Proximal fluorescence sensing of potassium responsive crops to develop improved predictions of biomass, yield and grain quality of wheat and barley
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Precision nutrient management requires accurate assessment of crop nutrient status. This is common for assessing N status, but much less so for other nutrients. Because fluorescence can indicate crop stress, the robustness of different fluorescence indices was assessed to predict crop nutrient status (K, Mg and Ca). The hypothesis was that crop nutrition limitations, especially K, can be detected using fluorescence proximal sensing to quantify crop response with a high degree of spatial resolution. A factorial experiment was imposed with four treatment factors: crop, K fertilizer rate, lime and row management. The soil at the experimental site was K deficient and the crop variables showed significant treatment effects (e.g. yield, protein). Fluorescence sensing identified a significant positive K response for three chlorophyll related indices (SFR_G, SFR_R and CHL), but not for FLAV; while wheat was significantly different from barley. Using a k-fold cross-validation method promising predictive relationships were found. The strongest predictions were for SFR_R to predict crop biomass, for SFR_G to predict crop K content of inter-row wheat, for CHL to predict crop Ca content of inter-row wheat and for FLAV with barley grain protein in the windrow treatment. The fluorescence indices produced more significant crop variable predictions than measuring NDVI using an active sensor. This study illustrates the utility of fluorescence sensing to measure chlorophyll related signals for capturing the nutritional status of barley and wheat crops. These results show encouraging potential to rapidly detect crop nutrient status for non-N nutrients using fluorescence sensing.
KeywordsFluorescence indices Chlorophyll Grain quality prediction Wheat Barley Biomass
The authors are very grateful to the farmer Mr. Rob Veale for providing access to and use of his field to conduct these experiments. Corrine Celestina and Megan Beveridge (Southern Farming Systems) undertook important tasks at sowing, harvest and general crop management. We also must thank Mr. Ed Hilsdon (Landmark) for his constant support and helpful agronomic advice. Financial support for this work was provided through a grant from the Grains Research and Development Corporation, Australia and with significant in-kind support from the NSW Department of Primary Industries (NSW DPI). In addition, we acknowledge the encouragement of Dr. Rob Norton and the financial support received from the International Plant Nutrition Institute (IPNI).
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