General Comments (May 2014)
The early autumn break was welcome relief for those handfeeding livestock, providing exceptional autumn feed growth due to the warm soil temperatures and associated soil Nitrogen mineralisation, after a relatively long, hot dry period. Livestock markets rose predictably in response to both stock being withheld from market due to adequate paddock feed, plus restocker demand from those who were understocked for the pasture growth. However, pasture growth will slow considerably from now due to soil temperatures dropping, with the result that realistic assessments now have to be made regarding the number of stock which can be carried through winter.
Cropping paddocks which have had good autumn rain have produced significant germination of weeds, providing an ideal opportunity to reduce seed bank levels of problem weeds prior to sowing.
An analysis carried out of client average crop yields and rainfall over the last 28 years of data held, has revealed a significant reduction in farm average crop yields in line with reduced rainfall over this period. However in most cases, crop input levels have increased during this period, despite the reduction in yields. This is considered to be mainly due to the general shift away from mixed farming based production systems, where legume based pastures provided Nitrogen for subsequent crops, and integrated weed management practices involving grazing, some cultivation and stubble burning were carried out.
Continuous cropping systems relying totally on artificial Nitrogen and selective in-crop herbicides have evolved, bringing with them higher costs plus production and financial risks. It is obvious from soil test results that many clients are over-fertilising crops, with Phosphorus levels of 50 – 70 ppm Colwell being common. RMS and other trials have repeatedly shown little or no economic crop yield responses where soil Phosphorus levels are above 35 ppm Colwell. Likewise with Nitrogen fertiliser applications, target yields are often overly optimistic, with the result that excessive rates of Nitrogen fertiliser are being used, adding unnecessarily to costs.
A trial carried out by RMS last year reported later in this News Bulletin, produced an average wheat yield of 3.27 t/ha on a paddock with a relatively long cropping history, with no economic response to applied Nitrogen.
It should be remembered when planning crop inputs, that the yield having the greatest probability of occurring, is by definition the median or Decile 5 yield calculated from historical yield data from that farm.