Effect of potassium fertilizers and application time on the yield of wheat and evaluations of their efficiency in two farms in West Azarbaijan

Among growth factors, proper nutrition plays an important role in increasing yield and the quality of wheat grain. In order to investigate the effect of different sources of potassium (K) fertilizers management on some qualitative and quantitative characteristics of wheat, two experiments were implemented in two fields with lower and higher critical level of K (Kava=125 and Kava= 412mg kg-1) in a randomized complete block design with five treatments and four replications in West Azarbayjan province in 2017-18. Treatments were as follows: T1 = control (use of all essential nutrients based on soil test except K-fertilizer; T2 = T1 + sulfate of potassium(SOP) before planting; T3 = T1 + consumption of 50% K from (SOP) before planting and 50% from morate of potassium(MOP) in two topdressing; T4 = T1 + consumption of 50% K from SOP before planting and 50% from soluble sulfate of potassium(SSOP) in two topdressing; T5 = T1 + consumption of 50% K from SOP before planting and 50% from SSOP+Zn-EDTA in two topdressing periods during the first stem elongation and wheat heading. The results of this study revealed that a) in the farm with lower available K, K-fertilizers had a significant effect on grain yield, harvest index, biomass and protein content of wheat grain. But, in the farm with higher available K, the use of K-fertilizers had no significant effect on the above growth factors. b) topdressing of SSOP+Zn-EDTA compared to other K-fertilizers, due to having available K, Zn and SO4, had increased grain yield, protein, straw weight and Zn content. c) topdressing of potassium fertilizers, compared to T2 treatment, significantly increased grain yield and protein content and fertilizer use efficienciy. While potassium fertilizer use efficiency in T2 was 5 kg kg-1, it was improved in the T3 and T4 treatments to six and in the T5 treatment increased up to 8 kg kg-1, respectively. d) While farmer’s income in T2 treatment was 7 million rials per hectare, in the T3, T4 and T5 were 12, 9 and 16 million rials per hectare, respectively. While the superiority of T5 over other treatments has been proven, it is highly recomented that this experiment be further tested and evaluated in all agricultural crops.