Submitted to: Journal of Agricultural Chemistry and Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2016
Publication Date: 11/3/2016
Citation: Goebel, T.S., Lascano, R.J., Acosta Martinez, V. 2016. Evaluation of stable isotopes of water to determine rainwater infilitration in soils under conservation reserve program. Journal of Agricultural Chemistry and Environment. 5:179-190.

Interpretive Summary: In 1985, the USDA introduced the Conservation Reserve Program (CRP) geared to identify agricultural land that was highly susceptible to erosion and that could be managed by increasing its vegetative cover to reduce soil losses. Enrollment into the CRP program was done via contracts between landowners and the USDA and these arrangements varied in length between 10 and 15 years. Since the inception of the CRP several modifications have been introduced, mainly on the number of acres enrolled in the program. The Farm Bill of 2014 dictated that the number of acres in the CRP needed to decline and this reduction varied by State and by soil type. For example, Texas leads the nation with more than 2 million acres enrolled in CRP and the decline in the Texas High Plains (THP) was 23% less acres. The long-term benefits of CRP are improvements of soil physical and chemical properties mainly due to an increase in soil organic matter and carbon content, leading to a better soil structure and thus improving infiltration of rainfall and reduction of water runoff. How will this reduction in CRP acres affect the water balance of both CRP and dryland cropping systems in the THP? Of importance is to determine the infiltration depth of rainfall into these systems and thus our objective was to evaluate the feasibility of using stable isotopes of water to measure this parameter. For this purpose, we selected a site in Lynn and in Terry County, both in the Amarillo soil series, to determine the infiltration depth of rainfall on fields under CRP and dryland crop production. Our results showed that stable isotopes of water can be used to measured the depth of rainfall due to infiltration to soils under CRP and dryland management.

Technical Abstract: The Conservation Reserve Program (CRP) is a USDA program introduced in 1985 to reduce soil erosion by increasing vegetative cover of highly erodible land. Participation in the CRP is done via contracts (10-15 years in length) and currently the total area of land under contract is set to decline as per the 2014 Farm Bill. The Texas High Plains (THP) leads the US with > 1 million ha enrolled in CRP. A potential long-term benefit of CRP is to increase soil organic matter and to improve soil structure leading to increased water infiltration. Our objective was to evaluate the feasibility of using stable isotopes of water to measure and compare infiltration of rain in land under CRP management to land under continuous dryland cotton in the THP. For this purpose we selected two sites, with soils in the Amarillo series, enrolled in CRP, one for 25 years and the second site for 22 years. Results from a several rain events showed that stable isotopes of water is a method that can be used to evaluate the depth of rainwater infiltration for soils under CRP and dryland management.