Long-term simulations of wheat yields showed that, with early sowing in the Lower North, median wheat yield increased by 50 kg/ha for every kilogram of nitrogen applied at sowing, up to a maximum nitrogen rate of 50 kg/ha. A satisfactory prediction of dry matter, grain yield and grain weight was obtained for wheat when the models were extended to other trials at Roseworthy (Lower North), Minnipa (Upper Eyre Peninsula) and Wunkar (Murray Mallee), based on limited soil data. This was possibly due to inadequate remobilisation of nitrogen from the straw and roots to the grain by the simulated crop. Prediction of grain protein was underestimated in all cases, including where nitrogen in the shoot was overestimated. For most variables of crop growth and soil water, the simulated data were mostly within 2 standard errors of the measured means. Thus, the soil nitrate had to be reset at sowing for the following barley crop simulated soil nitrate agreed with the measured data in this season when this nutrient was low. Simulation with SOILN2, however, largely underestimated soil nitrogen, due to excessive uptake by the simulated wheat during the season when nitrogen was abundant and water supply readily available. Simulation data for soil water, from SOILWAT2, was consistent with measured data. The NWHEAT model satisfactorily predicted above-ground dry matter, leaf area index and grain yields for both crops in rotations with either grassy (Grass) or medic (Medic) pastures, including the lack of significant response of yield to nitrogen fertiliser applied to wheat at sowing.
#APSIM WHEAT SIMULATOR#
The Agricultural Production Systems Simulator (APSIM) suite of models was used to predict dynamics in water and nitrogen in soil, as well as the growth and yield of sequential crops of wheat and barley in pasture–wheat–barley rotations, between 19 at Roseworthy, South Australia.
We concluded that to bring accuracy in the simulation outcomes of models, new cultivars should be calibrated to minimize uncertainty to allow judicious recommendations in response to climate variability.An exploratory evaluation of APSIM to simulate growth and yield processes for winter cereals in rotation systems in South AustraliaĪnimal Production Science, 2004 44(8):787-800 Climate variability results depicted that an increase in temperature from 0 ☌ to 5 ☌ resulted in a 60% average decline in the yield of wheat cultivars while increased CO 2 increased yield similar to the combined effect of increased temperature and CO 2. Evaluation with the measured data showed that performance of both models was realistic as indicated by the accurate simulation of crop phenology, LAI, biomass and grain yield against measured data. The temporal changes in maximum LAI accumulation for all cultivars indicate that both measured and simulated values match each other. Both models were able to accurately simulate anthesis and maturity days, maximum leaf area index, biomass and grain yield, with normalized root mean square error (RMSE) less than 10%, D-index greater than 0.80 and model efficiency above 80% in most cases. APSIM-Wheat and CERES-Wheat were calibrated for all five wheat cultivars using genetic coefficients estimated based upon measured data during 2008–09 cropping year and validated with independent data sets (experimental data of 2009––11 cropping seasons) which were not used for models calibration. The experiments were laid out in Randomized Complete Block Design (RCBD) replicated four times with individual plot size of 5 m × 3 m.
Five wheat cultivars of diverse origin namely Tatara, NARC-2009, Sehar-2006, SKD-1 and F-Sarhad were planted on 19th November, at Islamabad during the years 2007–2011.
#APSIM WHEAT MANUAL#
We applied a manual method to calibrate APSIM-Wheat and CERES-Wheat for the flowering day, maturity day, leaf area index, biomass and grain yield of five spring wheat cultivars under rainfed conditions in Pakistan. Model calibration is necessary for application to new cultivars and environment. Crop growth in process based crop models is controlled by different parameters.
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