Effect of nitrogen fixing cover crops on fertility of apple (Malus domestica Borkh) orchard soils assessed in a chronosequence in North-West Himalaya of Kashmir valley, India

The aim of this work was to study the effect of nitrogen fixing cover crops on soil organic carbon fractions and nutrient status in apple orchard soils in a chronosequence in north-west Himalaya of Kashmir, India. The experiment include six phases of chronosequence (0, 10, 20, 30, 40 and 50) years under three landscapes. Soil of lower altitudes with no cover crop grown in the orchard floor, the mid altitude soils with berseem (Trifolium alexandrinum) as a cover crop and in the higher altitudes with the alfalfa (Medicago sativa) grown as nitrogen fixing cover crop. There is a perceptible temperature difference across these landscapes. In addition to the apple yield and nutrients content, physical properties and soil organic fractions were investigated. Compared to the sites where no nitrogen fixing cover crops were grown there was 51% and 92% increase in the apple yield over other sites with inclusion of berseem and alfalfa. There was significant increase in yield up to 40 years and declined with advancement of stand age. Higher contents of all soil organic carbon pools were found in the higher altitudes with alfalfa grown as a cover crop in the orchard floor. Lower bulk densities were observed in the sites with cover crops grown in the apple orchard which might have synergistic role on nutrient cycling. There was significant increase of N, K, S, Mg, Fe and Mn and no discernible difference were observed for B, Cu, P and Zn. There was significant increase of the nutrients up to 40 years and afterwards significant drop was observed. Our result suggests that there was significant decrease of the nutrients from vertical soil depth of 0–90 cm.