One of the major challenges in the application of biological control agents into the soil is their inability to withstand competition from natural microflora. In this study a management programme involving fungal biological control agents Trichoderma harzianum (TH) and Purpureocillium lilacinium (PL), and the organic amendment neem was carried out for the control of Meloidogyne javanica and Fusarium oxysporum f. sp. lycopersici (FOL). The experiment was carried out in sterile and non-sterile soil in order to test the efficacy of biological control in natural soil conditions. This experiment was repeated twice. A Wilcoxon's Signed-Rank test indicated there were no significant (P < 0.05) differences in fusarium wilt control in sterile and non sterile soils in the treatments PL neem and TH neem, but there was significantly (P < 0.05) higher control of M. javanica in the same treatments in sterile soils compared to non sterile soils. The combinations of fungal antagonists and neem were effective in non sterile as in sterile soils in the control of fusarium wilt, while being less effective in the control of M. javanica. Thus the biological control agents can be very effective in the control of fusarium wilt in natural conditions where the soil is not sterilised, but be less effective in the control of M. javanica in the same conditions. There is therefore potential of integrated management of fusarium wilt and root-knot nematodes (RKN) by these biological control agents in natural soil field conditions as an alternative to using chemicals.
Bush tea (Athrixia phylicoides DC.) is a popular aromatic plant, indigenous to South Africa. For many decades, indigenous people have widely consumed the tea as a healthy beverage and a medicine. The objective of the study was to investigate the influence of nitrogen fertiliser application on the quality, pharmacological activities and metabolite profiles of the leaves and twigs of bush tea cultivated under greenhouse and field conditions. Treatments consisted of 0, 75, 150, 225, 300 and 375 kg/ha N, arranged in a randomised complete block design with five replicates. Parameters measured were leaf tissue nitrogen, total polyphenols, total flavonoids, total tannins, total antioxidants, antimicrobial activity and cytotoxicity. In addition, metabolites were identified and measured using gas chromatography linked to mass spectrometry (GC-MS) and liquid chromatography linked to mass spectrometry (LC-MS). The results of this study showed a significant quadratic response of total polyphenols, total flavonoids, total tannins and total antioxidants of bush tea leaves and twigs, irrespective of the growth environment ranging from 150 to 225 kg/ha N. The results further suggested that, despite the growing environment, nitrogen treatments did not improve the minimum inhibition concentration and minimum microbicide concentration of bush tea with extract concentrations ranging from 25.0 to 3.1 mg/g. Bush tea was found to be non-toxic (IC50 above 100) under both growing conditions, irrespective of nitrogen treatments. Despite trials being conducted under greenhouse and field conditions and with different nitrogen treatments, there were no distinct differences regarding the gas chromatography linked to mass spectrometry and liquid chromatography linked to mass spectrometry compounds. The future aims of the study are to investigate the effects of nitrogen fertilisation, the timing of nitrogen fertilisation and the planting density on the yield, quality, plant metabolites and pharmacological activity of field-grown bush tea.
