Performance of brassica cultivars from New Zealand and United States seed sources in southeast Ohio, USA.

摘要

A replicated trial was conducted in SE Ohio during 1994. Forage brassicas were sown into a sward composed of temperate perennial species during July. Brassica napus (swedes) cv. Doon Major and Highlander, Brassica rapa (turnips) cv. Purple Top, Rondo, Appin Stubble and Wintergreen, rutabaga [Brassica napus] cv. Purple Top, Brassica oleracea (kale) cv. Premier and a Chinese cabbage-turnip hybrid [Brassica campestris] cv. Tyfon were sown at 2.1 kg/ha, except kale which was sown at 4.2 kg/ha. Total DMyield ranged from 5.46 t/ha for Premier to 8.88 t/ha for Rondo. Tyfon and Appin exhibited the highest yield of tops, Rondo had the highest root yield, while Rondo and Doon Major had the highest combined yields of tops and roots. Rondo turnip tops were significantly higher in CP than the kale, rutabaga, Tyfon or Wintergreen although no significant differences in root CP contents were observed. Potassium and calcium levels in the tops were high. No significant differences were observed in neutral detergent fibre content among species and fibre levels were low. Premier (kale) survived the entire winter (22degC minimum), but during late autumn the quality of other species declined. By Jan. all the cultivars except Premier displayed damage. Highlander stillhad 33% of its tops green and the roots were intact. Wintergreen had a similar proportion of tops intact but the roots had started to soften. Doon Major and Purple Top had firm roots but brown tops. By Apr., Premier had recovered from the winter and hadresumed rapid growth. All cultivars were accepted by lambs and stocker calves. It is suggested that brassicas may be used to extend the grazing season. In this assessment, Doon Major, Highlander and Appin Stubble were acceptable in DM, yield and CP content. It is suggested that brassicas may be especially useful for young growing stock with high nutritional requirements. It is also suggested that special precautions should be taken due to possible high nitrate levels, mineral imbalances and low fibre content. It is concluded that brassicas should be grazed in combination with other stockpiled grasses or hay to reduce potential metabolic and digestive disorders.