Effects of alternate wetting and drying irrigation at key growth periods on rice yield and nitrogen and phosphorus loss characteristics in Erhai Lake Basin
Author:
Affiliation:
(1.International College of Rivers and Ecological Security，Yunnan University，Kunming Yunnan 650500;2.Yuntianhua Co.，LTD.， Kunming Yunnan 650500;3.College of Resources and Environment，China Agricultural University，Beijing 100080)
This study aimed to investigate the impact of various water management strategies on rice yield and nitrogen and phosphorus loss during key growth periods. Taking Yunjing 37 as the research object，a field experiment was carried out in Wanqiao Town and Lecun Village，Dali City，Yunnan Province. Different irrigation techniques，including conventional irrigation(CI)，mild alternate wetting and drying(AWD)，heavy alternate wetting and drying I(WSDⅠ)，and heavy alternate wetting and drying II(WSDⅡ)，were implemented to assess their effects on rice yield fluctuations as well as nitrogen and phosphorus loss patterns. Compared to CI treatment，the effective tillering number of AWD，WSDⅠ and WSDⅡ treatments increased by 31.8%，14.8% and 1.1%. AWD treatment resulted in a 6.9% increase in yield，reaching 10.8 t·hm-2. There was no significant difference in yield between CI treatment and WSDⅠ and WSDⅡ treatments. Compared with CI，the three dry and wet alternating treatments significantly reduced runoff and infiltration losses of total nitrogen(TN)，total phosphorus(TP)，ammonium nitrogen(NH4+-N)，and nitrate nitrogen(NO3--N)，with the lowest pollution to Erhai Lake observed under WSDⅠ treatment. Irrigation amount was significantly reduced by 49.9%-54.0% with AWD，WSDⅠ，and WSDⅡ treatments，leading to a reduction in water seepage by 47.7%-52.6%；Irrigation productivity was increased by 59.9%-137.0%.However，compared with CI treatment，the drainage increased by 177.3%-256.1%，And losses of TN，TP，NH4+-N and NO3--N in AWD treatment were decreased by 31.5%，64.1%，70.0% and 47.8%，respectively，and those in WSDⅠ treatment decreased by 39.9%，73.4%，74.0% and 50.6%，respectively，while WSDⅡ treatment reduced TP and NH4+-N losses by 75.0% and 74.0%，respectively. However，TN and NO3--N losses were increased by 3.9% and 11.1%，respectively. In conclusion，for lake basins with abundant groundwater，normal rehydration after alternating heavy dry and wet conditions during the jointing booting stage could maintain rice yield and reduce nitrogen and phosphorus pollution. This study provided insights for the development of rice farming areas in similar lake basins.