Effect of Potassium Rates and Sources on Some Quantitative and Qualitative Characteristics of Oil-Seed Sunflower in Calcareous Soils

The current study was conducted to investigate the effect of different levels and sources of potassium (K) on seed and oil yields and K uptake of sunflower (Helianthus annuus L.) var. Azargol. The experiment was laid out in randomized complete block design under split plot arrangement with three replications at two locations in West Azerbaijan province during two consecutive years (2017-18). Sunflower sources (K2SO4 and KCl) were arranged in the main plots, accommodating five K doses 0 (control), 100, 200, 300 and 400 kgha-1 in sub-plots. The results indicated that treatment of 100 kgha-1 K from K2SO4 source increased the seed and oil yields by, respectively, 44.8% and 38.6%, which did not differ from the same treatment using KCl. The highest straw weight and biomass were obtained by 300 kg.ha-1 K from K2SO4 source, which increased by 58.9% and 51.8%, respectively, compared to the control. K uptake by straw was 2.93 times more than the grain. Sunflower reduced native available potassium (Kava) by 32 mg.kg-1. K uptake in grain was 141.2 kg.ha-1, which enhanced with increasing potassium level treatments. The soil Kava was proportional to potassium level treatments. The maximum soil Kava was 410 mg.kg-1, with application of 400 kg.ha-1 of K. In this connection, K sourcaes had the same effect. The results suggested that by application of 100 kg K.ha-1  from K2SO4 or KCl in oil-seed sunflower cultivation, in addition to producing a suitable product, Kava of the soil is maintained in optimum range.