25b JouiiJNAL oi- iiiE DErAKTMEKT oi' Agkicultuke. — Sept., 1922. 



the day these large leaves transpired more moisture than the roots 

 • ould take up from the depleted stock of Avater in the soil, but as 

 the evening approached the supply of water from the soil again 

 equalled the demand of the leaves. However, as the season advanced, 

 the supply of water in the soil near the trees became so small that 

 the pumpkin leaves there took on a permanent wilt, and finally the 

 plants nearest the trees died olf completely, although the crop in the 

 centre of the field was quite a good one. 



Moisture Absoeption by Trees. 



In order to ascertain to what extent the trees will dry up a soil, 

 samples were taken under one of the shelter-belts previously men- 

 tioned and also at a distance of about 50 yards from the trees. The 

 sampling was done at the beginning of January, during the rainy 

 season, but there had been a week of dry weather previous to that 

 date, thus ensuring that no recent storms or showers of rain had caused 

 a temporary acquisition of moisture to the soil near the surface. The 

 field contiguous to the .shelter-belt liad been cultivated in the spring 

 and kept clean, thus making certain that there was no loss of moisture 

 by transpiration owing to the presence of weeds or a crop. 



The total amount of moisture in each sample was immediately 

 estimated, which gave the combined percentage of both hygroscopic 

 and capillary moistuie in the soil under normal conditions. This 

 soil is a reddish, heavy clay loam, of excellent physical and water- 

 retaining properties, and from previous estimations it was fomid that 

 the amount of hygroscopic moisture (i.e. the amount of moisture still 

 left as an exceedingly thin film round each particle in a thoroughly 

 air-dried soil) it is capable of holding is roughly 5 per cent., so this 

 amount is taken from the total in each case in order to have some 

 idea of the amount of capillary moisture present, for this is the 

 moisture from w^hich plants are able to draw their supply. In fact, 

 during a period of drought, even before all the capillary moisture has 

 escaped from a soil, plants will show evident signs of wilting, and 

 when there is only the hygroscopic moisture left the crops will soon 

 die from the want of available moisture. 



From the results of the first experiment made in connection with 

 this point it was found (see table) that Ihere was approximately 50 per 

 cent, more capillary moisture in the soil away from the trees than 

 under them, although the shade and shelter of the trees would 

 naturally tend to conserve the moisture in the soil there. 



This experiment was repeated a fortnight later in the same neigh- 

 bourhood, and although a heavy storm or two had taken place in the 

 meantime, a week of dry weather was allowed to elapse before samples 

 were taken in order to ensure that the distribution of moisture in the 

 soil had approached normal conditions again. This time, samples were 

 taken at regularly increasing distances from the trees, and the results 

 in Table 3 show that there is a continuous increase in the moisture- 

 content of tJie soil up to the maximum distance of 20 yards from the 

 trees, although the increase in the last 10 yards is but small. The 

 amount of capillary moisture in the surface soil at 20 yards from the 

 trees was as much as 80 per cent, more than that in the surface soil 

 under the trees, but the increase in the sub-soil was practically the 

 same as in the first experiment, viz., a little under 50 per cent. 

 •Judging from t]ie appearance of the crop on a neighbouring portion 



