Location: Water Management and Systems ResearchTitle: Soil carbon pools in dryland agroecosystems as impacted by several years of drought
|SCHIPANSKI, MEGAN - Colorado State University|
|FONTE, STEVE - Colorado State University|
|LARSON, KEVIN - Colorado State University|
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/12/2018
Publication Date: 4/5/2018
Citation: Sherrod, L.A., McMaster, G.S., Delgado, J.A., Schipanski, M.E., Fonte, S.J., Montenieri, R.L., Larson, K. 2018. Soil carbon pools in dryland agroecosystems as impacted by several years of drought. Journal of Environmental Quality. doi:10.2134/jeq2017.09.0371.
Interpretive Summary: Long-term no-till and increased cropping intensity (CI) beyond the traditional wheat-fallow rotation are important practices that can increase crop production and soil organic carbon (SOC), and therefore soil health and quality, in the semi-arid Great Plains. Droughts can reduce carbon inputs into the soil and potentially reverse SOC gains accrued during wetter periods. Our objectives were i) determine soil C pools (0-20 cm) after 24 years in no-till as influenced by potential evapotranspiration (PET), landscape position (slope), and CI; and ii) compare the size of the C pools after the first 12 (wet) years versus the subsequent 12 years, notable for frequent droughts. Rotations were wheat-corn-fallow (WCF), continuous cropping (CC), and a native grass mixture (Grass) at three PET locations in Colorado that were planted in strips across the landscape. The three sites have similar annual precipitation (approx. 420 mm) but increase in PET from north to south. After 24 years, the levels of water soluble organic C (WSOC), soil microbial C biomass (SMBC) increased with CI in the 0-20 cm depth. The particulate organic matter C (POM-C) interacted with PET site, slope and CI. There was no CI impact on the passive mineral associated organic C (P-MAOC), but slope position and PET site where independently influenced with the strength of the significance being strongest within the landscape. Overall, at the end of the wet years verus the end of the dry years (24th year), SOC increased in Grass by 16.7%, with a rate of 425 kg C ha-1 yr-1 sequestration compared to 10.5 % and 1.4 % for the WCF and CC systems, respectively. This work showed that combining no-till with increased cropping intensity (i.e., less fallow period) will result in greater SOC, thereby improving soil health and quality, resulting in increased crop production and system resiliency.
Technical Abstract: No-till and increased cropping intensity (CI) can increase yield and soil organic carbon (SOC) in the US Great Plains compared with traditional wheat (Triticum aestivum L.) – fallow management. However, gains in SOC, and other C pools, may not be permanent. Increasing frequency of drought may reduce C inputs and potentially reverse gains accrued during wetter periods. This study examined the effect of drought on the persistence of SOC with two objectives: i) determine soil C pools (0-20 cm) after 24 years in no-till as influenced by potential evapotranspiration (PET), landscape position (slope), and CI; and ii) compare the size of the C pools after the first 12 (wet) years versus the subsequent 12 years, notable for frequent droughts. Rotations were wheat-corn (Zea mays L.)-fallow (WCF), continuous cropping (CC) and a Grass CRP mixture planted across slopes at three sites in Colorado with similar precipitation but increasing PET. After 24 years, water soluble organic C (WSOC) increased with CI from WCF- CC to Grass with 250, 340, and 440 kg C ha-1 respectively. Soil microbial C biomass (SMBC) also increased with CI; 1500, 1660 and 2135 kg C ha-1 for WCF, CC and Grass respectively. The particulate organic matter C (POM-C) pool had a 3-way interaction with PET, slope and CI. Overall between the 12th and 24th years, SOC increased in Grass by 16.9 %, with a rate of 425 kg C ha-1 yr-1 sequestration compared to 10.5 % and 1.4 % for the WCF and CC systems, respectively.