Land use and tillage effects on soil hydraulic properties: Does infiltration method matter?

Abstract

Land use and tillage are important factors influencing soil hydraulic properties. However, associated results are usually controversial partly due to different measurement methods involved. The aim of this study was to explore whether measurement method affects the response of soil hydraulic properties to land use and tillage. For this purpose, infiltration experiment were done two times (i.e. pre-tillage and post-tillage) at the surface layer of two land uses (i.e. pasture and cropping land) in a silt loam textured soil at Lincoln, New Zealand. Based on the scoring with seven criteria including cost, operation, and information content, four methods, including one lab method (constant head and tension table with intact core, IC) and three field methods (Beerkan Estimation of Soil Transfer, BEST; tension infiltration, TI; double ring infiltration, DRI) were used to obtain saturated hydraulic conductivity (Ks), unsaturated hydraulic conductivity (Kun) (except for DRI method), and soil water retention curves (with IC and BEST methods only). Overall, method and tillage did not affect Ks, while cropping land had significantly higher LgKs value than pasture land (LgKs of 1.31 versus 1.16 mm h-1). However, methods had significant (p<0.001) interaction with land use and tillage, indicating that land use and tillage effect on Ks was affected by method. The field methods corresponded to higher Ks value in cropping land and post-tillage, whereas the lab method showed the opposite. Memory of the tillage effect on Ks was retained for Kun. The BEST and TI methods corresponded to higher Kun for post-tillage, while the IC method showed the opposite. The BEST method underestimated soil water content, partly because of the overestimation of shape parameter n and underestimation of sorptivity due to the high initial soil water content. This study indicates that method can influence the response of hydraulic properties to land use and tillage effects, and methods (i.e. field or lab method) should be selected depending on the particular application purpose.