GROWTH RESPONSE OF SUGAR BEET 341 



was watered, freely. Metered quantities of tap-water were applied, with a 

 hand-rose in Exp. i and with a mobile overhead sprayhne in later experi- 

 ments. Soil moisture was determined routinely on samples from the 0-12 in. 

 layer. Flints made sampling at lower levels impracticable. 



The crop was sampled on six occasions in Exps. i and 2 and on four 

 occasions in Exp. 3. In Exps. i and 2, one 3 ftx 3 ft area of crop (nine 

 plants) and in Exp. 3, two 2 ft x 3 ft areas (six plants each) were taken at 

 each sampling. 



The plants were separated into roots and tops, and the tops were sub- 

 divided into laminae and stem plus petioles. The fresh and dry weights of 

 each part, the total leaf area and the number of Hving leaves were then 

 determined. Leaf area was estimated by the method of Owen (1957) in 

 Exp. I, and by the scanning planimeter (Orchard, 1961) in Exps. 2 and 3. 



Details of Experiments 



Experiment i (1958) and Experiment 2 (1959) 



These experiments were similar in design and will be discussed together. 

 The plots received 10 cwt/acre of a compound fertihser containing 7% N, 

 7% P2O5 and 10-5% KgO. The seed, was sown in mid- April. In 1958, 

 seedlings were planted on the plots 21 days after sowing, butini959 plant- 

 ing was delayed 14 days, so that an attack by Rhizoctonia spp. could be 

 controlled. The A plots were maintained near field capacity throughout 

 and no water was apphed to the C plots after June 25, except for i in. 

 between the fifth and sixth samphngs in 1958. These treatments were 

 comparable in the two experiments, but the B treatments differed (Table 

 i). The 1958 regime was intended to produce water stress but no wilting; 

 the plots were rewatered as soon as the soil moisture content reached 15%. 

 Two drought cycles of this type did not affect growth, and a third, more 

 severe, cycle was given, so that the recovery from drought could be 

 studied. 



In 1959, therefore, drought was continued until growth was significantly 

 affected. The drought was then broken by ^ in. of water, but there was no 

 further watering for 8 days ; the plots were then returned to field capacity. 



The three treatments were repHcated in four randomised blocks. 



Experiment 3 (Autumn, i960) 



The stubble left after an experiment on barley was burnt with a flame-gun 

 and rotary cultivated. No fertihser was added. Before sowing the barley, 2 

 cwt/acre of a compound fertihser containing 13 % P2O5 and 13 % KgO was 



