536 TRANSACTIONS OF SKCTION M. 



corn ; too wet in winter to bo ploughed for spring corn j and too dry in sprincr 

 to be prepared for mangolds. There are times in between -when something can 

 he done, but only the man who is skilful enough to take fuU advantage of these 

 intervals has much hope of success. Mo.';t men, therefore, prefer not to run the 

 risk of cultivation, and lay the land down to permanent grass. 



_ There are two directions in which the risk can be reduced, though it will 

 still remain a serious factor. 



The great difficulty of cultivation arises largely from the circumstance that 

 only on a relatively small number of days are both soil and weather suitable for 

 ploughing. The result is that much of the work is left till late, and late work 

 tends to be bad work. This can only be overcome by speeding up the process 

 of ploughing during the favourable opportunities, and so far as I can see this 

 is only possible by the use of motors. I believe, therefore, that motor-ploughs 

 and cultivating implements will play a considerable part in the improvement of 

 heavy land. 



A second direction in which the risk can be reduced is by keeping up the 

 supply of organic matter in the soil. The action of organic matter is partly 

 mechanical, partly more complex, but the result is that the soil becomes lighter, 

 works down more readily to a tilth, and shows less tendency to fluctuations in 

 crop. The Broadbalk plot at Rothamsted, receiving farmyard manure, gives a 

 steadier yield, showing far le.'^s fliictuation than the plots receiving dressings 

 of artificial manures. 



Probably the cheapest and most satisfactory way of increasing the supply of 

 organic matter in the soil is by ploughing in crop residues, such as, for example, 

 are left by a seeds mixture, a clover ley, or ploughed-up grass-land. Their 

 effect is well seen by comparing the wheat-yields on the Agdell field at Rotham- 

 sted, where clover is plouglied in prior to "the wheat, with those on Broadbalk. 

 where wheat only is grown, and where, therefore, nothing bigger than wheat 

 stubble and its accompanying weeds is ever ploughed in. " The Broadbalk plot 

 receives far more manure than the Agdell plot, and in good years it gives higher 

 yields, but in poor years it comes down much lower; the flnctuations are 

 considerably greater. 



Steadying Effect of Crop Eesidues on Yield of Wheat. 



Agdell Field. r, n i, 



-Vfter Clover plouglied ,„, Broadbalk 



jjj Alter previous Wheat. 



Complete Artificials Complete Artificials 



Average of all 



Highest yield, 18(5:5 



Low yields, 1871 



„ 1875 



„ 1879 



„ 1903 



Land that went down to grass in the '90s because cultivation was too risky 

 has now gained so much organic matter that it can safely be cultivated again. 

 Mr. Strutt has done this satisfactorily on some of the heavy Essex clays. The 

 Duke of Marlborough has ploughed up some of the grass in Blenheim Park, 

 though here, as a matter of fact, tlie land is not all clay but includes corn- 

 brash that never need have gone down to grass at all. At Rothamsted we have 

 recently ploughed up a poor grass field that for some years had barely paid its 

 rent, and the crops promise to be considerably more remunerative than anything 

 we have had before. The conditions for success seem to be that the soil shall 

 be turned right overin the ploughing, and then rolled down so as to prevent 

 the grass from growing up between the furrows; and, further, that measures 

 should at once be taken against weeds, either by growing hoed crops like 

 potatoes or beans drilled in rows sufiiciently far apart, or some dense crop 

 like winter oats that will smother everything else. Tn our ploughed-up field 

 wherever the trial crops are thin we had a brilliant display of charlock and 



