ON THE TEMPERATURE OF THE SOIL 71 



weather ensues the difference between the two plots becomes greatly 

 accentuated. On August 16th the plots were cut shortly after the 

 temperature readings were taken, and the hay lay on the swathe 

 until the 21st, when it was raked up, weighed and carted. The reason 

 for the difference in temperature which had existed throughout the 

 season soon became apparent. With the removal of the dense covering 

 from Plot 17 the temperature records corresponded very closely with 

 those of Plot 16, and in fact on several occasions were a trifle higher. 



The temperature records taken at a depth of 9 inches on each 

 plot serve to emphasise the importance of an adequate covering of 

 the soil. The beneficial effect of the covering action of the clover on 

 the slag plot is very marked even at a depth of 9 inches, and during 

 the warmest periods there is often a difference of 3 C. between the 

 two plots, Plot 17 being invariably the cooler, despite the fact that 

 the moisture content at this depth was generally lower than on Plot 16, 

 the untreated plot. With the removal of the crop on August 21st 

 this difference in the temperature records of the two plots at a depth 

 of 9 inches becomes negligible and the two curves follow each other 

 very closely indeed. 



It is of course difficult to say how far this 'secondary effect' of 

 the action of slag has contributed to the difference in the cropping 

 power of the two soils (28-8 cwts. on Plot 17 and 6-4 cwts. on Plot 16), 

 but there can be little doubt that it is of very considerable importance, 

 and that during a dry season it may well be the most important action. 



To retain moisture and keep the soil cool is the great difficulty 

 experienced on this type of soil during the late spring and early 

 summer. It is obvious therefore that whatever is possible should be 

 done to maintain a thick close bottom, and for this purpose it is very 

 desirable that the meadows should not be cut every year, but should 

 be cut one year and grazed the next or two following years. To reserve 

 a meadow for hay for several years is far from desirable under the 

 climatic conditions prevailing in the east of the county, unless a hay 

 crop varying from 1-7 cwts. of hay per acre should prove sufficiently 

 profitable. 



Martin's Hearne. It is of interest to compare the results at Horndon 

 with those at Martin's Hearne. At Martin's Hearne the plots were 

 cut for four years in succession and are known to have been cut for 

 hay during the two years prior to the commencement of the experi- 

 ments. There is no close bottom of clover at this centre such as that 

 at Horndon (compare Tables XV and XXIV). At Martin's Hearne 

 the clover dies down at the end of the season and in the following 



