G. K. Judel

Yield response and availability of various phosphate fertilizer types as estimated by EUF

SummaryThe solubility of various phosphate fertilizers (Superphosphate, Rhenania phosphate, Novaphos, Carolon phosphate and Hyperphosphate) was studied in an incubation experiment, and the uptake of P from these fertilizers and their effects on wheat yields were investigated in a pot experiment. The soil used was a carbonate-free, brown podsolic soil (C horizon) with a neutral pH and low in available phosphate and humus.The quantities of P extracted from the soil by the EUF technique decreased with an increase of the unacidulated portion of the P fertilizer. This clear differentiation in the solubility of the various P fertilizers was not obtained with a DL extraction. Uptake of P by plants was highly correlated with quantity of P extracted by EUF (r=0.95***), while the correlation between P uptake and P extracted by DL was less narrow (r=0.64*). Yield, particularly grain yield, decreased with increasing portion of unacidulated P in the fertilizers tested. Grain yield and EUF-extractable P were highly correlated (r=0.86***), whereas the relationship between grain yield and DL-extractable P was poorer (r=0.62*). The experiments showed that mainly the easily soluble phosphate is of importance for the P nutrition of crops.