IV SELECTION OF PASTURE PLANTS 37 



Theory of Selection 



Necessity for Selection. — The varying characteristics of fodder plants 

 are of the utmost importance from an agricultural point of view, since many 

 varieties endure for years, others only for brief periods ; some luxuriate on 

 moist or clayey soils, some in light, dry situations, and yet others only where 

 the subsoil is deep and permeable ; many form erect tufts alone, some 

 produce creeping and rooting stolons, either under or above the surface of 

 the ground, and others still, wholly or partially decumbent stems ; and while 

 some start into growth rapidly after being mown or depastured, so yielding 

 several crops in a season, others again give but a single cutting a year. 

 Many additional and equally striking variations exist, but sufificient have been 

 mentioned to render it obvious that the judicious selection of varieties, or 

 composition of mixtures, for any particular soil or purpose must be founded 

 on an accurate knowledge of the growth, requirements and peculiarities of 

 the pasture plants. 



Design in Selection. — The object of selecting pasture plants should be 

 to form a complete sward, which will yield the greatest possible, most certain 

 and sustained annual produce of palatable food for a desired period. 



Duration of Varieties. — The intended duration of a pasture is an 

 important guide to the selection of the most suitable fodder plants ; and each 

 mixture should be principally composed of varieties which naturally endure 

 for the contemplated time. 



Soil and Climate. — A judiciously composed mixture must contain only 

 those species which may reasonably be expected to thrive under the proposed 

 conditions of soil and climate, since most fodder plants become unproductive 

 or die out altogether amidst uncongenial surroundings. 



Habit of Growth. — Many pasture plants, especially simply tufted 

 grasses, are incapable of forming a complete covering for the ground ; and to 

 prevent indigenous weeds springing up between, and possibly suppressing, 

 them, suitable proportions of creeping or stoloniferous species must be added 

 to form " bottom-herbage " and occupy every vacant space. While the 

 finely-growing grasses usually root only in the surface vegetable-soil, taller 

 kinds penetrate deeper, and leguminous plants, which also possess, the power 

 of assimilating and storing up free nitrogen from the atmosphere, send down 

 central tap-roots deep into the subsoil in search of the necessary minerals 

 and water. Fraas says that leguminous roots can penetrate to the following 

 depths: — White clover, 6 inches; Red clover, 25; Lucerne, 50; and Sain- 

 foin from 37 to 150. Thus, it becomes evident that the available elements of 

 plant-growth can only be fully taken advantage of when a pasture contains 

 proper proportions of large and small grasses and leguminous plants. 



Development and Yield. — While some fodder plants vegetate early in 

 spring and yield their principal produce at the first cutting, others grow until 

 late autumn, and provide abundant aftermath ; and different varieties attain 

 to their maximum development at widely varying periods after being sown ; 

 so that a well arranged mixture must include early and late plants and some 

 developing fully the first, and some the second, year, thus ensuring a profitable 

 return from the first season onwards. 



Calculation of Mixtures 



Purity and Germination. — By percentages of purity and germination 

 are understood the numbers of pure and of germinating seeds respectively in 



