Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.
Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.
THE EFFECTS OF DEFOLIATION AND STAND REDUCTION ON THE GROWTH AND YIELD OF CORN (ZEA MAYS L.)
Abstract
Hail damage to corn is largely characterized by stripped and shredded leaves. Defoliation and occasional reduction in plant density also result from hail damage. Two experiments were conducted at the University of Nebraska Field Laboratory near Mead, Nebraska during the 1979 and 1980 growing seasons. These studies were conducted to investigate the effects of defoliation and reduction in plant density on the growth and yield of corn. Both the defoliation and stand reduction experiments were layed out in randomized complete-block design, with seven replications for each study. Normal leaf type NC + 85 hybrid corn was planted at the rate of 69,160 kernels/ha. on May 11, 1979, and May 7, 1980 for the defoliation study. Upright leaf type, single cross hybrid corn, NC + 59 was planted on May 11 and May 8 in 1979 and 1980, respectively, at the rate of 74,100 kernels/ha. for the stand reduction study. The stand reduction experiment was later thinned to 69,160, 59,280, 49,400, 39,520, and 29,640 plants/ha. The 69,160 plants/ha. was used as the control. Both hybrids used in the experiments are full-season hybrids with a 120-day maturity rating. Reduction in plant density was at the 6, 9, 12, and 15 leaf stages. The defoliation study consisted of cutting off the corn plants at 2.5 cm. above the growing point at the 4 through the 9 leaf stages, while reduction in plant density involved completely removing randomly selected corn plants until desired population density was attained. The characters studied included plant height, leaf area and leaf area index, ear height, stem diameter, dry matter, shelling percentage and grain yield. Defoliation treatments resulted in a linear decrease in plant height and ear height. Leaf area and leaf area index were significantly reduced by defoliation. Stem diameter linearly declined with defoliation at successive leaf stages. All defoliation treatments reduced dry matter from that of the control. Grain yields were increased by defoliation at the 5 leaf stage. Even though there was an increase in grain yield by defoliating corn plants at the 5 leaf stage, this increase over the control was only 1%. Apart from this increase, all other defoliation treatments significantly reduced yields. Reducing corn plant density from 59,280 plants/ha. to 29,640 plants/ha. reduced grain yield. For the single cross hybrid, NC + 59 used in the experiment, data obtained suggest that a population density of 49,400 plants/ha. to 59,280 plants/ha. is the most stable for grain production.
Subject Area
Agronomy
Recommended Citation
MBANASO, A. BENJAMIN CHIJIOKE, "THE EFFECTS OF DEFOLIATION AND STAND REDUCTION ON THE GROWTH AND YIELD OF CORN (ZEA MAYS L.)" (1981). ETD collection for University of Nebraska-Lincoln. AAI8118174.
https://digitalcommons.unl.edu/dissertations/AAI8118174