Miller Magazine Issue: 120 December 2019

76 ARTICLE MILLER / DECEMBER 2019 Discussion: Variable Rate Nitrogen Fertilization has been an option for farmers for 20 years, yet so few farmers are actually using VRF to increase their incomes. It has been suggested that VRF is too hard to implement or that applying more Nit- rogen does not always produce positive Yield Responses. However the Yield Gap is a reality in Australian grain farming and a solution for closing the Yield Gap offers the industry the grea- test step forward to sustainability. The CropScan 3300H provides the one piece of information that can resolve the two issues that have limited VRF imp- lementation, i.e., a method of measuring Nitrogen Availability and Uptake across the fields. Protein is directly related to Nitrogen by a factor of 0.175. For every kilogram of Protein in a tonne of grain, 175 grams of Nitrogen is stripped from the soil. By combining Pro- tein and Yield data off the combine, Protein/Yield Correlation Quadrant Maps can be generated that clearly shows how much and where Nitrogen was stripped from the soil. Approximately 30% of all grain fields across Australia under perform in terms Yield and Protein. By identif- ying those zones in a field where the Protein is less than 11.5% and the Yield is average or less than average, then a positive Yield Response can be achieved by app- lying more Nitrogen. Using an approximate factor of 0.6 T/ha Yield Response per 100litres of Nitrogen per % Pro- tein allows the farmer to compute how much Nitrogen should be applied to achieve the optimum Yield. Table 4 shows this simple computation. THE OTHER BENEFIT OF USING THE PROTEIN/YIELD Correlation Quadrant Maps is that it makes implemen- tation of VRF simple. The four performance zones; Green, Blue, Red and Yellow, show how the plants have accessed and taken up Nitrogen from the soil. The Green zones are the Sweet Spots in the field where the plants have achieved their full Yield Potential. The Blue Zones are most likely wa- ter limited. The Red and Yellow zones are where the plants were Nitrogen limited at some stages in the growth cycle. AS SUCH, A VRF PRESCRIPTION CAN BE DEVELOPED WHERE the rate of Nitrogen fertilizer is held constant in the Green zones and increased in the Red and Yellow zones. These zo- nes are where the low lying fruit can be gathered and a positive Yield Response can be achieved. The implementation of VRF becomes very simple and will ensure positive results. The Blue zones are where there are other factors affecting the plants growth. Further investigation may be required, i.e. soil pits, to understand what is limiting the plants growth in these zones. Conclusion: Researchers and agronomists have been aware of the sig- nificance of Protein in developing VRF Nitrogen applications, howe- ver there has not been available an instruments to measure the seed Protein and therefore the Nitrogen Availability and Uptake across the field. The CropScan 3300H On Combine NIR Analyser is the Missing Piece of the Preci- sion Agriculture Puzzle. By com- bining Protein and Yield with GPS coordinates, a complete picture of the Nitrogen Availability and Uptake can now be achieved. Protein (%) Applied Flexi N (l/ Ha) Yield (t/Ha) Flexi N Cost $ Payment $/ha Additional Profit $/ha 8.3 0 3.7 0 1184 0 8.7 50 4.1 34.5 1312 94 9.1 100 4.4 69 1408 155 9.6 120 4.8 82.8 1536 269 10.1 200 5 82.8 1600 278 10.6 250 5.3 172.5 1696 340 11.1 300 5.6 207 1792 401 11.6 350 5.8 241.5 1856 431 Table 2. Yellow represents actual field data. Green represents extrapolated data. Dollars Left in the Field per ha Payment $/ha Additional Profit $/ha Protein % Yield 3.5 T/ha Yield 4.0 T/ha Yield 4.5T/ha Yield 5.0T/ha Yield 5.5 T/ha Yield 6.0T/ha Yield 6.5 T/ha 8.5 -$330 -$275 -$220 -$165 -$110 -$55 $0 9 -$275 -$220 -$165 -$110 -$55 $0 $0 9.5 -$220 -$165 -$110 -$55 $0 $0 $0 10 -$195 -$130 -$65 $0 $0 $0 $0 10.5 -$130 -$55 $0 $0 $0 $0 $0 11 -$65 $0 $0 $0 $0 $0 $0 11.5 $0 $0 $0 $0 $0 $0 $0 Table 3. The Cost of Lost Yield as a result of under fertilization.