66 EFFECT OF PHOSPHATES 



to dry up. By May 25th the untreated plot had begun to crack and 

 by June 7th it was difficult to find a square yard of this plot that 

 was not traversed by a big crack. On this date also the first signs of 

 'cracking' were observed on the slag plot, but the cracks required 

 looking for and were of small dimensions. The dense growth on Plot 17 

 was obviously taking much more water from the soil than was the 

 case on Plot 16 where the growth was negligible and where a large 

 proportion of the surface was bare (see Table XV). The data presented 

 in Table XXXV and Figs. 13 and 14, however, afford some explana- 

 tion of these differences. On May 10th, Plot 16 (untreated) contained 

 29 % of water, whilst Plot 17 contained approximately 26 %. By 

 the 17th the moisture content of both plots had fallen to 23 %, 

 Plot 16 having evidently lost its moisture at a more rapid rate than 

 Plot 17. On the 25th the moisture content had fallen to 18-4 % on 

 Plot 16, whilst Plot 17 in spite of the very much larger transpira- 

 tion which was taking place from this plot contained 20-1 % of 

 moisture, a difference of 1-7 % in favour of the slag plot. The week 

 following the 25th was showery and hot, and on the 31st of May, 

 when samples were again taken, there was a surprising difference 

 between the moisture contents of the two plots to a depth of 3 inches. 

 Plot 16 contained only 19 % of moisture, whilst Plot 17 had a 

 moisture content of 23-7 %, a difference of 4-7 % in favour of the 

 phosphate plot. Plot 16 received very little benefit from the showers 

 during the week; much of the rain must have run down the cracks, 

 and the bulk of the remainder, falling on a bare surface exposed to 

 the direct rays of the sun, was evaporated rapidly. The following eight 

 days from May 31st to June 8th were dry and hot, no rain whatever 

 falling. The moisture content of both plots fell rapidly, but on the 

 8th, Plot 17, notwithstanding the much greater demand made upon 

 it, contained 18 % of moisture in the first three inches of soil, com- 

 pared with 15-9 % (the lowest moisture content recorded throughout 

 the season) on the untreated plot. The advantage of a dense crop on 

 this type of soil is fairly obvious, and it is in fact the only practical 

 method of conserving the soil moisture. 



It is difficult to emphasise the importance of this indirect action 

 of basic phosphates on this type of soil during a dry season when 

 the absence of rainfall in May and June or a small precipitation 

 makes the growth of a hay crop impossible. 



On the 10th of June the fine weather broke and during the sub- 

 sequent fortnight unsettled conditions prevailed. Even at the end 

 of a fortnight Plot 17, in spite of the rapid growth which was taking 



