Correlation analysis of soil physical and chemical properties under different planting patterns of blood orange garden in hilly areas of Chongqing City

Agroforestry, as a form of land use, is an effective technique to preserve mountain ecology and environment. To evaluate the ecological benefits of mountain agroforestry for guiding future land use planning, the physical and chemical properties of the 0 10 cm and 10 20 cm soil layers of agroforestry patterns of blood orange-sweet potato (I), blood orange-peanut (II), blood orange-maize (III), blood orange-eggplant (IV) and pure blood orange (V) were evaluated by using a grey correlation analysis. The paper also comprehensively discussed the differences in effects of different patterns on soil bulk density, soil porosity and soil nutrients contents in blood orange key demonstration area of Hebian Town of Bishan County, Chongqing City. The results suggested that soil bulk density, non-capillary porosity, total porosity, and contents of soil organic matter, total nitrogen, alkali-hydrolysis nitrogen, available phosphorus and available potassium under the same cultivation pattern were significantly lower in 0 10 cm soil layer than those in 10 20 cm soil layer. Also capillary porosity, total phosphorus and total potassium of different soil layers under the same cultivation pattern were not significantly different between two soil layers. Differences in soil bulk density, porosity and soil nutrients contents in the same soil layer among different cultivation patterns were either significant (P < 0.05) or extremely significant (P < 0.01). Soil bulk density was highest and non-capillary porosity, total porosity, and contents of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolysis nitrogen, available phosphorus and available potassium lowest under pure blood orange. However, the total potassium in the 0 10 cm soil layer was slightly higher under pure blood orange than under blood orange-peanut pattern, and those in the 10 20 cm soil layer lowest. Contents of soil organic matter, total nitrogen and alkali-hydrolysis nitrogen of the 0 10 cm soil layer were highest under blood orange-maize pattern. Under blood orange-eggplant pattern, soil organic matter and available potassium contents in the 10 20 cm soil layer were highest. Then under blood-sweet potato pattern, total phosphorus and total potassium contents were highest. Also under blood orange-peanut pattern, available phosphorus content was highest. A comprehensive evaluation of the improvement in soil nutrients of different agroforestry patterns was done using grey correlation analysis. Based on the analysis, the order of improvement in soil nutrients in the 0 10 cm soil layer was blood orange-sweet potato > blood orange-maize > blood orange-eggplant > blood orange-peanut > pure blood orange. It was blood orange-sweet potato > blood orange-eggplant > blood orange-maize > blood orange-peanut > pure blood orange for the 10 20 cm soil layer. Surface vegetation diversity, below-ground root system distribution, and biological and ecological characteristics of each cultivation pattern were the main reasons for the differences in soil physical and chemical properties.