Synopsis Nitrate‐nitrogen content of cotton petioles was found to be related to the rate of nitrogen applied and the total yield. Yield reductions were related to the length of time petiole nitrate‐nitrogen fell below minimum levels of 1000 and 2000 parts per million.

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Interactions of Zn and P in tops and roots of corn were studied in Corning and Landlow soils and of tomato in Corning soil in greenhouse. Zn deficiency symptoms were seen in both crops. The Zn concentration in tops was reduced due to P application and the magnitude of reduction was greatest for the first increment of added P (25 ppm). The Zn concentration in roots was much less influenced by added P. The P concentration was reduced by first rate of 1 ppm Zn and the effect was primarily with higher rates of P. Added P increased P concentration in the top much more than in the roots. In the presence of P, added zinc increased the zinc concentration in corn roots more than in corn tops.

The effects of source and placement of zinc and phosphorus were studied in several greenhouse experiments. A Zn and P deficient soil was utilized and sweet corn was grown as the test plant. When Zn fertilizer materials were mixed well with the soil ZnSO4 and organic sources such as ZnEDTA and Rayplex‐Zn were equivalent in their effectiveness for the correction of Zn deficiency. However, if the fertilizer was banded under the seed, ZnEDTA was more effective than the inorganic sources. A small amount of mixing appeared to improve the effectiveness of Zn, or P, or both fertilizers markedly. Granulation greatly reduced the effectiveness of ZnSO4, ZnNH4PO4, and Rayplex‐Zn.

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