99 



FKIJTIM'I'V nv SOILS OK HANCOCK COi:.\TV, IMdA.NA. 



liY 



li. II. Caku, II. S. Ci)1m:i..\.m) .\.\1) K. Ckntzleb. 



riUPlK TiNIVKUSITV. 



TIkmc .-lie !it IcMsl six fiicldis wliicli .iic rccojiiiizod as essential in ci'op 

 Iiroductioii Mild ;ill ai-c thoii^dil to lie of ahout equal importanee ; these are 

 titflit, tn<ti.'<tiirc, tviniKidl lire, .vccf/, /ildcc for seed to f/roir, and sufficient 

 food- for itx i(x(\ Of these the (iiic most easily controlled is the last men- 

 tioned or food for its u.se. There are at least ten food elements neces.sary 

 to si'ow crops and of these sufticient earhon. hydrogen, oxygen and sulphur 

 soem 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 ixitassium, 65 lbs. of magnesium per 

 rotation, and at least 150 lbs. of nitrogen for every 100 bii. 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 lbs. per acre whereas the amount of 

 ])liosphorus 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. 



PI (HI of Procedure. 

 One hundred representative soils were collected in the usual way in 

 August, 1918, by Mr. Coi^eland 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 litrnvi."?. 

 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 Sutnman/. 

 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 



