Legume-inclusive cropping is increasingly appreciated for enhancing crop yield and sustainability. However, their impacts on subsequent oilseed rape productivity under reduced nitrogen (N) inputs have not been well explored. In a five-year field rotation experiment, oilseed rape was cultivated with N fertilizer at zero (MN0), recommended (MN100), and 35 % reduction (MN65) following maize monoculture or preceding lablab (Lablab purpureus (L.) Sweet) intercropping in addition to MN65 (IN65). The productivity and stability of subsequent oilseed rape, and relevant indices of soil fertility and N cycling enzymes were investigated. Compared with the MN0 control, the MN100, MN65 and IN65 treatments increased the rapeseed yield by 0.7- to 1.2-fold. Compared with MN100, MN65 decreased rapeseed yield by 21 % and N uptake by 16 % on average across years. However, preceding lablab intercropping (IN65) recovered yield and N uptake. Treatment IN65 increased soil total N content by 7 % and organic matter by 10 % compared to the monoculture treatments, corresponding to 18-25 % increase in the soil quality index by preceding pulse intercropping. Moreover, in parallel with the increase in soil urease activity, the soil nitrate content in IN65 markedly increased by 18-123 % compared with that in the MN65 or MN100 treatments at most stages of oilseed crop growth. Principal component analysis revealed that the IN65 treatment was well distinguished from the three monoculture treatments, which was attributed primarily to soil nitrate, organic matter, nitrate reductase activity, and microbial biomass N. This enhanced N turnover and availability, in turn, largely contributed to N uptake and yield recovery of subsequent rapeseed crops under reduced N input. Consequently, the yield sustainability and stability of rapeseed following lablab intercropping were greater than those following monoculture, as evidenced by the higher sustainability index (64 % vs. 49 %) and lower variation (20 % vs. 32 %). Overall, these findings indicate that lablab and maize intercropping enhances positive legacies for subsequent rapeseed productivity under reduced N inputs.

【Objective】The aim of this study was to investigate the effects of nitrogen application on yield formation and nutrient utilization of oilseed (Brassica napus L.) under different cropping systems.【Method】A field experiment was carried out in Huanggang, Hubei Province. An oilseed variety ‘Zhongyouza19’ was used as the material, setting with two cropping systems (rice-oil rotation, RO; soybean-oil rotation, SO) and four nitrogen rates (N0, 0; N1, 90 kg·hm-2; N2, 180 kg·hm-2; N3, 270 kg·hm-2) in this study. The yield and its components, dry matter accumulation, agronomic traits, nitrogen content and seeds quality were measured.【Result】(1) The oilseed yield of SO was significantly higher than that of RO, and the pods per plant, seeds per pod and 1000-seeds weight of oilseed in different cropping systems all tended to increase significantly by increasing the amount of nitrogen. Compared with N0, the seed yield of RO increased by 176.68%, 436.49% and 835.40% under N1, N2 and N3 treatments, respectively, while that of SO increased by 123.96%, 344.46% and 547.25%, respectively. Compared with RO, the seed yield under SO increased by 62.09%, 31.33%, 71.79% and 12.21% under N0, N1, N2 and N3 treatments, respectively. (2) The root crown diameter, plant height, first effective branch height and branch number of SO oilseed were significantly higher than those of RO at maturity stage, and the increase in each agronomic trait index was significant under different cropping systems with the increase in nitrogen application; the root biomass and above-ground biomass of SO were significantly higher than those of RO at all growth stages, but the root shoot ratio was lower than that of RO. The root shoot ratio decreased significantly after seedling stage in both cropping system with increasing nitrogen application. (3) Nitrogen content and nitrogen accumulation in the root, pod shell, stalk and seeds of SO were higher than those in RO, and the increases in nitrogen content and nitrogen accumulation in each part were significant with the increase in nitrogen application; the apparent nitrogen recovery efficiency under SO was higher than that under RO, and the apparent nitrogen recovery efficiency under RO increased with the increase in nitrogen application. (4) Compared with the RO, the soluble sugar content of pod shell under SO was lower, while the amino acid content and amino acid/soluble sugar content were higher with the same nitrogen application. The soluble sugar content decreased, but the amino acid content and amino acid/soluble sugar content increased with the increase of nitrogen application. Therefore, the oil content of oilseed under SO was lower than that under RO due to the limitation of fatty acid synthesis substrate, and the oil content of seeds decreased significantly with the increase of nitrogen application in cropping system. Oil yield was the maximum in both cropping system at 270 kg·hm-2 nitrogen application level, 1 678.60 and 1 665.33 kg·hm-2 for RO, and 1 684.03 and 1 687.10 kg·hm-2 for SO, respectively, but the difference in oil yield between 180 and 270 kg·hm-2 nitrogen application for SO was not significant.【Conclusion】In conclusion, the nitrogen rate for RO could be controlled at about 270 kg·hm-2, but the nitrogen rate for SO could be controlled at about 180 kg·hm-2 to ensure higher nitrogen use efficiency and higher oil yield.

