Soil and soil organic carbon effects on simulated Southern High Plains dryland cotton production

Authors: Mauget, Steven; HIMANSHU, SUSHIL - Texas A&M Agrilife; Goebel, Tim; ALE, SRINIVASALU - Texas A&M Agrilife; Lascano, Robert; Gitz, Dennis

Submitted to: Soil and Tillage Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/20/2021
Publication Date: 6/16/2021
Publication URL: https://handle.nal.usda.gov/10113/7367269
Citation: Mauget, S.A., Himanshu, S., Goebel, T.S., Ale, S., Lascano, R.J., Gitz, D.C. 2021. Soil and soil organic carbon effects on simulated Southern High Plains dryland cotton production. Soil and Tillage Research. 212. https://doi.org/10.1016/j.still.2021.105040.
DOI: https://doi.org/10.1016/j.still.2021.105040

Interpretive Summary: Advisors from national and regional agricultural services have made impressive claims about the effect of increasing soil organic carbon (SOC) on a soil’s capacity to hold water, and, potentially, to increase agricultural yields. To check those claims, ARS scientists from Lubbock used specialized mathematical functions to estimate the effect of increasing SOC on the water retention of two representative soils in the U.S. Southern High Plains. In addition, they used crop simulation models to estimate the related effects of higher SOC on un-irrigated cotton yields. Although higher SOC increased both soil’s ability to hold water, a greater effect was found in the sandier of the two soils. These effect’s magnitudes were consistent with those found in past studies, but considerably below those claimed by the national and regional agricultural advisors. As surface SOC levels in both the soils were increased the sandier soil’s median simulated cotton lint yields were basically unchanged, while yields simulated with the less sandy soil decreased. Thus this work showed that increased SOC had a minor effect of soil water retention in the two soils, and a neutral or negative yield effect. As a result, the conservation management practices intended to increase SOC may not have the effect of increasing yields and profits.

Technical Abstract: The effect of increasing soil organic content (SOC) on the soil water retention and cotton yield productivity of two U.S. Southern High Plains (SHP) soils was estimated using pedotransfer functions and the CROPGRO-Cotton crop simulation model. In the two regionally representative soils, increasing plow layer (0-30 cm) SOC leads to increased wilting point (WP), field capacity (FC), and plant available water capacity (PAW = FC-WP). The increase in a clay loam’s available water capacity is modest, with a 1% increase in SOC producing an additional 0.16 cm of PAW in the soil profile’s uppermost 30 cm. The fine sandy loam’s plow layer effect is almost twice that, with a 1% SOC increase producing a 0.32 cm PAW increase. These effect’s magnitudes were consistent with a recent meta-analysis of SOC on soil water retention, but considerably below those cited by national and regional extension services. As surface SOC levels in both soils were increased above baseline levels the fine sandy loam’s median simulated cotton lint yields were essentially unchanged, while clay loam yields decreased. The clay loam yield effect is attributed to increased soil evaporation rates. Conservation agriculture (CA) practices such as increased residue retention may compensate for these weak soil water retention effects, but cotton’s limited residue production would require winter cover crops or alternate crop rotations. As the success of terminated winter wheat – dryland cotton rotations is unclear in past SHP field studies, a CA sorghum-cotton rotation with periodic tillage is proposed as an SHP dryland production system.