Vegetable Production Systems Research Articles

Organic amendment increases soil respiration in a greenhouse vegetable production system through decreasing soil organic carbon recalcitrance and increasing carbon-degrading microbial activity

Purpose: Recent works have shown that fertilization has an important influence on soil respiration (Rs); however, the underlying mechanisms involved in regulating Rs in greenhouse vegetable production (GVP) systems remain unclear. Materials and methods: Samples from six kinds of soils that were amended with different fertilization patterns (8 years) were incubated for 36 days to determine soil microbial community (PLFA), enzyme activities, soil organic C (SOC) quality (13C NMR), and Rs in a GVP system in Tianjin, China. Treatments included 100% chemical N (CN) and different substitution rates of CN with manure-N and/or straw-N. Results and discussion: Compared with 100%CN treatment, organic amendment strongly promoted microbial (e.g., fungi, bacteria, and actinomycetes) growth, enhanced the majority of C-degrading enzyme activities, affected SOC chemical composition with increasing O-alkyl (labile) C and reducing aromatic (stable) C, decreased SOC recalcitrance, and enhanced Rs. Redundancy analysis indicated that variations in microbial community and SOC chemical composition were closely linked to light fraction organic C (LFC) and readily oxidizable C (ROC), respectively. Further, structural equation modeling and linear regression analysis revealed that SOC recalcitrance (negative effects) and C-degrading enzyme activities (positive effects) together mediate Rs rates; meanwhile, microbial community can indirect affect Rs rates through altering C-degrading enzyme activities. Conclusions: Agricultural soil abiotic properties (mainly labile C fractions, i.e., LFC and ROC) are altered by adding organic resources (i.e., manure and straw), the changes of which can promote soil microbial growth, enhance C-degrading microbial activity, and reduce SOC recalcitrance, and in turn accelerate Rs in GVP systems.

Soil salinity control and cauliflower quality promotion by intercropping with five turfgrass species

Greenhouse vegetable production contributes 60% of the economic value of the world vegetable industry. However, the secondary soil salinization and nitrate accumulation in vegetable products have become critical concerns in greenhouse vegetable production system. Here we show that cauliflower intercropped with five turfgrass species not only reduces the salinity stress and nitrate accumulation of cauliflower but also improves cauliflower curd quality. Effect of soil salinity control and cauliflower nitrate reduction was associated with the capacity of salt and nitrate uptake and accumulation of turfgrass species. Paspalum vaginatum performed the most significant effects on soil salinity control, reduced 37.8% of nitrate content, increased 50.7% of vitamin C and 21.1% of soluble protein contents in cauliflower curd. Our results demonstrated that intercropping with Paspalum vaginatum could provide a significant help for the sustainable development in the intensive greenhouse vegetable production.

GHG mitigation from sewage effluents: C sequestration after reuse in different urban cropping systems

ABSTRACTLarge volumes of greenhouse gases (GHGs) are emitted during conventional treatment of sewage. On the other hand, sewage reuse may enhance biomass production, improve soil carbon sequestration and carbon balance. Therefore, the carbon balance in plant biomass and soils was assessed in 8-year long experiment where food grain (FGPS), fodder (FPS), vegetable (VPS) and agro-forestry (AFS) production systems were irrigated either with sewage (SW) or groundwater (GW), along with the application of varying doses of N and P (25–100% of the recommended). The build-up in soil organic carbon (SOC) was 41–69% of that added through SW. The maximum annual increment in SOC occurred with AFS (1.59 Mg ha−1) followed by FPS (1.13 Mg ha−1), VPS (0.89 Mg ha−1) and FGPS (0.77 Mg ha−1). The total carbon stocks accumulated in soils and plant biomass, in terms of CO2 equivalence, were 33.4–39.8, 41.4–45.7, 35.6–41.6 and 14.5–18.4 Mg ha−1 year−1 for FGPS, AGFS, FPS and VPS, respectively, while those accumulated with 50–75% NP under SW irrigation were similar to 100% NP fertilizers under GW. These were equal to the GHGs released daily during conventional treatment of 0.42–1.06, 0.50–1.24, 0.44–1.09 and 0.20–0.48 million liters of sewage.

