Performance of setaria in the northern North Island

Abstract

Setaria sphacelata is a perennial C, grass that has high potential summer yield, but its persistence and cool-season production are poor. An experiment investigated whether a winter oats cover crop could negate these poor traits. While oversowing oats into established setaria increased total winter-spring herbage production, the use of a cover crop reduced setaria persistence despite minimum soil temperatures being 1.5"C higher. Starch and soluble sugar levels in three different leaf and stem fractions of setaria were low and showed little seasonal variation. S. sphacelata and S. neglecta plants that had survived previous evaluations were transplanted into a field nursery and screened for a further 3 years. From this nursery, blocks of four phenotypically different lines were then established and their performance (herbage production and quality) was assessed for 2 years. Mean annual yields of the more productive blocks were 12.5 t /ha, 60% of this occurring during January-March. Herbage quality was assessed as being low-medium, leaf in vitro digestibilities and crude protein being 70% and 12% respectively. Within this "persistent" population, soluble sugars in the basal fractions of the plant appear important in assisting cool-season persistence. The place of a perennial C, grass such as setaria in farm systems was investigated using the computer model Stockpol. A smsll specialist block of setaria may have merit for feeding breeding stock where there is a need to miriimise the risk of drought in northern zones of New Zealand. Keywords: carbohydrates, cover crop, forage quality, persistence, Setaria spp.