Evaluation of Critical Limits of Potassium in Soil and Plant for Kharif Brinjal Grown on Shrink-Swell Soils

The critical limits of potassium in soil and plant was determined through a pot culture experiment with soils from eighteen different locations were collected having low (<125 kg K₂O ha⁻¹), medium (125–250 kg K₂O ha⁻¹) and high (>250 kg K₂O ha⁻¹) potassium status. The dry matter yield of brinjal plant ranged from 9.56 to 13.12 g pot⁻¹ amongst 18 locations. There was a significant increase in dry matter yield due to application of potassium. The critical limit of potassium in soil for brinjal plant was found 270.00 kg K ha⁻¹ by graphical method of Cate and Nelson (1965) and 274.40 kg K ha⁻¹ by statistical method of Cate and Nelson (1971), respectively. The critical limit of potassium in brinjal plant at initiation of flowering for shrink-swell soils was found 2.36 per cent by graphical method and 2.39 per cent by statistical method, respectively. The results indicated that, soil containing less than 274.40 kg K ha⁻¹ and brinjal plant containing less than 2.39 per cent potassium at initiation of flowering, respond to application of potash fertilizers.