February, 1914 



Subsoil Water. 



All supplies of {resli water are 

 111 the lirst instance derived from 

 ilie atmospheric condensation of 

 rain ^including snow) and dew, 

 which are precipitated on the laud 

 surface and serve directly to niin- 

 ister to the needs of plant life. 

 l)f the supplies received in this 

 way, a portion soaks into the 

 land ; the amount which is cap- 

 •ible of being thus absorbed, will 

 depeawi on the texture of the soil 

 ;uid the underlying subsoil. When 

 tliis is coarse and open, the capa- 

 city of the soil for absorbing 

 water is relatively great. On the 

 other hand, in the case of close- 

 textuted soils, in which the finer 

 particles of the clay order of mag- 

 nitude predominate, the rate of 

 absorption is naturally slower. In 

 any case, when the rate of precipi- 

 tation exceeds the absorptive capa- 

 city of any soil, the excess of 

 water passes off along recjgnized 

 channels in the form of surface 

 drainage or storm water, and 

 unless special facilities exist for 

 conservation, becomes lost to the 

 area on which it falls. 



The water which is absorbed by • 

 the soil, however, tends to accu- 

 mulate and form an underground 

 reservoir. This accumulated sup- 

 ply may conveniently be termed 

 subsoil water, and serves as a 

 source from which water is drawn 

 by capillarity from below through 

 the layers of soil to supply the 

 needs of growing plants, supple- 

 mentary to the amount available 

 from actual precipitation. 



In general, subsoil water perm- 

 eates the soil, subsoil and under- 

 lying rocks. The quantity present 

 usually increases fromi the surface 

 downwards to a point varying in 

 depth according to the prevailing 

 conditions, and after that, dimin- 

 ishing as the pressure of the over- 

 lying rocks and soil increases. Un- 

 der certain conditions, it is esti- 

 mated that the amount of water 

 contained in the^ first hundred feet 

 from the surface is equal to one- 

 quarter of the total volume of 

 ordinary porous soil, subsoil, rock. . 

 In other words, this is an equiva- 

 lent to a reservoir of water 25 feet 

 in depth, or a supply equal to the 

 total rainfall over average years 

 under the conditions in question. 



It will be seen that the aggre- 

 gate quantity of water thus avail- 

 able is considerable, and it is use- 

 ful to conceive it as an actual re- 

 servoir susceptible of increase and 

 diminution, and diflering from' an 



THE GARDEN AND FIELD. 



open pond chielly in nnei^enness of 

 its upper level, this latter eflcct be- 

 ing due to obstruction of free 

 mo\emeiit by the earth within 

 which it lodges. 



Water contained in subterranean 

 reservoirs in this way moves un- 

 der gra\ity, teuaiug to How from 

 a higher to a lower levels at rates 

 which depend on the penueauility 

 of the material through which it 

 passes. Moreover, it is subject to 

 capillary movement, and thus un- 

 like free water, the upper lesel of 

 the subsoil water will tend to 

 irregularities of the ground level.. 



Under the influence of these two 

 forces the upper level of the subsoili 

 water is indeliniie ; the moisture 

 content of soi.s increasing gradual- 

 ly downwards until a point is 

 reached at which the surrounding 

 subsoil or rock is saturated- 



WeUs derive their water supply 

 from subsoil water, as also do by 

 far the greater part of normal 

 brooks and' rivers (apart from 

 storm water), and the varying 

 levels of these mark variations in 

 the level of the subsoil water by 

 which they are supplied. 



The level of saturation is known 

 as the water-table ; it is conveni- 

 ent to distinguish between the 

 level of the saturation which is ef- 

 fective in supplying capillarity, 

 from that (generally somewhat 

 lower level) at which water is 

 delivered freely into wells. The for- 

 mer is termed the , ' agricultural 

 water-table,' the latter the ' well- 

 water table.' 



The quantity of subsoil water 

 permeating the earth varies , to 

 some extent with the texture and 

 structure of the materials, and 

 these factors also influence its 

 movements to a very considerable 

 degree. Through gravds and sand^ 

 it flows with a freedom approach- 

 ing that of open streams, whilst 

 through clays and close-textured 

 rocks it may move only at an 

 imperceptible rate. When the un- 

 derlying rocks consist of permeable! 

 limestone however, large cavities 

 and fissures may in course of timg 

 ' become created, as the result of 

 the solvent action of water con- 

 taining dissolved carbon dioxide, 

 and thus form those subterranean 

 reservoirs' and channels commonly 

 termed undersround rivers and 

 lakes ; which receive drainap-e of 

 the surroundino; rocks, and facili- 

 tate cnenerally the mov^ements of 

 subsoil water. 



The limit of vertical movement 

 of soil water is, of course, the 



distance between the surface of 

 the soil and the agr. cultural water 

 tai)le, but when the latter is re- 

 moved to con-sideraiJc depths below, 

 the surlace, the water available 

 lor plant growth in this way be- 

 comes increasingly restricted. It 

 may be broadly stated that, under 

 average coudiuons, capillarity acts 

 freely to a depth of 4 or 5 feet ; 

 fairly, to a depth of 10 Icet i;, and 

 slowly, to 30 ieet or more. 



In certain cases, especially those 

 of very heavy low-lying lands, the; 

 water-table may a,,proacn \ery 

 near to, or even rise above, the 

 soil surface. Under these condi- 

 tions, lands become water-lodged, 

 and it is then necessary to l6wer 

 the level of the water taole tiy 

 drainage, to permit of the lands 

 being utilized. 



In districts liable to suffer from 

 drought it is obviously a matter 

 of 'importance agriculturally to 

 know whether the reserve supply 

 of subsoil water, available ,or 

 eking, out the rainfall, approaches 

 the surface to within 10 feet, or 

 comes within 30 feet, or lies so 

 much deeper as to be beyond the 

 reach of capillarity. 



Moreover, a proper appreciat.on 

 of the conditions go verning supplies! 

 of subsoil water is of importance 

 in relation to attempts to utilize 

 them as industrial and domestic 

 sources of water. In the foregoing 

 article the main principles relating 

 to this question have been out- 

 lined. — Agricultural N'ews. 



♦ 



The Age Limit. 



As a result of experiments made 

 in Wisconsin, U.S.A., it would ap- 

 pear that a cow reaches her best 

 during the fifth and sixth years of 

 her life ; up to that age, if the 

 cow is in normal condition, the 

 production of milk and butter .fat 

 increases. As regards the length 

 of time that a cow will maintain 

 her maximum production, this de- 

 pends largely upon her constitu- 

 tional strength and the care with 

 which she is fed and managed. A 

 good averaee cow, properly man- 

 aged, should remain at ber best 

 productive standard almost unim- 

 paired until after she is ten years 

 old. Generally speaking, a cow" 

 may be said to have passed her 

 best after her tenth year, though 

 manv excellent records have been 

 made bv older individuals. 



