456 THE MONTHLY BULLETIN. 



COVER CROPS IN CITRUS CULTURE.* 



By C. S. Vailb, Claremont, Cal. 



In all lines of industrial activity the present times demand increased 

 economy and efficiency. The pertinency of this demand has been less 

 recognized in the farming industry than in others, where competition is 

 more keen, and machinery more potent. But the citrus grower is now 

 awakening to the urgency of this study. 



The citrus industry in the future, to be remunerative, will demand 

 the truest economy along every line. While a few may be able to 

 indulge in citrus culture simply for the esthetic effects, the majority of 

 the growers must live off the financial returns of its investment. 



Owing to the increased acreage set to trees, the cost of labor, trans- 

 portation and taxation, and the many ills citrus groves are heir to, the 

 orchardist will be compelled to obtain the largest results at the minimum 

 cost. Then, too, if California is long to continue as a Garden of the 

 Lord and the Mecca of the world its soil values must be conserved and 

 improved. 



COVER CROPS AS FERTILIZERS. 



AVhile other factors are to be considered in studying this economy in 

 citrus culture, the question of grove fertilization, as being one of its 

 most costly factors, is of vital interest to the orchardist. Of the 

 elements needed to increase soil fertility the most essential is nitrogen. 

 Whether this is added through barnj^ard or commercial fertilizer its 

 test increases with the growth of the orchard. 



This costly unit in fertilization can be supplied by certain kinds of 

 cover crops more cheaply than in any other way. This incorporation of 

 green organic matter in the soil is called green manuring, and we hope 

 to show that certain kinds of such matter constitute one of the most 

 important factors in soil fertility. 



Certain plants — the legumes — not only yield large amounts of organic 

 matter but also possess the power of gathering from the air in the soil 

 this costly element of plant food — nitrogen. 



These legumes, or nitrogen-producing plants, include among others 

 the peas, beans, vetches, alfalfas, clovers, fenugreek and the lupines. 

 This large variety of plants gives room for much choice and many 

 experiments and the rancher should become acquainted with the relative 

 value of each. Out of ten thousand species of legumes some two hun- 

 dred are now cultivated and others may be proven to be of value; yet 

 doubtless a few of the plants will be found sufficient for the desired 

 results. 



AVhile this chemical effect of the leguminous cover crop is its chief 

 worth, it is far from being the only value of green manuring. Besides 

 producing available nitrogen, cover crops give to the soil a moisture- 

 holding condition and permanently increase — if we may use an ill- 

 defined word — the humus of the soil. They shade the ground and set 

 free and make soluble the available minerals, potash and phosphoric acid 

 which, if thus liberated, may in some soils be sufficient for orchard 

 growth and fruitage. 



♦Address before State Fruit Growers' Convention, Palo Alto, Cal., .July 29, 1915. 