Purpose: The purposes of this study were to determine the effect of matrine on the migration and the colonization dynamics of the two fluorescent-tagged rhizobia in Gannong No.5 alfalfa (Medicago sativa L. Gannong No. 5) tissues, and also to determine the effect of the combination treatments on alfalfa seedlings' growth.Materials and methods: 0, 100, 200, 300 and 400 mg L-1 matrine levels were added into two cyan fluorescent protein (CFP)-tagged rhizobia; Ensifer meliloti LZgn5f (gn5f) and Ensifer meliloti 12531f (12531f), respectively; and drenched the alfalfa root with the inoculants. Then the migration and colonization of the two rhizobia in alfalfa on D7, D14, D21 and D28, and subsequently seedling growth were investigated.Results: The results showed that the optimum matrine level enhanced the colonization of both fluorescent-tagged rhizobia in alfalfa roots and the highest colonization densities of log 6.31 cfu g(-1) and log 5.87 cfu g(-1) were achieved by adding 300 mg L-1 matrine into 12531f and adding 100 mg L-1 matrine into gn5f, respectively. They could migrate to the aerial tissues and most colonize stems through the application of adding 300 mg L-1 matrine into 12531f and 100 mg L-1 matrine into gn5f, respectively. No fluorescent-tagged rhizobia were detected in the control treatment. Alfalfa seedling growth parameters like leaf chlorophyll content, seedling growth rate, root length, seedling biomass and total N percentage also increased the most when 300 mg L-1 matrine was added into 12531f and 100 mg L-1 matrine added into gn5f treatments.Conclusions: Our results suggest that 300 mg L-1 matrine added into 12531f and 100 mg L-1 matrine added into gn5f might be exploited to promote the colonization of rhizobia in alfalfa tissue and positively impact growth and yield, indicating possible benefits for plant cultivation.
Ambient UV radiation is recognised as an important environmental factor in the regulation of plant growth and development, and selenium (Se) as a beneficial nutrient that can increase plant tolerance to different environmental constraints. The effects on hybrid buckwheat plants of full (+UV) and reduced (-UV) ambient UV radiation without (-Se) and with (+Se) foliar Se treatment (10mgL(-1) sodium selenate) provided the four conditions of Se-UV-, Se-+UV, +Se-UV and +Se+UV. Plant morphological, biochemical and physiological properties were examined, along with leaf elemental composition and content, efficiency of Se enrichment, and production parameters. Leaf anatomical parameters under all conditions were mainly affected by UV radiation, and less so by Se. +Se+UV plants showed a trade-off between primary and secondary metabolism, which resulted in high levels of protective substances (e.g. anthocyanins, UV absorbing compounds), and low levels of photosynthetic pigments. All +UV plants were significantly shorter in comparison to those under the reduced -UV, while biomass production was highest for -Se+UV plants and lowest for +Se+UV plants. +Se plants accumulated approximate to 20-fold greater Se content compared to -Se plants, and full ambient UV radiation partly reduced this effect. +UV plants showed increased phosphorus content in leaves, independent of Se status, while +Se plants showed increased K content. Si content was increased by Se treatment and decreased by the full UV exposure. Se treatment and the ambient UV radiation, separately have positive effects on growth and production of this hybrid buckwheat, while the combination of the Se treatment and ambient UV resulted in lower yields. However, under these conditions (+Se+UV), the buckwheat plants established good protection against the different environmental constraints that are becoming more and more frequent due to changes to our climate.
The recent drought in South Africa has reduced the production of both dryland and irrigated wheat. This study evaluated physiological traits of irrigated wheat genotypes in response to water stress (WS) imposed at different growth stages. A 8 × 2 × 3 [(genotypes) × (water treatmets; stresses and non-stressed) × (growth stages; tillering, flowering and grain filling)] factorial experiment based on a randomised complete block design with three replicates was conducetd. In general, the rate of photosynthesis was unaffected by WS except for genotypes LM43 at tillering and LM98 at grain filling. Stomatal conductance (SC) and transpiration rate (Tr) followed the same treand except for genotype LM35 which reduced its SC and Tr significantly at grain filling. Instantaneous waster use efficiency (IWUE) of genotype LM35 and LM57 was unaffected (p > 0.05) by WS at tillering but at flowering stage it was affected. However, at grain filling IWUE was affected (p < 0.05) in genotypes LM35, ML57, LM79 and LM 98. The relative water content was unaffected at tillering except for LM35 and LM47 genotypes whereas at flowering LM57, ML79, LM83 and LM98 were affected. These results indicate some degree of drought tolerance of these genotypes at different growth stages.
