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FERTILITY OF SOILS OF HANCOCK COUNTY, INDIANA. 
BY 
R. H. Carr, H. 8. COPELAND AND I. GENTZLER. 
PuRDUE UNIVERSITY. 
There are at least six factors which are recognized as essential in crop 
production and all are thought to be of about equal importance; these are 
light, moisture, temperature, seed, place for seed to grow, and sufficient 
food for its use. Of these the one most easily controlled is the last men- 
tioned or food for its use. There are at least ten food elements necessary 
to grow crops and of these sufficient carbon, hydrogen, oxygen and sulphur 
seem to be supplied naturally while iron is needed in small amounts from 
soils usually containing an abundant supply. The other five food elements 
nitrogen, phosphorus, calcium, magnesium and potassium are usually present 
in the soil in more limited quantities and are removed by cropping in a rota- 
tion to corn, wheat, oats and clover to the extent of about 75 lbs. of phos- 
phorus, 160 lbs. of calcium, 318 lbs. of potassium, 65 lbs. of magnesium per 
rotation, and at least 150 Ibs. of nitrogen for every 100 bu. of corn and its 
stalks. 
The supply of potassium in the soil is usually 20,000 lbs. (per acre 6% 
m’s) or more in all but the unusual soils. The amounts of calcium and mag- 
nesium vary from 8,000 to 10,000 Ibs. per acre whereas the amount of 
phosphorus is much more limited varying from 1,000 to 3,000 lbs. per acre 
and is usually the limiting factor in the production of crops. Nitrogen also 
is a very important element in crop production and is present in soils to 
the extent of 1,000 to 5,000 lbs. per acre. It too is often a limiting factor 
and one of the most expensive to replace unless returned through the aid 
of legume crops instead of commercial fertilizers. Thus it will be 
evident that only the system of farming which returns as much to the 
soil as the crops remove can be considered good farming and anything less 
must be termed “mining”. A chemical invoice of part of the plant food in 
Hancock County, Indiana, has just been made, and is reported here. 
Plan of Procedure. 
One hundred representative soils were collected in the usual way in 
August, 1918, by Mr. Copeland and after being air dried were ground 
and analyses were made for total nitrogen, total phosphorus, volatile matter, 
amount of calcium or magnesium present as carbonate, acidity to litmus, 
and solubility of soil in dilute nitric acid. The carbon dioxide determina- 
tion was made by treating 20 grams of soil with 10 per cent hydrochloric 
acid in such a manner that the volume of gas evolved could be determined. 
The data obtained from the above is contained in the tables which follow. 
Discussion and Sunvmary. 
The data is so arranged as to put in one group all soils containing approx- 
imately the same organic content. This has been found desirable because 
