The effects of phosphorus fertilizers and organic materials under different soil ph on phosphorus adsorption, changes in some micronutrients and biological properties of soils

This study aimed to determine the effects of phosphorus fertilizers (TSP and ground crude rock phosphate (GRP)) in combination with various organic materials (biochar, vermicompost, farmyard manure) on phosphorus adsorption capacity, micronutrient availability and biological properties in soils with different pH. This research was conducted at Tokat Gaziosmanpaşa University, Faculty of Agriculture, using two phosphorus fertilizers and three organic material combinations in three different soil types with acidic, neutral and basic properties, and supported by both incubation and pot trials. The findings of the study show that the application of phosphorus fertilizers in combination with organic materials significantly increases the amount of both total and inorganic phosphorus in the soil. In particular, farmyard manure and vermicompost applications promoted microbial activity and enzymatic processes, thereby significantly increasing the availability of phosphorus. In addition, these organic materials increased soil fertility by increasing soil organic matter and especially inorganic nitrogen levels. The effect of pH on phosphorus uptake was significant; in acidic soils, the combination of ground rock phosphate and farmyard manure increased pH and facilitated phosphorus uptake, while in basic soils, biochar further increased pH and in some cases caused fixation of phosphorus. According to the research findings, phosphorus adsorption capacity in acid, neutral and basic reaction soils revealed that phosphorus adsorption in all soil types increased rapidly from the 1st hour and reached the maximum level on the 3rd day, then this increase slowed down on the 5th and 7th days. It was observed that the treatments also had significant effects on microelements and especially GRP+Vermicompost and GRP+Farm treatments increased the availability of Zn, Fe, Mn and Cu in the soil by increasing their available forms. In addition, microbial biomass (MBC), dehydrogenase (DHA) and phosphotase enzyme activities of soils increased significantly due to the use of applied phosphorus fertilizers together with organic materials. Especially, GRP+Farm and GRP+Vermicompost treatments reached the highest values in MBC and enzyme activities in all soil reactions. In conclusion, in terms of improving soil health and increasing the efficiency of phosphorus utilization, applications of phosphorus fertilizers with organic materials provide important advantages in terms of sustainability in agriculture. These combinations, considering soil pH, phosphorus form and organic material type, increase the availability of phosphorus to plants, support the mobility of micronutrients and positively affect soil biological properties. In this respect, the study sheds light on new strategies for phosphorus fertilization and the contribution of organic materials.