APSIM kale appropriately simulates spring and autumn grown forage kale crops in Tasmania

Kale (Brassica oleracea var. acephala) is an important winter feed on many dairy farms in the temperate regions of Australia and New Zealand. A key challenge in lifting farm productivity and profitability is understanding the effects of biophysical factors on growth and development of this crop. Biophysical models help in this regard, and can be used to test new production practices, or identify efficiencies that can be gained over current agronomic practices. The objective of this study was to determine if the APSIM kale module appropriately simulated the growth and development of forage kale crops in Tasmania. The results of simulations using site-specific soil and climate data and crop management were compared with data collected from field experiments and commercial kale crops. Comparison of the modelled growth and leaf development to observations in the field showed the model appropriately represented both biomass accumulation and phenological development. Relationship between modelled and observed biomass (n = 35) explained 86% of the variation with a mean bias of -37kg DM/ha over the life of the crop. Relationship between modelled and observed number of leaves (n = 16) explained 93% of the variation with a mean bias of 0.4 leaves over the life of the crop. The APSIM kale module includes predictions of soil water and nitrogen use and once verified will allow more precise management scenarios to be tested and implemented for optimising productivity while minimising the environmental impact of dairy winter forage systems.