12 



AGKICULTURAL HANDBOOK 395, U.S. DEPT. OF AGRICULTURE 



ductivity of the treated area requires improve- 

 ments in the physical structure and in the nu- 

 trient supply of the remaining soil. xVdditions 

 of lime, fertilizers, manure, and mulches help to 

 restore ])roductivity. 



Decontamination in Cold Weather 



Subfreezing weather and the possibility of 

 snow cover exist for part of the year on large 

 acreages of farmland in the United States. In 

 cold weather, the removal of surface contamina- 

 tion would usually be more difficult tlian in warm 

 weather. If the soil surface were frozen, it could 

 not be removed by scraping. Vacuum or sweep- 

 ing machines might be useful unless the con- 

 taminant had been frozen into the surface. 



A snow cover would present different problems, 

 depending on whether the contaminant was be- 

 neath it, mixed with it, or deposited on top of it. 

 In the first case, the snow cover would have to 

 be removed before the contaminant on the soil 

 surface could be treated. If additional hazard 

 would be created by contaminant carried in the 

 runoff' from melted snow, it might be desirable 

 to remove the snow cover in spite of the extra 

 effort required. In case the contaminant was in 

 or on top of the snow, the area could be decon- 

 taminated by removing only the snow. However, 

 the presence of crop residues in the snow cover 

 would interfere witli snow removal and could 

 seriously reduce the effectiveness of decontam- 

 ination. 



Studies on the decontamination of land that 

 was frozen or covered with ice or snow have been 

 made by the U.S. Army Nuclear Defense Lab- 

 oratory (£3). Feasibility ratings derived from 

 their data are given in table 3 for methods that 

 may be applicable under some farmland condi- 

 tions. 



Several methods removed 75 percent or even 

 95 percent of the contaminant that had been 

 deposited on the snow or ground surface. Since 

 tests were carried out at varying temperatures 

 and textures of the snow, differences between im- 

 plements in effectiveness of removal of radio- 

 activity may not be significant. Tlie texture of 



the snow, which varied with the recent temper- 

 ature history, affected the removal of radio- 

 activity. 



Tlie effort required for removal of radioactive 

 contaminants in cold weather was not excessive 

 under the conditions of the tests, which were 

 run on paved or smooth ground areas. On rough 

 land areas, the rate of ti'avel would be much 

 slower. A longer time would be required for 

 decontamination in such circumstances, even as- 

 suming that the snow cover permitted effective 

 decontamination. 



Ratings for disposal effort are based on the 

 weight of materials to be moved, and whether 

 or not an extra loading operation would be nec- 

 essary. However, the disposal of contaminated 

 snow could be very difficult because of its great 

 bulk. It should be piled so that the contaminant 

 would not spread by wind, rain, or runoff from 

 melting snow. If one could let the snow melt 

 while retaining the contaminant, there would 

 be much less material for disposal. 



No effect on soil productivity would be ex- 

 pected from snow removal, and removal of thaw- 

 ing ground should have an effect comparable to 

 that of removal of surface soil. 



No-tillage Management 



Wliere the soil surface contains most of the 

 radioactive contamination, its uptake by crops 

 could be lessened by growing deep-rooted crops 

 under conditions of no-tillage. The feasibility 

 of no-tillage management has been established 

 for economic production of certain crops {5), 

 but its possible usefulness as a treatment for con- 

 taminated land has not been established. It would 

 have the advantage of keeping the radioactive 

 material mostly on the surface, where it could 

 later be removed or otherwise treated. Estimated 

 feasibility ratings for no-tillage management are 

 given in table 4. 



Deep Placement of Contaminated Soil 



Contaminated surface soil may be buried by 

 plowing. With common farm tractors and plows, 

 the depth of plowing is limited to about 12 inches. 



