GRASS-LAND AND ARABLE 125 



he waits till the herbage affords practically no keep 

 that is to say, till the clover has died out and the 

 sward is little but Bent, and thus at once fouls his 

 arable land and loses the fertility he should have 

 assured for his subsequent crops. 



I now come to what are scientifically perhaps the 

 most interesting problems connected with the tem- 

 porary ley, namely, how to establish a sward quickly, 

 and how to make it uniformly productive over the 

 whole of its existence. The pioneers on herbage 

 questions concerned themselves to find out what 

 species qua species had the greatest nutritive value, 

 under what soil conditions these species qua species 

 flourished, and at what season of the year these 

 species qua species matured. All this they ascer- 

 tained, and to the lasting benefit of agriculture. They 

 proceeded to argue, however, that the selection of a 

 seed mixture then became a mathematical problem 

 pure and simple: you wanted so much ground 

 covered with top grass, so much with bottom grass, 

 such and such a proportion of early species, a proper 

 proportion of mid-season and late-maturing species, 

 and there was the basis of your seeds mixture; and, 

 provided you knew the germination of your seed 

 and the approximate number of seeds to the pound, 

 a sliding scale would do the rest. But, unfortunately, 

 there are other factors affecting the problem not yet 

 capable of mathematical solution. What, for instance, 

 is going to be the competitive interaction between the 

 species you sow? How is it all going to be affected 

 by those indigenous species which have a knack of 

 springing up naturally? And, furthermore, what of 

 the antecedents of the seed of the desired species you 

 sow where has the seed come from, and is it really 

 going to succeed and fill up its allotted portion of 

 ground? 



