The effect of various sources and dose of phosphorus on residual soil test phosphorus in different soils

Soil test phosphorus (STP) finds its agronomic utility for the recommendation of phosphorus (P) fertilizer to crops and in risk assessment of offsite soil P movement from an environmental perspective. The objective of this research was to understand the influence of P from several P sources applied at 0, 50 and 150 mg P kg− 1 on STP in six different soils both before crop P removal (NBP0) and after the first (NBP1) and seventh harvest (NBP7) of corn (Zea mays L.). The P was extracted with Bray1 solution from animal P sources alone as well as from soils amended with P sources. The various net Bray1 (NBP) levels were computed by subtracting Bray1 levels in the control treatments from the P amended treatments. The results suggested that monogastric P sources contained relatively large proportions of Bray1 than ruminants. However, when gross Bray1 levels were expressed as percent of total P, the hog (Sus scrofa) manure (HM) and cattle (Bos taurus) manure 2 (CM2) had identical proportions while sewage sludge (SS) and turkey (Meleagris gallopava) litter (TL) had the least amount of Bray1 extractable P. Both cattle manures and HM resulted in significant higher concentration of NBP0 and NBP1 in most soils among the animal P sources. All P sources in the Eram–Lebo soil and all soils amended with TL at both levels of P application had the least amounts of NBP0 and NBP1. The greatest proportion of total residual P was detected as Bray1 in HM and the least in TL. These findings will be helpful for land managers with high soil test P levels who are under P regulation to help discern how various P sources affect soil Bray 1P.