Effect of Potassium Fertilizers Management on Some Quantitative and Qualitative Characteristics of Wheat

Among growth factors, proper nutrition plays an important role in increasing yield and the quality of wheat grain.  Wheat in most human societies is a strategic product and the main supplier of protein and calories needed by communities. Among growth factors, proper nutrition plays an important role in increasing yield and the quality of wheat grain. Potassium (K) is the most abundant cation in the cytoplasm of the plant and plays an important role in plant physiological functions. Its deficiency reduces the qualitative and quantitative yield of crops. It is an essential component in the basic stages of protein biosynthesis. Its deficiency results in a decrease in wheat protein. The results showed that a small amount of potassium was needed in the establishment and wintering stages of wheat and it was highly required at the later stages of plant growth and the plant requirement reached its maximum in flowering stage. This illustrates the importance of taking potassium partition. Among the low nutrient elements, Zinc (Zn) is the most important element that is clearly deficient in calcareous soils. Zinc is essential for enzymatic activities and increases the protein, carbohydrate and gluten of wheat grains.

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 conducted 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 + whole sulfate of potassium (SOP) before planting; T3 = T1 + consumption of 50% K from (SOP) before planting and 50% from muriate 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. Basal elements based on soil analysis results were as follows: at site one, containing 250 kg ha-1 potassium fertilizer, 150 kg ha-1 triple superphosphate and 100 kg ha-1 pre-planting urea fertilizer, and at site two potassium and urea similar to site one and 75 kg ha-1 triple phosphate. Topdressing 120 kg urea ha-1 was used in two stages i.e. the first stem node and the emergence of cluster at both locations. The size of the plots was 4 m2 and the interval was 2 m. Mihan cultivar was planted at a density of 500 seeds m-2 and 180 kg ha-1 using a linear grain harvesting machine. After determination of yield parameters, soil and plant composite samples were prepared and taken to the laboratory. Physical and chemical analysis of soil was performed using conventional methods at the Soil and Water Research Institute. Statistical analysis of data for different traits at two locations was performed using SAS statistical software version 9.1. Mean comparisons were undertaken using Duncan's multiple range test at the 5% level of probability.

The results of this study revealed that in the field (1), K-fertilizers increased grain yield and protein content. In this field, T5 was the best treatment in comparison with the other treatments. Split application of SSOP+Zn-EDTA was the best treatment and increased potassium fertilizer efficiency (KUE). Topdressing of SSOP+Zn-EDTA compared to other K-fertilizers, due to having available K and Zn, increased the kernel, grain yield, grain protein, straw weight and Zn content. While KUE in T2 was 5 kg kg-1, it became 6 kg kg-1 in T3 and T4 , and increased up to 8 kg kg-1 in T5. However, in the field (2) due to its higher content of available K, application of K-fertilizers had no significant effects in all treatments. In the field (1), applying the optimum amount of fertilizer (T3), increased wheat yield by 1300 kg ha-1 compared to the control treatment. However, T5 increased the yield and fertilizer efficiency by 11% and 60%, respectively, even with respect to T3. Therefore, split application of K-fertilizers should be conducted based on the soil analysis result.

Topdressing of soluble sulfate potassium +Zn-EDTA compared to other K-fertilizers, due to having available K, Zn and SO4, increased grain yield, protein, straw weight and Zn content, and fertilizer efficiency.