Understanding the responses of winter green manure February orchid (Orychophragmus violaceus) to different levels of nitrogen (N) supply in Northern China and determining the optimal soil N supply level to meet N demands of green manure production with high yield and efficiency, could provide a theoretical foundation and practice reference for maximizing ecological effects of green manure and optimizing N management for spring maize-green manure rotation system in intensive farmland in Northern China. We carried out a field experiment in a site which had received no fertilizer for many years. The aboveground biomass accumulation, N uptake of February orchid and soil residual inorganic N before green manure incorporation, as well as the N balance during the green manure growing season were determined under different levels of N supply. The results showed that N fertilizer application significantly increased the biomass and N uptake of February orchid under low soil inorganic N content (15 kg·hm-2 in 0-90 cm soil layer). At the application rate of 90 kg·hm-2, the biomass (dry mass) and N uptake reached the maximum, being 2031 and 42 kg·hm-2, respectively. The soil residual inorganic N amount rose with the increases of N fertilizer application before sowing, growing very rapidly once the application rate was over 60 kg·hm-2. With the increases of N application rate, the calculated apparent N balance changed from deficit to surplus in the growing season of February orchid. The inputs and outputs of N reached a balance at the application rates of 60 to 90 kg·hm-2. The relationships between February orchid biomass, N uptake, soil inorganic N before green manure incorporation, and soil N supply amount (0-90 cm preplant soil inorganic N content plus N application rate) could be fitted by the quadratic, linear plus plateau and exponential models respectively. Based on the simulation, we calculated the preplant soil N supply and soil residual inorganic N content before green manure incorporation would be 136 and 78 kg·hm-2 individually, as the biomass of February orchid reached the maximum (2010 kg·hm-2). While N uptake was at the highest level of 40 kg·hm-2, the biomass of February orchid was 95% of the maximum biomass mentioned above (1919 kg·hm-2) and the soil residual inorganic N before green manure incorporation decreased to 57 kg·hm-2 whose corresponding minimum soil N supply amount was 105 kg·hm-2. This value was quite near to the recommended soil residual inorganic N (100 kg·hm-2) after maize harvest under optimized N management in Nor-thern China. Taken together, our results showed that the level of soil N supply should be at approximately 100 to 105 kg·hm-2 in spring maize-winter green manure system for improving tradeoffs between agronomic and environmental impacts.

Increasing atmospheric nitrogen (N) deposition has profound effects on carbon (C) cycling in forest ecosystems. As an important part of belowground C dynamics, soil respiration is potentially affected by changing N availability. However, the responses of total soil respiration (RST) and its three components, soil respiration derived from plant roots (RSR), root-free soil (RSS) and the litter layer (RSL), to such N enrichment remains poorly understood. To assess the effects of N enrichment on soil respiration components, three levels of N addition, namely low (LN, 50 kg N ha−1 year−1), medium (MN, 100 kg N ha−1 year−1) and high (HN, 150 kg N ha−1 year−1), were conducted over five growing seasons from 2011 to 2015 in a temperate Chinese pine (Pinus tabulaeformis) forest in northern China. A control plot without N addition (CK) was also established. The five-year mean annual rate of RST was 2.18 ± 0.43 μmol m−2 s−1, and the contributions of RSR, RSS and RSL were 8.8 ± 3.1%, 82.2 ± 4.5% and 9.0 ± 5.5%, respectively. Compared with CK, RST was significantly increased by 16.5% in the HN plots, but not in the LN or MN treatments. RSS was significantly decreased by 18.1%, 26.6% and 18.4% in the LN, MN and HN plots, respectively, due to the reduction of both microbial biomass carbon (MBC) and enzyme activity. In contrast, RSR was increased by more than twice under the MN treatment, which promoted root growth and activity (higher fine root biomass and N concentration). A significant elevation in RSL was only detected in the HN plots, where the increased litter input enhanced litter decomposition and hence RSL. Our findings clearly demonstrated that N addition of different intensities had different effects on soil components. In particular, the above- and belowground components of heterotrophic respiration, RSL and RSR, showed contrasting responses to high level addition of N. Thus, we highlight that the response of soil respiration components to N addition should be examined individually. Our results may contribute to a better understanding of soil respiration dynamics under future N scenarios, and have important implications in forest management.

