SECTIONAL TRANSACTIONS.— M. 519 



additional areas of marginal land go into this condition. In order to check 

 the shrinkage of our agricultural land it is desirable that we should examine 

 the possibilities of re-conditioning the marginal farms and of reclaiming land 

 which has gone out of cultivation. 



In many cases the deterioration is chiefly due to lack of lime and of 

 manures, particularly phosphates, but re-conditioning would involve 

 cultivation and usually some draining and renovation of buildings and 

 fencing. 



Special equipment and workers with some experience are necessary if 

 this work is to be done in the most economical manner. But even if the 

 equipment could be hired many of the owners of this class of land are 

 unable or unwilling to invest the necessary capital in re-conditioning it. 

 In some ways the problem of our marginal land resembles that of afforesta- 

 tion, but if the State were to purchase the land and undertake the re-con- 

 ditioning the farms could then be rented, with suitable safeguards, to 

 private individuals. Unless something of this kind is done, or unless special 

 facilities and inducements are offered to private owners, it seems likely that 

 still more of our agricultural land will revert to its original condition. 



Experiments on the re-conditioning of land have been carried out in 

 recent years at various centres and experiments on the reclamation of moor- 

 land are in progress in Lewis and in Lanarkshire. 



Dr. E. M. Crowther. — The maintenance of soil fertility (11.30). 



The old view that the maintenance of fertility in arable land requires 

 merely the return of the plant foods removed in the crops is now known to 

 be totally inadequate. Among other things it neglects the losses of calcium 

 and nitrate in drainage, and of nitrogen as gas, the conversion of added 

 phosphates and potassium into unavailable forms, and the steady loss of soil 

 organic matter. It fails to direct attention to the deterioration of physical 

 properties under continued cultivation through the destruction of root 

 channels and soil crumbs. Under extreme conditions of torrential rain or 

 prolonged drought, this may lead to soil erosion on a devastating scale. 

 The most effective measure of soil conservation is an active cover of vegeta- 

 tion, the living and decaying roots of which granulate the soil and make it 

 permeable to air and water. Most stable systems of arable cultivation have 

 involved either an alternation with grass, scrub, or forest or the production 

 of large quantities of bulky rotted manure. 



The possible chemical, physical and biological effects of farmyard manure 

 are so manifold that their precise analysis has rarely been attempted. The 

 traditional methods often prove unduly expensive under modern conditions 

 and attempts to dispense with them provide severe tests of technical skill. 

 On the other hand uncritical advocacy of old ways may merely retard pro- 

 gress. It is known that lime, the major plant foods, and some of the minor 

 plant foods can be supplied far more economically in inorganic forms, 

 where the principal soil deficiencies are known. Modern methods of soil 

 survey, field experiment and soil analysis can do much to reveal the require- 

 ments and potentialities of individual soils, but far more active co-operation 

 between official bodies, farmers and technical workers is needed to develop 

 these methods and extend their use. There is an especial need for field 

 trials over a term of years on the residual effects on soil fertility of different 

 systems of land management. 



General Discussion opened by Sir Daniel Hall, K.C.B., F.R.S. (12.0). 



