Effects of Seeding Rate on Dry Matter Yield of Two Forage Rape Varieties

Abstract

Husby and Krieg (1987) reported that average Alaskan forages were deficient in energy for beef cattle and protein levels were marginal for growing animals. Both the energy and protein of Alaskan forages are low for lactating dairy cows (Brundage and Herlugson, 1984). Energy and protein concentrates are imported to Alaska from elsewhere in the U.S. High transportation costs make these imported feedstuffs expensive for Alaskan livestock producers. Brassica crops, such as rape (Brassica riapus L.) and turnips (B. rapa L.) have been widely studied as forage crops because they have the potential to produce high yields of excellent quality forage. Jung et al. (1986) demonstrated this potential when they reported that Brassica spp. yielded 4-7 tons DM/A and the forage was highly digestible (80-90% in vitro dry matter digestibility). Crude protein was relatively low for turnip roots (8-12%), but top growth was high (up to 27%). Lambert et al. (1987) found that the quality of Brassica spp. was too high for optimum performance of growing lambs. They reported that it was necessary to include some coarse feed, such as grass hay, to increase the fiber content in the diets of these animals. The potential of Brassica crops has been investigated in Alaska (Mitchell and Krieg, 1985; Panciera et al., 1990). The yield and quality of these crops in Alaska were similar to the levels observed in the Lower 48 states. Basic agronomic information is needed in order to develop management recommendations for Brassicas in Alaska. Research is underway to define the nitrogen and phosphorus fertilizer requirements (Panciera etal., 1990). This report summarizes the results of a two year study concerning the effects of seeding rates on dry matter yields of two Brassica hybrids.