ABSTRACT.
Prediction of Brachiaria decumbens forage biomass using structural characteristics

Jefte A. de A. Conrado1*, Marcos N. Lopes2, Magno J.D. Cândido1, Vitor H.M. Macedo3, Valdson J. da Silva4, and Vitória G. Damasceno1
 
Tools that generate models with good biomass predictive capacity are essential to maintain thes ustainability of productions ystems. The objective was to analyze the relationship between forage biomass and structural variables and generate models to predict total forage biomass (TFB) and green leaf blade biomass (GLB). Irrigated pastures of Brachiaria decumbens Stapf 'Basilisk' were kept under rotational stocking with sheep (Ovis aries L.) The TFB, GLB, leaf area index (LAI), height (cm), and normalized difference vegetation index (NDVI) were evaluated. The experimental design was completely randomized with four replicates: ten and five cycles of defoliation management, respectively, were used togenerate and validate the stages of the models. The best goodness of fit was obtained by nonlinear models for both TFB and GLB, which can be confirmed by high Spearman's correlations and significance (P < 0.0001). The path analysis showed low collinearity (42.60) between NDVI, LAI, and height; the high determination coefficient (R2) with values of 0.8421 and 0.7767 demonstrated their associations with TFB and GLB, respectively. Among the studied models to predict TFB and GLB, only exponentials using NDVI and power using LAI and height showed the best fit. In the validation stage, the models related to heigh texhibitedt hehighest performance with 0.9531 (TFB) and 0.9638 (GLB) d-index, -2.3(TFB) and -7.20 (GLB) bias, and 0.8532 (TFB) and 0.8932 (GLB) R2. Only nonlinear models using height (cm) to predict TFB and GLB had the best practical application potential, thus ensuring efficiency in data collection.
Keywords: Brachiaria decumbens, height, leaf area index, NDVI.
1Universidade Federal do Ceará, Departamento de Zootecnia, Av. Mister Hull, 2977, Campus do Pici, CEP: 60356-000, Fortaleza, Ceará, Brasil.*Corresponding author (jefte_arnon@hotmail.com).
2Instituto Federal do Piauí, Campus Valença do Piauí, Av. Joaquim Manoel, s/n, Centro, Valença do Piauí, CEP: 64300-00, Valença do Piauí, Piauí, Brasil.
3Universidade Federal Rural da Amazônia, Av. Perimetral, 2501, CEP: 66077830, Belém, Para, Brasil.
4Universidade Federal Rural de Pernambuco, Av. Dom Manoel de Medeiros, s/n, Dois irmãos, CEP:62040370, Recife, Pernambuco, Brasil.