Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2006
Publication Date: 7/1/2006
Citation: Akdogan, H.P., Casada, M. 2006. Climatic humidity effects on controlled summer aeration in the hard red winter wheat belt. Transactions of the ASABE. 49(4): 1077-1087 Interpretive Summary: It is difficult to aerate wheat immediately after harvest as part of an integrated pest management (IPM) strategy in much of the hard red winter (HRW) wheat belt due to high ambient temperature as well as high nighttime relative humidity. The high ambient temperatures are well known, but the complicating effect of high humidity has not been well documented. We evaluated 50 years of historical weather data and developed maps covering the HRW wheat belt that show the combined effect of high temperature and high humidity on summer aeration. The maps show contours of average hours when summer aeration is effective after accounting for the complicating effect of high humidity. The actual hours available for effective grain cooling were reduced by an average of 68% for 12% moisture content wheat and by 88% for 10% moisture content wheat compared to the hours suggested by ambient temperatures when neglecting the humidity effect. These maps allow engineers to properly design aeration systems with correct fan sizes for summer aeration and show where the climate makes summer aeration impractical.
Technical Abstract: Aeration is an inexpensive way to improve grain storage conditions, but can be difficult to implement immediately after harvest in much of the hard red winter wheat belt due to high ambient temperatures. High nighttime relative humidity worsens this problem because the heat of condensation released during adsorption reduces aeration cooling, but the magnitude of the humidity effect is not well documented. A procedure was developed to calculate effective temperature (Teff), which coupled dry-bulb (Tdb), wet-bulb temperature (Twb), and grain moisture content to predict the actual final grain temperature after aeration. Hourly historical weather data was used to determine the hours of temperature accumulation below 24'C from mid-July through early August in Kansas, Oklahoma, Texas, eastern New Mexico, and eastern Colorado along with nearby portions of surrounding states. Grain cooling was highly influenced by humidity and actual available hours averaged approximately 75% less during the periods studied compared to calculations based on Tdb alone. Latitude rather than longitude influenced the shape of the contour lines of aeration hours calculated by using Tdb since latitude omits the effects of humidity, whereas longitude had a strong influence when actual available hours were determined based on Teff. Airflow rates higher than 0.1m3/min/t would be necessary to achieve sufficient grain cooling for the summer in southern Texas and Oklahoma. This effect was more pronounced at 10% mc than 12% mc grain because Teff was always lower for grain at 12% mc. The highest number of aeration hours was accumulated during late night to early morning, regardless of the region studied. In general, within a given period, the hot and humid south accumulated the least number of available aeration hours whereas eastern Colorado accumulated the most.