Abstract: The correlation between rhizobia distribution and the physical/chemical properties in soil of winter wheat intercropped with sweet clover in the Aksu region of Xinjiang was determined. Rhizobia numbers were counted by dilution plate method. Soil physical and chemical properties including pH, soil bulk density, total salt, organic matter, total nitrogen, alkali-hydrolyzale nitrogen, available phosphorus and available potassium were also measured. The results showed that the number of rhizobia was highest at 10-20 cm soil depth compared with 0-10 cm and 20-40 cm from sowing to cutting of sweet clover. The number of rhizobia was highest at 0-20 cm depth (6.89 lg cfu·g^-1) in July and at 20-40 cm soil depth in August (6.46 lg cfu·g^-1). Soil pH and total salt decreased 0.23%-1.40% and 3.45%-37.69% between September and April, respectively. At 0-40 cm soil depth, organic matter, total nitrogen, available nitrogen and available phosphorus decreased from April to August. However, compared with September (sweet clover harvest) organic matter and total nitrogen in August was increased 7.65%-26.98% and 16.67%-44.12%, respectively. Alkali-hydrolyzable nitrogen at 0-20 cm was increased by 20.27%-160.68%, available phosphorus by 167.74% at 10-20 cm and available potassium by 10% at 0-20 cm soil depth. The correlation between total salt and the number of rhizobia at 0-40 cm soil depth was strong and negative (r=-0.81, P<0.05. The correlations between moisture content and rhizobia numbers at 0-20 cm soil depth were also strong and negative (-0.81≤r≤-0.73, P<0.05). There was also a strong negative correlation between total nitrogen content and rhizobia numbers at 20-40 cm soil depth(r=-0.88, P<0.05). Path coefficients for total salt, organic matter and total nitrogen were generally strongly correlated with rhizobia numbers, and organic matter was positively correlated (P₅=0.56) but total nitrogen and total salt negatively correlated (P₆=-0.50, P₄=-0.64). Organic matter had the greatest positive influence on rhizobia, whereas total nitrogen and total salt reduced rhizobia.

Key words: winter wheat, sweet clover, intercropping, rhizobia, soil physical&chemical properties;