土壤剖面基础性质差异对农田水氮过程和作物产量的影响

Effects of Soil Profile Basic Properties on Water and Nitrogen Movement and Crop Yield

【目的】华北平原地区是中国最重要的冬小麦和夏玉米生产基地,不同农田土壤基础性质差异是造成该地区农田生产力空间变异的基本原因。通过研究该地区冲积始成土冬小麦-夏玉米轮作农田土壤剖面性质对水氮过程以及作物产量形成的影响,以期为该地区高产农田的水氮利用与管理提供参考。【方法】选取位于山东省泰安市研究区3块具有不同土壤基础性质且产量存在显著性差异的农田,进行3年田间试验,测定土壤剖面的土壤基本性质,具体包括机械组成、饱和导水率、田间持水量、永久萎蔫点、有机碳、全氮;监测土壤剖面0—160 cm的水分和硝态氮的动态变化以及作物生物量、叶面积指数和产量等。运用根区水质模型(RZWQM)对各农田的水氮过程进行模拟计算。【结果】RZWQM模型在整体上可以很好地模拟2009年10月至2012年9月3年不同基础土壤性质农田水分、无机氮、作物产量、地上部生物量和叶面积动态特征,并计算各农田水氮平衡项。各农田土壤基础性质差异对水氮过程及产量形成的影响具体为:高产农田0—160 cm剖面的最大有效贮水量为223 mm,分别高出中产和低产农田28和56 mm,同时30 cm深度以下土层具有相对较低的饱和导水率。该基础性质差异使得高产农田年均水分损失(地表径流+深层渗漏)仅为150.3 mm,分别低于中产和低产农田5.7和26.4 mm,从而使高产农田作物受到相对低的水分胁迫。高产农田土壤表层土壤有机碳含量较中低产田高,而碳氮比则较低,使得高产农田具有更高的净矿化氮量(较中产和低产农田高52.0和82.6 kg·hm-2),且较低的氮损失(氨挥发+氮淋洗+反硝化作用),较中产和低产农田分别少6.9和10.9 kg·hm-2。高产农田的水分利用效率(WUE)为2.32 kg·m-3,分别较中产和低产农田高12.1%和6.8%,这是因为高产农田受到较低的氮素胁迫。在本研究区不同土壤基础性质农田的氮素利用效率(NUE)差异不显著。【结论】在华北平原冬小麦-夏玉米轮作区,理想的土体构型能够存储更多的有效水,高土壤有机碳含量和低的碳氮比能矿化出更多的无机氮,保障了充足的水氮供应,减缓作物受到的水氮胁迫,从而获得高产。

[Objective]The North China Plain （NCP） is one of the major winter wheat and maize production areas in China. Spatial variance of soil basic properties is one of the main reasons for the spatial variance in the grain yield. This study was carried out in order to quantify the effects of soil profile basic properties differences on water and nitrogen movement and crop yield in the farmland with the soil type of Alluvial Cambisols, and crop system of winter wheat and maize rotation in the NCP. Results of the study will give some suggestions on promoting grain yield, water and nitrogen use efficiency in NCP. [Method]Three plots of field in Tai’an, Shandong Province with different soil profile basic properties and yield levels were selected as the three treatments andconsistent field management strategies were applied in these fields. The soil profile properties such as soil particle size distribution, saturated hydraulic conductivity （Ks）, field water capacity （FC）, permanent wilting point （PWP）, soil organic carbon （SOC） and soil total nitrogen （TN）, soil moisture and nitrate content at the 0-160 cm soil profile, crop growth and grain yield were measured for three years. The water and N movement and balance were simulated using the Root Zone Water Quality Model （RZWQM）.[Result]The dynamic of soil moisture, nitrate content, grain yield, aboveground biomass and LAI between Oct 2009 and Sep 2012 was precisely simulated by RZWQM, water and nitrogen balance was got from the model. The effects of basic soil properties on soil water and nitrogen movement, and yield was as follows： The maximum soil available moisture in 0-160 cm depth in the high yield field was 223 mm, which was 28 mm and 56 mm higher than the values in the intermediate yield field and low yield field, respectively. The saturated hydraulic conductivity at the ＆gt;30 cm soil layers in the high yield field was lower than the values in the intermediate yield field and low yield field. These basic property differences resulted in the water loss （runoff ＋ drainage） in the high yield field （150.3 mm） was 5.7 mm and 26.4 mm less than the intermediate yield field and low yield field. Thus less water stress occurred in most of time in the high yield field. The soil organic carbon and C﹕N ratio in the high yield field was higher than intermediate and low yield fields which resulted in higher organic matter mineralization rate （52.0 kg·hm^-2 and 82.6 kg·hm^-2 higher than the values in intermediate yield field and lower yield field）. The nitrogen loss （ammonia volatilization ＋ leaching ＋denitrification） in high yield field was 6.9 kg·hm^-2 and 10.9 kg·hm^-2 less than the values in the intermediate yield field and low yield field. Thus less nitrogen stress occurred in most of time in high yield field. The water use efficiency （WUE） in the high yield field was 2.32 kg·m^-3, which was 12.1% and 6.87% higher than the values in the intermediate yield field and low yield field, respectively. That was caused by less nitrogen stress in the high yield field. There was no significant difference in nitrogen use efficiency （NUE） in the fields with different basic properties in this study.[Conclusion]The soil basic properties such as higher soil profile available water moisture, superior profile saturated hydraulic conductivity distribution, higher soil organic carbon and lower C﹕N ratio can promote water and nitrogen supply, decrease water and nitrogen loss. The farmland in the crop system of winter wheat and maize rotation in NCP with these soil basic properties suffers less water and nitrogen stress, and thus leading to high yield.