Using simulation models to investigate the cumulative effects of sowing rate, sowing date and cultivar choice on weed competition

Izzadora K.S Andrew,Jonathan Storkey

doi:10.1016/j.cropro.2016.05.002

Abstract

With the increasing pressure on crop production from the evolution of herbicide resistance, farmers are increasingly adopting Integrated Weed Management (IWM) strategies to augment their weed control. These include measures to increase the competitiveness of the crop canopy such as increased sowing rate and the use of more competitive cultivars. While there are data on the relative impact of these non-chemical weed control methods assessed in isolation, there is uncertainty about their combined contribution, which may be hindering their adoption. In this article, the INTERCOM simulation model of crop/weed competition was used to examine the combined impact of crop density, sowing date and cultivar choice on the outcomes of competition between wheat (Triticum aestivum) and Alopecurus myosuroides. Alopecurus myosuroides is a problematic weed of cereal crops in North-Western Europe and the primary target for IWM in the UK because it has evolved resistance to a range of herbicides. The model was parameterised for two cultivars with contrasting competitive ability, and simulations run across 10 years at different crop densities and two sowing dates. The results suggest that sowing date, sowing density and cultivar choice largely work in a complementary fashion, allowing enhanced competitive ability against weeds when used in combination. However, the relative benefit of choosing a more competitive cultivar decreases at later sowing dates and higher crop densities. Modeling approaches could be further employed to examine the effectiveness of IWM, reducing the need for more expensive and cumbersome long-term in situ experimentation.

Highlights

In agricultural systems, a careful balance is required between producing a high value crop yield and minimising costs
Over-reliance on herbicides has led to widespread resistance in many problematic weed species (Heap 1997; Moss et al, 2011) and the current herbicide-based weed control paradigm is widely considered to be unsustainable
We demonstrate how the INTERCOM model of plant competition can be utilised to observe the combined effect of sowing density, sowing date and cultivar choice, using wheat and A. myosuroides as model species

Summary

Introduction

A careful balance is required between producing a high value crop yield and minimising costs. Non-chemical control techniques employed in IWM are numerous and can be divided into those implemented over several seasons, including rotational ploughing and increased crop diversity, and within-season measures The latter include increased sowing rate and growing more competitive cultivars to minimise weed seed return. Non-chemical weed management options will be employed in combination with herbicides but by increasing crop competitiveness, the required efficacy and reliance on herbicide control is reduced. This annual grass species can cause substantial losses to wheat (Storkey et al, 2003) and herbicide resistance is widespread in North-West Europe (Moss et al, 2011; Lutman et al, 2013; Keshtkar et al, 2015), and is the focus of this study

Methods

Results

Discussion

Conclusion