No. 7. DEPARTMENT OF AGRICULTURE. 235 



their minute size it is easy to understand why the food must be iu 

 solution, for these little hairs cannot absorb anything of a solid 

 nature. As the root progresses in the soil the root-hairs dry up 

 and new ones are produced back of the root cap, so that the roots 

 are ever foraging in fresh soil. Since these root-hairs are the only 

 parts of the roots engaged in taking food from the soil, and as they 

 are always near the remotest tips of the roots it is easy to see why 

 the man who runs a big plow through his corn and tears off the roots 

 is depriving the plants of the power to get food from the soil till 

 new rootlets are formed. 



Knowing these facts in regard to plant life, how shall we apply 

 them in the improvement of the fertility of our soils? The import- 

 ance of the moisture-retaining character of humus in the soil will 

 be better understood when we fully comprehend the need for the 

 solution of the plant food for the minute root-hairs. There are a 

 number of elements that must be supplied in the soil water iu order 

 that plants may live and grow, and if any of them are entirely absent 

 the plant cannot thrive. These elements are nitrogen, potassium, 

 phosphorus, magnesium, sulphur, sodium, iron, chlorin, silicon and 

 calcium. Some of these are only used in minute quantities and some 

 only by certain plants under peculiar conditions, and most of them 

 are in such abundance as to be practically inexhaustible. Those 

 which are used freely by all crops, and most apt to become deficient 

 in the soil are nitrogen, potassium and phosphorus, and in rare cases 

 calcium or lime. Nitrogen, potassium and phosphorus exist in 

 smaller amounts than other essential elements iu all soils, and are 

 most rapidly taken up by crops. They exist in greatly varjdng 

 amounts iu dilTerent soils. A soil may be rich iu nitrogen like the 

 black prairie soils of Illinois, and yet be deficient in phosphorus, as 

 has been shown there, and in hill lands like those of southern Il- 

 linois, potassium may be abundant, while both nitrogen and phos- 

 phorus are deficient. Some years ago I was invited to lecture at 

 an Institute in one of the southern Illinois counties, and the sub- 

 ject assigned me was the restoration of worn out land. It seemed 

 odd to me that Illinois farmers were already considering the exhaus- 

 tion of their soils in a section formerly known as Egypt, from its 

 great productiveness. When I reached there, however, I found that 

 reckless farming and bad treatment of the soil resulted in the same 

 conditions in Illinois as they do elsewhere, and I found washed 

 hillsides and unproductive soils there, just as they exist in the up- 

 lands of the South and from the same causes. When I was a young 

 man I was engaged in making railroad surveys from Minnesota to 

 Texas. On the rolling prairies of the Grand Divide in northeastern 

 Missouri they were then just turning the raw virgin sod, and they 

 laughed at the idea that their soil would ever need manure, and 

 boasted that they made 25 bushels of wheat per acre while eastern 

 farmers made 10 to 15 bushels. But last year the farmers of Mis- 

 souri paid two million dollars for commercial fertilizers, for their 

 lands had gone down to 10 and 15 bushels of wheat per acre, w^hile 

 the lands in eastern and northern Maryland had gotten to making 

 40 bushels of wheat per acre in many counties. They have found 

 that the essential elements for crop production can be exhausted 

 in any soil, and that to keep up production some means must be 

 taken to repair the waste. Single cropping has brought the famous 



