Do Crop Rotations in Rice Reduce Weed and Echinochloa spp. Infestations? Recommendations for Integrated Weed Control

Gabriel Pardo,Ana Isabel Marí,Joaquín Aibar,Alicia Cirujeda

doi:10.3390/agronomy11030454

Abstract

The species belonging to the genus Echinochloa represent the main weeds in rice fields worldwide. Heavy soils are especially appropriate for this crop that is often grown in monoculture. A drought period in 2012 impeded farmers from sowing rice in some parts of the region of Aragon (northeastern Spain) and, unusually, they seeded alternative crops such as winter cereal, fescue (Festuca arundinacea), ryegrass (Lolium multiflorum) and lucerne (Medicago sativa). A total of 20 fields were selected, in which rice had been grown in monocrop until 2011 and several crop sequences were established afterwards; weed vegetation was recorded in spring, summer and autumn 2014-16 to find out if the crop rotations reduced weed infestations. Winter cereal and fescue were the crops with the highest soil cover; ryegrass and lucerne had difficulties in installation probably due to the heavy soil textures. Echinochloa spp. plants were found in the winter cereal stubble after having grown fescue for the previous two years and rice before that; in the forage fields, small plants of earing Echinochloa spp. adapted to mowing were detected. Recommendations for Integrated Weed Management that arise from the observations are ploughing the winter cereal stubble before seed shed of the emerged Echinochloa plants, assuring a high density of the forage crops, and efficient herbicide control in rice fields.

Highlights

IntroductionDespite decades of intensive herbicide use, lack of weed control is a serious problem in rice fields worldwide [1]
Biotypes of several Echinochloa species have developed herbicide resistance, and currently 35 different herbicide-resistant populations have been reported worldwide for Echinochloa crus-galli alone in rice [7], the first confirmed case being in Greece in 1989 [8]
The main conclusion of this work is that crop rotation alone is not sufficient to control Echinochloa spp. but needs to come along with detailed observation of the species’

Summary

Introduction

Despite decades of intensive herbicide use, lack of weed control is a serious problem in rice fields worldwide [1]. Flooding avoids the emergence of many species but others are perfectly adapted to inundation, the most difficult weeds in this crop being Echinochloa spp. and some Cyperaceae all over Europe [1,2], as well as in other parts of the world, e.g., in Arkansas and California in the USA [3,4], and in Asian countries such as Japan [5] and. Biotypes of several Echinochloa species have developed herbicide resistance, and currently 35 different herbicide-resistant populations have been reported worldwide for Echinochloa crus-galli alone in rice [7], the first confirmed case being in Greece in 1989 [8]. In Spain, resistance of several Echinochloa species has been reported [9] and control with alternative herbicides is irregular [10]

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