VEGETATIVE DEVELOPMENT AND GROWING DEGREE-DAYS OF TROPICAL AND WINTER FORAGES

Arthur C Sanches,Eder P Gomes,Fernando C Mendonça,Débora P De Souza,Fernanda L F De Jesus

doi:10.1590/1809-4430-eng.agric.v39n2p191-197/2019

Abstract

ABSTRACT One of the limitations to producing irrigated forages is setting suitable biometric parameters to establish the entrance of animals to grazing areas. Such parameters can be measured or even estimated. Estimates are advantageous for being practical and able to be used for grazing optimization. This study aimed to evaluate the correlation among growing degree-days (GDD), canopy height (CH), leaf area index (LAI), and number of cycle days (NCD) of Guinea grass (Panicum maximum cv. Mombaca) and Bermuda grass (Cynodon spp. Tifton 85) single cropped for one year and overseeded with black oat and ryegrass in the autumn-winter season. The study was carried out from February 2016 to February 2017, and forage crops were sprinkle irrigated. LAI and CH were measured twice a week, at intervals of 3 and 4 days. These parameters were correlated to GDD accumulation at each cutting cycle (CC). All the correlations showed high coefficients in linear fits. For spring-summer cycles, Guinea grass in exclusive cultivation showed the highest averages for CH and LAI, being 102.3 cm and 5.93, respectively. For autumn- winter cycles, when this grass was overseeded, it showed an LAI value similar to that when single cropped, which was of about 5.6. Yet single Bermuda grass presented lower values of LAI (one unit lower) and CH (16.4 cm lower) in the autumn-winter season when compared to that overseeded. The spring-summer cycles of Guinea grass had a duration of 24 days, after which no increase in leaf production was registered.

Highlights

At the end of the eighteenth century, beef and leather became important export products in Brazil
The test was used for different variances of both ‘Mombaça’ and Cynodon spp., in almost all the periods in which leaf area index (LAI) was involved
The correlations found in this study among canopy height (CH), leaf area index (LAI), and growing degreedays (GDD) enabled the development of empirical models, with applicable linear regression adjustments and high coefficients of correlation for all treatments

Summary

Introduction

At the end of the eighteenth century, beef and leather became important export products in Brazil. The international scenario again becomes favorable to the Brazilian livestock sector with the entry of new consumers, namely Russia and China. Pasture growth is influenced by seasonal weather patterns, mainly solar radiation and temperature (Vogeler et al, 2016). In tropical countries such as Brazil, the high temperatures favor forage growth and, when properly managed, high yields have been achieved (Pezzopane et al, 2012; Gomes et al, 2015b; Andrade et al, 2016; Antoniel et al, 2016; Martuscello et al, 2016; Sanches et al, 2016)

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