126 



than a half of one per cent. Incidentally, the moisture 

 content is noticeably less under the covercrop, and this re- 

 duction has evidently practically offset the plantfood addi- 

 tions that should have come from the annual leguminous 

 covers. The further addition of an intercrop here has thus 

 far actually improved the trees by a trifle more than 4 per 

 cent, although the moisture content of this plat was lowest 

 of all at the time taken. This result is probably due partly 

 to the presence of a fertilizer in connection with the inter- 

 crop and also to the later seeding of the covercrop on this 

 plat. The addition of a complete fertilizer in plat 6 is now 

 showing a somewhat larger benefit than might be expected, 

 but this has just begun to appear in the last couple of years, 

 and its moisture situation is slightly favorable, — a fact 

 which shows up in the last two columns. 



The striking correlation between moisture supply and 

 the growth of young trees is evident here in the first two 

 and last two columns. The only important exception ap- 

 pears in the manure effects in plat 5 and this has already 

 been at least partly explained. In general therefore, on the 

 average soil and with average moisture conditions the best 

 growth of young trees will naturally b§ secured by the 

 method that is most efficient in conserving moisture. 



In this connection we may state that the samples for 

 the present moisture determinations were taken on Septem- 

 ber 6, after a six-week period of unusual drought, which 

 enabled us to test quite fully the moisture-conserving quali- 

 ties of the various cultural methods. Only 1.27 inches of 

 rain had fallen in the 43 days immediately preceding the 

 test, or only about 22.6 per cent of the normal for the 

 period, which is about 5.6 inches. The moisture was de- 

 termined both in the first and second 6 inches of soil, at a 

 distance of about 41/0 feet from the trees, and the figures 

 given in the third column show the average moisture pres- 

 ent in the surface foot. The figures in the last column are 

 calculated from those in the third, on the basis that a moist- 

 ure content of 20 per cent is about the optimum or best 

 possible content for the soil involved. 



In both the third and fourth columns, the remarkable 

 efficiency of the definite mulches in conserving moisture is 

 evident. Next to them, but decidedly lower, comes the plat 



