The Residual Effects of P and K-fertilizers on the Yield of Wheat in Rotation with Maize

This study was conducted to determine the residual effects of P and K fertilizers applied to maize on the yield of wheat in rotation with maize during 1999-2002 at Safi-abad Agicultural Research Center, Dezful. The experimental design was a randomized complete block with three replications and a comparative plot for comparing the effects of fresh P and K fertilization with the residual effects of P and K in each replication. The treatments were four P fertilizer levels(0, 60, 120 and 180 kg/ha P₂O₅ as TSP) and four K fertilizer levels(0, 100 , 200 and 300 kg/ha K₂O as SOP) , which were applied prior to maize planting. The results showed that the residual effect of P on the grain yield and the thousand kernel weight was significant at 1% level, while K residual effect on the grain yield was significant at 5% level. Also,whenever more fertilizer was applied in previous planting, the residual effects of P and K on the grain yield and the thousand kernel wieght increased. Also,the residual effect for each fertilizer level on the grain yield and the thousand kernel weight was greater than control plot which received no P and K before cultivation. The grain yield (4.60 tons/ha) resulting from the fresh P and K fertilizer in comparative plots was nearly equal to the grain yield (4.91 ton/ha) obtained with the residual effect of the highest P and K fertilizer levels (180 and 300 kg/ha P₂O₅ and K₂O). The differwnce between the grain yield of fresh fertilization (100 and 150 kg/ha TSP and SOP, respectively) and the control plots was more than 1 ton/ha (4.6 vs 3.53 ton/ha). Therefore, application of P and K fertilizers in maize can provide some of the nutritional requirments of the next crop(wheat). This finding emphasizes the importance of soil testing rather than the application of a general fertilizer recommendations in wheat-corn rotations