中国科学院水利部水土保持研究所机构知识库

摘要

肥料产业的发展促进了粮食增产，保证了粮食安全供给。由于人类持续向土地投入大量化学肥料，农业面源污染负面效应逐渐凸显，给人类生存健康带来潜在风险。未来农业向着绿色、环保方向发展，对于解决农业增产与环境的平衡问题具有重要的意义。黄土高原南部旱作农业区，土层深厚而疏松，暴雨频发，为农业面源污染提供了条件。因此，在该地区研究不同的氮肥管理措施下硝态氮的淋溶特征与阻控技术，对于提高作物产量和保护生态环境具有重要的指导意义。

本试验在黄土高原南部长武农业生态试验站进行，采用完全随机区组设计，半覆膜种植，供试作物为春玉米，品种为先玉335。设置4组试验处理，每组3个重复，分别为：（1）不同施氮量，施氮量分别为0、80、100、130、160、200、250kg/hm²；（2）总施氮200kg/hm²，设置缓控肥与普通尿素不同施用比例，比例分别为35%+65%、50%+50%、65%+35%；（3）施氮200kg/hm²时，设置硝化抑制剂不同添加浓度，分别为施氮量的1%、5%、10%、15%；（4）在施氮200、250kg/hm²的基础上，采用玉米秸秆深埋措施。在缓控肥与硝化抑制剂试验处理区，采取春玉米各生育期根层土壤，测定土壤硝态氮含量。在春玉米收获期采取土壤样品和植物样，分别测定土壤硝态氮含量和籽粒产量，以确定各种氮肥管理措施对土壤硝态氮淋溶及春玉米籽粒产量的影响。试验于2017—2018年开展2年，主要结果如下：

（1）适量的施氮量促进春玉米增产，同时可降低土壤硝态氮淋溶累积。在施氮范围0～250 kg/hm²内，春玉米籽粒产量呈现先增长后下降的趋势，经函数模拟分析，施氮为227 kg/hm²时产量可达到最大。施氮量在0～160 kg/hm²时，土壤硝态氮含量保持在较低的水平，不会引起大量淋溶累积。当施氮量超过160 kg/hm²时，淋溶至深层土壤的硝态氮显著增加，导致土层0—300累积量剧增。因此，引发土壤硝态氮淋溶累积的施氮阈值为160 kg/hm²。施氮量为200 kg/hm²时，植株总吸氮量、氮素利用效率达到最大。施氮量达到250 kg/hm²时，使春玉米籽粒产量和氮素利用效率存在一定程度降低。

（2）缓控肥的施用可有效阻控土壤硝态氮的淋溶下移，减少下层土壤硝态氮的累积。各处理中，缓控肥与普通尿素施用比例为50%+50%时，淋溶至深层的土壤硝态氮最少，对土壤硝态氮的淋溶阻控效果最佳，土层0—300cm硝态氮累积量降低37.39%。缓控肥的施用降低春玉米各生育期根层土壤硝态氮含量，各缓控肥处理之间，无明显差异。缓控肥的施用一定程度上降低了春玉米籽粒产量，主要由于缓控肥在春玉米生长前期阶段肥效释放较慢，与春玉米根系对氮素的吸收不同步，降低作物总吸氮量与氮素利用效率，进而降低产量。

（3）适量的硝化抑制剂对土壤硝态氮的淋溶下移起到有效的阻控作用，减少土层硝态氮的累积。随着硝化抑制剂添加量的增加，土壤硝态氮向深层土壤淋溶的风险系数增加，同时，土壤硝态氮的累积量有增加的趋势。硝化抑制剂添加量为施氮量的1%时，土层剖面硝态氮含量最低，土层0—300cm硝态氮累积量最低(与对照对比降低55.68%)。硝化抑制剂的施用使春玉米各生育期根层土壤硝态氮含量显著降低，不同量硝化抑制剂处理之间无显著性差异。与对照相比，添加硝化抑制剂对春玉米增产没有积极作用，但适量硝化抑制剂浓度对土壤硝态氮淋溶具有抑制作用。

（4）秸秆深埋对土壤硝态氮淋溶下移可以起到有效阻控作用，降低深层土壤硝态氮累积量。施氮为200 kg/hm²时，秸秆深埋使得土层0—300cm硝态氮总累积量降低25.29%。施氮为250 kg/hm²时，秸秆深埋使得土层0—300cm硝态氮总累积量降低5.49%。同等施氮条件下，秸秆深埋提高春玉米籽粒产量，促进植株对氮肥的有效吸收，提高作物的氮素利用效率。

综上所述，在黄土高原沟壑旱作农业区，在当地气候和试验管理条件下，经数学模拟分析，施氮量达到227.38 kg/hm²时，春玉米可获得最高产量，采用秸秆深埋措施可促进春玉米提高产量。控制施氮量、采用秸秆深埋、施用缓控肥可控制土壤硝态氮的淋溶累积。施氮量1%的硝化抑制剂添加量对土壤硝态氮淋溶下移有阻控效果。

关键词：春玉米；缓控肥；硝化抑制剂；秸秆深埋；土壤硝态氮；淋溶阈值

Abstract

The development of fertilizer industry has promoted the increase of grain production and ensured the supply of food security. As human beings continue to apply a large amount of chemical fertilizers in the land, the negative effects of agricultural non-point source pollution are gradually highlighted, which brings great risks to human survival and health. In the future, agriculture will develop at the direction of green and environmental protection, which is of great significance to solve the problem of balance between agricultural production increase and environment. In the dry farming area of the Loess Plateau, the soil layer is deep and the rainfall is uneven, which provides conditions for agricultural non-point source pollution. Therefore, taking different nitrogen management measures in this area has important guiding significance for improving grain crop yield and maintaining ecological environment security.

