Zinc fertilizer application in rice crop: Why, when and how

Abstract

Zinc deficiency is an important disorder in lowland and aerobic rice. High soil pH drastically reduces zinc availability. Intensive cereal cropping over years also leads to zinc deficiency. The symptoms appear on the second or third leaf from top, at about 2 to 3 weeks after transplanting. Rice leaves develop brown blotches and streaks that may fuse to cover older leaves. Zinc deficiency for prolonged period reduces plant height, tillering and grain yield and in severe cases plants die. Regular consumption of low zinc rice induces stunted growth, improper development, low intelligence and diseases due to low immunity. Zinc deficiency in rice plant can be managed by fertilizer application, water management, soil amendment, crop diversification and organic matter application. Water soluble zinc sulphate can be sprayed on leaves, and zinc oxide can be administered as a root dip for seedlings. Due to its acid-forming properties and abundant sulphur, zinc sulphate is the best solution for sodic soil. To prevent initial loss, zinc fertilizer should be administered early. Foliar treatment throughout boot leaf to blooming is desired to obtain zinc-rich grain or seed.