Old System of Intertillage . 159 



is that of using the rain which falls upon an acre of 

 ground to produce a crop on one -half of that same 

 area. For this, as a matter of fact, was the essential 

 thing which the Lois-Weedon system did. It is evi- 

 dent enough that in a country where the rain which 

 falls is only one -half the amount which is needed to 

 produce remunerative crops, if that water can be 

 brought to use on one -half of the area, then a fair 

 crop on one -half of the ground may reasonably be 

 expected. 



The important matter, then, is to devise a system 

 of planting for the various crops which shall permit 

 the rain which falls upon the unused area to be 

 brought within reach of the plants growing upon the 

 occupied ground. For all crops which are grown in 

 hills or in rows, like maize, potatoes, and various 

 vegetables, the problem is simple enough, as it resolves 

 itself into the single question of how many plants can 

 be matured upon the ground with the available water, 

 allowing for unavoidable losses. This fixes the dis- 

 tance between the rows and the distance between the 

 hills in the row. In countries, where there is an 

 abundance of water, or where irrigation is practiced, 

 plants may be brought so close together that the limit- 

 ing factor is amount of sunshine, or available plant- 

 food in the soil, or air about the plant ; but in sub- 

 humid regions, the limiting factor is water alone, and 

 the distance between plants must be made such, if 

 necessary, that the roots of one will not encroach upon 

 the feeding ground of another. 



The roots of the maize plant commonly spread 



