No abstract

No abstract

No abstract

Core Ideas The soil organic C dynamics and net ecosystem C balance of five dryland cropping systems were compared. Conservation systems stored up to 15% more soil organic C than conventional system. Net ecosystem C balance was positive with cover cropping. Cover crops and conservation tillage are crucial for soil C storage in drylands. Biomass C inputs often limit agroecosystem C dynamics, nutrient cycling, and soil organic carbon (SOC) storage in semiarid drylands. This study evaluated SOC and net ecosystem carbon balance (NECB) of five cropping systems in the drylands of the Southern Great Plains. Cropping systems evaluated included corn (Zea mays)–sorghum [Sorghum bicolor (L.) Moench] rotation with conventional tillage without cover cropping (CTNC), strip tillage with and without cover cropping (STCC and STNC, respectively), and no tillage with and without cover cropping (NTCC and NTNC, respectively). After 4 yr of experimental tillage, we measured CO2 emissions, soil and soil surface air temperatures, soil moisture content, potentially mineralizable carbon (PMC), total SOC, total nitrogen (TN), and net primary productivity (NPP). Conservation systems (any treatments including no‐till, strip till, or cover crops) had 5 to 6°C lower soil temperature and 2.8 to 4.9°C lower soil surface air temperature and stored 2.3 to 3.9% more soil moisture content than CTNC. Conservation systems also stored 15.2% more SOC than CTNC. Cropping systems that integrated cover crops in the rotation (STCC and NTCC) had greater NPP and positive NECB. Regardless of tillage management, cover cropping had a greater NECB, including SOC (NECBSOC) than CTNC. Reducing tillage and diversifying cropping systems through cover cropping can benefit semiarid dryland agroecosystems by increasing SOC storage and maintaining positive NECB.

Cover crops improve soil health and environmental quality by enhancing soil organic carbon (SOC) sequestration and nutrient cycling in agroecosystems. This study evaluated the effect of cover crops on soil CO2–C emissions, temperature, and water content during cover crop growth from April to October, 2017 and 2018. Treatments included fallow, pea (Pisum sativum L.), oat (Avena sativa L.), canola (Brassica napus L.), pea–oat (POmix), pea–canola (PCmix), pea–oat–canola (POCmix), and POC–hairy vetch (Vicia villosa L.)–forage radish (Raphanus sativus L.)–barley (Hordeum vulgare L.) (six species mixture; SSmix). The CO2–C emissions were monitored weekly from April to October each year using a portable infrared‐gas analyzer. Seasonal changes in CO2–C emissions varied with cover crops and peaked as soil temperature and water content following precipitation events. Average CO2–C emissions across sampling dates was 46–70% greater under pea than under fallow, canola, and POmix in 2017, but not different among cover crops in 2018. Although the emissions were higher than fallow, canola and POmix plots had lower CO2–C emissions than other cover crops. Pea as sole cover crop or in mixtures (PCmix, POCmix, SSmix) increased CO2–C emissions and microbial activity whereas canola and POmix mixture reduced the emissions during the period with higher precipitation.