Life cycle assessment of fruit and vegetable production in the Region of Murcia (south-east Spain) and evaluation of impact mitigation practices

The Region of Murcia (south-east Spain) is a world-leading agricultural producer which exports 2.5 million tonnes of fruit and vegetables per year. It holds a leading position in international sales of many fresh products including lettuce, broccoli, lemon, melon and artichoke. However, the sustainability of this highly profitable business is in the spotlight as concerns mount regarding environmental exhaustion caused by intensive farming. To gain a more objective perspective, we present the first quantification of the environmental impacts of the fruit and vegetable production systems in this region using a “cradle-to-gate” life cycle assessment. We provide standard measurable values of resource depletion; acidification and eutrophication hazards; global warming potential; and use of water resources. Once the crops and agricultural stages in critical need of intervention are identified, we propose and evaluate mitigation strategies to curb their impact.Our results show that in general woody crops have bigger footprints than vegetable crops, as they usually demand higher amounts of energy, pesticides, fertilisers and water, for considerably lower yields. Nonetheless, a turnabout in the carbon footprint was observed when CO2 fixation, which is commonly not included in Life Cycle Assessments (LCAs), was accounted for. This is due to the fact that woody crops, despite having higher emissions, are more efficient carbon sinks. When analysing impacts per agricultural stage, our results add more weight to the growing body of LCA-based evidence that irrigation, field work operations and fertiliser production have the most detrimental impacts. The most promising impact-mitigation action was the replacement of mineral fertiliser with manure, which offered potential footprint reductions of up to 10% and 21% for vegetable and woody crops, respectively. For woody crops, moderate impact reductions (up to 6% without a decline in yield) can also be achieved with deficit irrigation, which can be applied in synergy with mulching or organic fertilising. Finally, we compared our results against previous studies and highlighted comparability limitations, such as the inter-annual productivity fluctuations and the wide variability in agricultural practices.

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.

Impact of Nitrogen Fertilizer on Yield and Associated Revenues in No-tillage Pumpkin

The use of no tillage (NT) integrated with cover cropping is a management practice that is becoming more popular with commercial ‘jack-o-lantern’ pumpkin (Cucurbita pepo) growers in the eastern and midwestern United States, although little is known about nitrogen (N) fertilizer requirements for this production system. A field study was established at the Southern Illinois University Horticulture Research Center in Carbondale to evaluate the yield response of pumpkin and associated revenues to N fertilization in a NT production system after wheat (Triticum aestivum) harvest. Nitrogen application rate affected pumpkin leaf chlorophyll content, and resulting yields and revenues. At all sampling dates, pumpkin fertilized with 224 kg·ha−1 N had the greatest leaf chlorophyll content. Quadratic relationships best described pumpkin fruit size and diameter increase with N rates from 0 to 224 kg·ha−1. Furthermore, pumpkin fruit number and weight per hectare also increased in a quadratic manner, as N application rates increased from 0 to 224 kg·ha−1. The application of 168 kg·ha−1 N also provided high yields and large fruit sizes, although quadratic models indicated that maximum net revenues for NT pumpkins were achieved with 224 kg·ha−1 N. Growers applying 224 kg·ha−1 N would increase net revenues by ≈54%, 52%, and 51% at pumpkin fruit price points of $0.33, $0.44, $0.55 per kg, respectively, compared with 0 kg·ha−1 N fertilization. An additional 123 kg·ha−1 N from fertilizer was required for NT pumpkin production after wheat harvest in fields with high amounts of cereal straw residues on the soil surface compared with the 101 kg·ha−1 N recommended for conventional tillage systems with no cover crop residues. This study suggests that N fertilizer investments will provide significant monetary returns in NT pumpkin systems. However, the 168 kg·ha−1 N rate provided the highest return on fertilizer investment at all pumpkin pricing points compared with all other N rates evaluated. Additionally, pumpkins grown in NT systems using a winter grain crop that is ended at flowering should require similar N amounts, because little N is used during heading and grain ripening. Although growers often look for ways to reduce input costs in vegetable production systems, N fertilization is clearly an important investment that provides increased yields and revenues in NT pumpkins. The results of this study should provide additional information to establish N fertilizer recommendations for NT pumpkin production.

Strategies to mitigate nitrate leaching in vegetable production in China: a meta-analysis.

