ON RECENT DEVELOPMENTS IN AGRICULTURAL SCIENCE. 269 
bacterial infection in South African soils is worthy of most careful 
investigation. It is necessary to know to what extent nodules are formed 
when lucerne is planted on new soils in South Africa, as, for example, on 
freshly broken-up veldt ; the condition of the organisms within the nodule 
should be investigated, so as to ascertain if improvement be possible by 
inoculation from pure cultures, either imported or prepared de novo from 
lucerne within the country. These and kindred questions connected with 
the symbiosis of the nitrogen-fixing organism and the leguminous plants 
must to a large extent be worked out afresh in each country, and South 
Africa, with its special conditions of soil and climate, cannot take on trust 
the results arrived at in Europe or America. 
T have spoken of the enrichment of the soil due to growing lucerne, 
caused by the decay of the great root residues containing nitrogen 
derived from the atmosphere; an enrichment which is quite inde- 
pendent of the amount of similarly combined nitrogen taken away in 
the successive crops of leafy growth. Some of the Rothamsted experi- 
ments show very clearly how great the gain may be. In the first place 
T will call your attention to the effect of a crop of red clover grown in 
rotation upon the crops which succeed it, since in the Agdell rotation- 
field we get a comparison between plots growing red clover once every 
four years and other plots on which a bare fallow is substituted for the 
clover. 
TABLE I, 
Wheat, 1895 | Roots, 1896 Barley, 1897 
Mannring for Swede Orop |Clover | haan jr | 
only 1894, | After] 4 so, |Imerease| After , ¢,,. Increase | After After Mueresse 
Fal- | due to || Fal- | due to || Fale 4t''®" | due to | 
low ee’ Clover || low lover! Cl Clover | 
ares | | 
| | | | | | | 
Cwt. | Ib. lb. Percent,|) Cwt. | Cwt. Per cent. Ib. lb. Percent. 
| Mineral Manure A - | 59°7 | 4,220] 5,180] 4+22°7 17971 | 2445) +36°5 || 2,103| 3,991, +898 
ee Manure . - | 767 | 4,547) 5,209] +14°6 } 3798 3888) +24 | 3,095 | 4,913) +367 | 
The table shows that in one particular case, when an extra large crop 
of clover was grown, notwithstanding the fact that the clover plots 
yielded between three and four tons per acre of clover hay, yet the wheat 
crop which followed this growth of clover was 15 per cent. better than 
the wheat crop following the bare fallow. The swede turnip crop, which 
followed the wheat, although similarly and heavily manured on both plots, 
continued to be better where the clover had been grown two years 
previously ; and even the barley, which came next, three years after the 
clover, showed a decided superiority on the clover land. Thus a clover 
crop, itself wholly removed from the land, exercised a marked influence 
for good on at least the three succeeding crops grown under the ordinary 
conditions of farming. Next we can make a comparison between red 
clover and lucerne. On some of the Rothamsted plots various leguminous 
plants have been grown for many years, with indifferent success indeed, 
because of the well-known reluctance of the land to support such crops 
except at intervals of four or more years. Eventually the plots on which 
these indifferent crops had been secured were ploughed up and sown with 
wheat without any manure. In five years the wheat was thus grown on 
the residues left in the soil by the previous leguminous crops, and from 
