Emergency Periodicity and Seeds Bank of Weeds in Systems of Tillage and No Tillage

André Luiz De Souza Lacerda,Ricardo Filho Victoria,Cristiane Gonçalves De Mendonça

doi:10.11648/j.plant.20190703.15

Abstract

In Brazil there is lack of information about the weed emergency periodicity from the seed bank in the soil. This information is important to the elaboration of a strategy of weeds management. The objective of this research was to evaluate emergency periodicity of weeds by a frequent application of glyphosate used to determine the seeds bank in two systems of handling of the soil (tillage and no tillage). The experiment was conducted in the district of Piracicaba-SP, during two years, on the Dept. of Vegetable Production of ESALQ/USP. The experimental design was of completely randomized blocks with subdivided portions, repeated four times. The treatment consisted in glyphosate applications rates of 0, 540, 720, 900, 1080, 1260 and 1440 g.i.a ha<sup>-1</sup>. Weeds were sampled through the method of iron square and the seeds bank was determined by withdrawing of soil in depths of 0-2.5, 2.5-5.0, 5.0-10.0, 10.0-15.0 and 15.0-20.0cm. The herbicide glyphosate was shown effective in controlling weeds. In the year of 2001, they happened periodicitys of emergency more differentiated in the no tillage that in the tillage, but in the year of 2002, those differences of periodicitys in the species were not as expressive. The seeds concentrated layer superficial of the soil, in the no tillage system, while the tillage preparation in the soil distributed the seeds in the profile of soil.

Highlights

Weeds are characterized by producing lots of seeds when in a constantly disturbed environment that is due to the fact that only a small percentage germinates and survives completing its life cycle
In January 2001, plots were homogeneous because did not contain a significant variability of weeds and, there was a trend toward fewer weeds per m-2 in larger doses, there was no significant difference between the rates of glyphosate in two consecutive years when applied in the areas of conventional and direct system
Portions receiving no herbicide application had only made up weeding, showing that the herbicide was effective in controlling weeds even in lower doses

Summary

Introduction

Weeds are characterized by producing lots of seeds when in a constantly disturbed environment that is due to the fact that only a small percentage germinates and survives completing its life cycle. The seed bank is a reserve of viable seeds in soil, on the surface or at depth. This reserve is constituted as the initial stage of a reproductive life cycle for annual species, is the main cause for their persistence. In agricultural areas the seed bank in soil has been widely studied because of its importance. It is used to study the quantitative relations between the population of weeds and the infested flora. This kind of information allows to develop predictive indices and to formulate emergency models, making it possible to predict future infestations and how adequate soil management, measures and culture should be

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Conclusion