IS-2102-93

Publications

Achievements

Reducing Evaporation from Cultivated Soils by Mulching with Crop Residues and Stabilized Soil Aggregates	Budget	Duration
	$240,000	3 years

	Fuchs, M.	ARO, Min. Ag.
	Hatfield, J.L.	USDA, ARS
	Hadas, A.	ARO, Min. Ag.
	Keren, R.	ARO, Min. Ag.

Final Report Abstract
Field and laboratory studies of insulating properties of mulches show that the changes they produce on the heat balance and the evaporation depend not only on the intrinsic characteristics of the material but also on the structure of air flow in boundary layer. Field measurements of the radiation balance of corn residue showed a decrease of reflectivity from 0.2 to 0.17 from fall to spring. The aerodynamic properties of the atmospheric surface layer were turbulent, with typical roughness length of 12 to 24 mm. Evaporation from corn residue covered soils in climate chambers simulating the diurnal course of temperature in the field were up to 60% less than bare soil. Wind tunnel studies showed that turbulence in the atmospheric boundary layer added a convective component to the transport of water vapor and heat through the mulches. The decreasing the porosity of the mulch diminished this effect. Factors increasing the resistance to vapor flow lowering the effect of wind. The behavior of wheat straw and stabilized soil aggregates mulches were similar, but the resistance to water of soil aggregate layer with diameter less than 2 mm were very large, close to the values expected from molecular diffusion.