Should I keep my existing crops or spray out and replant?

By Trevor Philp, Pacific Seeds Grain Sorghum Technical Specialist

With an encouraging forecast for spring, some growers took advantage of available soil water from rainfall received during July and planted sorghum and corn in areas of northern New South Wales and the central Darling Downs.

For many, establishment has been mixed – with cooler-than-ideal soil temperatures, drying conditions post-planting, mice damage and late frost events all contributing.

Established crops are growing slowly due to these early setbacks and the lack of follow-up rainfall in early September. Apart from some cold spells, September and October have been warmer than average and quite windy, adding to an already challenging start.

Crops that are struggling to develop secondary roots will be at more risk of early season abiotic stress, such as nutritional deficiencies and attack from insect pests, including aphids, thrips and Rutherglen bug.

As winter crops – such as wheat, barley and chickpea – rapidly ripen and harvest begins, growers and agronomists need to keep a close watch on young summer crops, as insects will migrate from these winter crops in search of ‘greener pastures’.

A La Niña has now been officially declared, so when significant rainfall does eventuate, some growers may be faced with the difficult decision of keeping existing crops or spraying out and replanting.

Several factors need to be evaluated to make this decision: for dryland corn and sorghum, plant population is important – however, as a contributor to final yield, it is actually a relatively minor element.

Of more importance is, in fact, the uniformity of plant spacing and the evenness of crop growth – an evenly spaced low population will often perform better than a higher population of unevenly spaced plants.

Other considerations to replant will be expected yield, weed pressure, soil water profile, and the timing of year.

Trials conducted last season at the Pacific Seeds research farm evaluated the effect of increasing gaps (>50cm) in grain sorghum. We found significant yield penalty from ‘gappy’ establishments and a high ROI for replanting poorly established fields.

To see more of these results or to discuss your options for summer, please feel free to get in touch. https://www.pacificseeds.com.au/contact-us/

Trevor Philp