in determining whether or not a tile system should be installed 

 under given conditions. In the truck-growing sections of Nor- 

 folk, Virginia, I have seen complete systems of tile installed 

 in sandy soil which one would expect to afford a very quick 

 run off of rain water; but rains in that section are very heavy, 

 and the crops grown are worth a lot of money per acre, so that 

 the prudent farmer finds it a good investment to protect his 

 crop by an expensive system of tile. 



Quite the reverse is the problem of guarding against a dry 

 season. Here, again, in the case of expensive crops, such as you 

 market gardeners are growing, an irrigation system will un- 

 doubtedly pay. I have not come to that yet, but have de- 

 pended upon careful conservation of moisture by cultivation to 

 ehminate risks in this particular. Investigations made by King 

 show that a clay loam soil which was not cultivated to make 

 a dust mulch evaporated in one hundred days 2,414 tons of 

 water, equalling a rainfall of 21.31 inches; while the same type 

 of soil stirred to the depth of 2 inches to maintain a mulch 

 evaporated but 979.7 tons, equalling a rainfall of 8.65 inches. 

 The maintenance of a mulch, therefore, saved moisture equiva- 

 lent to 12.66 inches of rainfall. Since a crop transpires 300 

 pounds of water for each pound of dry matter produced, the 

 saving effected by the maintenance of a mulch might easily be 

 the determining factor in a dry year in producing a crop, the 

 moisture saved in the case of this type of soil being sufficient 

 to produce 4f tons of dry matter. I have been most careful to 

 guard against dry seasons by beginning harrowing of all plowed 

 fields as soon as they were dry enough in the spring, harrowing 

 again after each heavy rain until the crop was planted, and con- 

 tinuing to maintain a mulch by cultivating thereafter. This 

 method will solve the weed problem, and will pay in insurance 

 against drought big returns on the cost. The effects of a dry 

 season may also be guarded against by increasing the humus 

 content of the soil by plowing in green crops or manuring with 

 stable manure. This is well illustrated by the results of long- 

 range experiments conducted at Rothamsted, England. Grain 

 was grown for years upon plots fertilized in different ways. 

 In the cold wet season of 1879 the plot which had been fer- 

 tilized continuously with a complete artificial fertilizer yielded 



