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How much Yield will you leave in the Field this harvest?

13 December 20197 min reading

“Researchers and agronomists have been aware of the significance of protein in developing VRF Nitrogen applications, however 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 Precision Agriculture Puzzle. By combining protein and yield with GPS coordinates, a complete picture of the nitrogen availability and uptake can now be achieved.”

Phillip Clancy CEO Next Instruments Sydney, Australia

GAP The term Yield Gap refers to the difference between the actual Yield and the potential Yield that can be achieved across a farm or field. Across the world, the Yield for wheat crops varies from approximately 2T/ha to 8.7T/ha. Australia has the lowest average Yield across the country where as Europe has the highest. Table 1 shows the data from the GRDC on the Yield and Yield Gap across eastern Australia. The table shows that Australian farms are producing around 50% of the wheat that is the potential to produce.

# of the 259 SLAs used in the national analysis 31 fall outside GRDC regions. Bridging the Yield Gap, Author: Zvi Hochman, David Gobbett, Heidi Horan, Di Prestwidge and Javier. Navarro Garcia, CSIRO Ecosystem Sciences | Date: 05 Mar 2014.

Water is a limiting factor in many regions of Australia. Farmers have no ability to affect the rainfall, where as they can take action where their fields are nutrient limited. Nitrogen, Phosphorus and Potassium are the key nutrients that can drive Yield. However Nitrogen is the major nutrient that directly increases Yield if applied correctly. Brill et al, 2012, have shown that Variable Rate Fertilization of Nitrogen can produce a positive Yield Response in zones where the Protein content of the grain is less than 11.5%. Figure 1 shows the affect of applying 0, 30, 60, 90 and 120kg/ha of Nitrogen in Australia wheat variety trials. Note that at 120kg/ha Nitrogen fertilization rate, the Yield reaches an otpimum of 4.1T/ha and the Protein content was 11.2%. Where as at lower rates of Nitrogen application, the Yield is lower and the Protein content is lower.

The CropScan 3300H On Combine NIR Analyser measures Protein in real time as the grain is stripped in the field. Measuring Protein and Yield of the grain across the field allows a new field map to be generated, ie, Protein/Yield Correlation Quadrant Map, figure 2. This map shows four performance zones which can show farmers where they can produce a positive Yield and Protein Response by selectively applying more Nitrogen fertilizer into the zones that are Nitrogen limited.

How much Nitrogen to apply? A farmer, Matt Hill, Esperance, WA, conducted strip trials to see how much Yield increased with the application of higher rates of Flexi N Nitrogen fertilizer. He applied 50, 100, 120 and 200 l/ha rates in the Red Zones of the adjacent field. The Red zone had previously produced Low Yield and Low Protein wheat, and thereby was projected to produce a positive Yield Response to increased Nitrogen fertilizer.

Grain yield (t/ha) and protein concentration (%) from 10 wheat varieties with 0, 30, 60, 90 and 120 kg/ha applied nitrogen in a trial at Parkes in 2011.(Brill et al, 2012, Comparison-of-grain-yield-and- grain-protein-concentration-of- commercial-wheat-varieties).

Table 2 shows the Yield and Protein Response to increases in the rate of Nitrogen applied across the field. Figure 3 is the plot of the Yield vs Nitrogen 6 Rate, which shows that approximatley 5 100 liters of Flexi N fertilizer produces an 4 additional 0.6T/ha and approimatley 1% 3 higher Protein.

Mr. Hill realised that he could have “gone harder” and increased the Nitrogen rate even further. With the cost of the Flexi N at $.69/l, then the return on investment can be shown in table 2.

How many Dollars are left in the Field? Based on the data collected by Mr Hill, the following chart provides a means of estimating the cost of under fertilizing and what additional income could have been achieved by using a CropScan 3300H On Combine Analyser to define the performance zones based on Protein and Yield.

Figure 2. Protein, Yield and Protein/Yield Correlation Maps for a Wheat Field in Young, NSW, 2016. Figure 2. Protein/Yield Correlation Maps, Wheat Field, Esperance, WA.

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 Nitrogen 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 greatest step forward to sustainability.

The CropScan 3300H provides the one piece of information that can resolve the two issues that have limited VRF implementation, 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 Protein 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 identifying 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 applying more Nitrogen. Using an approximate factor of 0.6 T/ha Yield Response per 100litres of Nitrogen per % Protein allows the farmer to compute how much Nitrogen should be applied to achieve the optimum Yield. Table 3 shows this simple computation.

THE OTHER BENEFIT OF USING THE PROTEIN/YIELD Correlation Quadrant Maps is that it makes implementation 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 water 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 zones 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 significance of Protein in developing VRF Nitrogen applications, however 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 Precision Agriculture Puzzle. By combining Protein and Yield with GPS coordinates, a complete picture of the Nitrogen Availability and Uptake can now be achieved.

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