Infiltration and soil water distribution in irrigation furrows treated with polyacrylamide

Authors: Lentz, Rodrick; Bautista, Eduardo; Koehn, Anita; SOJKA, R - Retired ARS Employee

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2020
Publication Date: 10/23/2020
Citation: Lentz, R.D., Bautista, E., Koehn, A.C., Sojka, R.E. 2020. Infiltration and soil water distribution in irrigation furrows treated with polyacrylamide. Transactions of the ASABE. 63(5):1451-1464. https://doi.org/10.13031/trans.13939.
DOI: https://doi.org/10.13031/trans.13939

Interpretive Summary: Furrow irrigation, whereby water is directed across cropped fields in small surface channels under gravity flow, is a common irrigation practice employed worldwide. Though energy efficient, furrow irrigation causes soil erosion and does not apply irrigation water uniformly down the furrow, resulting in substantial losses of water and crop nutrients and degradation of soil and water quality. The addition of minute quantities of water-soluble anionic polyacrylamide (WSPAM) to irrigation water greatly reduces soil erosion in furrows but WSPAM’s influence on furrow infiltration uniformity and soil water distribution is poorly understood. This study shows that WSPAM managed furrows apply irrigation water more uniformly than non-WSPAM furrows. And while overall net infiltration was the same for the two approaches in each irrigation, WSPAM-treated soils contained 1.2-times more water than non-treated soils. The WSPAM management approach, while protecting against furrow erosion, provides a means of improving irrigation uniformity and could potentially reduce total water use, percolation water losses, and nutrient contamination of surface and groundwater.

Technical Abstract: Few if any studies have measured water-soluble anionic polyacrylamide’s (WSPAM) effects on infiltration and soil water distribution in different segments of irrigation furrows. We conducted a three year study on a silt loam soil with 1.5% slopes, planted to corn. Control furrows received no WSPAM and inflows were 15.1 L/min, whereas WSPAM was applied using 8 mg/L a.i. to 45 L/min inflows during furrow advance. After advance, treatments were identical, with inflows of 15.1 L/min. Soil profile water content and net infiltration in upper (inflow-end) and lower (outflow-end) furrow sectors were measured during the growing season. The results indicate mean whole-furrow, net infiltration was the same between treatments in each irrigation. The WSPAM increased lateral wetting from furrow to planted row by as much as 1.3-fold in the lower furrow sector. Mean field-wide soil water content was an average 1.2-fold greater in WSPAM furrows than for the control, but the effect was more significant in lower furrow sectors. This was consistent with infiltration data, which showed that WSPAM decreased the upper-to-lower-sector, net infiltration ratio 33% to 40% relative to control furrows, indicating improved irrigation uniformity. A 62% reduction in furrow advance time afforded by WSPAM accounts for some of the increased uniformity, but opposing changes in infiltration rate between upper and lower furrow sectors suggests that other factors are involved. The WSPAM management approach, while protecting against furrow erosion, provides a means of improving irrigation uniformity, and could potentially reduce associated percolation water and nutrient losses.