Effects of Planting Date on Winter Canola Growth and Yield in the Southwestern U.S.

Abstract

Canola ( Brassica napus L.) has potential to become alternative cash crop (healthy oil for human and meals for animal uses) with tremendous rotational benefits in the Southwestern U.S., a region dominated by cereal-fallow cropping systems. However, information on optimum planting date for its successful production is limited. Field experiments were conducted in 2011-12 and 2012-13 seasons under irrigation condition to study the response of canola growth and yield to planting dates at Clovis, NM. Three planting dates (mid-September, late-September and early-October) and four canola varieties (early flowering: DKW41-10 and DKW46-15; medium flowering: Riley and Wichita) are studied. Fall plant stand density is significantly higher for early-October than mid- and late-September plantings. However, a ratio of fall to spring plant stand density indicates a greater reduction in spring plant stand density with early-October (25%) and mid-September (19%) than late-September (7%). Vegetative (by 13 days) and flowering (by 7 days) duration phases are significantly shortened with delay in planting. The decline in aboveground dry matter (DM) due to delayed planting resulted in significant seed yield reduction in both 2011-12 (26%) and in 2012-13 (8%) when early-October and mid-September plantings were compared. There was a positive relationship between final DM and canola seed yield, accounting for 84 and 34% variation for 2011-12 and 2012-13 seasons, respectively with the 2011-12 environmental conditions being conducive for genetically controlled variation in DM production to be more apparent and strong in explaining the variation in seed yield among varieties. Medium-flowering varieties produced higher DM (9741 vs. 8371 Kg&#8226ha -1 ) and seed yield (2785 vs. 2035 Kg&#8226ha -1 ) than early-flowering varieties. In addition to seed yield, DM can be used as an indirect selection criterion for seed yield in variety selection and appropriate planting dates including a guarantee for high crop residues (~75% of the total aboveground biomass) production to make canola a potential alternative cash and rotational break crop in the Southwestern U.S.