Greenhouse Vegetable Systems Research Articles

Responses of Soil Macro-Porosity, Nutrient Concentrations and Stoichiometry Following Conversion of Rice–Wheat Rotation to Organic Greenhouse Vegetable System

Responses of Soil Macro-Porosity, Nutrient Concentrations and Stoichiometry Following Conversion of Rice–Wheat Rotation to Organic Greenhouse Vegetable System

Nitrogen fertilization affected microbial carbon use efficiency and microbial resource limitations via root exudates

Root exudation and its mediated nutrient cycling process driven by nitrogen (N) fertilizer can stimulate the plant availability of various soil nutrients, which is essential for microbial nutrient acquisition. However, the response of soil microbial resource limitations to long-term N fertilizer application rates in greenhouse vegetable systems has rarely been investigated. Therefore, we selected a 15-year greenhouse vegetable system, and investigated how N fertilizer application amount impacts on root carbon and nitrogen exudation rates, microbial resource limitations and microbial carbon use efficiency (CUEST). Four N treatments were determined: high (N3), medium (N2), low (N1), and a control without N fertilization (N0). Compared to the control (N0), the results showed that the root C exudation rates decreased significantly by 42.9 %, 57.3 % and 33.6 %, and the root N exudation rates decreased significantly by 29.7 %, 42.6 %, and 24.1 % under N1, N2, and N3 treatments, respectively. Interactions between fertilizer and plant roots altered microbial C, N, P limitations and CUEST; Microbial C and N/P limitations were positively correlated with root C and N exudation rates, negatively correlated with microbial CUEST. Random Forest analysis revealed that the root C and N exudation rates were key factors for soil microbial resource limitations and microbial CUEST. Through the structural equation model (SEM) analysis, soil NH4+ content had significant direct effects on the root exudation rates after long-term N fertilizer application. An increase in root exudation rates led to enhanced microbial resource limitations in the rhizosphere soils, potentially due to increased competition. This enhancement may reduce microbial carbon use efficiency (CUE), that is, microbial C turnover, thereby reducing soil C sequestration. Overall, this study highlights the critical role of root exudation rates in microbial resource limitations and CUE changes in plant-soil systems, and further improves our understanding of plant-microbial interactions.

Integrated Soil–Crop System Management Promotes Sustainability of Intensive Vegetable Production in Plastic Shed Systems: A Case Study in the Yangtze River Basin, China

Excessive fertilizer input, low nutrient use efficiency, soil quality, and environmental degradation hinder greenhouse vegetable production. Integrated agronomic strategies of soil, crop, and nutrient management are needed to sharply improve the vegetable yield and simultaneously maintain sustainable production. A three-season field experiment was conducted from 2015 to 2018, aiming to evaluate the effect of integrated soil–crop system management (ISSM) on the agronomy, environment, and economy of greenhouse vegetable systems in the Yangtze River Basin, China. Three treatments were included in the experiment: (1) farmers’ current practice (FP), based on a local farmers’ survey; (2) soil remediation treatment (SR), the application of soil conditioner and compost fertilizer instead of chicken manure; (3) ISSM, a combination of soil conditioner, reducing plant density, and using formula fertilizer as well as increasing the fertilization times. The results indicated that ISSM (47.7 Mg ha−1) improved the pepper yield by 17% relative to farmers’ current practice (FP, 40.7 Mg ha−1). Soil remediation (SR), as a single approach, mainly made a contribution to improving the yield (by 6.9%) and nutrient use efficiency while reducing apparent nitrogen (N) losses. Higher yields were mainly attributed to increasing the fruit number per plant. On average, apparent N losses were reduced by 245 kg N ha−1 per season for ISSM compared to FP. In addition, higher net profits were obtained under SR and ISSM relative to FP. Overall, both SR and ISSM have advantages for the agronomy, environment, and economy in greenhouse vegetable production, but ISSM would be the optimal choice to achieve higher yields with lower environmental impacts.