Nitrate leaching is a main nitrogen (N) loss pathway in vegetable production. Although there are numerous mitigation practices that control nitrate leaching, an integrated assessment of these measures is lacking. Thus, we conducted a meta-analysis to integrate the assessment of strategies for controlling nitrate leaching from vegetable systems in China. The main strategies included improved N fertilizer management (INFM), reduced water management (RWM), comprehensive regulation of N fertilizer and water management (CFWM), and catch crops (CCs). Each mitigation measure decreased nitrate leaching significantly and did not reduce vegetable yields. CFWM reduced nitrate leaching the most at 41% on average, followed by CCs, RWM, and INFM (35%, 24%, and 22%, respectively). The nitrate leaching scaled yields (NLSY, defined as yield divided by the quantity of nitrate leaching) were significantly increased by 87%, 44%, 32%, and 27% for CFWM, CCs, INFM, and RWM, respectively. The efficacies of the strategies were dependent on soil properties. CFWM, INFM, and RWM were more effective in soils with low pH and coarse texture than in other soils. In conclusion, the risk of nitrate leaching from vegetable production systems is high, and INFM and CFWM are suggested to decrease nitrate leaching from vegetable production.

Evaluation of the sustainability of four greenhouse vegetable production ecosystems based on an analysis of emergy and social characteristics”

The use of emergy to evaluate the sustainability of greenhouse systems leads to management recommendations to increase the sustainability of production in these systems. In this study, four greenhouse systems for cucumber, tomato, bell pepper, and eggplant production, located in Jiroft city, Iran, were evaluated using emergy sustainability indices. To accomplish this study, 56, 31, 19, and 12 greenhouses were selected for cucumber, tomato, bell pepper, and eggplant production, respectively. Analysis of twelve emergy indices and a study of the social characteristics of the producers using Analytic Hierarchy Analysis showed that the sustainability of the cucumber production system was greater than that of the other three systems. The calculated unit emergy values for economic yield (UEVE) generally indicated that greenhouse systems were at least 100 times more sustainable than open farm systems for the production of different products, primarily because of drastically reduced soil erosion. The highest (5.10E+04 sej J−1 [4.96E+04, 5.25E+04]) and lowest (7.27E+03 sej J−1 [7.09E+03, 7.45E+03]) UEVE values were calculated for the bell pepper and cucumber systems, respectively. Also, cucumber producers had greenhouses with larger areas compared to the greenhouses used for the other crops examined in this study. The physiological characteristics of cucumber plants resulted in greater sustainability of this system, because the plants were able to capture more of the free renewable energy, had a higher production potential, and this production system made more efficient use of the workforce. In contrast, the highest proportion of purchased non-renewable resources reduced the sustainability of the eggplant production system compared to the other systems studied. Therefore, selection of a plant with more potential to use free local environmental energy, higher yield, and more efficient use of labor will lead to greater sustainability of greenhouse vegetable production systems. Sustainability can also be increased by paying attention to the socio-technical characteristics of the producers, the use of technologies to reduce non-renewable inputs to the greenhouse building, and by reducing the proportion of non-renewable inputs used overall.

Effect of Manure and Urea Fertilization on Yield, Carbon Speciation and Greenhouse Gas Emissions from Vegetable Production Systems of Nigeria and Republic of Benin: A Phytotron Study

Fertility management techniques being promoted in sub-Saharan Africa (SSA) seek to grow indigenous vegetables economically and sustainably. This study was conducted in a phytotron chamber and compared yield, soil carbon (C) speciation and greenhouse gas (nitrous oxide (N2O) and carbon dioxide (CO2)) emissions from SSA soils of two ecoregions; the dry savanna (lna, Republic of Benin) and rainforest (Ife, Nigeria) cultivated with local amaranth (Amaranthus cruentus) under manure (5 t/ha) and/or urea (80 kg N/ha) fertilization. Vegetable yield ranged from 4331 kg/ha to 7900 kg/ha in the rainforest, RF, soils and 3165 kg/ha to 4821 kg/ha in the dry savanna, DS, soils. Yield in the urea treatment was slightly higher compared to the manure, and manure+urea treatment, but the difference was not statistically significant. Cumulative CO2 emissions over 21 days ranged from 497.06 to 579.47 g CO2-C/kg soil/day in the RF, and 322.96 to 624.97 g CO2-C/kg soil/day in the DS, while cumulative N2O emissions ranged from 60.53 to 220.86 mg N2O-N/kg soil/day in the RF, and 24.78 to 99.08 mg N2O-N/kg soil/day in the DS. In the RF samples, when compared to the use of urea alone, the combined use of manure and urea reduced N2O emissions but led to an increase in the DS samples. ATR-FTIR analysis showed that the combined use of manure and manure+urea increased the rate of microbial decomposition in the soils of the DS, but no such effect was observed in soils of the RF. We conclude that combining manure and urea fertilization has different effects on soils of the two ecoregions, and that RF farmers can reduce agricultural N2O emissions without compromising soil productivity and yield potential.

