Greenhouse Vegetable Production Systems Research Articles

Modeling dissolved organic nitrogen dynamics under different N management practices for intensive greenhouse production using an improved WHCNS_veg model

Excess dissolved organic nitrogen (DON) leaching occurs due to manure or fresh organic matter application coupled with high irrigation frequency in intensive greenhouse vegetable production systems (GVPS). Quantifying DON leaching is crucial in developing best management practices for intensive GVPS. The objectives of this study were to develop a DON leaching component for the water and N management model for greenhouse vegetables (WHCNS_veg) and to evaluate nitrate and DON leaching under different N management practices. Two seasons of tomato greenhouse experiments with several N management practices were conducted in Shouguang County, Shandong Province in China. The measured soil water content, soil nitrate and DON concentrations, and tomato yield were used to calibrate and evaluate the improved WHCNS_veg model. Results showed that the WHCNS_veg performed well in modeling soil water content, soil nitrate and DON concentrations, and tomato yield, giving normalized root mean square error values of 4.4%, 37.2%, 45.8% and 3.8%, respectively. Manure application significantly enhanced DON leaching, which accounted for 8.8% to 18.7% of the total N leaching under different N management practices. The simulated and measured tomato yield was not sensitive to different N management practices (except for the no N input treatment). However, the amounts of nitrate leaching, DON leaching, and N gas emission (NxO and NH3) under conventional N management were 2.1, 1.3, and 1.1-fold greater than those in the reduced N management treatment, respectively. Reduced N management practices should be recommended in the greenhouse tomato production in North China, which had a relatively high vegetable yield, less environmental impact, and more sustainability. Results indicated that the improved WHCNS_veg model has great potential to optimize N management and assess the environmental impact of GVPS.

Drip fertigation significantly reduces nitrogen leaching in solar greenhouse vegetable production system

Vegetable production in solar greenhouses in northern China results in the excessive use of nitrogen (N) fertilizers and water via flooding irrigation. Both factors result in low N use efficiency and high environmental costs because groundwater becomes contaminated with nitrate (NO3−). Four consecutive tomato (Lycopersicum esculentum Mill.) cropping seasons were tested whether drip fertigation and/or the incorporation of maize straw (S) may significantly reduce NO3− and dissolved organic N (DON) leaching while increasing the water-use efficiency (WUE) and partial factor productivity of applied N (PFPN) of the tomatoes. The following treatments were used: ① conventional flooding irrigation with overfertilization (CIF, 900 kg N ha−1 season−1), ② CIF + S, ③ drip irrigation with optimized fertilization (DIF, 400 kg N ha−1 season−1), ④ DIF + S. We found that (1) DIF significantly increases the PFPN and WUE by 262% and 73% without compromising the yield compared with CIF, respectively. (2) For CIF, approximately 50% of the total N input was leached at a NO3−/DON ratio of approximately 2:1. (3) Compared with CIF, DIF reduced NO3− and DON leaching by 88% and 90%, respectively. Water percolation was positively correlated with N leaching (p < 0.001). (4) Straw application only reduced NO3− leaching losses in the first year and did not affect DON leaching overall, although DON leaching was increased in DIF in the first growing season. In conclusion, DIF significantly reduces NO3− and DON leaching losses by approximately 90% compared with the current farmer practice (CIF). Considering the significant DON leaching losses, which have been overlooked because previous measurements focused on NO3−, DON should be considered as a primary factor of environmental pollution in conventional solar greenhouse vegetable production systems.

Other Design Information Resources - Florida Greenhouse Vegetable Production Handbook, Vol 2

There are many sources of information that can be very useful in the development of a profitable greenhouse vegetable production system. If there are greenhouses already being successfully operated in the area, it can be very helpful to talk directly with veteran local producers. The county Extension agent can help with information about who the active growers are and about local growers' associations. Established growers should have informed opinions about professional contractors that install greenhouses and about what works and what doesn't. First published Dec.1990.

