Effect of Tillage and Cover Crops on Soil Macroporosity and Hydraulic Conductivity.

Measurements of soil macroporosity and hydraulic properties such as saturated (K_s) and unsaturated hydraulic conductivity [K (Ψ) ] are important for characterizing the rate of water flow and the fate of contaminant transport across the vadose zone. The main objective of this study is to determine the effect of tillage and cover crops on macroporosity and hydraulic conductivity of Abilene clay loam soil at the Texas A&M AgriLife Research station at Chillicothe in the Texas Rolling Plains. In situ infiltration tests were conducted during June-July, 2015 in the experimental plots under three different treatments of conventional till, no-till and no-till with cover crops. Three infiltration measurements were made in each of three replicated plots, resulting in a total of 27 measurements. Infiltration measurements were conducted at -25, -20, -15, -10, -5 and 0 cm pressure head using a tension infiltrometer. In addition to infiltration measurements, soil samples were also collected near infiltration measurement sites to analyze for soil properties including soil texture, soil moisture, bulk density, electrical conductivity and soil nitrate. K_s and K (Ψ) were calculated from the steady state infiltration rate using Wooding’s equation. Initial results showed that significantly higher K_s and K (Ψ) at -20, -15, -10 and -5 cm pressure were observed in the no-till plots with cover crops compared to conventional till and no-till plots. Soil macroporosity parameters such as hydraulically active macroporosity, effective macroporosity and number of pores will be derived using soil infiltration data at different suctions pressures. Another set of infiltration tests will be conducted in these plots during October, 2015 after cotton is harvested, and finally the effects of tillage and cover crops on soil hydrologic properties will be studied.