482 INVESTIGATION BY CULTURE EXPERIMENTS 



ment and preservation, but, as stated above, the first requisite 

 is an increase in humus and nitrogen. 



There is, however, a serious difficulty to the growing of legume 

 crops, especially for clover and alfalfa. This type of soil, where it 

 has been long under cultivation, is markedly sour or acid. This ap- 

 plies to the Kansan glaciation in Missouri and to the lower Illi- 

 noisan glaciation, and especially to the unglaciated yellow silt loam 

 in the southern parts of Illinois and Indiana, and in the loess- 

 covered areas of Missouri, Kentucky, Tennessee, and Mississippi. 



In the northern glaciations this type of soil is less acid than in 

 the Kansan and lower Illinoisan, but it is usually more or less acid 

 in the middle and upper Illinoisan, in the pre-Iowan and lowan, 

 and even in the early Wisconsin glaciation, and not only in the 

 Central states, but also in New York and other Eastern states. 



In the unglaciated areas and in the lower Illinoisan and Kansan 

 glaciations initial applications of at least two tons per acre of ground 

 limestone are recommended for the yellow silt loam; and for the 

 other glaciations two tons or more may well be applied where 

 acidity is shown in the surface and subsoil and where difficulty is 

 encountered in the growing of red clover or alfalfa. 



One of the very best crops, and probably the most satisfactory 

 and profitable crop, to be grown on these yellow silt loam soils is 

 alfalfa. Its power to secure nitrogen from the air, to root deeply, 

 and to live for many years are all very great advantages for this 

 soil. Furthermore, experiments have shown that where the land 

 is properly treated with heavy applications of lime or ground 

 limestone (five tons per acre) and thoroughly inoculated with the 

 alfalfa bacteria and the alfalfa seeded on well-prepared and well- 

 manured land at the proper time and given proper care, it grows 

 luxuriantly and yields large and profitable crops on this soil, as 

 in Illinois, Ohio, and New York. On the other hand, to sow 20 to 

 25 pounds of good alfalfa seed on this soil without special and 

 proper treatment is much like throwing away about $4 an acre. 



Of course, if alfalfa is grown on this land, it should be fed on the 

 farm, in part at least, and the manure returned to the soil, not 

 only to help the alfalfa but also for other crops to be grown, such 

 as corn and potatoes, which are a very profitable crop for this soil 

 when properly enriched. 



