Greenhouse Vegetable Production Systems Research Articles

In situ 15N labeling reveals high soil N2 emission during anaerobic soil disinfestation period in a greenhouse vegetable production system

In situ 15N labeling reveals high soil N2 emission during anaerobic soil disinfestation period in a greenhouse vegetable production system

Towards Sustainable Productivity of Greenhouse Vegetable Soils: Limiting Factors and Mitigation Strategies.

Greenhouse vegetable production has become increasingly important in meeting the increasing global food demand. Yet, it faces severe challenges in terms of how to maintain soil productivity from a long-term perspective. This review discusses the main soil productivity limiting factors for vegetables grown in greenhouses and identifies strategies that attempt to overcome these limitations. The main processes leading to soil degradation include physical (e.g., compaction), chemical (e.g., salinization, acidification, and nutrient imbalances), and biological factors (e.g., biodiversity reduction and pathogen buildup). These processes are often favored by intensive greenhouse cultivation. Mitigation strategies involve managing soil organic matter and mineral nutrients and adopting crop rotation. Future research should focus on precisely balancing soil nutrient supply with vegetable crop demands throughout their life cycle and using targeted organic amendments to manage specific soil properties. To ensure the successful adoption of recommended strategies, socioeconomic considerations are also necessary. Future empirical research is required to adapt socioeconomic frameworks, such as Science and Technology Backyard 2.0, from cereal production systems to greenhouse vegetable production systems. Addressing these issues will enable the productivity of greenhouse vegetable soils that meet growing vegetable demand to be sustained using limited soil resources.

Modeling Nitrogen Fate and Water and Nitrogen Use Efficiencies under Different Greenhouse Vegetable Production Systems Using the WHCNS-Veg Model.

Quantitative evaluation of the effects of diverse greenhouse vegetable production systems (GVPS) on vegetable yield, soil water consumption, and nitrogen (N) fates could provide a scientific basis for identifying optimum water and fertilizer management practices for GVPS. This research was conducted from 2013 to 2015 in a greenhouse vegetable field in Quzhou County, North China. Three production systems were designed: conventional (CON), integrated (INT), and organic (ORG) systems. The WHCNS-Veg model was employed for simulating vegetable growth, water dynamics, and fates of N, as well as water and N use efficiencies (WUE and NUE) for four continuous growing seasons. The simulation results revealed that nitrate leaching and gaseous N emissions constituted the predominant N loss within GVPS, which separately accounted for 11.5-59.4% and 6.0-21.1% of the N outputs. The order of vegetable yield, N uptake, WUE, and NUE under different production systems was ORG > INT > CON, while the order of nitrate leaching and gaseous N loss was CON > INT > ORG. Compared to CON, ORG exhibited a significant increase in yield, N uptake, WUE, and NUE by 24.6%, 24.2%, 26.1%, and 89.7%, respectively, alongside notable reductions in nitrate leaching and gaseous N loss by 67.7% and 63.2%, respectively. The ORG system should be recommended to local farmers.

High soil nitrous oxide emissions from a greenhouse vegetable production system in Shouguang, Northern China

In China, the area of greenhouse vegetable production (GVP) has exceeded 4 million ha, accounting for >80% of global GVP systems. Excessive nitrogen (N) fertilization and frequent irrigation have created GVP hotspots of nitrous oxide (N2O) emissions. There are several studies on soil N2O emissions from GVP systems, but all with low-frequency manual sampling, which may have resulted in large uncertainties regarding quantifying N2O emissions. Herein, we utilized an automatic chamber system equipped with 16 channels to measure N2O emissions under common farm practice from a GVP system in Shouguang, Northern China. We measured emissions from both furrows and ridges for 1 year from July 2020 to July 2021. Our continuous monitoring showed that the annual soil N2O emission was 102 kg N ha−1, accounting for 7.6% of the applied N (1338 kg N ha−1). The annual N2O emission from furrows (176 kg N ha−1) was significantly higher than that from ridges (28 kg N ha−1). Large spatial variations in the N2O emissions were observed, ranging from 102 to 273 kg N ha−1 yr−1 for furrows (n = 8) and from 19 to 45 kg N ha−1 yr−1 for ridges (n = 7). In addition, we found that irrigation caused N2O flux pulses from furrows, increasing by 12–396% compared with the level before irrigation. High-frequency measurements using our automatic chamber system provided detailed information on the diurnal and seasonal dynamics of N2O emissions, which could be useful for building more accurate models and developing more effective policies to reduce N2O emissions from global GVP systems.

