MOISTURE-CONTENT OF CEREALS AT HARVESTING TIME BY COMPARING MICROCLIMATE VALUES AND STANDARD WEATHER DATA

The relationship between standard weather data and the microclimate of wheat and barley during harvesting time has been determined. The mois ture content of wheat and barley together with the weather elements ha ve been measured at 3 different experimental sites in the Netherlands in the harvesting seasons of 1990 and 1991. The difference in the dew point temperature in the screen and in the field is small. However, th e differences between air temperature in the screen and those at diffe rent heights in wheat as well as in barley are considerable. In daytim e the surface temperature of barley is higher than that of wheat under the same weather conditions as a result of a higher absorbtion coeffi cient. Both for wheat and barley, the maximum difference between the c alculated moisture content is 0.5%, the air temperature at 1.5 m heigh t from the nearest standard weather station and the surface temperatur e of the ears. Barley has a greater daily cycle in the moisture conten t of the grains than wheat as a result of a high equilibrium moisture content during the night and a low one in daytime.