The role and contributions of animals in alternative agricultural systems
Livestock are important components of agricultural systems. In the U.S., one-half of total agricultural receipts come from the sale of livestock. They are the harvestors of range plants, forages, and crop residues; they level out the effects of the seasonally and variability of rainfall; they cushion disruptions in the trade and marketing of feed grains; they counteract declining soil fertility and soil erosion; and they contribute to the efficient year-round use of farm labor. Unfortunately, farmers are often not inclined to adopt alternative animal agriculture systems despite the advantages they may offer. Constraints that may be encountered include possibilities of reduced short-term profits, difficulties in adapting available technology to alternative farming systems, difficulties in shifting from specialized crop or livestock farms to crop/livestock farms, and the increased needs for labor and management. Some actions needed in the U.S. to improve livestock production in alternative farming systems are: the establishment of government policies to promote the shift of marginal lands to soil and water conserving crops and the incorporation of pastures and forages in crop rotations; research to improve the utilization by ruminants of ligno-cellulosic feeds (pastures, forages, crop residues); and programs to improve range and forest management and to lead to the development of systems that optimize the use of forages for the production of nutritionally desirable lean beef.
Evaluation of the use of agricultural residues as an energy feedstock. Volume I
Since agricultural residues (crop and forest wastes and animal manures) constitute a potential supplemental source of energy, the authors examine the availability of such residues and evaluate their potential use as an energy feedstock. The report is presented in two volumes: the method of approach used in inventory development, the collection, harvesting, and conversion economics, and the overall concept assessment are presented in Volume I.
Investigations on the rôle of organic matter in plant nutrition
1. As the result of decomposition of green manure in a swamp soil, the coarse fractions (including coarse and fine sand) of the surface layer (first 3 inches) decreased by 11·2 per cent. while the fine ones (silt+clay) increased by 9·8 per cent. in the course of 43 days. The effect was less pronounced in the manured soil maintained at 60 per cent. saturation, while no alteration was to be noticed in the case of the unmanured specimens. 2. Treatment with dilute hydrochloric acid prior to dispersion had no appreciable effect on the estimates of mechanical composition obtained in the different cases. Loss in solution was also comparatively small. 3. The silica-sesquioxide ratio increased slightly as the result of decomposition of green manure in swamp soil. The composition of the fine fractions was also altered, the total percentages of the oxides of iron, aluminium and silicon increasing from 90·5 to 99·3 in the course of 71 days. 4. The practical significance of the above and related observations has been discussed.