Changes in Soil Phosphorus Pools and Chemical Properties under Liming in Nitisols of Farawocha, South Ethiopia

Abstract

Understanding the nutrient dynamics in acid soil is fundamental to carry out proper management. The study was conducted to investigate phosphorus (P) pools and selected properties under different rates of lime for acid nitisols of Farawocha, Southern Ethiopia. Four lime rates incubated for a month in three replications were tested. The lime rates were 0 t/ha (0%), 5.25 t/ha (50%), 10.5 t/ha (100%), and 15.75 t/ha (150%). Lime requirement (LR) for 100% was calculated targeting soil pH of 6.5. Data on the P pools such as soluble P (P-sol) and bounded forms of P with iron (Fe-P), aluminum (Al-P), calcium (Ca-P), organic part (Org-P), residual P (Res-P), and total of P fractions were measured. In addition, changes in soil chemical properties such as pH, exchangeable acidity, calcium (Ca), magnesium (Mg), sulfur (S), iron (Fe), copper (Cu), boron (B), zinc (Zn), and manganese (Mn) were analyzed. The result showed that total P was 357.5 mg/kg. Compared to nontreated soil, liming at a rate of 15.75 t/ha significantly improved P-sol (34.2%, r2 = 0.88), Ca-P (61.6%, r2 = 0.92), and Res-P (195%, r2 = 0.94); however, it reduced Fe-P (58.5%, r2 = −0.83), Al-P (71%, r2 = −0.97), and Org-P (19.1%, r2 = 0.93). Overall, the P-associated fractions in the soil, regardless of the lime rates, were in the order of Org_P > Res_P > Fe_P > Ca_P > Al_P > P-sol. Liming raised soil pH by 2.1 units (4.5 to 6.6) over nonlimed soil, whereas it reduced exchangeable acidity from 4.18 to 0.23 meq/100 g soil. Available P, Ca, Mg, S, Cu, Zn, and B contents were significantly improved with lime application. However, liming reduced Fe and Mn contents. In conclusion, these findings showed that liming facilitated the release of P from various pools, modified pH and exchangeable acidity, and resulted in beneficial changes for most of the soil chemical properties.

Phosphorus Fractions Evaluation in the Soils of the Southern Guinea Savannah of Nigeria

“…Aluminium bound P is more readily available than other P forms and its uptake of Al-P may also be attributed to the low amount observed in these soils in comparison to the Fe-P 12 . Precipitation reactions involving the replacement of Al by Ca on exchange sites as well as the fixation of phosphorus by calcium could be could occur have led to the high amount of Ca-P observed in both soils 8 . The amount of Residual P fraction made up of insoluble and stable forms of P, such as Ca-, Fe-and Al-bounded P representing the unavailable forms of P pools in the soil was high in both locations.…”

“…The amount of Residual P fraction made up of insoluble and stable forms of P, such as Ca-, Fe-and Al-bounded P representing the unavailable forms of P pools in the soil was high in both locations. The high amount may be as a result of complexation and reaction of both organic and inorganic released P with the clay surface either by ligand exchange and or surface complexation 5,8 .…”