Stover forage quality and stalk strength relationships in corn, Zea mays L.
The study was conducted with the purpose of helping to clarify the poorly understood relationship between stover forage quality and stalk strength and plant traits associated with stalk strength of corn (Zea mays L.);Seven hybrids with a wide range of stalk strength (male-sterile with ears covered, normal counterpart, male-sterile with ears, prolific hybrid, and the zero, first, and third cycles of selection for stalk strength from a synthetic variety) were grown at two locations, Ames and Nashua, Iowa, 1983. They were planted at three population densities (about 32,000, 64,000, 96,000 plants ha('-1)), and harvested at mid-silking and at physiological maturity. The experimental design was a split-split plot with three replications;The variables measured were crushing strength; rind thickness; sugar concentration of the sap; stalk moisture for the first harvest; and length, diameter, and volume of the second elongated intermode from the bottom. Also, concentration of acid detergent fiber (ADF) and acid detergent lignin (ADL) of the whole internode, rind, and pith, and in vitro dry matter disappearance (IVDMD) of different plant parts of the corn plant (whole internode, rind, pith, and stover). Stover dry matter yield and grain yield were also determined;The results showed that stalk strength seems to be a complex phenomenon. Rind thickness, which implies a strength factor, was by far the trait most closely associated with crushing strength. Sugar concentration, which implies a healthier stalk with more resistance to pests, and a possible strength aspect of higher turgor potential, was greatest in the strongest stalk hybrids. Stalk diameter might have accounted for the decrease in stalk strength from increasing population densities. Forage quality (ADF, ADL, and IVDMD) of the whole internode, rind, pith, and stover was not adversely affected by stalk strength. Stover yield was greatest in the male sterile with ears covered and was least in the prolific. There was no clear sacrifice in grain yield by increasing stalk strength, and male sterility was responsible for the greatest yields under stress conditions. The prolific hybrid also showed relatively high yields.