Zinc Nutrition of Horticultural Crops with Emphasis on Yield and Quality

摘要

Coarse textured soils of high soil pH, under intensive cropping and heavy fertilisation with macronutrients, inadequate organic manuring, have aggravated Zn deficiency in horticultural crops. The corrective measures involve application of ZnSO4 either to the soil or to foliage as sprays. The latter is more popular because of its economy, ease and effectiveness. Aqueous solutions of ZnSO4 of >0.5% concentration used for foliar sprays tend to be acidic enough to scorch and harm foliage. Customarily the spray solutions are neutralized with slaked lime solution to overcome this problem. Since Zn(OH)2 is insoluble the process nullifies active Zn present in the spray solution. Alternatively un-neutralized solutions of < 0.2% concentration are useful. The multi-micronutrient formulations do not favour Zn absorption. Among horticultural crops, most fruit and vegetable-crops have shown positive response to Zn application in terms of growth, yield, quality and storage behavior of the produce. The work on ornamental, plantation and spice crops in respect of Zn is meager. The future needs evolving site or region specific management of Zn by employing Zn-fortified or zincated fertilisers to attain balanced nutrition, evaluation of mobilization of Zn to edible parts as related to human nutrition and development of cultivars/ rootstocks genetically efficient to absorb adequate Zn from marginal soils and as also to tolerate toxic levels in the soils. Further, there is need to differentiate between active fraction of Zn in the plant as against total Zn content to aid proper diagnostic and advisory work.