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Zinc, as one of the essential microelements in crop plant, plays a crucial role in resistance to drought stress.

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Purpose Vegetable production is one of the most intensive agricultural systems with high rates of nitrogen (N) fertilizer use and irrigation, conditions conducive for nitrate (NO 3 − ) leaching, and nitrous oxide (N 2 O) emissions. The objective of this study was to determine the effectiveness of a nitrification inhibitor, dicyandiamide (DCD), in decreasing NO 3 − leaching and N 2 O emissions in vegetable production systems. Materials and methods Twenty-four undisturbed soil monolith lysimeters (610 mm in diameter; 700 mm in depth; surface area, 0.29 m 2 ) with two different soils, Huangzongrang (alfisol) and Chaotu (fluvisols), were collected and installed in a field lysimeter facility in Central China under irrigated vegetable production conditions. Urea fertilizer was applied at 650 kg Nha −1 , and DCD was applied at 10 kg ha −1 to the lysimeters planted with three kinds of vegetables (capsicum, Capsicum annuum L.; amaranth, Amaranthus mangostanus L.; radish, Raphanus sativus L.). Results and discussionThe results showed that DCD reduced NO 3 − leaching by 58.5% and 36.2% and N 2 O emissions factor by 83.8% and 72.7% in the two soils. The average NO 3 − -N concentration in the drainage water was decreased from 4.9 mg NL −1 to 2.3 mg NL −1 and from 4.4 mg NL −1 to 3.3 mg NL −1 , in the Huangzongrang and Chaotu soils, respectively. In addition to the environmental benefits, the use of DCD also increased the yields of capsicum and radish in alfisol soil significantly (P<0.01); only the amaranth yield in fluvisol soil was declined (P<0.01), and the other vegetables yields were not affected. Total N concentrations of the three vegetables were increased significantly (P<0.01) with the application of DCD with urea compared with urea alone. These results showed that the nitrification inhibitor DCD has the potential to significantly reduce NO 3 − leaching and N 2 O emissions and to make vegetable farming more environmentally friendly.Conclusions These results demonstrated that the use of the nitrification inhibitor DCD can significantly reduce NO 3 − leaching, N 2 O emissions, and the average NO 3 − -N concentration in the drainage water, while increasing the fertilizer N efficiency in the vegetable production system.

Background, aim, and scope Nitrate leaching from intensive vegetable production is an important contributor of nitrate contamination of water resources. The aim of this study was to quantify NO 3 − leaching losses under intensive vegetable production as affected by different rates of N fertilizer and to determine the optimum N application rates both for vegetable production and for meeting the drinking water standard. Materials and methods Twelve undisturbed soil lysimeters (590 mm diameter and 650 mm depth) were collected and installed in a field lysimeter facility in Central China to study nitrate leaching from a clay loam soil (alfisol) under irrigated vegetable production conditions. Urea was applied at 0 kg N/ha (N0), 370 kg N/ha (N1), 1,110 kg N/ha (N2), and 1,480 kg N/ha (N3) to the lysimeters planted with vegetables. Nitrate leaching losses and vegetable yields were measured for five vegetables [capsicum (Capsicum annuum L.), amaranth (Amaranthus mangostanus L.), radish (Raphanus sativus L.), Chinese cabbage 1 (Brassica chinensis L.), and Chinese cabbage 2), with rotations lasting a total of 13 months.Results The results showed that NO 3 − -N leaching losses were significantly affected by urea-N application rates, increasing from 32.8 to 63.3, 227.1, and 353.7 kg N/ha in the N0, N1, N2, and N3 treatments, respectively. These leaching losses represented 8.2%, 17.5%, and 21.7% of the total N applied, respectively. The average NO 3 − -N concentration in the drainage water ranged from 3.7 to 43.1 mg N/L. Only the NO 3 − -N concentrations of the control and N1 treatment were below the drinking water standard (10 mg N/L). Plant N removal accounted for 38.3%, 29.7%, and 22.9% of total N applied in the N1, N2, and N3 treatments, respectively. The N application rates for maximum yield, 90% maximum yield, and for meeting the drinking water standard (10 mg N/L) were 1,098.4, 699.5, and 445.2 kg N/ha, respectively. Discussion These results showed that the intensive vegetable production systems with high N fertilizer application rates and irrigation have a high NO 3 − leaching potential.Both the N application rates for optimum economic yield and for meeting the drinking standard were much lower than those often used by local farmers pursuing excessively high yields.Recommendations and perspectives The optimum fertilizer N application rate should be set as that which would not result in the NO 3 − -N concentration in the leachate above the drinking water standard. This rate is often lower than that for 90% maximum production.Vegetable production in China has increased significantly over the past two decades, with land area used for vegetable J Soils Sediments (