WASTES IN RELATION TO AGRICULTURE AND FORESTRY 



OO 



at least 5 years before the cause of the injury was 

 attributed to ozone in the ambient atmosphere. 



Spinach is exceedingly susceptible to photo- 

 chemical air pollutants. Current observations in- 

 dicate that several spinach lines are tolerant to 

 certain air pollutants. Crosses have been made to 

 develop lines and hybrids having a high level of 

 tolerance to airborne contaminants as well as hav- 

 ing a resistance to major spinach diseases. 



Forestry researchers have made selections of 

 ponderosa and eastern white pines that are nearly 

 immune or highly tolerant to specific air pol- 

 lutants such as S0 2 , F 2 , ozone, and PAN. Genetic 

 variation in susceptibility has been established. 

 Clonal lines with high tolerance have been selected 

 for reforestation in high-hazard areas, and lines 

 with low tolerance for use as monitors of air pol- 

 lution. The demand for such clonal materials im- 

 pelled the research on expediting reproduction of 

 elite clonal materials. To illustrate the urgency of 

 this research, trees along highways and in metro- 

 politan areas may all need to be from resistant 

 clones. 



Some corn varieties are susceptible to fluorine 

 injury; however, ever-increasing air pollution 

 show good potential for breeding reseai-ch in this 

 species. 



Even though relatively tolerant strains are de- 

 veloped, plant breeders must continue their re- 

 search. In 1963, cigar-wrapper tobacco growers 

 around South Hartford, Conn., found that a vari- 

 ety considered resistant was significantly damaged 

 by fleck. The point illustrated is that varieties with 

 higher resistance have high threshold values for 

 injury; however, ever-increasing air pollution 

 around metropolitan areas can overtake the thres- 

 hold values of injury of even the more resistant 

 varieties. 



Air pollution injury has been reduced by appli- 

 cation of chemicals to foliage. Field and fumiga- 

 tion tests in California disclosed that a number 

 of fungicides and antioxidants reduced damage to 

 beans, lettuce, and endive. Numerous compounds 

 will reduce ozone injury or weather fleck on 

 tobacco. Various fungicides and such materials as 

 ascorbic acid, powdered clay, kaolin, and diato- 

 maceous earth have been evaluated. It was recently 

 shown by the U.S. Department of Agriculture that 

 the application of AyV'-diphenyl-p-phenylene 

 diamine protected tobacco from ozone fleck with- 

 out evidence of injury to the plant by the applied 

 chemical. 



Research is revealing many difficulties in using 

 chemical treatments to prevent air pollution in- 

 jury. For example, treatments may be washed off 

 by rains or sprinkler irrigation and thereby require 

 frequent application. The chemical residues from 

 the treatment may be hazardous to consumers. 

 Because of this concern over residues, research has 

 not yet produced a satisfactory chemical treatment 

 to prevent air pollution injury to crop plants. 



Applied research has developed a practical 

 method of reducing or preventing certain types of 

 air pollution injury to plants in greenhouses. A 

 number of greenhouses in California are equipped 

 with carbon filters to remove ozone and other oxi- 

 dants. At present, the method is expensive to in- 

 stall and the filters may need to be replaced after 

 a few years, or even a few months, of operation. 

 Evidence of air pollution damage in greenhouses 

 in the eastern United States is increasing. 



Preliminary studies show that cultural pro- 

 cedures may affect the extent of air pollution in- 

 jury. Irrigation tends to accentuate the damage. 

 Levels of mineral nutrients appear to modify the 

 adverse effects of air pollution. The complexity of 

 current observations, however, offers no clear-cut 

 conclusions. 



Research underway pertaining to the injury, 

 and the abatement of injury, of these airborne 

 chemicals on crops, trees, and animals obviously is 

 inadequate. 



Smoke From Wild Forest Fires 



As indicated in appendix II (Organic Wastes), 

 wild forest fires during the average year emit 

 hundreds of thousands of tons of hydrocarbons 

 and millions of tons of particulates into the atmos- 

 phere. Abatement of this smoke production has 

 importance in air pollution control besides the 

 urgent need to minimize decimation of our forests. 



The Forest Service began research on forest fire 

 control in 1923. The three Forest Fire Laboratories 

 conduct research on the development oi | 1) fire 

 danger prediction systems; (&) aerial tire control 

 methods; (c) low-cost fire-retardant chemicals: 

 and (</) infrared fire detection and mapping 

 techniques. 



The importance of the application of these re- 

 search findings is indicated by the reductions in 

 fire damage in the National forests from 602, 

 acres in L924 to ''-2.000 acres in 1963. In 1964, the 

 average expenditure for tire protection on Federal. 



