麦季牛场肥水灌溉对冬小麦–夏玉米轮作土壤氮素平衡的影响

规模化畜禽养殖废弃物已成为当前重要的污染来源,为有效控制畜禽养殖污水面源污染,将处理后的养殖肥水作为水、氮资源进行农田灌溉,在华北冬小麦–夏玉米轮作灌溉区,连续3 a进行牛场肥水灌溉田间定位试验,研究冬小麦季牛场肥水灌溉对作物产量、氮表观利用率、土壤无机氮残留及轮作体系氮平衡的影响。结果表明,肥水灌溉能显著提高作物产量,肥水灌溉处理(冬小麦生育期内肥水灌溉带入氮为160、240和320 kg/hm2)冬小麦和夏玉米3 a产量平均增幅分别为36.78%和40.82%。随着牛场肥水灌溉年限的推移作物增产效果逐渐明显,冬小麦–夏玉米轮作体系作物累计氮利用率逐年升高,6季作物收获后氮累计利用率达47.87%~67.63%,肥水氮后效明显。肥水灌溉增加了100 cm土体内无机氮残留,NO3--N残留量显著高于NH4+-N。对冬小麦–夏玉米轮作体系氮平衡分析表明,随牛场肥水灌溉带入氮量增加,作物氮累计吸收增加,在冬小麦生育期内肥水氮带入量为160 kg/hm2夏玉米生育期内不施氮处理(T1),氮表观利用率显著高于其他肥水灌溉处理(T2和T3),100 cm土体无机氮残留率和氮表观损失率均显著低于T3处理,与T2处理差异不显著。该试验条件下,综合产量、氮累计利用率及土壤无机氮残留考虑,冬小麦–夏玉米轮作体系肥水灌溉适宜氮带入量为160~240 kg/hm2。适量牛场肥水灌溉冬小麦–夏玉米能够增加作物产量,增加作物对肥水氮的利用率,减少氮在土壤中的积累。

Effects of dairy effluents irrigation on N balance in soil under winter wheat-summer maize rotation system

Abstract: With the development of intensive cultivation of livestock in China, a large number of effluents are produced. However, the treatment and utilization rate of livestock effluents are low, which causes nitrogen and phosphorus losses and the problems of water resource shortage and serious overexploitation of the groundwater for agricultural irrigation in the North China Plain. In order to control the non-point pollution, the experiment was conducted in the North China Plain for 3 years to test the effects of continuous dairy effluent irrigation on crop yield, nitrogen (N) use efficiency, residual inorganic N and N balance in winter wheat - summer maize rotation system. The study included five treatments with three replications: No fertilizer and freshwater irrigation in wheat growing season (CK), 2 times dairy effluent irrigation in wheat growing season (T1), 3 times dairy effluent irrigation in wheat growing season (T2), 4 times dairy effluent irrigation in wheat growing season (T3), customized fertilization, inorganic compound fertilizer of 375 kg/hm2 after planting, and 600 kg/hm2 urea application at wheat jointing stage, freshwater irrigation in wheat growing season (CF). The irrigation quota was 830 m3/hm2, and the irrigation quantity was controlled by water Ultrasonic flowmeters. The results showed that dairy effluent irrigation significantly increased the winter wheat and summer maize yield by 36.78% and 40.82% respectively. With the increasing of N application amount, the yield of winter wheat increased at first and then decreased. When the N application amount was 240 kg/hm2, the yield of wheat was the maximum. However, the yield of maize increased with the increasing of N application amount, and when the N application amount was 320 kg/hm2, the yield of maize was the maximum. The yield of wheat increased by 1.56%-12.47% and maize increased by 1.84%-7.27% in the three-year successive harvests, though the N application rates were reduced by 3.61%-51.81% for wheat and by 68.94%-74.89% for maize. The nitrogen accumulation amounts in plant and grain under the treatments with dairy effluent irrigation were significantly higher than those under the treatment CK. There was no significant deference among the treatments T1, T2, T3 and CF in 2011 and 2012, the nitrogen accumulations in winter wheat for the treatments T2, T3 and CF were significantly higher than that for treatment T1. The crop yield increased gradually with the increasing of dairy effluent irrigation span. The crop N use efficiency increased year by year, and in the third year the crop N use efficiency reached 47.87%-67.63%, which was the carryover effect of dairy effluent irrigation. After harvesting winter wheat, with the increasing of nitrogen amount of dairy effluent, the soil nitrate accumulation in 0-100 cm soil layer was increased. The soil nitrate accumulation in 100 cm soil layer of 4 times irrigation was significantly higher than that of 2-3 times irrigation. The dairy effluent irrigation significantly enhanced the residual inorganic N in 0-100 cm soil layer, and the residual nitrate N was apparently more than the residual ammonium N. The results of N balance showed that the N uptake by crop increased with the increasing of N application amount. After the irrigation using dairy effluent in wintering and elongation period of wheat, N use efficiency of crop was significantly greater than that cultivated by normal fertilization and irrigation. Residual inorganic N in 0-100 cm soil layer and apparent N loss were significantly less than that in other dairy effluent irrigation treatments, and decreased by 39.73% and 55.67% respectively than that in the normal fertilization irrigation treatment. Considering crop yield, accumulative N use efficiency and soil inorganic N balance, it is concluded that 2-3 times dairy effluent application is appropriate in winter wheat - summer maize rotation system.