ABSTRACT To what extent might a crop with increased plant N uptake efficiency and/or N demand increase plant biomass and soil carbon storage, decrease N leaching, and reduce the need for N fertilisation? This was assessed for a fertilised sandy loam site in central Sweden cultivated with spring barley for a four year period using a process based crop and soil simulation model (SOILN) calibrated to fit observations of field experiments with non-modified crops. Crop properties were changed in accordance with previous model applications to other crops with higher N uptake and utilisation efficiencies, to resemble potential effects of breeding. For the modified crops a doubling of daily uptake efficiency of soil mineral N and/or increase of radiation use efficiency by 30%, increased plant biomass by 3%–30%, decreased N leaching by 1%–30% and increased soil organic carbon (SOC) content by 1–12 g C m−2 year−1. The larger changes were mainly due to increased uptake efficiency. Fertilisation of the modified spring barley crop could be reduced while still producing the same plant biomass as the non-modified crop. The plant biomass to N leaching ratio of the modified crops increased. The simulated changes in plant biomass and SOC were sensitive to weather conditions suggesting that in situ experiments would need to cover a large range of weather conditions to evaluate the performance of new crop traits under climatic variability. The study suggests a strong need that field experiments are accompanied with model applications, when exploring the potential of the modified crops under variable conditions.
With increasing demand for sustainable production, the need to effectively utilise site-based resources increases. One such resource is the remaining crop residues, both above and below ground, after harvest. In order to assess the magnitude of this resource, this study determined the plant nutrient contribution of residues from 17 different crops in seven different regions of Slovakia over a nine-year period. The soil profile 0.0–0.3 m was taken into account at belowground residues sampling. The results showed that winter rape, mustard, corn maize, triticale, winter rye with straw and sunflower left the most residues, exceeding 8 tons of dry biomass per hectare. Root crops (sugar beet, potatoes) and peas left less than 3 tons of residual dry biomass per hectare. Using these data, the nutrient potential coefficient, i.e. the amount of nutrients left by production of one ton of the main product was calculated by polynomial regression. With these coefficients and the known yield of a given crop, it was possible to calculate how much nitrogen, phosphorus and potassium each crop leaves in the soil after harvest. It was found that the amount of nitrogen left ranged from 20 to 132 kg, phosphorus from 2 to 24 kg and potassium from 13 to 218 kg per hectare. This has to be taken into account when calculating the fertiliser requirement of the subsequent crop in order to achieve better resource utilisation, thereby reducing the risk of eutrophication and improving farm profits by reducing expenditure on fertiliser.
Purpose: The current study was aimed to analyse the occurrence of water and nitrogen stress in spring barley and estimate their effects on the crop performance under low-input and conventional management.Materials and methods: Field experiments were conducted during 2007-2009 at the Institute of Agriculture, Lithuanian Research Centre for Agriculture and Forestry on a sandy-loam soil. The management systems were: (a) conventional, with the application of fertilizers and pesticides adjusted to target 5 t ha(-1) grain yield; and (b) low-input, without fertilizers and pesticides. Biomass and nitrogen concentration, leaf area index, soil moisture, drainage water runoff and ground water table were measured periodically during the growing season.Results: In all three experimental years, the annual precipitation was close or above the climate normal, but a large part of the rainfall (up to 310 mm) was lost through drainage contributing to the occurrence of temporary moisture deficit in late spring or summer. Water stress resulted in a lower spring barley biomass accumulation rate and lower biomass yield in the years characterized by sub-optimal rainfall distribution. Direct measurements of water retention in the soil and DSSAT model simulations gave relatively good indication of water stress occurrence. Under the low-input management, nitrogen nutrition level was a major constraint for spring barley biomass and grain yield formation.Conclusions: Under Central Lithuania's conditions, spring barley frequently experiences temporary water stress, because a relatively high proportion of annual precipitation is lost during the non-growing period. This crop can benefit from anticipated increased precipitation and carbon dioxide levels if adequately provided with nitrogen.
