Nitrogen-Fixing Cover Crops and Chronosequential Effects on Fertility of Apple Orchard Soils

Abstract

The aim of this work was to study the effect of nitrogen-fixing cover crops and chronosequential impact on physical, chemical and biological properties on the apple orchard ecosystem in the northwest Himalaya of Kashmir, India. The experiment includes six phases of chronosequence (0, 10, 20, 30, 40 and 50) years grown under three altitudes: soil of lower altitudes with no cover crop grown on 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. Zero stand age groups of apple trees along with no cover crop act as control for treatment comparison. All the soil indicators essential for soil health were measured. 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 in N, K, S, Mg, Fe and Mn, and no discernible difference was observed for B, Cu, P and Zn. There was significant increase in the nutrients up to 40 years, and afterward, significant drop was observed. Our result suggests that there was significant decrease in the nutrients from vertical soil depth of 0–90 cm.