Substitution of manure for chemical fertilizer affects soil microbial community diversity, structure and function in greenhouse vegetable production systems.

Soil microbial communities and enzyme activities together affect various ecosystem functions of soils. Fertilization, an important agricultural management practice, is known to modify soil microbial characteristics; however, inconsistent results have been reported. The aim of this research was to make a comparative study of the effects of different nitrogen (N) fertilizer rates and types (organic and inorganic) on soil physicochemical properties, enzyme activities and microbial attributes in a greenhouse vegetable production (GVP) system of Tianjin, China. Results showed that manure substitution of chemical fertilizer, especially at a higher substitution rate, improved soil physicochemical properties (higher soil organic C (SOC) and nutrient (available N and P) contents; lower bulk densities), promoted microbial growth (higher total phospholipid fatty acids and microbial biomass C contents) and activity (higher soil hydrolase activities). Manure application induced a higher fungi/bacteria ratio due to a lower response in bacterial than fungal growth. Also, manure application greatly increased bacterial stress indices, as well as microbial communities and functional diversity. The principal component analysis showed that the impact of manure on microbial communities and enzyme activities were more significant than those of chemical fertilizer. Furthermore, redundancy analysis indicated that SOC and total N strongly influenced the microbial composition, while SOC and ammonium-N strongly influenced the microbial activity. In conclusion, manure substitution of inorganic fertilizer, especially at a higher substitution rate, was more efficient for improving soil quality and biological functions.

Non-Chemical Weed Management in Vegetables by Using Cover Crops: A Review

Vegetables are a substantial part of our lives and possess great commercial and nutritional value. Weeds not only decrease vegetable yield but also reduce their quality. Non-chemical weed control is important both for the organic production of vegetables and achieving ecologically sustainable weed management. Estimates have shown that the yield of vegetables may be decreased by 45%–95% in the case of weed–vegetable competition. Non-chemical weed control in vegetables is desired for several reasons. For example, there are greater chances of contamination of vegetables by herbicide residue compared to cereals or pulse crops. Non-chemical weed control in vegetables is also needed due to environmental pollution, the evolution of herbicide resistance in weeds and a strong desire for organic vegetable cultivation. Although there are several ways to control weeds without the use of herbicides, cover crops are an attractive choice because these have a number of additional benefits (such as soil and water conservation) along with the provision of satisfactory and sustainable weed control. Several cover crops are available that may provide excellent weed control in vegetable production systems. Cover crops such as rye, vetch, or Brassicaceae plants can suppress weeds in rotations, including vegetables crops such as tomato, cabbage, or pumpkin. Growers should also consider the negative effects of using cover crops for weed control, such as the negative allelopathic effects of some cover crop residues on the main vegetable crop.

Winter cover crops increase readily decomposable soil carbon, but compost drives total soil carbon during eight years of intensive, organic vegetable production in California.

Maintaining soil organic carbon (SOC) in frequently tilled, intensive organic vegetable production systems is a challenge that is not well understood. Compost and cover crops are often used to add organic matter to the soil in these systems. Compost contributes relatively stabilized carbon (C) while cover crops provide readily degradable (labile) organic matter. Our objectives were to quantify C inputs, and to assess the effects of urban yard-waste compost, winter cover crop frequency and cover crop type on SOC and labile C stocks during eight years of intensive, organic production that usually included two vegetable crops per year in a long-term systems study in Salinas, California. Total C inputs from pelleted fertilizer, compost, vegetable transplant potting mix, vegetable residue and cover crops, including estimates of below ground inputs, ranged from 40 to 108 Mg ha-1 in the five systems evaluated. Following a rapid decline in SOC stocks in year 1, compost had the largest effect on SOC stocks increasing mean SOC over years 2 to 8 by an average of 9.4 Mg ha-1, while increased cover crop frequency (annual vs. quadrennial) led to an additional 3.4 Mg ha-1 increase. In contrast, cover cropping frequency had the largest effect on permanganate oxidizable labile C (POX-C), increasing POX-C by 26% after 8 years. Labile POX-C was well correlated with microbial biomass C and nitrogen. Compost had the greatest effect on total SOC stocks, while increasing cover crop frequency altered the composition of SOC by increasing the proportion of labile C. These results suggest that frequent winter cover cropping has a greater potential than compost to increase nutrient availability and vegetable yields in high-input, tillage intensive vegetable systems.

