Mineral nutrition of wheat (Triticum aestivum L.) on calcareous chernozem soil. II.

In a fertilisation experiment set up in autumn 1973 on calcareous loamy che rnozem soil, studies were made on the effect of different N, P and K supply levels and their combinations on the development, powdery mildew infection , protein and amino acid contents of wheat, and on major soil properties, T he agrochemical parameters of the ploughed layer of the soil were as follow s: CaCO3 5%, humus 3%, PH(KCl) 7.3, AL-P2O5 60-80 ppm, AL-K2O 140-160 ppm, KCl-soluble Mg 150-180 ppm, KCl+EDTA Mn 100-150 ppm, Cu 3 ppm, Zn 2 ppm. Th e factorial experiment represented 4N x 4P x 4K = 64 treatments in 2 replic ations, giving a total of 128 plots. The mineral fertiliser was applied in the form of 25% calcium ammonium nitrate, 18% super-phosphate and 50% potas sium chloride. The main results can be summarised as follows: The degree of infection of wheat with powdery mildew rose from 24% to 56% w hen N was over-supplied. As the P and K supplies improved, the degree of in fection dropped by 10 and 14%, respectively. Balanced nutrition led to an i mprovement in powdery mildew resistance and better yields. Measurements show that at the tillering stage the toxic chloride limit tole rated by wheat is indicated by a Cl- content of around 0.2% in the shoots. As the result of N x P interactions the 4 t/ha grain yield obtained in the control rose by 35-40% and the protein yield per hectare by 60-65%. Little change was observed in the amino acids, which are largely geneticall y determined. Maximum yield and quality (protein and amino acid content or yield) were achieved as a function of balanced N x P supplies. The AL-solub le P2O5 content of the soil, however, should not be increased to more than 150-200 mg/kg to improve either the quantity or quality of the yield. After the wet first year the NO3-N in the N-3 treatment was leached to a de pth of 60 cm. According to analyses of the 1:5 aqueous extract, the leachin g of the Cl- ions introduced with the potassium fertiliser could be observe d even at a depth of 1 m, with concentrations an order of magnitude greater than normal in the 40-80 cm layer. The K+ and Na+, and the SO42- and Ca2from the P treatments remained in the upper 0-40 cm soil layer. The "total salt" gave a good indication of the movement of electrolytes in the soil pr ofile.