Soil threshold values for cadmium based on paired soil-vegetable content analyses of greenhouse vegetable production systems in China: Implications for safe food production

Greenhouse vegetable production (GVP) is the major type of vegetable production in China. However, dietary exposure of heavy metals through vegetable consumption has been identified as a potential risk to human health. To ensure safety of vegetables, soil threshold values (STVs) of cadmium (Cd) in GVP systems were assessed based on analysis of soil-vegetable Cd contents in relation to human health risk. Contents of Cd were determined in 324 sampled soil-vegetable pairs from five GVP systems in three Chinese provinces. Soil Cd contents ranged from 0.07 to 1.32 mg kg−1, with 17.9% of sampled soils exceeding current Chinese threshold values. Vegetable Cd contents ranged from 0.0003 to 0.546 mg kg−1, with 8.6% exceeding permissible maxima. Vegetable type and soil pH significantly affected Cd transfer from soil to vegetable with lower transfer at neutral (6.5 < pH ≤ 7.5) to alkaline (pH > 7.5) soils and uptake decreasing in the order: Leafy > rootstalk > fruit. Consequently, both soil pH and vegetable type should be taken into consideration as suggested when revising current STVs for Cd in GVP systems in order to capture the health risk correctly and ensure safe vegetable consumption.

Accumulation Characteristics of Heavy Metals in Greenhouse Soil and Vegetables in Siping City, Jilin Province

Based on the typical greenhouse vegetable production system in Siping City, Jilin Province, 124 soil samples were collected from greenhouse soils growing vegetables (GSGV), fields growing maize (FGM), and forest soil (FS) under different land utilization patterns. In addition, other samples including greenhouse vegetables (81), fertilizers (50), and irrigation water (10) were also collected in the studied region. To illustrate the accumulation characteristics of heavy metals in GSGV and greenhouse vegetables, the heavy metal content of different samples was measured using inductively coupled plasma mass spectrometry (ICP-MS) technology. The results indicated that the heavy metal content in GSGV was much higher than that in FGM and FS except for lead (Pb). Heavy metals including cadmium (Cd), copper (Cu), chromium (Cr), nickel (Ni), and zinc (Zn) in GSGV presented with various degrees of accumulation. The mean value of Cd content in the soils in the investigation region was 0.45 mg·kg-1, with about 42.8% of all the soil samples exceeding the Cd content criterion of the Environmental Quality Evaluation Standard for Farmland in Greenhouse Vegetable Production (HJ 333-2006). The content of the other heavy metals was in the normal range, and all met the regulations of the standard. In comparison with different vegetable categories, leafy vegetables showed much higher heavy metal concentrations (Cd 0.033 mg·kg-1 fresh weight) than did fruity ones. In total, about 2.5% and 1.2% of vegetable samples exceeded the regulated values of Cd and Pb recommended by the Standard of Food limits, respectively. With the cultivation time prolonged, heavy metal concentration in soils and vegetables all increased synchronously as the pH value decreased. The content of heavy metals in greenhouse vegetables was significantly influenced by soil pH and organic matter. It can be concluded that the health risk of greenhouse vegetables increased with GSGV accumulating more heavy metals due to the substantial application of chemical fertilizer and manure containing high level of heavy metals.

Cadmium phytoavailability under greenhouse vegetable production system measured by diffusive gradients in thin films (DGT) and its implications for the soil threshold

The diffusive gradients in thin films (DGT) technique is recognized to have advantages over traditional techniques. For example, the passive measurement generally follows the principle of metal uptake by plants, and its result incorporates the influences of soil properties, which may make DGT a good protocol for improving soil quality guidelines (SQGs). However, DGT has rarely been applied to assess Cd phytoavailability in soils under greenhouse vegetable production (GVP) systems. In this study, 29 turnips (Raphanussativus L.), 21 eggplants (Solanum melongena L.) and their corresponding soils were collected from GVP systems in Dongtai and Shouguang, eastern China. Simple linear regression and stepwise regression were performed using the soil Cd content and soil properties to predict the vegetable Cd content. Soil thresholds were derived based on both total and available Cd concentrations. The results showed that total Cd, DGT-measured Cd (DGT-Cd), soil-solution Cd (Soln-Cd) and CaCl2-extractable Cd (CaCl2-Cd) were all significantly correlated with vegetable Cd. DGT-Cd had the best correlation with turnip Cd. The total Cd threshold values ranged from 4.87 (pH 6.5) to 5.18 (pH 7.5) mg kg−1 for turnips and 14.60 (pH 6.5) to 14.90 (pH 7.5) mg kg−1 for eggplants. These Cd thresholds were higher than the current SQGs. The predicted of turnip Cd by DGT-Cd was not improved significantly by further considering the soil properties. The calculated soil threshold of DGT-Cd was 5.35 μg L−1 for turnips. However, the predicted soil threshold of DGT-Cd for eggplant was improved by including SOM, with R2 values from 0.53 to 0.70. The DGT-Cd threshold was calculated as 1.81 μg L−1 for eggplant (30.0 g kg−1 SOM). In conclusion, whether DGT measurements are independent of soil properties and preferable for the evaluation of Cd phytoavailability and the generation of soil thresholds remains to be clarified in future research.