Relationship between macropores and soil organic carbon fractions under long‐term organic manure application

AbstractGreenhouse vegetable production systems converted from cereal fields often experience a decrease in soil aeration due to intensive land use. Organic fertilization is a method commonly used to solve this problem. Although previous studies have considered soil organic carbon (SOC) or soil pores under organic cultivation, the relationship between SOC fractions and soil macropores is unknown. This study analysed the long‐term progressive variations in soil macropore (>50 μm) and SOC fraction characteristics in organic greenhouse vegetable plantations (1‐year‐old, 9‐year‐old, and 14‐year‐old fields) converted from rice–wheat rotation fields and established the relationship with X‐ray computed tomography scanning and 13C solid‐state nuclear magnetic resonance spectroscopy. The results suggested that the total macroporosity increased from 7.95% to 16.36% throughout the whole organic plantation, and a similar trend occurred in small (50–500 μm) and medium (500–1,000 μm) macroporosity. Besides, the total SOC content and the contents of its fractions increased with organic planting time. With the total macroporosity exhibiting significant associations with SOC (r = .81**), the relative proportion of O–alkyl C (r = −.94**), and the relative proportion of aromatic C (r = .89**), a lower O–alkyl C proportion of SOC might help to increase macroporosity. A similar relationship was found between the relative proportion of SOC fractions and the macroporosity. The O–alkyl C proportion had significantly negative relations with aromatic C (r = −.94**) and SOC (r = .84**). Overall, both SOC and its fractions can help to improve soil macroporosity, but the effects of different fractions on these pores vary.

Long term crop management effects on soil organic carbon, structure, and water retention in a cropland soil in central Ohio, USA

AbstractThe objective of this study was to determine 13‐year management effects on soil properties between a corn–soybean (Zea mays–Glycine max) cropping system (CSRS) and vegetable production systems (VPS) on a soil in central Ohio. Three treatments included in the VPS were: (1) addition of wood chips, (2) permanent raised beds (PRB) with black polyethylene film (20 μm thick), and (3) bare soil surface (BSS). Additionally, (4) animal manure was applied in all CSRS and VPS treatments except for the wood chips (WCP) added plot in the VPS. Research data from the study show that relatively more soil organic carbon (SOC) stock in the 0–20 cm soil depth of the BSS treatment (100.6 Mg ha−1) was primarily due to differences in the type of soil amendments applied. For example, composted poultry manure was applied in the BSS and PRB plots, compared with input of fresh dairy manure mixed with straw being applied in the CSRS. Furthermore, soil management practices that aided in avoiding or reducing soil compaction (i.e., PRB or application of WCP in the surface) resulted in the overall improvement in soil structure and water retention, compared with that under chisel and disc ploughing done in the CSRS. The highest plant available water capacity (1.79 cm) was observed in the CSRS compared with 0.97 cm under BSS and PRB plots. These trends suggest that the type and amount of animal manure is critical to increasing SOC stocks in intensively cultivated VPS and CSRS in central Ohio, while also improving soil structure and water retention.