Microplastics affect the ecological stoichiometry of plant, soil and microbes in a greenhouse vegetable system

Microplastic (MP) pollution is a growing global issue due to its potential threat to ecosystem and human health. Low-density polyethylene (LDPE) MP is the most common type of plastics polluting agricultural soils, negatively affecting soil-microbial-plant systems. However, the effects of LDPE MPs on the carbon (C): nitrogen (N): phosphorus (P) of soil-microbial-plant systems have not been well elucidated. Thus, we conducted a pot experiment with varying LDPE MP concentrations (w/w) (control without MPs; 0.2 % MPs (PE1); 5 % MPs (PE2); and 10 % MPs (PE3)) to study their effects on soil-microbial-plant C-N-P stoichiometry. Soil C:N ratio increased 2.3 and 3.4 times in PE2 and PE3, respectively. Soil C:P ratio increased 2.2 and 3.6 times in PE2 and PE3, respectively. Soil microbial C:N ratios decreased by 46.2 % in PE1, while C:P ratios decreased by 59.2, 38.6, and 67.9 % in PE1, PE2, and PE3, respectively. Soil microbial N:P ratio decreased in PE1 (17.2) and PE3 (59.1 %). MPs increased shoot C content and C:N ratios, particularly at the 5 % MP addition rate. MP addition altered dissolved organic C, N, and P concentrations, depending on the MP addition rate. Microbial community responses to MP exposure were complex, leading to variable effects on different microbial groups at different MP addition rates. Structural equation modeling showed that MP addition had a direct positive effect (β = 0.96) on soil C-N-P stoichiometry and a direct negative effect (β = −1.34) on microbial C-N-P stoichiometry. These findings demonstrate the complex interactions between MPs, soil microorganisms, and nutrient dynamics, highlighting the need for further research to better understand the ecological implications of MP pollution in terrestrial ecosystems.

Effects of Different Irrigation and Fertilization Practices on Nitrogen Balance and Yield on Greenhouse Eggplant (Solanum melongen L.) in Mollisols

ABSTRACT Balancing the nitrogen (N) budgets of agricultural production is crucial to maintaining yield and reducing the environmental pollution, especially in vegetable systems. Here, a systematic study was conducted on eggplant (Solanum melongena L.) yield, N uptake, N leaching and N balance in response to regular fertilization and irrigation (WF), reducing 20% of chemical fertilizers (W + 80%F), reducing 20% of irrigation amount (80%W+F), and biochar addition (WF+B) in a greenhouse eggplant system in Northeastern China. The results showed that compared with WF, 80%W+F treatment decreased eggplant yield, N uptake and N leaching by 11%, 23% and 14%, respectively. However, it increased N surplus by 30%. W + 80%F not only decreased N surplus by 4% and improved N balance, but also maintained eggplant yield and N uptake. WF+B significantly increased eggplant yield and N uptake, however, it sharply increased N surplus by 141% and caused N imbalance. Therefore, these results demonstrated that reducing chemical fertilizers by 20% would be the most suitable management practice for maintaining eggplant yield and reducing N surplus in greenhouse vegetable systems.

Microbial mechanism of crop residues addition in nitrogen leaching loss retention and soil ecosystem stability maintenance

Over fertilization is the main factor in excessive N leaching (NL) loss in greenhouse vegetable cultivation systems. Adjusting the fertilizer application rate and returning plant residues effectively reduce NL. However, the microbial mechanism of crop residues addition in NL loss retention remains largely unknown. This study established a tomato-cultivating soil column experiment with different organic fertilizer addition treatments: no organic amendment (CK), chicken manure application (CM), chicken manure ＋rice husk (CMR), and chicken manure ＋maize straw (CMM) to further explore the discrepancies in the microbial community composition and the microbial co-occurrence network structure. The results revealed that CM produced the highest yield when provided with just enough nutrients for the crop requirements. The CMR yield decreased by 26.0%, while CMM remained at the same level as CK. Although discrepancies were evident between the decomposition characteristics and nutrient release rates of the rice husk and maize straw, no differences were apparent between the mineral NL loss retention of the two materials after one growing season, exhibiting a 47.8% and 50.4% reduction compared to CM. Furthermore, crop residues addition induced rapid microbial growth, increased the microbial community richness, and caused lignocellulose degraders accumulation, with fewer operational taxonomic units (OTUs) associated with the nitrification process. The CMM treatment produced a more robust and complex microbial co-occurrence network that was absent in the CM treatment. The results implied an alleviating effect of the straw amendment on mineral NL loss and emphasized the importance of readily available C sources in stabilizing an ecosystem.

