ISHS Acta Horticulturae 557: VII International Symposium on Orchard and Plantation Systems
MULCH ENHANCES APPLE FRUIT STORAGE QUALITY |
| Authors: | A. Lang, M.H. Behboudian, J. Kidd, H. Brown |
| Keywords: | mulch, root-length density, bitter pit, mineral nutrition, storage quality |
| Abstract:
In New Zealand many apple cultivars must receive up to 12 foliar calcium sprays to raise fruit calcium level sufficiently for storage and export to distant markets. However, calcium spraying represents a significant investment in time and materials and it is not always enough. This 2-year project aimed to discover effective, more practicable and more sustainable alternatives to calcium spraying. The alternative discussed here is a combination of mulch and a surface application of gypsum. The mulch used was of black polyethylene topped with sawdust, to hold it in place and to afford mechanical protection and to provide thermal insulation. Coarse-ground gypsum was sprinkled onto the soil surface prior to applying the mulch. Trial plots each contained two trees. In each plot mulch was either present or absent, gypsum was applied at three levels and these treatments were replicated four times. For the duration of the trial, normal foliar calcium spraying was abandoned. Mulch increased root length density and brought the roots closer to the surface. The mulch also increased the concentration of calcium, potassium, and magnesium in the soil and the soil’s cation exchange capacity. These below ground changes were reflected in increases in leaf potassium and calcium. Although significant effects on fruit mineral concentration were not detected, the incidence and the severity of the calcium-related bitter pit (a serious storage disorder) was significantly reduced. The gypsum applications had no significant effect on any of the variables measured. It is concluded that mulching is a sustainable and low input management option that enhances apple fruit quality. This beneficial effect is apparently mediated via improved growth and distribution of feeder roots and via improved soil nutrient cycling. | |
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