PRESIDENTIAL ADDRESS. 533 



layor of luck has a, tendency to refoiin wlikh can only be prevented by occa- 

 sionally ploughing- to greater depths than usual. 



Once the light soil is made deeper it can be still further improved. The 

 most permanent improvement is to add clay, or preferably marl ; this used to be 

 (k)ne in many parts of England, but it now only survives on certain fen or 

 peaty soils. "Here the soil is not sand but almost pure organic matter; it is, 

 however, very light. The operation in the fens is simple : the marl (mainly 

 c1av. and containing only a few per cents, of calcium carbonate) ' liee about four 

 or "five feet below the surface, and is reached by digging a series of holes arro.=s 

 the field; it is then thrown up to surface and spread. Another set of holes is 

 then dug about 18 yards away, and the process is repeated until the whole 

 Held is covered. The operation'is done about every twenty years ; it is admittedly 

 very successful, though I have been unable to obtain precise figures to show the 

 value of the improvement ; it would be more extensively carried out but for the 

 circumstance that much of the marl lies below the water-table, and cannot be 

 reached by ordinary means. 



More usually the marl does not occur under the sand but at some distance 

 away, so that it has to be carried, and this has killed the process in England. 

 Transit difficulties, however, need not be permanent, and they have a way of 

 disappearing in large-scale operations; this was successfully achieved in the 

 intensively "cultivated tract of land known as the Pays de Waes in Belgium. 

 The soil is very light : in places it is even blown about by tlie wind. But clay 

 lies near; it was brought in tramways,, and laid on to a depth of about four 

 inches. The soil then became very productive. Excellent results have also 

 been obtained in Denmark, where perhaps more than anywhere else the work 

 has been put on a .=;nund scientific and economic basis. Usually a district is 

 marled by co-operation between farmers whereby the cost of marl on the land 

 is reduced to about 2 kroner (2.^-. 3f/.) per cubic metre. This has necessitated 

 the construction of light railways from the marl pit to the farm, and the work 

 has been carried out by co-operative associations, often working on a loan from 

 the State, free of interest and repayable in twenty-five years. Another method 

 has been for the Society to buy moveable tracks and tip trucks and to let them 

 out to the farmer. 



The more usual method of increasing the absorptive power of light sandy soils 

 is to add organic matter, either by dressings of farmyard manure, by feeding 

 crops to sheep on the land, or by a method that wants much further investi- 

 "ation, ploughing crops or crop residues straight into the soil. But the organic 

 matter disappears at a very rapid rate, so that the process needs repeating 

 in one form or another every second or third year. In few cases only can this 

 be dispensed with : where the soil is deep and lies in a valley or even in a 

 saucer-shaped depression there may be enough seepage from the higher land to 

 ensure regularity in water-supply. More usually the addition of organic matter 

 becomes necessary : in the Norfolk Chamber of Agriculture field experiment.s 

 on light soils no mixture of artificials proved as effective as farmyard manure. 



The addition of organic matter must generally be accompanied by the addi- 

 tion of lime or limestone, otherwise the soil may become ' sour ' — a remarkable 

 condition, detrimental to plant-growing, but not yet fully understood by 

 chemists, and therefore more easily detected by the vegetation than by analysis. 

 Few light-land farmers use lime or chalk as regularly as they should for the 

 best results. There are two reasons for this. The first is that all crops do not 

 benefit by lime. The potato-crop in particular, which, as we shall eee later, is 

 one of the most valuable crops on light lands, responds neither to lime nor chalk 

 in an ordinary way; indeed, lime is considered to be actually harmful by favour- 

 ing scab. But although the potato- and even the oat-crop may not benefit by 

 limin£r. the clover certainly does, and this reacts on the corn-crops that follow. 

 Experiments are much needed to determine at what point in the rotation lime 

 or limestone should be added. 



Tlie second reason against liming or chalking is the old one of transit. 

 The problem is solving itself wherever finely ground lime.stone is to be had. 

 but over considerable tracts of countiy natural deposits of chalk, especially 



' A sample analysed in our laboratory contained 1.8 per cent, calcium, 24 per 

 cent, clay, and 31 per cent, fine silt (British units). 