Rice straw return and green manure cultivation in winter fallow season are 2 effective ways of improving soil fertility in south China. Due to the relatively stable carbon to nitrogen ratio, either the rice straw return or green manure cultivation alone has its own limits in practice. Recently, the combined application of green manure and rice straw has been developed, while little is known about the impacts on crop yield and soil fertility. A field trial was conducted at an experimental station managed by National Engineering and Technology Research Center for Red Soil Improvement in Fengcheng, Jiangxi Province, China to explore effects of remaining high rice stubble, inter-planting green manure (Chinese milk vetch,Astragalus sinicus L.) and co-incorporation of rice straw and green manure on double rice and green manure yield and soil fertility. Field experiments were conducted in a rice-rice-winter fallow or rice-rice-Chinese milk vetch (MV) rotation system. A total of 5 treatments with different cultivation practices were included, (ⅰ) CK, rice-rice-winter fallow without rice straw return; (ⅱ) RS, rice-rice-winter fallow with rice straw return; (ⅲ) MV, rice-rice-MV without rice straw; (ⅳ) MV+LRS, rice-rice-MV with return of low stubble (0 cm) of rice straw; (ⅴ) MV+HRS rice-rice-MV with return of high stubble (30 cm) of rice straw. The results showed that co-incorporation of RS and MV significantly increased fresh yield and nitrogen content of MV plants by 13.1％ and 6.8％ in MV+LRS and 32.2％ and 5.2％ in MV+HRS than those in MV alone, respectively. The average yield of double rice yield over the 4 years was significantly increased by 556.8 and 412.8 kg/hm2 in MV+HRS than in RS and MV, respectively. Compared to CK, the soil organic matter (SOM) content was significantly increased by 6.8％ to 8.0％ in RS and MV, the total nitrogen (TN) was marginally affected by the 2 treatments. Compared to CK, the soil inorganic N content was significantly decreased in treatments with RS and MV alone, while the available K was increased in RS. Different from soil inorganic nitrogen, manure treatments greatly improve available P content and the treatment of MV with HRS increased the available P by 18.0％. However, the treatments with rice straw could greatly increased soil available K by 8.0％ (RS), 9.2％(MV+LRS) and 22.8％(MV+HRS), respectively. The soil microbial nitrogen were also significantly enhanced in the combinations than in MV or RS alone (P<0.05). The dissolved organic carbon and nitrogen were greater in the manure-rice straw combination treatments than CK. The treatments with rice straw enhanced the proportion of microbial biomass C in SOC and that of microbial biomass N in TN. Compared with the rice straw and manure alone, the co-incorporation of rice straw and manure increased the proportion of dissolved organic N in TN and inorganic N in TN. Collectively, the co- incorporation of rice straw and green manure could improve the rice yield and soil fertility in present conditions. The practice of keeping high stubble of rice straw standing in the field and returned together withgreen manure had the great promise to maintain and improve soil fertility and rice yield in south China.

The February orchid (Orychophragmus violaceus)-spring maize rotation system is established to resolve the problems caused by the expansion of fallow fields in North China. Based on a site-specific experiment, temporal and spatial variations of soil NO(3-)-N were investigated during the period from February orchid incorporation to maize harvest. The results showed that the nitrate content in soil profiles not only showed a temporal characteristic, i. e., increasing at the beginning of the maize season and decreasing then after, but also showed a spatial characteristic, i. e., the gradual occurrence of the peak of nitrate content from shallower to deeper layer with the growth season of maize. Meanwhile, incorporation of February orchid could affect temporal and spatial variations of soil NO(3-)-N. February orchid planting reduced the soil NO(3-)-N accumulation in the profile of 0180 cm. After incorporation of February orchid, similar characteristics were observed at the seedling and bell stages of maize, i. e., the soil NO(3-)-N mainly stayed in the profile of 0-20 cm, and NO(3-)-N concentrations in the treatments with February orchid were higher in 0-100 cm layer and lower in 100-180 cm layer than those of the treatments without February orchid. After tasseling stage, opposite phenomena were found, and the soil NO(3-)-N content was all relative low. Overall, incorporation of February orchid could increase the storage capacity of soil NO(3-)-N in the profile of 0-180 cm.

