Herbage accumulation, morphological composition, and nutritive value of Paspalum notatum CV. INIA Sepé

D Giorello ,André Fischer Sbrissia,S Da Silva

doi:10.31285/agro.25.348

Abstract

Defoliation strategies determine sward canopy structure and affect forage accumulation and nutritive value. The objective of this study was to determine forage accumulation, morphological composition and nutritive value of inia Sepé subjected to combinations of three frequencies (defoliation at 90%, 95% and maximum canopy light interception during regrowth —li90%, li95% and liMax), and two severities of defoliation (40 and 60% of the pre-cutting height). The experiment was carried out from November 15th, 2018 to March 31st, 2019 in Tacuarembó. Measurements of li and canopy height, forage mass morphological composition and nutritional value were carried out. Forage mass was greater in Feb-March. The percentage of leaves was greater for the higher defoliation frequency treatment (li90%). The percentage of stems did not vary among treatments (average of 23%). The percentage of dead material was greater for the lower defoliation frequency treatment (liMax) and 40% defoliation severity. Greater adf and ndf values and smaller digestibility were recorded for liMax/40% combination. For li90%, greater adf and ndf, and smaller digestibility were recorded for the 60% defoliation severity (Feb-March). Forage accumulation was greater for li90% and li95%. inia Sepé shows large flexibility to defoliation management, and the optimal pre-cutting target should not exceed li95% (i.e. 30 cm of canopy height) in order to ensure production of high nutritive value forage and harvest efficiency.

Highlights

Paspalum notatum is a summer perennial grass, type C4, and one of the most common species in Uruguay's natural grassland
To harvest better nutritive value forage at the expense of a possible loss of forage accumulation, studies were carried out evaluating targets of light interception during regrowth (LI) lower than critical LAI (90% vs 95% LI)(12), which indicated a decrease in forage and leaf accumulation in the growth process
Parsons and others[13] demonstrated that the lower the residual LAI was, the longer the regrowth period had to be before reaching the maximum forage accumulation rate, which was unlikely to vary in an extensive range of defoliation regimes

Summary

Introduction

Paspalum notatum is a summer perennial grass, type C4, and one of the most common species in Uruguay's natural grassland. Parsons and Penning[6] demonstrated that interruption of regrowth at the critical LAI results in maximum forage accumulation rate for perennial ryegrass, a condition in which the balance between growth and senescence processes would be maximum. To harvest better nutritive value forage at the expense of a possible loss of forage accumulation, studies were carried out evaluating targets of LI lower than critical LAI (90% vs 95% LI)(12), which indicated a decrease in forage and leaf accumulation in the growth process. Despite using the pre-set canopy height as a management criterion for temperate and tropical pastures, the use of flexible post-grazing (cutting) heights is more recent, mainly in tropical pastures, where most studies were carried out with fixed heights, generating variable defoliation severities that hinder the definition of a single goal for different forage crops. The soil of the experimental site is a Typic Eutric Vertisol (Hapluderts Typic), belonging to the Soil

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