Effects of long-term organic fertilizer substitutions on soil nitrous oxide emissions and nitrogen cycling gene abundance in a greenhouse vegetable field

Intensive vegetable fields, characterized by extremely high nitrogen (N) application rates, emit a large amount of the potent greenhouse gas nitrous oxide (N2O). Short-term substitution of organic fertilizers for chemical fertilizers may mitigate N2O emissions from vegetable fields. However, the long-term impacts, particularly on soil background N2O emissions (excluding effects caused by newly applied fertilizers) in vegetable fields, remain poorly elucidated. Thus, we conducted an 11-year experiment to investigate the long-term fertilization effects on soil background N2O emissions and the abundance of N-cycling genes in a greenhouse vegetable field. The soil capacity for potential denitrification activity (PDA) was further measured to evaluate denitrification potential. The field experiment comprised of four treatments: no fertilization (control, CK), only chemical N fertilizers (CF), 50 % of chemical N fertilizers substituted by organic fertilizers (OL), and 87.5 % of chemical fertilizers substituted by organic fertilizers (OH). The long-term application of chemical fertilizers alone (CF) and organic fertilizer substitutions (OL and OH) increased soil background N2O emissions 30-fold and 10-fold, respectively, with average N2O fluxes of 1.2 ± 3.8, 33.8 ± 5.1, 9.4 ± 2.3 and 10.2 ± 2.7 μg N2O-N m−2 h−1 in the CK, CF, OL and OH treatment, respectively. The CF treatment significantly decreased the abundance of AOA amoA, nirS and nosZ genes, while both the OL and OH treatments increased the abundance of AOB amoA, and the OH treatment also increased nosZ gene abundance. Soil pH was a key determinant of the contrasting responses of N-cycling genes to different fertilizer types. Compared with low fertilizer substitutions (OL), high organic fertilizer substitutions (OH) did not result in more soil background N2O emissions, despite higher potential denitrification activities and soil total N contents. This was due to increased abundance of nosZ gene and likely enhanced N2O consumption activities. Soil NO3−-N concentrations, soil pH, and the abundance of nosZ gene were three main factors in controlling the responses of soil background N2O emissions to long-term fertilization. Overall, this study suggests that in the long-term perspective organic fertilizer substitution is a beneficial practice to mitigate N2O emissions from intensive greenhouse vegetable cropping systems.

Is sorghum a promising summer catch crop for reducing nitrate accumulation and enhancing eggplant yield in intensive greenhouse vegetable systems?

Is sorghum a promising summer catch crop for reducing nitrate accumulation and enhancing eggplant yield in intensive greenhouse vegetable systems?

Aerated drip irrigation improves water and nitrogen uptake efficiencies of tomato roots with associated changes in the antioxidant system

• After aerated drip irrigation, soil oxygen content significantly increased. • The duration and sequence of aeration changed the root antioxidant system. • The root antioxidant system correlated root morphology of tomato. • Root antioxidant systems and growth affect water and nitrogen uptake efficiency of tomato. China has the largest area of vegetable cultivation in greenhouse vegetable system in the world. However, the excessive application of irrigation and fertilizers has caused soil degradation and hardening, even leading to injury and yield loss in vegetable. Increasing soil aeration oxygen can improve crop water and nutrient uptake efficiencies. However, its effects on crop antioxidant systems are less known. Due to the sensitivity of the antioxidant system to changes in soil oxygen content, it is expected that aerated drip irrigation (ADI) delivering microbubble water to the crop rhizosphere will alter root antioxidant enzyme activities, malondialdehyde (MDA) content, and osmotic regulators in tomato plants. We conducted pot experiments under eight irrigation regimes: five aerated durations (0%, 25%, 50%, 75%, and 100%) of the subsurface drip irrigation period aerated (CK, A 25% , A 50% , A 75% , and A), with two aerated sequences (L: subsurface drip irrigation follow by aerated drip irrigation, F: aerated drip irrigation follow by subsurface drip irrigation) for the A 25% , A 50% and A 75% treatments. All treatments with ADI had an average of 7.63% higher oxygen concentration (OC) than the CK treatment at 74 d after transplanting. The principal component analysis revealed that MDA of all treatments had the greatest effect on the antioxidant system, while aerated drip irrigation reduced MDA content. Increasing aeration duration from A 25% to A 75% significantly affected antioxidant enzyme activities and root growth parameters, and the L treatment had higher values than the F treatment. The L -A 75% treatment had the highest water use efficiency, nitrogen uptake efficiency, and yield. The structural equation model demonstrated that ADI indirectly promotes tomato water and nitrogen uptake efficiencies by affecting the antioxidant system and root growth.

