The goal of this study was to evaluate the effects of thinning eucalyptus trees on yield and nutritive value of corn for silage and palisadegrass in a crop–livestock–forest integrated system and to evaluate the total aboveground biomass yield in systems with and without trees. Plant variables, as well as the incidence of photosynthetically active radiation (PAR) and soil moisture, were evaluated between October 2016 and March 2018 in São Carlos, Brazil, in a crop–livestock–forest and a crop–livestock system. In the crop–livestock–forest system, eucalyptus trees (Eucalyptus urograndis clone GG100) were planted in April 2011, in single rows, with 15 × 2 m spacing. In 2016, the trees were thinned, and the spacing was changed to 15 × 4 m. The treatments comprised measurements at 0.00, 3.75, 7.50, and 11.25 m from the trees of the North row in the integrated crop–livestock–forest (iCLF) system and integrated crop–livestock (iCL) system. Palisadegrass (Urochloa brizantha) was sown after harvesting the corn. Corn yields were similar between treatments, with an average of 13.6 Mg ha−1. Corn for silage presented a higher percentage of grain in total biomass in the crop–livestock–forest positions (41.4 and 42.1%) than in the crop–livestock system (35.6%). No differences in forage accumulation were observed. Crude protein content in corn for silage and palisadegrass was higher in the crop–livestock–forest treatments than in the crop–livestock system. Such results indicate that thinning was favorable to production in the crop–livestock–forest system. Total aboveground biomass yield was higher in the iCLF system, indicating better land use for this type of integrated system.

In intensive livestock production systems, estimating forage production and its nutritive value can assist farmers in optimizing pasture management, stocking rate, and feed supplementation to animals. In this study, we aimed to use vegetation indices, determined using a proximal canopy reflectance sensor, to estimate the forage mass, crude protein content, and nitrogen in live forage of Marandu palisadegrass (Urochloa brizantha). Pasture canopy reflectance was measured at three wavelengths (670, 720, and 760 nm) using a Crop Circle device equipped with an ACS-430 sensor. Total forage mass, plant-part composition, leaf area index (LAI), and crude protein content were assessed during 14 growth cycles in a pasture under four management regimes, comprising different combinations of two N fertilization rates and two irrigation schedules. For each forage assessment, pasture canopy reflectance data were used to calculate the following vegetation indices: normalized difference vegetation index, normalized difference red edge, simple ratio index (SRI), modified simple ratio, and chlorophyll index. In addition, we also performed analyses of the linear and exponential regressions between vegetation indices and total forage mass, leaf + stem mass, leaf mass, LAI, crude protein content, and nitrogen in live forage. The best estimates were achieved for total forage mass, leaf + stem mass, leaf mass, and nitrogen in live forage using SRI (R2 values between 0.72 and 0.79). When estimating pasture productive variables (total forage mass, leaf + stem mass, leaf mass, and LAI) from SRI, the equations showed R2 values between 0.69 (leaf mass) and 0.74 (LAI) and relative errors ranging from 19% to 21%. For each of the water and nitrogen supply conditions evaluated, this index facilitated the monitoring of forage mass time series and nitrogen in live forage and the extraction of this nutrient by the pasture.