1921.] : RoTIIAMSTED EXPERIMENTAL STATION. 77V 



Time of Sowing. — A further advantage of the tractor is that 

 it enables cultivation to be pushed forward so rapidly in 

 autumn as to allow winter corn crops to be sown early. Tn 

 is no advantage in sowing too soon, but experiments have 

 shown that on the Rothamsted land winter oats should go in 

 during the first fortnight in October, and winter wheat during 

 the second fortnight. With horse cultivation it was impossible 

 to be right up to time, and the result was a certain proportion 

 of poor corn crops which became badly infested with weeds. 



Chalking. — It is also found that the work of the tractor on 

 heavy land can be considerably lightened by the use of chalk.* 

 One of the fields is divided into three parts, two of which are 

 chalked and the third unchalked. A dynamometer was 

 attached to the tractor as it was hauling the plough across 

 these strips. On the unchalked land the draw-bar pull was 

 1,610 lb. for three furrows, and the speed per hour was 1.98 

 miles; as soon as the plough entered the chalked strip the 

 draw-bar pull fell to 1,425 lb. and the speed of working 

 increased by 1 mile in 5 hours. This reduction in draw-bar 

 pull means a considerable reduction in fuel and in wear and 

 tear, while the additional speed is a valuable asset. 



Cultivation Implements for the Tractor. — The cultivation 

 implements in common use were designed for the horse, and 

 it by no means follows that they are equally suitable for the 

 tractor, which is a very different agent." The ordinary trials 

 are not entirely satisfactory from the farmers' point of view; 

 they are rather artificial. In practice cultivation is carried out 

 to facilitate crop production, and the final test of the efficiency 

 of a machine is the help that it gives to crop growth. At 

 Rothamsted an attempt is made to carry out the test to give 

 the farmer this information; the work of the implements is 

 carefully observed over the whole of the growing period of the 

 crops. The advantage of this plan is that farmers have an 

 opportunity of seeing the implements at work under practical 

 farming conditions, and of judging the value of the work from 

 the growth of the crop, w T hich is after all the best criterion. 

 Some of the largest and most important implement makers 

 are co-operating and lend their implements free of charge. 



Supplies of Organic Matter in the Soil. — Recent experi- 

 ments emphasise the importance of having ample supplies of 

 organic matter in the soil. Some of the older agricultural 

 chemists tended to the view that artificial fertilisers were tlie 

 chief source of fertility and that little more need be done if 



* This Journal, August, 1921, p. 419. 



