Influence of Tillage System on Soft Red Winter Wheat Cultivar Selection

Soft red winter wheat (Triticum aestivum L.) producers in the southeastern USA are adopting no-till production practices. Official wheat cultivar testing programs, however, are conducted in conventional-till. The objective of this research was to determine whether soft red winter wheat cultivars perform differently across tillage systems, indicating the need for no-till cultivar testing programs. Twelve winter wheat cultivars commonly produced in the southeastern USA were tested in a split-plot design with tillage system as the main effect. The test was located in the North Carolina Piedmont and Coastal Plain in 1996 and 1997. In the Piedmont the soil type was Hiwassee clay loam (fine, kaolinitic, thermic Typic Rhodudults), and in the Coastal Plain the soil was Goldsboro sandy loam (fineloamy, siliceous, subactive, Aquic Paleudults). Plant density after emergence, head density at harvest, kernel weight, grain yield, and test-weight were determined and compared across cultivars and tillage systems. For each of these variables, environment and cultivar effects were significant (P ≤0.05). Tillage system had a significant effect only on plant density with average no-till stands being 8.3 % lower than those in the conventional-till system. Relative cultivar performance, or rank, did not change across tillage systems for any of these variables. Consequently, soft red winter wheat cultivars that perform well in conventional-till will probably be the best adapted for no-till production. Separate cultivar trials are not required for the two tillage systems. Research QuestionOver the past 10 yr, southeastern producers have adopted no-till small grain production practices. The number of wheat acres in no-till has increased rapidly, especially over the last few seasons. To select wheat cultivars best adapted to the region, growers typically rely upon results from official cultivar testing programs conducted through the land grant universities. These testing programs are historically conducted in conventional-till systems. When grown no-till, wheat generally has reduced stands, slower vegetative growth, and slower tillering. Consequently, wheat cultivars that are best adapted for no-till, may be different from those that produce the best in conventional-tillage. The objective of this research was to determine whether soft red winter wheat cultivars performed differently across tillage systems for grain yield, test-weight, stand establishment, head density at harvest, or kernel weight. If, for example, cultivars were found that ranked high in one tillage system, but performed poorly in the other, it would indicate the need to include a no-till component in southeastern winter wheat cultivar trials. This 2-yr study was conducted at two geographically diverse locations in North Carolina. Literature SummaryStudies to determine cultivar performance across tillage systems for soft red winter wheat in the Southeast have not been reported and studies of hard wheats from other areas have resulted in mixed conclusions. This makes it difficult to predict whether separate cultivar trials have to be conducted in no-till and conventional-till systems. In the North Central Great Plains, research with spring wheat has shown that cultivars change their ranking when they are grown in different tillage systems. For winter wheat in the North Central Great Plains, no-till production is recommended to trap snow and protect the crop from freeze damage and research has shown that these cultivars do not change their ranking across tillage systems. In the Southern Plains, hard red winter wheat cultivars have been shown to change their ranking across tillage systems for date of anthesis, leaf-area duration, and grain fill, but not for yield. Study DescriptionTwelve soft red winter wheat cultivars were grown in no-till and conventionaltill systems in the North Carolina Piedmont (Salisbury NC) and Coastal Plain (Kinston, NC) in 1996 and 1997, to determine whether their relative performance or rank for grain yield, test-weight, plant density after emergence, head density, and kernel weight would change across tillage systems. At both locations, winter wheat followed corn harvested for grain leaving 1 to 2 in. of residue on the soil surface. The conventional-tilled plots were disked prior to planting. No-till wheat was planted directly into the corn residue after applying glyphosate. All other agronomic practices were identical across tillage systems. A split plot design with tillage as the main effect and five replications at each location was used. Applied QuestionsDo soft red winter wheat cultivars rank differently for stand establishment between the two tillage systems? No. Stand was influenced by environment, tillage, and cultivar. The average stand density at the Coastal Plain was 25.3 plants/sq ft compared with 28.6 plants/sq ft in the Piedmont. Across years, average initial stand was 21.3 and 32.6 plants/sq ft in 1996 and 1997 respectively. Across years and locations, no-till initial stands averaged 25.3 plants/sq ft compared with 27.6 plants/sq ft in the conventional-till systems. While each of these variables affected stand, cultivars ranked the same across tillage systems. This indicates that cultivars that do well in stand establishment in one tillage system, are also the best in the other tillage system. Do soft red winter wheat cultivars rank differently for head density between the two tillage systems? No. Environment and cultivars were important in determining head density. Average head density was highest, 39.6 heads/sq ft, at the Coastal Plain in 1997 compared with 33.6 and 31.6 heads/sq ft at the Coastal Plain and Piedmont respectively in 1998. Tillage did not affect head density and cultivar ranking was similar between tillage systems. Do soft red winter wheat cultivars rank differently for kernel weight between the two tillage systems? No. Environment, and cultivar were important in determining thousand kernel weight. Cultivars that had high kernel weights in conventional-till also had the highest kernel weights in the no-till system. Do soft red winter wheat cultivars rank differently for grain yield or testweight between the two tillage systems? No. Test weight and grain yield were influenced by environment and cultivar, but tillage had no affect on these variables. Cultivar ranking for test weight and grain yield did not change across tillage system. RecommendationsFor each of the variables tested, stand establishment, head density, kernel weight, test weight, and grain yield, cultivar ranking did not change across tillage systems. Cultivars that did well in conventional-tillage systems continued to be the best adapted for no-till systems. Based on these findings, no-till wheat producers in the Southeast can use official cultivar test results to choose well adapted cultivars, even when these tests are performed in conventional tillage.