Site Position, Tillage, and Soil Depth Effects on Soil Properties in a Furrow-irrigated Rice Field on a Silt-loam Soil

The fundamental agronomic shift from conventional agricultural methods to conservation agriculture relies on understanding soil nutrient stratification with depth and under different tillage treatments. Assessment of nutrient stratification in the dynamic conditions of furrow-irrigated rice (Oryza sativa) systems in eastern Arkansas is absent. The objective of this study was to evaluate the effects of tillage [i.e., conventional tillage (CT) and no tillage (NT], site position (i.e., up-, mid-, and down-slope), soil depth interval (i.e., 0-10 and 10-20 cm), and their interaction on the difference (i.e., end of the season minus beginning of the season) in select soil chemical properties (i.e., pH, EC, P, K, Ca, Mg, S, Na, Fe, Mn, Zn, TN, TC, and SOM) over the 2019 growing season in a furrow-irrigated rice field on a silt-loam soil in eastern Arkansas. Soil K content decreased ~10 times more under CT than NT, while soil Mg, Ca, and Mn decreased 70%, 160%, and 34% respectively more and soil Fe increased 38% more under NT than CT. Soil Fe and TN increased 112% and 194% respectively more in the 10-20 than in the 0-10 cm depth interval, while pH, Na, and Ca decreased on average more than 5 times at the up-slope position in the 10-20 depth interval than in the other site position-soil depth combinations. Soil P, TN, TC, and SOM increased on average more than 5 times at the down-slope position under NT. Soil Fe increased 4 times more at the down-slope than at the other two site positions. Results confirmed that the dynamic near-surface soil conditions in a production-scale, furrow-irrigated rice field require best management practices along the predominant slope of the field.