80 The Supplement to tlie 



practical teaching of our modern experiments 

 for extracting nitrogen from the air. Varro, 

 before Virgil, even came nearer modern prac- 

 tice, for he advised the sowing of certain crops, 

 not with the immediate hope of harvest, but in 

 the knowledge that such crops ploughed in 

 would increase the fertility of the soil. That is 

 the practical experience of high farming of 

 today. Crops are sown to 



CATCH AND DETAIN CHEMICAL ELEMENTS NECES- 

 SARY FOR THE CROPS 



to succeed them, and then are ploughed in. But 

 the great thing is the mixing and breaking up 

 and ventilating the soil, ploughing it to enable 

 the frost to do its proper work, pulverising it so 

 that the water which is to hold the food for the 

 plants' roots can cling round every tiny particle 

 of soil. Then the roots can push free and far 

 and find food and drink wherever they push. 

 That is the substance of human knowledge of 

 the oldest of man's industries. The soil holds 

 all that a plant needs if it can be broken up 

 sufficiently small for the plant to get at its food. 



To inciease tilth and to decrease manure is 

 the main tendency of modern scientific farming. 



An interesting little book, summing up in a 

 condensed form the conclusions of many ex- 

 periments iu soils and farming generally, has 

 just been published by Mr Primrose McConntll, 

 a practical farmer of Southminster, Essex, un- 

 der the title "Soils: their Nature and Treat- 

 ment." How much is there still waiting for the 

 farmer to discover, of the soil which Varro 

 wrote two thousand years ago, and man had 

 been learning for uncounted centuries before 

 him ? If the need for good tiithBtill remains 

 the greatest need of all, what have we learnt 

 that the Roman farmer did not know ? Of 

 the actual practical work of ploughing and 

 sowing probably very little. Of the com- 

 position of soils and subsoils perhaps a 

 little more. We know, for instance, what 

 he had no opportunity of knowing,— that the 

 rule of cultivable soils is pretty nearly the 

 same the whole world over. First the top 

 layer, some three inches of turf ; under that 

 a layer, which may be shallow or deep, but is 

 seldom much more than afoot deep of soil; under 

 that a subsoil ; under that, a layer of "brash" or 

 rubble ; and, last of all, the bedrock itself, from 

 whose surface all the rest have been rubbed and 

 washed and broken by frost and rain and sun and 

 clinging plants. The Roman farmer could get a 

 practical knowledge of the actual earth which he 

 himself worked, but he could not of course, 



Tropkal Agricultiiriil 



compare the geology of five continents, What 

 has been reserved for a generation living two 

 thousand years after him to discover is that the 

 soil is something very different from what Eng- 

 lish farmers believed it to be forty or fifty years 

 ago. Perhaps the Roman, or the Greek before 

 him, knew it instinctively, for was it not an Eng- 

 lishman who first called the earth Mother P But 

 it was not until our day that science established 

 the fact that the soil is not a mass of dead, inert 

 matter, to be shovelled here and shifted there, 

 merely a fortuitous collection of powdered rocks 

 which can bo "manured/' or worked by the 

 hand into different places and various uses; but 

 is a teeming world of living creatures; an aggre- 

 gate of millions of tons of so-called "soil" which 

 can bring forth life because it is itsdlf alive ; 

 which holds in its open, 



ARABLE SURFACE SECRETS OF LIVING ORGANISM 

 AND GROWTH AND FERTILITY 



which men who have ploughed it since the begin- 

 ning of earning bread only yesterday began to sus- 

 pect, only today recognise faintly and perhapsonly 

 in the end of things, perhaps never, will fathom. 

 The more man learns of other life, the further 

 the horizon of his own life retreats from him. 



The principles of the plainer methods of im- 

 proving soils are simple enough. Wet soil can 

 be drained, and so made more capable of hold- 

 ing water. It sounds contradictory, but an ill- 

 drained soil does not hold water as plants like 

 it held,— that is, collected by capillary attrac- 

 tion to tiny particles, with room for air next to 

 the water. Rather it contains stagnant settle- 

 ments of water at which roots will not drink, 

 and which need to be drained away. Some 

 soils must be drained of water, others cleared 

 of stones. Others, again, need to be limed, or 

 supplied with a body which acts in various 

 ways, nearly invariably beneficially, on various 

 soils. Lime stiffens sand, makes clay friable, 

 and helps plants whose roots take up nitrogen 

 from the air in the soil iii retaining surpluses 

 of the gas which otherwise might be too much 

 for them. Plants which take up nitrogen some- 

 times succeed in choking themselves; and lime, 

 as it were, helps them with what they cannot 

 manage of their plateful. But the most interest- 

 ing, and, regarded from different points of 

 view, at once the darkest and best lighted of 

 the problems of soil and cultivation, is the 

 question of what perhaps may be called bac- 

 terial aid to plant-growth. Soil, separated into 

 its constituents, consists of some twelve or 

 thirteen chemical substances, existing in various 



