by 7. 55%-18. 99%,and the uptake reduced by 11. 62%- 37. 40%. The zinc content and absorption in stems / leaves are reduced more than in roots. High exchangeable Mg level would also lead to lower upward transfer of zinc. 5) Soil available zinc contents are significantly reduced with the increase of exchangeable Mg levels. When the Mg level reaches 515 mg / kg,i. e. the exchangeable Mg content in soil is over 755. 2 mg / kg,the available zinc content falls to 0. 47 mg / kg,which is below the critical value of zinc deficiency( DTPA- Zn 0.5 mg / kg).【Conclusions】Zinc deficiency of maize in saline fluvo- aquic soil in Hexi Oasis Area is closely related to soil magnesium content. The high levels of exchangeable Mg contents show significant restraining effects on the maize seedling growth and biomass,the leaf chlorophyll content and the activities of superoxide dismutase( SOD),peroxidase( POD) and catalase( CAT). Over high exchangeable Mg levels decrease the zinc absorption by maize seedlings,and the inhibition in stem / leaf is significantly higher than in root system,which inhibites the upward transfer of Zn from root to shoot. The available zinc content in soil will also be reduced,when the Mg level reaches515 mg / kg,the available zinc content is below the critical value of zinc deficiency.