Accumulation characteristics and potential risk of heavy metals in soil-vegetable system under greenhouse cultivation condition in Northern China

Heavy metal pollution in greenhouse vegetable production system is a growing concern for public health. In this study, 87 soil and 72 vegetable samples were collected from greenhouse vegetable production systems in Shanxi province, Northern China, aiming to evaluate the accumulation characteristics and potential risk of heavy metals in soil-vegetable system under greenhouse condition. The results showed that Cd and Pb concentrations in 72.4% and 35.5% of the soil samples were higher, while all of As, Cr, Ni, Cu, Zn samples were lower than the Grade II value in Environmental Quality Standard for Soils (GB15618-1995). Nearly 99% of the total amount Pb existed in the form of residual and could not be absorbed by vegetables. The proportions of As, Cd, Zn in ionic form, bound to carbonates and the exchangeable fraction were 6.21, 13.71, and 13.47% respectively, and were relatively higher than other metals (Cr, Cu, Ni, Pb). The transfer factors (TF) of As, Cr, Ni, Pb were found to be higher in leaf and fruit vegetables than that in tuber vegetables. With a relatively low total concentration and high proportion of available form in soils, Cd showed relatively larger TF in three kinds of vegetables than other metals. The concentrations of Cr, Ni and Pb in three kinds of greenhouse vegetables exceeded the limit in national food safety standards. Especially, Ni in leaf and fruit vegetables showed significantly higher hazard quotient (HQ) than that in tube vegetables. Overall, leaf and fruit vegetables had a relatively higher hazard index (HI) than tube types, and exceeded 1, suggesting that there was larger potential health risk by ingestion of heavy metals through fruit and leaf vegetables. Thus, in order to avoid human body health endangered by heavy metals through the food chain, appropriate management measures should be implemented in greenhouse cultivation, especially tuber vegetables be cultivated instead of leaf and fruit types.

Soil environmental quality in greenhouse vegetable production systems in eastern China: Current status and management strategies

Greenhouse vegetable production (GVP) has become an important source of public vegetable consumption and farmers' income in China. However, various pollutants can be accumulated in GVP soils due to the high cropping index, large agricultural input, and closed environment. Ecological toxicity caused by excessive pollutants' accumulation can then lead to serious health risks. This paper was aimed to systematically review the current status of soil environmental quality, analyze their impact factors, and consequently to propose integrated management strategies for GVP systems. Results indicated a decrease in soil pH, soil salinization, and nutrients imbalance in GVP soils. Fungicides, remaining nutrients, antibiotics, heavy metals, and phthalate esters were main pollutants accumulating in GVP soils comparing to surrounding open field soils. Degradation of soil ecological function, accumulation of major pollutants in vegetables, deterioration of neighboring water bodies, and potential human health risks has occurred due to the changes of soil properties and accumulation of pollutants such as heavy metals and fungicides in soils. Four dominant factors were identified leading to the above-mentioned issues including heavy application of agricultural inputs, outmoded planting styles with poor environmental protection awareness, old-fashion regulations, unreasonable standards, and ineffective supervisory management. To guarantee a sustainable GVP development, several strategies were suggested to protect and improve soil environmental quality. Implementation of various strategies not only requires the concerted efforts among different stakeholders, but also the whole lifecycle assessment throughout the GVP processes as well as effective enforcement of policies, laws, and regulations.