Leaching and fractionation of phosphorus in intensive greenhouse vegetable production soils.

Greenhouse vegetable production systems use excessive phosphorus (P) fertilizer. This study is set out to look into the P fractionation, mobility, and risk of P leaching in ten greenhouse soils. The mean P concentrations in leachates varied from 0.4 to 1.6 mg l-1 (mean of 30 days of soil leaching). Between 5.7 and 31.0 mg kg-1 of P was leached from soils during 30 days of column leaching. Organic matter (OM) and Olsen-extractable P (Olsen P) correlated strongly with cumulative P leached after 5, 10, 15, 20, 25, and 30 days of leaching. The high correlation between OM and Olsen P with cumulative P leached at 5 days of leaching suggests that in future leaching experiments, the leaching period should be extended to 5 days of leaching. The first two P fractions correlated significantly with the total P leached in the primary days of leaching. The pH had little effect on P leaching but had a significant impact on soluble and exchangeable P fraction, suggesting that P mobility would increase in these calcareous greenhouse vegetable soils as pH rose. The calculated change point (194 mg kg-1) was high, indicating that a high percentage (40%) of the studied greenhouse soils had exceeded the change point. In conclusion, due to the high degree of P saturation and change point in greenhouse vegetable soils, P mobilization is a significant risk, and the findings can be used to provide future direction for fertilizing greenhouse vegetable soils.

Assessing the environmental sustainability of different soil disinfestation methods used in solar greenhouse vegetable production systems

Overuse of fertilizers and irrigation and continuous monocropping is increasingly jeopardizing vegetable production in solar greenhouses as it causes serious soil degradation and the spread of soil-borne diseases. As a countermeasure, the practice of anaerobic soil disinfestation (ASD) has been recently introduced, which is carried out during the summer fallow period. However, ASD may increase N leaching and greenhouse gas (GHG) emissions when large amounts of chicken manure are applied. This study assesses how the use of different amounts of chicken manure (CM) combined with rice shells (RS) or maize straw (MS) affects soil O2 availability, N leaching, and GHG emissions during and following the ASD period. Application of RS or MS alone effectively stimulated long-lasting soil anaerobiosis without major stimulating effects on N2O emissions and N leaching. Seasonal N leaching and N2O emissions were in the ranges of 144–306 and 3–44 kg N ha−1, respectively, and were strongly increasing with increasing rates of manure application. Combining high rates of manure application with the additional incorporation of crop residues further increased N2O emissions by 56 %–90 % as compared to the standard practice of farmers (1200 kg N ha−1 CM). About 56 %–91 % of seasonal N2O emissions occurred during the ASD period, whereas N leaching mainly occurred in the cropping period (75 %–100 %). Our study shows, that for priming ASD incorporation of crop residue is sufficient and that the addition of chicken manure for ASD is not needed and should be reduced or even prohibited as it does not improve yields but stimulates the emission of the strong GHG N2O.

Phosphorus Leaching Alleviated by Organic Carbon in Greenhouse Vegetable Production System

Phosphorus Leaching Alleviated by Organic Carbon in Greenhouse Vegetable Production System

Drip fertigation with straw incorporation promotes soil microbial network complexity and potentially reduces pathogen abundance in greenhouse vegetable production systems

