Soil potassium and the growth of vegetable seedlings. II.—Effect of potassium and ammonium salts on the growth and composition of seedlings

Abstract

AbstractThe effects of applications of potassium nitrate, potassium sulphate with ammonium nitrate, and farmyard manure (FYM) with ammonium nitrate on the growth and mineral composition of seedlings of lettuce, cabbage, onion and carrot were measured. The main purpose of the experiment was to find whether the sulphate in potassium sulphate supplying 400 lb. of K per acre damaged seedling growth; the results show that it did not.The FYM applications increased the cation‐exchange capacity of the soil (by 27%) and the amount of exchangeable potassium in the soil but had little effect on the exchangeable calcium and magnesium contents. The effects of these changes and of the added fertilisers on the availability of soil potassium and on the concentrations of the major cations in an ‘equilibrium soil extract’ are considered.Seedlings grown in soil with a given Na+/K+ ratio in the ‘equilibrium soil extract’ took up much less Na+ than seedlings grown in sand culture where the Na+/K+ ratio in the nutrient solution was the same as that in the ‘equilibrium soil extract’.