.Vol. VTII. No. 184. 



THE AGRICULTUKAL NEWS. 



151 



INOCULATION OF LEGUMINOUS CROPS 



IN THE WEST INDIES. 



During the year 1908, the effect of inoculating 

 the soil, or in some cases the seed, to be sown, with 

 prepared cultures of nitrogen-gathecing bacteria was 

 tried at Antigua and Grenada, with the object of 

 ascertaining whether such a procedure would stimulate 

 the growth, and increase the crop return.s of various 

 leguminous crops. At Antigua, where cowpeas, woolly 

 pyrol, and alfalfa were the crops nnder experiment 

 .at the instance of Messrs. Henckell,.pu Buisson & Co., 

 Professor W. B. Bottomley's' Nitro-bicterine ' was the 

 -inoculating material used, but at Grenada, a culture 

 preparation sent out from the United States Depart- 

 ment of Agriculture was employed. « It may be added 

 that e.xperiments in which a small number of sugar-cane 

 'plants were inoculated with a special culture prepared 

 by Professor Bottomley, in the hop^ that it might be 

 beneficial in increasing the yield, were also carried out 

 .at Antigua and Barbados. 



At Antigua inoculation experiments were conducted at 

 the E.xperiment Station, and also "at Fitches' Creek, 

 'Gambles, and Cas.sada Garden. 



Seed of the different crops sown was inoculated at the 

 Laboratory, and part of the culture .solution was used in 

 inoculating the soil, and later on the growing crop.s. Where 

 crop and .soil inoculation was carried on,' two applications of 

 the .solution were made, at an interval of a fortnight. 



No effect of inoculation could bo ti'aced in the case of 

 ihe cowpeas grown. Practically no differences were observ- 

 able between the treated and the untreated plots. It is 

 therefore to be presumed that the soils in the e.xperimeiit 

 plots weve well stocked with the bacteria responsible for 

 nodule formation on this crop, or that they were well supplied 

 ■with available nitrogen. 



With woolly pyrol the results of iiicKulation were, in the 

 case of one estate, more definite and satisfactory-. The 

 experiment plots were each |-acre in ared, and from the plot 

 sown with seed that had not been inoculated 330 lb. of green 

 bush was gathered. A second plot also sown with 

 urunoculated seed, but which was ' watered ' with the culture 

 fluid, yielded 700 lb. of green bush ; a third plot that had 

 been sown with inoculated seed gave 970 K). of bush, while 

 from the fourth plot, .sown with inoculated seed, 1,015 lb. of 

 bush was reaped. It will be seen that in the cases indicated, 

 inoculation seems to have been distinctly beneficial for woolly 

 pyrol. At two of the stations, however, ,all the plants on the 

 •experiment plots were destroyed by caterpillars. No report 

 has yet been received on the trials with alfalfa. 



The Grenada experiments were designed to ascertain ( 1 ) 

 whether any benefit is to be derived J'frora inoculation of 

 leguminous crops on Grenada soils, knd (2) whether, by 

 inoculation, leguminous green dressings,- such as cowpeas, can 

 be grown under the shade produced by full-grown cacao. 

 The trials were made at the Experiment Station, and on six 

 different estates in the island, where the crop under treatment 

 was cowpeas. whch were inoculated wiiti a material prepared 

 especially for this plant. ' ■ 



At the Botanic Station and two of the estates, the 

 results obtained showed no difference Whatever in favour of 

 inoculation. At two other estates, tihe returns from the 

 inoculated j)lots were slightly superior to those which had not 

 "been treated. Finally, on the two ' remaining estates — 

 Dougaldston and Diamond — it is reported that the inoculated 



plots gave yields very considerably higher than the untreated 

 plots, although no actual figure.s_are stated. 



Inoculation, however, had no eft'ect in influencing the 

 growth of cowpeas plantetl beneath the shade of cacao trees, 

 and these failed completely in aU cases. The results of the 

 experiments, therefore, give a ri^ative reply to the second 

 <juestion suggested above. 



It may be added that die inoculation of sugar-cane 

 plants with Professor Bottomley's culture preparation could 

 not be observed to have any effect whatever, f ither at Antigua 

 or Barbados. 



CULTIVATION AND FERTILITY. 



Thorough and judicious cultivation is es.sential for a soil 

 to give its best results as a crop-producing medium. Provid- 

 ing a soil is well-drained, the more deeply it is cultivated, 

 the more extensive is the arCii through which the plants can 

 forage in search of food, and thus it is that improvement in 

 tillage methods which result in deepening the .soil and 

 promoting nitrification, tend to have the same efi:ect as 

 applications of manure. 



The advantages of a deep soil, as compared with 

 a shallow soil, are obvious, and — expressed concisely — these 

 may be said to consist in the fact that when land is ploughed 

 to a depth of no more than 3 inches, the plants growing 

 thereon have 3 inches of food, while when the land is ploughed 

 6 inches deep the lantl has access to 6 inches of food, and so 

 on. The lower portions of the soil are not so rich in avail- 

 able plant food as the upper portions, but this may be 

 remedied to a large extent by .suitable cultivation, which 

 results in admitting air, moisture, and heat, the necessary 

 conditions under which fertility is developed. 



It need hardly be pointeif out, however, that any deliberate 

 attempt to lower the line of division between the soil and sub- 

 soil by deeper ploughing should be carried out gradually and 

 with caution, and the most judicious plan is to extend the opera- 

 tion over several years, i.e., to plough just a little deeper each 

 season than w^as done in the i)revious year. Many instances 

 are on record in which the fertility of land remarkable for 

 its crop-producing capacity has suffered enormously as the 

 result of lowering the dei)th ,of ploughing 2 or 3 inches 

 below the normal level in one ,sea.sun. This is because the 

 surface soil containing the organisms which are responsible 

 for the breaking down of plant food, has been buried, and 

 a heavy, raw, infertile subsoil brought to the top. 



Another important point in connexion with the capacity 

 of a soil to return large crops is its ability to retain moisture. 

 This power is greatest when thejand contains a good propor- 

 tion of humus, is well tilled, ttforoughly pulverised, the sub- 

 soil firm, and the soil kept in the form of a loose mulch at 

 the surface. ^ 



As the result of all these conditions, absorption of rain 

 water takes place readily, and this is retained instead of 

 rapidly draining away. Water in a cultivated soil is held in 

 the f<.irni of thin surface films enclosing each separate particle. 

 It is obvious, therefore, that the more thoroughly the land is 

 pulverised by cultivation, the greater will be the number of 

 soil particles, and the greater the capacity of the land 

 to retain moisture. The presence of humus increases this 

 storage capacity, and reduces evaporation. It has been 

 estimated by agricultural physicists that a ton of humus will 

 store over seven times as much moisture as a ton of sand, 

 and further, that sand loses its water by evaporation from 

 three to four times as rapidly as the humus. Clay .soils 

 store only about one-fourth as - much moisture as humus, and 

 lose it by evaporation about twice as rapidly. 



