Studies were carried out in the greenhouse and field to elaborate the mechanism of P‐Zn interaction in the nutrition of corn (Zea mays L.). From this work depressive action of P on Zn uptake of corn appears to be largely physiological in nature, expressed at root surfaces and/or in root cells, and is not chemical inactivation of Zn by P in soil. Translocation of Zn from roots to tops is inhibited by elevated P concentration, with resulting sharp reduction in Zn concentration of nodal and internodal tissues. No clearly definable P/Zn ratio in tissue was found above which yield restriction could be predicted. Corn seems to tolerate high concentrations of P in its tissues provided some modest quantity of Zn is present. Other elements counteract somewhat the damaging effects of P. Concurrently placed N promotes Zn uptake at the same time that it benefits P utilization. Increased level of native or applied K reduces the depressive effects of P on Zn.

Synopsis Water use efficiency of grain crops in Nebraska was increased an average 29% by optimum fertilizer treatment. This enhancement was especially associated with yield increase, and was accompanied by an approximate extra inch of water consumption by the crop. Corn and sorghum evidenced a greater capability for extracting deep subsoil moisture than small grains.

Greenhouse experiments were used to study soil compaction, moisture level, soluble P and Zn, pH, organic matter and clay contents, K saturation and titratable alkalinity as these soil factors influenced P‐Zn relationships in corn. Some of the resulting observations help to explain why starter fertilizers containing P may on occasions cause depressions in plant growth. Fertilizer P applied in the row markedly reduced Zn concentration of corn. Increasing soil compaction and soil moisture level caused further depressions of Zn concentration. The combination of irrigation practice on newly graded (and compacted) land, especially when soil P is high, would seem to portend Zn deficiency problems. Soil K saturation also appears to have a decided influence on P‐Zn relations in the plant. The higher the percent K saturation of the soil, the less did applied P reduce plant utilization of Zn in these experiments.