Soybean Cultivar Response to Tillage Systems and Planting Date
The soybean [Glycine max (L.) Merr.] production area in the USA planted with reduced-tillage practices has doubled in the last two decades. Previous studies show that soybean cultivars yield similarly in various tillage systems when planted in well-drained soils. Reduced-till farmers are planting earlier than in the past, but planting date studies with various tillage systems and cultivars have not been reported. A 3-yr field study was conducted to compare soybean cultivar responses to various tillage systems at various planting dates. Six soybean cultivars were planted on three dates each year (average planting dates were: 7 May, 29 May, and 15 June) with two tillage systems: three passes with a tandem disk in the spring (TD) or notill (NT). A Hastings silt loam soil (fine, montmorillonitic, mesic Udic Argiustoll) was used in 2 yr and a Crete silt loam soil (fine, montmorillonitic, mesic Pachic Argiustoll) was used in the other. The determinate cultivar yielded less when planted on 7 May than on 29 May at 2.72 and 3.14 Mg ha−1 respectively. Indeterminate cultivars had similar yields for these two dates with 2.99 Mg ha−1. Yield of TD was 0.18 Mg ha−1 less than that of NT for 7 May, but was 0.19 Mg ha−1 greater than that of NT for 29 May. There were no tillage × cultivar or tillage × planting date × cultivar interactions. Although planting date was shown to be an important factor in cultivar selection, this study has shown that planting date is not a critical factor in the tillage-cultivar selection process. The best yielding cultivars in tilled performance tests will likely be the same as those from a no-till performance test, irrespective of planting date.
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