16 JAMESTOWN CONGRESS OF HORTICULTURE 



organic matter must be secured through deep plowing which aims to 

 turn all waste refuse and occasionally green and stable manures. Go- 

 ing with this practice there must be an intelligent rotation of crops 

 which includes the legumes, to accumulate nitrogen from the air, and 

 to fix it deeply in the soil in their tubercle and root growth ; which 

 includes the grasses having dense root systems tending to both deeply 

 and finely divide the soil by the close ramification of their roots and 

 to make the granules so formed more rigid by the cementing action 

 of substances rendered soluble by the carbonic acid transpired through 

 their roots and which accumulate in the granules by diffusion to become 

 precipitated there as the soil is deeply and thoroughly dried by the 

 action of the roots in supplying the plant with water. The cereal, 

 vegetable, fiber and sugar crops exert but a feeble structure-building 

 effect upon the soil. They tend rather to weaken soil structure by the 

 removal of the soluble plant food ingredients which have accumulated 

 there, thus rendering it both structurally defective and deficient in 

 immediately available plant food. These last crops, therefore, make 

 chiefly the financial earnings while the grasses and legumes are largely 

 restorative but may be earning crops as well. It must be remembered, 

 however, that their restorative effect lies wholly in their power to 

 mend structure and in adding the single element nitrogen to the soil. 

 Other plant food elements they never add but may, to some extent, 

 help to make them more available and thus permit larger yields to 

 follow them, but whose removal, when no return is made to the soil, 

 hastens its ultimate exhaustion. 



Composition, first, and structure, second, are the master factors 

 which determine the productive capacity of fields. Let me close by 

 illustrating this through the practice of composting soils preparatory 

 to their use on the benches of forcing houses. With the practical man 

 his first choice is a rich sod, his second a rich mellow loam. To the 

 soil he adds from a third to a half its volume of good stable manure, 

 perhaps supplemented with phosphates, lim'e and potash. The whole 

 is thoroughly mixed, put in good moisture condition and given oppor- 

 tunity for fermentation under conditions of frequent turning. By this 

 treatment he secures a soil whose structure is ideal and which is at 

 the same time carrying a heavy charge of plant food in highly avail- 

 able form. A strong blue-grass or timothy sod is itself a guarantee 

 of thorough and strong crumb structure. Because the volume of the 

 soil is small it is imperative that the root system be brought in effec- 

 tive contact with the whole of it, that the available surface shall be 

 as large as possible and that the soil with which the roots come in 

 contact shall be heavily charged with essential plant food. The 

 decay of the manure in contact with the soil grains leads to their 

 becoming highly charged with plant food in water-soluble form. 

 Quite likely, too, at the time of planting, the manure and other sub- 

 stances will be supplemented by sodium nitrate. 



It seems idle to think that soils like this, selected at the start 

 because they are in evident good condition and reasonably productive, 

 should require such excessive amounts of manure and fertilizers to 



