Journal of the Indian Society of Soil Science

A screenhouse experiment was conducted using 13 coarse textured soils with DTPA-extractable Zn ranging from 0.34 to 2.09 mg kg⁻¹ to determine the critical value of Zn deficiency in soil and plants for predicting response of sorghum (Sorghum vulgare) to applied Zn. Dry matter yield of 60-day-old sorghum increased with the increase in available Zn status of the soil and a significant correlation (r = 0.86**) was observed between these two. Available soil Zn showed a significant relation with Bray's per cent yield (r = 0.79**) as well as Zn concentration in the index leaf (r = 0.98**). Both graphical and statistical methods of Cate and Nelson indicated 0.76 mg kg⁻¹ and 8.8 mg g⁻¹ as the critical values of Zn deficiency in soils and plants, respectively, below which sorghum may be expected to respond to Zn application.