224 FUNDAMENTALS OF FRUIT PRODUCTION 



yielding returns greater than those obtained from commercial fertilizers 

 used in quantities carrying equal amounts of nitrogen. However, a part 

 of their beneficial influence is without doubt due to other nutrients that 

 they carry and to the effects on the physical condition of the soil. 



Thus Schreiner and Shorey/^" in discussing the physical condition of 

 the soil as affected by organic matter, state: ''The organic matter may, 

 and in fact generally does, play an intimate part in the behavior of the 

 mineral particles, entering into chemical combination, coating them or 

 cementing them together. The organic matter becomes, therefore, of 

 the greatest importance in its influence on the great controlling factors in 

 crop production, such as the solubility of the soil minerals, the physical 

 structure of the soil granules, and the water-holding power of soils. To 

 illustrate this, there was found in California a soil which could not be 

 properly wetted, either by rain, irrigation, or movement of water from 

 the subsoil, with the result that the land could not be used profitably 

 for agriculture. On investigation it was found that this peculiarity of 

 the soil was due to the organic matter, which when extracted had the prop- 

 erties of a varnish, repelling water to an extreme degree. The soil, 

 once freed of this ingredient, had a high water-holding power." 



Some suggestion of the many ways, direct or indirect, in which organic 

 matter affects tree growth and production may be derived from the follow- 

 ing statements pertaining to the rosette of pecans: "The experimental 

 and other evidence indicates very strongly that pecan rosette is a sign of a 

 soil deficient in humus, fertihty, and moisture supply, . . . The 

 constant addition of large quantities of humus-forming materials, thereby 

 both bettering the physical condition of the soil and increasing its water- 

 holding capacity and fertility, is absolutely necessary to produce healthy 

 trees from those already diseased and to prevent the development of 

 new cases of rosette. . . . some consistent and definite soil-building 

 policy should be adopted in the pecan orchards of the South if rosette 

 is to be overcome and healthy productive orchards maintained. The 

 program of work should involve the growing of one crop, preferably a 

 legume, which may be returned to the soil. ... In these experiments, 

 heavy applications of stable manure, cottonseed meal and stable manure, 

 and cottonseed meal alone, in connection with legumes, have proved 

 highly beneficial to rosetted trees." ^^^ Though in cases like this it is 

 impossible at present to distinguish between the influence of the nitrogen 

 and that of the other components of the organic matter there is no reason 

 for minimizing their combined effects or for failing to resort freely to the 

 use of organic fertilizers in orchard practice where observation and experi- 

 ence indicate that they may be of decided benefit. The nitrogen of 

 organic fertilizers is more slowly available than that of the common 

 nitrogenous commercial fertilizers and experience shows that for quick 

 results the commercial sources are more satisfactory. Investigation 



