Floristic and phytosociology of weeds in pastures in Maranhão State, Northeast Brazil

Jaílson Penha Costa,Mário Luiz Ribeiro Mesquita

doi:10.5935/1806-6690.20160050

Abstract

Knowledge of weed floristic composition and phytosociology are key factors for improving weed management in pastures. Information on weed species that occur in pastures in Northeast Brazil, particularly in Maranhao State is very limited. It is, therefore, important, to search for information to help farmers to control weeds in livestock farming. This paper describes the weed flora diversity and community structure parameters, including density, frequency, abundance and importance value for each weed species found in five pastures of same age and management in Maranhao State, Northeast Brazil. The weed survey was carried out using a wooden frame (80 cm x 30 cm) placed randomly on the soil surface 30 times in each pasture (n = 150). Weeds were pulled out, separated by species and counted. The weed flora was represented by 996 individuals, from nine families, 15 genera and 19 species. Weed density within pastures was of 44.3 plants m -2 . The weed flora was dominated by species of the Cyperaceae and Poaceae families. The most important weed species based on Importance Value wereEragrostis ciliaris (IV = 32.97), Cyperus rotundus (IV = 31,95), Cyperus luzulae (IV = 27,50), Cyperus sphacelatus (IV = 27,42), Pycreus lanceolatus (IV = 27,33) Cyperus haspan (IV = 25,72) and Eleusine indica (IV = 23,49). Weed diversity, based on Shannon Diversity Index was very high (H' = 4.37 nats ind -1 ).

Highlights

IntroductionPasture degradation due to overgrazing, lack of management and consequent weed infestation is the main agronomic problem affecting livestock industry in northeastern Brazil, in Maranhão State (DIAS FILHO, 2005).According to Dias Filho (2011), pasture degradation is a complex phenomenon that involves causes and consequences which lead to gradual decrease of carrying capacity, such as inadequate grazing practices including the use of stocking rates or grazing intervals that do not take into account pasture rhythms of growth; inadequate pasture management practices like the absence of periodic soil fertility replenishment and the excessive use of fire to eliminate not consumed pasture, to provoke grass re-sprouting or to control weeds; failures in pasture establishment due to inadequate seedbed preparation, use of low quality seeds, wrong date of planting or by the fact that the first grazing is held too early or too late; biotic factors such as pests or pathogens and abiotic factors such as the excess of or lack of rainfall and poor soil drainage capacity.Weeds interfere in livestock production by mechanisms of competition with forage species by water, nutrients, space and light and by allelopathy, that is, the production of phytotoxins that prohibits or suppress growth of forage species (REIGOSA et al, 2013).Weed infestations impact livestock farming by lowering yield and quality of forage, increasing costs of managing, slowing animal weight gain, reducing livestock products quality like meat and milk, and eventually poisoning livestock, because many weed species that occur in pastures are toxic, such as Palicourea marcgravii A
Weeds interfere in livestock production by mechanisms of competition with forage species by water, nutrients, space and light and by allelopathy, that is, the production of phytotoxins that prohibits or suppress growth of forage species (REIGOSA et al, 2013)
Weed infestations impact livestock farming by lowering yield and quality of forage, increasing costs of managing, slowing animal weight gain, reducing livestock products quality like meat and milk, and eventually poisoning livestock, because many weed species that occur in pastures are toxic, such as Palicourea marcgravii A

Summary

Introduction

Pasture degradation due to overgrazing, lack of management and consequent weed infestation is the main agronomic problem affecting livestock industry in northeastern Brazil, in Maranhão State (DIAS FILHO, 2005).According to Dias Filho (2011), pasture degradation is a complex phenomenon that involves causes and consequences which lead to gradual decrease of carrying capacity, such as inadequate grazing practices including the use of stocking rates or grazing intervals that do not take into account pasture rhythms of growth; inadequate pasture management practices like the absence of periodic soil fertility replenishment and the excessive use of fire to eliminate not consumed pasture, to provoke grass re-sprouting or to control weeds; failures in pasture establishment due to inadequate seedbed preparation, use of low quality seeds, wrong date of planting or by the fact that the first grazing is held too early or too late; biotic factors such as pests or pathogens and abiotic factors such as the excess of or lack of rainfall and poor soil drainage capacity.Weeds interfere in livestock production by mechanisms of competition with forage species by water, nutrients, space and light and by allelopathy, that is, the production of phytotoxins that prohibits or suppress growth of forage species (REIGOSA et al, 2013).Weed infestations impact livestock farming by lowering yield and quality of forage, increasing costs of managing, slowing animal weight gain, reducing livestock products quality like meat and milk, and eventually poisoning livestock, because many weed species that occur in pastures are toxic, such as Palicourea marcgravii A. Pasture degradation due to overgrazing, lack of management and consequent weed infestation is the main agronomic problem affecting livestock industry in northeastern Brazil, in Maranhão State (DIAS FILHO, 2005). According to Dias Filho (2011), pasture degradation is a complex phenomenon that involves causes and consequences which lead to gradual decrease of carrying capacity, such as inadequate grazing practices including the use of stocking rates or grazing intervals that do not take into account pasture rhythms of growth; inadequate pasture management practices like the absence of periodic soil fertility replenishment and the excessive use of fire to eliminate not consumed pasture, to provoke grass re-sprouting or to control weeds; failures in pasture establishment due to inadequate seedbed preparation, use of low quality seeds, wrong date of planting or by the fact that the first grazing is held too early or too late; biotic factors such as pests or pathogens and abiotic factors such as the excess of or lack of rainfall and poor soil drainage capacity.

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