Heavy metals in intensive greenhouse vegetable production systems along Yellow Sea of China: Levels, transfer and health risk

Recently, greenhouse vegetable production (GVP) has grown rapidly and counts a large proportion of vegetable production in China. In this study, the accumulation, health risk and threshold values of selected heavy metals were evaluated systematically. A total of 120 paired soil and vegetable samples were collected from three typical intensive GVP systems along the Yellow Sea of China. Mean concentrations of Cd, As, Hg, Pb, Cu and Zn in greenhouse soils were 0.21, 7.12, 0.05, 19.81, 24.95 and 94.11 mg kg−1, respectively. Compared to rootstalk and fruit vegetables, leafy vegetables had relatively high concentrations and transfer factors of heavy metals. The accumulation of heavy metals in soils was affected by soil pH and soil organic matter. The calculated hazard quotients (HQ) of the heavy metals by vegetable consumption decreased in the order of leafy > rootstalk > fruit vegetables with hazard index (HI) values of 0.61, 0.33 and 0.26, respectively. The HI values were all below 1, which indicates that there is a low risk of greenhouse vegetable consumption. Soil threshold values (STVs) of heavy metals in GVP system were established according to the health risk assessment. The relatively lower transfer factors of rootstalk and fruit vegetables and higher STVs suggest that these types of vegetables are more suitable for cultivation in greenhouse soils. This study will provide an useful reference for controlling heavy metals and developing sustainable GVP.

Phthalate esters in soil, plastic film, and vegetable from greenhouse vegetable production bases in Beijing, China: Concentrations, sources, and risk assessment

The increased use of plastic film in greenhouse vegetable production (GVP) could result in phthalate ester (PAE) contamination in vegetables. However, limited information is currently available on their occurrence and associated potential risks in GVP systems. The present study documents the occurrence and composition of 15 PAEs in soil, plastic film, and vegetable samples from eight large-scale GVP bases in Beijing, China. Results showed that PAEs are ubiquitous contaminants in these GVP bases. Total PAE concentrations ranged from 0.14 to 2.13mg/kg (mean 0.99mg/kg) in soils and from 0.15 to 6.94mg/kg (mean 1.49mg/kg) in vegetables. Di (2-ethylhexyl) phthalate, di-n-butyl phthalate, and diisobutyl phthalate were the most abundant components, which accounted for >90% of the total PAEs. This investigation also indicated that the widespread application of plastic film in GVP systems may be the primary source of these PAEs. The non-cancer and carcinogenic risks of target PAEs were estimated based on the exposures of vegetable intake. The hazard quotients of PAE in all vegetable samples were lower than 1 and the carcinogenic risks were also at acceptable levels for consumers. The data in this study can provide valuable information to understand the status of potential pollutants, specifically PAEs, in GVP systems.

The impact of Cu, Zn and Cr salts on the relationship between insect and plant parasitic nematodes: A reduction in biocontrol efficacy

Accumulation and potential health risks of toxic elements are associated with excessive fertilizer and manure applications in vegetable production systems. The goal of the present study was to explore the effects of potential toxic elements on the function of a cohort of beneficial organisms, specifically, the insect parasitic nematodes known as entomopathogenic nematodes. We assessed the impact of heavy metal accumulation on entomopathogenic nematodes (Steinernema carpocapsae and Heterorhabditis bacteriophora) and plant parasitic nematodes (Meloidogyne incognita). Genearlly, pretreatment with 1.5mg Cu/L, 50mg Zn/L or 7.5mg Cr/L solution for 24h caused direct mortality of infective juvenile S. carpocapsae and H. bacteriophora nematodes, and lowered virulence of H. bacteriophora against Galleria mellonella. Interestingly, we found that 24h exposure to 4.5mg Cu/L, 50mg Zn/L or 7.5mg Cr/L solution already caused higher mortality in H. bacteriophora than M. incognita in a laboratory assay. Moreover, in a potted plant experiment, pretreatment of H. bacteriophora with Cu, Zn or Cr salts resulted in increased penetration of M. incognita into cucumber roots compared with H. bacteriophora that were not treated (thus reducing biocontrol efficacy). Pretreatment of S. carpocapsae with Cu also caused increased penetration of M. incognita into cucumber roots; however, none of the Zn and Cr pretreatment concentrations exposed to S. carpocapsae resulted in increased M. incognita root penetration, and lower concentrations of these elements caused decreased penetration (enhancing biocontrol efficacy). Our results indicate that heavy metals can have a direct negative effect on entomopathogenic nematodes (via direct mortality) and also an indirect effect by disrupting biocontrol efficacy against plant parasitic nematodes, but in some cases low concentration may stimulate biocontrol activity. High levels of heavy metal accumulation in greenhouse vegetable production systems could substantially influence nematode community structure and impact other soil biota as well.

