Supported by the National Natural Science Foundation of China (No. 41877023), the Agriculture Science and Technology Innovation Fund of Jiangsu Province, China (Nos. CX(20)2003 and CX(21)1009)
【Objective】Soil fertility is significantly influenced by plough layer thickness. However, it is still not clear how the transformation and fate of fertilizer nitrogen (N) in fluvo-aquic soils would be affected by plough layer thickness. 【Method】In this study, a soil column simulation experiment in the field was conducted throughout three crop cultivations. The experiment was performed in a completely randomized design with six treatments including two plough layer thicknesses (15 and 25 cm) and three soil textures (sandy loam, sandy clay loam and loamy clay). A 15N-labeled tracer technique was used to evaluate the dynamics of fertilizer-derived organic N, fixed NH4+ and mineral N in 0-40 cm soil layer and the fate of fertilizer N in soil-crop systems. 【Result】 The transformation of fertilizer N in soil-crop systems was significantly affected by plough layer thickness, and showed the same varying tendency among different textural soils. The residual fertilizer N existed mainly in the form of organic N, which accounted for more than 83% of the total residual fertilizer N and played a pivotal role in the storage and supply of fertilizer N. Increasing plough layer thickness degraded the conversion of fertilizer N to fixed NH4+ pool, while increased the stocks of fertilizer-derived organic N in 0-40 cm soil layer. In the current season after fertilizer N was applied, the average value of fertilizer-derived organic N stock in soils with 25 cm plough layer thickness (PLT-25) was averagely 8.9% higher than that in soils with 15 cm plough layer thickness (PLT-15). The stocks of fertilizer-derived mineral N under PLT-25 treatments were also higher than that under PLT-15 treatments in the current and subsequent crop cultivations; promoting the fertilizer N uptake by crops. The N use efficiency under PLT-25 treatments in the first two crop cultivations was about 8.0% higher than that of PLT-15 treatments, while the current seasonal loss rate and cumulative loss rate of fertilizer N were 12.3% and 9.1% lower, respectively. The stocks of fertilizer-derived organic N in sandy clay loam and loamy clay were significantly (P < 0.05) higher than that in sandy loam, while the trend was the opposite for the stocks of fertilizer-derived fixed NH4+. And the fertilizer-derived mineral N stock was usually to be higher in sandy loam. Overall, the percentage of recovery of applied fertilizer N in crops and soil under sandy loam treatment was significantly (P < 0.05) lower than that in sandy clay loam and loamy clay. Also, the percentage of cumulative loss of fertilizer N in sandy loam was 20.4% and 18.2% higher than that in sandy clay loam and loamy clay, respectively. 【Conclusion】The fluvo-aquic soils with higher sand content have lower fertilizer N storage capacity, restricting the enhancing of N use efficiency. For fluvo-aquic soils with different textures, increasing plough layer thickness could improve the annual N use efficiency and the residual amount of applied fertilizer N in the current season. This, could be released for crop uptake in the subsequent crop cultivation. In typical fluvo-aquic soil areas, increasing the plough layer thickness may be a potential means for regulating the transformation and fate of applied fertilizer N, increasing fertilizer N retention, enhancing the fertilizer N uptake by crops and minimizing fertilizer N loss in soil-crop systems.
DING Shijie, YANG Wenliang, XIN Xiuli, ZHANG Xianfeng, ZHU Anning, YANG Jiao, REN Guocui, LI Mengrou. Effects of Plough Layer Thickness on the Transformation and Fate of Fertilizer Nitrogen in Fluvo-aquic Soils with Different Textures[J]. Acta Pedologica Sinica,2023,60(6):1688-1699.Copy