Weed management constraints under climate change

A series of models was used to assess the effect of climate change on seven different farm types in 13 locations in England and Wales. The models used included simulations of crop yield responses and weekly Available Work Days (AWDs) to determine the pattern and timing of crop production under one climate change scenario. The project used the UKCIP98 Medium High scenario, which projects a warmer climate (1.7-2.0degreesC) and a higher annual rainfall (1-5%) giving wetter autumns and winters, but drier summers than at present. The ECOMAC II available work days model results indicated that in spring, AWDs may remain at current levels or decline, whilst in early autumn, soil moisture deficit (SMD) will be higher, but fields will then become too wet to perform fieldwork sooner than at present. The climate change scenario also suggests a longer growing season. This could mean an earlier start to spring weed growth with potentially fewer spray days to control them. Harvests may be easier in the drier conditions, but this may reduce post harvest opportunities for weed germination and hence control. Early cultivations may be difficult with a shorter period of suitable conditions and once fields become wet in the autumn, there could be fewer opportunities for late season herbicide spraying.