ch. x] Seed-Mixtures 169 



(1) Rapidly maturing species can be sown with those perma- 

 nent kinds which are naturally slow of development. In this way 

 the ground can be quickly covered, weeds largely excluded, and 

 crops secured from the first ; whilst the permanent sorts gradually 

 come forward and occupy the place of the short-lived kinds as 

 the latter die out. (See Diagram on p. 170.) 



(2) Generally speaking, the larger the variety of plants 

 associated, the greater the number of individuals that can grow 

 on a given area. Tall and low-growing plants, tufted and creep- 

 ing forms, can be associated with advantage as regards yield, etc., 

 and the surface can be more evenly and densely covered by a 

 mixed vegetation. 



(3) Species which vegetate early can be associated with those 

 which are more prominent at later periods of the season. 



(4) Leguminous plants — on account of the nitrogen fixing 

 bacteria contained in their root-nodules — can be associated with 

 grasses to the great advantage of the latter. 



(5) A mixed vegetation gives more regular and certain crops 

 than a simpler type. In abnormal seasons, though some of the 

 species may suffer others will probably be favoured. 



The making up of such mixtures is a matter which requires a 

 considerable amount of experience and care. Probably on no other 

 subject directly connected with practical farming has such widely 

 differing views been held. This has been so — partly because of 

 the lack of carefully conducted experiments, and partly because 

 of the almost infinite variety of soils and climatic conditions, to 

 say nothing of other variable factors. By some it has been held 

 that the selection of species for the formation of grass land is 

 almost a matter of indifference since the soil and after treatment 

 will ultimately determine the character of the turf produced; 

 whilst others have advocated a rigid selection of species for each 

 geological formation, and in strictly definite proportions, as if the 

 ultimate results could be secured by careful calculations beforehand. 



Whilst such slavish adherence to a particular mixture for a 

 given type of soil is quite unnecessary, it is equally foolish to be 

 indifferent in the choice of species to meet a given set of circum- 

 stances. Our object is to obtain a much larger yield of more 

 valuable produce than would be obtained if nature were left to 