Manure properties, soil conditions and managerial factors regulate greenhouse vegetable yield with organic fertilizer application across China.

To better understand the responses of vegetable yields in a greenhouse system to organic fertilizer through a quantitative evaluation based on peer-reviewed journal articles and in consideration of environmental managerial factors. We conducted a meta-analysis of 453 paired observations from 68 peer-reviewed journal articles to assess the response of vegetable yields in greenhouse vegetable systems in China to organic fertilization. Compared with the control (no organic fertilizer), organic fertilization significantly increased the yields of vegetables by 44.11% on average. The response of vegetable yields to organic fertilizer tended to increase with the increasing experimental duration. Organic fertilizer application had the greatest potential for leafy vegetables (+76.44%), in loamy soils (+53.94%), at moderate organic fertilizer carbon input levels (+54.13%), and in soils with moderate initial soil total nitrogen levels (+50.89%). Aggregated boosted tree analysis indicated that organic fertilizer carbon inputs, vegetable type and experimental duration were the predominant factors that manipulated the response of vegetable yields to organic fertilizer application. The rational application of farmyard manure would be a promising strategy for increasing vegetable yields in greenhouse vegetable systems in China. Factoring in vegetable type, carbon and nitrogen inputs of organic fertilizer, and soil texture would benefit vegetable yields with the application of organic fertilizer.

Biochar-Induced Mitigation Potential of Greenhouse Gas Emissions Was Enhanced under High Soil Nitrogen Availability in Intensively-Irrigated Vegetable Cropping Systems

Intensive irrigation coupled with excessive nitrogen (N) fertilizer input has resulted in high soil greenhouse gas (GHG) emissions in vegetable cropping systems. Biochar as a soil amendment has been advocated as a desirable option to reduce GHG emissions in agricultural systems, but its interactive effects with soil N availability in vegetable systems have yet to be clarified. We performed a field study to examine how biochar interacts with N fertilizer in driving annual methane (CH4) and nitrous oxide (N2O) emissions from an intensively-irrigated greenhouse vegetable cropping system acting as both sources of atmospheric CH4 and N2O in subtropical China. Biochar amendment significantly increased soil CH4 emissions by 33% and 85%, while it decreased soil N2O emissions by 22% and 12% with and without N fertilizer input, respectively. Fertilizer N combination weakened the positive response of CH4 to biochar while it enhanced the mitigation potential of biochar for N2O. Annual direct emission factors of fertilizer N for N2O were estimated to be 1.35% and 1.94% for the fields with and without biochar amendment, respectively. Annual flux-sustained global warming potential (SGWP) and greenhouse gas intensity (GHGI) were significantly decreased by biochar amendment, and this mitigation effect was enhanced with fertilizer N combination. Altogether, we highlight that biochar can reconcile higher yield and lower climatic impact in intensive vegetable cropping systems in subtropical China, particularly in vegetable soils with high N availability.

Optimized fertigation mitigates N2O and NO emissions and enhances NH3 volatilizations in an intensified greenhouse vegetable system

