Reclamation of calcareous saline sodic soil with different amendments (II): Impact on nitrogen, phosphorous and potassium redistribution and on microbial respiration

Macronutrients deficiency is one of the most important limitations of saline sodic soils. This study is focused on redistribution of nitrogen (N), phosphorous (P) and potassium (K) as well as microbial respiration in ameliorating process of a calcareous saline sodic soil. The experimental work was performed with five soil treatments: cattle manure, pistachio residue, gypsum, manure + gypsum and pistachio residue + gypsum, plus the control. One water treatment (with sulfuric acid) plus the control and three replications were applied. After one month of incubation, four intermittent irrigation events with a monthly frequency were applied. The results indicated that concentrations of N and K increased with soil depth while, the highest P concentration was observed in surface soil. The organic matter-amended soils showed the highest concentrations of N. It was found that P availability increased due to the application of amendments except for gypsum which showed an antagonism influence. Application of organic matters increased the absorbable K, but part of its concentration came from their chemical composition. Compared to the untreated water, sulfuric acid had positive impacts on P and K availability, however its influence on N concentration was negligible. Measurement of microbial respiration showed that cattle manure had the highest rates of carbon mineralization. The application of gypsum as well as sulfuric acid had no significant effects on microbial respiration. Results showed that pistachio residue is an efficient amendment to reclaim saline sodic soils, and to improve availability of macronutrients.