Efifciencies, Budget, Simulation And Application Of Nitrogen In Long-term Fertilization Wheat-maize Cropping System In China

Using the monitoring data from "National Soil Fertility and Fertilizers Effects Net", thebalance of nitrogen and carbon in various soils and climates in wheat-maize rotation system wasstudied. The present study mainly focused on the budget and long-term efficiencies of nitrogenand temporal and spatial variation of total aerial nitrogen deposition, which were used for nitrogenfertilization recommendation and validation; also on biomass, yield, nitrogen uptake of wheat andmaize and the soil carbon dynamic in response to agricultural management practices and climateswere simulated using the Agricultural Production Systems Simulation (APSIM) in order toincrease efficiency and management of nitrogen in agri-ecosystem. The mainly results are:1. Under zero-nitrogen application (only phosphorus and potassium applied as PK), averagebiomass of wheat and maize for15years was2454and5844kg/ha, respectively, andcorresponding grain yield was1387and3555kg/ha. Under balance fertilization (NPK, FS, FMand HF), average biomass of wheat and maize for15years was10302and11503kg/ha,respectively, and corresponding grain yield was4230and5931kg/ha. The results showed that soilsuffer nitrogen deficiation and nitrogen fertilization is a way of food security in China.2During15years, contribution of nitrogen to grain yield of wheat and maize were between61%and325%and24and199%, respectively. Corresponding average values are199%and126%.The highest grain yield increment of wheat and maize attributed to nitrogen were at Zhengzhousite (4459kg/ha) and at Yangling (3965kg/ha), respectively. It is suggested that wheat could begiven priority over maize when nitrogen fertilization as a result from contributions of nitrogen tograin yield of wheat be more than that of maize.3The nitrogen physiological efficiencies of wheat varied from12.3and95.7kg grain per kgnitrogen with36.9kg grain per kg nitrogen on average. For maize they varied from5.5and87.8kg grain per kg nitrogen with48.1kg grain per kg nitrogen on average. Generally,1kilogramnitrogen absorbed in biomass could produce35.6and39.5kilogram grain yield for wheat andmaize, respectively.4. Apparent accumulated nitrogen recovery efficiencies (NREac) varied4%and90%in alltreatment in all sites. The variation of NREacfrom normal nitrogen fertilization (NP, NPK, FS andFM) was between44%and90%with71%on average, in which from one rotation system per yearthe variation was narrative with81%on average that could be used in nitrogen fertilizationrecommendation, which was validated by data derived from3414field experiments.5. Combination of data published about3414experiments and the phenomena of nitrateaccumulated in the soil profit in wheat-maize cropping system, some equations used by nitrogenfertilization recommendation were deducted in order to use nitrate in soil profits as well asdecreasing pollution. Furthermore, the nitrogen fertilization recommendation of system based onyield goal was amended contributed to easy performance in field. 6. Temporal and spatial variations of total aerial nitrogen deposition (TND) were studiedusing biomass nitrogen in zero-nitrogen treatment (PK). The result showed that TND amounts ofannual average were76,80and94kg nitrogen for Changping, Zhengzhou and Yangling,respectively with increasing in Yangling. And there were no correlations between TND amountsand precipitations and also suggested that dry deposition were main pattern in this system.Amounts of TND from NPK treatment accounted for17~21%of total nitrogen input that wasequal to loss rate by way of volatilization and leaching of nitrogen in wheat-maize croppingsystem.7Agricultural Production System Simulator (APSIM) well simulated the biomass and yieldin wheat-maize cropping system besides in Urumchi with0.65of R2. Simulating under automaticirrigation in100year, the highest biomass were30,29,20.8,27.5and15.4t/ha in Zhengzhou,Changping, Yangling and Urumchi, respectively. Corresponding grain yield were14.7,8.6,12.4and6.9t/ha with350,150,200and250kg/ha of nitrogen. Simulating under rainfed in100year, thehighest biomass were18.7,6.6,5.1and2.8t/ha in Zhengzhou, Changping, Yangling and Urumchi,respectively. Corresponding grain yields were8.5,2.6,2.1and0.2t/ha. Simulating soil carbondynamic under nitrogen rate when highest grain yield in100years, soil carbon could bemaintained without straw return under both automatic irrigation and rainfed in Zhengzhou, butincreasing in Changping and decreasing in Yangling. Soil carbon was significant deceasing inUrumchi. Furthermore, the trend could be accelerated by irrigation and stop by100%straw return.