Tuesday, June 19, 2007 - 9:15 AM

Brassica spp. Performance in the Irrigated High Desert of the Southern Rocky Mountains.

Leonard M. Lauriault and Steven Guldan. Plant and Environmental Sciences Department, New Mexico State University, Agricultural Science Center, 6502 Quay Rd. AM.5, Tucumcari, NM 88401

Frost tolerance, high forage yield and quality, and planting and harvest management flexibility of forage brassicas may make them useful in irrigated environments climatically similar to high desert areas of the southwestern USA. A multiple-cut fall production system was used for two years at two high desert locations in New Mexico to determine the effect of planting date (mid-July and mid-August) on forage dry matter yield, crude protein (CP), and in vitro dry-matter disappearance (IVDMD) of three brassica species (kale, rape, and turnip). Harvests simulating short-duration intensive grazing were taken 60, 90, and 120 days after planting (dap) from four randomized complete blocks each year at each location. Generally, second and third harvest yields were negligible (<500 kg ha-1) in this environment; however, a significant year x planting date x harvest interaction occurred because the mid-July planting in one year produced 772 kg ha-1 in the second harvest. Precipitation differences and the unavailability of irrigation water after mid-October may have been factors. Species differed for total forage yield (2461, 3109, and 2983 kg ha-1 for kale, rape, and turnip, respectively, 5% LSD = 419). Across years, rape had highest first harvest yield, followed by turnip, then kale (2105, 2899, and 2486, kg ha-1 for kale, rape, and turnip, respectively, LSD = 241). Turnip produced significantly more yield than rape in the second harvest (314, 161, 412 kg ha-1 for kale, rape, and turnip, respectively, LSD = 241). With few exceptions, forage quality was high across treatments (152 and 610 g kg-1 for CP and IVDMD, respectively). Rape has greatest potential for use in single grazing (60 dap) systems in high desert environments similar to the southern Rocky Mountains, while turnip has greater potential for stockpiling to also allow root growth as an energy source for livestock or for rotational grazing systems.

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