| China Northeast is the base for grain production and spring maize is the main crop. In 2008 its planting area and total production accounts for 28% and 31% of China national total, respectively. However, a series problem associated with the intensive maize production occur such as increase of chemical fertilizer (CF) input and decrease of organic fertilizer (OM) amendments, decline of soil organic matter and soil fertility, etc. Nitrogen (N) fertilizer has been usually applied one time during growing season and little organic manure or slow release fertilizer was applied. Phosphorus (P) fertilizer has been high-analysis compound fertilizer which resulted in P accumulation in soil. Thus, it important to investigate the optimum patterns of N and P application in spring maize in northeast region for improving nutrient use efficiency and sustainability of land use. According to the investigation and analysis of farmer practice and issues in fertilizer application, this study was to investigate the effects of various patterns of N application (i.e. 100% chemical N as basal, Chemical N with 1/3 as basal and 2/3 as topdressing, 30% organic fertilizer N substitution for chemical N, regular N combined slow-release N and, regular N combined organic fertilizer N plus slow-release N) and patterns of P application (100% chemical fertilizer as basal, 30% organic fertilizer P substitution for chemical N) on soil N or P supply, maize plant growth, nutrient uptake, yield, nutrient use efficiency and soil nutrient balance and try to find appropriate pattern for efficient use of N and P fertilizer. The main results are as follows:1. When N, P and K was applied at the same amount, N application pattern with 30% organic fertilizer N substitution for chemical N significantly reduced mineral N in 0-20cm and 20-40cm soil layer at the seedling and jointing stage of spring maize, but similar to or higher than that of the pattern with basal application of 100% chemical fertilizer N.2. Results from experiment in 2008 indicated that when N was applied at conventional N rate (190 kg N/hm2) there was no significant different between N application patterns. When N was applied at recommended rate (152 kg N/hm2) N application patterns with 30% organic fertilizer N substitution significant reduced dry matter accumulation of maize from seedling to tasselling stage, but similar at filling and harvest stage compared with 100% chemical fertilizer N application either as basal or basal:topdressing of 1:3. Results from experiment in 2009 indicated that when N was applied at conventional rate (190 kg N/hm2) N application patterns with 30% organic fertilizer N substitution significant reduced dry matter accumulation of maize from belling to filling stage, but similar at harvest compared with 100% chemical fertilizer N application. When N was at the recommended rate (150 kg N/hm2) the patterns with 30% organic fertilizer N substitution reduced dry matter accumulation of maize from jointing to belling stage, and then significantly increased at filling and maturity stage compared with 100% chemical fertilizer N application.3. Results from experiment in 2008 showed no significantly different effect on N accumulation between N application patterns. Results from experiment in 2009 indicated that when N was applied at conventional rate (190 kg N/hm2) N application pattern with 30% organic fertilizer N substitution significant reduced N accumulation by maize at jointing, tasselling and filling stage, but similar at harvest compared with 100% chemical fertilizer N application. When N was applied at recommended rate (150 kg N/hm2) N application patterns with 30% organic fertilizer N substitution accumulated similar to or significantly more N during maize growth except at belling stage compared with 100% chemical fertilizer N application.4. Nitrogen application significantly increased maize yield by 6.0%-16.8% and 10.9%-24.2% in 2008 and 2009, respectively. N application pattern with 30% organic fertilizer N substitution for chemical fertilizer N produced similar or higher maize yield and benefit than other N application patterns at the same N rate. Patterns with both organic fertilizer N substitution and slow release N resulted in lower benefit. Organic fertilizer N substitution for chemical fertilizer N could not increase N recovery efficiency compared with other N application patterns at the same N rate.5. Organic P substitution for 30% of chemical P could increase soil Olsen-P at seedling and jointing stages and so improve P availability. The effect of P application on dry matter accumulation and maximum accumulation rate had no significant difference between the pattern with organic P substitution and pattern with chemical P alone when P was applied at either conventional rate (75 kg P2O5/ hm2) or recommended rate (60 kg P2O5/ hm2).6. Phosphorus content and accumulation in maize plants did not significantly influence, but the maximum P accumulation rate was decreased and delayed by P application with organic P substitution for 30% chemical P compared with 100% chemical P alone at the same P rate. Organic P substitution for 30% chemical P improved P redistribution within maize plant and P contribution to the grains.7. Application of P increased maize yield by 1.7%-5.0% and 0.6%-6.4% in 2008 and 2009, respectively. Compared with chemical P alone, organic P substitution for 30% chemical P did not significantly affected maize yield and P recovery effieicncy, but increased agronomic efficiency of P and economic benefit.
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