A pot experiment was conducted to investigate the effects of incorporation February Orchid,applied as green manure,on dry matter accumulation and nutrient uptake in maize and soil nutrient status. There were five treatments,control,two green manure incorporation rates (50%G and G),conventional fertilizer application rate ( F) and green manure combined with fertilizer ( G+F) in the experiment. The results showed that green manure application could supply a certain amount of nutrients. The biomass,grain yield and nutrient uptake of maize were significantly increased after green manure application,and were enhanced with the application rates as well. The bi-omass and N,P,K absorption in the treatments of 50%G and G were similar to those in F and G+F at jointing stage,indicating that sole green manure applications could satisfy the normal growth of maize before jointing. Com-A pot experiment was conducted to investigate the effects of incorporation February Orchid,applied as green manure,on dry matter accumulation and nutrient uptake in maize and soil nutrient status. There were five treatments,control,two green manure incorporation rates (50%G and G),conventional fertilizer application rate ( F) and green manure combined with fertilizer ( G+F) in the experiment. The results showed that green manure application could supply a certain amount of nutrients. The biomass,grain yield and nutrient uptake of maize were significantly increased after green manure application,and were enhanced with the application rates as well. The bi-omass and N,P,K absorption in the treatments of 50%G and G were similar to those in F and G+F at jointing stage,indicating that sole green manure applications could satisfy the normal growth of maize before jointing. Com-pared with the F treatment,green manure combined with fertilizer application could further benefit the nutrient up-take and the grain yield of maize,i. e. ,the G+F treatment increased the N,P,K uptake of maize at maturity by 10. 8%,28. 1%,45. 8%, respectively, and increased the yield by 9. 1%. Green manure application might have effects on the root growth and P,K uptake of maize,resulting in that root biomasses and root to shoot dry weight rati-os were increased and relative P and K absorption rates were higher than N absorption rate in all treatments incorpo-rated with green manure. Treatments with sole green manure (50%G and G) depleted the soil Nmin and Olsen-P, while the soil Nmin,Olsen-P,and NH4OAc-K were enhanced remarkably in the G+F treatment,showing that green manure combined with fertilizer application could effectively improve the soil nutrient status.

Effects of reducing farmer's fertilizer rates on yield and nutrient utilization of spring maize were investigated by using February Orchid(Orychophragmus violaceus L.) as green manure.There were six treatments,control(F0),farmer's fertilizer rate(F100),green manure application only(F0+G),and green manure combined with 70%,85% and 100% of farmer's fertilizer rates(F70+G,F85+G and F100+G),respectively.The results show that both the fertilizer and the fertilizer combined with green manure could increase the yields and nutrient accumulation amounts of shoot and component tissues,and could improve the nutrient distribution in maize.The yields of F100,F70+G,F100+G and F85+G are 101.4,108.4,115.5 and 130.4 g/plant,which are about 120.9%,129.2%,137.6% and 155.3% higher than the control,respectively.Compared with F100,maize grain yield and shoot N accumulation under the treatment of F85+G are significantly increased by 29.0 g/plant and 0.65 g/plant,respectively.There are no significant differences among the treatments of F100,F85+G and F100+G for biomass and nutrient accumulation.The nutrient accumulation and distribution in grains under the green manure application combined with fertilizer treatments(F100+G,F85+G and F70+G) are similar to those of the F100 treatment.

Effects of reducing farmer's fertilizer rates on yield and nutrient utilization of spring maize were investigated by using February Orchid(Orychophragmus violaceus L.) as green manure.There were six treatments,control(F0),farmer's fertilizer rate(F100),green manure application only(F0+G),and green manure combined with 70%,85% and 100% of farmer's fertilizer rates(F70+G,F85+G and F100+G),respectively.The results show that both the fertilizer and the fertilizer combined with green manure could increase the yields and nutrient accumulation amounts of shoot and component tissues,and could improve the nutrient distribution in maize.The yields of F100,F70+G,F100+G and F85+G are 101.4,108.4,115.5 and 130.4 g/plant,which are about 120.9%,129.2%,137.6% and 155.3% higher than the control,respectively.Compared with F100,maize grain yield and shoot N accumulation under the treatment of F85+G are significantly increased by 29.0 g/plant and 0.65 g/plant,respectively.There are no significant differences among the treatments of F100,F85+G and F100+G for biomass and nutrient accumulation.The nutrient accumulation and distribution in grains under the green manure application combined with fertilizer treatments(F100+G,F85+G and F70+G) are similar to those of the F100 treatment.

