旱涝交替下控制灌溉对稻田节水及氮磷减排的影响

该文研究控制灌排技术对稻田水氮磷动态变化及节水减排效应的影响。于2015年5—10月在河海大学江宁校区节水园,在有底侧坑内进行水稻栽培试验,于水稻分蘖期、拔节孕穗期、抽穗开花期和乳熟期4个生育阶段进行控水试验,以常规控制灌溉为对照,测定稻田淹排水铵态氮(NH_4~+-N)、硝态氮(NO_3~--N)和总磷浓度变化。结果表明:旱转涝处理淹水初期稻田水中铵态氮(NH_4~+-N)、硝态氮(NO_3~--N)和总磷浓度显著高于涝转旱处理,这个时期地表和地下排水应该引起注意。控制灌排条件下灌水量减少7.4%~18.5%,排水量减少23.0%~43.5%,NH_4~+-N负荷减少18.5%~54.5%,NO_3~--N负荷减少16.8%~57.7%,总磷负荷减少34.2%~58.3%;其中拔节孕穗期和抽穗开花期在保证节水减排的同时,也能实现较高的产量;因此,控制灌排技术具有较好的节水减排效果,对南方稻作区灌排实践具有指导意义。

Effect of controlled irrigation and drainage on saving water and reducing nitrogen and phosphorus loss in paddy field under alternate drought and flooding condition

Attempts to reduce the nutrient losses in drainage water have led to the promotion of controlled irrigation and drainage.Under the controlled irrigation and drainage condition,alternate drought and flooding condition (drought then flooding (HZL) and flooding then drought (LZH)) often occur.It is unclear about the change of nitrogen and phosphorus concentration in paddy water affected by controlled irrigation and drainage under the alternate stress.Therefore,this study based on farmland water depth as the control index aimed to investigate dynamic changes of nitrogen and phosphorus concentration in underground water and surface water of paddy field under the controlled irrigation and drainage in the HZL and LZH condition.Moreover,the effect of controlled irrigation and drainage on the discharge-reducing and water saving was studied.The experiments were conducted in specially designed experimental pits in Jiangning Water-saving Experiment Station at the Key Laboratory of Efficient Irrigation-Drainage and Agricultural Soil-Water Environment in Southern China,Ministry of Education,Nanjing (31°86′N,118°60′E) during the rice growing season of 2015 (May to October).Eight controlled irrigation and drainage treatments were designed for the experiment.For the HZL treatments,rice experienced the drought stress at first,and when the field water depth dropped to the lower limit (-500 mm) the irrigation water was added with an auto-irrigation system until the upper limit of water depth (200 mm at the tillering stage and 250 mm at the other stages)was reached.For the LZH treatments,rice experienced the flooding stress at first,and then irrigation water was immediately added to the upper limit of water depth (200 mm at tillering stage and 250 mm at the other stages);the field surface water was then drained and the field water depth dropped to the lower limit (-500 mm).The controlled irrigation was considered as the control with irrigation lower limit of-200 mm and the upper limit of 20 mm for the tillering stage and 50 mm for the other stages.Ammonia N (NH+4-N),nitrate N (NO-3-N),and total phosphorus (TP) in the water samples were analyzed.The results showed that when the HZL treatments had higher NH+4-N,NO-3-N and TP concentration during the earlier period of flooding,therefore,the surface and underground drainage should be noticed.Extending the flooding days could decrease nitrogen and phosphorus concentration in the controlled irrigation and drainage.The NH4+4-N was the major form of N in the surface drainage and percolation water.The TP concentration in the surface water followed a decreasing trend during the flooding.Compared to the controlled irrigation,under the controlled irrigation and drainage,the irrigation amount was reduced by 7.4％-18.5％,the drainage amount was reduced by 23.0％-43.5％,the NH+4-N load was reduced by 18.5％-54.5％,the NO-3-N load was reduced by 16.8％-57.7％ and the TP load was reduced by 34.2％-58.3％.Meanwhile,most of the controlled irrigation and drainage treatments could keep high rice grain yield.In sum,the controlled irrigation and drainage could achieve a positive effect on grain yield,water saving and N-P loss reduction at the jointing-booting stage and heading and flowering stage.Therefore,the controlled irrigation and drainage technology has a good effect on water saving and N and P loss reduction and provides a guide for the irrigation and drainage.