Intensive Vegetable Production Research Articles

Assessing sustainability in smallholder vegetable farms in Benin Republic: A matrix approach

This study aims to assess the level of sustainability in vegetable-based agrifood production systems in Benin and to propose actions to enhance sustainability, food safety, and year-round production in the vegetable production systems. Semi-structured interviews were conducted with 200 vegetable farmers in contrasting agroecological areas (with areas of extensive production of staples and intensive production of vegetables), using the “Indicateur de Durabilité des Exploitations Agricoles” (IDEA) framework (an on-farm sustainability index). Most of the surveyed vegetable farmers produced a wide range of crops, including leafy vegetables (amaranth, African eggplant, and African basil) and peppers, grown by more than 50% of the farmers. The average scores achieved by the vegetable farms regarding three dimensions of sustainability—ecological, social, and economic—were 35, 41, and 63, respectively, out of a maximum score of 100. All three sustainability dimensions of the vegetable farms were, on average, at a low level and improvements were needed for them to reach an acceptable standard. The vegetable farms located in the south of Benin had, on average, a higher sustainability score than those in the north: around 50% of vegetable farms in the south had a medium score, while the sustainability level of almost 75% of vegetable farms in the north was low. Interventions seeking to improve the sustainability of vegetable farms in Benin should focus on the promotion and adoption of eco-responsible practices that improve on-farm biodiversity, water conservation, and the effective allocation and management of land and labor, to mitigate the environmental impacts of vegetable production.

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

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

Optimizing organic fertilization towards sustainable vegetable production evaluated by long-term field measurement and multi-level fuzzy comprehensive model

Precision and efficient management of organic substitution fertilization is crucial in balancing soil health, environmental risks, and economic benefits for intensive crop cultivation. However, effectively determining the optimal organic substitution ratio in vegetable production remains uncertain and still relatively unexplored. We conducted a five-year vegetable field experiment and established four nitrogen-equivalent fertilization treatments: mineral fertilizer alone, and organic fertilizer substituting a quarter, half, and entirety of the mineral nitrogen. Employing a specialized multi-level fuzzy comprehensive evaluation model, our study assessed impacts of different organic substitution ratios on soil qualities, microbial diversity, vegetable yield and quality, environmental risks, and economic benefits in sustainable vegetable production of eastern China. Our results showed that the 50% organic substitution was optimal, significantly improving soil qualities and microbial characteristics, particularly in the topsoil layer. Compared to the control, this approach significantly reduced methane by 6.6–48.3%, nitrous oxide by 49.5–79.1%, and nitric oxide by 36.5–50.0%, while enhancing vegetable yield by 16.0–28.3% and its five-year average stability as well as quality as evidenced by increased protein, soluble sugar, and vitamin C contents. Economic analysis revealed that while it maximized environmental benefits, complete organic substitution did not consistently yield positive economic returns. In contrast, a 50% substitution ratio was identified as the most economically viable, representing a sustainable compromise that balances environmental health with economic feasibility. Further modeling analysis indicated an optimal comprehensive range between 42.9% and 64.5% for achieving the best balance of multiple objectives in vegetable fields. The study underscores the intricate organic substitution effects on intensive vegetable production, highlighting the necessity for tailored organic substitution strategies that integrate environmental sustainability with agricultural productivity and economic practicality.

Pesticide Residue and Bio-pesticides in Vegetable Crops

Intensive vegetable production using pesticides has biggest threat to growers and the consumers. In such instances the accumulation of pesticide residues is increased due to relatively short pre-harvest interval. Use of pesticides without knowing the label claim information increases the cost of production, increases the number of spray and labour cost, ultimately leading to decrease in farmers profitability. Hence, the adoption of pesticide as per label claim is very much essential. The level of residues should be below the maximum residue limit (MRL) at the time of harvest. Most of the detected pesticides in vegetables are not registered by Central Insecticide Board and Registration committee (CIBRC) for use on that specific vegetable which is the off label use of pesticides. Crops grouping is the development of a model that allows extrapolation of residue data from a few representative crops to many other crops in the same group. This allows establishment of residue tolerances for the entire group of crops based on the residue values from certain key crops that are similar. The acceptance of representative crop is a critical component of the savings from using the crop groups. IR-4’s involvement with efforts to remove pesticide residues as a barrier for exports for US-grown specialty crops has been growing in importance over the last 20 years. By establishing a common MRL on a specialty crop from a particular crop protection product use, trade irritants between the two countries can be prevented before they have the potential to become a major problem for specialty crop growers on each side of the border. The U.S./Canadian specialty crop partnership has yielded valuable results for all the stakeholders involved. IR4 signed MOUs with Canada, New Zealand, Brazil, Costa Rica, and Colombia. This model is also much needed for India to regulate the pesticide label claims for numerous crops.

