Quantifying the effect of crop spatial arrangement on weed suppression using functional-structural plant modelling.

Jochem B Evers,Lammert Bastiaans

doi:10.1007/s10265-016-0807-2

Abstract

Suppression of weed growth in a crop canopy can be enhanced by improving crop competitiveness. One way to achieve this is by modifying the crop planting pattern. In this study, we addressed the question to what extent a uniform planting pattern increases the ability of a crop to compete with weed plants for light compared to a random and a row planting pattern, and how this ability relates to crop and weed plant density as well as the relative time of emergence of the weed. To this end, we adopted the functional-structural plant modelling approach which allowed us to explicitly include the 3D spatial configuration of the crop-weed canopy and to simulate intra- and interspecific competition between individual plants for light. Based on results of simulated leaf area development, canopy photosynthesis and biomass growth of the crop, we conclude that differences between planting pattern were small, particularly if compared to the effects of relative time of emergence of the weed, weed density and crop density. Nevertheless, analysis of simulated weed biomass demonstrated that a uniform planting of the crop improved the weed-suppression ability of the crop canopy. Differences in weed suppressiveness between planting patterns were largest with weed emergence before crop emergence, when the suppressive effect of the crop was only marginal. With simultaneous emergence a uniform planting pattern was 8 and 15 % more competitive than a row and a random planting pattern, respectively. When weed emergence occurred after crop emergence, differences between crop planting patterns further decreased as crop canopy closure was reached early on regardless of planting pattern. We furthermore conclude that our modelling approach provides promising avenues to further explore crop-weed interactions and aid in the design of crop management strategies that aim at improving crop competitiveness with weeds.

Highlights

Improving crop competitivenessWeeds can be classified as the potentially most serious biotic production constraint to agricultural production, while at the same time actual production losses due to weeds do not differ substantially from those caused by pests and diseases (Oerke 2006)
We study crop-weed competition for light using a modelling approach called functional structural plant (FSP) modelling (Evers 2016; Vos et al 2010), that explicitly includes plant architecture and the spatial configuration of the crop-weed canopy, and allows for the simulation of individual plants that grow while competing for resources in three-dimensional (3D) space
The build-up of crop leaf area over time was predominantly affected by the relative time of weed emergence (Fig. 2): early weed emergence resulted in maximum crop LAI of between 2.0 for 200 crop plants m−2 and 3.0 for 400 crop plants m−2 at a weed density of 100 plants m−2

Summary

Introduction

Improving crop competitivenessWeeds can be classified as the potentially most serious biotic production constraint to agricultural production, while at the same time actual production losses due to weeds do not differ substantially from those caused by pests and diseases (Oerke 2006). The reason is that, so far, weeds can relatively be controlled by a combination of primary tillage (the first soil tillage after the last harvest) and chemical means. This situation is rapidly changing, as due to the increasing interest in lowfrequency tillage systems, weed control is increasingly relying on herbicides. Care should be taken not to be caught in a negative spiral, where a smaller number of herbicides results in an increased risk of herbicide resistance that in turn results in a further reduction of suitable herbicidal compounds.

Methods

Results

Conclusion