350 



HORTICULTURE. 



September 12, 1908 



renewed. Of these latter elements sul- 

 phur may be omitted, as it, like some 

 other elements of minor importance, 

 is usually found in sufficient quantity. 

 Of these substances tin- most expen- 

 sive and at the same time the most 

 evanescent, is nitrogen. The soil will 

 not hold it; it is here today and there 

 tomorrow. It is inordinately fond of 

 fresh fields of activity, and so impa- 

 tient of confinement that it has to be 

 constantly kept at work, and watched 

 lest it escape into the atmosphere 

 from whence it came, or enter into 

 some combination which secretes it 

 and deprives the plant of its services. 



The usual sources of supply for fer- 

 tilizing purposes are from animal sub- 

 stances, stable manure and from na- 

 tural deposits of nitrates. 



Potash is a more stable element, 

 though likely to be lost by leaching, 

 and is obtained in commercial quanti- 

 ties from wood ashes and from the 

 nitrates and sulphates. 



Phosphoric acid is commonly bought 

 in the shape of ground phosphatic 

 rock, from bone, horn, hair, from fish 

 and from basic slag. These three ele- 

 ments have been called "The tripod of 

 fertility." 



A so-called complete fertilizer as 

 prepared by the manufacturers will 

 contain, we will say, 60 lbs. of avail- 

 able nitrogen worth at 19c. per lb., 

 $11.40; 6 per cent, or 120 lbs. of avail- 

 able phosphoric acid worth at 5c. per 

 lb., $6.00; 5 per cent or 100 lbs. of 

 available potash worth at 5c. per lb., 

 $5.00; making a total cost of $22.00 per 

 ton, of which more than one-half is 

 represented by the nitrogen. 



From whatever source these ele- 

 ments are obtained, they must be solu- 

 ble in water in order to be available 

 to the crop. Potash and phosphoric 

 acid can be applied to the soil at any 

 time, and the loss from leaching or 

 otherwise is not very serious, while 

 any surplus beyond the present needs 

 of the plants will be retained for future 

 use; but nitrogen applied in excess is, 

 as a rule, nitrogen wasted, and as we 

 have seen, this is an expensive fertili- 

 zer. This leads us to the theory, which 

 has the support of good practice, that 

 nitrogen should be applied in small 

 quantities, and often rather than 

 enough at one time to perfect the crop. 

 There are combinations of nitrogen, 

 however, as in stable manure and 

 animal matters, which require time to 

 unlock and render available. Such 

 compounds may be applied in larger 

 quantities some time previous to the 

 planting of the crop, or a time allow- 

 ance made to enable the proper forces 

 to tear the combinations apart, and 

 render nitrogen fit for assimilation. 

 The high price of nitrogenous fer- 



tilizers has caused careful search to 

 be made for the purpose of finding 

 cheaper sources of supply than those 

 above mentioned. 



To understand the reasons for some 

 of the studies which have been made 

 with this end in view, it will be well 

 to review some of the theories of the 

 inhalation of nitrogen and the forces 

 which are supposed to play an impor- 

 tant part in the reduction of nitroge- 

 nous compounds and the secretion of 

 the product within the plant tissues. 

 Some of the most interesting chapters 

 in the history of plant life are those 

 dealing with the relationships between 

 widely different organizations where 

 a partnership is formed for the mutual 

 benefit of the parties concerned. It 

 was formerly supposed that all plants 

 growing upon others were parasites, 

 or, to use the somewhat "yellow" lan- 

 guage of Grant Allen, they were com- 

 mitting "Robbery and Murder." When, 

 nearly forty years ago, Frank made 

 the startling assertion that the "Beech 

 is a parasite on a fungus," he did not 

 mean just what we would ordinarily 

 understand by parasite, but that the 

 beech was simply dependent, for the 

 supply of nitrogen upon a mycorrhiza 

 or root fungus. 