Sustainability assessment of greenhouse vegetable farming practices from environmental, economic, and socio-institutional perspectives in China.

To provide growing population with sufficient food, greenhouse vegetable production has expanded rapidly in recent years in China and sustainability of its farming practices is a major concern. Therefore, this study assessed the sustainability of greenhouse vegetable farming practices from environmental, economic, and socio-institutional perspectives in China based on selected indicators. The empirical data were collected through a survey of 91 farm households from six typical greenhouse vegetable production bases and analysis of environmental material samples. The results showed that heavy fertilization in greenhouse vegetable bases of China resulted in an accumulation of N, P, Cd, Cu, Pb, and Zn in soil, nutrient eutrophication in irrigation water, and high Cd in some leaf vegetables cultivated in acidic soil. Economic factors including decreased crop yield in conventional farming bases, limited and site-dependent farmers' income, and lack of complete implementation of subsidy policies contributed a lot to adoption of heavy fertilization by farmers. Also, socio-institutional factors such as lack of unified management of agricultural supplies in the bases operated in cooperative and small family business models and low agricultural extension service efficiency intensified the unreasonable fertilization. The selection of cultivated vegetables was mainly based on farmers' own experience rather than site-dependent soil conditions. Thus, for sustainable development of greenhouse vegetable production systems in China, there are two key aspects. First, it is imperative to reduce environmental pollution and subsequent health risks through integrated nutrient management and the planting strategy of selected low metal accumulation vegetable species especially in acidic soil. Second, a conversion of cooperative and small family business models of greenhouse vegetable bases to enterprises should be extensively advocated in future for the unified agricultural supplies management and improved agricultural extension service efficiency, which in turn can stabilize vegetable yields and increase farmers' benefits.

Changes of C and N stocks in the subtropical Dianchi lake watershed in southwest China due to LUCC

The change from forest to agricultural land in the last three decades represents a significant shift in land use in China. This study was conducted to evaluate how change from forest to greenhouse cabbage production affected soil organic carbon (SOC) and total nitrogen (TN) stocks in surface soil. Our results showed that converting forest to greenhouse vegetable production led to increases in SOC and TN concentrations and stocks, and decreases in C:N ratio in the top soil. The accumulation rates of SOC and TN in the surface soil (0-40cm) were estimated to be 4.638 Mg ha -1 yr -1 and 1.113 Mg ha -1 yr -1 respectively, over an average period of 8 years after change of forest to greenhouse vegetable production. We conclude that greenhouse vegetable production system could be an effective strategy to improve SOC and TN stocks in the subtropical Dianchi lake watershed.

Optimizing nitrogen and water inputs for greenhouse vegetable production

Greenhouse vegetable production systems require high N and irrigation inputs. Commonly, these systems are associated with environmental problems caused by nitrate leaching. Given increasing societal pressure to reduce these problems, there is a requirement to optimally use N and water inputs. Optimal management practices will be influenced by the greenhouse technological level, the growing medium and the quality of the available water supply. Four broad categories of greenhouse vegetable production can be considered: (i) high technology (HT) in soil, (ii) HT in substrate, (iii) low to medium technology (LMT) in soil, and (iv) LMT in substrate. Examples of HT systems are glasshouses in The Netherlands and Belgium, and of LMT are plastic greenhouses in the Mediterranean Basin. Combined drip irrigation and fertigation are being increasingly used which provide a high technical capacity for precise N and irrigation management. Tools are required that enable growers to take advantage of this technical capacity. For optimal irrigation management, suitable tools are decision support systems (DSS) incorporating simulation models to estimate daily crop water requirements and soil/substrate moisture sensors. For optimal N management, suitable tools are DSS employing simulation models that estimate N fertilizer requirements based on an N balance approach combined with soil or soil solution testing. Crop/plant monitoring is potentially useful, but as yet further work is required. For both irrigation and N management, the recommended approach is combined prescriptive-corrective management, which can also be described as combining modelling and monitoring approaches whereby models are used to prescribe management plans and monitoring is used to identify when adjustments are required.

