|Baumhardt, Roland - Louis|
Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 7/5/2000
Publication Date: N/A
Technical Abstract: A generally accepted rule for dryland grain sorghum [Sorghum bicolor (L.) Moench] production is to plant into soil with adequate water for crop establishment. However, the optimum planting time and population for cultivars of various maturity classes is still debated. Our objectives were to identify the desired planting date, population, row spacing, and cultivar maturity class combination for optimum production and risk management of dryland sorghum. Using the crop growth simulation model SORKAM, known Pullman soil (fine, mixed, superactive, thermic Torrertic Paleustoll) conditions, and long-term (1958-1999) weather and production records, we evaluated all combinations of planting dates (15 May, 5 June, 25 June), populations (30, 60, 120 x 1000 plants/ha), row spacing (0.38 and 0.76 m), and cultivar maturity classes (early, medium, late) on sorghum yield. Compared with observed values, SORKAM underestimated yield about 20% %(r2=0.64), which was more frequent and larger for simulated late planting dates or the late maturing variety. Both lower plant population and narrow row spacing increased the modeled yield independent of planting date or cultivar maturity. Generally, the earlier cultivar maturity class achieved greater yields, while both early and late planting dates limited yield.