Machine learning-based estimation and mitigation of nitric oxide emissions from Chinese vegetable fields

High fertilizer input and nitric oxide (NO) emissions characterize the intensive vegetable production system. However, the amount, geographic distribution, and effective mitigation strategies of NO emissions over Chinese vegetable fields remain largely uncertain. In this study, we developed a data-driven estimate of NO emissions and their spatial pattern in Chinese vegetable fields based on the Random Forest (RF) model. Additionally, we conducted a field experiment in a subtropical vegetable field to investigate the effect of climate-smart practices on NO emissions. The RF model results showed that soil NO emissions from Chinese vegetable fields were sensitive to nitrogen application amount, soil clay content, and pH. The total NO emission from Chinese vegetable fields in 2018 was estimated to be 75.9 Gg NO–N. The urgency to reduce NO emissions in vegetable fields was higher in northern than in southern China. Our meta-analysis and field experiment results suggested that biochar amendment and replacing chemical fertilizers with bio-organic fertilizers were win-win climate-smart management practices for mitigating NO emissions while improving vegetable production. Overall, our study provided new insights into NO emissions in vegetable soil ecosystems and can facilitate the development of regional NO emission inventories and effective mitigation strategies. These findings highlight the importance of adopting sustainable and climate-smart agricultural practices to reduce NO emissions and mitigate their adverse environmental impacts.

Soil microbial activity improved while intensifying vegetable production by use of plant-based fertilisers, cover crops and reduced tillage

Frequent soil cultivation in intensive vegetable production is detrimental to soil quality. Combining several sustainable management techniques, such as increasing organic matter input and plant diversity, and reducing soil cultivation, could benefit biological soil quality. We designed a crop rotation with a system approach, combining plant-based fertilisers, cover crops and reduced tillage, while growing more crops (sustainable intensification, SI). We compared this approach to common practice (CP), where animal manure fertilisers, no cover crops and ploughing were employed in a standard organic crop rotation on sandy loam in Denmark. Treatments were initiated in 2017, and two sets of contrasts, each comparing across cropping systems and specific crop rotations, were investigated in the second and third year of implementation: lettuce-leek double-cropping (SI) vs. leek sole-cropping (CP), and onion-lettuce intercropping (SI) vs. lettuce-lettuce double-cropping (CP). Soil microbial activity was assessed by β-glucosidase and dehydrogenase activity and potential N mineralisation over 28-days incubation. Root growth was investigated using minirhizotrons. The risk of N leaching was estimated from soil mineral N content at 0–2.5 m depth in autumn. β-glucosidase and dehydrogenase activity increased by 27–107% under SI compared to CP in the third year after implementation. SI improved potential N mineralisation by 12–52 kg N ha−1 before and after spring fertilisation both years. Increased soil fertility under SI contributed to 1.3 to 2.3 times higher plant N uptake (except for lettuce/onion first year), and 1 to 2.7 times higher marketable yields, but only minimally affected root depth. Despite higher N fertilisation, risk of N leaching did not rise under SI. The beneficial effects of SI were attributed to the combination of higher N fertilisation (53–144 kg N ha−1 more) as organic matter addition (2–3 Mg carbon ha−1 more), growing cover crops, and reducing soil tillage. Combining these techniques is promising for improving soil microbial activity in a sustainable way for highly intensive organic vegetable production.

