Potential loss of phosphorus from a rice field in Taihu Lake basin.
Nonpoint-source pollution by phosphorus (P) poses a threat to waters in the Taihu Lake basin in China. The potential transfer of P in rice (Oryza sativa L.) fields through surface drainage and subsurface flow was investigated under simulated conventional irrigation-drainage management. Surface drainage events were conducted to avoid overflow across the plots after heavy rainfall and for rice harvest, at which time P losses were also investigated. This study was conducted in 2001 in a long-term rice field experiment. The experimental plots were treated with 0, 26, or 52 kg P ha(-1) as superphosphate or 26 kg P ha(-1) with equal parts of P supplied as superphosphate and pig manure. Phosphorus concentrations and loads in field floodwater on plots receiving P rapidly declined in a nonlinear manner before the first drainage, three weeks after fertilizer application. The combined application of fertilizer and manure P resulted in higher P transfer potential in field floodwater than with fertilizer P alone one week after P application. Phosphorus concentrations in interflow water sampled by Teflon suction cups inserted at a depth of 150 to 200 mm gradually increased within two weeks after P application, then declined. The concentration of P in interflow water was related to soil P buildup from long-term P application, as well as recently applied P. The 26 kg P ha(-1) treatment (the conventional P rate in this region) resulted in a loss of 0.74 kg total phosphorus (TP) ha(-1) and a drainage-weighted average concentration of 0.25 mg TP L(-1) from the three surface drainage events. Results indicate that avoiding overflow drainage after P input and extending the time between P application and drainage may reduce P losses from rice paddies.
Zhang
ZhiJian
Z
Environmental Technology Center, College of Environmental and Resource Sciences, Zhejiang University, Kuanxian 268, Hangzhou, Zhejiang 310029, P.R. China.
Zhu
YinMei
Y
Guo
PeiYong
P
Liu
GuangSheng
G
D000383:Agriculture; D004784:Environmental Monitoring; D005068:Eutrophication; D005308:Fertilizers; D007194:India; D012275:Oryza; D010758:Phosphorus / Q000032:analysis*; D011891:Rain; D014872:Water Movements; D014873:Water Pollutants / Q000032:analysis*
D005308:Fertilizers; D014873:Water Pollutants; D010758:Phosphorus