Influence of soil fertility management technologies on phosphorus fractions, sorption characteristics, and use efficiency in humic Nitisols of Upper Eastern Kenya.

Fractions of phosphorus (P) and its sorption characteristics are affected by different soil fertility (FM) technologies which ultimately affect crop growth and productivity. However, the response of P fractions and sorption characteristics to soil fertility technologies that integrate diverse amendments is still poorly understood in acidic Nitisols. A randomized complete block design was layout in an acidic Nitisol to determine fractions of P, its sorption characteristics and use efficiencies in acidic Nitisols under various FM technologies in field conditions. The use of minimum tillage + maize residue + inorganic fertilizer + goat manure (MTCrGF) had the highest impact on and significantly increased resin-Pi, NaHCO-Pi, and maximum P sorption (S) by 182, 76, and 52 mg P kg. Moreover, NaOH-Pi and S concentrations were higher under conventional tillage + maize residue + inorganic fertilizer + goat manure (CTCrGF) by 216 mg P kg and 49 mg P kg than the control. MTCrGF and CTCrGF also had the lowest P bonding energy (0.04 L mg). CTCrGF had the highest P partial productivity factor (0.093 and 0.140 kg biomass kg P) and P agronomic efficiency (0.080 and 0.073 kg biomass kg P) during the two cropping seasons. The results demonstrate the positive influence of combining multiple P sources on soil P fractions, sorption characteristics, and use efficiencies. Notably, combining either conventional or minimum tillage with maize straw and applying integrated manure and inorganic fertilizer (MTCrGF or CTCrGF) can increase the labile P concentrations and reduce the potential depletion of the non-renewable rock phosphate and the use of inorganic phosphatic fertilizers for agricultural production.