The use of saline water for plant production will become increasingly necessary over future decades. In some cases, fruit quality such as in tomato, can be improved by irrigation with saline water. The influence of different salt concentrations on physiological responses and the expression of some selected genes of cherry tomato (Solanum lycopersicum L), cv. West Virginia 106, was examined. Tomato plants were grown in peatmoss substrate and irrigated with 0, 25, 50, 75, 100 or 150mM sodium chloride (NaCl) in a glasshouse. The NaCl treatments of 75, 100 and 150mM salt resulted in shorter plants, decreased stem width, a lower plant dry weight, fewer flowers, and smaller leaf area, while yield was reduced by treatment with concentrations of 50mM NaCl and above. Average fruit weight and fruit number were also negatively affected by treatment with 50mM salt and above. Salinity treatment led to increased fruit total soluble solids, titratable acidity and firmness and improved the taste index. Salt-responsive marker genes identified in Moneymaker were also induced in cherry tomato but not at the highest salt concentrations. Our results indicated that cherry tomato treated with 25mM NaCl produced fruit with improved quality in comparison with non-salinized control plants without compromising yield, while at 50 and 75mM the improved fruit quality was accompanied by a reduction in yield.
Rhizomania, caused by Beet necrotic yellow vein virus (BNYVV), is one of the most devastating diseases on sugar beet throughout the world. A total of 235 BNYVV-infested soil samples taken from 29 provinces during the growing seasons of 2004–2005 and 2010–2011 were investigated for resistance-breaking properties of BNYVV isolates. BNYVV resistant (Rz1, Rz1 + R2, Rz1 + C48 + minor genes) and susceptible (rz1) sugar beet cultivars were grown in the BNYVV-infested soils by the bait plant technique, and virus infection was evaluated based on disease symptom and DAS-ELISA. Of the soil samples tested, 57.4% produced infection in the roots of sugar beet cultivar (cv.) containing the Rz1 gene, 51.9% in cv. carrying the Rz1 + Rz2 and 18.9% in cv. carrying the Rz1 + C48 + minor genes. Also, the presence of Beet soil-borne virus (BSBV) was evaluated by TAS-ELISA. Additionally, the presence of BNYVV RNA-5 component was investigated by RT–PCR using the primers specific for p26 coding region. Our results revealed that BNYVV isolates compromising resistance genes are highly common and widespread in sugar beet production areas in Turkey, and it seems unlikely that BSBV and/or RNA-5 were directly involved in RB-event.
Data from a field experiment conducted in China's Loess Plateau (2013–2015) were used to determine the energy balance of winter wheat (Triticum aestivum L.) as affected by tillage and straw treatments. Tillage treatments included chisel plow, no tillage, and mouldboard plow. Crop straw levels included straw returning and straw removed. The energy balance was evaluated by comparing the following parameters: net energy, energy profitability, energy use efficiency, and energy intensity. The yield parameters were significantly influenced by the tillage treatments and revealed that the chisel plow entailed fewer field operations and lower energy requirements with a higher yield than mouldboard plowing tillage. The highest proportion of energy input came from a nitrogen fertiliser, followed by diesel fuel. The total energy input applied per hectare increased with an increase in the tillage intensity, and the lowest energy input was required for the no tillage case with the straw returning treatment, and the highest for the case of mouldboard plow with the straw returning treatment. The lowest average energy intensity was recorded for the no tillage case, followed by the case of chisel plow tillage in both cropping seasons. Moreover, in the case of mouldboard plough tillage, the maximum energy intensity was recorded in both cropping seasons. In the cases of the chisel plow tillage and the no tillage, we observed the maximum energy gain, while in the no tillage case, we observed the maximum energy use efficiency. The net return and the benefit/cost ratio were higher in the case of straw returning than those in the case of no straw treatment. We concluded that no tillage and chisel plow tillage with straw returning could improve the energy use efficiency and the benefit/cost ratio of winter wheat production systems.
