Assessment of aggregate stability methodologies for calcareous silty soils in Idaho's Magic Valley

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

Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Abstract Only
Publication Acceptance Date: 12/4/2022
Publication Date: 2/13/2023
Citation: Schott, L.R., Yost, J.L., Kruger, K., Leytem, A.B., Dungan, R.S. 2023. Assessment of aggregate stability methodologies for calcareous silty soils in Idaho's Magic Valley [abstract]. American Society of Agricultural and Biological Engineers International (ASABE). Paper No. 23040.

Interpretive Summary:

Technical Abstract: Idaho ranks in the top 10 in the U.S. for dairy, potato, barley, hay, sugar beet, corn silage, and dry bean production. The highest producing areas in the state for these commodities are in southern Idaho where irrigation is necessary. Water quality is impaired in the region but has been improving due to some best management practice implementation. To measure progress in producer efforts for reducing erosion and runoff, appropriate methods need to be identified. The soils in this region are prone to crusting, have low organic matter, and are high in calcium carbonates making these soils unique to much of the U.S. Thus, the overall goal of this project was to identify the best method for the assessment of aggregate stability properties. Two study sites were located on the USDA-ARS Northwest Irrigation and Soils Research Laboratory in Kimberly, Idaho, and were established in 2013 (Long-Term Manure) and 2016 (Cover Crop). A randomized complete block design with four replicates was used for the Long-Term Manure study; plots were under different manure and fertilizer treatments. Briefly, the study design consisted of eight treatments: three rates solid dairy manure applied annually or biannually, a control (no fertility additions, and inorganic fertilizer only. The cover crop study was set up as a split-plot design with four replications with tillage as the main experimental factor (direct seeding vs disk/chisel plow) and treatment as the subfactor (cover crop with manure, cover crop without manure, no cover crop with manure, no cover crop without manure). Both studies were assessed for soil physical properties in late summer 2020. Three methods were used to measure soil aggragate stability: wet sieving, a hybrid method utilizing a Cornell Sprinkle Infiltrometer (CSI; van Es and Schindelbeck, 2001), and the Slakes mobile application (Fajardo & McBratney, 2019). For the wet sieving method, samples were submerged in water and oscillated at 30 oscillations min-1 for 10 min. A CSI was used to measure soil aggregate stability at the heights of 30, 90, and 150 cm. The CSI operated at a constant rainfall rate of 2 cm of rainfall per 10 min of operation. Soils data were analyzed using a linear mixed-effects model (lme function) using the nlme package in R. No differences in aggregate stability were found when the wet sieving method was used among treatments for both studies. However, the CSI hybrid method was found to be statistically different at an operational height of 30 cm among treatments at mean values of 3.73 ± 0.36 mm (cover crop with manure), 3.67 ± 0.38 mm (cover crop only), and 3.70 ± 0.30 mm (manure only) as compared to the control (3.13 ± 0.46 mm) for the Cover Crop study. There were also statistical differences found at an operational height of 90 cm between cover crop + manure (3.14 ± 0.86 mm) and cover crop only (2.54 ± 0.54 mm). However, none of the treatments were different from the control. Further, mean weight diameters (MWD) were different between the CSI and wet aggregate seiving method. Average MWD for the wet seiving method in the Cover Crop study ranged from 1.1 ± 0.40 mm (control) to 1.5 ± 0.32 mm (cover crop + manure). For the hybrid CSI method, MWD measured under the heighest operational height (150 cm) were the closest to the wet seiving method; MWD ranged from 2.0 ± 0.62 mm (control) to 2.4 ± 0.54 mm (cover crop + manure). These initial results not only have implications on which methods are best for assessing progress, but also what management practices can be utilized to decrease water erosion from irrigated cropland. Under these soil conditions, the CSI hybrid method was more sensitive to management change than the traditional wet seiving method. The CSI hybrid method better captures and assesses typical erosion processes occuring in irrigated crop land.