Key Laboratory of Plant-Soil Interactions, Ministry of Education, Department of Plant Nutrition, China Agricultural University, Beijing, China.
PLoS One. 2012;7(5):e37726. doi: 10.1371/journal.pone.0037726. Epub 2012 May 18.
A challenge for Chinese agriculture is to limit the overapplication of nitrogen (N) without reducing grain yield. Roots take up N and participate in N assimilation, facilitating dry matter accumulation in grains. However, little is known about how the root system in soil profile responds to various N supplies. In the present study, N uptake, temporal and spatial distributions of maize roots, and soil mineral N (N(min)) were thoroughly studied under field conditions in three consecutive years. The results showed that in spite of transient stimulation of growth of early initiated nodal roots, N deficiency completely suppressed growth of the later-initiated nodal roots and accelerated root death, causing an early decrease in the total root length at the rapid vegetative growth stage of maize plants. Early N excess, deficiency, or delayed N topdressing reduced plant N content, resulting in a significant decrease in dry matter accumulation and grain yield. Notably, N overapplication led to N leaching that stimulated root growth in the 40-50 cm soil layer. It was concluded that the temporal and spatial growth patterns of maize roots were controlled by shoot growth and local soil N(min), respectively. Improving N management involves not only controlling the total amount of chemical N fertilizer applied, but also synchronizing crop N demand and soil N supply by split N applications.
中国农业面临的一个挑战是在不减少粮食产量的情况下限制氮肥（N）的过度施用。根系吸收 N 并参与 N 同化，促进谷物干物质积累。然而，人们对根系在土壤剖面中如何响应各种 N 供应知之甚少。在本研究中，连续三年在田间条件下深入研究了 N 吸收、玉米根系的时空分布和土壤矿质 N（N(min)）。结果表明，尽管早期起始节根的生长受到短暂刺激，但 N 缺乏完全抑制了后期起始节根的生长并加速了根死亡，导致玉米植株快速营养生长阶段总根长的早期减少。早期 N 过量、缺乏或延迟 N 追肥会降低植物 N 含量，导致干物质积累和籽粒产量显著下降。值得注意的是，N 过量施入会导致 N 淋失，从而刺激 40-50 cm 土壤层的根系生长。研究结论认为，玉米根系的时空生长模式分别受地上部生长和局部土壤 N(min)的控制。改善 N 管理不仅涉及控制施入的化学 N 肥料总量，还涉及通过分期施 N 来协调作物 N 需求和土壤 N 供应。
