Land use and tillage effects on soil saturated hydraulic conductivity: does infiltration method matter?

Abstract

The detrimental effects of tillage on soil hydraulic has been a focus of research for many years and is still widely researched globally. Tillage is used to prepare a seedbed to ideal conditions for plant establishment and growth. Intensification and increase in agricultural production has led to increased concerns around tillage. Understanding how tillage effects the soil hydraulic properties is crucial in determining how to move forward with a sustainable focus. This study focuses on the effects of tillage in different land uses, using four different measurement methods. Land uses include pasture and cropping (oats) before tillage. The methods used include the tension infiltrometer, intact cores using constant head in the laboratory, Beerkan estimation of soil transfer procedure (BEST) and constant head double ring infiltration The purpose of this study is to investigate the interaction between tillage and land use which has not been conducted in previous studies. For each method investigated there is a significant effect due to tillage and land use effect. The two types of methods that have been used include infiltration data when the soil is unsaturated or saturated. Tension infiltrometer and BEST method are unsaturated methods used to determine Ksat whereas the constant head double ring infiltration and intact cores under a constant head are saturated methods. There is no significant difference in Ksat within the unsaturated or saturated methods at each land use either before or after tillage. But there is a significant difference between each of the saturated methods and unsaturated methods. The BEST method showed that in the pasture system the Ksat increased by 40.7% as a result of tillage compared to the crop system where the Ksat increased by 47.9% as a result of tillage. The tension infiltrometer showed that in the pasture system the Ksat increased by 88.3% as a result of tillage compared to cropping decreased by 13.4% as a result of tillage. The constant head double ring infiltration showed that in the pasture system the Ksat reduced by 44.6% as a result of tillage whereas in the cropping system it increased by 48.6%. The intact core under constant head showed that before tillage occurred, the pasture had a slower log 10 Ksat than the cropping system by 22.9% compared to after tillage the pasture was slower than cropping by 33%. The difference in bulk density, porosity and soils structure before and after tillage influences the results, as saturated flow and unsaturated flow in the field vary. The unsaturated methods result in higher Ksat in cropping land use and after tillage compared to the saturated methods that resulted in higher Ksat under pasture system and before tillage. The higher the bulk density of the soil (before tillage or pasture land use), the more appropriate the saturated methods used may be. This shows that the pasture and the before tillage systems have similar soil properties and the cropping and after tillage systems are also similar.