Effect of Source and Rate of Potassium Fertilizer on Plant Growth Under Soil Water Stress

Abstract

Two pot experiments were conducted to study the effects of soil water stress, and rate and type of K-fertilizer on some growth and physiological traits of two Maize (Zea mays L.) hybrids S.C.10 and T.W.C310. Three soil water regimes (100, 75 and 50% of soil field capacity), Three K application rates (0, 50, 100 kg K/fed.) and four types of K sources (KCl, K2SO4, KNO3 and a 1:1:1 mixture of them) were applied as the treatments of a split- split experimental design for each hybrid. The total chlorophyll a and b, fresh and dry weight were measured as growth parameters and leaf area ratio, net assimilation and relative growth rates were measured as physiological parameters. The obtained data indicated significant effects for moisture stress on fresh and dry weight of both S.C.10 and T.W.C.310 maize plants in the three growth stage and total chlorophyll content only in the third growth stage for both Maize hybrids. Potassium fertilization level effects were significant on the three characters in second and third growth stages in S.C.10 and in the first and second growth stages for fresh and dry weight besides the three growth stages for total chlorophyll content in T.W.C.310. However, potassium fertilizer source effects were significant on total chlorophyll content in the third growth stage, only for both maize hybrids. Potassium source had significant effect on fresh and dry weight in the three growth stages in

S.C.10 and the first and second growth stages in T.W.C.310. Generally, non-water stressed treatment (100% of field capacity), the highest potassium level (45 kg/fed.) and potassium nitrate or sulphate produced the highest values of the tested traits. Increasing K application rate was found to relief the adverse effect of soil moisture stress on the two tested maize hybrids. Also, selection of suitable K source has a beneficial effect for better plant growth. Potassium nitrate produced the highest values of the most studied growth characters.