Effect of timing of harvest on nutritive value of four cultivars of kale (Brassica oleracea L. var. acephala)

Abstract

Abstract A single site, single year replicated study in Canterbury investigated change in nutritive value and dry matter (DM) yield of four kale cultivars harvested monthly between May and September. The proportion of leaf relative to stem was significantly higher for an intermediate kale ('Regal') and short marrow-stem kale ('Kestrel') compared with two giant kales 'Gruner' and 'Rawera'. Late winter loss of leaf was greater for 'Gruner' and 'Rawera' compared with 'Regal' or 'Kestrel'. Whole plant DM% remained stable through winter (average 11.9%). Lower stem contained more DM than top stem or leaf. The DM% of 'Gruner' was significantly higher than other cultivars. 'Kestrel' contained significantly more megajoules of metabolisable energy than other kales. Energy content of leaf and top sections of stem averaged 2.5 MJME/kg DM more than lower stem. Dry matter yield peaked in June then declined monthly thereafter for giant kales 'Gruner' and 'Rawera', but not 'Regal' or 'Kestrel'. The use of intermediate and short marrow-stem kales 'Regal' and 'Kestrel' is one management option to improve the leafiness and whole plant energy content of late winter feed crops. Keywords: Forage brassica, kale, nutritive value, winter feed, yield