24 THE WALNUT — PLANTING, SOIL, ETC. 



years, and are only prevented from putting forth growth by being under 

 ground. While the theories advanced are logical, and be the causes 

 what they may, success can only result where precision is applied. In 

 places where roots remaining in the ground have caused trouble, the 

 growers have found that it is best to let the oaks stand, and plant trees, 

 around them. They are headed back to prevent too much shade, but as 

 they continue growing the roots do not interfere with the growth of the 

 , orchard trees. 



SOIL EXHAUSTION THROUGH THE CULTUEE OF THE WALNUT, AND FEBTILIZEES 



TO USE, ETC. 



By Pbof. S. M. Woodbbidge, Ph.D., Agricultural Chemist, Los Angeles. Prepared 



by special request. 



The walnut crop is involved in more or less mystery, and is little 

 understood in the abstract, or from a chemical standpoint, although 

 from a practical standpoint the matter of maintaining the original 

 integrity of the soil, and in fact the building up of a poor soil, is well 

 understood and readily accomplished. 



To give an illustration, let us look at the orange. In an orchard in 

 the San Gabriel Valley the soil analyzed 1.14% in potash. Taking the 

 soil to a depth of only 2 feet, an acre of ground would contain about 

 100,000 pounds of potash; this potash would be enough to supply an 

 annual crop of 20,000 pounds of oranges for more than 2,000 years; the 

 figures from which the above conclusion is drawn are taken from the 

 report of the State Analyst. Before the orchard was fifteen years old, 

 it showed marked signs of degeneration. The practical application of 

 potash in conjunction with nitrates and phosphates, some five years 

 ago, revived the orchard, and the annual application of a complete 

 fertilizer has since kept it in a most flourishing condition. 



Again, it is a well-known fact that in new ground, suited to the pur- 

 pose, from 400 to 500 bushels of potatoes can be raised the first year; 

 the second year scarcely one half that amount can be raised, and the 

 third year the field would hardly give its seed back; and yet the soil of 

 such a field would analyze practically the same at the end of the period 

 as it did at the beginning. Nevertheless, the soil is exhausted from the 

 practical standpoint of the farmer, that is, he cannot raise a paying 

 crop of potatoes; and yet from the standpoint of the chemist the soil is 

 as rich in plant-foods as ever — the little that would have been with- 

 drawn by three such crops, as are above described, being only the ten 

 thousandth part of the plant-food in the soil. 



What is true in regard to the exhaustion of the soil by an orange or 

 potato crop is also found to be true in practice in regard to the walnut. 



Chemical science has settled the fact that nitrogen, phosphoHc acid, 

 and potash are the only three expensive elements that any soil is likely 

 to become deficient in; therefore, as a general rule, those are the only 

 elements that must be added in order to do everything that is known to 

 science in order to properly feed any crop. In order, however, to make 

 these elements, when applied, most effective, the soil must contain a 

 sufficient amount of humus (decomposing vegetable or animal matter). 



It is a well-known fact that the best results are attained in horticul- 

 ture where circumstances admit of a rotation of crops, the same cfop 

 not being reached oftener than once in four or five years. In an orchard 



