314 



P. G. JARVIS 



removed at this stage in order to accelerate any effects which the different 

 soils might have on seedling performance. 



Shortly after planting, plaster resistance blocks (modified Bouyoucos 

 type; Jarvis, P.G., i960) were inserted with the long axis vertical, so as to 

 have as much soil [c. 4 cm) above as beneath them. 



Three different soil-water regimes were practised on each soil. In one 

 (treatment i) the bowls were watered 3 or 3 times a week, depending on 

 the weather, and (with the exception of one occasion) no measurable 

 SMTs (i.e. no SMTs above 0-2 atm) were allowed to develop. In the other 



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03 



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1A.7.59. 



17.10.59. 



20 Days 



Fig. I. The soil moisture tensions (SMTs) in atmospheres which were allowed to 

 develop in the five soils during the course of the experiment. The broken line represents 

 moisture treatment 3 ; the sohd line, treatment 2 ; and the blacked in area, treatment i. 

 Vertical lines indicate watering. 



two treatments (treatments 2 and 3) watering took place, as closely as 

 could be arranged, when SMTs had reached i-2 and 2-5 atm respectively. 

 The actual range of SMTs over which watering took place can be seen 

 in Fig. I. Watering was with deionised water (Elgastat) which was always 

 added until the soil was thoroughly saturated throughout. 



The experiment was conducted in a cold fully-ventilated glasshouse. The 

 leaves were removed from the plants on 17 October 1959, to prevent an 

 unnaturally long growing season, and the plants were subsequently 

 harvested. * 