Continuous monoculture, conventional flood fertigation and low soil fertility increase the risk of soil-borne diseases in greenhouse vegetable production systems. Drip fertigation with straw incorporation (DIF+S) significantly improves resource use efficiency and reduces environmental risks compared to conventional fertigation. However, it remains unclear whether DIF+S positively affects soil microbial diversity and community structure and reduces the occurrence of soil-borne diseases. Therefore, a two-factor field trial was conducted in a greenhouse tomato production system with drip vs. flood fertigation, with and without straw incorporation across the seven growing seasons. The experimental treatments were as follows: (i) conventional flood irrigation with overfertilization (CIF); (ii) CIF + straw incorporation; (iii) drip fertigation with reduced irrigation and fertilization (DIF); and (iv) DIF + straw incorporation. Across the seven growing seasons, the average water and nitrogen use efficiency (WUE and NUE) was two- and threefold higher for DIF than for CIF, respectively, whereas tomato yields remained high. DIF significantly increased soil bacterial diversity and network complexity compared to CIF but had no effect on the soil fungal community. DIF significantly reduced the relative abundance of Fusarium-induced tomato wilt. Moreover, straw application significantly decreased fungal diversity while increasing fungal network complexity, although no effect on the bacterial community was found. The relative abundance of plant pathogens, such as Cladosporium, Fusarium and Alternaria, which are related to soil-borne diseases of tomato plants, was significantly reduced when straw was incorporated. Our results highlight that drip fertigation combined with straw incorporation significantly positively affects soil microbial diversity and stability. Thus, DIF+S is a sustainable and effective technology for maintaining soil health and reducing pesticide use in greenhouse vegetable production systems.

Organic farming decreases nitrate leaching but increases dissolved organic nitrogen leaching in greenhouse vegetable production systems

Organic farming decreases nitrate leaching but increases dissolved organic nitrogen leaching in greenhouse vegetable production systems

WHCNS-Veg Modelling of N2O, NH3 and NO3− Dynamics in a Vegetable Production System under Different Fertilization and Irrigation Regimes

Greenhouse vegetable production in China not only increases farmers’ income, but also increases the risk of nitrogen losses due to excessive water and fertilizer input. Nitrogen losses, including the potent greenhouse gas nitrous oxide (N2O), are driven by water content, soil temperature and pH; regulated by available organic carbon and inorganic nitrogen (N); and affected by management. Therefore, a process-based model was applied to explain the complex interaction of the factors affecting N losses in the form of N2O, NH3 and NO3− from a greenhouse vegetable production system in a northeast suburb of Beijing, China. We designed four treatments: two equal N input treatments with one flooding (FP) and the other drip irrigation (FPD) and two equal water input treatments (drip irrigation) with one 100% chemical N input (FPD) and the other 50% N input (OPTD). The last one was CK treatment (flooding without chemical N). We calibrated the WHCNS-veg model using year-round measurements of soil temperature, N2O emission, NH3volatilization, NO3− distribution and yields for greenhouse cucumber–tomato cultivation under farmers’ practice (flooding + 100% chemical N, FP). Then, we validated the model using the data sets under drip irrigation (70% of flooding amount + 100% chemical N, FPD), reduced chemical N by 50% (drip + 50% chemical N, OPTD) and CK treatment. The WHCNS-veg model was able to capture the above processes under different treatments. Annual N2O emissions were 5.47 and 3.76kg N ha−1 for the cucumber and tomato seasons under FP, respectively. Compared to FP, drip irrigation (FPD) decreased N2O emissions by 19.0% and 45.5% in the two seasons, respectively. Compared to FPD, applying a lower rate of N (OPTD) further reduced N2O emissions by 13.7% and 40.5%, respectively. According to the model simulation, N2O emission was mainly controlled by nitrification/denitrification in the cucumber/tomato seasons, respectively. Compared to FP, drip irrigation (FPD) increased NH3 volatilization by 54.2% in the cucumber season, while in the tomato season, there were no significant differences inNH3 volatilization under the three fertilizer treatments. The nitrate leaching levels were 48.5 and 81.0 kg N ha−1 for the two seasons under FP treatment. Drip irrigation (FPD) decreased NO3− leaching by 20.6% in the cucumber season. Drip irrigation (FPD) and/or reducing chemical N (OPTD) did not compromise vegetable yields. In all, WHCNS-veg performed well in simulating N2O, NH3 and NO3− dynamics from the greenhouse vegetable field, which means that the model can be used to manage water and nitrogen precisely in greenhouse vegetable production systems by scenario analysis, and drip irrigation and/or lower N input can be applied in this area to secure yield and reduce N losses.

Flavonoid-producing tomato plants have a direct negative effect on the zoophytophagous biological control agent Orius sauteri.

