Discussion on Mr. Smith'' s Paper. 71 



properties naturally existing become dissolved, and thus afford plant 

 food where only water has been artificially added. Fertilizers are 

 divided into two classes — chemical and mechanical. The fiber and 

 coarse material in barn-yard manures act chiefly in a mechanical way, 

 by rendering the soil porous and permitting- the free passage of air 

 and water, both essential to the growth of plants. Your soil in 

 these California valleys can not become compact, owing to the 

 nature of its origin and composition. Prof. J. S. Newman, of the 

 Alabama experiment station, experimented as to the relative effect 

 of fertilizers and of mechanical manures used to render the soil 

 porous, and had found that, while there seemed to belittle difference 

 between the effect of one fertilizer and another while the soil was 

 heavy, the plants seemed to " leap up almost double" when it was 

 well drained and otherwise rendered porous, so that the air and 

 water could reach the roots. Both fertilizers and water, when op- 

 erating beneficially, acted as fluxes, loosening something that the 

 plant life needed. 



Prof. Klee, of California — Cereal crops take from the soil large 

 amounts of phosphates. A forest growth, in a state of nature, re- 

 moves but a small per cent, of plant food from the soil, as by its 

 decay the original elements are mostly returned. Summer fallow- 

 ing is growing in favor among California farmers. Grain fields, 

 that have been run down by long and constant culture, may be 

 greatly improved by allowing them to lie in fallow a single season. 

 Irrigation alone will not produce a productive soil. The orange- 

 growers of Southern California, who of necessity must irrigate, find 

 it necessary, also, to fertilize their lands. 



Prof. Husmann, of California — I hail from the Napa valley, 

 where irrigation is unknown, excepting occasionally for a few sum- 

 mer vegetables. Grain has been grown on the bottom lands twenty- 

 six to twenty-eight years without intermission, and good crops 

 raised with very slovenly culture, half the valley being merely 

 scratched with the harrow and left for " volunteer" crops, which 

 yielded five tons of hay to the acre. When oaks of six feet in diam- 

 eter were seen growing there, we knew that something below must 

 sustain them. Last year I gathered five crops of grapes, commenc- 

 ing on September 15th and ending the first few days of December. 