Organic substitutions enhanced soil carbon stabilization and reduced carbon footprint in a vegetable farm

The strategies of substituting inorganic fertilizers with organic fertilizers have been shown to significantly impact the dynamics of soil organic carbon (SOC) combating soil degradation and climate changes in intensive vegetable production. However, the underlying mechanisms and comprehensive assessment of environmental consequences are not fully understood. We conducted a five-year field experiment in the Yangtze River Delta Alluvial Plain, China, four fertilization treatments were established at equal nitrogen (N) levels: sole mineral fertilizers (SN); organic substituting 20 % (M1N4), 50 % (M1N1), and 100 % (SM) of mineral N fertilizer with organic fertilizer. Soil carbon (C) pools, physical and chemical composition of SOC, and C footprint were measured based on soil aggregates, 13C nuclear magnetic resonance spectroscopy, and life cycle assessment to investigate the effects of organic substitution on SOC quantity, quality, and environmental implications. Our results showed a significant increase in SOC content, particularly in the M1N1 treatment. This increase was attributed to changes in soil properties, an elevation in dissolved organic C content, and improved SOC stability. Specifically, organic substitution increased the proportion of macroaggregates, content of lignin phenols, and enrichment of alkyl C groups. Based on life cycle assessment incorporating field measurements, the average C footprint ranged from 1.82 to 2.58 CO2 kg eq kg−1 vegetable in the five-year experiment, primarily influenced by transportation and fertilizer manufacturing. Partial organic substitution reduced the C footprint by 6.2–10.1 %, while the SM treatment increased it by 0.54 CO2 eq kg−1 vegetable, and the M1N1 had the lowest C footprint at 1.82 CO2 eq kg−1 vegetable. As a whole, this approach of substituting 50 % of mineral N with organic fertilizers serves as a viable strategy to bolster soil C stabilization, promote C accumulation, and mitigate the C footprint linked to intensive vegetable production in subtropical regions.

Effect of Furrow Straw Mulching and Straw Decomposer Application on Celery (Apium graveolens L.) Production and Soil Improvement

Straw mulching on wet beds is an effective method to alleviate continuous cropping obstacles in greenhouses. However, this technique cannot be applied in the production of leafy vegetables with high planting density. Straw mulching in furrows is an alternative method in this circumstance. In this study, celery (Apium graveolens L.), a vegetable that prefers a high planting density and wet soil, was used to test furrow straw mulching technology, and the effect of different straw amounts and straw decomposers on soil improvement and celery production was investigated. The results showed that straw mulching in furrows significantly reduced soil conductivity and nitrate nitrogen levels, increased the contents of soil organic carbon as well as phosphorus and potassium nutrients in the bed, and improved celery yield and quality, indicating the significant lateral movement of released nutrients between the furrow and bed. The positive effects of 15,000 kg/ha straw application were more pronounced than those of 7500 kg/ha and 11,250 kg/ha. In addition, straw decomposers accelerated nutrient release and improved celery yield and quality. A decomposer named “ZhuBang” containing Bacillus licheniformis was the most effective. We concluded that furrow straw mulching combined with straw decomposer application is an effective measure for the sustainable production of leafy vegetables in intensive vegetable production facilities.

Compensation schemes for plant quarantine pest costs: A case study for Germany

Plant quarantine pests worldwide cause considerable economic damage due to direct plant losses, eradication costs, and contamination measures. Although these losses can threaten the survival of a farm, no country to date has a universal compensation solution that encompasses all agricultural sectors. This paper aims to assess various compensation options by, firstly, calculating potential monetary losses caused by selected quarantine pests, which have not been studied in this context before. Secondly, we calculate farmers’ willingness to pay (WTP) for different components of compensation options in plant production using a discrete choice experiment (DCE). We find that monetary losses caused by quarantine pests vary significantly across products and sectors and are highest for intensive vegetable production. The DCE reveals a strong preference for the state compensation and heterogeneity of preferences among farmers depending on their experience with risk management options and perception of pest occurrence. The WTP analysis indicates that requiring preventive plant protection measures as a prerequisite for receiving compensation significantly deters farmers from participating in such a system, as its WTP exhibits the most negative impact compared to all other factors. Due to sectoral differences and path-dependent nature of compensation programs, a universal solution is rather not feasible. Sector-specific solutions must be considered, which does not rule out similar compensation approaches among sectors. Our findings are useful for designing compensation programs for quarantine plant pest cases.

