Calibration and validation of optical chlorophyll‐measuring devices for use in predicting crude protein concentration in tropical grass herbage |
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| Authors: | M P Hughes C H O Lallo V Mlambo P G A Jennings |
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| Affiliation: | 1. Department of Food Production, Faculty of Food and Agriculture, University of the West Indies, St. Augustine, Trinidad and Tobago;2. Open Tropical Forage‐Animal Production Laboratory, Department of Food Production, Faculty of Food and Agriculture, University of the West Indies, St. Augustine, Trinidad and Tobago;3. Department of Animal Science, School of Agricultural Sciences, Faculty of Agriculture, Science and Technology, North‐West University, Mafikeng, South Africa;4. MARJEN Consulting Group, Spanish Town, Jamaica |
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| Abstract: | The objective of this experiment was to evaluate the Fieldscout CM 1000 NDVI and Yara N‐Tester as easy‐to‐use and cost‐effective tools for predicting foliar chlorophylls (a, b and total) and crude protein (CP) concentrations in herbage from three tropical grass species. Optical chlorophyll measurements were taken at three stages (4, 8 and 12 weeks) of regrowth maturity in Guinea grass (Panicum maximum) and Mulato II (Brachiaria hybrid) and at 6 and 12 weeks maturity in Paspalum spp (Paspalum atratum). Grass samples were harvested subsequent to optical measurements for laboratory analysis to determine CP and solvent‐extractable chlorophylls (a, b and total) concentrations. Optical chlorophyll measurements and CP concentrations were highly correlated (Yara N‐Tester: r2 = 0·77–0·89; Fieldscout CM 1000 NDVI: r2 = 0·52–0·84). Crude protein prediction models from the Yara N‐Tester and Fieldscout CM 1000 NDVI accounted for 70–89% and 44–73% CP variability, respectively, in Mulato II and Guinea grass. The Yara N‐tester produced more accurate and reliable CP estimates based on very high concordance correlation coefficient CCC (0·73–0·91)] and low rMSPE, mean and regression bias. It is concluded that the Yara N‐Tester produces more accurate and reliable CP estimates of tropical pastures. |
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| Keywords: | optical chlorophyll measurements tropical grass crude protein concentration solvent‐extractable chlorophyll |
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