The Bulletin. 51 



germ-life factor of fertility live. So you see that if we keep our land well 

 supplied with humus we are to a certain degree controlling the moisture factor, 

 the plant-food factor, the ventilation factor, and the germ-life factor of fer- 

 tility in the soil. 



I consider the moisture factor of fertility the most important to the plant 

 grower, for it is the one most difficult to control, and I want to call your 

 attention to a chart showing the relative power of humus over moisture as 

 compared with sand, clay, and other soil mixtures. (See Chart 1.) One 

 hundred pounds of each kind of soil was taken in a perfectly dry state. It was 

 then filled with water until it would hold no more. It was found that 100 

 pounds of sand held 25 pounds of water, or 25 per cent of its weight. A mixture 

 of sand and clay held 40 pounds of water. A strong clay held 50 pounds. De- 

 caying vegetable matter or humus held 190 pounds of water, or almost twice its 

 own weight. A cultivated soil with some humus in it will hold more moisture 

 than the sand or clays, while a garden soil well supplied with humus held 

 nearly its own weight of water. You see from this the power of humus over 

 the moisture factor of fertility. 



Humus is always undergoing decay and wasting from the soil, unless it be 

 perfectly dry or frozen solid. How are we going to keep up the supply of 

 humus in the soil? Stable manure is an excellent source of humus, but we 

 have not the live stock on our farms to produce the manure necessary to keep 

 up the needed supply of humus over the entire farm. We must raise crops to 

 turn into the soil to keep up the supply of this most powerful agent for the 

 control of fertility. Small grains, buckwheat, corn, grass, or any similar crop 

 help; but there is another class of crops with which you are familiar — cow- 

 peas, soy beans, clovers, and vetches — which are more valuable for this pur- 

 pose. You are familiar with the action of these crops, the way they get the 

 nitrogen out of the soil air through the aid of little germs or bacteria which 

 live in the characteristic nodules or tubercles which grow on their roots. I 

 want to show you results obtained by growing these nitrogen-gathering crops 

 in rotation with the other crops of the farm, for we must grow them in rota- 

 tion in order' that each field may be benefited. I want to take you to some 

 experiment stations and show the results which have been obtained there. 

 Then I want to go with you to some farms and show you what has occurred 

 there from growing these leguminous or nitrogen-gathering crops in rotation 

 with the othor crops of the farm. I am going to take you over the country, 

 out to Minnesota and Illinois, to South Carolina, to Maryland, to Florida and 

 Arkansas, to show you that these principles and facts are universal. They 

 apply and must be followed everywhere that crops are raised if best results 

 are to be obtained. 



The next chart (No. 2) is one representing conditions found on two farms by 

 the Minnesota Experiment Station. The station was studying methods of 

 farm management. The staff found two farms lying side by side on the same 

 soil formation which had been under tillage for thirty-five years. When they 

 were first tilled the yield of wheat on both these farms was 25 bushels per 

 acre. At the end of the thirty-five years, one farm was still making 25 bushels 

 of wheat per acre; the other farm gave only 8 bushels per acre. Why had the 

 yield dropped off on this farm? The soil was examined, and it was found that 

 the soil of the first farm held a much larger amount of humus. The second 

 farm had been so managed that the humus had been wasted. What was the 

 result? The water-holding power of the soil was cut down on the second farm 

 and control was lost over the other factors necessary to root growth, with the 

 result that the yield ran down on the second farm to one-third the origmal 



yield. 



What caused this difference in the humus content of the soil of the two 

 farms'? It was found that the first farmer had adopted a rotation of crops 

 consisting of corn, small grain, and red clover. Live stock were raised on this 

 farm being fed on the roughage and some of the grain, the manure going back 

 on the land In this way the supply of new nitrogen-bearing humus was kept 

 up by turning into the soil the stubble and roots of the clover, the manure 

 from stock fed on clover hay and other products of the farm. In this way the 

 farmer was enabled to control conditions necessary for root growth. The 

 other farm was run as a straight grain farm. By the waste of humus, con- 