Intensive vegetable production under plastic mulch: A field study on soil plastic and pesticide residues and their effects on the soil microbiome

Intensive agriculture relies on external inputs to reach high productivity and profitability. Plastic mulch, mainly in the form of Low-Density Polyethylene (LDPE), is widely used in agriculture to decrease evaporation, increase soil temperature and prevent weeds. The incomplete removal of LDPE mulch after use causes plastic contamination in agricultural soils. In conventional agriculture, the use of pesticides also leaves residues accumulating in soils. Thus, the objective of this study was to measure plastic and pesticide residues in agricultural soils and their effects on the soil microbiome. For this, we sampled soil (0–10 cm and 10–30 cm) from 18 parcels from 6 vegetable farms in SE Spain. The farms were under either organic or conventional management, where plastic mulch had been used for >25 years. We measured the macro- and micro-light density plastic debris contents, the pesticide residue levels, and a range of physiochemical properties. We also carried out DNA sequencing on the soil fungal and bacterial communities. Plastic debris (>100 μm) was found in all samples with an average number of 2 × 103 particles kg−1 and area of 60 cm2 kg−1. We found 4–10 different pesticide residues in all conventional soils, for an average of 140 μg kg−1. Overall, pesticide content was ∼100 times lower in organic farms. The soil microbiomes were farm-specific and related to different soil physicochemical parameters and contaminants. Regarding contaminants, bacterial communities responded to the total pesticide residues, the fungicide Azoxystrobin and the insecticide Chlorantraniliprole as well as the plastic area. The fungicide Boscalid was the only contaminant to influence the fungal community. The wide spread of plastic and pesticide residues in agricultural soil and their effects on soil microbial communities may impact crop production and other environmental services. More studies are required to evaluate the total costs of intensive agriculture.

Assessment of fertilization strategies and policy measures for vegetables by simulation of a long-term cauliflower leek rotation

As the larger part of the residual soil nitrate in late autumn leaches out during the wet winter months, some regions monitor these residues to convince farmers to adopt improved fertilisation practices in order to reduce nitrate pollution. However, the reduction of the nitrate concentration in the surface and groundwater remains limited, especially in regions with intensive vegetable production. Soil-based advisory systems are recommended to reduce nitrate leaching, but it is unclear if this is sufficient to meet the EU nitrate directives. The objectives of this study were to assess localized fertilizer placement, soil-based fertilization, soil-based fertilizer recommendations and nitrate monitoring policies using a simulation with historical weather data. For this purpose, the ECOFERT model was proposed, a pseudo-2D expansion of the WAVE model to simulate the heterogeneity of vegetable root development. The model was calibrated and validated for a cauliflower-leek rotation on three-year experimental data. The results show that a soil-based advisory system reduces nitrate leaching and residual soil nitrate while maintaining similar biomass production levels compared to a fixed high fertilisation rate. However, in most simulated cases, the fertilisation advice was still too high to meet the legal limits of 50 mg NO3 l-1 in the percolated water or 85 kg N ha-1 residual soil nitrate in autumn. This was attributed to considerable mineralisation and crop N-uptake variability caused by weather variation compared to fixed values. The simulations identified the potential of localised N-application and soil-based advisory systems but also showed some weaknesses. This will allow researchers to improve N-advisory systems to reduce nitrate pollution.

Effect of cultivar on measurements of nitrate concentration in petiole sap and leaf N content in greenhouse soil-grown cucumber, melon, and sweet pepper crops

Excessive N fertilizer applications in intensive vegetable production in soil is commonly associated with appreciable N losses causing negative environmental impact. Measuring petiole sap [NO3−‒N] and leaf N content (%) are simple and practical monitoring methods to assess crop N status for improving N fertilizer management. The effect of cultivar on petiole sap [NO3−‒N] and leaf N content was evaluated. One cucumber, two melon, and two sweet pepper crops were grown in different cropping periods, with three cultivars in each crop. Three N treatments, deficient (N1), sufficient (N2) and excessive (N3) N supply, were applied by combined fertigation with drip irrigation. For a given N supply, there were often significant differences between cultivars in petiole sap [NO3−‒N] and leaf N content in cucumber, the two melon crops and one pepper crop. This was, particularly so with the sufficient (N2) and excessive (N3) N supply. In the cucumber and two melon crops, there were consistent differences in petiole sap [NO3−‒N] between cultivars in two or three of the different N treatments. In some crops, very little petiole sap [NO3−‒N] was measured with deficient (N1) N supply. In the two pepper crops, the differences between cultivars were less clear than with cucumber and melon. In general, for the three species examined, petiole sap [NO3−‒N] was subject to more consistent and larger effects between cultivars, than was leaf N. Average differences between cultivars in petiole sap [NO3−‒N] of 200‒450 mg NO3−‒N L−1 were observed during periods of 4‒6 weeks in cucumber and melon. The differences between different cultivars of the same species in petiole sap [NO3−‒N] and leaf N content, when receiving the same N supply, has implications for the practical applications of these methods for monitoring crop N status.