Orius sauteri (Poppius) (Hemiptera: Anthocoridae) is often used for biological control of small arthropod pests in greenhouse vegetable production systems in Asia. In addition to feeding on arthropod prey, O. sauteri consumes small quantities of plant material. Previous studies demonstrated that tomato plant chemistry confers antixenosis resistance to phloem-feeding whiteflies, but the potential nontarget effects of phytochemicals on the beneficial predator O. sauteri are unknown. Comparison of O. sauteri confined to near-isogenic lines (NILs) of tomatoes producing high levels of flavonoids (NIL-purple hypocotyl; resistant to whiteflies) and low levels of flavonoids (NIL-green hypocotyl; susceptible to whiteflies) revealed that O. sauteri had reduced oviposition, nymphal survival, and development on resistant plants, even if they were also provided with prey that did not feed on the host plant. Moreover, O. sauteri showed a significant ovipositional preference in choice assays, laying significantly more eggs on susceptible than on resistant plants. Molecular gut content analysis using the specific chloroplast trnL gene from tomato confirmed that adult and immature O. sauteri feed on both resistant and susceptible genotypes, and feeding behavior assays revealed that resistance did not affect plant feeding or prey acceptance by O. sauteri adults. These results demonstrate a direct negative effect of phytochemicals on a nontarget beneficial species and indicate that resistance mediated by phytochemicals can affect organisms that do not solely feed on phloem sap. The results also indicate that the mode of action and the potential ecological effects of phytochemical-mediated resistance are broader than previously recognized.

Effects of a decade of organic fertilizer substitution on vegetable yield and soil phosphorus pools, phosphatase activities, and the microbial community in a greenhouse vegetable production system

Partial substitution of chemical fertilizers by organic amendments is adopted widely for promoting the availability of soil phosphorus (P) in agricultural production. However, few studies have comprehensively evaluated the effects of long-term organic substitution on soil P availability and microbial activity in greenhouse vegetable fields. A 10-year (2009–2019) field experiment was carried out to investigate the impacts of organic fertilizer substitution on soil P pools, phosphatase activities and the microbial community, and identify factors that regulate these soil P transformation characteristics. Four treatments included 100% chemical N fertilizer (4CN), 50% substitution of chemical N by manure (2CN+2MN), straw (2CN+2SN), and combined manure with straw (2CN+1MN+1SN). Compared with the 4CN treatment, organic substitution treatments increased celery and tomato yields by 6.9−13.8% and 8.6−18.1%, respectively, with the highest yields being in the 2CN+1MN+1SN treatment. After 10 years of fertilization, organic substitution treatments reduced total P and inorganic P accumulation, increased the concentrations of available P, organic P, and microbial biomass P, and promoted phosphatase activities (alkaline and acid phosphomonoesterase, phosphodiesterase, and phytase) and microbial growth in comparison with the 4CN treatment. Further, organic substitution treatments significantly increased soil C/P, and the partial least squares path model (PLS-PM) revealed that the soil C/P ratio directly and significantly affected phosphatase activities and the microbial biomass and positively influenced soil P pools and vegetable yield. Partial least squares (PLS) regression demonstrated that arbuscular mycorrhizal fungi positively affected phosphatase activities. Our results suggest that organic fertilizer substitution can promote soil P transformation and availability. Combining manure with straw was more effective than applying these materials separately for developing sustainable P management practices.

Simulation of N2O emissions from greenhouse vegetable production under different management systems in North China

Quantifying greenhouse gas emissions from greenhouse vegetable production systems (GVPS) is helpful to direct carbon sequestration and greenhouse gas emissions reduction. The objectives of this study were to (i) evaluate the performance of the improved WHCNS-Veg model (soil Water Heat Carbon Nitrogen Simulation for Vegetable) in simulating nitrous oxide (N2O) emissions under different GVPS and (ii) analyze the impact of different management systems on N2O emissions from the GVPS. Greenhouse vegetable experiments were carried out under different management systems, including conventional (CON), integrated (INT) and organic (ORG), in Quzhou County, Hebei province from 2013 to 2015. Field observations of soil water content, soil nitrate concentration and N2O emissions were used to calibrate and validate the WHCNS-Veg model. The sensitivity analysis results showed that the effects of soil hydraulic parameters on N2O emissions were higher than those of N transformation and vegetable genetic parameters. The improved WHCNS-Veg model simulated soil water content, soil nitrate concentration and N2O emissions well under different GVPS. The average N2O emissions in the spring-summer season (16.3 kg N ha−1) were about 2.5 times higher than the autumn-winter season (6.4 kg N ha−1). Among the four seasons, the average N2O emissions of CON, ORG and INT were 13.5, 11.3 and 9.3 kg N ha−1, respectively, accounting for 1.4–1.7% of the total fertilizer input. The N2O emissions of the INT and ORG systems were 31.1% and 16.3% lower than the CON treatment, respectively. The results indicated that the improved WHCNS-Veg model can be used to simulate and analyze N2O emissions under different management systems and substituting organic manure for chemical fertilizer could effectively reduce the N2O emissions in the GVPS.

