Studying the Direct and Residual Effect of Long‐Term Fertilization Using Ammonium Lactate and Hot Water Extraction Methods

Abstract

In the last decade, there was a strong decline in the fertilizer consumption in Hungary. The low fertilizer use has led to negative nutrient balances. The objective of this work was to study the direct and residual effect of P and K fertilization on soil P and K content after many years of intensive fertilization, using ammonium‐lactate (AL) extraction and hot water percolation (HWP) methods, and to investigate grain yield response of winter wheat to nutrients. Long‐term P and K fertilization experiments were set up on a chromic cambisol at Keszthely (Hungary) in 1963. The treatments included increasing P and K rates. The trials were done on plots of 96 m2 in six replications. After 10 yr, the plots were split, and the number of replications was reduced to three. From 1974 on, one part of the plots no longer received P and K fertilizer, whereas the other part of the plots was fertilized with increasing P and K rates. Investigations were performed in 2000 and included 20 different fertilization treatments. After 27 yr, no residual effect of long‐term intensive P and K fertilization on soil P and K or grain P and K contents could be detected even in the highest P and K rate plots (1968 kg P2O5 and 2160 kg K2O ha−1 10 yr−1, respectively). There were statistically validated linear correlations between HWP and AL methods in the soil P and K contents (r=0.83 and 0.82, respectively). However, regression analysis revealed closer correlation between AL‐extractable soil and plant P contents than with soil HWP and plant P contents. Under the given site conditions, a regular P supply is of greater importance than K fertilization, and up to a soil AL‐P2O5 level of 100 mg kg−1, yearly P fertilization can not be neglected.