Design of a control system for a mini-automatic transplanting machine of plug seedling

In China, vegetable production system has been dominated by small and medium-sized agricultural facilities over the open-field cultivational practices. Low ceiling height and narrow width are dimensional attributes associated with most of these facilities. Due to these dimensional parametric constraints, the application of available field transplanting machinery in such facilities is a problematic subject which leads the vegetable growers towards manual transplanting. In order to meet the needs of small and medium-sized agricultural facilities for automatic vegetable transplanting, a smaller size wireless remote-controlled automatic transplanting machine was designed, which can transplant seedlings quickly in the greenhouse and by considering the stainability of environment electric power was adopted to drive all the mechanisms. In the process of agricultural production, the control system of agricultural machinery plays an important role in the degree of automation of mechanical equipment. Therefore, this paper focuses on the design of the control system of the newly premeditated automatic transplanting machine. The hardware of the control system is separated into three portions: the sensors for signal acquisition, the programmable controller for signal processing, and the driving elements for specific actions. PLC (Programmable logic controller) is adopted as the central control system of the transplanting machines which controls the automatic movement of seedlings tray carrier, seedlings extraction and feeding, and seedlings transmission to the planting units automatically. In order to control the overall movement of seedling transplanting machine, a microcontroller is adapted to control the hub and steering motor. The key driving elements of the control system are solenoid valves and electric motors which controls the action of pneumatic air cylinders and linear movement of different parts of machine respectively. The overall software design of the control system is accomplished, together with coordinated motion between components, control flow design and control program writing. In order to test the motion coordination of each component and the rationality of the control system of the Mini-Automatic transplanting machine, different planting frequencies were set to record the success rate of seedling collection and transplanting. The results of the trials exhibited that at the planting frequencies of 40, 50 and 60 plants/row/min the overall success rates were noted 98.6%, 97.2% and 96.5% respectively. It shows that the key parts of the transplanting machine are synchronized in motion, accurate in positioning, reasonable in assembling the control system and stable in operation, which meets the requirements of transplanting seedlings in the dry land.

Using pXRF to assess the accumulation, sources, and potential ecological risk of potentially toxic elements in soil under two greenhouse vegetable production systems in North China.

Intensive greenhouse vegetable production (GVP) has increased the pollution risk of potentially toxic elements (PTEs) in soils. This study examined the accumulation, sources, and potential ecological risk of six PTEs (Cu, Zn, As, Ni, Pb, and Cr) in soil under two GVP (solar greenhouse (SG) and round-arched plastic greenhouse (RAPG)) systems by portable X-ray fluorescence spectroscopy (pXRF) and conventional laboratory analysis. The results indicated that all PTE concentrations were lower than their corresponding thresholds in GVP soils, presenting a low potential ecological risk in both GVP soils according to risk indices (RI ≤ 40.67). As, Ni, Pb, and Cr were not significantly accumulated in both GVP soils. Although Cu and Zn accumulated in both GVP soils, their accumulation extents in SG soil were both greater than that in RAPG soil. Cu and Zn were mainly originated from anthropogenic activities based on multivariate statistical analysis, which were greatly associated with excessive manure application. Overall, pXRF can identify the accumulation difference of PTEs between the two GVP soils, which is generally consistent with conventional laboratory analysis. Hence, pXRF can be a promising alternative to conventional laboratory analysis for rapid assessment of PTEs accumulation, sources, and the potential ecological risk in the two GVP soils. Although PTEs had a low ecological risk, Cu and Zn accumulation in SG soil was increased with the planting years. Therefore, rational application of livestock manure containing high levels of Cu and Zn should inspire strategies to mitigate the environmental risk in GVP soils, especially in SG soil.

Conventional flooding irrigation and over fertilization drives soil pH decrease not only in the top- but also in subsoil layers in solar greenhouse vegetable production systems

Conventional flooding irrigation combined with over-fertilization in intensively used solar greenhouse vegetable production systems are jeopardizing soil productivity and groundwater quality due to soil acidification and nitrogen (N) leaching. While it has been shown that excessive application of N fertilizer in greenhouse production systems significantly reduces topsoil pH values, it remains unknown if also subsoil pH values do change too and if surplus N fertilization and hydrological N losses lead to nutrient imbalances. In this study, soil samples from six soil layers from 0 to 300 cm were taken from 45 greenhouse fields with three representative cultivation years (2, 5, and 10 years). Soil samples from 5 adjacent corn fields served as comparison. Results show that (1) compared to soils from adjacent corn fields, the pH in the 0–30 cm soil layer was slightly elevated two years and five years after greenhouse establishment, but was lowered by 0.52 ± 0.06 units after ten years. Moreover, also the pH in deeper soil layers (30–300 cm) significantly decreased with cultivation years. (2) A significant imbalance of N:P:K ratios in greenhouse top soils was found, as P and K accumulates while N is leached to subsoils. (3) Structural equation modeling indicated that changes in the mineral N concentration in the 0–30 cm soil layer was driving soil pH changes. Our results demonstrate that N accumulation in top soils and N leaching to deep soil caused by excessive irrigation explains observed declines in surface and deep soil pH values of conventional greenhouse vegetable production systems. Consequently, for avoiding groundwater contamination with N and for ensuring sustainable soil productivity, current schemes of irrigation and fertilization management need to be adapted to avoid N leaching, soil acidification, nutrient accumulation and imbalances.