Impact of anaerobic soil disinfestation on seasonal N2O emissions and N leaching in greenhouse vegetable production system depends on amount and quality of organic matter additions

Greenhouse vegetable production (GVP) systems in China receive excessive amounts of fertilizers (>1500 kg N ha−1 yr−1) and irrigation (>1200 mm yr−1), which results in severe soil degradation. Moreover, soil borne diseases are common as the same crop is planted continuously over years. Anaerobic soil disinfestation (ASD) is a method carried out every 3–4 years during the summer fallow period to combat soil-borne diseases and to improve soil health. The standard ASD practice, which is carried out before the cropping season, involves incorporation of organic matter (i.e. rice shells or straw) into the soil, covering of the soil with plastic films and soil irrigation until saturation. However, many farmers incorporate large amounts of organic nitrogen fertilizer for priming ASD. In this study, we investigated if incorporation of rice shells plus chicken manure (ASD+RM; farmers practice) provokes higher environmental N losses (N2O emissions and N leaching) during the ASD and the following tomato crop growing period as compared to the standard ASD practice (ASD+R: only rice shells) or a Control (fallow, but with incorporation of organic manure, standard in non-ASD years). Results showed that ASD+RM increased seasonal (ASD/fallow period plus tomato crop growing period) soil N2O emissions by a factor of 3 (ASD+RM: 14.1 kg N2O-N ha−1; ASD+R: 4.7 kg N2O-N ha−1), with 2/3 of emissions occurring during the 25 days long ASD period. Across all treatments, nitrate (NO3−) leaching dominated total N leaching (75%), with significantly lower rates observed for ASD+R as compared to ASD+RM. For both ASD treatments, total dissolved organic nitrogen (DON) leaching was a factor of two higher than for the Control. Crop productivity was not affected by ASD. Our findings imply that ASD+RM should be abandoned as the additional supply of manure N results in high environmental N losses without further increasing yields.

Combined effects of irrigation level and fertilization practice on yield, economic benefit and water-nitrogen use efficiency of drip-irrigated greenhouse tomato

The over-application of irrigation and chemical fertilization in the greenhouse vegetable production system (GVPS) in China can jeopardize fruit quality, compromise economic profit and waste resources. Seeking optimal water and fertilizer supply mode for GVPS is urgently required to improve resource use efficiency and economic benefit. A greenhouse experiment was conducted during four consecutive tomato growing seasons to investigate the combined effects of various irrigation levels and fertilization practices on yield, fruit quality, economic benefit, water use efficiency (WUE) and nitrogen use efficiency (NUE) of drip-fertigated tomato, and to obtain the optimal water and fertilizer supply practice by the principal component analysis (PCA). On the basis of full irrigation (W1: 100%ETc, ETc was the crop evapotranspiration), two deficit irrigation levels (W2: 75%ETc, W3: 50%ETc) were set. Except for the conventional fertilization practice used by local farmers (CC: chicken manures for basal application and chemical fertilizer for topdressing), four other fertilization practices were considered, including soluble organic fertilizers for topdressing (SO), soluble chemical fertilizers for topdressing (SC), both soluble organic and chemical fertilizers for topdressing (SOSC), and a control with no fertilizer application under full irrigation (CK). The results showed that SOSC obtained relatively high plant nitrogen uptake, net profit and WUE, and significantly improved tomato yield. Organic fertilizers addition reduced nitrate content in tomato fruits. Deficit irrigation promoted CC to obtain higher WUE than SC. According to the result of PCA, the comprehensive ranking of SOSC was first among the fertilization practices, regardless of irrigation levels and growing seasons. W1SOSC and W2SOSC were highly recommended for greenhouse tomato production in spring and autumn seasons, respectively.

