Ground Cover Supplement : GC Supplement - Crop sequencing
5 Issue 133 | Mar – Apr 2018 | GRDC GROUNDCOVER SUPPLEMENT: CROP SEQUENCING GROUNDCOVER PROFITABILITY will also be monitored at the sites. Modelling to compare sequences at the four field sites, using APSIM (Agricultural Production Systems sIMulator), found that systems involving long fallow (fallow/ canola/wheat) or continuous early- sown wheat with low (decile 5) nitrogen strategies have the lowest predicted system efficiency (below $1.50 per hectare per millimetre of rainfall). Although simulated continuous early-sown cereals with higher nitrogen could match the predicted efficiency of more diverse crop sequences (approximately $2.00 to $2.50/ha/mm), the effects of weeds and diseases were not captured by the simulation and are known to become significant problems over time. The experiments provide an opportunity to ground-truth these predicted outcomes with local growers and consultants. LONG-TERM TRIAL This type of modelling has been validated at CSIRO’s 28-year, long- term crop experiment at Harden in the PHOTO: JOHN KIRKEGAARD higher-rainfall eastern area of southern NSW where good soil characterisation and frequent soil nitrogen, water and crop measurements across that period allow confidence in the predictions. Here it was possible to investigate the predicted impacts of some of the proposed improvements to investigate system efficiency. The crops (15 wheat, five canola, five lupin, one pea, one oat and one fallow) were generally sown in mid-May, with reasonable summer weed control and adequate nutrition according to expected yield potential. The validated simulation at Harden predicted increases in average wheat and canola yield of 33 and 72 per cent respectively above the observed yields with the package of improved fallow weed control (small effect) and earlier sowing of long-season wheat and canola varieties – but increased nitrogen supply was required to capitalise on this potential (Table 1). The benefits from long-season crops predicted at Harden are perhaps not surprising for this high-rainfall site. The new project will allow identification of the most effective combinations of crop sequence, sowing time and nitrogen management to improve the conversion of rainfall into profit across the crop sequence in different rainfall zones. As well as comparing traditional practices (such as sowing date and nitrogen management) the trials will also look at recent innovations such as early-sown slower-maturing crops, higher-value lentils and chickpeas or diverse use grain legumes, dual-purpose crops and improved nitrogen management to see how these impact on the legacy effects of water, nitrogen, weeds and disease across the cropping cycle. Novel interventions (intercrops, spring-sown crops, self-regenerating annual pastures and summer cover crops) were also of interest at specific sites and will be included. o GRDC Research Code CFF00011 More information: Dr John Kirkegaard, CSIRO, 02 6246 5080, email@example.com; www.farmlink.com.au/project/crop-sequencing (From left) Greg Condon (Grassroots Agronomy), Graeme Sandral (NSW DPI) and Jeremy Whish and Tony Swan (CSIRO) discuss the crop sequencing trial field site at Wagga Wagga, NSW.
GC Supplement - Profit drivers
GC Supplement - Stubble