Using thermal units for estimating critical period of weed competition in off-season maize crop

Romiro Fernando López-Ovejero, Axel Garcia Y Garcia, Saul Jorge P. De Carvalho, Pedro J. Christoffoleti, Durval Dourado Neto, Fernando Martins, Marcelo Nicolai

    Research output: Contribution to journalArticlepeer-review

    2 Scopus citations


    Brazilian off-season maize production is characterized by low yield due to several factors, such as climate variability and inadequate management practices, specifically weed management. Thus, the goal of this study was to determinate the critical period of weed competition in off-season maize (Zea mays L.) crop using thermal units or growing degree days (GDD) approach to characterize crop growth and development. The study was carried out in experimental area of the University of São Paulo, Brazil, with weed control (C), as well as seven coexistence periods, 2, 4, 6, 8, and 12 leaves, flowering, and all crop cycle; fourteen treatments were done. Climate data were obtained from a weather station located close to the experimental area. To determine the critical period for weed control (CPWC) logistic models were fitted to yield data obtained in both W and C, as a function of GDD. For an arbitrary maximum yield loss fixed in 2.5%, the CPWC was found between 301 and 484 GDD (7-8 leaves). Also, when the arbitrary loss yield was fixed in 5 and 10%, the period before interference (PBI) was higher than the critical weed-free period (CWFP), suggesting that the weeds control can be done with only one application, between 144 and 410 GDD and 131 and 444 GDD (3-8 leaves), respectively. The GDD approach to characterize crop growth and development was successfully used to determine the critical period of weeds control in maize sown off-season. Further works will be necessary to better characterize the interaction and complexity of maize sown off-season with weeds. However, these results are encouraging because the possibility of the results to be extrapolated and because the potential of the method on providing important results to researchers, specifically crop modelers.

    Original languageEnglish (US)
    Pages (from-to)1-11
    Number of pages11
    JournalJournal of Environmental Science and Health - Part B Pesticides, Food Contaminants, and Agricultural Wastes
    Issue number1
    StatePublished - 2005


    • Corn
    • Critical period
    • Growing degree days
    • Interference
    • Off-season


    Dive into the research topics of 'Using thermal units for estimating critical period of weed competition in off-season maize crop'. Together they form a unique fingerprint.

    Cite this