Gaseous reactive nitrogen (GNr) losses (N2O, NO emissions and NH3 volatilization, etc.) in greenhouse vegetable fields (GVF) have received considerable critical attention. Much uncertainty still exists about GNr losses reduction under increasing vegetables demand and environmental policies in China. An experiment spanning four greenhouse vegetable growing seasons (cucumber and tomato) was conducted in North China Plain (NCP). It included four treatments, i.e., flood irrigation with no urea-N application (FU0), flood irrigation with conventional urea-N application (FUN), drip fertigation with conventional urea-N application (DUN), and drip fertigation with 50% reduction of urea-N application (DRUN). Obvious emission peaks of N2O, NO and NH3 flux were captured in the GVF after each fertilization and irrigation event. For FUN treatment, the mean annual area-scaled emissions of N2O, NO, and NH3 were 11.48, 1.66, and 44.90 kg N ha−1 yr−1, respectively; and the mean annual yield-scaled emissions of N2O, NO, and NH3 were 181.86, 23.04, and 800.07 g N t−1 yr−1, respectively. On the mean annual area-scaled and yield-scaled, the N2O emissions were significantly (P < 0.05) lower by 40.1 % and 32.3 %, and the NO emissions were lower by 23.5 % and 28.5 %, but the NH3 volatilization were significantly (P < 0.05) higher by 31.7 % and 49.0 %, respectively, for the DUN treatment than FUN. Also compared with FUN, in DRUN treatment, the mean annual area-scaled N2O emissions, NO emissions and NH3 volatilization were significantly reduced by 46.7 %, 52.4 % and 22.0 %, respectively; and the mean annual yield-scaled N2O emissions, NO emissions and NH3 volatilization were significantly reduced by 40.7 %, 57.1 % and 24.5 %, respectively. Moreover, compared with FUN treatment, DUN and DRUN treatment both alleviated the global temperature potential (GTP) at 20- and 100-year timescales. Overall, compared with conventional water and fertilizer regimes, only changing irrigation mode reduced N2O and NO emissions but increased NH3 volatilization losses in greenhouse cucumber-tomato cultivation system; reducing N application while changing irrigation methods had significant emission reduction effects on N2O, NO and NH3 at both the area-scaled and yield-scaled, and which is an effective water and fertilizer managements for greenhouse cucumber-tomato cultivation system.

Magnesium Fertilizer Application and Soil Warming Increases Tomato Yield by Increasing Magnesium Uptake under PE-Film Covered Greenhouse

Magnesium (Mg) plays an important role in numerous physiological and biochemical processes in plants. However, Mg deficiency is common worldwide, especially in greenhouse vegetable systems, due to the overuse or misuse of fertilizers. This study investigated the effects of different Mg application strategies in alleviating Mg deficiency of tomatoes in PE-film covered greenhouse. Six field treatments were used: conventional fertilization practice (C), conventional fertilization + soil warming (CW), conventional fertilization + Mg applied to soil (C + MgS), conventional fertilization + Mg applied as foliar application (C + MgF), conventional fertilization + Mg applied to soil and foliar application (C + MgSF), and conventional fertilization + Mg applied to soil and foliar application with soil warming (C + MgSFW). Foliar spray of Mg fertilizer (C + MgF, C + MgSF, and C + MgSFW) increased the total Mg uptake and Mg content of functional leaves in both winter-spring and autumn-winter seasons. Soil warming treatments (CW and C + MgSFW) were also beneficial for Mg uptake and chlorophyll biosynthesis compared with no-warming treatments (C and C + MgSF), especially in autumn-winter season. Additionally, Mg fertilizer application and soil warming increased tomato yields; the C + MgSFW treatment had the highest increase in yields compared with the C treatment. Therefore, foliar Mg fertilizer application combined with soil warming, while considering seasonal variation, is feasible for reducing Mg deficiency in tomatoes under PE-film covered greenhouse vegetable systems.

Annual NO and N

Context Overuse of N fertiliser in vegetable cropping systems is known to release of nitric and nitrous oxide to the atmosphere in China. Optimisation of N fertilisation regimes has the potential to mitigate NO and N2O emissions from these N-rich systems. Aims We investigated the effects of different N fertilisation regimes on NO and N2O emissions, and vegetable yields, with particular efforts to estimate annual direct emission factors of NO and N2O under different N fertilisation regimes in greenhouse vegetable fields. Methods Annual NO and N2O fluxes were taken simultaneously using the static chamber-based method from a greenhouse vegetable system in south-east China with four N fertiliser treatments: (1) no N fertiliser (control); (2) chemical N fertiliser application (CF); (3) organic N fertiliser application (OF); and (4) organic-chemical mixed N fertiliser application (MF). Key results N fertilisers significantly increased NO and N2O emissions. Direct emission factors of N fertiliser for NO and N2O were the largest for MF, with an average of 0.99% and 0.67%, respectively. Vegetable yields were only significantly enhanced under OF treatment. Conclusions Relative to the use of chemical N fertiliser, the application of organic-chemical mixed N fertiliser showed not to be effective for mitigating NO and N2O emissions. Instead, sole application of organic N fertiliser was a viable option to enhance vegetable yields but without increasing NO and N2O emissions in greenhouse vegetable systems. Implications Substituting the use of chemical N fertiliser with organic N fertiliser input could benefitvegetable production but without stimulating NO and N2O emissions from vegetable cropping systems in sub-tropical China.

