High-analysis fertilizers do affect respective macronutrient concentration in topsoil after wheat harvest while deeper exploration revealed their significant amount

Post-fertilization changes in soil macronutrients were explored in three locations on intensively cultivated soils in Ethiopia. Fifteen soil samples before planting and 30 after wheat harvest were collected from middle blocks at five-depth intervals, 120 cm deep pits. After harvest, samples were collected only from control, and full-dose Nitrogen-Phosphorus-Sulfur-Calcium (69:20:18:23 kg/ha, respectively) treated units. Results showed a substantial pool of (macronutrient contents of up to 30%) remaining in topsoil after wheat harvest. However, N and S which were already low in the initial topsoil went to severely deficient levels after harvest. But the available-P varied dramatically possibly due to previous applications in narrow-bands/small-spots. Calcium became excess in already Ca-rich calcareous soils. Profile-wise, soil-pH, SO42-, CEC, and Ca2+ increased with depth, while soil-OC, total-N, and P followed reverse trends. Major contributors to such spatiotemporal dynamics in soil properties were conceived to be the rates of biomass recycling, clay mineralogy, soil texture, and pedogenic processes like leaching. The correlation matrix also showed wide variations among soil properties. Such soil variability reflects the history of fertilizer-use/cropping systems, and also the differences in soil profile characteristics. The insights gained from this study indicate the significance of nutrients remaining after productive crops in future soil fertility planning. However, additional crop/soil-specific nutrient-balance model experiments detailing the respective macronutrients at the farm, etc., levels can be installed. This will allow us to make site-specific-cost-effective fertilizer recommendations.  Key words: Post-fertilization, soil profile, residual-nutrients, leaching-loss, nutrient-balance.