Carbohydrate materials, crop residues and proteinaceous materials were degraded by soil microflora in the presence and absence of clay minerals. The carbohydrates used included two cellulose dextrins differing in solubility and chain length, polysaccharides from sweet corn, starch dextrin, and hydroxyethylcellulose. The crop residues used were alfalfa meal, soybean leaf meal, soybean meal, and oat straw. Casein and gelatin were utilized as proteinaceous materials. A yeast nucleinic acid and a pectin (RX3) also were used in this study.
A calcium bentonite, an illite, and a calcium kaolinite of pH 8.0 respectively, were added to the substrates in a mineral medium and phosphate buffer. Carbon dioxide was collected in standard Baryta's solution and determined by titration. The activity of the enzymes, cellulase and hemicellulase was determined in the presence and absence of two clay minerals using an Ostwald viscometer to measure the time of efflux.
The association of the substrate with the bentonitic clays resulted in an attenuated breakdown of many of these substrates. Very little protective influence was noted with the illitic and the kaolinitic clays. However, the kind and complexity of the substrate influenced the amount of breakdown; the simpler compounds were broken down more completely than the complex. The cellulose dextrins, casein, gelatin, soybean leaf meal, alfalfa meal, soybean meal and oat straw all evolved less carbon dioxide in the presence of calcium bentonite than in its absence.
Aggregat e analyses oI Breton plot soils usi ng a wet sie.ving-technique revealed marked differences resulting from cropping practices but 1ew, il any' due to fertilizers. 'fhe mean $eiq6t-diametei ol'soils from plots in a 5-year rotation of grains and legumes waJalmost double the diarneter of soils from plots in a whiat-fallow ."-qu"tt.". \\rith respect to fertilizers, however, mean weightdiameter ol' soils from hish vielding plots in either cropping system were in general similar to those"on-low-yielhirrq plots of the system in.qu.estion' rncidentallv oolvsaccharide content of the soil showed a definite relationship to mean weight-diameter. IJI Can. J. Soil. Sci. Downloaded from www.nrcresearchpress.com by 44.224.250.200 on 07/06/20 For personal use only.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.