Some effects of orchard soil management on sward composition, levels of available nutrients in the soil, and leaf nutrient content of mature ‘Golden Delicious’ apple trees

Abstract

The effects of soil management practice on sward composition, the levels of available nutrients in the soil and leaf nutrient content of 11-year-old ‘Golden Delicious’ apple trees were examined over a 3-year period. The treatments consisted of: (a) grass sward mown at either 9 cm or 18 cm high, or controlled with the use of grass suppressant maleic hydrazide; (b) total herbicide coverage using simazine/paraquat or terbacil; (c) clean cultivation. Within the tree rows, beneath the tree canopies, the sward was composed of a higher percentage of weeds and grass and a lower percentage of clover than the sward in the alleys. In both areas, the magnitude of the clover component in the sward was in the order: grass suppressant > short grass > long grass. Over the 3 years, the mean dry-matter yield of herbage clippings returned was 11 938 kg ha −1 year −1 in the long-grass treatment, and 9089 kg ha −1 year −1 in the short-grass treatment. This was reflected in the higher amounts of mineral nutrients returned in the herbage clippings from the former treatment. In general, the surface soil (0–10 cm) from grassed plots contained more exchangeable Ca and Mg and less NO 3-N than that from the non-grassed plots. Available P accumulated in the surface layer of the herbicide-treated plots. No significant differences in available nutrients were detected below 10 cm soil depth. Over the 3 years, soil management practice had no measurable effect on tree growth or crop yield. However, in the second and third seasons, trees from grassed plots tended to have lower leaf total N contents than those from non-grassed treatments, while trees from cultivated plots tended to have lower leaf K levels than trees from other plots.