How Tillage and Fertilization Influence Soil N2O Emissions after Forestland Conversion to Cropland

Abstract

Soil nitrous oxide (N2O) emissions are influenced by land use adjustment and management practices. To meet the increasing socioeconomic development and sustainable demands for food supply, forestland conversion to cropland occurs around the world. However, the effects of forestland conversion to cropland as well as of tillage and fertilization practices on soil N2O emissions are still not well understood, especially in subtropical regions. Therefore, field experiments were carried out to continuously monitor soil N2O emissions after the conversion of forestland to cropland in a subtropical region in Southwest China. One forestland site and four cropland sites were selected: forestland (CK), short-term croplands (tillage with and without fertilization, NC-TF and NC-T), and long-term croplands (tillage with and without fertilization, LC-TF and LC-T). The annual cumulative N2O flux was 0.21 kg N ha−1 yr−1 in forestland. After forestland conversion to cropland, the annual cumulative N2O flux significantly increased by 76‒491%. In the short-term and long-term croplands, tillage with fertilization induced cumulative soil N2O emissions that were 94% and 235% higher than those from tillage without fertilization. Fertilization contributed 63% and 84% to increased N2O emissions in the short-term and long-term croplands, respectively. A stepwise regression analysis showed that soil N2O emissions from croplands were mainly influenced by soil NO3− and NH4+ availability and WFPS (water-filled pore space). Fertilization led to higher soil NH4+ and NO3− concentrations, which thus resulted in larger N2O fluxes. Thus, to reduce soil N2O emissions and promote the sustainable development of the eco-environment, we recommend limiting the conversion of forestland to cropland, and meanwhile intensifying the shift from grain to green or applying advanced agricultural management practices as much as possible.

Nitrous oxide emissions and maize yield as influenced by nitrogen fertilization and tillage operations in upland soil

“…Agricultural practices can be related to N 2 O emission based on crop yield, referred to as yield-scaled N 2 O emission (YSNE). There are many studies observed the effect of tillage operations and N fertilization on N 2 O emission in the arable land [17][18][19][20][21]. Therefore, the objective of this study was to determine the effects of different tillage operations and N fertilizations on N 2 O emission and crop yield from upland soil.…”

Soil gross nitrogen transformations in forestland and cropland of Regosols

“…Numerous studies have indicated that long-term N fertilizer applications could stimulate autotrophic nitrification rates 18,30,47,48 . Applying mineral N fertilizer could induce the rapid increases in NH 4 + concentrations for several weeks in cropland soils, thus providing sufficient available substrates for nitrification [49][50][51] . However, in this study, soil samples were collected once in April when several months had passed since the last fertilizer application.…”