T M B 
IVIAGAZINB 
OP 
Tf)G WI)00L OF AGRIOULTUKG, 
COLOMBO. 
Added as a Supplement monihhi to the TEOPIGAL AGRICV LTV BIST P 
The following pages include the contents of the Magazine of the School of 
Agriculture for March : — 
WATER IN SOILS. 
ATER exists in soils (1) in cheniica^ 
combination as ferric and alumi- 
num hydrates, and hydrated 
silicates, and (2) in mechanical 
suspension as hydrostatic, capil- 
lary, and hygroscopic water. Water in the first 
condition is found generally at the bottom of soils, 
and being quite free to obey the law of gravity, 
it sinks down and is found in the drainage. 
Taking up the subject of water in mechanical 
suspension: permanent hjulrostatic water or “ bot- 
tom water” is that reached when soil is excavated 
as in the construction of wells : it is the source of 
capillary water. Where hydrostatic water exists 
at a shallow depth, the soil is not of the most pro- 
fitable nature, unless it be first brought under 
a thorough system of drainage. Capillary 
water is held in the pores of the soil by capillary 
attraction, and is then not free to obey the law 
of gravity. Its source as before stated is hydro- 
static water. Capillary water is of the highest 
value in keeping soils in a condition of healthy 
moisture, and its presence can be readily detected 
jU soils. 
Hydroscopic water in onlinary circumstances 
cannot be perceived. Its presence is detected by 
heating air — dried soil to 100° and holding a cold 
surface over it to condense the moisture. The 
loss in weight suffered l)y the soil through this 
operation indicates the amount of hygroscopic 
water it contained. The amount varies consider- 
ably in different soils : it usually increases in any 
one soil during night, and decreases during day. 
The hygroscopic property of soils or the power 
of absorbiwg water vapour from the atmosphere 
depends on the chemical and mechanical Con- 
dition of the soils, as well as on the temperature 
of the air. Organic substances are more hydro- 
scopic than mineral substances ; for instance wool 
will vary 10 per cent of its weight on different 
days, and that there would be an advantage in 
selling silk and woollen goods by weight. The 
power of soil in absorbing water vapour is 
generally in the same ratio as that in which it 
absorbs other gases, such as ammonia. In 
respect of hydroscopicity soils vary much. 
Silicious soil may be practicably said not to 
possess the property at all, calcareous sand shows 
it in a very slight degree increasing about 3 per 
cent of its weight, while a good loamy soil 
absorbs on an average 3'.o per cent, clay o per 
cent, and humus 12 j>er cent. The green manur- 
ing of sandy soils increases their hygroscopic 
power, and in fact the addition of any organic 
matter to silicious soils brings about this desir- 
able result. The dryness or humidity of the air 
affects the rapidity with which soils will absorb 
water, while the temperature regulates the 
amount of water absorbed. During the day, 
when the temperature is high, moisture is lost, 
and gathered at night. 
The ca^jacity of retaining moisture that has 
been absorbed is also greatest with humus and 
least with sand. According to Schloesing's ex- 
periments as given by Warrington, line sand 
saturated with water and thoroughly drained, 
retained 7 per cent, a clay soil 3d per cent, 
a forest .soil 42 per cent. Additions of organic 
matter will thus increa.se the retentive as well 
as the absorptive power of soils. 
Capillarity depends on the poro.sity of the soil. 
In sandy soilsthe pores are large andthehydrostatic 
water is little drawn up. In a clay of medium tex- 
ture capillary action is at a maximum, but if the 
clay be too ‘ heavy,’ the Aval er cannot ascend. The 
order for ca])illarity is asfolhnvs: — ordinary clay, 
humus, garden .soil, sandy soil. In sandy soils 
thoughthercis little capillarity, the water is drawu 