Biostimulants decreased nitrogen leaching and NH3 volatilization but increased N2O emission from plastic-shed greenhouse vegetable soil

Biostimulant application is an effective strategy to enhance soil fertility and plant growth. However, its comprehensive impacts on nitrogen (N) uptake and reactive N (Nr) losses via leaching, ammonia (NH3) volatilization, and nitrous oxide (N2O) emission from plastic-shed greenhouse vegetable system are still little known. Therefore, a field experiment was conducted with cauliflower-tomato growth rotation (from September 6, 2018, to July 17, 2019) receiving three biostimulants, i.e., humic acid (HA), algae extract (AE), and chitosan (CT), as well as a control without stimulant. The cumulative Nr losses over the cauliflower-tomato growth cycle via leaching, NH3 volatilization, and N2O emission were 104-175 kg N ha-1, 2.32-3.85 kg N ha-1, and 0.70-0.85 kg N ha-1, respectively. Biostimulant application significantly (P < 0.05) retarded the total N leaching by 17-44% in tomato season, while suppressed the NH3 volatilization by 18-38% in cauliflower season. Overall, AE showed the best inhibition efficiency on Nr losses by significantly (P < 0.05) decreasing total N leaching and NH3 volatilization by 36-44% and 38-52% in both vegetable seasons, compare to the control. However, all three biostimulants stimulated the N2O emission under both vegetable cycles. Interestingly, all biostimulant-added treatments promote the cauliflower and tomato yield, particularly following the HA and AE amendments, which bring local farmers approximately 4,384-10,035 yuan RMB ha-1 more income. Enhanced yield under biostimulant treatments was due to higher N uptake capacity and enhanced root morphology. In summary, biostimulants have a contrasting influence on three major Nr lost pathways in greenhouse vegetable production. We recommend that AE is the most optimal biostimulant as it increases vegetable yield and decreases total N leaching and NH3 volatilization while not dramatically increase the N2O emission.

Global greenhouse vegetable production systems are hotspots of soil N2O emissions and nitrogen leaching: A meta-analysis.

Vegetable production in greenhouses is often associated with the use of excessive amounts of nitrogen (N) fertilizers, low NUE (15-35%), and high N losses along gaseous and hydrological pathways. In this meta-analysis, we assess the effects of application rate, fertilizer type, irrigation, and soil properties on soil N2O emissions and nitrogen leaching from greenhouse vegetable systems on the basis of 75 studies. Mean±standard error (SE) N2O emissions from unfertilized control plots (N2Ocontrol) and N leaching (NLcontrol) of greenhouse vegetable systems were 3.2±0.4 and 91±20kgN ha-1 yr-1, respectively, indicating legacy effects due to fertilization in preceding crop seasons. Soil organic carbon concentrations (SOC) and irrigation were significantly positively correlated with NLcontrol losses, while other soil properties did not significantly affect N2Ocontrol or NLcontrol. The annual mean soil N2O emission from fertilized greenhouse vegetable systems was 12.0±1.0kg N2O-N ha-1 yr-1 (global: 0.067Tg N2O-N yr-1), with N2O emissions increasing exponentially with fertilization. The mean EFN2O was 0.85%. The mean annual nitrogen leaching (NL) was 297±22kgN ha-1 yr-1 (global: 1.66TgN yr-1), with fertilization, irrigation, and SOC explaining 65% of the observed variation. The mean leaching factor across all fertilizer types was 11.9%, but 18.7% for chemical fertilizer. Crop NUE was highest, while N2O emissions and N leaching were lowest, at fertilizer rates <500kgN ha-1 year-1. Yield-scaled N2O emissions (0.05±0.01kg N2O-N Mg-1 yr-1) and nitrogen leaching (0.79±0.08kgN Mg-1 yr-1) were lowest at fertilizer rates <1000kgN ha-1 yr-1. Vegetables are increasingly produced in greenhouses, often under management schemes of extreme fertilization (>1500kgN ha-1 yr-1) and irrigation (>1200mm yr-1). Our study indicates that high environmental N2O and N leaching losses can be mitigated by reducing fertilization rates to 500-1000kgN ha-1 yr-1 (mean: ∼762kgN ha-1 yr-1) without jeopardizing yields.

