Thomas S. Osborne

“ Atoms in Agriculture The Understanding the Atom Series
Nuclear energy is playing a vital role in the life of every man, woman, and child in the United States today. In the years ahead it will affect increasingly all the peoples of the earth. It is essential that all Americans gain an understanding of this vital force if they are to discharge thoughtfully their responsibilities as citizens and if they are to realize fully the myriad benefits that nuclear energy offers them. ”

“ Because of the time and expense, researchers in the past have merely tested groups of animals on a ration for a few weeks and then estimated the total gain by weighing and measuring. The main drawback to such a method is that it measures total growth only. In meat animals, knowing total growth is less important than knowing how much gain is in the more valuable lean meat, how much is in fat, and how much merely water. ”

“ It is the responsibility of the Federal Food and Drug Administration to determine that no threat to human welfare could possibly result before approving the use of high-energy radiation to preserve foods.
With agricultural products stored dry, such as grain, tobacco, and wool, the chief agents of damage are not microbes, but insects. The loss of stored field crops caused by insects is estimated at $200 million annually in the United States. ”

“ In agriculture, as in all areas of research, the number of questions to be asked of Nature seems infinite. Future generations seeking to answer these questions will probably rely more on techniques using radioactive isotopes than on any other methods known today. ”

“ Plant Nutrition and Metabolism
Most studies of plant nutrition and metabolism pertain to the following questions. What do plants need for their best growth? How do they take in the materials they need? What things are absorbed by roots and what things by foliage? How does the plant turn water and other simple compounds into carbohydrates and proteins?
Specific problems that atomic energy has helped to solve are listed.
What Happens to Fertilizer in the Soil?
Early research indicated that only 10 to 12 per cent of phosphorus fertilizers was taken up by plants in the first year ”

“ The first traces of man on the earth are dated at about one and three-quarter million years ago. Plant life then was very much like plant life today, but the animal population was quite different. Man became a producer of plants and animals instead of merely a gatherer and hunter about 8000 years ago. He has applied systematic study to cultivated plants and animals for only 300 years.
Research in the United States
Estimates of crop losses in the United States each year are approximately $5 billion to weeds, $4 billion to insects, and $3 billion to diseases. ”

“ All plants readily absorb selective weed killers (“herbicides”) , which are not destroyed within the plants. Resistant 11 plants show no effect of the chemicals, but sensitive plants suffer damage in actively growing roots and shoots. Sugar formation during photosynthesis is disrupted in these plants, and phosphorus movement is retarded. In order to predict what new classes of chemicals might be of value as herbicides, we must await the results of research using radioactive tracers. ”

“ Radioactive atoms are not used directly by farmers but are used in research directed by the U. S. Department of Agriculture and Atomic Energy Commission, by the agricultural experiment stations of the various states, and by numerous public and private research institutions. From such research come improved materials and methods which are used on the farm.
In more highly developed countries agricultural research has brought a shift of emphasis from production to utilization. In the United States today, each farmer produces enough food for himself and 25 other people. ”

“ Botanists have learned in recent years that the foliage of plants can take in some nutrients much as roots can. With tracers they discovered that many nutrients are readily taken up by foliage, including bark of dormant trees, even at temperatures below freezing. As shown by isotopic tracers, elements such as phosphorus, nitrogen, and potassium move both up and down from the point of application at rates similar to those following root absorption. ”

“ The physically unstable radioactive atom behaves chemically exactly like its stable counterpart until the instant it emits its radiation and becomes stable. For example, radioactive phosphorus behaves, biologically and chemically, like stable phosphorus until it emits a beta particle and becomes stable sulfur. ”

“ An ingenious application of atomic energy to agriculture concerns the screwworm fly, which inhabits large areas of southern United States, Mexico, and the Caribbean. The fly lays eggs in open wounds of livestock, including navels of newly born, and the burrowing maggots inevitably kill the animal. ”

