Effects of potassium on temporal growth of root and shoot of wheat and its uptake in different soils

In a pot culture experiment، the root length density، potassium concentration in crop، and total K uptake by wheat (Triticum aestivum var. HD 2285) at different growth stages (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 72 pots containing 4. 5 kg of three types of soils، namely Alfisol، Vertisol، and Inceptisol. Pots were divided into two sets، that is، with 50 mg kg-1 K as basal and another 50 mg kg-1 was top dressed at 45 days after sowing and without potassium. Optimum doses of N، 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 soil in the pot was screened carefully under moist condition to collect total roots and 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. Results show that the wheat dry matter yields increased gradually with crop age and it was more in Inceptisol followed by Vertisol and Alfisol. Potassium deficiency decreased total root length (TRL) and root length density (RLD) in the last stages of wheat growth particularly in Vertisol and Alfisol. Potassium concentration in wheat at different stages of crop growth was 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 uptake values increased sharply with the age of the crop up to 69 days after germination (FLS) ، but the rate of potassium accumulation showed a gradual decrease thereafter، in soils، which received optimum amount of potassium.