Tillage, planting date, and plant population effects on dryland corn

Dryland corn (Zea mays L.) usually is not grown in western Kansas because of its low yield potential under drought stress. A study was conducted at the Southwest Research-Extension Center near Garden City, KS, from 1991 through 1994 to determine proper management practices for dryland corn. Corn was planted in a wheat (Triticum aestivum L.)-corn-fallow rotation in early (D1), mid (D2), and late (D3) May at plant populations of 12 000 (P1), 18 000 (P2), and 24 000 (P3) plants/acre with conventional tillage (CT) and no tillage (NT). No tillage increased yields 100% in the driest year (1991), increased yields by 41% in 1994, and resulted in yield increases in most comparisons in the remaining years. The highest yields in the dry year of 1991 resulted from D1 and D3, whereas D1 and D2 usually produced the highest yields in all other years. In 1991, yields declined with increased plant population, but the average yield reduction of 16% for P3 with NT was half that with CT. In other years, yields usually increased with an increase in population. In 1992 and 1993, P3 resulted in average yield increases,over P1 of 41% and 28% with NT and CT, respectively. In 1994, NT usually produced the most grain with P2, whereas population increases did not increase CT yields. We conclude that dryland corn in southwest Kansas should be planted in early to mid-May at plant populations not exceeding 18 000 plants/acre. No tillage is essential for adequate yields in dry years and will usually result in yield increases in years with more favorable climatic conditions.