Page 1 Page 2 Page 3 Page 4 Page 5 Page 6 Page 7 Page 8 Page 9 Page 10 Page 11 Page 12 Page 13 Page 14 Page 15 Page 16 Page 17 Page 18 Page 19 Page 20 Page 21 Page 22 Page 23 Page 24 Page 25 Page 26 Page 27 Page 28 Page 29 Page 30 Page 31 Page 32 Page 33 Page 34 Page 35 Page 36 Page 37 Page 38 Page 39 Page 40 Page 41 Page 4227 IREC Farmers' Newsletter No. 196 — Summer 2016 Recent changes to the NIR Tissue Test Some modifications have been made to the NIR Tissue Test in the last two seasons that will greatly increase its accuracy at predicting nitrogen uptake. The tissue test program converts the fresh weight measured by the grower into a dry weight, to allow the calculation of nitrogen uptake. It has been discovered that this conversion factor is not as accurate as we would like for current rice varieties, especially when drill sown, which has resulted in some of the reported PI nitrogen topdressing recommendations being lower than the actual crop requirement. This inaccuracy was partially modified last season and has been further refined for the coming season providing growers with more accurate topdressing recommendations. PI Predictor It can be very difficult to determine when a crop has reached PI. The only accurate method is to slice open some tillers and look for the furry tip (Figure 1). Rice Extension and NSW DPI have been busy fine-tuning the internet-based PI Predictor to help provide a guide to growers and agronomists on when their crop should reach PI. The PI Predictor requires the grower to enter the variety, sowing date, sowing method and location of their crop. The predictor then downloads up-to-date weather data from BoM (Bureau of Meteorology) to provide a reasonably accurate prediction of when PI will occur. It is important that the crop is still physically checked for PI as the PI Predictor is only a guide and some variability in the predicted PI date can occur. The PI Predictor is located at pipredictor.sunrice.com.au Satellite or aerial imagery Imagery is a very useful tool for showing the variability in crop growth across a field and enables targeted sampling to help account for the variability that is present. NDVI is the traditional imagery used by growers but research has shown it to have limited value at higher levels of crop growth. When nitrogen uptake at PI is above 80 to 90 kg N/ha, NDVI cannot determine any differences with the same NDVI value given regardless of the crop’s nitrogen uptake level (Figure 2). Research has shown that remote sensing imagery that includes the red-edge wavelengths (700 to 740 nm), i.e. NDRENDVI, does not have the same problem (Figure 3). At this time there are limited red-edge imagery options available but they should become increasing available in coming seasons. If growers have the opportunity to acquire a red-edge image instead of NDVI it is recommend they do so. Future direction Considerable research funded by RIRDC is being conducted on options for measuring PI nitrogen uptake with a reduced level of physical crop sampling or no sampling at all. All available remote sensing options are being evaluated to determine how accurately PI nitrogen uptake can be predicted. Depending on the level of accuracy achieved and the cost of the different options, modifications to the current sampling method to include remote sensing imagery and reduce the level of physical sampling will be incorporated into the NIR Tissue Test in future seasons. Further information Brian Dunn T: 02 6951 2621 E: [email protected] Figure 1. The crop is at panicle initiation once the furry tip (the developing panicle) is visible above the airspace and node in three out of ten main tillers. Figure 2. Measured PI nitrogen uptake (kg N/ha) compared with NDVI values collected using the micaSense RedEdge camera mounted on a drone. Figure 3. Measured PI nitrogen uptake (kg N/ha) compared with NRENDVI values collected using the micaSense RedEdge camera mounted on a drone. R² = 0.77 0.75 0.80 0.85 0.90 0.95 1.00 0 20 40 60 80 100 120 140 160 180 200 NDVI PI nitrogen uptake (kg N/ha) a) NDVI R² = 0.76 0.35 0.45 0.55 0.65 0.75 0.85 0 20 40 60 80 100 120 140 160 180 200 NRENDVI PI nitrogen uptake (kg N/ha) b) NRENDVI PI nitrogen uptake (kg N/ha) PI nitrogen uptake (kg N/ha) NDVI NRENDVI