Effects Of Combined Application Of Inorganic And Organic Fertilizers On Growth And Nitrogen Uptake Of Wheat And Rice

Based on15N isotope tracer and a pot experiment, effect of combined application of inorganic fertilizer with straw, pig slurry, straw compost and pig slurry compost on wheat growth and nitrogen uptake was studied in paddy soil and gray alluvial soil from2010-2011. A field experiment was carried out in Yan Cheng to studied the effect of combined application of inorganic fertilizer with straw and goat manure in2011. The main results were as follows:Compared with the inorganic N fertilization treatment, combined application of organic and inorganic fertilizers increased wheat yields by4.46%-24.82%and2.90%～22.78%in paddy soil and gray alluvial soil, respectively. Wheat yields under combined application of straw compost and pig slurry compost were higher than combined application of straw and pig slurry by4.94%～10.49%and6.38%-10.85%, respectively. Rice yields under application of inorganic fertilizer were significantly higher than combined application of straw, but had no significant differences with combined application of goat manure. The highest dry matter accumulation of rice was observed at heading stage with23.55-33.25t/ha, and it was dropped to21.49～24.44t/ha at harvesting stage. The dry matter weight in combined application of20%15N-labelled straw was significantly lower than other treatment at maturity.Combining application of straw compost and pig slurry compost stimulated N uptake and improved N accumulation of wheat. Application of straw compost and pig slurry compost treatments gave the highest15N recovery rate, while the lowest15N recovery rate was found in the treatment of inorganic N fertilization alone. The total amount of nitrogen accumulation under combined application of organic and inorganic fertilizer was higher than the treatment of inorganic fertilizer alone on both gray alluvial soil and paddy soil.Nitrogen accumulated in rice plant increased firstly and arrived maximum amount at heading stage, then decreased a little at harvesting stage. The dry matter weight of rice had a similar variation trends with rice N accumulation. Combined application of goat manure gave the highest N accumulation, while the lowest N accumulation was obtained from the treatment of combined application of straw. Combined application of20%goat manure gave the highest N accumulation.Soil microbial biomass nitrogen under combined application of straw and pig slurry was always higher than that under combined application of straw compost and pig slurry compost during wheat growth season. In tillering stage, soil mineral nitrogen under the inorganic N fertilization treatment was higher than the other treatment, and it was lower in later growing stage. During the whole growing stage, soil mineral nitrogen under combined application of straw compost and pig slurry compost treatments were higher than that under combined application of straw and slurry treatments. The changing trend of soil mineral nitrogen content in rice season was same with that of wheat season. Soil microbial nitrogen content decreased rapidly at first, then down slowly during rice growing period. At harvesting, the content of soil microbial nitrogen was a little higher than that at heading. Comparing with combined application of goat manure, the content of soil microbial nitrogen under combined application of straw was higher, while soil mineral nitrogen content was lower.In summary, combined application of composts and inorganic fertilizer were more conducive to reduction of nitrogen loss, improving the activity of soil microbial biomass, and increasing crop yield and plant N uptake.