|FAUST, DEREK - Clover Park Technical College|
|BAWA, ARUN - South Dakota State University|
|KUMAR, SANDEEP - South Dakota State University|
Submitted to: Agrosystems, Geosciences & Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2020
Publication Date: 1/27/2021
Citation: Faust, D.R., Liebig, M.A., Toledo, D.N., Archer, D.W., Kronberg, S.L., Hendrickson, J.R., Bawa, A., Kumar, S. 2021. Water quality of an integrated crop–livestock system in the northern Great Plains. Agrosystems, Geosciences & Environment. https://doi.org/10.1002/agg2.20129
Interpretive Summary: Agriculture is challenged to produce more food and fiber products and to do so in an environmentally sustainable manner. Integrated crop-livestock (ICL) systems may help in meeting this challenge. However, water quality impacts of ICL systems must be understood. This study used rainfall simulations to examine surface runoff and water infiltrating into soil for different vegetation types in a long-term ICL system. Grazing effects were also studied by conducting both pre-graze and post-graze rainfall simulations. Results indicated that surface runoff nitrate-nitrogen and ammonia-nitrogen concentrations and nitrate-nitrogen and phosphate-phosphorus concentrations of infiltration water were greater in cover crop and wheat compared to grass pasture. In conflict with previous studies, pre-graze nitrogen and phosphorus concentrations were greater compared to post-graze, perhaps due to snowmelt occurring before the post-graze rainfall simulations. Effects on the quantity and quality of water infiltrating into the soil were greater than effects on runoff in this flat, semiarid landscape. These results are useful to policy makers, regulatory agencies, researchers, and producers in understanding how adoption of ICL systems could affect water quality in a semiarid region. Yet, more studies assessing water quality in ICL systems are needed to better understand dynamics in different regions and climates.
Technical Abstract: Integrated crop-livestock (ICL) systems may improve environmentally sustainable production of agricultural products. Impacts of ICL systems on water quality have not been well studied, particularly in semiarid climates, thus impeding sustainability evaluations of these systems. Water quality parameters were quantified for two 30-minute rainfall simulations in wheat-cover crop, cover crop, and rangeland grass control phases of a long-term ICL study site in Mandan, ND in 2017 and 2018. Both pre-graze and post-graze simulations were conducted. Rainfall rate was typical of a 50-year rainfall event for the region. Nitrate-N (NO3--N), nitrite-N (NO2--N), ammonia-N (NH4+-N), phosphate-P (PO43--P), and total suspended solid (TSS) concentrations and loads were evaluated in surface water, along with concentrations of NO3--N, NO2--N, NH4+-N, and PO43--P concentrations in infiltration water. Non-parametric ranked two-way analysis of variance was used to evaluate differences for vegetation type and grazing as fixed effects, with year as a random effect. Surface runoff concentrations of NO3--N and NH4+-N were significantly different following the general trend cover crop = wheat > grass. A grazing effect was also observed with pre-graze significantly greater than post graze for NO2--N, NH4+-N, PO43--P, and TSS surface runoff concentrations. For infiltration water concentrations, similar significant effects of vegetation type were observed for NO3--N and PO43--P, while pre-graze was also greater than post-graze for NO2--N and PO43--P. Due to variable runoff volumes, no significant differences were observed for loads of any parameters. Minimal runoff volumes (0 to 6.7 L) and significant vegetation and grazing effects in nutrient infiltration water concentrations highlight the importance of infiltration in such studies, particularly in semiarid landscapes with flat topography. More studies assessing water quality are needed to better evaluate overall environmental sustainability of ICL systems.