Effect of tillage implements on saturated hydraulic conductivity of loamy sand soil

Abstract

A field study was conducted during May - July, 2015 on loamy sand soil at the Agronomy Farm of Eastern University to compare the effect of different tillage practices on soil saturated hydraulic conductivity at 10 cm depth. The experiment was arranged in a split plot design with three replications where two types of tillage implements (mould board plough and rotovator) were assigned as main plot factors and the speed of operation of the implements such as 0.45, 0.65 and 0.85 m/s as sub plot factors. The treatment combinations were randomly distributed in each block, resulting in a total of 18 plots. Soil saturated hydraulic conductivity was measured using Guelph permeameter. The rate of fall of the water level in the reservoir was observed at 1 minute interval. One set of steady flow rate measurements was made at a constant pressure head of 5 cm water. The hydraulic conductivities were then calculated using “Guelph Permeameter Calculator” spreadsheet. Greatest hydraulic conductivity was obtained with rotovator than mould board plough due to the achieved lower bulk densities and higher porosity with rotovator. It has been documented that higher hydraulic conductivity under shallow tillage than under mould board ploughing is due to stable macro pores. Thus, the variation in size and number of macro pores in each tillage system has caused greater hydraulic conductivity values with rotovator than with mould board plough. Furthermore, inversive tillage with mould board plough made the aggregates unstable during wetting that could cause lower hydraulic conductivities. After four weeks of tillage, hydraulic conductivity was found to be decreased with increase in bulk density due to soil compaction as the hydraulic properties of soils are affected by soil compaction. The statistical analysis revealed that the tillage implements had a significant effect on hydraulic conductivity, but the operating speed did not have any significant impact on hydraulic conductivity at P <0.05. The tillage with rotovator treatments enhanced favorable soil conditions, which facilitated increased hydraulic conductivity of 9.06 mm/h. The tillage plots with mould board plough resulted in lower hydraulic conductivities. Therefore, under the soil and weather conditions of this experiment, the better tillage practice identified for improved soil hydraulic property is tillage with rotovator.