Effects of N fertilization and maize straw on the dynamics of soil organic N and amino acid N derived from fertilizer N as indicated by 15N labeling

Publication date: 1 July 2018
Source:Geoderma, Volume 321
Author(s): Caiyan Lu, Huaihai Chen, Zhenzhen Teng, Lei Yuan, Jian Ma, Hongbo He, Xin Chen, Xudong Zhang, Yi Shi
The accumulation and availability of soil organic nitrogen (N), especially amino acid N, is highly important for N retention in the soil and N supply for crop growth. However, it remains obscure how the conversion of fertilizer N to both soil organic N and amino acid N is affected by management practices such as fertilization and residue amendment. In present study, we conducted an outdoor ¹⁵N labeling pot experiment in Mollisols of Northeast China, where plants were consecutively cropped after each of three cultivations (spring wheat-buckwheat-spring wheat). We aimed to evaluate the effects of maize straw applications on the dynamics of organic N and amino acid N derived from fertilizer N. Six treatments were set: no N fertilization (CK), application of only maize straw (M), low N levels (N1), N1 plus maize straw (N1 + M), high N levels (N2), and N2 plus maize straw (N2 + M). The results showed that organic N and amino acid N dominated the available N derived from fertilizer N, but their contents decreased significantly as crop cultivation continued. Compared with N2, N2 + M, which involved the application of maize straw, significantly increased the content of organic N derived from fertilizer N by an average of 20.1% during the first crop cultivation. Compared with N1 and N2, N1 + M and N2 + M promoted the content of fertilizer-derived amino acid N by an average of 12.5% across five sampling dates. During the first crop cultivation, straw amendment also significantly increased both plant uptake and soil residues of fertilizer N in N1 + M and N2 + M. Our results demonstrated that substrate amendments such as crop residues may constitute a practical agricultural management approach for promoting the transformation of fertilizer N to soil organic N, thereby increasing both fertilizer N use efficiency and retention in our study crop-soil systems.