In South Africa, chickpea is becoming one of most consumed pulses but its demand is currently met through imports. In general, the imported chickpea grain is likely costly with a relatively lower nutritional value as is largely the case with most imported food products. In this review paper, we discuss how its production in South Africa would improve the nutritional status of humans and livestock and enhance the fertility status of cropping fields. Other benefits include that its production would be of financial reward to local farmers and ensure better nutritional quality and boost the country's economy and global competiveness. Studies conducted in South Africa have assessed the crop's suitable planting season and where planted in winter, irrigation has sustained its growth. We discuss challenges of its plantation in the dry winter season given the on-going water restrictions on agricultural activities, drought, low water levels in dams, and water scarcity. Suggestions include identification of low-temperature locations and fields experiments be established to assess the crop's adaptation to summer cropping. Field studies conducted locally have also included the nutritional requirements of chickpea. The review discusses possible solutions to low soil fertility suggest the use of plant biostimulants for enhanced fertiliser use.
Purpose: In recent years, interest in plant nutrition research has arisen with a strong focus on organic forms. The aim of this study was to determine the effect of different organic fertilizers on growth, yield, fruit quality and polyphenol content in soilless grown grape tomatoes under greenhouse conditions.Materials and methods: Tomato plants were subjected to three organic nutrient solutions, which consisted of different mixtures of several OMRI (Organic Materials Review Institute) certified nitrogen fertilizers of industrially processed residues: Treatment I: solid and soluble liquid fertilizers of animal raw materials, natural potassium sulphate-non-synthetic, and calcium chloride; Treatment II: solid and soluble liquid fertilizers of animal raw materials, by-product of marine raw material (soluble liquid), natural potassium sulphate-non-synthetic, and calcium chloride; and Treatment III: solid fertilizers of animal raw materials, natural potassium sulphate-non-synthetic, and calcium chloride to 100% [0-30 days after transplanting (DAT)], 125% [31-80 DAT], and 150% [>81 DAT]. The Steiner solution (SS) was used as a control (Treatment IV).Results: Yield did not differ between organic and conventional treatments, ranging from 3.04 to 3.35 kg m(-2) while fresh weight in organic treatments was 3.14 compared to 3.2 kg m(-2) in plants fed with the SS. No significant differences in plant height or fruit quality were found. The application of organic fertilizers positively affected the total hydrolysable and condensed polyphenols of tomato fruits compared to the control. Twelve phenolic compounds were identified, highlighting 3-Caffeoylquinic acid, salvianolic acid and 5,6-Dihydroxy-7,8,3',4'-tetramethoxyflavone (Treatment I) and Medioresinol (Lignan) (Treatment II).Conclusions: The results indicated that organic fertilization through animal-based fertilizer application is a feasible alternative for grape tomato production under greenhouse conditions.
PurposeBesides nitrogen, phosphorus and potassium, sulphur is nowadays considered fundamental for plants, and due to its deficit in many regions, should be provided to crops by fertilization. The enzymes, rhodanese and arylsulphatase, take part in transforming sulphur in soil.Material and methodsThe seaweed biostimulant Kelpak (auxins 11mg l(-1) and cytokinins 0.031mg l(-1)) was applied to increase the uptake and accumulation of sulphur affecting the yield of oilseed rape cv. Chagall'. Field experiments were conducted in Poland (53 degrees N.18 degrees E), in Alfisol (USDA) over 2010-2013. In the experiment, the nitrogen, potassium and phosphorus rate applied was as follows: high: 180 N, 70 P, 132 K[kg ha(-1)] or low: 144 N, 35 P, 66 K[kg ha(-1)], fertilization rate with elemental S (36 or 0kgha(-1)) and with biostimulant (Kelpak 2lha(-1) in autumn and 2 l ha(-1) in spring) or without it.ResultsThere was found no relevant effect of biostimulant on the activity of the enzymes studied. With a low sulphates content in soil during ripening the rape, the activity of arylsulphatase increases. The highest rate of NPK resulted in a 27-42% increase in the content of SO42- in soil as compared with the soil sampled from NPK fertilization at lower rates. Sulphur recovery efficiency from fertilizer with S elemental increased for higher NPK fertilization.ConclusionsBiostimulant application can compensate for a low level of oilseed rape crops cultivation technology (low rates of NPK fertilization) by improving the use of S from a fertilizer. In growing oilseed rape, it is essential to correlate the management of NPK and S fertilization at the right rate for a high sulphur recovery efficiency.
