Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK.
Division of Agricultural & Environmental Science, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, Loughborough, LE12 5RD, UK.
Sci Rep. 2020 Mar 19;10(1):5072. doi: 10.1038/s41598-020-61986-0.
Leaching of nitrate from fertilisers diminishes nitrogen use efficiency (the portion of nitrogen used by a plant) and is a major source of agricultural pollution. To improve nitrogen capture, grasses such as brachiaria are increasingly used, especially in South America and Africa, as a cover crop, either via intercropping or in rotation. However, the complex interactions between soil structure, nitrogen and the root systems of maize and different species of forage grasses remain poorly understood. This study explored how soil structure modification by the roots of maize (Zea maize), palisade grass (Brachiaria brizantha cv. Marandu) and ruzigrass (Brachiaria ruziziensis) affected nitrate leaching and retention, measured via chemical breakthrough curves. All plants were found to increase the rate of nitrate transport suggesting root systems increase the tendency for preferential flow. The greater density of fine roots produced by palisade grass, subtly decreased nitrate leaching potential through increased complexity of the soil pore network assessed with X-ray Computed Tomography. A dominance of larger roots in ruzigrass and maize increased nitrate loss through enhanced solute flow bypassing the soil matrix. These results suggest palisade grass could be a more efficient nitrate catch crop than ruzigrass (the most extensively used currently in countries such as Brazil) due to retardation in solute flow associated with the fine root system and the complex pore network.
从肥料中淋滤出的硝酸盐会降低氮的利用效率（植物利用的氮的比例），并且是农业污染的主要来源。为了提高氮的捕获能力，人们越来越多地使用象臂形草这样的草作为覆盖作物，无论是间作还是轮作，尤其是在南美洲和非洲。然而，土壤结构、氮和玉米以及不同饲用草根系之间的复杂相互作用仍知之甚少。本研究通过化学穿透曲线来探讨玉米（Zea maize）、象草（Brachiaria brizantha cv. Marandu）和狼尾草（Brachiaria ruziziensis）根系对硝酸盐淋滤和保留的影响，研究发现所有植物都增加了硝酸盐的传输速率，这表明根系增加了优先流的趋势。象草产生的细根密度较大，通过 X 射线计算机断层扫描评估的土壤孔隙网络的复杂性增加，微妙地降低了硝酸盐淋滤的潜力。狼尾草和玉米中的较大根系占主导地位，通过增强绕过土壤基质的溶质流增加了硝酸盐的损失。这些结果表明，象草可能比目前在巴西等国家广泛使用的狼尾草（Brachiaria ruziziensis）更有效地作为硝酸盐截获作物，因为与细根系和复杂的孔隙网络相关的溶质流延迟。
