Predicting weed emergence in maize crops under two contrasting climatic conditions

Abstract

Summary Predictive empirical models of the timing of emergence were developed for ten major weed species in maize crops. Monitoring of seedling emergence was performed over two years in two maize fields located in Central Spain and Tagus Valley in Portugal. Thermal time was used as the independent variable for predicting cumulative emergence. Different non‐linear growth curves were fitted to the data sets of cumulative percent emergence for the different species, sites and years using genetic algorithms. Based on their emergence patterns, weed species were arranged into three groups. Species with early‐season emergence (Abutilon theophrasti, Xanthium strumarium, Datura stramonium, Datura ferox, Sorghum halepense, Digitaria sanguinalis and Echinochloa crus‐galli) reached 70% emergence with less than 700 growing day degrees (GDD). Species with whole‐season emergence (Cyperus rotundus and Solanum nigrum) started early their emergence processes but the emergence continued throughout the maize life‐cycle; they required up to 1300 GDD to reach 70% emergence. The only species with late‐season emergence was Sonchus oleraceus; it required more than 1300 GDD to reach 70% emergence. The results obtained in our experiments have shown a good synchrony between the predictions obtained in different years in the same site. However, no single model was able to predict the timing of emergence in two sites with different environmental conditions, challenging the hypothesis that a single general model, based on temperature only, can be used to predict weed emergence in different geographical locations.

Infestation maps and spatial stability of main weed species in maize culture

“…These results are in accordance with studies in maize crops in different areas from Spain and Portugal (Dorado et al, 2009). …”

Base temperatures for germination of selected weed species in Iran

“…This awareness induced increasing interest in the development of models that can simulate seedling emergence and the potential benefits, but also challenges, of their adoption were recognised and thoroughly reviewed (Forcella et al 2000;Grundy 2003). Several models have been created for seedling emergence of various weed species in the main crops such as maize (Dorado et al 2009a;Masin et al 2012), soybean Werle et al 2014) or winter cereals (Royo-Esnal et al 2010, 2015García et al 2013;Izquierdo et al 2013). These models are often based on the hydrothermal time concept (Bradford 2002) and require the estimation of biological parameters, base temperature, and base water potential for germination (t b and Y b hereinafter), to simulate seedling emergence according to weather trends.…”

Hıyarda (Cucumis sativus L.) yabancı ot çıkış zamanın tahminine yönelik araştırmalar

“…They require integration of the methods thorough the season staring before transplanting of cucumber. Late emerging weeds cannot be competitive (Dorado et al, 2009); but, burs of T. terrestris can make harvest difficult for workers.…”

“…Experimental studies based on Dorado et al (2009). Seedling emergence monitored in 30 permanent quadrates (66 cm x 33 cm).…”

“…Recently models have been improved to use hydrothermal time. However, using only temperature data is still accurate (Forcella et al, 2000;Myers et al, 2004;Dorado et al, 2009), especially in irrigated crops under adequate soil moisture conditions (Masin et al, 2012). Different cropping activities and environmental and climatic factors require develop models for different conditions and crops (Colbach et al, 2005;Dorado et al, 2009;Masin et al, 2010).…”