Modeling Maize -Zea mays L.- leaf development and apex temperature under different thermal environments

Abstract

Accurate prediction of leaf appearance rate is required in maize (Zea mays L.) simulation models to estimate leaf area development, biomass and yield. Plant temperature is closely related to the development rate, but the air temperature record used to estimate plant temperature is often biased during the early stages of maize development because the growing plant parts are below the soil surface. A field study was used to compare measured soil, air and apex temperatures with maize leaf appearance rates. Seasonal variation in leaf tip appearance rates was observed for four sowing dates spaced about one month apart during 1996. Solar radiation and temperature of the air, apex and soil (0.01 m, 0.03 m and 0.05 m depths) were recorded on half-hourly intervals. Apex temperature was found to be close to the soil temperature at 0.03 m or 0.05 m when the apex was below the surface. When the apex was aboye the surface. its temperature was close to the air temperature. The phyllochron (degree- days between leaf appearance events) was found to be higher (52.4°C/leaf tip) than values used in most existing maize models. A functional model was developed to estimate mean daily apex temperature using inputs of daily maximum and minimum air temperatures and solar radiation. The model was tested using an independent weather data set. The resulting estimates had a root mean square error (RMSE) of 1.31°C per day and mean bias error (MBE) of -0.06°C respectively. After stem elongation pushed the apex aboye the soil surface, mean air temperature was close enough to the mean apex temperature to assume that they were equal.