Seed longevity of Eragrostis plana Nees buried in natural grassland soil

Renato Borges De Medeiros,Leandro Luiz Menegon,Telmo Focht,Mário Ruschel Freitas

doi:10.1590/s1516-35982014001100001

Renato Borges De Medeiros, Leandro Luiz Menegon + Show 2 more

Open Access

https://doi.org/10.1590/s1516-35982014001100001

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Abstract

The objective of this research was to evaluate the seed longevity of Eragrostis plana Nees buried at different soil depths, in a natural-grassland area in the Pampa biome (46 m altitude, 30o05´S and 51o40´W) of Rio Grande do Sul State, Brazil. The experimental design was a split-plot type in complete blocks with two factors: seeds buried at five different depth levels (soil surface and 2.5, 5, 10 and 20 cm) and seven exhumation dates. The blocks were allocated in natural grassland grazed by cattle, allocated in a 12-m-long transection. Fifty-four permeable nylon bags filled with 100 seeds in each division, with five vertical divisions, were buried in each row. Seven exhumation dates were used: the first on October 14, 2003 and the last on January 14, 2006. The percentage of viable seeds of E. plana, collected at seven exhumation times and set at different depths in the soil horizon, were described by simple negative exponential equations. Based on the model, the percentage of viable seeds collected at the five depths, (soil surface and 2.5, 5, 10, and 20 cm), after 2.5 years of burial, were 0.1, 0.5, 1.0, 7.4 and 22.1%, respectively. Increase in depth is directly associated with physical and physiological seed integrity of E. plana. Negative simple exponential equations can be used to predict seed longevity of E. plana buried in nylon bags. This invader species accumulates soil seed-bank of high longevity.

Highlights

Native pasture is the main diet of sheep and cattle in Rio Grande do Sul State, Brazil
The objective of this research was to evaluate the seed longevity of Eragrostis plana Nees buried at different soil depths, in a natural-grassland area in the Pampa biome (46 m altitude, 30o05 ́S and 51o40 ́W) of Rio Grande do Sul State, Brazil
The exhumation of the seeds placed on the soil surface dropped to 61.3%, while those exhumed at 20 cm depth presented 90.7%, which resulted in 29.4% of amplitude between them

Summary

Introduction

Native pasture is the main diet of sheep and cattle in Rio Grande do Sul State, Brazil. In spite of its economic and environmental importance, this natural resource is losing its quality as forage due to the continuous invasion and expansion of Eragrostis plana. This invasion has determined drastic reduction in frequency and abundance of native species and losses in the animal productivity (Medeiros et al, 2009). Its expansion results from the ingestive behavior of animals under continuous grazing, in which, in the best growing pasture period (spring), they prefer to ingest the native prostrate species with higher nutritional value rather than the E. plana tussock (Medeiros et al, 2009). Another seed fraction is ingested by the animals and distributed locally by the feces or, in the case of animal transport, invades areas in other regions through the preserved seeds, which are viable for up to three days in the feces after ingestion (Medeiros et al, 2009)

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