Effects of long-term conservation tillage on soil physical quality of rainfed areas of the Loess Plateau

Long-term field experiments on soil physical quality in rainfed farming systems were conducted in Dingxi on the western Loess Plateau.The effects of conventional tillage and five conservation agriculture patterns [conventional tillage(T),conventional tillage with stubble incorporation(TS),no till with no stubble(NT),no till with stubble retention(NTS),conventional tillage with plastic mulching(TP) and no till with plastic mulching(NTP)] were studied.The experiment was fully-phased with two rotation sequences.Phase 1 started with field pea(Pisum sativum) followed by spring wheat(Triticum aestivum)(P→W) whereas phase 2 started with spring wheat followed by field pea(W→P).There were highly significant differences between the six tillage measures in soil properties including soil aggregates,available water content,water use efficiency and saturation conductivity.There were also significant differences in some soil properties including soil bulk density,total porosity,capillary porosity,non-capillary porosity,soil strength and saturation capacity.There were no significant differences in soil properties such as soil temperature and field capacity.Using the addition and multiplication method,and weighted integrated method,quantitative assessments of soil physical quality in different tillage systems were carried out.The order of soil physical quality index from high to low was NTS,NTP,NT,TS,T(TP) and TP(T) in P→W rotation,and NTS,NTP,TS,NT,TP and T in W→P rotation.The various tillage measures resulted in very different soil physical quality levels.Improved soil structure arose from tillage reduction or residue retention which improved soil structure,enhanced water infiltration,reduced soil and water loss,and hence improved soil physical quality.