Reducing the environmental risks related to phosphorus surplus resulting from greenhouse cucumber production in China

Excessive phosphorus (P) inputs from manure and synthetic fertilizers leads to high environmental risk in greenhouse vegetable production systems. In the current study, we determined whether a system of P fertilization that attempts to achieve a zero-P surplus balances agronomic, economic, and environmental concerns. A field experiment was conducted to evaluate the potential of integrated inorganic and organic nutrient management to provide both high yield and minimal environmental risk in a typical region of greenhouse vegetable production in China. Three treatments were compared: farmers’ practice (FP), current recommended nutrient management (CRNM), and designed balanced nutrient management (DBNM, with P input optimized based on crop demand). The results indicated that in the greenhouse cucumber production system, the seasonal P surplus of FP was as high as 410 kg P ha−1; this increased the movement of P to the subsoil, causing a high risk of P loss, i.e., a P index >9, and a high eutrophication potential (87.4 kg PO4-eq ha−1). Compared with FP, CRNM (which had a 76% lower P fertilizer input) significantly reduced the P surplus, the risk of P loss, and the eutrophication potential, and increased yield incomes and net ecosystem economic benefits by 18.0% and 31.8%, respectively. Compared with CRNM, DBNM significantly reduced the P surplus by 84.5% and the environmental damage cost by 19.0%, while increased the input cost by 23.0%. Therefore, the DBNM strategy is recommended in greenhouse vegetable production to reduce the P surplus and environmental costs, and to obtain high yield and economic benefits.

RNA-Seq Identification of Cd Responsive Transporters Provides Insights into the Association of Oxidation Resistance and Cd Accumulation in Cucumis sativus L.

Greenhouse vegetable production (GVP) has grown rapidly and has become a major force for cucumber production in China. In highly intensive GVP systems, excessive fertilization results in soil acidification, increasing Cd accumulation and oxidative stress damage in vegetables as well as increasing health risk of vegetable consumers. Therefore, enhancing antioxidant capacity and activating the expression level of Cd transporter genes seem to be feasible solutions to promote plant resistance to Cd stress and to reduce accumulated Cd concentration. Here, we used transcriptomics to identify five cucumber transporter genes (CsNRAMP1, CsNRAMP4, CsHMA1, CsZIP1, and CsZIP8) in response to cadmium stress, which were involved in Cd transport activity in yeast. Ionomics, gene expression, and REDOX reaction level association analyses have shown that the transcript of CsNRAMP4 was positively correlated with Cd accumulation and antioxidant capacity of cucumber roots. The expression level of CsHMA1 was negatively correlated with Cd-induced antioxidant capacity. The overexpression of CsHMA1 significantly relieved Cd stress-induced antioxidant activities. In addition, shoots with high CsHMA2 expression remarkably presented Cd bioaccumulation. Grafting experiments confirmed that CsHMA1 contributed to the high antioxidant capacity of cucumber, while CsHMA2 was responsible for the transport of Cd from the roots to the shoots. Our study elucidated a novel regulatory mechanism for Cd transport and oxidative damage removal in horticultural melons and provided a perspective to regulate Cd transport artificially by modulating Cd accumulation and resistance in plants.

Excessive phosphorus inputs dominate soil legacy phosphorus accumulation and its potential loss under intensive greenhouse vegetable production system

Phosphorus (P) is an essential element for crop growth and it plays a critical role in agricultural production. Excessive P applications has become a serious concern in Chinese greenhouse vegetable production (GVP) systems. Nevertheless, P accumulation (legacy P) in GVP profile soils and its potential loss remain poorly documented. Hence, this study aimed to response this issue via paired collection of 136 soil samples (0–30, 30–60 and 60–90 cm depth) and 41 vegetable samples from both plastic greenhouses (PG) and solar greenhouses (SG) in Shouguang, Shandong province. Results showed that the annual input of P ranged from 772 to 2458 kg ha−1 for different vegetables through the whole growing season versus little vegetable P uptake (ranging from 47.8 to 155 kg ha−1). Results also revealed significant P accumulation in both SG and PG profile soils. Compared to arable soils (background soils), legacy P to the depth of 90 cm in PG and SG soils were 3.28 and 11.16 Mg P ha−1, respectively. The content of total P in PG and SG soils significantly increased with cultivation duration. The maximum environmental capacity of P in SG soils was 187 Mg ha−1, and the maximum number of years for safe planting was 38 yrs. After four years of cultivation, P loss would occur in these soils and the loss rate of P increased with cultivation duration. Opposite to PG soils, a potentially higher risk of P losses took place in SG soils. Our results also demonstrated that excessive P inputs driven by intensive agricultural practices dominated legacy P accumulation within the profile soils and its losses in GVP systems. Site-specific P managements, including improving P use efficiency, reducing further P surplus and reusing legacy P in soils, are urgently needed to minimize P loss. At the same time, the potential loss of subsoil P could not be neglected.

