[Effects of combined application of pig manure with urea on grain yield and nitrogen utilization efficiency in...

To examine the effects of pig manure application on dry matter production, nitrogen accumulation and distribution, grain yield and nitrogen use efficiency of rice and wheat, the field trial was conducted with wheat 863 and rice 498. Fertilization treatments consisted of seven rates of organic manure supply: control (CK, no chemical nitrogen fertilizer, no pig manure), conventional fertilizing (T₁, no pig manure), 2500 kg·hm^-2 pig manure with 75% conventional fertilizing (T₂), 5000 kg·hm^-2 pig manure with 50% conventional fertilizing (T₃), 10000 kg·hm^-2 pig manure (T₄), 15000 kg·hm^-2 pig manure (T₅) and 20000 kg·hm^-2 pig manure (T₆). Combined application of pig manure with chemical fertilizer promoted dry matter accumulation of rice and wheat throughout the growing season. At the maturity stage of rice and wheat, the highest aboveground dry matter accumulation presented under highest pig manure input (T₆). The dry matter accumulation and nitrogen distribution were enriched in stem or leaf. The dry matter accumulation and nitrogen distribution rate in grain at T₆ was significantly lower than T₂ treatment. The high-est nitrogen fertilizer partial productivity, fertilizer agronomic efficiency and grain yield of rice pre-sented at T₃ treatment, which increased by 11.4%, 55.4%, 11.4% than that of conventional chemical fertilizer treatment, respectively. These vaules for wheat were at T₂, which was 14.0%, 29.1%, 14.0% higher than that of conventional fertilizer treatment, respectively. The combined application of pig manure with appropriate rates of chemical fertilizer (T₂ and T₃) could promote dry matter accumulation, the migration of nitrogen to grains, the increase of yield and the nitrogen use efficiency. Too much pig manure input (15000-20000 kg·hm^-2) could lead to excessive supply of nitrogen for crops. In this case, the transportation of dry matter to economic organs would be blocked and the nitrogen enriched to stem. The late-maturing phenomenon occurred, resulting in significant decrease of grain yield.