Evaporation from Manure-amended Soil.

Organic matter from the field-applied manure can alter soil hydraulic properties. Our objective was to compare evaporation from soil without manure and with manure in controlled conditions. Soil samples were taken from the plough layer of mesic Typic Hapludult in at the Beltsville USDA facility. The air-dry soil was passed through the 2-mm sieve and mixed thoroughly with the fresh bovine manure slurry at manure/soil ratios of 1:20, 1:10, and 1:7. The soil manure-mix was uniformly packed into acrylic rings and saturated with the water. The rings with soil were kept in a refrigerator at constant 9 C temperature and 18% relative humidity during 19 days. The mass of rings with soil was measured and recorded every 15 minutes. The two-stage evaporation from all samples was observed. The first stage of relatively high and almost constant evaporation rate became shorter with the increase in manure/soil ratios. The evaporation rate did not differ among the samples with different manure contents at this stage. The second stage of continuously declining evaporation rate became longer as manure content increased. An increase in manure content caused a decrease of soil water content range for the first evaporation stage and an increase of this range for the second evaporation stage. Overall, addition of manure to soil decreased evaporative water loss.