Molecular Scale Studies of Phosphorus Speciation and Transformation in Manure Amended and Microdose Fertilized Indigenous Vegetable Production Systems of Nigeria and Republic of Benin

This study investigated the speciation, transformation, and availability of P during indigenous vegetable production by employing a combination of chemical and spectroscopic techniques. The study focused on sites in two ecozones of SSA, the dry savanna (lna, Republic of Benin) and rainforest (Ilesha, Nigeria). Both sites were cultivated with two indigenous vegetable species: local amaranth (Amaranthus cruentus (AC)) and African eggplant (Solanum macrocarpon (SM)). The soils were treated with 5 t/ha poultry manure and urea fertilizer at the rates of 0, 20, 40, 60, and 80 kg N/ha. Soil samples were collected before planting and after harvest. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy was used to determine P speciation in these soils. Quantitative analysis showed that adsorbed and organic P were the two dominant P species in the manure amended dry savanna (DS) soils before planting and after harvest in soils cultivated with both AC and SM, with the addition of urea (40 kg N/ha) causing an increase in the organic P form in dry savanna soils cultivated with AC. Soils of the rainforest (RF) cultivated with AC initially had large amounts of apatite P in the manure amended soils prior to planting, which was transformed to adsorbed and organic P after harvest. Urea addition to the rainforest soils shifted the dominant P species from organic P to adsorbed and apatite P, which was likely to limit P availability. Soils cultivated with SM had similar proportions of both organic and adsorbed P forms, with 40 kg N/ha addition slightly increasing the proportion of adsorbed P.

Coconut shell derived biochar to enhance water spinach (Ipomoea aquatica Forsk) growth and decrease nitrogen loss under tropical conditions

Farms usually apply excessive nitrogen (N) fertilizers, especially in a vegetable production system, resulting in severe N leaching loss. Although there have been some reports on the impact of biochar on the N leaching in farmlands, most of them focused on field crops in temperate or subtropical religions. Limited information about N leaching in the tropical vegetable system is available regarding the quantitative data and effective countermeasures. A field experiment was conducted to quantify N leaching in a tropical leafy production system (Ipomoea aquatica Forsk) and to evaluate the effects of coconut shell biochar on N loss and crop growth. The results showed that compared to conventional fertilization with the 240 kg N ha−1 application rate (NPK), biomass yield of water spinach increased by 40.1% under the high biochar application rate of 48 t ha−1 (HBC), which was significantly higher than that of NPK treatment. Moreover, The HBC treatment decreased N leaching by 34.0%, which can be attributed to enhanced crop uptake which increased by 40.3% as compared to NPK treatment. The NH4+/NO3− ratio in leachates was between 0.01 and 0.05. It was concluded that coconut shell derived biochar improved the biomass yields of water spinach and reduced the leaching N loss, which provides a promising amendment in tropical regions.

Study of engineering properties of selected vegetable seeds

Quality seed is the foundation block of vegetable production system. Proper post-harvest processing of seed is important to maximize yield, longevity, vigour, and overall quality. The engineering properties determination is the first and foremost step for the design of any seed processing, storage and handling machine or equipment. Engineering properties like geometric, gravimetric, frictional and aerodynamic properties of bottle gourd, sponge gourd, garden pea, and radish seeds have been determined at different levels of moisture content (7.5 % to 19 % dry basis). Results revealed a quadratic increase in all properties with moisture content except for gravimetric properties. The properties like sphericity (0.83), bulk density (710.61 kg/m3), true density (1109.79 kg/m3), angle of repose (26.41°), terminal velocity (10.13 m/s) and drag coefficient (0.92) were highest for garden pea seeds. Whereas, bottle gourd seeds exhibited maximum values for size (7.17 mm), projected area (115.68 mm2), porosity (53.4%) and coefficient of friction (0.727).