GRAIN-SORGHUM AND PEARL-MILLET RESPONSE TO DATE AND RATE OF PLANTING

Pearl millet [Pennisetum glaucum (L.) R. Br.] often is grown in the same areas as sorghum [Sorghum bicolor (L.) Moench]. The crops are similar in use and adaptation, but differ in ways that might affect management requirements. For example, the high tillering capability of millet might result in different responses to plant population and planting date. A study to compare pearl millet and sorghum yield response to rate and date of planting was conducted for 2 yr at St. John, on a Naron fine sandy loam (fine-loamy, mixed, thermic Udic Argiustoll), and Manhattan, KS, on a Reading silt loam (fine, mixed, mesic Typic Arguidoll). In 1988, a millet hybrid (81-1056 x 86-9001), a millet variety (Senegal bulk), and a sorghum hybrid (DeKalb 39Y) were planted at 15 000, 45 000, and 135 000 plants/ha on three dates. In 1989, another millet hybrid (81-1086 x 87-8025) was added. The experiment was a modified split-plot design with dates of planting as main plots stripped across replicates and combinations of population and variety as subplots. Planting date had no consistent effect on either crop. Plant population had no effect on millet yield. Some yield components, particularly heads per plant, increased and compensated for low populations. Sorghum yield increased with increasing population, but plant population had no consistent effect on sorghum yield components. Sorghum yielded significantly more than millet at high populations, but not at low and medium populations. These results indicate that precise plant population is much less critical for pearl millet than for sorghum in determining final yield.