138 



may also aid in a study of the probable rate of availability. Thus, if I may 

 offer an illustration, we find that the ordinary brown silt loam soil of the 

 Illinois corn belt in the Early Wisconsin Glaciation contains in the surface 

 soil twice as much potassium soluble in hydrochloric acid as is contained in 

 the si'ay silt loam soil of the Illinois wheat belt in the older Lower Illinois 

 Glaciation, although the total potassium content of the soils in these two great 

 areas shows no such proportionate difference. Thus, chemical analysis plainly 

 indicates that potassium in the one soil will be made available much more 

 readily than in the other; and in actual practice we find that the application 

 of coiiimcrclal potassium to the one soil produces no increase in the corn crop, 

 whereas when applied to the other soil potassium increases the yield of corn 

 by ">() i)ei' cent, amounting to 20 or 30 bushels increase per acre under favorable 

 conditions. 



IIow to liberate from the soil's inexhaustible supply sufficient potassium to 

 supplement that which can be returned in farm manure, and thus meet the 

 needs of maximum profitable crop yields, is one of the problems to be solved 

 in a system of permanent agriculture. We are still hoping that this may be 

 accomplished by means of decaying organic matter, and to this end we are 

 using not only all available farm manure but also green manures, especially 

 nitrogenous green manures from legume crops. 



The fourth (luestion relates to the addition of commercial plant food, when 

 necessary, to supplement that which can profitably be liberated from the soil's 

 supply. 



The truck farmers of New Jersey will do well to follow the teachings and 

 experiments of their agricultural experiment station and make liberal use of 

 commercial nitrogen, and thus hasten the maturity, improve the quality, and 

 increase the yield and value of their market-garden crops, even to the extent 

 of .$180 per acre, as Director Voorhees has done at New Brunswick ; but for 

 the general farmers of America to try to raise 2.500,000,000 bushels of corn 

 with lO-cent nitrogen, at an annual cost of $400,0()0,0(io, is not only absurd 

 but it would be impossible, for there is no ade(piate commercial source for 

 such sui)plles of nitrogen. All of the information thus far obtained justifies 

 the conclusion that for the general farmer who practices a suitable rotation 

 of crops and makes in-oper use of legume catch crops and of manure which 

 may be produced on the farm the purchase of commercial nitrogen is both 

 unnecessary and unprofitable. Well-inoculated legume plants will thrive even 

 in soils devoid of nitrogen if they are well provided with lime and the mineral 

 elements of plant food. There is no great nitrogen proV>lem, for it was solved 

 by Ilellrlegel and Atwater and others more than fifteen years ago. 



On some soils of limited extent, as the i>eaty swamp lands and some sandy 

 lands, ai)]ilicatioiis of ]K)(assium must be made. This may be in the form of 

 farm manure i)rodnced from crops grown on lands rich in potassium, or com- 

 mercial i>otassium salts from the German mines may be used; but on our 

 normal agricultural lands of glacial origin, with a supply of total potassium 

 in- the plowed soil suflicient for large crops of grain for twenty centuries and 

 with subsurface and subsoil ecfiiall.v rich in potassium, the corn and wheat 

 helt has no great potassium problem except to liberate that element as needed 

 from the soil. I can not speak for the cotton-belt soils nor for those which arc 

 required to grow tobacco, but it seems noteworlhy that by the ultimate analysis 

 of 4.S samples of Mai-yland subsoils, com])rising 12 different soil formations. 

 Veitch found that the general average composition of normal soils in tliese 12 

 formations" shows less than 1,200 i»ounds of phosphorus and more than ."{o.OOO 

 pounds of potassium per acre for a T-inch stratum assiuued to weigh 2.000,000 

 pounds. This agrees ver.v closely with, the average composition of Illinois 

 surface soils. 



So far as can be ascertained from the analytical data at hand and from the 

 use of connnercial jdant food in agricultural i)ractice, the more connnon glacial 

 loessial. and residual soils of the United States contain an iunnense store of 

 total potassium and a very limited amount of phosphorus. There are of course 

 notable exceptions, such as the fanums " liluegrass regions " of Kentucky and 

 T'ennessee. which are thoiight to bear some relation to the natui-;il i(hosi)liate 

 deposits in that section, where some soils exceedingly rich in phosphorus are 

 found. Attention is called to the fact that three-fourths of the potassium 

 required for a crop of corn or wheat remains in the stalks or straw used as feed 



"Four other formations, including sandy truck soils and sand and other bar- 

 ren soils reported by Veitch, are omitted from this average. 



