Q6 The Bulletin. 



barley, clover, and wheat was one of the rotations practiced. The turnip crop 

 has decreased from 10 tons in 1848 to less than one ton in 1908, which was 

 the last crop of turnips. In the same year, 1908, where the land had been well 

 fertilized the yield was 20 tons of turnips per acre, or double that in 1848, 

 while the unfertilized land gave less than a ton per acre. The information is 

 really abundant upon this subject, from this country and other countries. If 

 you are going to grow crops, 5'ou must feed them. If food of any kind is not 

 abundant in the soil, you must put it in. 



So we come to the subject of plant food. There are ten different and abso- 

 lutely essential elements of plant food, and if any one of them is withheld you 

 cannot make a grain of wheat or a leaf of clover. Every one of the ten ele- 

 ments is absolutely necessary for the growth and maturity of every plant. The 

 names are as easy to learn as the names of ten men. Why should we not know 

 them? Why should not they be taught in the schools? 



Two of the ten elements come from the air — carbon and oxygen — taken in 

 through the leaves in the form of carbon dioxide, a compound that ought to 

 be familiar to us. One of the ten elements comes from water — hydrogen. 

 Seven of them come from the soil for all crops. In addition, one of the seven 

 may be taken from the air by the bacteria which live upon the roots of the 

 legume jilants in root nodules. ' 



I would like to emphasize the importance of adding vegetable matter to the 

 soil. It is easy enough to add other things, but the greatest practical problem 

 in American agriculture is to maintain the vegetable matter in the soil, the 

 material from which humus is made. In an hour's time I can put enough 

 limestone on an acre of land to keep it sweet for ten years, but to add nitrogen 

 and vegetable matter by growing crops and turning them under takes time, 

 dei)en<ling directly upon the growth made. I might emphasize the fact that 

 North Carolina will never enrich her soils with manures taken out from the 

 cities. I suppose that all the manure that could be gotten from the cities of 

 North Carolina could be used to advantage in one county. We never build up 

 the land in great areas in that way. Vegetable matter must be grown on land 

 by the farmer, not bought. 



Two elements, besides the three I mentioned, do not need to be given serious 

 consideration. They are iron and sulphur. Iron is contained in all soils in 

 such abundance, and it is required so little, that no soil has ever been found 

 that needed more iron. The element sulphur is contained in the soil in only 

 moderate amounts. It is taken out of the soil by crops in quite considerable 

 amounts. How nuich is necessary and how much is merely tolerated by the 

 plant? We know that much of it is merely toleratetl and is not needed; but 

 how much is absolutely essential we do not know. We know that plants con- 

 tain a lot of sodium, the element contained in common salt, but that is not at 

 all necessary. We know that plants contain silicon, but that it is unnecessary. 

 Merely because we find a lot of sulphur in the plant is not proof that the plant 

 has to have all the suljihur it contains. If that were the case, with soils con- 

 taining little sulphur, when more sulijhur is added the yield would increase. 

 But it has never been established that the addition of sulphur has increased 

 the yields of ordinary farm crops. 



There are five other elements, every one of which needs consideration. Tv\'o 

 of them can be gotten in the form of limestone. All limestone contains cal- 

 cium, and much of it contains both calcium and magnesium, two of the abso- 

 lutely essential elements of plant food. So far as I can learn from the data the 

 world affords, calcium is much more important for its own value as a plant 

 food than is potassium for use on normal soil. From data we have on soil 

 investigating. I am thoroughly convinced that calcium contained in limestone is 

 more valuable and more important than potassium. The soil contains ordi- 

 narily many times as much potassium as calcium, and yet we buy potash and 

 put it on the soil and usually ignore the calcium. Even magnesium, when 

 measured by the requirements of the crops, the content in the soil, and the loss 

 by leaching' is more important than potash by the same method of estimation. 

 You may be interested to know that in England they applied, in three different 

 plats of"^ ground, potassium sulphate on one, magnesium sulphate on another, 

 and sodium sulphate on another, and as an average of twenty-four years they 

 got exactly the same yield to the tenth of a bushel. And sodium is not one of 

 the essential elements of plant food at all. 



