10 



AGRICULTURAL HANDBOOK 395. U.S. DBPT. OF AGRICULTURE 



pose of treating farmland after contamination 

 with widespread fallout would be to reduce up- 

 take of fission products by plants. 



Removal of Crops and Mulches 



The presence of a crop would affect the choice 

 of treatments for a contaminated area. A heavy 

 crop would intercept part of any contaminating 

 material that was deposited from the air, such 

 as fallout. Thus, removal of the crop would 

 partly decontaminate a land area. However, crop 

 removal would generally be inadequate. In some 

 cases, crops might have to be removed before 



other, more effective treatments could be carried 

 out. 



The feasibility ratings of methods for remov- 

 ing crops and mulches are summarized in table 1. 

 Most common types of crop-liarvesting nuichinery 

 are compared on crops ranging from meadow to 

 full-grown corn. 



With one exception, none of the methods re- 

 moved more than 75 percent of simulated fallout 

 from a contaminated area. The exception is that 

 taking off a heavy mulch of wheat straw gave 

 good decontamination. This test was run with 

 liquid droplet contamination, which apparently 

 adhered to the straw. Dry fallout contamination 



Table 4. — A coinparison of soil management methods for reducing strontium-90 uptake from 



contaminated soils. 



Method 



Reduction in 

 Sr-90 uptake' 



Effort 

 required ' 



Effect on soil 

 productivity* 



Minimum tillage 



Plowing, 7" deep 



Plowing, 12" deep 



Plowing, 36" deep 



Plowing, 36" deep with 



root inhibition. 



Irrigation 



Leaching 



Lime application, 2 to 10 



tons/acre. 

 Nitrogen fertilizers, 



100# N/acre. 

 Phosphate fertilizers, 



100# P/acre. 

 Potassium fertilizers, 



500# K/acre. 

 Organic compost, 



5 to 20 tons/acre. 

 Clay minerals, 



.T to 20 tons/acre. 

 Ammonium or potassium 



phosphates, 2 to 5 tons/acre. 



Poor to fair Good 



Poor Good 



Poor Fair . 



Fair to poor Poor 



Good to fair Poor 



Poor Fair to good 



Poor Fair 



Poor to fair Good 



Poor Good 



Poor Good 



Poor Good 



Poor Fair 



Poor Fair . 



Fair Fair . 



-Good to poor. 

 -Good. 

 -Good. 



-Good to poor. 

 -Good to poor. 



-Good. 

 -Poor. 

 -Good. 



-Good. 



-Good. 



-Good. 



-Good. 



-Good to fair. 



.Fair to poor. 



'Rating of reduction in Sr-90 uptake: Good — > 95 percent reduction. 



Fair — 75 to 95 percent reduction. 

 Poor — < 75 percent reduction. 

 ' Rating of effort required : Good — Not significantly more than normal field practices. 



Fair — Extra equipment, materials, or labor required. 

 Poor — Very great requirement of equipment, materials, or labor. 

 ' Rating of effect on soil productivity : Good — Increases or does not change productivity. 



Fair — Reduces productivity < 20 percent. 

 Poor — Reduces productivity > 20 percent. 



