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Relationships between N, P, K, Ca, Mg, Fe and K/(Ca+Mg) ratio, ADF, NDF and chlorophyll contents of orchard grass (Dactylis glomerata L.) and spectral reflectance were determined. Visible near-infrared reflectance spectroradiometer (VNIR) was used to predict the nutrient contents of the orchard grass under different N (0, 40, 80, 120 and 160 kg/ha) fertilization. Increase in N fertilization decreased spectral reflectance at both angles of 10 degree and plant probe. Orchard grass nutrient contents had high correlation with spectral reflectance. In the angle of 10 degree, the r(2) of predicted and measured N, P, K, Ca, Mg, Fe and K/(Ca+Mg) ratio, ADF, NDF and chlorophylls were low (0.57, 075, 0.73, 0.50, 0.58, 0.71, 0.41, 0.92, 0.84 and 0.77, respectively). On the other hand in plant probe, N, P, K, Ca, Mg, Fe and K/(Ca+Mg) ratio, ADF, NDF and chlorophylls were high (0.86, 0.85, 0.97, 0.72, 0.79, 0.77, 0.58, 0.94, 0.86 and 0.92, respectively). It is revealed that spectral reflectance in VNIR can be used for non-destructive prediction of forage N, P, K, Ca, Mg, Fe and K/(Ca+Mg) ratio, ADF, NDF and chlorophyll content in orchard grass under different nitrogen fertilizations. |
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