The experiment was carried out at Changwu State Key Agro-Ecological Station. Pioneer 335, a spring maize , was planted with halfplastic film mulching,the experiment was designed by completely randomized grouping.The experiment inclueded four treatments and three replicates, they were: (1) Different nitrogen application rates, 0, 80, 100, 130, 160, 200 , 250 kg/hm² respectively; (2) On the basis of 200 kg/hm² nitrogen application, we set up different application ratios of slow-controlled fertilizer and ordinary urea, which took up the proportion 35%+65%, 50%+50%, 65%+35% respectively; (3) When applying 200 kg/hm² nitrogen, we set up different nitrification inhibitor concentration, The amount of nitrification inhibitor was 1%, 5%, 10% and 15% of total nitrogen application respectively. (4) Based on the application of 200 kg/hm² and 250 kg/hm² of nitrogen, Measures for straw deep buried was taken. In the experimental treatment zone of Slow-Controlled Fertilizer and nitrification inhibitor , we took root soil sample and measured soil nitrate nitrogen content during the growth period of spring maize. Soil and plant samples were taken during the harvest period of spring maize,and measured soil nitrate nitrogen content and grain yield, to confirm the effects of different nitrogen managements on soil nitrate nitrogen leaching and spring maize grain yield. The experiment was carried out from in 2017-2018 for two years. The main results are as follows:

(1) Appropriate amount of nitrogen application promoted the yield of spring maize and reduced soil nitrate nitrogen leaching and accumulation. The grain yield of spring maize increased at first and then decreased within the range of 0～250 kg/hm² of nitrogen application, and functional simulation analysis showed that the maximum yield could be achieved when nitrogen application was 227 kg/hm². Soil nitrate nitrogen content remained at a reasonable low level when nitrogen application within the range of 0～160 kg/hm², which would not cause a large amount of leaching and accumulation. When the amount of nitrogen applied exceeded 160kg/hm², the soil nitrate nitrogen leached into deep soil layer significantly, resulting in a sharp increase of soil nitrate nitrogen accumulation in the soil 0-300 layer. Therefore, the threshold of nitrogen application for soil nitrate nitrogen leaching and accumulation is 160 kg/hm². When the nitrogen application rate was 200 kg/hm², the total nitrogen uptake and nitrogen use efficiency of the plant reached the highest level. When the nitrogen application rate reached 250 kg/hm², grain yield of spring maize and nitrogen use efficiency were reduced.

(2) The application of slow-controlled fertilizer can effectively control the leaching of soil nitrate nitrogen, and reduce the accumulation of soil nitrate nitrogen. Among all treatments, when slow-controlled fertilizer and ordinary urea application proportion was each half, the soil nitrate nitrogen leached into deep soil layer was the least, reached the best control effect. The application of slow-controlled fertilizer reduced soil nitrate nitrogen accumulation in 0-300 cm soil layer by 37.39%. The application of slow-controlled fertilizer reduced the root layer soil nitrate nitrogen content at different growth stages of Spring Maize, and there was no significant difference among all slow-controlled fertilizer treatments. The application of slow-controlled fertilizer reduced the grain yield of spring maize, mainly because slow-controlled fertilizer efficiency released slowly in the early stage of spring maize growth, which is not synchronized with nitrogen uptake by spring maize roots, and reduced the total nitrogen uptake and nitrogen use efficiency of crops, at last reducing the spring maize yield.

(3) Appropriate amount of nitrification inhibitors can effectively prevent the leaching of soil nitrate nitrogen and reduce the accumulation of soil nitrate nitrogen. With the increase of nitrification inhibitors dosage, the risk of soil nitrate nitrogen leaching to deep soil increased, and the accumulation of soil nitrate nitrogen tended to increase. The nitrate nitrogen content in soil profile was the lowest when the amount of nitrification inhibitor was 1% of nitrogen application, and the nitrate nitrogen accumulation in 0-300 cm soil layer was the lowest（Compared with the control, it decreased by 55.68%）. The application of nitrification inhibitors significantly reduced the nitrate nitrogen content in root layer of Spring Maize at growth stages,but there was no significant difference between different amount of nitrification inhibitor treatments. Compared with the treatment without nitrification inhibitor, adding nitrification inhibitor had no positive effect on the yield of spring maize, but appropriate concentration of nitrification inhibitor had inhibitory effect on soil nitrate nitrogen leaching.

(4) Straw deep buried can effectively control the leaching of soil nitrate nitrogen, and reduce the accumulation of soil nitrate nitrogen. When nitrogen application was 200 kg/hm², the accumulation of soil nitrate nitrogen in 0-300 cm soil layer was reduced by 25.29% due to straw deep buried. When nitrogen application was 250kg/hm², the accumulation of soil nitrate nitrogen in 0-300 cm soil layer was reduced by 5.49% due to straw deep buried. When apply the same amount of nitrogen, the measures of straw burying can effectively improve the grain yield of spring maize, promote the absorption of nitrogen by plants, and improve the nitrogen use efficiency of crops.

In summary, under the conditions of local climate and experimental management, the maximum yield of spring maize can be obtained when the amount of nitrogen applied reaches 227.38 kg/hm2 through mathematical simulation analysis in the dry farming area of the Loess Plateau. The measure of straw deep buried can promote the yield of spring maize. the measures of controlling the amount of nitrogen applied, deep burying of straw and using slow-controlled fertilizer can control the leaching and accumulation of nitrate nitrogen in soil . Nitrification inhibitor of 1% nitrogen application could inhibit the leaching of soil nitrate nitrogen.

Key words: spring maize; slow-controlled fertilizer; nitrification inhibitor; straw deep buried; soil nitrate nitrogen; leaching threshold