Effect of Barley Sowing Density on the Integrated Weed Management of Lolium rigidum (Annual Ryegrass) in Mediterranean Dryland: A Modeling Approach

María Belén D’Amico,José L González-Andújar,Guillermo R Chantre,Guillermo L Calandrini

doi:10.3390/agronomy11081565

Abstract

Population models are particularly helpful for understanding long-term changes in the weed dynamics associated with integrated weed management (IWM) strategies. IWM practices for controlling L. rigidum are of high importance, mainly due to its widespread resistance that precludes chemical control as a single management method. The objective of this contribution is to simulate different IWM scenarios with special emphasis on the impact of different levels of barley sowing densities on L. rigidum control. To this effect, a weed–crop population model for both L. rigidum and barley life cycles was developed. Our results point out: (i) the necessity of achieving high control efficiencies (>99%), (ii) that the increase of twice the standard sowing density of barley resulted in a reduction of 23.7% of the weed density, (iii) non-herbicide-based individual methods, such as delayed sowing and weed seed removal at harvest, proved to be inefficient for reducing drastically weed population, (iv) the implementation of at least three control tactics (seed removal, delay sowing and herbicides) is required for weed infestation eradication independently of the sowing rate, and (v) the effect of an increase in the sowing density is diluted as a more demanding weed control is reached. Future research should aim to disentangle the effect of different weed resistance levels on L. rigidum population dynamics and the required efficiencies for more sustainable IWM programs.

Highlights

Barley (Hordeum vulgare L.) is a major cereal grain grown globally in temperate climates, and it is mostly used as feed for animals, malt, and food for human consumption
According to the proposed model, a control program needs to achieve a minimum efficiency (Equation (11)) of c0 = 0.9966 in the case of a standard barley sowing density and c0 = 0.9955 in the case of a high barley sowing density to reach the ‘theoretical eradication’ of L. rigidum in the ten year horizon. Such efficiencies indicate that only the management scenario composed of control program S7 (c = 0.9965) combined with a high sowing density could lead to the extinction of L. rigidum, at least, in theory
In the absence of other control actions, an increase of twice the standard sowing density of barley resulted in a reduction of 23.7% of L. rigidum density as a consequence of the interspecific competition

Summary

Introduction

Barley (Hordeum vulgare L.) is a major cereal grain grown globally in temperate climates, and it is mostly used as feed for animals, malt, and food for human consumption. The annual world harvest of barley in the late century was approximately 140 million tons from about 55 million ha [1]. Barley yield is seriously affected by weeds, especially by annual ryegrass (Lolium rigidum Gaudin) in Mediterranean climates. Yield losses in cereal crops due to L. rigidum competition can reach up to 80% depending on the season and infestation level [2]. Its high seed production [3], high genetic variability [4], and high seed banks [5] facilitate the long-term survival of this weed species. Its control relies heavily on herbicides and, as a consequence, L. rigidum has evolved resistance to various herbicide groups [6]

Methods

Results

Discussion

Conclusion