西南黄壤菜田镁的淋洗损失及纳米镁肥的阻控效应

In recent years, the magnesium (Mg) deficiency problem on vegetables in yellow soils in southwest China has been of increasing severity. The severe Mg leaching may be the main reason accounting for this phenomenon, unfortunately, rare studies have concentrated on the quantitative analysis of Mg leaching on such soil. This project aims to quantify the Mg leaching of yellow soil through field trials and soil column simulated experiments. Based on the Mg demand of vegetables and rainfall distributions, dynamic Mg leaching will be precise quantified. The dynamic equilibrium between exchangeable Mg, water-soluble Mg and mineral Mg in soil was analyzed, and the composition and concentration of Mg in the soil transformation process were determined. Accordingly, we attempt to prepare a new type Nano-Mg fertilizer, and reveal the functional mechanism of the Nano-Mg fertilizer on preventing Mg leaching from soils by comparing with the rapid and slow available Mg fertilizer. The dynamic process of adsorption and desorption of Nano-Mg fertilizer particles in soil was monitored in situ. The effect of Nano-Mg fertilizer in satisfying the needs of Mg in vegetables and preventing Mg from leaching in soils will be tested in a pepper-cabbage rotation system. The implementation of this project will provide foundation theoretical basis and technical support for the related research of solving Mg deficiency in yellow soils and vegetables in southwest China.

西南黄壤蔬菜缺镁问题近年来日趋严重，制约蔬菜产量和品质的提高。土壤镁淋洗可能是导致该区域缺镁的关键因素，但关于黄壤上镁淋洗的定量化系统研究尚未见报道。本项目拟通过田间原位监测和室内土柱模拟试验，首先定量化西南地区黄壤菜田的镁淋洗量，并从周年轮作蔬菜系统镁的吸收规律和周年降雨分布动态两个方面解释镁淋洗动态特征；其次，解析土壤交换态镁与水溶态镁、矿物态镁之间吸附、解吸和固定、释放的动态平衡，明确镁肥施入土壤后转化过程中赋存形态的变化；然后引入新型纳米镁肥，对比速效和缓效镁肥，原位监测纳米镁肥颗粒在土壤中吸附、解吸的动态过程，揭示纳米镁肥阻控土壤镁淋洗的机制，并在辣椒-白菜轮作系统中田间验证其在保障蔬菜镁需求的同时降低镁的淋洗的效果。本研究将为解决西南地区黄壤镁淋洗、蔬菜镁缺乏问题提供理论和技术支撑。

西南地区酸性土壤上蔬菜缺镁（Mg）问题近年来日趋严重，土壤镁淋洗严重可能是该区域缺镁的关键因素。但关于西南典型酸性土壤对镁淋洗的定量化监测较少。在阻控土壤养分淋洗方面，纳米肥料因其比表面积相对较大，吸附能力强，因而具有不易淋失、易被植物吸收的特点，但目前纳米镁肥在土壤中的转化、吸收和损失过程研究较少。本项目在田间条件下，首先利用田间原位淋洗测定装置明确了西南辣椒-大白菜轮作系统的镁素淋洗损失及平衡，辣椒和大白菜季土壤镁素淋失范围分别为20.7-46.0 kg ha-1和5.88-11.5 kg ha-1，镁淋洗量较大。基于优化产量和维持系统镁素平衡的施肥策略，西南黄壤上露地蔬菜系统的适宜施镁量为：辣椒季和大白菜分别需要62.1和21.8 kg Mg ha-1。同时，项目引入多种新型镁肥（纳米氢氧化镁、改性纳米氢氧化镁、磷酸铵镁），与传统硫酸镁对比，通过大田试验探究不同新型镁肥对西南地区典型辣椒-白菜蔬菜轮作系统生长发育的影响及其环境效应，并通过盆栽试验定量化不同类型镁肥淋洗损失，评价其生物有效性。初步揭示纳米肥料抗淋洗能力较强，其原因是由于其土壤颗粒间净作用力较大。研究还评价了蔬菜供应的镁营养对人体健康的影响。本研究为解决西南地区土壤镁淋洗、蔬菜镁缺乏问题提供理论和技术支撑。