Optimized Nitrogen Fertilizer Rate Can Increase Yield and Nitrogen Use Efficiency for Open-Field Chinese Cabbage in Southwest China

Intensive vegetable production has been characterized by high nitrogen (N) fertilizer input in southwest China. Optimizing the N fertilizer rate is the basis for the optimal management of regional N fertilizer. A two-year field experiment with five N fertilizer rates was conducted during 2019–2021 in southwest China, and the aim of this study was to identify the effects of different N application rates on yield, dry matter biomass (DMB), N uptake, N use efficiency (NUE) and soil mineral N (Nmin) residues for Chinese cabbage (Brassica chinensis L.) and further determine the critical plant N concentration and root-zone soil Nmin residues required to reach the maximum DMB of Chinese cabbage. Five N treatments were established: control without N input (CK); optimal N fertilizer rate decreased by 30% (70% OPT, 175 kg N ha−1), optimized N fertilizer rate (OPT, 250 kg N ha−1), optimal N fertilizer rate increased by 30% (130% OPT, 325 kg N ha−1) and farmers’ N fertilizer practice (FP, 450 kg N ha−1). The N source in all treatments was conventional urea (N ≥ 46.2%). The results showed that the total yield of Chinese cabbage followed a “linear-plateau” trend with an increasing N fertilizer rate. There was no significant difference in yield between the OPT, 130% OPT and FP treatments. The aboveground plant DMB and N uptake showed a ‘slow-fast-slow’ pattern with the growth period. There was no significant difference in aboveground plant DMB and N uptake between the OPT, 130% OPT and FP treatments. Moreover, the OPT treatment significantly increased the aboveground plant DMB and N accumulation by 29.6% and 40.5%, respectively, compared with the 70% OPT treatment. The OPT treatment significantly increased the NUE by 23.8%, 31.2% and 43.1% compared with that in the 70% OPT, 130% OPT and FP treatments, respectively. The linear-plateau model provided the best fit for the relationship among aboveground DMB of Chinese cabbage, plant N concentration and root-zone soil Nmin content. The critical root-zone soil Nmin and plant N concentrations were 94.1, 63.4 and 68.3 kg ha−1 and 34.4, 33.5 and 32.9 g kg−1 during the rosette, heading and harvest periods, respectively. In summary, compared to the FP treatment, the optimized N fertilizer rate (250 kg N ha−1) could significantly reduce the N application rate, maintain yield, increase aboveground plant DMB and N uptake, and improve NUE. Moreover, the study has great significance for guiding the green utilization of vegetable N fertilizer in southwest China.

Current tomato production practices and their effects on plant and soil carbon and nitrogen dynamics

Assessment on how current standard tomato production impacts plant and soil C and N dynamics is necessary to improve sustainable nutrient management strategies for the intensive production of vegetables in warm climates. Carbon (C), nitrogen (N) and C:N ratios were determined for tomato variety ‘BHN 602’ (Solanum lycopersicum) in spring and fall season at harvest, in north Florida. A replicated field study was conducted where tomatoes were grown in sandy soils with fertilizers injected through the drip irrigation lines under a plastic-mulched bed system. Ammonium nitrate as the N source was applied at four different rates (0, 168, 224, and 280 kg ha−1). Soluble N fertilizer was applied weekly in 13 equal doses through the drip system for both seasons. Whole plant C:N ratios were similar among N rates in both spring and fall applications showing that the lowest applied N rate (168 kg ha−1) was sufficient in supplying N to the crop. Therefore, fertilized whole plant C:N ratios of 15.2 (spring) and 13.8 (fall) indicated optimal N uptake capability by the tomato crop. Soil TC and TN concentrations were maintained in the top 0-45 cm increments of the soil profile in both seasons, where concentrations did not differ among the rates of N fertilizer applied. Due to the lack of fertilizer input response, the reduction of N fertilizer rates would improve the sustainability of conventional vegetable production systems that are grown in sandy soil under a warm climate. Soil C was commensurate with soil N levels with regard to stabilizing the C:N ratio below 20, thus promoting mineralization in the soil for the subsequent crop.

