Scientific Agriculture. 



462 



[May 1908. 



the highest percentage of nitrogen was 

 found in the nodules themselves. The 

 following table shows these figures in 

 detail :— 



Table II.— Occurrence of Nitrogen 



IN INOCULATED AND UNINOCULATED 

 PLANTS OP THE WILD HEMP. 



(Grams of nitrogen per 100 grams of 

 dry substance.) 



1. Roots, stripped of nodules ... 1"50 



2. Nodules (from No. 1) ... 6 40 



3. Tops (from No. 1) ... 209 



4. Whole plants (inoculated, hav- 



ing numerous nodules) ... 3 01 

 5- Whole plants (uot inoculated, 



no nodules) ... 1*71 



In veiw of the generally recognised 

 importance of nitrogen to the growth 

 of plants* the significance of the fore- 

 going facts needs little emphasis. A 

 difference between abundant nodule 

 formation and the absence of nodules, 

 which may affect the value of a legume 

 crop in the ratio shown, cannot fail to 

 command attention when its bearing 

 on successful farming is once realised. 

 It is not enough merely to count yields 

 in pounds or tons. The composition of 

 crops for feed or green manure becomes 

 in the light of these investigations a 

 factor of importance. 



Green Manuring and Inoculation. 



Generally speaking, the experience of 

 scientific farmers and the tests of agri- 

 cultural experiment stations agree iu 

 ascribing an unusual benefit to succeed- 

 ing crops from green manuring with 

 leguminous crops, and this is clearly 

 due in a considerable degree to the nitro- 

 gen fixed by the root nodules and not 

 to the length of the root system or 

 other peculiarities of leguminous plants. 

 Unfortunately, investigators have not 

 given sufficient attention to the relative 

 abundance or scarcity of nodules when 

 experimenting with different leguminous 

 crops for green manures. 



From the preceding data it is evident 

 that legumes reach their maximum 

 value as green manures only when 

 abundantly supplied with nodules. 



Confusion of Nem \tode Galls with 

 Nodules. 



Nematode galls, or root knots, are 

 often mistaken for nodules, which they 

 resemble in appearance. The nematode 

 gall is extremely injurious, and in regions 

 where it has been known to exist it is 



* See Bulletin 247 of the New York [Ithaca] 

 Agriultural Experiment Station, 



unwise to plant crops favourable to the 

 development of the pest. Nearly all of 

 the legumes should be avoided in such 

 cases. This is important not only because 

 the legumes susceptible to nematode 

 attack are themselves injured, but 

 chiefly because they furnish conditions 

 favoura ble to the rapid development and 

 multiplication of the nematode worms, 

 and these may become a serious menace 

 to succeeding crops or to orchard stock, 

 which under ordinary conditions they 

 would scarcely injure. There are, how- 

 ever, some resistant varieties* upon 

 which the nematode worm cannot deve- 

 lop, and in infested regions these resist- 

 ant varieties should be used exclusively. 

 If a leguminous crop with its roots 

 covered with what are apparently 

 nodules makes a sickly growth, or if 

 there is doubt as to whether a legume 

 is inoculated or infested with nematodes, 

 samples for examination should be for- 

 warded to the Bureau of Plant Industry 

 of the Department of Agriculture. 



When Inoculation is Desirable. 

 Inoculation is desirable — 



(1) If the soil has not previously 



borne leguminous crops. 



(2) If legumes previously grown on 

 the same land were devoid of nodules. 



(3) If the legume to be sown belongs 

 to a species not closely related to one 

 previously grown on the same soil, 



(4) If the soil produces a weak growth 

 of legumes, even though their roots show 

 some nodules. 



It is significant of the relative value of 

 pure culture inoculation that a high 

 percentage of beneficial results is being 

 obtained, not only where legumes new 

 to the region are being tried, but where 

 the ordinary legumes used in rotation 

 have been inoculated, a phenomenon 

 which is undoubtedly due to the in- 

 creased virility of the nodule-forming 

 bacteria resulting from the proper 

 development of the pure cultures in the 

 laboratory. It is also trne that the 

 crops following the inoculated legumes 

 have in many cases shown gains not 

 evident in the legume crop. The prac- 

 tice of inoculating is therefore justified 

 where legumes are naturally inoculated, 

 but do not seem to reach their full 

 vigour nor to give the best results as < 

 green manures. 



* The mo^t important and generally useful resist- 

 ant variety is the iron cowpea (Vigna sinensis). In 

 the Southern States the velvet bean (Mucuna 

 utilis) and Florida beggarweed (Meibomia molli*) 

 are valuable. 



