Maize genotypes regulate the feedbacks between maize nitrogen uptake and soil nitrogen transformations

Abstract

Maize (Zea mays L.) genotypes can directly affect gene expression and nitrogen (N) uptake capacity. However, the feedback between maize genotypes and soil gross N transformations, and their regulations on N uptake capacity are not well known. So, 15N tracing pot experiments were conducted in an acidic soil and an alkaline soil with six maize genotypes, i.e. Dika 007 (DK), Zhengda 999 (ZD1), Zhengdan 958 (ZD2), Jingke 968 (JK), Longdan 339 (LD), Liangyu 99 (LY). Maize N uptake and soil gross N transformation rates were quantified by the Ntraceplant tool to identify feedbacks between maize genotypes N uptake and soil N transformations and their mechanisms. Maize total N uptake rates (UTN) varied among genotypes and soils. UTN in alkaline soil was 1.1–2.1 times higher than that in acidic soil. NH4+ and NO3− uptake rates (UNH4 and UNO3, respectively) were regulated by specific N transport genes in acidic soil, supported by positive relationships between N uptake rates and relative expression of ZmNRT1.1, ZmNRT1.2 and ZmAMT1.1A genes. UTN, and UNO3 were positively correlated to soil gross N mineralization (M), and autotrophic nitrification (ONH4) rates, respectively. However, maize inhibited M compared to treatment without maize plantation (CK) due to effects on soil microbial community, and based on random forest analysis, the declined relative abundance of Acidicaldub, Gonytrichum and Nigrospora in acidic soil, Taeniolella in alkaline soil may cause the decrease of M by the presence of maize. Meanwhile, maize inhibited ONH4 to increase NH4+ residence time, which in turn was responsible for the positive relationship between UNH4 and ONH4. In contrast, the stimulation of heterotrophic nitrification (ONrec) by plants improved the NO3− availability. The maize genotypes, such as JK, could largely enhance N uptake by regulating the expression level of N transport genes in maize and stimulating soil N transformation to produce more inorganic N (Nmin) in the different soils. Our findings show that maize genotypes play a central role in regulating these feedbacks. These results are important for maize breeding and enhancing maize production.