Cover Crops Enhance Soil Properties in Arid Agroecosystem despite Limited Irrigation

Cover crops (CCs) can enhance the sustainability and resiliency of agroecosystems by providing multiple ecosystem benefits, including soil quality improvement. However, in areas with limited precipitation such as the southwestern USA, cover cropping is challenging. With limited water, it may be difficult to raise cover crops for realizing ecosystem benefits. Research was conducted at two sites in New Mexico over two years to determine if CC under limited irrigation could produce enough biomass to improve soil quality. Treatments included a fallow (control) and monocultures of barley (<i>Hordeum vulgare</i>), Austrian winter peas (<i>Pisum sativum</i> subsp. arvense), mustard (<i>Brassica rapa</i>, var. Caliente 199), and a three-way mixture of these species, grown under three different irrigation regimes. The results indicate that the improvement in soil quality measurements by CCs grown under one supplemental irrigation were comparable to those grown under multiple irrigations. All CC treatments improved the soil dry aggregate size distribution from 2018 to 2020. At the end of the study, the MWD of dry aggregates was higher (3.26 mm) in all CC treatments than in the fallows (2.43 mm) at one site, but at the second site, mustard and mix were comparable to the fallows. Wet aggregate stability increased by 19% in the mix between 2018 and 2020 at one site. Pea plots needed about 23 kg ha⁻¹ less N fertilizer for sweet corn production compared to the fallow treatment at one site. This suggests that CCs can be successfully grown under limited water availability in irrigated arid systems of New Mexico while still improving the soil quality.