BACKGROUND: Magnesium (Mg) fertilization is a promising practice to improve vegetable yield. However, its impacts on vegetable quality and human health have not been examined. Thus, a field experiment was conducted to investigate the effects of varying Mg fertilization rates on yield and quality of pepper (Capsicum annuum L.) fruit. Furthermore, result of the field experiment was linked to pepper consumption data from the China Health and Nutrition Survey (CHNS) in the disability-adjusted life years (DALYs) framework to evaluate the potential health impact of Mg fertilization for the first time. RESULTS: Compared to control, Mg fertilization increased the 2-year average pepper yield by 25.6%, whereas there was no significant yield improvement when Mg rates exceeded 112.5 kg MgO ha −1. Magnesium application increased concentrations of Mg and capsaicinoids, decreased those of calcium (Ca), zinc (Zn) and vitamin C (Vc), and had no effect on potassium (K) and iron (Fe) in pepper fruit. As a result, Mg fertilization decreased the comprehensive nutrition level of pepper by 16.6%. Furthermore, the current health burden of the Chinese adult population associated with pepper consumption is estimated at 21.3 million DALYs per year, with the risk being increased by 5.40 DALYs for per megagram of Mg fertilizer application. Increasing health risk was mainly attributed to decreasing concentrations of Ca and Vc in pepper fruit, though the increased Mg intakes offset the impact of 1.74% to 14.4%. CONCLUSION: Magnesium fertilization significantly improved the yield but reduced nutritional quality of pepper fruit, and increased human health risks associated with consumption of pepper fruit.
Fertilization affects soil processes in many ways that remain unclear. The effects of N, P, and K application on plant growth and Cu and Pb accumulation were thus evaluated in a soil-maize system using five treatments: N, P, and K application; N and P application; N and K application; P and K application; and control (no fertilization). Compared to the control, fertilizer application treatments, especially N application, significantly increased maize photosynthetic rate, which further improved shoot biomass production. Root growth, root and shoot Cu and Pb concentrations, and Cu and Pb mobility also significantly altered with fertilizer application. Shoot Cu contents, root Cu uptake and translocation factors were significantly increased in the N-fertilized treatments. The significant decrease of shoot Pb concentration and root Pb uptake and increase of Cu and Pb immobilization were observed in the P-fertilized treatments. No significant correlation was observed between K application and Cu and Pb accumulation in maize. Our results show that an increase in P application and decrease in N application is recommended to reduce agro-ecological risks associated with Cu and Pb in soil-maize systems. However, the mechanisms governing the relationship between nutrients and heavy metal transformation in soil-plant systems needs further research.
BACKGROUND: Effective nitrogen (N) management measures are required to control environmental problems caused by N fertilizer use in intensive maize production systems. Soil N losses associated with high precipitation and over-fertilization in maize production can cause substantial environmental problems, whereas there is a lack of quantitative data and effective study countermeasures. A 2-year field study was conducted in the subtropical maize production system in Southwest China to quantify N leaching under varying N application rates of 0, 90, 180, 270 and 360 kg N ha −1 yr −1 . RESULTS: The results indicated that N leaching accounted for 16-38% of N fertilizer input. For farmer practice treatment (360 kg N ha −1 yr −1 ), N leaching loss was high at 110 kg N ha −1 yr −1 and accounted for 31% of the N applied. As an indicator of the ambient water quality pollution, the grey water footprint across all treatments ranged from 376 to 1092 m 3 Mg −1 , with an average of 695 m 3 Mg −1 . Reducing N rate to agronomically optimized treatment (180 kg N ha −1 yr −1 ) significantly decreased N leaching by 77%, and maintained high grain yield of 8.1 Mg ha −1 . The grey water footprint was reduced by 52-63% with N rates from 270 or 360 kg N ha −1 yr −1 to 180 kg N ha −1 yr −1 . CONCLUSION: Nitrogen surplus (applied N rate minus N uptake by maize) resulted in higher soil residual nitrate concentration and consequently high N leaching. High precipitation and low soil pH were the main ecological factors leading to high N leaching.
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