156 STATE BOARD OF AGRICULTURE. 



Experiments in our laboratory show that when water is passed: 



through 100 ozs. of an air dry clay soil, 56 ozs. were retained, 

 through 100 ozs. of an air dry loam soil, 49 ozs. were retained, 

 through 100 ozs. of an air dry sandy soil, 3G ozs. were retained, 

 through 100 ozs. of an air dry muck soil, 170 ozs. were retained. 



In the first three cases the differences are due largely to the size of the soil 

 grains. In the fourth case the great capacity of the soil for water is due to the 

 large amount of organic matter present. The organic matter in this particular soil 

 amounts to over 69%. 



The presence of organic matter in a soil favors the development of the cramby 

 structure discussed above. 



4. The importance of the manner in which the simple grains of soil are com- 

 bined into composites, or crumbs, has been .discussed under (2). The manner in 

 which these composites are arranged in the soil mass — whether the soil is loose 

 and open or whether hard and compact — is even more important. 



If one takes the trouble to examine a productive virgin soil, he will find in it a 

 natural mellowness, which still exists for a time after the soil is brought under 

 cultivation. To this mellowness is due in no small degree the large crops which 

 such a soil yields. 



On the other hand a soil cropped continuously and carelessly handled for some 

 time, is found to be lacking in this mellowness. It no longer produces good 

 yields, and largely because it lacks mellowness, and largely because in this condi- 

 tion it is imable to gather and retain the moisture needed for crop production. 



In a mellow soil each crumb becomes a reservoir filled with food-laden moisture, 

 and through the openings or archways separating these crumb masses from 

 each other the roots of plants may readily travel, thus finding ready access to the 

 moisture and food stored in the crumbs. 



The really productive soils are those possessing the mellowness found in our 

 virgin soils and they possess it because proper methods are employed in their 

 tillage. These include a proper rotation of crops, the incorporating of an abund- 

 ance of organic matter in the soil, and the wise use of tools. 



Nature, left to herself, provides a crop, and usually a rotation, for the soil in 

 which: 



1. The soil is filled with roots — often perennial roots which, with frost action, 

 develop the crumbed and mellow or arched structure. 



2. The bulk of the growth is returned to build up and enrich the soil. Bees 

 may remove the nectares, birds may remove the seeds and grazing animals may 

 crop off the grasses, but after all the roughage with much of the fertilizing ma- 

 terial is returned to the soil. The wise farmer profits by the object lesson. 



Nature, however, has need of no ' other tools than the roots and frosts and 

 the multitude of animal forms which burrow in the soil, — earth worms, ants, etc. 

 The farmer must use the plow, harrow, roller and other tools. With the proper 

 moisture conditions these tools may be made to help develop the mellow condi- 

 tion sought. Every farmer should learn to recognize this proper moisture condi- 

 tion and to appreciate its importance. If the soil be too wet the use of these tools 

 may prove injurious rather than helpful. If a cultivated soil be allowed to 

 become over dry, the drying often produces a degree of compacting that the use 

 of these tools cannot overcome.* 



RAINFALL. 



The average annual rainfall for Michigan is about 30 inches. This equals 3,400 

 tons of water on every acre of land. See Cut I . 



Our average rainfall duri^ig the growing months — April, May, June, July and 

 August, for the fifteen years, 1888 to 1902, inclusive, was 13.75 inches and was 

 distributed as shown by Table I.t 



♦ See article '• The Puddlinp of Soils," p. 85. Farmers' Institutes 1902-1903. 



t This (lata wa.^ obtained throiiKli the courtesy of Mr. C. F. Schneider, ia charge of the U. S. 

 weather observing station at Grand Rapids, 



