|Jung, G - RETIRED ARS EMPLOYEE|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 24, 1994
Publication Date: N/A
Interpretive Summary: There can be substantial savings in costs of animal production when the fall grazing season is extended with summer-planted turnips. Not enough is known about the interactive effects of planting date and harvest date on dry matter yield accumulation of turnip tops and roots. We showed that turnip yields of tops and roots were markedly influenced by planting and harvesting dates and by varietal priority for top versus root production. Savanna and All Top had relatively high priorities, Forage Star intermediate priority, and Purple Top had a low priority for top production. Turnip top yield generally peaked sometime in October, regardless of planting date, because top yields decreased in November due to leaf senescence and freezing injury. By contrast, turnip root yields generally continued to increase in November and early December. The proportion of yield in tops versus roots increased by delaying summer planting and decreased by delaying fall harvest. Yield of all varieties was about 20% higher on average than when being infested with Alternaria leaf spot. Farmers can reduce the risk of yield loss to leaf spot by using more than one planting date and disease resistant varieties. Turnips offer a very high production potential for extending the fall grazing season, with a with a wide range of top/root yields.
Technical Abstract: Summer-planted turnips (Brassica rapa L.) have been shown to be a highly productive crop, allowing farmers to extend the grazing season and lower animal production costs. A study was conducted to determine the influence of interactive effects of planting date and harvest date on morphological development and productivity of turnip in late fall. Turnip was seeded in rows on Hagerstown siltloam (fine, mixed mesic Typic Hapludalf) soil, utilizing a 6-planting date by 4-cultivar factorial treatment structure in a split plot design with planting date as whole plot, cultivar as the split plot and 4 replicates. Three to six harvest dates were used depending on planting date, resulting in an overall incomplete factorial treatment structure. Mean yield of all cultivars with optimal planting date/harvest date combinations was 11.5 Mg ha-1 without severe foliar disease and 9.7 Mg ha-1 with Alternaria sp. leaf spot. The interactive effects of planting date and harvest date on morphological development depended on priority of the cultivar for top/root production. Delay of planting from late July to late August decreased top and root production more in 1990 than 1989. An optimum harvest date for maximizing fall top yield occurred each year regardless of planting date. Root yields increased in November and early December whereas top yields did not. In general, total yields were high for crops planted in late July and harvested in late October or early November. Top/root quotient was increased by delaying summer planting, and decreased by delaying fall harvest. `Savanna' had the highest, and `Purple Top' had the lowest top/root quotient. These crops offer very high production potential for late fall grazing with a wide range of top/root yields