Studies on correlations between endomycorrhizai and Azotobacter population with growth, yield and soil nutrient status of apple orchards in Himachal Pradesh

摘要

The productivity and the diversity of apple tree under natural ecosystems are frequently dependent upon the presence and activity of mycorrhiza. Keeping ir. view the capacity of AM fungi to form useful associations with apple trees growing in diverseecosystems of North-Western Himalayan region and to ascertain the influence of soil and cultural practices on such associations, a survey was undertaken in 80 apple orchards. These studies have shown that the frequency and decree of infection of endomycorrhizae bear a direct effect on growth and yield of the tree. Positive correlation was observed between mycorrhizal spore population in the rhizosphere soil with leaf area, crop yield and per cent of mycorrhizal infection in the roots. But proportion andintensity of colonization were negatively correlated with soil P and Zn status. Higher status of N and organic carbons have shown positive relationships with microbial population and root colonization. Azotobacter chroococcum counts in the soil have also shown a positive relationship with organic carbon content of soil, shoot extension growth and yield of apple trees. Leaf N, P, Cu and Zn contents were also positively and significantly correlated with yield. However, Azotobacter count was positively and significantly correlated with leaf N but negatively and significantly with leaf K.