ae a 
1 Serr, 1897.] QUEENSLAND AGRICULTURAL JOURNAL. 209 
But how does nitrogen get fixed into the soil, or, in other words, what, 
produces that nitrification of the soil? The question has for thousands of 
years been a puzzle to the cleverest and shrewdest scientists of the whole 
world. True, according to Theophrastus, Pliny, and Columella, the ancients 
had empirically found out that they could enrich their soils by ploughing in 
green crops, and such a practice was extensively followed in ancient Greece 
and in many parts of the Roman Empire. At the beginning of this (nineteenth) 
century, chemical science had made sufficient progress to enable de Saussure, 
Boussingault, and others to explain that the beneficent effect of such ploughed- 
in crops was due to the singular property possessed by a numerous family of 
plants (the Leguminose) to provide, not only enough nitrogen for their own, 
requirements, but also to leave a good supply of it in the soil in which they 
were grown. But how that was being done, remained still a mystery. 
In recent years, however, the discoveries of Pasteur and Koch have 
completely transformed many of the natural sciences, by establishing beyond 
doubt that most of the changes which take place in Nature are the work of tiny 
organisms generally known under the names of microbes and bacteria. Being 
now put on the right track, two most conscientious and sagacious scientists 
(Willfarth and Hellriegel) directed their investigations on the various members 
of those nitrogen-producing leguminous plants. On most of their roots they 
found nodosities—or knots—and in those very nodosities, the tiny bacteria 
which first absorb the nitrogen and then fix it in the roots and soil. 
Modern scientists take good care to leave us no room for doubting their 
assertions. or instance, if the bacteria of a leguminous plant are killed—or 
sterilised, as the operation is called—that plant will grow like any other 
ordinary plant, without producing any nitrogen whatever, and taking from the 
soil that which it is in want of to form its tissues (protoplasm) and cells. Still 
more wonderful: Those tiny nitrogen-producing organisms are being isolated 
and cultivated —that is, multiplied like farm animals. They are then put in 
hermetically sealed bottles and sold—under the name of “nitragin”—to farmers, 
who sow them on their land. And at once those bacteria start their wonderful 
work of absorbing nitrogen and transmitting it to the soil, 
But those ultra-scientific means of enriching our lands with nitrogen are 
not yet within our reach. : 
Fallowing, during which it is probable that as yet unknown bacteria enrich 
the soil with nitrogen, is not to be recommended in this country, especially in 
summer. It is not improbable that the great heat kills those useful beings or 
paralyses their action. In any case it is in some way injurious to them. If 
any nitrogen is being formed during fallowing, it is often washed by heavy 
rains out of the reach of plant roots. And, finally, fallowing gives full play to 
noxious weeds which take hold of the field to the great detriment of the 
following crops. 
Commercial nitrogenous manures are not seldom either too expensive or 
require too great an expenditure of labour to be profitable. So that the simplest 
and cheapest way to give our fields the nitrogen they absolutely require, 
especially for cereals and other exhausting crops, is to grow on the fields 
leguminous plants, and plough them under whilst they are still in a green state. 
During his long residence in Western Queensland, the writer has been experi- 
menting for years with plants of that family, with a view to finding one 
answering all the requirements of a fertilising crop. None gave him entire 
satisfaction. Some, as lucerne, for instance, occupy the land far too long to 
form part of a regular rotation; others are of slow growth, or cannot stand the 
drought or a wet season. He was beginning to doubt of ever succeeding, when 
a few years ago the solution came to him from quite an unexpected quarter, 
when he received from the Department of Agriculture a few seeds of the 
so-called “cow-pea,” which Professor Shelton had recently introduced from 
America into Queensland. If the cow-pea is given in our national economy 
the place it deserves, it is bound to entirely revolutionise our agriculture. The 
time will come when it will be recognised as the most important economic plant 
