Submitted to: Maydica
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/27/2002
Publication Date: 3/15/2003
Citation: BRUNS, H.A., ABBAS, H.K. 2003. EFFECTS OF PLANT POPULATIONS ON MAIZE HYBRIDS IN THE SUB-TROPICAL MID SOUTH, USA.. MAYDICA. Vol 48:21-27 Interpretive Summary: Corn production in Mississippi has nearly quadrupled during the past 15 years from slightly less than 100,000 acres in 1985 to more than 410,000 acres in 2000. Corn hybrids have changed considerably during the past 30 years with plants that have more erect leaves and better stress tolerance. Most corn in Mississippi is still grown in 40-inch rows as compared to 30-inch rows in the Corn Belt where most of the recommendations on plant populations have been made. This study was designed to evaluate the influence of different spacings within the row on corn production in Mississippi with particular attention to agronomic qualities and mycotoxin incidence. The study also compared possible differences between normal and Bt hybrids. Yields increased as plant populations increased due to the shorter distances between plants within a row. No adverse effects regarding aflatoxin or fumonisin were measured with increasing plant populations. The ratio of leaf area to land area, known as leaf area index, increased with increasing plant populations which would allow the crop to capture and use more of the available sunlight for growth. Corn can be grown in Mississippi at plant populations of 32,000 plants per acre in 40-inch rows with no loss in yield or grain quality.
Technical Abstract: Modern maize (Zea mays L.) hybrids have been developed to withstand high plant densities and produce high grain yields under such conditions. The culture of modern maize hybrids, including Bt hybrids, in the Mid South is limited. Six commercially available maize hybrids, two Bt and four normal, were grown using a 101.6 cm row spacing and plant densities of 43,000, 48,000, 54,300, 64,000 and 76,500 plants ha*-1 in 2000 and 2001 at the Mississippi State University Delta Branch Experiment Station in Stoneville, MS. Yields increased with increasing plant density. Grain bulk densities varied among plant densities but no trend was evident. Kernel weights, ear weights, and leaf area plant*-1 all declined with increasing plant density. However, declines in kernel and ear weights did not affect grain yield, indicating ears per unit land area was the most important yield component. Leaf area index also increased with increasing plant density thus negating the decline in leaf area plant*-1. Leaf area index was higher in 2000 than in 2001, probably due to more rainfall. Hybrids differed in LAI, yield, kernel bulk density and kernel weight, but these differences were not correlated. Aflatoxin levels were very low both years and well below the maximum allowable level. Fumonisin levels were higher in 2001(5.0-7.9 mg kg*-1) than in 2000 (0.5-1.6 mg kg*-1). This was most likely due to less rainfall and high ambient temperatures during reproductive growth. Maize can be grown in the Mid South USA at plant populations of 76,500 plants ha*-1 in 101.6 cm rows with no adverse effects on yield or grain quality.