AGRICULTURAL PROGRESS AND EXPERIMENTS. 573 
not for a moment think that we shall ever be able to dis- 
pense altogether with manures, but I do think that the 
potential plant-foods which are already in the soil can be 
made to contribute far more largely, and that they should 
be made to contribute as much as possible, to the nourish- 
ment of our crops; and that eventually, under ordinary 
conditions and for ordinary, as distinguished from intensive, 
farming, it will only be found to be necessary to hand-feed 
crops with such plant-foods as the soil is naturally, or may 
become by cropping, insufficiently provided with, or as par- 
ticular crops require in special abundance. 
I have pointed out that the turning of potential plant- 
foods into available and assimilable forms is accomplished 
by the chemical, physical, and biological activities which 
are incessantly going on in the soil, and have expressed an 
opinion that available plant-foods can be produced in 
increased quantities by increasing and stimulating these 
activities. J will now go on to show that by takimg proper 
measures we have a reasonable expectation of being able to 
do this. 
The factors which are the most important for the creation 
of a state of chemical activity or unrest in a-soil, and we 
are able to influence, are— 
(1.) Its physical condition.—The soil should be in good 
tilth; that is to say, its condition should be 
made to be such that it is sufficiently open for 
air and water to enter freely, and close enough 
to be able to retain and, in the drought-liable 
interior of Australia especially, hold until crops 
have made use of it, as much as possible of the 
rain-water which falls upon it, as well as be 
favourable for the movement of moisture in it 
by capillary attraction. The putting of land 
into a condition of good tilth is a matter of 
good and thorough cultivation, and of manage- 
ment suitable to its character. To enable it to 
take in and store as much water as possible (a 
matter of very great importance in the interior 
of Australia), the cultivation should be as deep 
as possible, and sub-soiling had recourse to for 
this purpose. This is a point to which I shall 
recur. 
(2.) The presence in it of orgame matters from dead 
plants.—This is the main disturbing agency 
which causes the chemical activity in soils, to 
which they owe so much of their fertility. 
