Planting date, hybrid maturity, and plant population effects on soil water depletion, water use, and yield of dryland corn

Dry land corn (Zea mays L.) yield in western Kansas is limited by high temperatures and low rainfall. The number of corn hectares has increased in recent years due to improved hybrids, acceptance of reduced- and no-till practices, and favorable weather conditions. Research was conducted near Garden City, KS, from 1996 through 1999 to determine the effects of hybrid maturity, planting date, and plant population on soil water depletion, water use efficiency (WUE), and yield of dryland corn. Five hybrids with relative maturities of 75 (H1), 92 (H2), 98 (H3), 106 (H4), and 110 d (H5) were planted in mid-April (D1) and early May (D2) of each year (the 75- and 92-d hybrids were not planted in 1996) and thinned to populations of 30 000 (P1), 45 000 (P2), and 60 000 (P3) plants ha(-1) in a wheat (Triticum aestivum L.)-corn-fallow rotation. Depletion of soil water increased with hybrid maturity. In addition, higher populations tended to remove more water from the lower portion of the profile. Hybrids usually yielded more at the D2 planting date. In the most stressful year, grain yield averaged 97% more for D2 and water use efficiency averaged 85% more. For the 1997 through 1999 period, WUEs for D2 were 43, 45, 29, 30, and 37% higher vs. D1 for H1 through H5, respectively. In summary, earlier planting decreased yield and WUE. The highest yields and WUEs were achieved with the later planting date, combined with later-maturing hybrids and higher plant populations.