Productivity and quality of kale, swede, fodder beet and maize in Manawatu

Abstract

Winter grazing of forage crops can result in large losses of nitrogen (N) from leaching and consequently, deterioration in water quality in affected catchments. A viable alternative cropping option which can potentially reduce N leaching may be useful for maintaining productivity while minimising environmental risks. Maize could be a possible alternative crop because of its yield and low N as well as convenience to cut and carry system. Thus, maize, kale, swede and fodder beet were compared in a factorial randomised complete block design with or without N application. Dry matter (DM) yield ranged from 12,450 to 30,417 kg DM/ha with the highest yield achieved by maize hybrids. Yield was increased by N application, but there was no interaction between forage entries and N rates. Forage entries differed significantly in all quality traits while N application only affected crude protein (CP), soluble sugars and starch (SSS) and acid detergent fibre (ADF). Metabolisable energy (ME) was significantly different for all forage entries. It ranged from 9.5–11.0 MJ/kg DM for swede, fodder beet and maize and was <9.5 MJ/kg DM for kale. Maize hybrids showed the lowest CP (5.4–5.9%DM) and highest SSS (42.7– 48.0%DM). Dry matter yield was positively correlated with SSS (r = 0.58; P<0.001) and neutral detergent fibre (NDF) (r = 0.56; P<0.001). Similarly, ME was positively and strongly correlated with SSS (r = 0.79; P<0.001) while CP was negatively correlated with yield and all quality traits. The results highlight the advantages of maize having high DM yield and good feed quality under unlimited moisture conditions.