Effect of P, Zn and Cu Fertilization on Crops on a Calcareous Chernozem Soil

Both deficiency and excess of P, Zn and Cu are common in soils and crops of Hungary. The excess and deficiency of P occurring in agricultural soils and crops is a consequence of previous fertilization practice. Zn deficiency occurs mainly on calcareous soils well fertilized with P under maize, while Cu deficiency is often detected on poor sandy soils and on organic soils under other crops. Zn and Cu excess has been measured in city soils, in soils near highways and industrial areas. In the present paper the effect of P supply is shown on yield and P/Zn ratios of crops, presenting the phenomena of the P-induced Zn deficiency on a calcareous loamy chernozem soil. In an other long-term field trial on the same soil, the effect of Cu and Zn loads was studied on soil and crop. The main conclusions drawn from these long-term field experiments are as follows: 1. An excess of available P in the plough layer of this soil might be detected by the ammonium lactate (AL) method when the soil analysis shows concentrations higher than 150-200 mg/kg P ₂ O ₅ . The P/Zn ratios of 6-leaf stage shoots and harvested straw of maize grown on these plots might be higher than 200, while that of grain 150-200. 2. In the frame of a fertilization program, P-induced Zn deficiency can be counterbalanced effectively on such calcareous chernozem soils with the application of P and Zn fertilizers in a ratio around 10:1. 3. The Cu content of crops could not be markedly raised by using CuSO ₄ fertilizer, even with rates as high as 270 or 810 kg/ha Cu. However, as an effect of increased NxP fertilization, the Cu content of maize grain doubled, or that of maize straw was 4-times higher. This is an important tool for the Cu enrichment of animal diet, when maize straw is also used for animal feeding. 4. The soil and plant analysis data are proper means of controlling soil fertility and crop nutritional status when the soil and plant data are previously calibrated in long-term field experiments.