Sawdust composts in soil improvement
As indicated in a previous paper 2) the use of wood wastes in soil improvement has received considerable attention lately. Composting seems to offer large possibilities for avoiding the adverse effects of fresh sawdust and to utilize the potentialities of sawdust as a soil builder in the best fashion. The literature on composting of various waste products has been listed and reviewed very comprehensively i n t w 0 recent publications 1). The investigations rePorted here are preliminary tests of methods of composting sawdust and tests of the resulting materials on plant growth in greenhouse pot cultures.
Field plot studies with sawdust for soil improvement
SummaryHeavy application of fresh and rotted sawdust to field plots in comparison to manure and untreated control plots showed no significant difference in yields of corn over a four year period. The soil type was coarse textured and poor in nutrients at the start. However, the total yields for the rotted sawdust plots were consistently greater each year than those for the other treatments, thus possibly indicating a trend of benefit for the rotted sawdust treatments. Total yields for the fresh sawdust were close to those for the controls.Heavy applications of fertilizer, especially nitrogen, were necessary the first three years, but only a rather light application was necessary the fourth year.Soil moisture determinations indicate that all of the organic materials tend to prevent pronounced fluctuations in moisture levels, the rotted sawdust most of all.
INFLUENCE OF DRY SOIL ON ROOT EXTENSION.
Previous work at this Station (2) shows that the percentages for the relative wetness of soils expressed as ratios of soil-moisture contents to their respective moisture equivalents may be used to show the development of roots, and the results of adequate moisture samples, taken at proper times, indicate with a fair degree of accuracy the presence or absence of roots growing in the soils tested. It was further concluded, "that if the soil is wet at the beginning of the growing season to the full depth to which roots of plants would normally penetrate, subsequent additions of water by rain or irrigation, unless adverse conditions for growth are brought about thereby, can have but little influence on the extent of the root system developed. " In connection with the studies from which these findings were drawn, the question arose as to whether roots would elongate into dry soil. SHANTZ (6) believes that some drought resistant plants do have the ability to push their roots through dry soil, but that ordinary field crops do not. MAGISTAD and BREAZEALE (5), also, believe that some plants will send their roots through dry soil and BREAZEALE (1) thinks that roots will elongate into dry soil because of the "build up" of the moisture content of the dry soil by water transported from the roots in moist soil. LIvINGSTON'S work (3) at Tucson, Arizona, shows that the roots of seedlings penetrated downward when the soil was wet from the frequent showers of the rainy season, but there is no evidence in his report to show that the roots of these plants had the ability to traverse dry soils. In the work previously mentioned (2), it was reasoned, largely from theoretical considerations, that roots do not penetrate dry soils. Since the publication of the previous report some simple experiments have been carried out to ascertain the influence of dry soil on root extension.