GRAIN YIELD AND PROTEIN OF BARLEY IN DEPENDENCE OF PHOSPHORUS AND POTASSIUM NUTRITION

The different levels of phosphorus and potassium nutrition on the productivity of two-rowed winter barley (Hordeum vulgare L.) cv. Kamenitza were studied under conditions of pot experiments. Two greenhouse pot experiments with increased nitrogen, phosphorus, and potassium fertilizing levels were conducted. The effect of potassium fertilization and different levels of nitrogen fertilizing was studied at the first experiment. The investigated nitrogen levels were 0, 200, 400 and 600 mg N/kg soil and the levels of potassium fertilizing were 0, 200, 400 mg K2O/kg soil. The aim of the second pot experiment was to establish the effect of increasing levels of phosphorus fertilizing at a background of 400 mg N and 200 mg K2O per kg soil on the barley grain and protein yields. The plants were grown in plastic pots (5L volume). Each pot was contained 5 kg soil (Molic fluvisol) with pH (H2O) - 7.3, humus content 3.2%, Nmin - 39.8 mg N/kg, available phosphorus (method of Egner - Riehm) - 102 mg P2O5/kg, and available potassium (2 N HCL) - 460 mg K2O/kg. The different levels of mineral nutrition at two pot experiments were created by applying of NH4NO3, Ca(H2PO4)2.H2O, and K2SO4 in the form of water solutions. Thirty seeds were sown in each pot ant the plants were reduced to equal number in each pot (15) at tillering. Phosphorus and potassium fertilizing were a proved positive effect on the nutrient regime of barley plants, productivity and grain quality. Moderate phosphorus fertilizing 200 mg P2O5.kg-1 soil combined with levels N400K200 showed the highest grain and protein yields and grain protein concentrations. Grain protein concentration increased from 12.5 to 13.5% and protein yield increased by 28.6%, compared to variant without phosphorus N400P0K200. The K levels of 200 and 400 mg K2O.kg-1 soil increased the grain yield when were combined with nitrogen levels of 200 - 400 N mg/kg soil. The changes of potassium nutrient regime by fertilizing alone in a range K0 - K400 on the background of N0P200, slightly affect the grain protein concentrations and yields of barley. The potassium fertilization demonstrated a positive effect on the concentrations of plant nitrogen at tillering. The concentrations of N and P of barley plants at tillering stage slightly depended on fertilizing levels P0-P400