Planting Season and Harvest Date Effects on Dry Matter Production and Nutritional Value of Brassica spp. in the Southern Great Plains1
- S. C. Rao and
- F. P. Horn2
Brassica spp. may serve as highquality forage crops in parts of the Southern Great Plains when most warm- and cool-season forages are unproductive. Field studies were conducted to assess the forage (shoot and/or root) yields, crude protein (CP), and digestibility (IVDMD) of turnip root crops (Brassica rapa L., ‘Purpletop’, ‘Cyclon’, ‘Frisia ’, and ‘Tyfon’; a Chinese cabbage × stubble turnip hybrid) and leafy-stem crops [‘Winfred’ rape (B. napus L.) and ‘Merlin’ kale (B. olerucea L.)] at different harvest dates. All six Brassicas were established on a Dale silt loam soil (fine-silty, mixed, thermic, Pachic Haplustoll) in September 1982 and 1983 (fall) and March 1983 and 1984 (spring) under dryland conditions. Shoot dry matter (DM) production for root crop cultivars was highest 85 and 95 days after planting in fall and spring, respectively. The greatest total plant DM yield was produced by Cyclon in the fall and Purpletop in the spring (7.4 and 7.6 Mg ha−1, respectively). Cyclon and Tyfon produced 0.7 Mg ha−1 more shoot DM, whereas Purpletop and Frisia produced 0.4 to 0.9 Mg ha−1 more root DM during their maximum DM production period. In early harvests, DM yields of kale were less than those of rape, but after 90 days growth, yields were similar (7.0 Mg ha−1). Shoot CP levels of root crops averaged 220 g kg−1 and were about 25 to 60 g kg−1 greater than root levels. The IVDMD of mots ranged from 670 to 840 g kg−1 and were approximately 60 to 120 g kg−1 higher than values for shoots. Levels of DM, CP, and IVDMD for all cultivars were similar or better in fall growing season and did not decline as rapidly compared with spring. Cyclon and Purpletop have the potential to provide high yields of high-quality forage during the forage deficit periods of Southern Great Plains.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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