Effect Of Controlled Release Nitrogen Fertilizer On Soil Microbiological Characteristics And Nitrogen Fertility

A field experiment was conducted based on monitoring experiment station for reddish paddy soil eco-environment in Wangcheng County, Hunan Province. The main aims were to study the status of microbial biomass and populations, physiological groups of microorganisms, and bacterial community diversity in soil affected by different N fertilization and application rates or combine with swine manure after double rice-cropping region. There were five treatments:1)control(no nitrogen applied, CK);2)Urea(120kgN/hm~2 applied in early rice and 150 kgN/hm~2applied in late hybrid rice); 3)CRNF(120kgN/hm~2 applied in early rice and 150 kgN/hm~2applied in late hybrid rice,the nitrogen fertilizer was CRNF); 4)70%CRNF(84kgN/hm~2 applied in early rice and 105 kgN/hm~2 applied in late hybrid rice,the nitrogen fertilizer was CRNF);5)50%CRNF+M(84kgN/hm~2 applied in early rice and 105 kgN/hm~2 applied in late hybrid rice,there were two nitrogen fertilizers, 80%CRNFand 20% swine manure applied).The changes of soil nitrogen fertility in paddy soil were also discussed. The main resultsas follow:Results showed that the amounts of bacteria, fungi and actinomycetes were higher in soil with CRNF treatment than those in CK treatment. The amounts of bacteria and actinomycetes in soil with applying CRNF treatment were increased, but slightly lower than that of fungi in urea treatment. Combined application of 50%CRNF with organic manure (swine manure) increased bacteria, fungi and actinomycetes in soil as compared with CRNF applied alone. The amounts of aerobic and anaerobic azotobacteria were lower in fertilizer treatments than in CK treatment. The amounts of aerohic azotobacteria, ammonifiers and anti-nitrifiers were lower in soil with CRNF applied than those in soils with urea applied. The amounts of aerohic azotobacteria, ammonifiers, nitrifiers and anti-nitrifiers were higher in combined application of 50%CRNF with organic manure than in CRNF alone.Application of the controlled release N fertilizer significantly increased new band numbers and diversity index of bacterial community in soil, especially the 50%CRNF+M treatment.We observed that soil microbial biomass (SMB) concentrations were significantly affected by different N fertilization. The changes of microbial biomass C were less remarkable as those of microbial biomass N during rice growth stages. The contents of SMBC and SMBN were the highest at 10 day period after fertilize application, then decreased gradually as progress of rice growing stages, but increased again during late rice growth stages. The results of this experiment showed that soil microbial biomass N was significantly higher in 50%CRNF+M treatment than in other treatments. The contents of SMBN and SMBC in plough layer were different. The contents of SMBC was higher in soils of CRNF and Urea with high nitrogen fertilizer applied than in soils of 70%CRNF and 50%CRNF+M with less nitrogen fertilizer applied. But the contents of SMBN was lower in rhizosphere and 5-10 cm soils of CRNF and Urea with high nitrogen fertilizer applied than in soils of 70%CRNF and 50%CRNF+M with less nitrogen fertilizer applied. The contents of SMBN and SMBC of CRNF treatment were higher than Urea in rhizosphere and 5-10 cm soils, but lower in 0-5 cm soils.Results showed that the total hydrolysable nitrogen (THN) was the main part of soil total nitrogen and its average percentage to total nitrogen (TN) was 86.2%. THN in soil with N fertilizer application was higher compared with no N application at 10 ds period after fertilizer application. The contents of THN was showed the trend of increasing-decreasing- increasing during rice stages as well as soil microbial biomass.The contents of THN with CRNF fertilizer application were significantly higher compared with urea fertilizer application at late rice growth stages.TN and THN and Nonhydrolysable nitrogen (NHN) in plough layer soil with N fertilizer application were higher compared with no N application.The percentage of ammonia acid nitrogen (AAN) and hydrolysable undefined nitrogen (HUN) were the greatest, and the percentage of ammonia sugar nitrogen (ASN) was the smallest. Ammonium nitrogen(AN) concentrations in 0-5cm soil with N application were higher than no N application. ASN of the treatments with N application in rhizosphere soils were higher than that of the treatments with no N application, while lower in 0-10 cm soil. The contents of AAN with N treated were lower compared with control treated in 0-5 cm soil, but higher in 5-10 cm soil. AAN contents in rhizosphere soils with CRNF and 50%CRNF+M were increased significantly (p<0.01) compared with other treatments. The effects of nitrogen fertilizer on HUN in plough layer soil were no significantly.Mineral nitrogen and available nitrogen with N fertilizer application were higher in early growth stage than in late growth stage of rice. The contents of mineral nitrogen with CRNF fertilizer treated(CRNF,70%CRNF and 50%CRNF+M) soils were much higher compared with Urea and contol treated soils during the middle growth stages of rice, their contents in soil were decreasing gradually as the growing stages progressed, and no difference in late growth stages of rice.The contents of available nitrogen in treatmets with N application were higher than control treatment after N applied, and its contets of CRNF and 50%CRNF+M were significantly higher than those in other treatments. Then the contents of available nitrogen decreased gradually as progress of rice growing stages, and were lowest at the tillering stage.The contents of fixed ammonium in early rice soil with N application were higher compared with late rice, however, fixed ammonium of late hybrid rice in late growth stage were the same level after fertilizer applied in early rice, and the contets in CRNF fertilizer treated (CRNF and 70%CRNF and 50%CRNF+M) were slightly higher than those in urea and control treated.The N uptake and yield of the rice were higher in CRNF,70%CRN and 50%CRNF+M treatments than those in Urea treatment. The average N recovery of rice with CRNF application (64.4%) was much higher than that of Urea (43.6%) in our study...