Model of crop:weed competition applied to maize:Abutilon theophrasti interactions. I. Model description and evaluation

Abstract

A complex set of interactions among crops, weeds and their environment determines the impact of weed interference on crop productivity. These interactions can be simulated with dynamic crop:weed competition models, such as ALMANAC. In this study, ALMANAC was modi®ed to simulate maize:Abutilon theophrasti competition. In the modi®ed ALMANAC model, daily increases in leaf area index (LAI), height and rooting depth are attenuated on the basis of accumulated above-ground biomass and by environmental stress. Also, a simple,¯exible method is adopted to partition radiation in a mixed canopy. A maize:A. theophrasti competition study conducted near Aurora, NY, in which a range of weed densities (0±16 plants m A2 ) were established in a maize crop, was used to evaluate the model. The modi®ed ALMANAC proved to be a useful tool for segregating the maize response to competition in 1991 (simulated loss of 35% at the highest weed density) from those in 1992±94 (simulated losses not greater than 16%). Based on these ®ndings, the modi®ed ALMANAC model is judged to be capable of distinguishing between environmental conditions that facilitate large yield losses and those that allow maize to outcompete A. theophrasti.

Competition of velvetleaf (Abutilon theophrasti M.) weed with cotton (Gossypium hirsutum L.). Economic damage threshold

“…According to McDonald and Riha (1999), EDT should ∆EDT ( not be used in the integral management of this weed in maize fields; in this respect, they agree with Sattin et al (1992) that, below the EDT level, the cost of weed control exceeds crop losses avoided. The potential problems posed by seeds from uncontrolled velvetleaf individuals should be avoided by careful hand removal from newly infested fields.…”

Modelling crop-weed competition: Why, what, how and what lies ahead?

“…Models have also been used to investigate the impacts of weed density and spatial patterns (e.g. McDonald and Riha, 1999;Evers and Bastiaans, 2016). In real fields, these are unlikely to be determined directly by the farmer, but weed density will be influenced by management actions such as herbicide application, cultivation, hand-weeding, harvest weed seed control, as well as insect predation of seeds or degradation in the soil, which may be indirectly influenced by farmer actions such as cultivation.…”

Influence of soybean row width and velvetleaf emergence time on velvetleaf (Abutilon theophrasti)

“…Velvetleaf can complete its life cycle even when grown under a crop canopy (Mitich 1991) and can produce up to 17,000 seeds per plant seed (Warwick and Black 1988). Velvetleaf competitive effects have been studied in many crops, including soybean (Dekker and Meggitt 1983;Lindquist et al 1995;Patterson 1992;Regnier and Stoller 1989), corn Mortensen 1998, 1999;McDonald and Riha 1999), tomato (Lycopersicon esculentum) (Ngouajio et al 2001), and cotton (Gossypium hirsutum) (Smith et al 1990). Although velvetleaf has been evaluated under varying shade and water regimes under controlled environments (Sailsbury and Chandler 1993), no studies reported any evaluation of velvetleaf growth under field conditions in soybean with soybean row width and the relative emergence time of velvetleaf taken under consideration.…”