PLUTONIUM CONTENTS OF FIELD CROPS 385 



5°C in winter; average precipitation is 140 cm, with 10 cm of snowfall. Winter and 

 summer temperature variations tend to be greater at Oak Ridge than at SRP. 



Methods 



Savannah River Plant 



Pine trees were bulldozed from the old fields and bushes and herbaceous vegetation were 

 cut with a tractor-drawn rotar>' mower to prepare the land for crops. All debris, including 

 tree roots, was removed before any operation. The fields were disked with a bush and 

 bog disk harrow, then with a standard disk harrow, subsoiled, redisked, limed, redisked, 

 fertilized, and, finally, redisked. The disking was done to a depth of about 20 cm. 

 Agricultural Hme (consisting of 60% CaCOg, 25% MgCOg, and 15% H.O by weight) was 

 added at tlie rates of 908 kg on the South Field and 590 kg on the North Field. 

 Mixed-grade fertihzers were added at rates of 318 kg of 3-9-18* and 227 kg of 

 5—10—15 for the South and North fields, respectively. The South Field was divided into 

 18 equal plots, and the North Field, into 12 equal plots. 



Wheat (variety Coker 68-19) was sown on the fields by hand in November 1974 at the 

 rate of approximately 53 kg of seed per field. The seeds were then covered by disking the 

 fields at a very shallow depth. Foliage samples were collected in March and April. At 

 harvest in June, plants were separated into grain and straw. Wheat-grain samples were 

 obtained by two techniques. The first technique was to carefully collect wheat heads by 

 hand from each of the 30 plots and separate the grain with a laboratory thrashing 

 machine. This machine was carefully cleaned between samples from each plot to 

 minimize the amount o{ dust that would adhere to the grain. The second technique was 

 to harvest the grain with a tractor-pulled combine. Grain collected by this method was 

 exposed to the usual soil and dust stirred up by harvest activities. Total biomass for the 

 crop (grain plus hull plus straw) was estimated at 3615 and 3545 kg/ha for the South and 

 North fields, respectively. Wlieat was also grown 37 km from the reprocessing plants as a 

 control. 



The fields were prepared for soybeans by disking them several times and adding 

 mixed-grade fertilizer (3—9—18) at the rate of 227 kg for each field. Inoculated soybeans 

 (variety Bragg) were planted in July 1975 with a two-row planter; about 27 kg of seeds 

 was used for the two fields. The crop was harvested with a combine in November 1975. 



The fertilizer-addition and field-preparation techniques for the corn crop were similar 

 to those for soybeans. Field corn (variety Coker) was planted in May 1976 with a 

 two-row planter and harvested in October with a combine. 



The chronic releases of plutonium-bearing particles at low levels from the emission 

 stack make it impossible to determine the plutonium uptake by the crops from the soil 

 through the root pathway. Whatever amount of plutonium is translocated to the plant 

 foliage from the soil would be obscured by external deposition and retention from stack 

 fallout. Therefore glasshouse studies were conducted to determine the amount of 

 plutonium translocated to the aerial portions of the plants from the soil. 



'3-9-18 refers to 3% elemental nitrogen, 97o P^O. , and 1 87r K^O, respectively. 



