Bahiagrass (Paspalum notatum CV. Inia Sepé) responses to defoliation intensities

Defoliation management is determinant of forage production and plant persistence. The objective of this study was to identify grazing suitability and stability of herbage production of INIA Sepé subjected to four intensities of defoliation (represented for sward canopies of 3, 10, 17 and 24 cm maintained constant through weekly cuts) and two rates of nitrogen fertilization (100 and 300 kg ha⁻¹). The response variables studied were: botanical/morphological composition of the herbage mass, herbage accumulation, nutritive value, tiller population density (TPD), tiller weight (TW), leaf area index (LAI) and nitrogen nutrition index (NNI) and calculations performed relative to the tiller size × density compensation mechanism (SDC). Taller swards had smaller population of large tillers, with greater individual leaf area, showing a tiller × size density compensation response. Calculations indicated that the regression coefficient for the linear regression between TW and TPD in a log scale was close to −2.5, in agreement with the −5/2 self-thinning rule, with variable LAI and R (ratio between tiller leaf area and volume). The exception was during year 1 for the 100 kg N ha⁻¹, when the regression coefficient was close to −1.5. During year 2 only one replication of the 3 cm and 100 kg N ha⁻¹ did not follow the SDC line. LAI and herbage accumulation were positively correlated with the distance between points of log(TW) × log(TPD) and an hypothetical −3/2 SDC line (p < .0001). Paspalum notatum cv. INIA Sepé shows stability of herbage accumulation and ability to adjust tiller size and population density.