Nonlinear effects of biochar on greenhouse gas emissions and soil microbial community composition under intensive vegetable production in South China

Biochar amendment in agroecosystems is proposed to mitigate the greenhouse (GHG) emissions and enhance multiple ecosystem services. However, it remains unclear whether and how various biochar amendment rates can influence soil microbial communities linking with GHG mitigation. In a two-year field experiment with five biochar amendment rates (0, 10, 20, 30 and 40 Mg ha−1), we determined cumulative GHG emissions, soil physiochemical properties and soil microbial community composition base one total phospholipid fatty acids (PLFA) under intensive vegetable production from Ultisols in southern China. Results showed that biochar amendment significantly decreased cumulative N2O emissions by 40–66 % during the whole study period (p < 0.01), whereas effects on CH4 emissions were inconsistent across the two study years. In addition, biochar amendment significantly decreased PLFAs and fungi/bacteria ratio by 4–31 % and 12–39 %, respectively. Annual global warming potential (GWP) was effectively reduced by biochar amendment, and random forest analysis showed that soil pH, C/N, humic acid (HA) and fungal PLFAs exhibited the highest mean predictor importance. The nonlinear correlations between the biochar amendment rate and GHG emissions mainly caused by soil pH, and the 20 Mg ha−1 biochar amendment rate was recommended because it produced the lowest GWP with the lowest economic costs. These findings demonstrated that various biochar amendment rates can differently alter GHG emissions and microbial properties under intensive vegetable production, which can provide new insights on optimal biochar amendment rates for GHG mitigation in agricultural production in China.

Optimizing nitrogen and water management for sustainable greenhouse vegetable production with less greenhouse gas emissions

Intensive greenhouse vegetable production is considered a major source of greenhouse gas emissions and ammonia volatilization in China because the overuse of nitrogen (N) fertilizers is extremely common. Therefore, the emissions of nitrous oxide (N2O), carbon dioxide (CO2), and ammonia (NH3) from five different fertilizer treatments (conventional practice (CN) and four reduced N rate treatments (synthetic fertilizer, combined without (RN1) or with a nitrification inhibitor (3,4-dimethypyrazole phosphate, DMPP) (RN1 +DMPP), and a mixed application of synthetic and organic fertilizers, combined without (RN2) or with straw (RN2 +S))) were determined during a tomato and melon rotation. The results showed that the CN treatment had high total emissions of N2O (9.81 ± 0.81 kg N ha−1 yr−1) and CO2 (6.43 ± 0.75 kg C ha−1 season−1), which were 2.1–6.5 times and 1.2–1.91 times greater than those of other reduced N treatments, respectively. The annual direct N2O emission factor of the CN treatment was 0.94 %, which was higher than that of the reducing N treatments. The RN1, RN2 and RN2 +S treatments significantly (p < 0.05) decreased NH3 volatilization. The RN1 +DMPP treatment significantly (p < 0.05) increased NH3 volatilization in comparison with the RN1 treatment; however, it reduced the net global warming potentials (GWP) due to decreasing both N2O and CO2 emissions. Reducing the N application rate did not compromise vegetable yields in comparison with the CN treatment, but it significantly decreased the yield-scaled N2O emissions (p < 0.05). The combination of synthetic fertilizer and manure significantly (p < 0.05) increased N2O emissions relative to synthetic fertilizer alone. Compared to the other treatments, the RN1 +DMPP treatment significantly reduced the net GWP. Therefore, RN1 +DMPP is a better practice to reduce greenhouse gas emissions and simultaneously maintain crop yield in intensive vegetable production.

The Extension of Vegetable Production to High Altitudes Increases the Environmental Cost and Decreases Economic Benefits in Subtropical Regions

Global warming has driven the expansion of cultivated land to high-altitude areas. Intensive vegetable production, which is generally considered to be a high economic value and high environmental risk system, has expanded greatly in high-altitude mountainous areas of China. However, the environmental cost of vegetable production in these areas is poorly understood. In this study, pepper production at low (traditional pepper production area) and high (newly expanded area) altitudes were investigated in Shizhu, a typical pepper crop area. The output and environmental cost at the two altitudes were identified. the influence of resource inputs, climate, and soil properties on pepper production was evaluated. There were obvious differences in output and environmental cost between the two altitudes. High-altitude pepper production achieved a 16.2% lower yield, and had a higher fertilizer input, resulting in a 22.3% lower net ecosystem economic benefit (NEEB), 23.0% higher nitrogen (N) footprint and 24.0% higher carbon (C) footprint compared to low-altitude farming. There is potential for environmental mitigation with both high- and low-altitude pepper production; Compared to average farmers, high-yield farmers groups reduced their N and C footprints by 16.9–24.8% and 18.3–25.2%, respectively, with 30.6–34.1% higher yield. A large increase in yield could also be achieved by increasing the top-dress fertilizer rate and decreasing the plant density. Importantly, high-altitude pepper production was achieved despite less advanced technology and inferior conditions (e.g., a poor road system and uneven fields). It provides a reference for the study of the environmental cost of other high-altitude regions or other crop systems at high-altitude areas.

