Assessment of Piatã palisadegrass forage mass in integrated livestock production systems using a proximal canopy reflectance sensor

Abstract

Abstract Estimates of forage mass can help in decision making for pasture management and stocking rate adjustment in pastoral systems. This study aimed to estimate Piata palisadegrass forage mass under full sun and shaded livestock production systems using vegetation indexes obtained with a proximal canopy reflectance sensor. Pasture canopy reflectance was measured at three fractions of the radiation spectrum (670, 720, and 760 nm). Total forage mass, morphological composition, and leaf area index (LAI) were assessed at the same time as reflectance in all production systems. Reflectance data were used to calculate vegetation indexes (normalized difference vegetation index – NDVI, normalized difference red edge – NDVI_RE, simple ratio index – SRI, modified simple ratio – MSR, and chlorophyll index) for each assessment. Linear and exponential regression analyses between vegetation indexes and total forage mass, leaf + stem mass, leaf mass, and LAI were performed. The equations generated by these analyses were used to estimate such pasture variables. The best estimates of leaf + stem mass, leaf mass, and LAI were obtained using SRI (R2 between 0.55 and 0.84) for the full sun systems, MSR (R2 from 0.67 to 0.93) for the shaded systems, and NDVI (R2 between 0.65 and 0.91) when all systems were analyzed together. These pasture variables can be estimated by general equations developed for both full sun and shaded livestock production systems. However, total forage mass estimates were less efficient (R2 of 0.03–0.53), due to differences in canopy structure and senescent material content between production systems.