Risk Management in North Texas Soybean: Mid-March Soybean Plantings Uncertain; Maturity Group IV Cultivars Reliable

The popularity of early (March and April) soybean plantings using maturity groups (MG) 3.9 to 5.1 has become widespread among commercial growers in north Texas due to the adverse impact of hot and dry weather in July and August. The efficacy of April planting is well documented, but there is less consensus on whether March planting is worth the risks associated with potentially cold, wet weather at planting. Likewise, it is not clear whether cultivars maturing earlier than MG 3.9 or later than MG 5.1 would be competitive under March plantings. In 2002 and 2003, we grew 20 soybean cultivars ranging from MG 0.8 to MG 6.1 on low-yielding sites with poor surface drainage and clay soil textures in the northern Texas Blacklands at Prosper, Texas (33.2°N). Four planting dates ranged from mid-March to mid-May and July drought was severe both years. Plant stands from March planting dates were lower than April planting dates. In 2002, the 15 March planting date (12 bu/acre) was out-yielded by later planting dates (16 to 23 bu/acre). In 2003, the 1 April (16 bu/acre) planting out-yielded the other three plantings (11 bu/acre). Although yield was affected by planting date-by-cultivar interactions, MG IV cultivars were generally higher than other MGs regardless of planting date. Early-maturing cultivars planted in March were visibly shorter than the same cultivars planted later. In the 14 March 2003 planting only, fungicide-treated seed resulted in a 3 bu/acre yield increase above the untreated seed. Our results support two ideas. First, mid-March planting dates in this region can often be less competitive than April planting dates if stand loss and poor seedling growth associated with wet (2002) or cold (2003) weather occurs. Second, cultivars from MG 3.7 to 5.1 are likely to be the most competitive cultivars across a wide range of planting dates when grown on heavy clay soils in north Texas.