Abstract:

Taking Hangzhou City of Zhejiang Province as an example, 23 low hilly red soil orchards with different plantation time were selected, and the soil samples at the piedmont, the downhill and the middle and upper slope were collected. The effects of topographic positions (natural factor) and plantation time (human factor) on soil physical, chemical and biological properties of the orchards were evaluated and analyzed. The results showed that the thickness of effective soil layer was mainly controlled by natural factors and less affected by cultivation. The thickness decreased in a sequence of piedmont > downhill > middle and upper slope. Other soil properties were affected by both natural factors and artificial farming. Soil CEC, and the content of soil organic carbon, available phosphorus, available potassium, water stable aggregates and microbial biomass carbon decreased in the order of piedmont > downhill > middle and upper slope, and the soil bulk density increased generally in the order of piedmont < downhill < middle and upper slope. Soil pH was generally higher at the piedmont than that at the downhill and middle and upper slopes. With the increase of the plantation time, soil organic carbon, available phosphorus, available potassium and microbial biomass carbon increased, soil bulk density and water stable aggregates increased first and then decreased, and soil pH decreased continuously. There were great differences in soil properties between the piedmont, the downhill and the middle and upper slope, while the differences in soil properties between the downhill and the middle and upper slope were relatively small. The effect of plantation time on soil properties was more obvious at the piedmont than that at the downhill and the middle and upper slope. Multivariate statistical analysis showed that there was synergy among the changes of soil fertility indexes, and the similarity of the changes could be roughly divided into three groups: group 1 included CEC, organic carbon, microbial biomass carbon, available phosphorus and available potassium, group 2 included pH, bulk density and available calcium, and group 3 included soil thickness and water stable aggregates. The research indicates that the spatial heterogeneity of soil quality in hilly orchards is an objective phenomenon, which is affected by natural and human factors. Therefore, the difference of slope positions and plantation time should be considered in taking management measures.

Key words: topographic position, planting time, orchard, soil properties