EXPERIMENT STATION BULLETINS. 347 



A popular test for distinguishing marl from clay may be made by plac- 

 ing a lump of the material in a basin of water and leaving it undisturbed 

 for a^ime. If it is marl it will crumble down into a loose mass, but if it 

 is clay it will be little changed by the water. 



USES OF MARL. 



Marl is sometimes found so pure that it may be burned for lime for the 

 masons' use where it can be got in solid masses fit for the lime kiln. But 

 for the farmer its main value is for a fertilizer (though the farmer's wife 

 may use it for scpuring purposes in place of whiting if it is free from]|sand 

 and grit). When marl is found on or near the farm, it is the cheapest 

 lime fertilizer he can use, as it costs nothing but the expense of moving. 

 It approaches in composition the chalk of the English farmer, and like 

 chalk it may be used lavishly without fear of injury as it is "mild lime," 

 and has no caustic properties like quick lime. 



Lime is a necessary material in every fertile soil, and no crop can grow 

 in its entire absence, and every crop removes some of the soil supply of 

 lime. But the use of lime is not confined to furnishing the small amount 

 removed by crops. A soil may have a relatively small amount of potash 

 and yet raise good crops if lime is present in good supply. The soils of 

 limestone regions are distinguished for their fertility. 



One of the good offices of marl is to promote nitrification or the convar- 

 sion of the inert nitrogen of the humus in the soil into the active form of 

 nitrates for the use of growing plants. Nitrate is the material commonly 

 in greatest demand for crops on worn out and run down soils. This mild 

 form of lime or carbonate is a great promoter of nitrification in soils con- 

 taining a good supply of humus. A good dose of marl may thus increase 

 the fertility of a soil for many years, but unless the supply of vegetable 

 matter in the soil is kept up by farm yard manure, by green manuring, or 

 some other way of supplying humus to the soil, the good effect of marl 

 disappears after a time. It is a significant fact that muck and inni-l are 

 often found together in the immediate neighborhood of light and infertile 

 soils. Muck and marl would make a good team for many a poor farm. 



Marl has a certain alkaline property and will neutralize the acids some- 

 times found in poor soils and will decompose such salts as sulphate of 

 iron, which will render any soil barren that contains one per cent, of the 

 salt. Any soil to be fertile must be either neutral or alkaline, and every 

 acid soil will fail to raise good crops. The mild carbonate of lime found 

 in marl will most cheaply and safely secure this prime condition of fertility. 



WEATHEKING MARL. 



^ As taken out of the lakes and marl beds, the marl contains a large 

 amount of water, a useless load to transport. If the material is thrown up 

 into heaps and exposed to the weather it breaks down into a loose mass 

 containing much less water. This dryer and looser mass is then in good 

 condition to be carried unto the fields and ready to be incorporated with 

 the soil. 



One serious difficulty found in handling the marl found in shallow lakes 

 is to get it on the land and in fit form for handling. As it lies in the 



