Miller Magazine Issue: 120 December 2019

75 ARTICLE MILLER / DECEMBER 2019 # of the 259 SLAs used in the na- tional analysis 31 fall outside GRDC regions. Bridging the Yield Gap, Au- thor: Zvi Hochman, David Gobbett, Heidi Horan, Di Prestwidge and Javi- er. Navarro Garcia, CSIRO Ecosystem Sciences | Date: 05 Mar 2014. Water is a limiting factor in many re- gions of Australia. Farmers have no ability to affect the rainfall, where as they can take action where their fields are nutri- ent limited. Nitrogen, Phosphorus and Potassium are the key nutrients that can drive Yield. However Nitrogen is the ma- jor 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 fertiliza- tion 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. Measur- ing 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 posi- tive Yield and Protein Response by selec- tively applying more Nitrogen fertilizer into the zones that are Nitrogen limited. How much Nitrogen to apply? A farmer, Matt Hill, Esperance, WA, con- ducted strip trials to see how much Yield increased with the application of higher rates of Flexi N Nitrogen fertilizer. He ap- plied 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. Table 2 shows the Yield and Protein Response to increases in the rate of Nitrogen applied across the field. Fig- ure 3 is the plot of the Yield vs Nitro- gen 6 Rate, which shows that approx- imatley 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 Nitro- gen 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 Com- bine Analyser to define the performance zones based on Protein and Yield. 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, Compari- son-of-grain-yield-and- grain-protein-concentrati- on-of- commercial-wheat-varieties). 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.