Many clients in the north have received significant rain during late March, leading to successful establishment of early-sown grazing crops. Following are some issues to consider with respect to management of these crops:
- Red Legged Earth Mite (RLEM) – RLEM hatch after a period of at least 5mm of accumulated rain over a five day period, followed by 10 days of average daily temperature remaining below 16oC. Although rainfall in some areas has been significant, average daily temperatures have remained well above 16oC to date. Given these conditions (good moisture and warm temperatures), early crop growth will be rapid and it is unlikely that RLEM will be a significant threat to early-sown grazing crops. Once temperatures cool down, there will no doubt be a hatching of RLEM, which may pose more of a risk to later sown crops germinating under high pressure situations. Monitoring first year-in paddocks and crop margins which adjoin pastures and non-crop areas, is recommended.
- Grass weeds – Where good rain has fallen there has been a significant germination of grass weeds. For the early sown crops, these have been controlled with a pre-sow knockdown. For later sown crops, this presents the opportunity to apply a double knock to areas where weed populations are higher, or where Glyphosate resistance is a threat. Whilst this does add cost, it is important to take the opportunity to maintain the sustainability of Glyphosate, by rotating herbicide groups used.
- Broadleaf weeds – There have been large germinations of weeds such as capeweed, Paterson’s curse, clover and thistles. Under current conditions, these weeds will grow rapidly and compete with crops. In dry sown crops, these will likely need to be controlled early, possibly before grazing. Where these weeds have germinated prior to sowing, they should be controlled with the knockdown, resulting in crops which should be relatively clean of broadleaf weeds early in the season.
- Pre-emergent herbicides – In some cases the decision to use expensive pre-emergent herbicides is not clear cut, while in others, where weed pressure is high, it is a straightforward decision. Where weed pressure is relatively low and a good knockdown is achieved, there may be scope to drop some of these products, resulting in reduced selection pressure on the herbicide, plus a cost saving. This may be more prudent for later sowing into cooler soils where pre-emergents have a more significant effect on early crop growth. However this should be discussed with a consultant who knows the situation before doing so, as there can be longer term considerations which influence the decision.
- Fertiliser rates – Crops sown early into warm soil are less responsive to Phosphorous. Where soil Phosphorous levels are high and removal in the previous year was low, there may be scope to further reduce starter fertiliser rates on early sown crops.