Morphological adaptations of signal grass in response to liming and cutting severities

Lilian Elgalise Techio Pereira,Valdo Rodrigues Herling,Junior Cesar Avanzi,Bruna Scalia De Araújo Passos,Pedro Henrique De Cerqueira Luz

doi:10.5935/1806-6690.20180076

Abstract

Changes in morphological composition and in the plant population were evaluated during late spring, summer and autumn, in swards of Brachiaria decumbens cv. Basilisk in response to liming (C0.0, without liming; C0.7, limestone amount equivalent to 0.7 ton ha-1; and C1.0, limestone amount equivalent to 1.0 ton ha-1), which were subjected to severe or lenient cutting (40 or 60% of the pre-cutting height, respectively). Increased limestone doses did not result in higher herbage mass (HM), leaf area index (LAI) or proportion of leaves (%L) in the pre-harvest. However, lower proportion of dead material was registered in C0.7 treatment. The treatments C0.0 e C0.7 had higher %L during late spring and summer when associated to severe cutting regimes (R40%), although they reached the pre-harvest condition with lower HM and longer regrowth periods compared to lenient cuttings. The Brachiaria decumbens cv. Basilisk modifies its shoot architecture during the growth season, indicating that lower pre-harvest heights are required during autumn. The absence of liming led to a sharp decreasing of base saturation and levels of K, Ca and Mg in the soil. The minimum annual amount of limestone required for B. decumbens correspond to 0.7 ton ha-1.

Highlights

Pasture-based livestock systems in Brazil are traditionally stablished on low fertility soils, which are subjected to a minimal frequency of nutrient replacement through fertilization or control of their acidity levels, and unsatisfactory grazing management techniques (VOLPE et al, 2008)
The average canopy heights of swards maintained under severe (R40%) and lenient (R60%) cuttings were, respectively, 14.4 and 19.4 ± 0.52 cm during late spring, 14.9 and 20.0 ± 1.08 cm during summer, and 14.9 and 20.0 ± 1.08 cm in the autumn
The residual herbage mass (HM), morphological composition and the remaining leaf area index (LAI) in this stage are dependent upon the targets for management imposed, the severity of cutting (SC), and affects how fast is the recovering of the surface leaf area (PEREIRA et al, 2014)

Summary

Introduction

Pasture-based livestock systems in Brazil are traditionally stablished on low fertility soils, which are subjected to a minimal frequency of nutrient replacement through fertilization or control of their acidity levels, and unsatisfactory grazing management techniques (VOLPE et al, 2008). Liming is an essential agronomic practice for pH correction and neutralization of toxic aluminum, promoting benefits to chemical, physical and biological soil properties, and contributing to the maintenance of productivity and persistency of pastures (BARCELOS et al, 2011). Basilisk is prominent among the perennial tropical grasses as it is considered tolerant to soil acidity (PEDREIRA; SILVA; ALONSO, 2015). It has high resistance to grazing, being able to provide an adequate vegetation cover and satisfactory dry matter yield even under poor soil fertility, a condition considered restrictive for growing and persistency of other plant species of the same genus (VALLE et al, 2010). Despite being introduced in Brazil in 1968 and commonly used as pasture, its plasticity for adjustments in tiller population density and morphological traits in response to liming remain largely unknown, when severe cuttings are adopted (PEDREIRA; BRAGA; PORTELA, 2017)

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