The use of cover crops and manure to retain soil moisture in Aridisols in Southern Idaho

Authors: Krecker-Yost, Jenifer; Leytem, April; Dungan, Robert - Rob; KRUGER, KEVIN - University Of Idaho; SCHOTT, LINDA - University Of Idaho

Submitted to: Waste to Worth Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/27/2022
Publication Date: 3/7/2022
Citation: Yost, J.L., Leytem, A.B., Dungan, R.S., Kruger, K., Schott, L.R. 2022. The use of cover crops and manure to retain soil moisture in Aridisols in Southern Idaho. In: Waste to Worth Conference, April 18-22, 2022, Oregon, OH. 126244.

Interpretive Summary: It is important to measure soil moisture in semi-arid regions because future models predict severe droughts and a decrease in rainfall events by up to 40%. The effects of management practices, such as reduced tillage, cover cropping, and manure application, have not been evaluated in the semi-arid and irrigated crop production area of Southern Idaho. In this study, we investigated the effects of cover crops, dairy manure, and tillage on soil physical characteristics (soil moisture, infiltration, runoff, saturated hydraulic conductivity, bulk density) and silage corn yield in silty loam soils. The objectives of this research were to: (a) determine if cover crops and dairy manure increase soil moisture, or if the cover crops were depriving the cash crop of water, (b) determine if infiltration, runoff, saturated hydraulic conductivity, and bulk density were influenced by cover crops and dairy manure, (c) determine if silage corn yield is affected by cover crops and dairy manure, and (d) determine if there are differences between tillage types. From this research, we found that the use of winter cover crops and fall applied solid dairy manure did not improve soil moisture in the semi-arid and calcareous soils in Southern Idaho. Although some research has shown improvements in soil moisture, soil physical properties, and dry biomass yield when using reduced tillage practices, there were no differences between reduced tillage and conventional tillage. Silage corn yields tended to be highest in the manure only plots and lowest in the cover crop plus manure plots, however there were no treatment differences in three of the six years of the study. Using triticale as a winter cover crop would be beneficial to increase total dry biomass yields in dairy systems that would like to increase their forage production, however it is not advised if a producer is only looking to increase silage production.

Technical Abstract: It is hypothesized that cover crops aid in retaining soil moisture because they provide ground cover, which decreases water evaporation from the soil surface. Manure application has also been shown to increase soil moisture in some soils due to an increase in organic carbon. However, the effects of these practices have not been evaluated in the semi-arid and irrigated crop production area of Southern Idaho. The goal of this study was to determine if cover crops and manure increase the water holding capacity of the soil, or if the cover crops were depriving the cash crop of water. The field experiment was located on the USDA-ARS Northwest Irrigation and Soils Research farm in Southern Idaho and was conducted from 2016-2020. The study was set up as a split-plot design with repeated measures with tillage as the experimental factor (direct seeding vs disk/chisel plow) and treatment as the sub-factor (cover crop with manure, cover crop without manure, no cover crop with manure, no cover crop without manure). From 2016 to 2021, the plots (12m wide and 12m long) were cropped with continuous silage corn with triticale utilized as a winter forage cover crop and planted directly after manure application and harvested within one week of corn planting. Stockpiled dairy manure was applied at a rate of 67 Mg ha-1 (dry weight) in the fall after corn silage harvest and incorporated by disking or left on the surface. Soil moisture data was collected using a neutron probe, and data was recorded every 15 cm in the top 1.5 m of soil. Neutron probe data was collected throughout the year and was collected more frequently during the growing season. Based on the 2016-2021 datasets, soil moisture was significantly different by collection date for each year; however, tillage and treatment did not influence soil moisture throughout the year. From planting to harvest in 2019-2021, the total water storage in the top 60 cm in the cover crop with manure plots was significantly lower than the no cover crop with manure plots, suggesting that cover crops are depriving the cash crop of water. Results from this study will provide insight to growers on the effects of cover crops and manure application on water availability to their cash crops.