Assessing impacts of nitrogen management on nitrous oxide emissions and nitrate leaching from greenhouse vegetable systems using a biogeochemical model

Greenhouse vegetable (GV) fields with intensive nitrogen application and frequent flood irrigation may substantially contribute to reactive nitrogen (Nr) losses, such as nitrous oxide (N2O) emissions and nitrate (NO3−) leaching. In this study, we applied a biogeochemical model, Denitrification-Decomposition (DNDC), to assess impacts of N management on vegetable yields, N2O emissions, and NO3−-N leaching from GV systems. The model was evaluated using multi-year (2011–2013) field measurements of vegetable yields, N2O emissions, and NO3−-N concentrations in the surface soil layer and soil leachate under three treatments with different N management. The model evaluations demonstrated that the simulations of the vegetable yields and seasonal cumulative N2O emissions were consistent with the corresponding observations after calibration. In addition, DNDC generally captured the seasonal variations of the N2O fluxes and NO3−-N concentrations in the surface soil layer and the seasonal patterns and magnitudes of the measured NO3−-N concentrations in soil leachate in 2011. We then assessed impacts on the vegetable yields, N2O emissions, and NO3−-N leaching of different N management practices by conducting simulations under scenarios with changes in rate of the applied N-fertilizers and the application of nitrification inhibitor (NI). The results suggested that 1) the increasing of organic or synthetic N application rate generally increased the N2O emissions and NO3−-N leaching, but did not persistently increase the vegetable yields, 2) urea N application could induce more N2O emissions and NO3−-N leaching in comparison with organic N amendment, and 3) the NI application could decrease the N2O emissions and NO3−-N leaching while maintaining the vegetable yields at the GV fields. The optimum management practice identified in this study was applying organic manure at a rate of 320 kg N ha−1 four season−1 and urea at a rate of 334 kg N ha−1 four season−1, combined with the NI application. The optimum management practice reduced the rates of organic manure (1600 kg N ha−1 four season−1) and urea (1670 kg N ha−1 four season−1) under the farm's conventional practice by 80%. This practice maintained or slightly increased the yields and mitigated the N2O emissions and NO3−-N leaching by 81% to 90% and 92% to 95%, respectively, among different vegetable growing seasons.

Nitrogen use efficiency, crop water productivity and nitrous oxide emissions from Chinese greenhouse vegetables: A meta-analysis

Greenhouse vegetable cultivation is a substantial source of nitrous oxide (N2O) emissions in China due to intensive managements with nitrogen (N) fertilizers and irrigation water. We hypothesize that reducing input rates of N fertilizers or irrigation water to optimal levels would mitigate N2O emissions without significant loss of vegetable yields. The primary aims of this study are to (i) quantify the variations in vegetable yields, N2O emissions, nitrogen use efficiency (NUE) and crop water productivity (CWP) under greenhouse cultivation conditions; (ii) determine the major regulating factors of vegetable yields, N2O emissions, emission factors (EFs), yield-scaled N2O emissions, NUEs and CWPs; and (iii) evaluate the effectiveness of fertilization and irrigation strategies for N2O mitigation. We compiled a comprehensive dataset from 44 peer-reviewed publications, which includes 408 determinations of seasonal N2O emissions from greenhouse vegetable systems across China between 2006 and 2019. An emission coefficient of 0.95% was obtained as the slope of the linear regression between N2O emissions against N input rates (r2 = 0.480, n = 322, p < 0.001) for treatments that were unfertilized and fertilized with conventional fertilizers. For fruit vegetables, N2O emissions responded to NUEs following a linear-plateau model (r2 = 0.539, n = 115, p < 0.001), which suggests that management practices aiming to increase NUEs are effective for decreasing N2O emissions at NUEs below 0.15 t kg−1. The results of meta-analyses revealed that applications of biochar or enhanced efficiency fertilizers (EEFs) decreased EFs and yield-scaled N2O emissions (ranging from −42% to −34%) but did not significantly increase NUEs. Reducing the input rates of N fertilizers (approximately 50% of the total N input) or irrigation water (approximately 20% of the full irrigation water) provided advantages for maintaining vegetable yields (ranging from −7% to 3%), decreasing N2O emissions (ranging from −68% to −59%), increasing NUEs (ranging from 76% to 157%), and subsequently reducing the reactive N released into the environment.

