Fengqiu Agro-Ecological Experimental Station/State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science, Chinese Academy of Sciences
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)
耕层厚度是影响土壤肥力的重要因素之一，但其对潮土中化肥氮素转化的影响尚不清楚。利用田间?土柱模拟试验，采用15N示踪技术，探究在不同耕层厚度处理下，化肥氮在3种质地潮土0~40 cm土层中有机氮、无机氮与固定态铵库中的动态变化以及作物对化肥氮的吸收利用。结果表明：耕层厚度显著影响化肥氮在土壤不同氮库中的转化及其在土壤-作物系统中的去向，且在不同质地潮土中的作用效果一致。在不同质地潮土中，残留于土壤中的化肥氮83%以上以有机氮的形式存在，影响化肥氮的保蓄与供给。增加耕层厚度虽然降低了化肥氮向固定态铵库的转化，但提高了0~40 cm土层中的肥料来源有机氮储量，尤其是在施肥当季，耕层厚度25 cm（PLT-25）处理下的肥料来源有机氮储量平均较耕层厚度15 cm（PLT-15）处理提高8.9%。增加耕层厚度显著（P < 0.05）提高了施肥当季与后茬作物生长季内肥料来源无机氮的供给，在此期间PLT-25处理下作物对化肥氮的利用率较PLT-15处理提高8.0%左右，而化肥氮的当季损失率与累积损失率则较PLT-15处理分别降低12.3%与9.1%。就土壤质地的角度而言，砂粒含量高制约着化肥氮向有机氮库的转化，不利于作物对化肥氮的吸收利用，增大了氮肥损失。由此可见，在不同质地潮土中，增加耕层厚度在提高化肥氮素当季利用率的同时也增大了化肥氮在土壤中的残留量，减少了化肥氮的损失。残留的化肥氮在后茬作物生长季释放出来供作物吸收利用，促进了化肥氮累积利用率的提高。
【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 18.8% and 20.8% 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, DOI:10.11766/trxb202204060097,[In Press]