EFFECT OF TEMPERATURE ON THE GERMINATION OF MAIZE WEED SPECIES

Weed emergence patterns at the field scale are the consequences of the probability of occurrence of certain meteorological conditions being suitable for dormancy release, germination, and emergence of proportions of seed populations at that time and also of management practices. A study of a three year period (2002-2004) in a Portuguese maize field is presented about the germination patterns as a function of temperature (GDD) of four main weed species, Chenopodium album L., Digitaria sanguinalis L., Portulaca oleraceae L. and Solanum nigrum L. Plot size was 16 x 9 m and the above ground flora was assessed in 25 samples (rectangles of 10 x 50 cm) placed on a sandy soil (1.7% organic matter, pH 6, 93.8% sand, 2 % silt and 4.2 % clay) on a 2 m x 2 m sampling grid. A logistic model was fitted for all the species. The possibility of incorporating these results into predictive thermal time models is discussed.