REPORT OF TEE CHEMIST 151 



SESSIONAL PAPER No. 16 



Plot ' A.' Though during the 24 weeks of the investigation the moisture content 

 is seen to fluctuate considerably, it is invariably greater in the ' cultivated soil.' This is 

 strictly in accord with theory, based on experimental data. The soil in crop loses more 

 moisture by capillarity than that cultivated, and also parts with a considerable amount 

 by transpiration through the leaves of the clover. 



The greatest differences, especially during the earlier months, are observable when 

 the precipitation is least. Thus, on May 6, the total rainfall to date was only 1 *33 

 inches, and the excess of moisture in favour of the ' cultivated ' land was practically 130 

 tons per acre. At this time there was a vigorous growth of the clover, and much 

 moisture was consequently being withdrawn from the soil for its development. This 

 teaches an important lesson, as it is from May 1 to the middle of July that we wish par- 

 ticularly the trees to be supplied with all the moisture necessary for their growth. The 

 value of cultivation during this period, if the season is dry, will be proportionally much 

 greater than if there is a fair rainfall. The season of 1901 during its earlier weeks 

 shows a fairly well distributed precipitation, but nevertheless, the data fully confirm 

 this conclusion. 



Rainfall. Ex ? ess °/ f . W **"fi P e ' acre > 



in cultivated land. 



Inches. Tons. Lbs. 



May 6 133 129 1,566 



20 274 68 583 



June 3 2 13 91 1,710 



17 1-31 154 669 



July 2 173 103 1,415 



The converse of the proposition considered in the preceding paragraph is also true : 

 The greater the precipitation, the less the difference in moisture content between the 

 6oil of the crop-covered and cultivated plots. In illustration of this, we might refer to 

 the differences for May 20, June 3, and August 12, recording the largest rainfalls. 

 The heaviest fortnightly precipitation of the season is for the two weeks preceding the 

 last mentioned date, viz., 4 *17 inches, when the difference in favour of the ' cultivated ' 

 soil is only 5 tons per acre. 



From the 1st July the system seeks to provide the orchard soil with a cover of 

 vegetable growth, which serves (1) to utilize any excess of soil moisture, thus check- 

 ing the development of the tree and promoting the ripening of its wood, (2) to fur- 

 nish the roots of the trees with a protection against frost, (3) to enrich the soil in 

 humus and nitrogen, and thus improve it mechanically and chemically, and (4) to 

 assimilate and retain the nitrates formed during the summer months. It is with re- 

 gard to the first of these only that we shall now present data. 



Plot ' A.' — Commencing with July 15, it will be noticed that in the cultivated 

 soil, as heretofore, there was always an excess of water over that present in the soil 

 supporting a growing crop. In other words, there was invariably less soil moisture 

 available for those trees where the clover was growing than for those in the bare and 

 stirred soil. This is more readily seen from the subjoined table: — 



Decrease in amount of Water, 



Rainfall per acre ' due fco S rowtn ot 

 Cover crop and capillary 



action. 



Inches. Tons. Lbs. 



July 15 126 85 1,557 



29 137 121 5 



August 12 4-17 5 717 



26 -29 46 893 



Sept. 10 -52 110 1,686 



23 168 33 505 



Oct. 7 193 54 1,644 



21 -67 26 138 



Any extended comment on these results is unnecessary, their character is suffi- 

 ciently pronounced to tell their own story. The amounts of water which may be con- 



