YoL. VIII. No. 199. 



THE AGRICULTURAL NEWS. 



391 



Tarieties, measures to be taken agaiust pests, the importance 

 of the continuation of the aid given by the British Cotton 

 Growing Association, and the manner in which cotton should 

 be shipped, the meeting closed, with a hearty vote of thanks 

 to Dr. Watts for his most valuable and interesting address. 



OBSERVATIONS ON WILD LEGUM- 

 INOUS PLANTS. 



Some interesting facts are brought forward, in 

 ■Circular No. 31 of the Bureau of Plant Industry of the 

 United States Department of Agriculture, with regard 

 to the way in which virgin soils have gained their 

 high nitrogen content. The following is abstracted 

 from the circular to which reference is made : — 



Many hypotheses have been formed to account for the 

 large stores of nitrogen in virgin soils, but none of these 

 have been entirely satisfactory. It seems to be a well estab- 

 lished fact that small ijuantities of ammonia are collected 

 from the air by rain and added to the soil; also, that more 

 or less nitric acid is formed by electrical discharges and 

 added to the sujiply. Some investigator.s have attributed 

 the fixation of nitrogen entirely to the latter cause. Recently 

 a number of efibrt.s have been made to show that non.sym- 

 biotic, or independent, bacteria are the chief agents in fixing 

 this element. While it seems certain that some nitrogen is 

 added to the soil by each of these methods, it appears to 

 the writer that there is not sufficient evidence to warrant 

 a conclusion that any one of them has been the most 

 important factor in this work. They do not furnish a satis- 

 factory explanation of the presence of such large quantities 

 of nitrogen in the soil. 



Several experimenters have suggested that wild legumes 

 may have played some part in this work; they have not 

 generally been considered as important factors. The studies 

 reported in this circular indicate that this subject deserves 

 more thorough investigation than it has yet received, and 

 that native legumes have been of much more importance in 

 this role than has been thought. 



Several years ago, the writer raised the question as to 

 ■whether the native legumes of the prairies were sutfioiently 

 numerous to have fixed the anmunt of nitrogen present. 

 A search for published data on the subject was made, but 

 none were found. Accordingly, in the spring of 1908 a series 

 of investigations was begun, a preliminary report of which is 

 here given. 



The writer had long been familiar with the flora of this 

 region but was not at all prepared for such results as were 

 found. The average numbers of wild leguminous plants 

 per sijuare yard, that were found, were: ordinary ground 17, 

 high plains 3-6, and .sandhills ,S-4. After the grasses 

 (including sedges) and possibly the c.-^mposites, legumes form 

 a larger part of our flora than does any other group of plants. 

 If these figures are representative, or anywhere near it, it is 

 evident that our farm lands from time immemorial have been 

 growing a full stand of legumes. Seventeen plants to the 

 square yard are enough to fill all the soil with their roots. 

 Most of these plants, .such as Amorpha, Kuhnistera and 

 Psoralea, have enormous root systems (and these genera 

 represent the large majority of the prairie legumes). 

 A single plant is often sufficient to fill the soil with its roots 

 for a radius of several feet, as any farmer who has ploughed 

 up Amorpha is ready to testify. The .smallest root system.s 

 are probably those of Vicia and Lotus, and yet seventeen of 

 these to the square yard would seem to be sufficient to 

 gather a large supply of nitrogen. 



Many examinations were made to ascertain the preva^ 

 lence of nodules upon different species. Large numbers of 

 tubercles were found on every species examined, and on 

 nearly every individual except mature Kuhnistera. Nodide.s 

 are especially plentiful on Psoralea, Astragalus, Acuan, 

 Meibomia, and Lotus. On Lotus the nodules are often 

 almost massed together on the tap-root. Some difliculty was 

 experienced at first in finding tubercles on Kuhnistera, but 

 they are always in evidence on seedlings. On the old plants 

 there is a doubt whether typical nodules are produced, or 

 whether the bacteria are in the small, thickened roots which 

 occur in extraordinary numbers, almost in fascicles, especially 

 on roots of the previous year's growth. During the coming 

 season an eflbrt will be made to determine this point. The 

 efiiciency of these legumes as nitrogen gatherers does not 

 seem open to question, however, if the univers:d inoculation 

 of the seedling plants is considered. 



It does not seem that most of these legumes choose the 

 poorer soils, for, in fact, many of them grow much better on 

 rich soil; but when the soil becomes rich in nitrogen and 

 humus, other plants which do not thrive on poor soil are able 

 to crowd out the legumes. There is good reason to believe 

 that lands that are now richest formerly supported the 

 densest leguminoits growths, except, perhaps, where the 

 plant food has been washed down from higher levels. 



AVestern farmers have been slow to learn their lessons 

 from Nature. Nature on her farm has kept up the produc- 

 tion of grasses and other nitrogen robbers by the constant 

 growth of legumes. If this fact had been recognized sooner, 

 perhaps there would not have been such reckless exploitation 

 of the rich .soils of the Mississippi basin. For forty years 

 farmers have lost sight of this and have taken oft" grain crops 

 (all grasses) continuously, and doubted if this prac'Jee would 

 ever exhaust their soils, because they were still productive 

 after the removal of twenty, thirty, or forty crops. But now 

 the eft'ect is evident; farmers must learn from the prairies 

 round them one of the first principles of permanent agricul- 

 ture, and introduce leguminous crops into the farm rotation. 



THE SOY BEAN. 



An account of the so}^ bean was recently given in 

 the Agricultural A'ews (Vol. VIII, p. 222). An 

 interesting addition to the information containecl there 

 is to be found in the October number of the Journal 

 of the Jamaica. Agricultural Society. 



An enormous quantity of soy bean cake is now being 

 imported into Great Britain from Manchuria. This cake 

 has already won a high reputation as a food for milch cows. 

 The soy bean cake is sold at about £6,15.s. to £7 a ton. 

 Some recent trials have been carried through in the United 

 Kingdom with soy bean cake as against cotton seed cake; 

 the results were fairly equal, with a slight advantage in 

 favour of soy bean cake. 



The following analysis has been made: — 



Decorticated Soy cake. Soy l.ieans, 



cotton cake, per cent. per cent, 



per cent. 

 Moisture 10-89 1331 10-23 



Oil 13-18 600 15-62 



Albuminoids 40-18 44-37 37-.54 



Carbohydrates 24-22 2504 27-27 



Woody fibre 4-13 3-90' 5-02 



Ash 7-40 7-38 4-32 



Nitrogen 

 Sand 



6-39 

 None 



7-10 

 1-20 



601 



None 



