不同减量氮肥配施紫云英对田面水氮磷流失及水稻生长的影响

为指导水稻田合理施肥,防治稻田面源污染,试验开展了不同氮肥减施比例对紫云英—水稻轮作体系下稻田田面水氮磷流失的影响研究。2020年在浙江建德开展田间小区试验,设置冬闲(CK)和冬种紫云英(CT)2个处理,并在冬种紫云英基础上设置4个减氮比例,分别为0(CT0),10%(CT1),20%(CT2),30%(CT3),共5个处理,每个处理重复3次。在水稻移栽施肥后开始稻田田面水样品采集(包括施肥2周内的连续采样以及2周后相隔7,14,28天的间隔采样),测定田面水氮磷浓度;于水稻成熟后采集土壤和植物样品,测定土壤理化性状以及水稻生长性状和产量。各处理田面水总氮、可溶性氮、铵态氮以及总磷、可溶性磷均在施肥后第1天达到峰值,总氮在基肥后4天内降幅明显,为最大值的4.2%~9.1%,可溶性磷在施基肥5天内降至最大值的4.7%~13.7%。采样期内,CK处理田面水总氮、可溶性氮、总磷和可溶性磷的平均浓度分别为48.87,36.82,0.82,0.64 mg/L,CT0、CT1、CT2、CT3的总氮平均浓度分别为CK的93.9%,78.1%,79.7%,69.7%;可溶性氮平均浓度分别为CK的95.1%,84.1%,85.7%,73.2%;总磷平均浓度分别为CK的90.9%,76.9%,96.2%,81.3%;可溶性磷平均浓度分别为CK的79.4%,73.8%,87.3%,68.7%。与CK相比,CT2、CT3显著提高土壤有效磷含量,增加幅度分别为61.7%和37.0%。比较冬闲处理,翻压紫云英使水稻株高增高0.7%~3.5%,有效穗数增加7.0%~15.2%,水稻增产0.4%~4.9%。与冬闲处理相比,冬种紫云英配合不同比例氮肥减施均能降低稻田田面水氮磷流失风险,其中以30%氮肥减量效果最好;紫云英配合减氮施肥措施能够提升土壤有效磷、全氮含量和水稻产量,其中均以紫云英配合20%减氮施肥效果最好。综合稻田田面水氮磷流失风险、土壤肥力以及水稻产量,紫云英配合20%减氮施肥是较为适合该地区的种植方式。

Effects of Different Nitrogen Reduction Fertilizer Combined with Milk Vetch (Astragalus sinicus L.) on the Loss of Nitrogen and Phosphorus in Field Water and Rice Growth

In order to guide the rational fertilization of paddy fields and prevent non-point source pollution of paddy fields, we studied the effects of different nitrogen fertilizer reduction ratios on the nitrogen and phosphorus loss in the surface water of paddy fields under the milk vetch (Astragalus sinicus L.) -rice rotation system. In 2020, field plot experiment was conducted on Jiande, Zhejiang. Two treatments of winter idle and winter milk vetch were set up, and four nitrogen reduction ratios of 0 (CT0), 10% (CT1), 20% (CT2) and 30% (CT3) on the basis of winter planted milk vetch. There were 5 treatments in total, each treatment was repeated three times. After paddy transplanting and fertilization, surface water samples of paddy field were collected (including continuous sampling within two weeks of fertilization and sampling at intervals of 7, 14, and 28 days after two weeks), and the concentration of nitrogen and phosphorus in the field water was measured. After the rice matured, soil and plant samples were collected and soil physicochemical properties, rice growth properties and yield were determined. The total nitrogen, soluble nitrogen, ammonium nitrogen, total phosphorus and soluble phosphorus in the field surface water of each treatment reached their peaks on the first day after fertilization. The total nitrogen decreased significantly within four days after basal fertilizer application, which was 4.2%~9.1% of the maximum value, and the soluble phosphorus decreased to 4.7%~13.7% of the maximum value within five days of basal fertilizer application. During the sampling period, the average concentration of total nitrogen, soluble nitrogen, total phosphorus and soluble phosphorus in the CK was 48.87, 36.82, 0.82 and 0.64 mg/L, respectively. The average concentration of total nitrogen in CT0, CT1, CT2 and CT3 was 93.9%, 78.1%, 79.7% and 69.7% of CK, respectively. The average concentration of soluble nitrogen was 95.1%, 84.1%, 85.7% and 73.2% of CK, respectively. The average concentration of total phosphorus was 90.9%, 76.9%, 96.2 and 81.3% of CK, respectively. The average concentration of soluble phosphorus was 79.4%, 73.8%, 87.3% and 68.7% of CK, respectively. Compared with CK, CT2 and CT3 significantly increased soil available phosphorus content by 61.7% and 37.0%, respectively. Compared with winter fallow treatment, turning over and pressing milk vetch increased rice plant height by 0.7%~3.5%, effective panicle number by 7.0%~15.2% and rice yield by 0.4%~4.9%. Compared with the treatment of winter fallow, the combination of winter planting of milk vetch and different proportions of nitrogen fertilizer reduction could reduce the risk of nitrogen and phosphorus loss in paddy field surface water, of which 30% nitrogen fertilizer reduction was the best. Milk vetch combined with nitrogen reduction fertilization measures improved content of soil available phosphorus and total nitrogen and rice yield. In these treatments, milk vetch combined with 20% nitrogen reduction fertilization had the best effect. Considering the rice yield, soil fertility and risk of loss of nitrogen and phosphorus in paddy field surface water, the combination of milk vetch and 20% nitrogen fertilizer reduction was a more suitable planting method for this area.