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/ % The Gem State Rural A Monthly Magazine for Idaho Farms and Farmers Vol. XIV Caldwell, Idaho, December, 1908. No. 6 Soils From a Chemical Standpoint. IV. FERTILITY. By Prof. J. Shirley Jones, Chemist, University of Idaho Agricultur Experiment Station. al It is intended in this article to dis cuss briefly the subject of the soil's fertility, and the most feasible and practical methods of arriving at prop er conclusions regarding it. What is this soil good for; what crops will grow best upon it; how should it be cultivated in order to get the best results from it? These are typical questions often asked of the Experiment Station workers. There is apparently a feeling prevalent a mong farmers that from the results of a chemical analysis, informa tion should be gained as to ex kind of crops are ques tion; for the question is some times put point blank—Is this soil bet ter for apples than for small fruit, or actly what best suited to the soil in is it better for grain than either. It is not strange that this feeling has gained prevalence among farmers; for the early investigators in this line of work rather encouraged it, and actually expected to be able from the results of their analyses to answer such questions satisfactorily. It should be said now though, that this is too . , much to expect of purely chemical soil analyses. Valuable as they are, they be made to answer such inquiries , . „ , omy in a general way. he a r may be told how much plant food there is in his soil; but unfortunately L cannot be told as vet with any nrpiirapv inst accuracy j available at a growing This is ot . ho en i, lH . n n f e U ch not saying that the solution of such, problems has been despaired of, or i has not. The soil is being made the subject of careful investigation just suoject ux « 6 . , , now and much may be expected from it in the way of practical working re BroadÉs peaking the chemical com-1 SÄ ÏÏ w|ch other investigations relative to its fer tility will have to be based. 0t ^ r j considerations than chemical compo sition, however, must always be taken into account in speaking of a soils ïta S j can great degree of how much of it is time for demands. any one crop's normal suits in be discussed. question to a depth of 12 to 15 inches, or to the subsoil if that comes closer to the surface than twelve inches. Usually it is best to take several small samples from as many different spots and mix them all together, obtaining in this way, a mixture from which a composite sample may be taken for analysis. A composite sample of the subsoil or underlying soil should also be taken from the same places. Note should be taken of the amount of gra vel or stones, sticks and other debris present. Only the fine soil, that which passes through a sieve whose holes are .5 millimeters in diameter is used for analysis. Mineral plant food is usually thought of as existing in the soil in three degrees of solubility, and therefore it is certainly not all equal ly available at any one time. There is that part which is soluble in water and weak acids, constituting the por tion that is always available or ready for use by the growing plants; that part which is soluble only in quite strong acids; and that part which is insoluble in strong acids, but 'which may be decomposed by the aid of high heat and a flux of some kind. The na ture of the solvent used in analysis will therefore depend entirely upon the object in view. If only the immediately available plant food is to be determined, then weak organic, or mineral acid is used, while strong acid is employed if the maximum amount of mineral matter that may be reckoned as plant food is te be determined. Of course the wa tet, and weak acid soluble material represents the most valuable of the soil's constituent minerals, it is made up of the easily decomposable sili ca t e g, potash, lime, phosphoric acid, etc. It is, except in alkali regions, always small in amount, and usual y is not considered sufficient alone to gupport a norma i plant growth. The | stronger acid solution will contain, in addition to the above, the more diffi cultly soluble silicates, the minerals that were in combination with the hu Rimâtes, and the more difficultly solu- j j ^\ e compounds of lime and phoS phoric acid. In many soils not over 15 to 20 per cent, of the fine earth is i soluble in strong hydrochloric acid, (gp ^ 1U5)> and the sum of the rea j]y essential compounds, nitrates, ji me ,~ potash, and phosphoric acid, is much less than this, say 2 to 3 per o n that iu most soils every 100 • ^ . i / __ -r ar ag PJ£ f d ; conceded, 97 to 98 ment, of I prruseless;- for it i/to be _ | bered that this constitu es . ... porhon «f the soil or the parti in the future, if it is cu p A erly, prot^ tte TOluble ^i^ and which o c . y . » ,. « far' ^a al the , mineral I portro n j i^ con- [ ther decomposition of this inert mat ter. Below is given a table showing the results of the chemical analysis of three soils. No. 1 is a surface soil taken from the Sub-station at Cald well. No. 2 is a soil taken near Star, Idaho, and No. 3 is a soil represent ing an irrigated tract near Hayden Lake, Idaho. The analyses were all made on the strong acid solution of the soils and therefore probably rep resents more than the limit of the sol-1 vent power of the plant roots. No. 2 j No. 3 No. 1 per cent, per cent, per cent. j Insoluble 71.72 84.51 Matter Potash Soda Lime Magnesia Iron Aluminu Phosphoric Acid Volatile Matter Humus Total Nitrogen Nitrogen as Humus It will be noted that soil No. 1 has potash than has And yet is is 87.40 .30 .52 .82 .49 .46 .37 1.10 .83 1.09 .75 .74 .61 2.88 2.89 3.24 7.53 4.65 4.08 .28 .04 .05 12.99 5.46 2.76 5.73 1.94 1.88 .24 .19 4.00 4.88 considerably more either of the others, possible that more of that in No. 3, for instance, is available for imme Generally speaking, how diat0 ug0 . ev ^ wou i(i be safe to assume that ^ oge so ij s wb i Cj> have as high a per cent of potash so i ub le in strong add &g the are rich enougb in the p«oii v soluble forms of this . 'A ^ n(L 1 I As for the In* ° content, the percentages as shown would indicate a . sufficiency cf this expound pro vided it emsted in the soils as a a - bonate. U "^tunate.y the * * fSÄ not snown in me taoie; . to? small for one to assume t the lime is in that form. A.. - less then existsi as a silicate, e as sumption that ^h is lacking m ac tive I 11 ?? compounds s p ^ rect. The phosphoric acid in o 1 and 2 is low, too low in xa considered sufficient tor tne n ^ e a growing crop. No,. 3 has an a - dance of total phosphoric » that soil is ;an acid one, .and therefore much of its phosphoric , unavailable until something is aone neutralize its acidity. on of less respond to a liberal application oi Hnie which is a material most com "veVteS*Ä "eteii-Tt!| Th^mvoj.«.. matter should ^ includes also the water that ha« fa SSdcS combination, A c j av m irht have a high per-j A ^ ^ uallv be deficient in organic sub-i however manures. It is to be remembered here that humus varies much in composi tion; the richer it is in nitrogen the more fertile will be the soil containing it. The percentage of nitrogen in the humus was not determined in No. 1 but in No. 2 and 3 it was found to be 4.88 per cent, and 4,00 per cent, re ; spectively. This is low and indicates ( either that the humous in each case has been exhausted of its nitrogen or that it was formed from organic ma terial not rich in nitrogen, In the case of Nos. 1 and 2 it is not known what has been the origin of the humus now in them, but No. 3 seems to have derived its stock of this important ingredient largely from that class of plants which possess but little nitrogen. Sorrel, and a similar growth of vegetation, is character istic of the tract from which that soil was obtained. The important fact is this; Nos. 1 and 2 need more humus, and No. 3 needs humus of a better quality; and this emphasizes the point made in a previous article that when an effort is made to increase the stock of humus in a soil, care should be ex ercised in seeing that it shall be hu mus of the best possible quality. It requires no more time to spread and plow under a good grade of manure than it does a poor one; to plow un der a growth of peas or other nitro gen gathering crop, than one which does not gather nitrogen, and the bet ter grade of either fertilizer used in the potential fertility of the ^ , ,. ., A few words now regarding other considerations tnan its chemical com position, which should always be ta ken into account when the fertility of a so ji | s un der discussion- One soil gent recen tjy f 0 r chemical examin ation wag f oun( j by mechanical sep ara ^ on ^ con sist of 65 per cent, small rocks and pebbles, and 35 per cent. ?" " rtl V Si "" « " the sample was taken correctly, the fing eartb was analyzed and found to ver y go0( | j n go far as the com ndg necessary f or p i an t nutrition ^ concerned. The experienced far mer would reflect at once, however, tbat j n this soil, even though the small rocks would offer no serious hinder ance to cultivation, the sum total of p j ant f 00( j wb i c h growing crons could draw upon in that soil would be rela tive]y when com pared to an equally rich fine earth not diluted, so ^ gpea £ g0 large a percentage °f notorial not yet even reduced to rwar/l*«. P »toÄ? fart Æ these ime 'rocls property^describ ^d^as^ïvju ^ an important cons:deration in irriga ted sections. Again, instances are quite frequent, when a fairly rich, jj ne earth M ig g0 8 haUow that the sec tion in question should not be consid ÏÂ creases land far more than does the poorer one. the