Agriculture and Environment最新文献

Results of studies in western Canada aimed at developing low cost, minimum processing or optimum processing strategies of utilizing crop residues and forages are reviewed. These studies involved the following components:

• 1.

  (1) Studies were conducted to determine which crop residues and forages have high feed values without expensive processing. Sunflower heads, after seed harvest, and faba bean crop residue, for example, showed feed values (in vitro OMD of 71% and 61% respectively) considerably above values for wheat and barley straw (OMD of 37% and 48%).

• 2.

  (2) With regard to the feed value of common cereal straws, studies determined the influence of differences between cultivars, season and location of growth and fertilizer supply. Significant differences in feed value were observed between cultivars, although season and location effects were at least as large. Nitrogen fertilizer application increased crude protein content and yield, but effects on in vitro digestibility were less predictable.

• 3.

  (3) Analyses of the feed value of chaff, leaf and stem components of a number of wheat cultivars indicated that chaff and leaf components were significantly higher in value than stems. The effect of nitrogen fertilizer rate of application on the feed value of each crop residue component was evaluated.

• 4.

  (4) Ammoniation of wheat chaff and wheat straw significantly improved feed value with chaff having a higher feed value than straw. Weed seeds, such as might be collected with chaff, were shown to have germination ability destroyed by ammonia treatment. Chaff removal for feed use may be more environmentally acceptable than straw removal in semiarid areas.

The energy requirements of a number of novel protein production systems are compared, along with an examination of the relevant environmental implications of such systems. It is postulated that energy analysis has a role to play in food policy planning through the trade-off between energy and land. The prospects for single cell protein (SCP) fermentations, leaf protein, fish farming, fish protein concentrate, algal cultivation and hydroponic plant growth systems are evaluated, with special emphasis being placed on the last two. Of the processes investigated, SCP from carbohydrate substrates, algal protein and fish protein seem to hold much promise, while hydroponics could be very significant in areas lacking in arable land. The potential of leaf protein and SCP derived from oil appears to be very limited at present, and will probably never provide a significant contribution to world protein supplies.

Many important characteristics of bacteria are determined by relatively small genetic elements known as bacterial plasmids. Such agriculturally and environmentally important bacterial characteristics as multiple antibiotic resistance in animal pathogens, nodulation and nitrogen fixation in Rhizobium—plant symbioses, crown gall formation by plant pathogenic Agrobacterium species and pesticide degradation by members of the genus Alcaligenes have been shown to be carried as part of transmissible plasmids. The widespread use of antibiotics in human and veterinary medicine and agriculture has resulted in the evolution and spread of multiple drug resistance plasmids. The problem of drug resistance might be overcome by reduction or pronhibition of the use of clinically important antibiotics for non-therapeutic purposes such as growth promotion or prophylaxis. An understanding of the role of plasmid-borne nitrogen fixation/nodulation characteristics of Rhizobium species may provide an alternative to the use of very expensive nitrogenous fertilizers. Studies of the plant pathogenic Agrobacterium have led to successful biological control of crown gall. Finally, the manipulation of pesticide degrading plasmids has already demonstrated their potential for reducing environmental pollution resulting from the widespread use of complex synthetic molecules in both industry and agriculture.

The sagebrush (Artemisia)/grasslands of western North America are a tremendous grazing resource that currently is producing forage at only about one-half of its potential. The history of degradation of this environment is traced from the late 19th century, when livestock were introduced to the sagebrush rangelands. The dominant species of sagebrush that characterize the landscape are not preferred by domestic livestock. Continuous excessive grazing greatly reduced the perennial grass cover and allowed shrubs to increase. Phenoxy herbicides proved to be very valuable and economically feasible tools for improving grass and other forage production on shrub-dominated rangelands. Second-generation herbicides were used in controlling alien annual weeds to permit the seeding of degraded sagebrush rangelands. These techniques for control of herbaceous weeds were vertically integrated with brush control and seeding techniques for total range improvement. Environmental and economic constraints brought improvement of sagebrush range to a virtual standstill during the nineteen-seventies.