Modern investigations have shown 

 chat many of the associations are far 

 from being criminal, and that the two 

 members are mutually dependent on 

 one another for existence. To this pe- 

 culiar arrangement has been given the 

 name of symbiosis, which, being inter- 

 preted, means growing together. 



Plants of the higher orders are de- 

 pendant for their supply of nitrogen 

 on that which is soluble in water, 

 while some of the lower forms are able 

 to extract it from its compounds, or, 

 as some claim, from the atmosphere, a 

 statement, however, which needs proof. 

 Of the lowly forms which possess 

 these powers of nitrification, perhaps 

 the most familiar are the maligned 

 bacteria. To these simple nitro-or- 

 ganisms we probably owe most of the 

 reduction of organic remains, the 

 breaking down of complex, and the 

 formation of simpler soluble ones. 



It is maintained thai a symbiotic re- 

 lationship exists between our red clover 

 and the nitrifying bacteria, and that 

 the little swellings or tubercles which 

 are ordinarily to be found on the roots 

 of the clover are the homes of the bac- 

 teria: that the bacteria supply the ni- 

 trogen necessarj for the growth of the 

 clover, and. in return, take from the 

 clover such elaborated food as they 

 may require. 



Such tubercles may be found on the 

 roots of beans, peas or, in fact, on 

 most any of the leguminous plants. 

 Whether the bacteria can take nitro- 



gen from the air may well be doubted, 

 but i( is a pretty well established fact 

 that they can extract nitrogen from 

 combinations that are beyond the 

 power of higher plants. So firmly has 

 the belief in this association been es- 

 tablisl ed that it, has become the prac- 

 tice to inoculate the soil with the 

 proper bacteria when legumes are to 

 be grown on soil where their natural 

 symbionts are lacking. 



This inoculation is often made by 

 the transfer of some soil from a fer- 

 tile field to the new location. One can 

 obtain on the market pure cultures of 

 bacteria suitable for various crops, and 

 sow with the seed. That the use of 

 these cultures is not uniformly success- 

 ful, does not disprove the theory, but 

 rather indicates that the preparations 

 are at fault, or that they are not prop- 

 erly applied. 



Long before these relationships 

 were known, the fact was realized that 

 if a good crop of clover could be grown 

 upon a field it could safely be relied 

 upon to grow a good crop of corn or 

 wheat the succeeding year, and this not- 

 withstanding the fact that the clover 

 had been cut and removed in the form 

 of hay, the extensive root system of 

 the clover with its stored nitrogen 

 being sufficient for the succeeding 

 crop. 



The action of fungi of the unicellu- 

 lar type in breaking down organic 

 compounds has long been recognized, 

 and put to use in many industries: 

 witness the yeasts and other ferments 

 of this class, but l heir mutual rela- 

 tionships with the higher plants are 

 subjects of quite recent inquiries. To 

 recur to the statement in regard to 

 the fungus and the beech, we find that 

 in this case we have a fungus of a 

 bighei and much more complex organ- 

 ization, a fungus which, instead of 

 being a microscopic unicellular plant 

 or a collection of similar cells, is really 

 a structure having organs highly dif- 

 ferentiated and making in some 

 stages cf its growth a conspicuous ob- 

 ject to the naked eye. Here, too, it is 

 believed that a symbiotic relationship 

 is maintained, and that the mycorrhiza, 

 in return for the nitrogen secreted for 

 the higher plant, takes its pay in 

 starch or sugar which it is unable to 

 make for itself. Investigation shows 

 many cases of symbiosis between 

 plants containing chlorophyl and those 

 which are without it. Among our 

 cultivated plants which depend more 

 or less upon the help of the root fun- 

 gus, we may mention some of the or- 

 chids, gerardias, polygalas, some erica- 

 ceous species and many others. If you 

 will examine some of these plants, or, 

 to be more exact, if you will place a 

 thin -ection of their root on the stage 



