Dryland Corn in Western Kansas

Dryland corn (Zea mays L.) yield in western Kansas is limited by high temperatures and low rainfall. The number of hectares has increased in recent years due to improved hybrids, acceptance of reduced- and no-till practices, changes in the farm program, 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 the yield of dryland corn. Five hybrids with 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 (H1 and H2 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. The early May planting date (D2) produced an average of 1.51 Mg ha -1 (31.9%) more grain than did Dl. In the year of the poorest rainfall distribution, D2 resulted in 2.83 Mg ha -1 (96.8%) more grain. Yield usually increased with relative maturity and plant population. The average yield increases were 13.5% from P1 to P2 and 4.3% from P2 to P3. Yield increases with higher populations were greater for earlier hybrids than for later ones. Yield of H5 was 32.6% lower at P3 than P1 in the driest year. Dryland corn should be planted in early May in western Kansas. To minimize yield reductions in dry years, relative maturities should not exceed 106 d, and populations should not exceed P2.