Influence of irrigation and supply of available nitrogen on growth and nutrient content of spring wheat

In the dry summer 1969 the effect of irrigation and supply of available nitrogen on the production of dry matter and on the N, P, K, Mg, and Ca content of the aerial parts of spring wheat was studied on the basis of samples collected at various stages of development from a field trial. Shoots collected from the irrigated plots (30 mm water on June 9 and 30 mm water on June 17) in the middle and at the end of June had a higher content of all the nutrients studied than those from the nonirrigated plots although at the latter date also the dry matter yield was markedly increased by irrigation. Later, the larger production of dry matter on the irrigated plots decreased this difference and resulted in equal or even somewhat lower contens of N, P, K, Mg, and Ca in the ears and straw, and also in the grains. An improvement in the supply of available nitrogen tended to increase the dry matter yield and the content of K, Mg, and Ca in the vegetative parts of the plant; the N content was increased also in the ears and grains. The positive interaction of water and nitrogen supply was distinct in the production of dry matter and in the uptake of nutrients. The high grain yields produced by irrigation and good or very good nitrogen supply were attributed, at least partly, to the more intensive uptake of nutrients during the period of vigorous growth in June. It was emphasized that the improvement of the efficiency of plant production by irrigation and placement of fertilizers may result in an impoverishment of the soil of other nutrients.