LEGUMES AND GRASSES 



57 



Table 39. — Losses of organic matter and nitrogen from virgin and cultivated 

 soil of 2 types, with and without residue, during 5 years of pot culture, 

 Swift Current, Saskatchewan, 1954 l 



Soil 



Loss in organic 

 matter — 



Without 

 residue 



With 

 residue 



Loss in nitrogen — 



Without 

 residue 



With 

 residue 



Wood mountain clay loam: 



Virgin 



Cultivated 



Sceptre clay: 



Virgin 



Cultivated 



Percent 

 26.9 

 21.6 



16.9 

 12.4 



Percent 

 20.3 

 17.7 



12.8 

 9.3 



Percent 

 23.2 

 21.3 



21.4 

 21.3 



Percent 

 19.4 

 17.9 



20.1 

 15.4 



Data from (5). 



crops at Lethbridge, Alberta, in the 

 Chestnut soil zone and at Swift 

 Current, Saskatchewan, in the 

 Brown soil zone. 



On Chernozem soils at Indian 

 Head, Saskatchewan, and Brandon, 

 Manitoba, legume-grass rotations 

 produced higher yields than straight- 

 grain rotations in a 10-year period. 

 Nitrogen fertilizer also increased 

 grain yields, but there is insufficient 

 data to indicate whether or not 

 nitrogen would substitute for leg- 

 umes and grasses in rotation on 

 Chernozem soils. 



Cropping caused substantial ni- 

 trogen and carbon losses. Legumes 

 and grasses in rotations reduced but 

 did not eliminate these losses. 



Yields of fallow wheat have not 

 declined with years of cropping on 

 Brown, Dark Brown, and Cher- 

 nozem soils. Yields of continuous 

 wheat have declined to some extent 

 in the more humid areas. Part of 

 this decline was attributed to weed 

 problems. 



In 1954, Hill (80) concluded that 

 the wheat, summer fallow system 

 of cropping can profitably be con- 

 tinued in Western Canada for 

 many years provided erosion and 

 weeds are controlled. 



In southwestern Saskatchewan, 

 crested wheatgrass increased the 

 water-holding capacity, carbon and 

 nitrogen content, and aggregation 

 of coarse- and medium-textured 

 soils. Grass had little effect on 

 fine-textured soils. 



At Saskatoon, Saskatchewan, a 

 5-year stand of crested wheatgrass 

 added more than 3 tons of root 

 fiber to a cultivated clay loam soil. 

 This restored soil structure to a 

 satisfactory condition. Duration 

 of this effect after the grass was 

 plowed was not reported. 



The addition of crop residues to 

 soil in pot cultures reduced losses 

 of organic matter and nitrogen. 

 The authors postulated that similar 

 benefits would occur under field 

 conditions. 



