Relationship between the phosphorus balance of Hungarian long‐term field trials, trend of yields, and soluble phosphorus content of the soils

Abstract

The long‐term changes in the first 20 years of the Hungarian National Long‐Term Fertilization Trials were studied. Eleven treatments were selected for the study: unfertilized control, a large dose of fertilizers [250–66–80 kg/ha of nitrogen (N), phosphrous (P), and potassium (K), respectively], and all combinations of 50–100–150 kg/ha N and 0–22–44 kg/ha P with 80 kg K/ha. Three experiments, started in 1967, 1968, and 1969, consecutively, were included in the analysis with same crop rotations of wheat‐maize‐maize‐wheat. Positive linear trends in yields were seen over the course of the experiment, even on the unfertilized plots. Nitrogen and P fertilization had strong influences on the slopes of trends. Ammonium lactate‐soluble P content in the soil plough layer also increased if P fertilizer was applied. Linear trends of nutrient content on yield were also seen in some treatments: positive for N and both negative and positive for the P. Nitrogen uptake increased in every treatment even in the unfertilized one. Phosphorus uptake increased at the higher P supply (44 kg P/ha). Phosphorus input was approximately equal to output at the 22 kg P/ha level, although the soluble soil P content increased at aproximately 10% of the fertilizer input.