One of the major challenges in crop production is increase efficiency of non-renewable P sources, or replace them with renewable sources. The objective of this study is to evaluate the effects of phosphorus (P) fertilization using reactive natural phosphate, filter cake, peat and biofertilizer on soil P content, foliar P content and growth of noni seedlings. The treatments were: control (without P fertilization); phosphorus; filter cake; phosphorus+filter cake; phosphorus+filter cake+peat; and phosphorus+filter cake+peat+biofertilizer. All treatments were replicated four times and arranged in a completely randomized design. The treatments phosphorus+filter cake; phosphorus+ filter cake+peat; and phosphorus+filter cake+peat+biofertilizer increased phosphorus content in soil and in leaf, and the growth of noni seedlings. Our results indicates that natural reactive phosphate enriched with filter cake can be used as phosphate fertilizer on noni seedlings cultivation.
Globally, most of the crop-related developmental projects collapsed due to the existence of aggressive plant-parasitic nematodes. Intensive South African biofortification efforts using exotic and local sweet potato (Ipomoea batatas) cultivars have hardly considered the inclusion of nematode resistance in plant breeding, despite the withdrawal of most nematicides from agrochemical markets. The objective of this study was to screen 12 selected biofortification sweet potato cultivars for host-status to South Africa tropical root-knot (Meloidogyne species) nematodes. Three exotic orange-fleshed, three local orange-fleshed and six cream-fleshed cultivars were used in three separate experiments of M. javanica and races 2 and 4 of M. incognita. In each experiment, 6000 eggs and second-stage juveniles/plant were used for inoculation, with nematode assessment performed at 56 days after inoculation. All tested biofortification exotic (except for cv. 'W-119') and local cultivars were hosts to Meloidogyne species and races, whereas three non-biofortication local cultivars, namely, 'Bosbok', 'Blesbok' and 'Mvuvhelo' were non-hosts. In conclusion, the findings suggested the likelihood of the existence of non-host-status in certain exotic and local sweet potato cultivars for use in plant breeding programmes against South African Meloidogyne species and races.
This study aims to investigate the response of 10 Greek Oregano (Origanum vulgare subsp. hirtum) populations, collected across Greece, under 3 levels of N-fertilization during 2012 and 2013. The populations were differentiated for dry matter (from 32.7 to 63.3 g center dot pot(-1)), for essential oil content (from 2.31 to 5.86 ml center dot 100(-1) g dry weight) and for amount of essential oil (from 1.37 to 2.46 ml center dot pot(-1)), for both years. Those with the highest dry matter (1-"Palaiochori" and 5-"Gliki") and the highest essential oil content (10-"Gytheio" and 9-"Achladocastro") were superior by 30%, as compared to the general mean of the experiment. The populations 3-"Litochoro" and 5-"Gliki" had an increased amount of essential oil (24%) as compared to the general mean of the experiment. An additional nitrogen supply (N-0 to N1 level) increased dry matter production and amount of essential oil per pot, while decreased essential oil content for all populations. Further increase of nitrogen supply, favored six populations for dry matter production and two populations for amount of essential oil per pot while had almost no effect on five populations for essential oil content. The superior populations could be used in a breeding program as starting material for the development of new cultivars.
