212 



EXPERIMENT STATION RECORD. 



3G6 samples of soils taken at three different depths in 122 different localities in 

 the State, the average results of which are given in the following table: 

 Plant food in loxoa soilts. 



Soil area. 



Number 

 of samples 

 analyzed. 



Total 

 calcium. 



Total 

 inorganic 

 carbon. 



Total 

 organic 

 carbon. 



Total 

 nitrogen. 



Total 

 phos- 

 phorus. 



Total 

 potas- 

 sium. 



In pounds per 2,000,000 pounds 

 of surface soil (fi-fJ'i inches). 



Missouri loess 



Mississippi loess 



Southern Iowa loess 



Wisconsin drift 



lowan drift 



In pounds per 4,000,000 pounds 

 of subsurface soil (SJ-^O in.). 



Missouri loess 



Mississippi loess 



Southern Iowa loess 



Wiseonsm drift 



lowan drift 



In pounds per 6,000,000 pounds 

 of subsoil {20-40 in.). 



Missouri loess , 



Mississippi loess 



Southern Iowa loess 



Wiseonsm drift 



lowan drift 



Pounds. 

 12,059 

 10,912 

 10, 522 

 18,975 



22,838 

 19, 766 

 20, 418 

 29, 401 

 18,199 



34,805 

 32,620 

 35,576 

 257,9.54 

 24, 795 



Pounds. 



117 

 90 

 74 



135 

 97 



162 

 132 

 107 



382 

 168 



288 

 138 

 118 

 48,727 

 258 



Pounds. 

 48, 895 

 51,320 

 55,424 

 69, 730 

 57,211 



67,934 

 65,061 

 71,976 

 98, 765 

 74,169 



.55,041 

 49, 140 

 48, 876 

 54,825 

 42, 637 



Pounds. 

 4,017 

 4,110 

 4,464 

 5,458 

 4,526 



5,265 

 5,2.32 

 5,596 

 8,011 

 5,716 



4,110 

 4,037 

 3,909 

 4,255 

 3,372 



Pounds. 

 1,538 

 1,361 

 1,368 

 1,395 

 1,289 



2,697 

 2,204 

 2,089 

 2,217 

 2,207 



3,892 

 3,003 

 2,972 

 3,253 



2,889 



Pounds. 

 33,875 

 31,100 

 32,584 

 28,742 

 22,247 



67,382 

 64,069 

 65,984 

 55,800 

 48,019 



96,372 

 91,980 

 93, 119 

 77,500 

 72,380 



From these analyses it is concluded that " there is not an inexhaustible supply 

 of either phosphorus or potassium in the soils of the State," although " if the 

 content of the soil in these constituents to a depth of 40 in. is considered the 

 'life' of the soil may be considerably lengthened." Maintenance of the supply 

 of potash requires less emphasis at this time than the keeping up of the supply 

 of phosphorus. It is pointed out that in many cases it is just as essential, if not 

 more so, with many of the soils to maintain suitable moi-sture and air conditions 

 by proper cultivation, and to keep the soil " sweet " by means of ground lime- 

 stone and well stocked with organic matter by means of green manure and barn- 

 yard manure as it is to keep up the plant food supply by means of fertilizers. 



Analyses of gumbo and peat soils are also reported. The infertility of gumbo 

 soils is said to be due to their physical condition rather than to a lack of plant- 

 food constituents. Physical methods of treatment of such soils are urged with 

 possibly the application of phosphoric acid to insure their continued fertility. 

 The addition of plant-food constituents is said to be also unnecessary for peat 

 soils at present, but proper physical treatment is particularly needed, together 

 with a system of cropping. 



An investigation of the carbon-nitrogen ratio of the various soil tyi^es of the 

 State showed, that, not only in the surface soils but also in the subsurface and 

 subsoils, in no case was the ratio narrow enough to show the lack of easily 

 decomposable matter. 



Soil acidity and the liming of Iowa soils, P. E. Brown, F. B. Howe, and 

 M. E. Sar (lotca Sta. Bui. 151 {191J,), pp. 156-200, fig. i).— This bulletin dis- 

 cusses causes and effects of soil acidity, reports comparative tests of methods 

 of detecting soil acidity, and gives the results of examinations for soil acidity 

 of the various classes of Iowa soils. A study of the sources, kinds, and methods 

 of application of lime compounds best suited to correct acidity in these soils 

 is also reported. 