The potential importance of soil denitrification as a major N loss pathway in intensive greenhouse vegetable production systems

BackgroundAbout 30 % of vegetables in China are produced in intensively managed greenhouses comprising flood irrigation and extreme rates of nitrogen fertilizers. Little is known about denitrification N losses.MethodsSoil denitrification rates were measured by the acetylene inhibition technique applied to anaerobically incubated soil samples. Four different greenhouse management systems were differentiated: Conventional flood irrigation and over-fertilization (CIF, 800 kg N ha−1, 460 mm); CIF plus straw incorporation (CIF+S, 889 kg N ha−1, 460 mm); Drip fertigation with reduced fertilizer application rates (DIF, 314 kg N ha−1, 190 mm); DIF plus straw incorporation (DIF+S, 403 kg N ha−1, 190 mm). Soil denitrification was measured on nine sampling dates during the growing season (Feb 2019-May 2019) for the top-/ subsoil (0 – 20/ 20- 40 cm) and on three sampling dates for deep soils (40-60/ 80-100 cm). Data was used to constrain N-input-output balances of the different vegetable production systems.ResultsRates of denitrification were at least one magnitude higher in topsoil than in sub- and deep soils. Total seasonal denitrification N losses for the 0 – 40 cm soil layer ranged from 76 (DIF) to 422 kg N ha−1 (CIF+S). Straw addition stimulated soil denitrification in top- and subsoil, but not in deep soil layers. Integrating our denitrification data (0-100 cm) with additional data on N leaching, N2O emissions, plant N uptake, and NH3 volatilization showed, that on average 50 % of added N fertilizers are lost due to denitrification.ConclusionsDenitrification is likely the dominant environmental N loss pathway in greenhouse vegetable production systems. Reducing irrigation and fertilizer application rates while incorporating straw in soils allows the reduction of accumulated nitrate.

10-Year fertilization alters soil C dynamics as indicated by amino sugar differentiation and oxidizable organic C pools in a greenhouse vegetable field of Tianjin, China

Understanding the temporal changes of soil organic C (SOC) pools and microbial residues is essential for clarifying SOC dynamics in agroecosystems; however, this information remains largely unclear in greenhouse vegetable production (GVP) systems. Here, based on information of SOC pools (i.e., oxidizable organic C pools) and microbial residue C (MRC, as indicated by amino sugars differentiation), a 10-year (2009–2019) field experiment with fertilization was conducted to evaluate how fertilization alters SOC dynamics in a GVP field in Tianjin, China. The experiment includes four treatments (equal N, P2O5, and K2O inputs): 100% chemical N (N100), 50% substitution of chemical N with manure-N (N50M50), straw-N (N50S50), and manure-N plus straw-N (N50M25S25). Results showed that the values of SOC, lability index, and C management index increased and decreased linearly with time in N50M50- and N100-amended soils, respectively, which were mainly induced by the changes in labile C fractions. Based on logistic regression models, we found that these indices in straw-amended soils (N50M25S25 and N50S50) were rapidly increased between 2009 and 2013, and then approach steady levels between 2015 and 2019. These findings suggested that we should guarantee enough C inputs to maintain the level and quality of SOC, otherwise it will cause C loss in the unique GVP soils. Besides, straw-amended treatments increased MRC contents and enlarged their contributions to SOC sequestration, whereas these indices in N100 treatment decreased linearly with the time of fertilization. In conclusion, long-term chemical application alone was not beneficial for SOC accumulation, whereas organic amendments brought several benefits for SOC sequestration in GVP soils. Our results implied that C sequestration in GVP soils is to a large extent determined by the amounts and time of fertilization.