Water use efficiency of forage kale crops

There is little information on the impact of water availability on yield potential of field-grown forage kale in summer in the dry east coast regions of New Zealand. A field experiment investigating dry matter (DM) production, water extraction, water use (WU) and water use efficiency (WUE) was carried out on a deep Templeton silt loam soil at Lincoln, Canterbury, in 2013. The experiment had two water treatments: 1) rain-fed control, and 2) full irrigation (evapotranspiration replaced weekly). Plant water use more than doubled with irrigation compared with rain-fed plots (774 vs. 316 mm), but WUE was similar for the two treatments, averaging 44.5 kg DM/ha/mm. Therefore, the total DM yield increase from 17 t DM/ha for the rain-fed plots to 27.7 t DM/ha for the fully irrigated plots was attributed to the additional WU of the crops, and not the efficiency with which the water was used to produce biomass. Farmers are increasingly growing kale on lighter soils than used in this experiment and therefore irrigation will be beneficial.