Effect of mulches on soil temperatures during the warmest week in July, 1925

Abstract does not appear. First page follows.

Previous investigations⁽¹⁾, ⁽²⁾, ⁽³⁾ on the use of paper as a mulch in contrast to soil mulches have dealt mainly with the effect on crop growth and crop yields. Investigations are now under way regarding the effects of such paper covering on the temperature and moisture conditions of the soil, and also on the most desirable kind of paper to use with particular regard to color, weight, durability, and need for perforations.

By the use of an unperforated black paper mulch at Berkeley in 1924, Shaw⁽⁴⁾ found that the soil at a depth of three inches averaged about 0.42° F warmer than at a similar depth in the soil-mulched plots. Hartung⁽²⁾ in the pineapple fields of Hawaii obtained higher mean soil temperatures at a depth of three inches in areas covered with grayish brown paper mulches than in unprotected soil. In his summary he states that “paper mulch maintains a mean soil temperature in the upper 3-inch layer of soil during the cool season in the localities given, from 3 to 4.5 degrees Fahrenheit above that of nonpaper covered soil; provided the mulch paper is dark, preferably black in color.” Although the standard mulch paper which Hartung used presented a “greyish brown appearance,” he nevertheless recommends black paper. Stewart⁽⁵⁾ and his co-workers in Hawaii found that on clear days the areas covered with black paper were from 12° to 15° F warmer during the day, and from 4° to 5° F warmer during the night.