秸秆还田和施肥对砂姜黑土理化性质及小麦-玉米产量的影响

通过安徽省蒙城县砂姜黑土上连续4a的冬小麦-夏玉米连作长期定位试验,研究了秸秆还田配合施用不同量氮肥对土壤理化性质及作物产量的影响。结果表明,秸秆还田可降低土壤容重2.5%—9.2%,提高含水量8.2%—28.5%和表层土壤贮水量4.1%—19.9%;增加土壤总孔隙度1.1%—8.9%、毛管孔隙度18.9%—41.0%,非毛管孔隙度降低6.4%—38.8%,土壤毛管孔隙度占土壤总孔隙度的比例增加。秸秆还田所有处理耕层的土壤硝态氮含量高于秸秆移除处理,施氮540、630、720 kg N hm-2a-1时,秸秆还田处理的硝态氮含量显著高于秸秆移除,而铵态氮含量无明显变化规律。无论秸秆还田还是秸秆移除,耕层土壤的硝态氮含量随氮肥用量的增加呈指数趋势增加,硝态氮含量与施氮量的相关性秸秆移除处理高于秸秆还田处理;秸秆还田处理的铵态氮含量随施氮量增加成指数趋势增加,而秸秆移除处理呈指数趋势减小,相关性均不显著。秸秆还田条件下,小麦和玉米获得高产的年氮肥用量分别为630、696 kg N hm-2a-1,秸秆移除为579、627 kg N hm-2a-1。经作用力分析,秸秆还田是影响土壤物理性质的最重要因素,作物产量受秸秆还田和施氮量的影响,但氮肥水平大于秸秆还田。

Effects of combined straw and N application on the physicochemical properties of lime concretion black soil and crop yields

The effects of a combination of returned straw and different N fertilizer application rates on the physical and chemical properties of lime concretion black soil and crop yields were systematically studied, based on data from a four year experiment using a winter wheat-summer maize rotation system in Mengcheng City, Anhui Province, China. The results showed that the bulk density of surface soil under areas where straw was either incorporated or removed were 1.14-1.20 g/cm³ and 1.24-1.31 g/cm³, respectively. Straw incorporation decreased soil density by 2.5%-9.2%, while soil water content and water storage increased over the four years by 8.2%-28.5% and 4.1%-19.9%, respectively, after the return of the straw. The total soil porosity and capillary soil porosity in the areas of returned straw treatments ranged from 3.0%-57.1% and 33.9%-41.0%, respectively, whilst the same parameters ranged from 50.7%-54.6% and 27.3%-29.5%, respectively, under the areas where straw was removed. In contrast, non-capillary porosity decreased by 6.4%-38.8%, showing a significant difference between areas where straw was incorporated or removed. The nitrate nitrogen content of top soil under the returned straw treatment areas was significantly increased by 9.80%-86.71% greater than that of the areas where straw was removed, especially with N application rates of 540, 630, and 720 kg N hm^-2 a^-1. Nitrogen accumulation in surface soil for N application rates of 360, 450, 540, 630 and 720 kg N hm^-2 a^-1 were 1.42, 1.53, 2.22, 2.51 and 2.12 times that of areas where no fertilizer was added, respectively, for the returned straw areas and 1.24, 1.38, 1.53, 1.59, 1.72 times the no added fertilizer accumulation for the area where straw was removed. For both straw incorporated areas or not, there were exponential relationships between the nitrate nitrogen content and N application amount, although the correlation coefficient was higher under the straw incorporation treatments than for those where straw was removed. Compared to nitrate, the ammonia nitrogen content showed no obvious differences between areas of straw incorporation and removal. Ammonia accumulation under different N application rates was affected by straw addition. Under straw return treatments, it increased exponentially with the increase of N application rates, and decreased exponentially under areas where straw was removed, but there was no significant correlation. The effects of straw incorporation and N application rates on maize and wheat yields were different. For maize, the yield gradually increased from 360 kg N hm^-2 a^-1 to 720 kg N hm^-2 a^-1of N application levels under both straw added areas and straw removed areas. However, the wheat yield gradually increased from 360 kg N hm^-2 a^-1 to 450 kg N hm^-2 a^-1 and from 360 kg N hm^-2 a^-1 to 630 kg N hm^-2 a^-1, and decreased when N exceeded 450 kg N hm^-2 a^-1and 630 kg N hm^-2 a^-1 under areas of straw removal and straw incorporation. The high yields of maize and winter-wheat with straw incorporation treatments would be obtained under the N application rates of 696, 630 kg N hm^-2 a^-1, respectively. N application rates of 579, 627 kg N hm^-2 a^-1 in straw removal areas would obtain high yields, but they were lower than that from areas of returned straw treatments. The force analysis showed that returning straw was the most important influencing factor of soil physical properties, and both straw incorporation and N application rates can compact crop yields, but the force of N level to yield is stronger than that for returning straw.