The effect of nitrogen fertilization and no‐till duration on soil nitrogen supply power and post–spring thaw greenhouse‐gas emissions

Abstract

With a world population now > 7 billion, it is imperative to conserve the arable land base, which is increasingly being leveraged by global demands for producing food, feed, fiber, fuel, and facilities (i.e., infra-structure needs). The objective of this study was to determine the effect of varying fertilizer-N rates on soil N availability, mineralization, and CO 2 and N 2 O emissions of soils collected at adjacent locations with contrasting management histories: native prairie, short-term (10 y), and long-term (32 y) no-till continuous-cropping systems receiving five fertilizer-N rates (0, 30, 60, 90, and 120 kg N ha -1 ) for the previous 9 y on the same plots. Intact soil cores were collected from each site after snowmelt, maintained at field capacity, and incubated at 20°C for 6 weeks. Weekly assessments of soil nutrient availability along with CO 2 and N 2 O emissions were completed. There was no difference in cumulative soil N supply between the unfertilized longterm no-till and native prairie soils, while annual fertilizer-N additions of 120 kg N ha -1 were required to restore the N-supplying power of the short-term no-till soil to that of the undisturbed native prairie soil. The estimated cumulative CO 2 -C and N 2 O-N emissions among soils ranged from 231.8-474.7 g m -2 to 183.9-862.5 mg m -2 , respectively. Highest CO 2 fluxes from the native prairie soil are consistent with its high organic matter content, elevated microbial activity, and contributions from root respiration. Repeated applications of ≥ 60 kg N ha -1 resulted in greater residual inorganic-N levels in the long-term no-till soil, which supported larger N 2 O fluxes compared to the unfertilized control. The native prairie soil N 2 O emissions were equal to those from both short-and long-term no-till soils receiving repeated fertilizer-N applications at typical agronomic rates (e.g., 90 kg N ha -1 ). Eighty-eight percent of the native soil N 2 O flux was emitted during the first 2 weeks and is probably characteristic of rapid denitrification rates during the dormant vegetative period after snowmelt within temperate native grasslands. There was a strong correlation (R 2 0.64; p < 0.03) between measured soil Fe-supply rate and N 2 O flux, presumably due to anoxic microsites within soil aggregates resulting from increased microbial activity. The use of modern no-till continuous diversified cropping systems, along with application of fertilizer N, enhances the soil N-supplying power over the long-term through the build-up of mineralizable N and appears to be an effective management strategy for improving degraded soils, thus enhancing the productive capacity of agricultural ecosystems. However, accounting for N 2 O emissions concomitant with repeated fertilizer-N applications is imperative for properly assessing the net global warming potential of any land-management system.

Changes in Ammonia-Oxidizing Archaea and Bacterial Communities and Soil Nitrogen Dynamics in Response to Long-Term Nitrogen Fertilization

“…The extensive input of ammonium fertilizers (such as urea) has been reported to selectively stimulate the AOA or AOB abundance in the agricultural field [ 19 ], and in turn, microorganism-mediated nitrification ultimately leads to a reduction of nitrogen use efficiency (NUE) [ 22 , 23 ]. Moreover, excessive N fertilizer application not only increases the risk of nitrate (NO 3 -N) leaching and runoff loss [ 24 , 25 ], and loss of N 2 O or N 2 due to denitrification and ammonia oxidation [ 26 ], but also leads to severe pollution [ 27 ] and greenhouse effect [ 28 , 29 ], which have been major environmental problems in some regions of Europe, the United States, and China [ 30 , 31 , 32 ]. Therefore, most countries in the EU have taken measures to limit the rate of N application [ 33 , 34 ].…”

Effect of Long-Term Nitrogen Addition on Wheat Yield, Nitrogen Use Efficiency, and Residual Soil Nitrate in a Semiarid Area of the Loess Plateau of China

“…With a high rate of N fertilizer application, some fertilizer N may remain in the soil at the end of the growing season, which can be absorbed by the following crops [17] or lead to the negative environmental impacts such as nitrate leaching, greenhouse gas emission, and eutrophication of water bodies [18][19][20][21]. Nitrate leaching and water pollution are major environmental problems in Europe, the USA, China, and elsewhere in rainfed areas due to the excessive application of N fertilizer [22][23][24]. Therefore, most countries in the European Union restrict the rate of N application to 170 kg N ha −1 per year [25,26].…”

Soil heterotrophic respiration assessment using minimally disturbed soil microcosm cores

“…For standard heterotrophic respiration assessment, a soil moisture content of 50% water holding capacity (WHC) is advised. This moisture level is recommended to ensure staying below the critical threshold for denitrification during the incubations [ [12] , [13] , [14] ]. Refer to the section entitled: “determination of WHC” below to determine and adjust this parameter.…”