Effect of potassium on root length density of wheat at different stages of growth

In pot culture experiment, the root length density, potassium concentration in crop, and total K uptake by wheat (var. HD 2285) at different growth stages namely, CRIS (Crown root initiation stage), MTS (Maximum tillering stage), FLS (Flag leaf stage) and DFS (Dough formation stage) were determined. Wheat crop was grown in pots containing 4.5 kg of three types of soils, namely Alfisol, Vertisol, and Inceptisol. Pots were divided into two sets, that is, with K (50 mg K kg⁻¹ as basal and another 50 mg K kg⁻¹ was top dressed at 45 days after sowing) and without potassium. Optimum doses of N and P and other macro- and micro-nutrients were given to the crop. At different stages of wheat growth (22, 41, 69, and 87 days after germination), the shoot was harvested and the whole of the soil in the pot was screened carefully under moist condition to collect total roots for measuring the root volume and mean root diameter. Using root volume and mean diameter of root, total root length and then root length density were calculated. Wheat dry matter yields increased gradually with crop age and it was more in Inceptisol followed by Vertisol and Alfisol. Potassium deficiency resulted in a decrease in total root length (TRL) and root length density (RLD) in the later stages of wheat growth, particularly in Vertisol and Alfisol. Potassium concentration in wheat and at different stages of crop growth was also found to be less in Alfisol than in Vertisol and Inceptisol. At different stages of wheat growth, potassium uptake (mg pot⁻¹) was found to be less in Alfisol than in Vertisol and Inceptisol. The K uptake values increased sharply with age of the crop up to 69 days after germination (DAG), but the rate of K accumulation showed a gradual decrease thereafter, in soils which received fertilizer potassium.