Accumulation status, sources and phytoavailability of metals in greenhouse vegetable production systems in Beijing, China

The accumulation status, sources and phytoavailability of selected metals in greenhouse vegetable production systems in peri-urban areas of Beijing were investigated. The mean concentrations of As, Cd, Cr, Hg and Pb in greenhouse soils were 8.44, 0.25, 69.0, 0.09 and 22.0mgkg−1, dw, respectively. According to principal component analysis, As, Cd, Cr and Hg are mainly from anthropogenic source, but Pb is likely from natural source. Metal concentrations in all vegetable samples were decreased in the order of Cr>As>Pb>Cd>Hg. Compared with root and fruit vegetables, leaf vegetables had relatively high concentrations and transfer factors of heavy metals, except for Cd. By including soil pH, OM and greenhouse soil metals, 10 empirical models were derived using stepwise multiple linear regression analysis to predict heavy metal concentrations in the edible parts of different vegetables. Among the different vegetable groups, the highest intakes of metals occurred through consumption of leaf vegetables for the two age groups, except for Cd. The HI value of the studied metals were all below 1, indicating that consumption of vegetables grown in greenhouse soils was of low risk to consumers in our study area.

Nitrogen removal from the surface runoff of a field scale greenhouse vegetable production system

Nutrient losses from greenhouse vegetable production systems may impair water quality in the Taihu Lake Region of China. We studied the characteristics of nitrogen (N) lost via runoff from greenhouse vegetable systems and strategies for minimizing N entering water bodies. A two-year experiment at a field scale was conducted to monitor N surface runoff. An eco-ditch (148 m2) and a low N input paddy field (135 kg N ha−1, 550 m2) were designed to remove N from the surface runoff of a 25 × 50 m greenhouse vegetable field. The greenhouse was not covered from late June to mid-October each year, and runoff occurred multiple times during this period. Annual total N loss in runoff from the greenhouse vegetable site was 25.3 and 33.5 kg ha−1 in 2010 and 2011, respectively. Nitrate-N was the major form of N lost in the runoff. The average runoff volume was 289 mm (varied from 221 to 357 mm), which contained 15.7 (varied from 3.3 to 39.2 mg L−1) mg L−1 total N. The eco-ditch system and the wetland paddy field (WPF) effectively reduced total N discharge; the removal rates reached 49.9% and 58.7% and the average removal capacities were 12.4 g N m−2 and 4.1 g N m−2 in 2010 and 2011, respectively. The combined system of the ecological ditch–WPF removed almost 79% total N in the runoff. Ecological ditch or paddy wetland can be a water management option available to growers in this region to economically reduce pollutants in agricultural runoff.

Changes in potential denitrification-derived N2O emissions following conversion of grain to greenhouse vegetable cropping systems

In China, considerable cropland previously under grain production has been rapidly converted to greenhouse vegetable production by farmers since 1980s. Vegetable crops generally require higher nitrogen (N) inputs from manure amendments and more frequent tillage and irrigation operations compared to grain crops. Here, we compared potential denitrification-derived N2O emissions across the soil profile (0–90 cm depth) between grain and greenhouse vegetable fields. Denitrification enzyme activity (DEA) was assessed in the top 0–15 cm soil layer. Soil samples from five wheat (Triticum aestivum L.) – maize (Zea mays L.) fields, paired with adjacent vegetable greenhouse fields, were collected across typical vegetable production regions. Conversion from the grain fields to the greenhouse vegetable fields led to greater potential denitrification-derived N2O emissions in the 0–15 and 15–30 cm depths, respectively, with 4 and 3 times higher cumulative emissions over the 10-day incubation. Continuous manure amendments and chemical N input increased water extractable organic carbon and nitrate concentrations, which significantly enhanced potential denitrification-derived N2O production in the 0–30 cm soil depth of vegetable crop fields. The differences in microbial community for the two cropping systems did not seem to affect the surface N2O production potential since denitrification enzyme activity were not significantly different between the two production systems. There was a small to negligible potential N2O flux in 30–90 cm soil depths for both production systems because of limited carbon availability and microbial activity. Managing surface labile carbon and mineral N pool may be critical in reducing regional N2O emissions in China's greenhouse vegetable production systems.

