Effect of botanical composition calibration on the accuracy of undisturbed sward height and comparative yield method techniques for herbage mass estimation in tropical heterogeneous pastures

Abstract

This study aimed to evaluate the influence of botanical composition calibration on the accuracy of undisturbed sward height and  comparative yield method (CYM) techniques for herbage mass estimation in tropical heterogeneous pastures. Two studies were  conducted using two grazing systems based on heterogeneous pastures. Herbage mass was estimated using CYM and undisturbed  sward height techniques within quadrats (SHQ) or at a set of standard points in the paddocks (SHP). SHQ had a higher adjusted R2 when  calibrated with the Urochloa brizantha cv. Marandú (U. brizantha) proportion compared to the simple SHQ model (0.75 vs 0.68), while RSE  was lower (0.18 vs 0.21). The R2 increased (0.63 to 0.68), while both residual means and RSE decreased (−2.30 to –0.05 and 0.22 to  0.20, respectively) when SHP was calibrated with U. brizantha. It also resulted in a reduction of mean squared prediction error (MSPE) to  CYM, SHQ, and SHP, respectively. The CYM allows for higher accuracy of herbage mass estimation in tropical heterogeneous pastures  than undisturbed sward height, irrespective of botanical calibration. However, the botanical composition calibration had positive effects  on the models from undisturbed sward height, and the calibration with U. brizantha increased the accuracy of herbage mass prediction.