u 



but it can be done with a tractor. The Hyatt Roller Bearinj^s Co. 

 kindly lent us a reliable high-class dynamometer with which were 

 taken measurements for cross ploughing land previously ploug^hed 

 in autumn. These show that the effect of chalking is to increase 

 the speed of ploughing and to reduce the draw bar pull on the three- 

 furrow plough by no less than 2001bs. 



We propose to extend these measurements to plots treated 

 witli other fertilisers : farmyard manure, green manure, folded 

 land, etc. The " secondary effects " of artificials, studied here by 

 vSir A. D. Hall, may prove to have a measurable economic value 

 when one adds up all the tractor cultivations of the year. This will 

 form an importaiit part of the programme of the soil physics 

 laboratory. 



THE POSSIBILITY OF INCREASED OUTPUT FROM THE 



LAND. 



It is often urged as a reproach to agricultural experts that in 

 spite of the multitudinous experiments of the last 20 years the 

 output from the land is no more than it was 50 years ago. The 

 statement is not entirely correct, but there certainly has been no 

 increase in output from the land comparable with that in industry. 

 One important reason is that much less cultivation is done now 

 than was usual 50 years ago, and in consequence the crop is not 

 given a full chance of making good growth. With the advent of 

 the tractor it will, we hope, become possible to remedy this defect 

 and to enabU,' some of tlie newer aids to crop production lo attain 

 their full effect. 



The results described in previous reports show that the output 

 from the land is much increased by the proper use of artificial 

 fertilisers on carefully selected suitable varieties of crops. In the 

 case of cereals good results have been obtained by the use of spring- 

 dressings of nitrogenous manures, these being required to replace 

 the nitrates washed out during the winter (see p. 35). Experi- 

 ments, however, show remarkable differences in effectiveness 

 according to the time of application. It is impossible on present 

 data to formulate hard and fast rules, but as shown below it 

 appears that a small dressing (1 c\vt. sulphate of ammonia or less) 

 may go on fairly late, while a larger dressing should go on earlv. 



THE AMOUNT OF FERTILISER TO l^SE. 



F'or many years the Rothamsted data have shown that the 

 yield of crops increases with the amount of manure supplied, but 

 beyond a certain point the increase is no longer proportional to the 

 added manure. In the old experiments the unit dressing was 



