Double cropping is a viable production system in the southeastern United States. Soft red winter wheat is currently the only winter cash crop under large scale production in this region. The development of additional winter crops is therefore necessary for implementing economical and productive double-cropping systems. Rapeseed has potential to develop as a major winter cash crop in this area, although current production is estimated at less than 2,000 hectares. Historically, only winter cultivars, most developed for northern Europe, have been evaluated in this area (Hoveland et al. 1981, Duncan and Hoveland 1986). Mild winters and rapidly rising spring temperatures typical to this region often cause inadequate vernalization and heat stress during bloom and seed fill of winter cultivars. More recently, cultivars developed for spring planting in more northern latitudes have been successfully grown as a winter crop in this region.
This study was conducted to compare the potential of spring and winter rapeseed cultivars when grown as a winter crop in the Coastal Plain and Piedmont regions of the southeastern U.S.
'Westar', 'Cascade', and 'Glacier' were also evaluated in a planting date study at Tifton during the fall of 1987. The treatments were arranged in a split-plot design with four replications. Planting dates formed the main plots and cultivars the subplots. The plot size and row pattern were as described above. Planting dates were at approximately two week intervals from 18 September to 24 December.
The bloom date of 'Westar', a spring type, was affected by planting date, in contrast to bloom dates of 'Cascade' and 'Glacier', winter types, which were relatively unaffected (Fig. 1). Planting 'Westar' earlier than November induced precocious flowering during the fall or winter months (Fig. 1). This could predispose this cultivar to injury in more severe winters.
Relatively mild winters are typical in the Coastal Plain region (approximately 5°F warmer than the Southern Piedmont). Spring cultivars may offer better yield potential here than winter types. Using spring cultivars for winter production in this area eliminates vernalization problems frequently experienced with traditional winter cultivars. Earlier bloom and maturity of spring type cultivars may reduce heat stress during seed fill and improve the potential for double crop production of soybean, sorghum (Duncan and Hoveland 1986), and peanut after rapeseed harvest. However, the identification and/or development of winter-hardy spring type cultivars will be necessary to insure survival during occasional severe winters.
|'Global'||2743||627||Mar 20||May 30||97|
|'Hanna'||2552||625||Mar 20||May 30||94|
|'Westar'||1586||624||Mar 22||May 30||84|
|Mean||2294||625||Mar 21||May 30||91|
|'Cascade'||1907||502||Mar 24||June 5||102|
|'Crystal'||2434||631||Apr 2||June 16||119|
|'Glacier'||2168||642||Apr 3||June 14||132|
|Mean||2169||592||Mar 30||June 12||117|
|Spring vs. Winter||n.s.||n.s.||**||**||**|
|'Global'||2641||722||Feb 28||May 7||147|
|'Hanna'||2577||705||Mar 21||May 17||135|
|'Westar'||2376||722||Mar 20||May 18||127|
|Mean||2531||717||Mar 13||May 14||137|
|'Cascade'||1290||641||Mar 28||May 24||142|
|'Crystal'||1120||581||Apr 5||June 6||147|
|'Glacier'||936||575||Apr 16||June 5||152|
|Mean||1126||600||Apr 6||June 1||147|
|Spring vs. Winter||**||**||**||**||n.s.|
Fig. 1. Effect of planting date on bloom date of three rapeseed cultivars at Tifton, Georgia, 1987-88.