宁夏引黄灌区猪粪还田对稻作土壤硝态氮淋失的影响

以宁夏引黄灌区稻田为例,探索猪粪还田条件下稻田土壤硝态氮淋失规律。试验设置3个处理:常规施肥300 kg纯N kg/hm2(CK)、常规施肥条件下施用4500kg/hm2(T1)和9000 kg/hm2(T2)猪粪。利用树脂芯法吸附稻田30cm、60cm和90cm土层的硝态氮流失量。结果表明:在常规施肥的基础上增施猪粪,可以减少稻田生育期内60cm与90cm处土壤硝态氮淋失量,与CK相比,T1、T2在两个土层处淋失量的减少比例分别为4.93%、13.92%与7.48%、13.77%。同一土层不同处理之间差异显著性比较看(P0.05),30cm处T1、T2与CK相比没有达到显著性差异;60cm处,T1与CK未达到显著差异,T2与CK达到显著差异;90cm处,T1、T2与CK相比达到显著差异;60cm和90cm土层处的T2与T1之间均达到显著差异。T1和T2在30cm处的淋失量高于CK,但增加不明显,处理之间以及处理与对照相比差异不显著。稻田生育期内不同土层硝态氮淋失量在13.61—17.77 kg/hm2(纯N)。硝态氮淋失集中在插秧至分蘖期(5月中旬—6月下旬),该阶段的硝态氮淋失量占生育期内总淋失量的61.62%—72.84%;后期淋失量明显减少。处理T1、T2的水稻产量增产率分别为15.86%与12.85%。由此可见,在引黄灌区稻田,一定数量的猪粪还田,不仅能够减少土壤硝态氮向深层淋失,防控地下水污染,还有利于水稻增产。

Effect of nitrate nitrogen leaching of paddy field based on swing manure application in the Yellow River irrigation district of Ningxia

The Yellow River irrigation district of Ningxia is an important agricultural area in North China, where the nitrate leaching and water pollution have been an increasing problem in recent year. Water in a number of drainage ditches is of Inferior quality, in which the main pollutants are nitrate and ammonium nitrogen. The concentration of ammonium is usually 20-30mg/L and can be much higher up to 70 mg/L in extreme cases, so that downstream water quality is severely affected. The proportion of total nitrogen and ammonia nitrogen from field was up to 61%-66% and 76%-81%, respectively. The concentration of nitrate nitrogen in about half of shallow groundwater was more than 10 mg/L. Content of soil organic matter, ranging from 9.2 to 14.5g/kg with the mean of 10.2 g/kg, was low; consequently it facilitates the loss of soil nutrient nitrate nitrogen. In this study, we investigated the effect of swine manure application in management of nitrate nitrogen leaching and improvement of soil organic matter in this area. The characters of nitrate nitrogen leaching in paddy fields in the Yellow River irrigation district of Ningxia were explored in the condition of swine manure application. The field experiment was conducted with 3 treatments: tradition fertilization without swine manure (CK), tradition fertilization with swine manure of 4500kg/hm²(T₁)and tradition fertilization with swine manure of 9000 kg/hm²(T₂). Nitrate nitrogen leaching rates were measured for 30, 60, 90 cm depth soil layer with a resin core absorption method. The results are shown as follows: (1) The treatments with swine manure application reduced the nitrate nitrogen leaching loss at 60 and 90 cm depth soil layers in the paddy field during rice growth period. The decreases were 4.93% (60 cm) and 13.92% (90 cm) for T1 vs. CK and 7.48% (60 cm) and 13.77% (90 cm) for T2 vs. CK. (2) In comparisons of the statistical significance of nitrogen leaching loss at the same soil layer between different treatments (P < 0.05), the variations among T₁, T₂ and CK were not significant at 30 cm depth. In the soil samples from 60 cm depth, T₁ and CK were not significantly different, while T₂ was significantly different from CK. Compared to CK, both T₁ and T₂ caused a significant reduction in nitrogen loss at 90 cm depth. Meanwhile, the difference between T₁ and T₂ were significant at 60 and 90 cm depth. Although the nitrate nitrogen leaching loss of T₁ and T₂ were higher than that of CK at 30 cm depth, the difference did not reach statistical significance among CK and T₁ and T₂. (3) The nitrate nitrogen leaching loss was 13.61-17.77 kg/hm² (pure nitrogen) in different soil layers during rice growth period. The major loss accounting for 61.62%-72.84% of the whole growth period occurred during the time from rice transplantation to tillering, corresponding to the season from middle May to end of June, and the loss was obviously alleviated at the late stage of rice growth. (4) The rice yield in T₁ and T₂ was increased by 15.86% and 12.85%, respectively. Taken together, our study suggests that swine manure application is effective to prevent nitrate nitrogen leaching loss in the Yellow River irrigation district of Ningxia and beneficial to rice production as well.