ORCHARD SOIL MANAGEMENT METHODS 43 



or water. Furthermore, the protective action of the cover crop through 

 checking wind velocity close to the ground and through shading the soil, 

 thus lowering its temperature, may fully compensate for its use of water 

 during the late smnmer and early fall. The data presented in Tables 23 

 and 24 show that later in the season, cover crops may actually contribute 

 indii-ectly to the soil moisture content. The examinations recorded in 

 Table 23 were made at Ithaca, N. Y., in November 1901, at the close of an 

 extended drought. Those recorded in Table 24 were made at intervals 

 during the winter of 1905-1906 in Wisconsin. The report upon this 

 latter investigation states that the moisture determinations taken in the 

 spring on the soil under these cover crops confirms the results obtained 

 in the fall and winter "in that it shows the average moisture content of the 

 covered ground to be considerably more than that of the bare ground."*^ 

 There are distinct differences between various cover crops in their influ- 

 ence upon the water content of the soil. 



However, if cover crops are started so early in the season that a 

 considerable amount of growth is made during July and August, or even 

 early September, they are likely to make serious drafts upon the water 

 supply of the surface soil, which might check the vegetative growth of the 

 trees prematurely and reduce the size of the fruit. Striking evidence on 

 this point is furnished by an experiment in which cylindrical cans were 

 filled with heavy soil from an orange grove. ^^ One was left undisturbed 

 as a check, in one a surface soil mulch was maintained and one was seeded 

 to barle^^ The experiment was started June 25, at which time the soil 

 contained 19.2 per cent, moisture. At the end of 38 days the soil in the 

 check cyhnder contained 10.1 per cent., the mulched soil 14 per cent, and 

 the soil seeded to barley 3.1 per cent, moisture. The soil seeded to barley 

 had reached its wilting coefficient 21 days after seeding. 



In certain cultural experiments in Pennsylvania the beneficial effects 

 of cover crops expressed in vegetative growth and yield have been most 

 apparent during the moist seasons, and little or no benefit has been 

 derived from their use during dry years. ^^s ^p^g rapid drying effect of 

 oats, when used as a cover crop for peaches in Delaware, has prevented 

 "the best growth of new wood to produce the maximum number of fruit 

 buds."^^ The rate of growth of cover crops as the season advances is an 

 important factor in determining their draft upon the water supply of the 

 soil from week to week. From this point of view, the ideal cover crop is 

 one which grows slowly at first but rapidly late in the season when the 

 trees do not require so much moisture and when the supply is more 

 abundant. Figures on the rates of growth, under Wisconsin conditions, 

 of some of the more common crops of the Northern states are given in 

 Table 25. The indirect influence of cover crops upon soil moisture in 

 adding organic matter to the soil and thereby increasing its water-holding 

 capacity is more difficult to estimate accurately, but there is reason to 