Fulvic acid displaces manure to improve soil in vegetable greenhouse

Acid soil has led to a significant decrease in vegetable yield in high-yield greenhouse vegetable production system. Chicken manure and fulvic acid (FA) application experiment was conducted to evaluate the effects on chemical properties of soil in vegetable greenhouse so as to confirm whether FA could replace chicken manure in acid soil amelioration under the same addition levels of nutrient, when compared to the effect of chemical fertilizers application alone on acid soil improvement. The results showed that the pH of soil added with chicken manure and FA, respectively, increased from the original value of 5.4 to 5.99 and 6.32 at the end of the experiment, while soil pH applied only with chemical fertilizers decreased to 5.43. Correlation analysis indicated that cation exchange capacity (CEC) of soil was positively correlated with soil pH buffering capacity. The peak values of soil CEC and pH buffering capacity occurred in April each year and subsequently tended to decrease in August and December throughout the experiment. Data demonstrated that chicken manure and FA in combination with soil contributed to soil base saturation that increased from 26.5%, 33.8% to 36.7%, 45.9% in chicken manure and FA treated soil during December 2011 to December 2012, respectively; however, chemical fertilizers displayed an adverse effect on soil base saturation that decreased from 17.1% to 5.6% on the same time period. Exchangeable aluminum (Al) concentration showed a weak but significant increase by 5.2% on August 2012 in comparison to April 2012, as chemical fertilizers were added into soil alone. Unlike to chemical fertilizer, chicken manure and FA significantly decreased soil exchangeable Al concentration from the original value of 5.37 cmol kg−1 to 4.56 and 4.22 cmol kg−1 at the end of experiment respectively. Compared to total yield treated solely with chemical fertilizers, chemical fertilizers combination with chicken manure or FA resulted in an increase in total yield in 2011 and 2012. Although chicken manure and FA possessed the same trend of improving acidic soil in vegetable greenhouse, a greater contribution was attributed to FA due to its lower mineralization rate of organic matter. Therefore, it was suggested that FA could completely displace chicken manure in improvement in acidic soil in vegetable greenhouse.

Conventional flooding irrigation causes an overuse of nitrogen fertilizer and low nitrogen use efficiency in intensively used solar greenhouse vegetable production

In China, fertilizer nitrogen input is three to five times greater than vegetables require during typical intensively managed solar greenhouse vegetable production, causing a large loss of nitrogen (N) and contaminating groundwater. Excessive N input may result from flooding irrigation, a conventional practice of Chinese vegetable growers. To test this hypothesis a six-season field experiment was carried out, examining two production models (conventional flooding irrigation with over-fertilization and drip irrigation with optimizing fertilization) with and without straw application. Tomato yield, nitrate residues, nitrate leaching, nitrogen and water use efficiency, apparent nitrogen loss, and the soil organic carbon content were measured. Compared to conventional flooding irrigation model, tomato yield was increased by 9% with drip irrigation model, while the inter-annual variation of yield decreased significantly. Nitrate leaching and apparent nitrogen loss also diminished substantially. Fertilizer N and water inputs were reduced by 78% and 43%, respectively, demonstrating an improvement in water and nitrogen use efficiency with drip irrigation. Straw application had a marginal effect on both systems. Soil organic carbon slightly increased during the six growing seasons while soil nitrate leaching decreased. These results demonstrate that without the improvement of irrigation systems, it will be hard sustaining an intensively used solar greenhouse vegetable production system.

Health Risk Assessment of Heavy Metals in Soils and Vegetables from a Typical Greenhouse Vegetable Production System in China

ABSTRACTThere is growing concern about food safety and environmental contamination due to potential health risks to consumers. The aims of this study are to elucidate the accumulation status, influencing factors, and potential risk of selected heavy metals in soils and vegetables from a typical greenhouse vegetable production system in China. The potential health risks of heavy metals through soil contact and vegetable consumption were evaluated for greenhouse and corresponding open field production. The results indicated that the mean concentrations of Hg, Pb, Cu, and Zn in greenhouse vegetable soils were greater than those in open field soils. Leaf vegetables had relatively higher concentrations and transfer factors of heavy metals than root and fruit vegetables, especially for Cd. The target hazard quotient of heavy metals through vegetable consumption was greater than 1 for leaf vegetables, and was also higher for greenhouse vegetables than those from open field. The risk of exposure to heavy metals through direct contact with soil and vegetable consumption was higher for children than for adults and seniors. Planting patterns with different vegetable types and soil properties can affect bioavailability and crop accumulation of heavy metals.