In the February Orchid(Orychophragmus violaceus)/Spring Maize(Zea mays L.)system,ammonia volatilization was investigated by the method of in situ field determination during the basal and top dressing fertilization periods of spring maize to study the characteristics of ammonia volatilization after the February Orchid was incorporated into soil as green manure.The results showed that the ammonia volatilization amounts ranged from 0.94 kg/ha to 3.27 kg/ha after the basal fertilization,the N loss rates resulted from ammonia volatilization were 1.34%-2.91%,accounting for 3.12%-6.80% of the total ammonia volatilization amounts of the whole spring maize season.Under the same nitrogen application levels,the ammonia volatilization amounts of treatments with green manure were averagely 1.04 kg/ha higher than those without green manure.After top dressing fertilization,the ammonia volatilization amounts were 27.17-46.81 kg/ha,and the N loss rates caused by ammonia volatilization varied from 34.50% to 41.61%,accounting for 93.20%-96.88% of the total ammonia volatilization amounts.No obvious differences were observed between the treatments with and without green manure.In general,the ammonia volatilization increased as a result of the N addition,while was little affected by the green manure.During the whole spring maize season,total ammonia volatilization amounts ranged from 28.50 kg/ha to 48.32 kg/ha in the treatments of fertilization,meanwhile,the N loss rates caused by ammonia volatilization varied from 16.28% to 20.20%.

The sensitivity of 100 isolates of Blumeria graminis f.sp.tritici sampled from eight provinces or cities to triadimefon and fenpropidin was tested by seed treatment and detached leaf segment methods.The results showed that the mean EC50 of all the tested isolates to triadimefon was 47.27 mg/L,and the mean resis-tance factor(RF) was 22.62.The frequency of resistant isolates to triadimefon reached 97.00%.The resistance factor of the tested isolates from Shandong to triadimefon was the highest,reached 52.63.The base-line of sensitivity of B.graminis f.sp.tritici to fenpropidin was 100.47 mg/L.There was no significant cross-resistance between triadimefon and fenpropidin in B.graminis f.sp.tritici population.These results will provide the refe-rence for fungicide resistant management and the rational use of fungicides.

To determine the effects of rapid release sulphur(RRS) application on winter wheat in Northern China,field trials were conducted respectively in Taian of Shandong Province and Cangzhou of Hebei province to evaluate the effects of rapid release sulphur(RRS) on grain yield,seed protein content,sulfur content and economic profit for winter wheat.Five treatments were applied in the experiments: control(0 kg/hm2),sulfur powder with low rate(30 kg/hm2),sulfur powder with high rate(60 kg/hm2),RRS with low rate(30 kg/hm2) and RRS with high rate(60 kg/hm2).Results illustrated that wheat yield was increased by S fertilization on high available sulfur content soil.And the yield responses were affected by the forms and rates of sulfur fertilizer.The RRS increased wheat yield higher than the sulfur powder.The high rate RRS treatment achieved the highest wheat yield at two sites.Compared with the control,the grain yields were enhanced by 8.3% and 10.1% at Tai'an and Cangzhou sites respectively.Sulfur fertilization improved the sulfur content in wheat grain,but only high rate sulfur treatments at Cangzhou site increased the grain sulfur content significantly.No significant difference was found between two elemental sulfur fertilizers.RRS treatment improved the seed protein content of wheat only for Tai'an site.The low rate RRS treatment yield had higher seed protein content than that in low rate sulfur power treatment.However,there was no significant difference among sulfur treatments at Cangzhou site.Sulfur fertilization led to the economic profit for wheat production.Economic profits were higher for RRS fertilizer than sulfur powder.At Tai'an site,the high rate RRS treatment yielded the highest economic profit(1369 yuan/hm2) and highest value cost ration(10.5).At Cangzhou site,the low rate RRS treatment achieved the economic profit of 1111 yuan/hm2and highest value cost ratio(16.4).Optimal application of RRS will maintain or improve seed quality while increasing economic profits and wheat grain yield.