减氮配施有机物质对土壤氮素淋失的调控作用

采用室内土柱模拟试验方法,研究不同氮肥施用下1m土体中氮素的分布和移动特征,揭示土壤氮素动态变化规律。结果表明:FN(农民习惯施无机氮用量)、RN(根据土壤养分供应和作物需求确定的推荐无机氮用量)显著增加了土壤上层NH_4^+-N和NO_3^--N向下层淋失。RN+HA(与推荐无机氮纯养分相等的锌腐酸尿素)和RN40%+OMB(推荐无机氮肥减60%基础上配施自制有机调理物质)可延长上层土壤NH_4^+-N峰值出现时间,降低下层NH_4^+-N。淋溶结束后,等氮量下增施HA较RN降低60cm以下NH_4^+-N残留29.7%～54.2%;降低60—80cm NO_3^--N累积17.4%。RN40%+OMB处理无机氮肥用量最小,0—20cm的NH_4^+-N最高,40—100cm稳定在2.0mg/kg左右;0—20,20—40cm土层NO_3^--N较RN+HA增加12.3%和2.0%,显著降低40cm以下NO_3^--N残留。RN+HA和RN40%+OMB较RN的土壤总无机氮残留分别减少7.4%和20.2%,降低表观淋失率。因此,RN40%+OMB可较好地抑制氮素下移,降低氮素淋失风险,为减少氮素淋失、明确合理氮肥施用方式提供科学依据。

Regulation of Reduced Nitrogen and Organic Matter Application on Nitrogen Leaching

The distribution and movement features of nitrogen in 1 m soil layer under different nitrogen fertilizer application were studied through artificial soil column simulation experiment in laboratory to reveal the dynamic changes of nitrogen in farmland soil. Results indicated that FN (the amount of inorganic nitrogen used by farmers) and RN (inorganic nitrogen dosage recommended by soil nutrient supply and crop demand) significantly increased the leaching of NH₄⁺-N and NO₃^--N from upper soil layer to lower soil layer. The treatments of RN+HA (zinc humic acid urea equivalent to the recommended inorganic nitrogen with RN) and RN40%+OMB (60% inorganic nitrogen fertilizer of RN with homemade organic substances) could prolong the peak time of NH₄⁺-N in the upper soil layer and reduce the NH₄⁺-N in the lower soil layer. At the end of leaching experiment, comparing with RN, the application of humic acid (HA) decreased the NH₄⁺-N residue by 29.7%~54.2% in the soil layer below 60 cm under the same amount of nitrogen, and reduced the accumulation of NO₃^--N by 17.4% in 60-80 cm soil layer. In RN 40%+OMB treatment, the dosage of inorganic nitrogen fertilizer was the minimum, and NH₄⁺-N was the highest in 0-20 cm soil layer and it was stable at 2.0 mg/kg in 40-100 cm soil layer. Comparing with RN+HA, NO₃^--N in 0-20 cm and 20-40 cm soil layer in this treatment increased by 12.3% and 2.0%, respectively, and the NO₃^--N residue in the soil layer lower than 40 cm was significantly reduced. Contrasted with RN, the total inorganic nitrogen residue of RN+HA and RN40%+OMB decreased by 7.4% and 20.2%, respectively, and the apparent leaching rate was decreased. Therefore, RN40%+OMB could inhibite the downward movement of nitrogen and reduce the risk of nitrogen leaching, and these results provide a scientific basis for reducing the nitrogen leaching.