Net Global Warming Potential and Greenhouse Gas Intensity Influenced by Irrigation, Tillage, Crop Rotation, and Nitrogen Fertilization

Abstract

Little information exists about how global warming potential (GWP) is affected by management practices in agroecosystems. We evaluated the effects of irrigation, tillage, crop rotation, and N fertilization on net GWP and greenhouse gas intensity (GHGI or GWP per unit crop yield) calculated by soil respiration (GWP and GHGI) and organic C (SOC) (GWP and GHGI) methods after accounting for CO emissions from all sources (irrigation, farm operations, N fertilization, and greenhouse gas [GHG] fluxes) and sinks (crop residue and SOC) in a Lihen sandy loam from 2008 to 2011 in western North Dakota. Treatments were two irrigation practices (irrigated vs. nonirrigated) and five cropping systems (conventional-till malt barley [ L.] with N fertilizer [CTBN], conventional-till malt barley with no N fertilizer [CTBO], no-till malt barley-pea [ L.] with N fertilizer [NTB-P], no-till malt barley with N fertilizer, and no-till malt barley with no N fertilizer [NTBO]). While CO equivalents were greater with irrigation, tillage, and N fertilization than without, NO and CH fluxes were 2 to 218 kg CO eq. ha greater in nonirrigated NTBN and irrigated CTBN than in other treatments. Previous year's crop residue and C sequestration rate were 202 to 9316 kg CO eq. ha greater in irrigated NTB-P than in other treatments. Compared with other treatments, GWP and GWP were 160 to 9052 kg CO eq. ha lower in irrigated and nonirrigated NTB-P. Similarly, GHGI and GHGI were lower in nonirrigated NTB-P than in other treatments. Regardless of irrigation practices, NTB-P may lower net GHG emissions more than other treatments in the northern Great Plains.

Global warming potential and greenhouse gas intensity in rice agriculture driven by high yields and nitrogen use efficiency

“…However, the release of CO 2 during the manufacturing and application of N fertilizer to crops and from fuel used in machines for farm operations can counteract these mitigation efforts (West and Marland, 2002). Therefore, when determining the GWP of agroecosystems, there is a need to account for all sources of GHG emissions, including the emissions associated with agrochemical input (Ei) and farm operation (Eo) and sinks, e.g., soil organic carbon (SOC) sequestration (Sainju et al, 2014).…”

Agricultural Management Impact on Greenhouse Gas Emissions

“…They observed this because (1) no nitrogen fertilizer was applied to legumes compared with nonlegumes which required large amount of nitrogen fertilizers to sustain yields, as nitrogen fertilizer stimulates N 2 O emissions and (2) legumes supplied greater amount of nitrogen to succeeding crops due to higher nitrogen concentration when above-and belowground residues were returned to the soil and reduced nitrogen fertilization rate compared with nonlegumes. Sainju et al [9,10] also found that legume-nonlegume rotation increased soil carbon sequestration because of increased turnover rate of plant carbon to soil carbon compared to continuous nonlegume.In a meta-analysis of 11 experiments on the effect of crop rotation containing small and large grain crops on net GWP and GHGI, Sainju [56] reported that crop rotation increased net GWP by 46% and net GHGI by 41% compared with monocropping. This was especially true for large grain crops, such as corn and soybean where net GWP and GHGI were 215 and 325%, respectively, greater under corn-soybean than continuous corn.…”

“…In contrast, greater N 2 O emissions following soybean increased net GWP and GHGI in corn-soybean rotation [3,7,48,49]. Under small grain crops, however, several researchers [9,10,60,61] have found that including legumes, such as pea and lentil, in rotation with nonlegumes, such as wheat and barley, reduced net GWP and GHGI compared with continuous nonlegumes. They observed this because (1) no nitrogen fertilizer was applied to legumes compared with nonlegumes which required large amount of nitrogen fertilizers to sustain yields, as nitrogen fertilizer stimulates N 2 O emissions and (2) legumes supplied greater amount of nitrogen to succeeding crops due to higher nitrogen concentration when above-and belowground residues were returned to the soil and reduced nitrogen fertilization rate compared with nonlegumes.…”

“…In the calculations of net GWP and GHGI, emissions of N 2 O and CH 4 are converted into their CO 2 equivalents of global warming potentials which are 265 and 28, respectively, for a time horizon of 100 year [2]. The balance between soil carbon sequestration rate, N 2 O and CH 4 emissions (or CH 4 uptake), and crop yield typically controls net GWP and GHGI [3,4,7].Some of the improved management practices used for reducing net GWP and GHGI from croplands are no-till, increased cropping intensity, diversified crop rotation, cover cropping, and reduced N fertilization rates [3,4,[7][8][9][10]. Soil organic carbon can usually be increased by adopting no-tillage practice which decreases microbial activity and CO 2 emissions as a result of reduced soil disturbance and residue incorporation compared with conventional tillage practice [3,11].…”

“…Increased carbon sequestration with increased cropping intensity in the semiarid regions with limited precipitation is well known [18,62]. Several researchers [7,9,50] have found that fallowing or crop-fallow rotation increased GHG emissions and therefore net GWP and GHGI compared with continuous cropping due to increased soil temperature and water content that enhanced microbial activity and absence of crops to utilize mineralized nitrogen during fallow. Using partial accounting of CO 2 sources and sinks, Liebig et al [63], however, did not found significant difference in net GWP between alternate-year fallow and continuous cropping in North Dakota.…”