The objective of this two-year field experiment was to study the effects of irrigation amount, N rate, and irrigation water salinity on cotton growth and the fate of N fertilizer. The movement of N through the plant-soil system was traced using N-15-labeled urea. The study consisted of twelve treatments, including two irrigation amounts (405 and 540 mm, I405 and I540, respectively); two N application rates (240 and 360 kg N/ha, N240 and N360, respectively); and three irrigation water salinity levels [0.35, 4.61 and 8.04 dS/m, representing fresh water (FW), brackish water (BW), and saline water (SW), respectively]. A randomized complete block design was used with three replications. The results showed that cotton biomass, N uptake, and yield increased as irrigation amount and N amount increased; however, all three variables were significantly less in SW than in FW and BW. Plant N-15 recovery rates were greater (i) in the I540 treatments than in the I405 treatments and (ii) in the N360 treatments than in the N240 treatments. Plant N-15 recovery rates in BW were 7.98% and 30.01% greater than those in FW and SW, respectively. Residual soil N-15 increased as N fertilizer amount increased but declined as irrigation amount increased. Residual soil N-15 in BW and SW was 6.02% and 21.44% greater, respectively, than in FW. Total N-15 recovery was significant greater in BW than in FW and SW. The N-15 leaching losses increased significantly with increases in irrigation amount, irrigation water salinity, and N rate. Our study suggests that if appropriate amounts of irrigation water and N fertilizer are used, then brackish irrigation water (4.61 dS/m) will not affect cotton growth, yield and N recovery. In contrast, saline irrigation water (EC > 8 dS/m) reduces cotton growth, yield, and N use efficiency.
Determining genotypic responses to soil fertility may assist selection of cultivars that can be adapted to varied soil fertility regimes, and such selection under field conditions is still limited. A two-year field experiment was conducted in long-term field trials to investigate wheat genotype effects on early growth, yield and nutrient accumulation as affected by varied long-term soil fertility managements and nitrogen (N) fertilization. Results show that the early growth, grain yield and nutrient accumulation of spring wheat plants were strongly affected by soil fertility managements and genotypes. Early shoot and root biomass of singly grown plants and leaf canopy growth under standard growth density was associated with subsequent grain yield of plants under standard growth density across the gradient in soil fertility levels. Taifun and Thasos had stable higher yield and N and phosphorus (P) uptake across varied soil fertility regimes compared with other genotypes. Okilde, however, increased yield by 8-34% and N and P accumulation by 1-22% only when grown in the high organic manure treatment compared with other genotypes, indicating that it is more adapted to high organic fertility regimes. Therefore, the different responses and adaptations of genotypes to soil fertility regimes should be included during selection of cultivars.
Field experiments were conducted to determine the effects of nitrogen (N) fertilization and manure addition on the soil-soluble nitrogen (SSN) (soil mineral N (SMN); soil-soluble organic N (SSON)) and soil-retained N (SRN) (soil fixed ammonium; soil microbial biomass N). The combined application of manure and inorganic N (different N fertilizer rates: M3N0, M3N1, M3N2, and M3N3; different manure rates: M0N2, M1N2, M2N2, and M3N2) was used in a greenhouse fertilization experiment. SSN and SRN increased with increasing N rate up to M3N2. SSON decreased with increasing manure rate and was the highest in the M1N2, whereas SMN and SRN were the highest in the M3N2, and increased with increasing manure rate on all sampling dates. Both SSN and SRN declined significantly with increasing soil depth in the different application rates of manure (p < .05). Moreover, the SSN and SRN significantly varied with plant growth and followed a different pattern during the growing season. SSN and FA peaked in the first ear fruit period, but SMBN was at its highest level in the second ear fruit period. There was a significant positive relationship (p < .05) between SSN and SRN throughout the plant growing season, and the annual apparent loss of N in the M3N3 was the highest. The combined application of inorganic N fertilizer and manure at an appropriate rate may be an effective strategy for maintaining the long-term health of greenhouses.
