Effects of N and P additions on net nitrogen mineralization in temperate typical grasslands in Nei Mongol, China

The aim of this study was to investigate the effects of grazing on soil gross nitrification (GN) and denitrification (DN) rates and soil environmental factors on GN and DN in the desert grassland of northern China. Soil samples were collected from July to November in 2017 and March to June in 2018, with 5-5 soil samples taken from three enclosures (CK) vs. three heavy-grazing (G) randomized treatment blocks. We determined: (1) the soil moisture (SM), pH, bulk density (BD), total nitrogen (TN), soil organic carbon (SOC), and inorganic nitrogen (IN, NH4+-N, and NO3−-N) content, and (2) GN and DN. The relationship between the changes in GN, DN, and the soil environment was analyzed using stepwise multiple-regression analysis. Gross nitrification, DN, pH, BD, C/N, SM, IN, and NO3−-N varied significantly by month. Grazing induced significant increases in SM and NO3− only. GN in the CK treatment was related to NH4+-N and NO3−-N, while GN in the G treatment was related to NH4+-N and SM. DN in the CK treatment was related to NH4+-N, while DN in the G treatment was related to C/N. Additionally, GN and DN had obvious seasonal variations and reached a maximum in July. This highlights the different underlying mechanisms that affect soil GN and DN and the dynamics, particularly in the desert grassland system.

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Effect of Nitrogen Application and Microbial Fertilizer on Nitrogen Conversion Processes in Saline Farmland

Zhao,

et al. 2023

Water

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The nutrient utilization rate of salinized farmland soils is low, the nitrogen loss is high, and soil salinity inhibits the hydrolysis of urea and the release of nutrients. In this work, the effect of microbial fertilizer on the nitrogen transformation characteristics and nitrogen morphology of salinized soils was studied using indoor constant temperature incubation tests with different nitrogen application rates—without (A0) and with microbial fertilizer application (A1 (15 t/ha)) or nitrogen application (N) of 0 kg/ha (N0), 97.5 kg/ha (N1), or 195 kg/ha (N2). The results show the following: (i) When no microbial fertilizer was applied, an increased nitrogen application promoted nitrogen fertilizer’s ammonification and nitrification reactions. Furthermore, the maximum net nitrification rate with the high nitrogen fertilizer application decreased; the apparent ammonification rate and net ammonification rate A0N2 increased by 26.1% and 24.6%, respectively, compared with A0N1 on the first day of incubation; the maximum net nitrification rate of A0N1 was more than that of A0N2; and A0N1 > A0N2 on day 3, while A0N2 > A0N1 on days 3 to 15. At 3 d, the nitrogen conversion process of A0N1 was dominated by the nitrification reaction, while the ammonification reaction dominated in A0N2. (ii) Microbial fertilizers significantly increased the ammonification and nitrification rates under the low N fertilizer application. The intensity of ammonification and nitrification under the low N fertilizer application was greater than that under the high N fertilizer application. The apparent ammonification rate and net ammonification rate of A1N1 increased by 60.9% and 52.6% compared with A0N1 and 21.9% and 21.7% compared with A1N2 on the first day of incubation, and the peak net nitrification rates of A1N1 and A1N2 (28.19 mg/kg d and 11.02 mg/kg d, respectively) and net nitrification rates of A1N1 and A1N2 were 113.7% higher than those of A0N1. The net nitrification rates of A1N1 and A1N2 were 82.3% and 58.6% lower than the maximum net nitrification rates on the 15th day of incubation, respectively. (iii) In saline soils, low-nitrogen microbial fertilizers led to more ammonium nitrogen in the soil, and the high-nitrogen fertilizer application resulted in higher nitrate nitrogen in the soil, leading to nitrogen leaching. Therefore, when applying microbial fertilizer, choosing the most suitable period for reduced chasing is important for the efficient use of fertilizers, the alternative role of biofertilizers, and the study of environmental pollution.

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Effects of N and P additions on net nitrogen mineralization in temperate typical grasslands in Nei Mongol, China

Cited by 3 publications

References 15 publications

Increased soil microbial AOB amoA and narG abundances sustain long-term positive responses of nitrification and denitrification to N deposition

Increased soil microbial AOB amoA and narG abundances sustain long-term positive responses of nitrification and denitrification to N deposition

Grazing Horse Effects on Desert Grassland Soil Gross Nitrification and Denitrification Rates in Northern China

Effect of Nitrogen Application and Microbial Fertilizer on Nitrogen Conversion Processes in Saline Farmland

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