English

Irrigated vegetable production is an important agricultural activity and a significant source of income for millions of smallholder farmers in the Sahel. There is little information on the potential effects of intensive vegetable production using African Market Garden (AMG) technology on vegetable yields and soil chemical properties. Three contiguous 500-m2 plots were established to evaluate three vegetable management practices: (1) AMG, (2) Improved Management (IM), and (3) Farmer Practice (FP). These management practices were arranged in a randomized block design. AMG and IM management practices produced higher yields as compared to farmer practices. Tomato and onion yield for IM were 50 and 300% higher than for AMG, respectively; while yields for FP were consistently lower. The soil chemical properties at the end of the experiment displayed marked changes in all treatments compared to the initial soil status. Except for pH, which decreased by 0.2, 0.4, and 1.1 pH units, respectively, for FP, IM, and AMG, soil chemical properties increased as a direct response to management practices. These findings indicate that regular and high rates of manure application combined with mineral fertilizer enhance sandy soil fertility in the Sahel. These findings are important for developing sustainable vegetable production in the Sahel. Key words: Vegetable production, Drip irrigation, Farmer&rsquo;s practice, Productivity, Soil fertility.

Scalable coupled aquaponics design: Lettuce and tilapia production using a parallel unit process approach

Coupled aquaponics is the integration of recirculating aquaculture systems (RAS) with hydroponic cropping systems (HCS) into a single system with shared water treatment units. Potential benefits of integration include water conservation, reduced reliance on finite mineral fertilizers, and intensive year-round location-independent production of lean proteins and fresh vegetables. However, coupled aquaponic practitioners have found minimal commercial success to date. This has been mostly due to the use of system designs which are not based on contemporary water treatment principles, especially those for commercial aquaculture. Instead, conventional coupled aquaponic system design has been based on a linear framework assuming fish wastes are readily utilized as plant fertilizers, with minimal emphasis on waste treatment or individual component hydraulic retention times. The result has been economic failures due to misbalancing the cost of inputs, the value of the outputs, and the time required to reach a marketable harvest size for both crops: fish and plants. This manuscript provides theoretical calculations based on existing standards in commercial RAS and HCS for sizing plant, fish, and biofiltration units focused on nitrogenous waste production from fish. Successful integration of HCS and RAS is defined as achieving industry standard production timelines for lettuce (seed to harvest time of 35 days) and Nile tilapia (fry to a 624 g average harvest weight in 35 weeks). Equations and examples to calculate lettuce yield, daily lettuce nitrogen requirement, fish feed rates to achieve specific nitrogen production rates, and fish tank and biofilter volumes are provided.

Assessing nutrient budget of ungauged catchment using intermittent water quality markers

This study is a preliminary spatial-temporal assessment method of the ungauged catchment to determine the variation in water quality (WQ) and the land use influence on river basins’ health. The intermittent WQ data, the principal component analysis, and the redundancy analysis were used to evaluate the (dis)similarity among the 10 ungauged streams and their significance in the entire catchment. These revealed some similarities/differences in nutrient pollution and latent land-use influence on the streams’ health. There were similarities between R6-R7, R9-R10, among R1 to R4 basins, while R5 and R8 had distinct variances in their WQ dynamics. The intensive vegetable and rice production in R5, R7, R8, R9, and R10 basins were the major sources of high nutrient concentrations. The unique variations, especially in R5 and R8 basins could be attributed to other different pollution sources. Hence, it’s of great significance to carry out comprehensive research in the above 5 river basins. That is the efficiency of management practices, identification of pollution sources, and the extent to which the elevated nutrients in the streams interact with biota within the river regime. This research offers a method to evaluate WQ dynamics in relation to human interferences in river basins of a catchment with limited data under similar climatic conditions.