Effect of crop residues on soil temperature
1946
McCalla, T.M. | Duley, F.L.
Soil temperatures were determined under the quantities of residues used in the system of subsurface tillage, or stubble mulching, as compared with soil temperatures when using heavy mulches or the conventional system of plowing. Heavy mulches, such as an 8-ton per acre application of straw, have lowered soil temperatures as much as 17.7 degrees C at the 1-inch depth. For a period of 3 or 4 months after the application of a straw mulch at the rate of 2 or 3 tons per acre, soil temperatures may be reduced from 3 degrees to 6 degrees C at the 1-inch depth and 2 degrees to 4 degrees C at the 4-inch depth. However, with the stubble mulch system of farming, soil temperatures were not reduced appreciably below that of plowed land after 6 to 9 months. In such farming, only amounts of residues equal to those grown on the land were returned to the surface of the soil, while decay and fragmentation of the residue continued. Soil temperature of the mulched plots lagged behind air temperature and this difference reached a peak on clear days around 1 to 2 o'clock. Soil temperature reached the lowest point for the day along with the air temperature at about 5 a.m. At this time mulched and bare plots usually had almost the same temperature. It was during the day that the temperature of the bare soil exceeded the mulched soil. The temperature, after considerable decay had taken place, at the time of widest differences was only a few degrees lower on the mulched soil. Generally, soil temperature under mulches did not appear to be unfavorable to plant growth where an amount of residues equal to that grown on the field was used. Due mainly to shading, a growing crop on the land decreased the temperature differences between the mulched and unmulched soil.
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