Effects of soil water conditions, sewage sludge and chemical fertilizers on concentrations of rice macronutrients in an alkaline soil

The aim of this research was the study of the effects of soil water conditions, sewage sludge and chemical fertilizers on concentrations of macronutrients and sodium in shoot and root of rice plant (Oryza sativa L. cv. Ali Kazemi) in a loamy sand non-calcareous alkaline soil. The study was performed as a factorial experiment in a randomized complete blocks design including soil water conditions at three levels (continuous submergence, alternate submergence and alternate saturation) and source and amount of organic and chemical fertilizers at 10 levels (control, 100% chemical fertilizers, 20 g sewage sludge/kg of soil with and without 50% chemical fertilizers, 40 g sewage sludge/kg of soil with and without 50% chemical fertilizers, 20 g poultry manure/kg of soil with and without 50% chemical fertilizers and 40 g poultry manure/kg of soil with and without 50% chemical fertilizers) with three replications. The results showed that the effects of soil water conditions and fertilizers on concentrations of macronutrients in shoot and root of rice were significant. Application of 20 and 40 g poultry manure per kg of soil prevented the growth of rice; therefore, these treatments were excluded. The application of 20 and 40 g sewage sludge per kg of soil increased significantly all of macronutrient concentrations except shoot concentration of N and Na and root concentration of K compared to the control and 100% chemical fertilizers. Addition of 50% chemical fertilizers to 20 g sewage sludge per kg of soil increased shoot and root concentrations of P compared to application of only 20 g sewage sludge per kg of soil. Alternate submergence increased shoot and root concentrations of P, K, Ca, Mg and Na (except root concentration of K) compared with continuous submergence and alternate saturation. The concentrations of P, K and Mg in rice shoot were greater than root, while the concentrations of Na and Ca in rice root were greater than shoot.