Campbell's 1902 Soil Culture Manual. 



31 



not to let any crust form under the mulch. We are of the opinion that 

 many corn crops have been seriously injured by that condition, when with 

 no more available moisture the crop would have come out all right had it 

 not been for this crust. 



The best possible condition for rapid, healthy growth of plants is 

 when the soil is fine, firm, and as full of moisture as it will naturally hold 

 from the mulch down. This condition can be kept if the mulch be finely 

 pulverized hy catching the soil at the proper condition after the rain, hold- 

 ing it a proper thickness and recultivating as soon as the top of the firm 

 soil begins to show the least indication of dryness, providing, however, that 

 a sufficient amount of moisture has been stored below before planting the 

 crop or during its growing period. 



KEEPING THE MULCH IN CONDITION. 



There are many important reasons why great care should be taken 

 to keep the mulch in perfect condition and prevent the loss as far as possi- 

 ble of any moisture by evaporatiou from the surface of the soil. The fol- 

 lowing paragraph taken from Prof. King's book on "The Soil"' conveys 

 some important information along this line. We quote this because it bears 

 the figures of his own practical observation at various depths in the soil, 

 showing the effect not only of the surface soil getting too dry but of light 

 showers. He says: 



"When the surface soil has its water contents reduced so the upper 

 6 to 12 inches is beginning to get dry the rate of capillary rise of water 

 through it is decreased and it begins to assume the properties of .a mulch. 

 But when this condition has been reached if a rain increased the thickness 

 of the water film on the soil grains without causing percolation the capil- 

 lary flow may be so certain that the surface foot draws upon the deeper soil 

 moisture at a more rapid rate than before, causing a trans-location of the 

 lower soil moisture, the deeper soil becoming measurably drier soon after 

 such a rain than it was before, while the surface foot is found to contain 

 more water than has fallen upon it." 



He cites the following experiment, as proof of this important prin- 

 ciple. At 5:30 p. m. samples of soil were taken on a piece of fallow ground 

 in one foot sections to a depth of four feet. Water was then applied to 

 this surface at the rate of 1 3^ pounds to the square foot. Samples of soil 

 were also taken adjacent to this wetted area to serve as a control experi- 

 ment, and nineteen hours later corresponding sets of samples were again 

 taken with the result stated below: 



