POTENTIAL USE OF STALK pH AND STALK PERCENT DRY MATTER AS ESTIMATORS OF LODGING SUSCEPTIBILITY IN CORN

Fourteen corn (Zea mays L.) hybrids were grown at three locations in 1973 and one location in 1975 to study relationships between stalk pH, percent stalk dry matter (SDM), and percent broken stalks (PBS). The three traits were measured at weekly intervals for 4 or 5 wk encompassing grain physiological maturity in the tests of 1973, and on one date, near maturity, in 1975. Measurements of stalk crushing strength, rind thickness, and dry weight of 5-cm stalk sections were also obtained in 1975. In addition, records of PBS were available for the 14 hybrids from 12 tests grown over 4 yr prior to 1973. All measurements of PBS were transformed as log10 (x + 1) prior to statistical analysis; measurements of PBS, pH and SDM were adjusted by covariance to a common percent grain moisture. Measurements of stalk pH were not consistently related across the 14 hybrids to long-term measurements of PBS. Linear correlation coefficients between SDM and PBS were more consistent (i.e., usually positive) but were generally not statistically significant. Measurements of crushing strength, rind thickness and dry weight of 5-cm stalk sections for the 14 hybrids were not correlated with the 12-test means of PBS. In fact, none of the analytical measurements were as useful as measurements of PBS per se, recorded for individual tests in 1973 and 1975, in predicting hybrid differences in PBS as measured in the 12 tests prior to 1973.Key words: Corn, lodging, stalk pH, stalk dry matter