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Effects of straw-returning on annual overland runoff NPK loss in farmland

A field experiment was conducted to investigate the effects of straw return on annual total nitrogen(N),total phosphorus(P),kalium(K) loss quantity with overland runoff in wheat-rice double cropping system in 2009-2010.The wheat cultivar of Yangmai 16 and rice cultivar of Yun 2645 was field-grown.Five treatments such as conventional measurement(A),wheat straw return(B),wheat straw return with reducing fertilizer(C),fertilizer application(D),rotational tillage system(E) were conducted.The results showed that:(1) Total overland runoff of farmland was 6.4 × 106 kg.hm-2in this wheat-rice season,with twenty times.(2) Straw return significantly reduced annual overland runoff NPK loss.In different treatments condition,both the order of total N and K loss were E A D B C,and the order of total P loss was D E A B C.Compared with conventional measurement(A),straw return decreased overland runoff N,P,K loss averaging 7.7%,8.0%,6.8%.(3) The proportion of rice season overland runoff NPK loss was 61.5%,44.0%,73.3% to the total NPK loss over the wheat-rice season.(4) Straw return reduced annual overland runoff NPK loss rate.(5) Soil available nutrient content was increased under straw return at rice maturity stage.(6) Straw return increased annual crop yield in wheat-rice double cropping system a little.