“ In a typical instance a ration thought to have 24 per cent digestible calcium, chemically determined, was found to have 38 per cent by the tracer technique.
The tracer method shows that milk contains phosphorus, only 20 per cent of which may come from the feed and 80 per cent from the cow’s bones. With eggs, about 65 per cent of the phosphorus is provided by feed and 35 per cent by the hen. Radioactive tracers permit measurement of such “biological pathways,” as the biochemist calls them.
Can Lean Meat be Estimated “on the Hoof”? ”

“ With radioactive phosphorus-32 scientists found that as much as 50 to 70 per cent of the phosphorus in a plant came from the fertilizer during the first two or three weeks of growth.
Do Plants Absorb Through Roots Only?
Fertilizer applied to soil is largely wasted because it is either bound by soil particles or is washed out of the root 5 zone. If chemical elements could go directly into leaves and bypass the wastefulness of soils, a tremendous saving would result. ”

“ Although the claims of over-enthusiastic gardeners and seed dealers about astonishing new plants “created” by atomic radiation are doubted, clear proof exists even in the restrained scientific journals of hereditary changes caused by radiation. ”

“ The animal is fed a test ration containing no added radioactivity. At intervals of a week or more, the animal is weighed and is also tested for natural radioactivity. Weighing tells total gain, while radiopotassium counting shows how much gain is in the desired lean meat. This method is remarkably simple, and since no radioactivity is added to its diet, the animal can still be marketed.
Does Thyroid Affect Milk—Egg Production? ”

“ With tracers it is possible for the first time to measure chemical uptake in single spores and to follow chemicals through the plant. Perhaps the most enlightening information from such studies is that some fungicides are 10,000 times less effective per unit of “body weight” than are other chemicals used to destroy weeds and insects. Obviously the breakthrough in chemical control of plant diseases is yet to come.
10 Why Do Chemicals Destroy Some Plants?
Weeds cost this country an estimated $5 billion annually, which is more than the loss to either plant diseases or insects. ”

“ Although plants are bred to resist the pathogen (fungus) of the moment, Nature is constantly changing the microbial population by mutation and hybridization. Within a few years virulent strains of fungi which can attack the “resistant” variety increase to such an extent that the new variety must be replaced. ”

“ In an effort to reduce these losses and to raise the standard of living, agricultural research has become more specialized and more complex. Over the years it has gradually changed from trial-and-error attempts to increase production to the actual study of basic questions. ”

“ In this country today plant diseases result in losses estimated at $3 billion a year. So far, the most economical means of reducing the ravages of plant diseases has been to breed resistant plant varieties. ”

“ With tracers the answer may be found in a few days. A plant is injected with radioactive phosphorus; after a few days its pollen is highly radioactive. Flowers at various distances from the tagged plant may be checked daily for radioactivity. In one study with alfalfa, radioactive pollen was carried as far as thirty feet by bees, but more than 16 one-third was deposited on plants adjacent to the labeled one.
Are Predators Used to Destroy Insects?
With insect pests, as with plant diseases, biological control is more economical than artificial control. ”

“ It may be that a dairy breeder can soon select calves for potential milk production because of thyroid activity as measured by radioactive iodine. At present he must let the animals grow and produce milk for several years before he chooses those to use in herd improvement. ”

“ Today a sort of double-barreled radiation method can be used to measure these two soil characteristics.
Neutrons are readily scattered by water but not by soil; gamma rays are absorbed by both soil and water. In practice the experimenter drills two holes in the soil a few feet apart. Into one he puts a gamma-ray source ”

“ These animals are mammals with simple stomachs and have the same general size, shape, and placement of organs as do humans. Radiation studies with swine and burros, although slow and expensive, should give information more applicable to humans than the more rapid and inexpensive studies with small laboratory animals. ”

“ Tritium can now be used by health officials to study the effects of tranquilizers.
15 Insects Where and How Fast Do Insects Travel?
Radioactive isotopes have been used to study insects, their life cycles, dispersion, mating and feeding habits, parasites, and predators. Several hundred such studies have been made on dozens of insect species.
With radioactive tracers even the smallest insect becomes more easily followed. As one example, nearly half a million mosquito larvae were tagged with radioactive phosphorus in Canada. ”