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Influence of Double-cut Plow Mulch Tillage on Number and Activity of Microorganisms¹

ABSTRACT

A decreased availability of plant food throughout the growing season has been observed for some stubble mulch practices. To determine if the microflora were involved as a possible factor in this plant food availability difference, comparative data were obtained from double-cut and turnplow soil samples. Under the conditions of this investigation the following microbiological factors may be related to the plant food tie-up problems: (a) The environmental conditions of better oxygen supply and more organic matter in the 0–6 inch horizon seem to favor the stimulation of the soil fungi in the mulch plots. This group of soil microorganisms might cause a temporary loss of nitrate-nitrogen as a result of protein synthesis by the mold cells. (b) Biochemical nitrification as determined with the perfusion apparatus of Lees and Quastel showed slightly lower amounts of nitrate-nitrogen formed from the mulch than from the turnplow samples. In addition, the soil pH should be considered as an environmental factor which may have considerable influence on the activity of the soil population. It is believed that these factors might be temporarily involved in the plant food tieup problems found to be associated with stubble mulch tillage practices at Virginia Polytechnic Institute.

¹ Contribution from the Biology Department and Agriculture Engineering Department, Virginia Polytechnic Institute, Blacksburg, Va. Presented before Section III, Soil Science Society of America, State College, Pa., August 30, 1951.

² Instructor in Bacteriology; Project supervisor, Soil Conservation Service; and Professor of Bacteriology, respectively.