2023 Volume 92 Issue 2 Pages 110-118
We investigated the effects of 4 rates of phosphorus (P) fertilizer application on growth, grain yield and arbuscular mycorrhizal (AM) infection rate of groundnut (Arachis hypogaea L.) grown in acrisols, in which P binds to iron, in Okinawa. Over 4 years, plants were grown with no addition of P (P0), half the standard rate of P (P0.5), the standard rate (P1), and double the rate (P2) using superphosphate. In year 1, there was no significant difference in growth and grain yield between P0 and P2. By the end of year 4, the growth and grain yields of P0 and P0.5 were significantly reduced, but those of P2 were similar to those of P1. We found a significant logarithmic regression relationship between the grain weight and the amount of P uptake of the grain. Grain P uptakes was in a logarithmic regression relationship with several kinds of P contents in soil. The results suggest that groundnut cultivation in acrisols must be 9 g/m2 of P fertilization (superphosphate). The AM infection rate of roots did not decrease in P0.5, P1 and P2, even when the P fertility was high, which implied that AM infection strongly affected groundnut growth.
