environmental management systems to counteract 

 adverse responses. When these models are appro- 

 priately interfaced, crop yield prediction is im- 

 proved. 



Characterization of new pathogenic nucleic acid 

 moieties. The discovery of viroids and myco- 

 plasms as causative agents of viral diseases opens 

 up new areas for research. The presence of any 

 array of nucleic acid pathogens ranging from the 

 naked viroid to the viral nucleoproteins and on to 

 the more highly organized bodies of mycoplasms 

 analogous to a primitive form of naked bacteroid 

 cells presents a problem of differentiation and 

 development of different approaches to therapy. 

 The most reliable diagnostic device for myco- 

 plasms is their response to highly specific antibiot- 

 ics. The processes for biogenesis of this material 

 and transmission of hereditary control must be 

 resolved. Among this series of agents are some of 

 the most pernicious and destructive pathogens. 



Alternative sources of energy. Farm and forest 

 operations must become more versatile in the use 

 of energy. Capability is required to utilize multi- 

 ple sources of energy in agricultural operations 

 such as solar radiation, wind, coal, crop and for- 

 est residues, nuclear radiation, and oil, as well as 

 other sources presently unknown. The biomass 

 conversion of plant materials to energy requires 

 concerted study. The energy potential of various 

 plants requires study as does potential production 

 of the most desirable biological materials. 



Salt control of irrigation return flows. Under 

 natural conditions, rainfall leaches salt below the 

 root zone of native vegetation. If crops with deep- 

 er rooting patterns are planted, some provision 

 to move the salt deeper must be made. Under irri- 

 gation, this means adding more water than is lost 

 by evapotranspiration. If excess water is applied, 

 the subsoil salt is leached into the stream. 

 Methods to add only enough water to keep plants 

 turgid and salt just below the roots will result in 

 less salt returned to streams. This approach to 

 water quality control is much more economical 

 and attractive than chemical desalting. 



Biomass productivity and fuel combustion effi- 

 ciency. Producing the maximum amount of wood 

 and other organic fibrous materials in the shortest 

 time possible by closely integrated use of fast- 

 growing improved genetic material, close spac- 

 ings, application of intensive cultural practices, 

 and total tree or crop plant harvesting and utiliza- 

 tion requires a strong underpinning of basic 

 knowledge. Forest biomass produced under inten- 

 sive short rotation management is highly suitable 

 for various wood-using industries and as basic 

 raw material for energy production. Quantity and 

 quality of material produced, energy trade-offs, 

 and the economic alternatives of intensive short 



rotation management for maximizing biomass 

 production are practical considerations as basic 

 knowledge is put into use. 



Opportunities of use of wood and other organic 

 fibrous materials as an alternate fuel to natural gas 

 and oil is highly dependent on obtaining maximum 

 combustion efficiency. However, little is known 

 about the refinements for improving this efficien- 

 cy, particularly about the interrelationships of parti- 

 cle size, moisture content, and density as they re- 

 late to alternative combustion and fuel-handling 

 techniques. 



Combustion products and their photochemistry. 

 The growing use of fire as a silvicultural practice, 

 coupled with the increasingly stringent air quality 

 standards requires in-depth exploration of the 

 chemistry of wood combustion and variations in 

 combustion products with species and burning 

 conditions. Release of these combustion products 

 into the atmosphere where they are subjected to 

 radiation throughout the solar spectrum, as modi- 

 fied by atmospheric transmissivity, demands the 

 production of new knowledge about these photo- 

 chemical processes involving combustion prod- 

 ucts. 



Wood structure and durability. Principles lead- 

 ing to improved performance and longer lasting 

 materials must be better understood to help en- 

 sure adequate long-term supplies of the Nation's 

 basic materials of construction. Additional infor- 

 mation on the long-term loading characteristics of 

 wood and wood structural components; on wood- 

 insect relationships, wood-fungi relationships, and 

 wood-fire relationships; and on the manipulation 

 of tree physiology will eventually lead to effective 

 combined wood treatment and wood construction 

 systems that are efficient and reduce the needs for 

 toxic chemicals and large energy inputs. 



Nutrient gains and losses associated with inten- 

 sive forest management. Intensive cultural prac- 

 tices in concert with improved utilization prac- 

 tices are expected to result in major changes in 

 soil nutrient reserves over a wide range of forest 

 sites. Nutrient gains can be achieved by artificial 

 applications of fertilizers, use of nurse crops and 

 introduction of nitrogen-fixing plants. Nutrient 

 losses result from complete removal of forest 

 biomass and from soil disturbances attributable to 

 intensive site preparation, vegetation control, and 

 other related practices. Better understanding of 

 nutrient budget and nutrient cycling processes 

 under various intensities of forest management 

 over a wide range of soil and site conditions will 

 help maintain needed forest characteristics. 



Forest fire effects. It is necessary to be able to 

 predict the effects of fire on many components of 

 forest ecosystems. This includes relationships of 

 plants or organisms to fire, especially their heat 



AGRICULTURE 27 



