Relationships Between Dry Matter Yields and Concentrations of Zn and P in Young Corn Plants¹

Yield‐Zn or P concentration relationships were studied in corn ( Zea mays L.) grown in several greenhouse pot experiments conducted to compare various rates and sources of Zn and P on soils deficient in these nutrients, Such relationships are important in proper interpretation of plant analysis results. The usual result was for corn forage yields to increase at a minimum Zn concentration of 7 to 9 ppm in the dry forage until P or other growth factor became limiting. Then yields leveled off and Zn concentrations increased at sufficiently high levels of applied Zn. Similarly, yields increased at a minimum P concentration near 0.10% until Zn or other growth factor became limiting; P concentrations then increased. Critical concentrations in the dry corn forage were estimated to be about 14 ppm of Zn and 0.14% P.