Integrated systematic approach increase greenhouse tomato yield and reduce environmental losses

High input - high output greenhouse vegetable systems are responsible for nutrient surpluses and environmental losses. Integrated strategies that improve soil, crop and nutrient management are needed to ensure more sustainable production systems. We conducted a two-year field experiment to evaluate the potential of integrated soil-crop system management (ISSM) practices to improve the productivity and environmental outcomes from an intensive greenhouse tomato production system in the Yangtze River Basin, China. Four treatments were tested: i) farmers' practice (FP); ii) soil remediation (SR), where lime nitrogen with compost addition was the only management strategy; iii) a treatment that combined soil remediation with optimized crop planting density (SRCO), which increased planting density for improving crop yield; and iv) integrated soil-crop system management (ISSM), as a systematic integrated approach, which included the combined optimization of soil remediation, crop optimization, and nutrient management. In the integrated soil-crop system management treatment, nutrient management was optimized through adoption of the most appropriate type (formula) of fertilizer for the crop, rate and application timing of synthetic fertilizer, and by substituting poultry manure with compost. Our results indicated that the fruit yield of the integrated soil-crop system management treatment was 104 t ha−1, 13.4%–37.3% higher than that of the other three treatments. The mean reactive nitrogen loss (81.1 kg N ha−1) and the greenhouse gas emissions (6495 kg CO2-eq ha−1) in the farmers' practice treatment were much higher than in the other three treatments (reactive nitrogen loss: 47.9–54.3 kg N ha−1; and greenhouse gas emissions: 4926–5468 kg CO2-eq ha−1, respectively). The mean nitrogen and carbon footprints of the integrated soil-crop system management treatment were significantly lower than those of other treatments, as a result of both the lower fertilizer nitrogen use and the greater yield. This study indicates that integrated soil-crop system management could produce greater yields and increase net profit with reduced nitrogen inputs, whilst reducing the environmental cost associated with conventional farmers’ practice in plastic-greenhouse vegetable production systems.

Changes in soil physical and chemical characteristics in intensively cultivated greenhouse vegetable fields in North China

The total area of greenhouse crop production is increasing in China. However, this adversely influences soil physical and chemical properties due to special environmental conditions and agricultural management in greenhouse production. In this study, we evaluated soil properties of greenhouse vegetable systems with different planting years, a long-term greenhouse strawberry system, and an open-field wheat-maize rotation system in a typical agricultural production area of North China. The annual fertilizer application rates of nitrogen (N), phosphorus (P), and potassium (K) in the greenhouse vegetable system were 842.15, 809.14, and 931.55 kg ha−1, respectively, which were 3 times more than those in the wheat-maize rotation system and led to great changes of soil properties. Bulk density and soil pH gradually declined with increased cultivation time from new to 15 years in the greenhouse vegetable system. Bulk density declined from 1.58 g/cm3 in the new greenhouse fields to 1.25 g/cm3 in the 15-year greenhouse fields, and pH decreased from 5.72 to 4.55 with a rate of 0.08 unit per year. The contents of soil organic carbon (SOC), soil soluble salts, total NPK, and available NPK rose steadily until the 10th or 11th year, then decreased. By comparison with another two cropping systems, the greenhouse vegetable fields showed the lowest bulk density and pH, but the highest contents of SOC, soil soluble salts, total NPK, and available NPK due to heavy fertilizer inputs. The contents of soil N, P, and K in greenhouse vegetable fields were imbalanced, as indicated by C:N (11.58), C:P (16.06), and N:P (1.71) molar ratios in soils, which were significantly lower than the level in China and the rest of the world. In addition, the C:P and N:P ratios of greenhouse vegetable fields were also lower than those of wheat-maize rotation fields and greenhouse strawberry fields. Regression analysis indicated that the contents of SOC and soluble salts were positively correlated with pH, while available N and P contents showed negative linear relationships. These results demonstrate dramatic adverse changes of soil properties in intensive greenhouse vegetable fields in China. Our results also emphasize the need to regulate appropriate fertilizer application for intensive greenhouse vegetable management.