LEGUMES AND GRASSES 



55 



gen loss was 18 percent. Losses of 

 organic carbon and nitrogen from 

 the 6- to 12-inch depths were small 

 as compared with the original con- 

 tent. Losses were comparable with 

 those reported by Haas and co- 

 workers (27) for the U.S. northern 

 Great Plains. 



Newton and coworkers (62) cal- 

 culated that one-third to one-half 

 of the nitrogen lost from the surface 

 6 inches of cultivated soil in the 

 Brown, Dark Brown, and Black soil 

 zones was removed by crops. Grain 

 and fallow rotations carried on for 

 25 to 30 years at Lethbridge and 

 Indian Head resulted in large losses 

 of organic carbon and nitrogen. 

 Comparable rotations that included 

 legumes or legumes and grasses and 

 barnyard manure caused smaller 

 losses of organic carbon and nitro- 

 gen. 



The value of sweetclover as a dry- 

 land green-manure crop has been 

 studied at Lethbridge, Alberta, for 

 30 years (6). On fallow, wheat, 

 wheat rotations, average yield of 

 fallow wheat was higher from clo- 

 verless fallow than that where clover 

 fallow was used. Average yields of 

 second-year wheat were almost 2 

 bushels per acre higher from rota- 

 tions that included clover than from 

 those that did not include clover. 

 During years of good moisture, this 

 difference was more than 2 bushels. 

 The average yield of wheat after 

 clover fallow was much higher 

 where the clover was plowed for 

 fallow before May 15 than where 

 plowing was delayed until after the 

 clover was more mature. 



Chemical and Physical Effects of 

 Legumes and Grasses on Soils 



Lehane and Staple (45) investigat- 

 ed the effects of crested wheatgrass 

 on^ physical and chemical charac- 

 teristics of soil. This investigation 

 was to determine the beneficial 

 effects of a large-scale regrassing 



program that had been carried out 

 in the Brown soil zone of western 

 Canada from 1937 to 1942. Crested 

 wheatgrass had germinated and sur- 

 vived better than other grasses and 

 had proved to be a relatively effi- 

 cient user of moisture under dry 

 conditions. Coarse-, medium-, and 

 fine-textured soils were sampled. 

 Composite samples to a depth of 6 

 inches were taken from crested 

 wheatgrass sod and from nearby 

 cultivated land. Effects of crested 

 wheatgrass on seven soil properties 

 were tabulated (table 38). 



The data indicate that crested 

 wheatgrass had beneficial effects on 

 coarse- and medium-textured soils. 

 Decomposed and undecomposed sod 

 samples showed a large increase in 

 field capacity, a smaller increase in 

 permanent wilting point, and a net 

 increase in available moisture- 

 holding capacity. Bulk density 

 was decreased and carbon and nitro- 

 gen increased. The authors sug- 

 gested that part of the organic 

 carbon increase and most of the 

 nitrogen increase may have been 

 caused by soil drift material blown 

 onto the sod land. Grass increased 

 dry aggregation of coarse-textured 

 soils and increased both the dry and 

 wet aggregation of medium- 

 textured soils. Fine-textured soils 

 showed little benefit from the grass. 



Stevenson and White (77) studied 

 root production of several perennial 

 grasses at Saskatoon, Saskatchewan. 

 Two objectives of the study were to 

 determine the relative root produc- 

 tion of slender wheatgrass, crested 

 wheatgrass, and bromegrass and the 

 time required for satisfactory res- 

 toration of root fiber to a cultivated 

 soil. All three grasses increased 

 root production each year for 5 

 years. Five-year stands of crested 

 wheatgrass added more than 3 tons 

 of roots per acre, which was about 

 one-half the quantity of roots 

 present in native prairie soil. Root 

 yields of bromegrass and crested 



