92 



and of barley) followed the ploughing-in, or the feeding-off, of 

 mustard than of tares, this being contrary to what would be 

 expected from scientific considerations as to the power of tares to 

 utilise atmospheric nitrogen, a power not possessed by the mustard 

 crop. 



Whether this unexpected result was due to the particular 

 nature of the soil in question or to considerations of moisture, 

 mechanical condition, etc., was unknown, though one set of 

 experiments conducted at the Pot-culture Station seemed to point 

 to the fact that if the tares were plentifully supplied with water 

 all through the growing period, then they would give the better 

 succeeding cereal crop. Such conditions, however, could not 

 obtain in practice, and the experiments had no further interest 

 beyond showing that the experience of the superiority of tares 

 on a heavy soil, where moisture is better retained, may in this 

 way be accounted for. Repeated analyses of the soils and of the 

 crops grown and ploughed in or fed off had shown more nitrogen 

 to" accrue from the growing of tares than of mustard, and yet, for 

 some reason, it could not be utilised for the following corn crop. 



1923. 



In renewing the enquiry by pot-culture methods, it was now 

 determined to try the addition to the soils of the respective plots 

 (the soil being taken direct from the plots in the fields), of 

 materials such as lime, superphosphate, and sulphate of potash, 

 and to see if these brought about any change. 



The quantities so added were : — 



Lime ... ... at the rate of 2 tons per acre. 



Superphosphate (30%) ,, ,, 3 cwt. ,, 



Sulphate of potash (90%) ,, ,, 1 cwt. ,, 



These were used both singly and, in a fourth instance, all of them 

 together. The additions were given to the soils previous to sow- 

 ing of wheat, they being mixed with the whole of the soil, and 

 wheat was sown on December 23rd, 1923. 



In the case of Stackyard Field soil, the green crops had been 

 fed off by sheep in 1922; in that of Lansome Field the green crop 

 had been ploughed in. In each field wheat had been sown in 

 November (1922), so that the crops in the field and at the Pot- 

 culture Station were in the same stage. 



(a) Stackyard Field Soil. 



The plants grew satisfactorily, and up to the middle of 

 February no changes were noticeable. Then, however, the tares 

 series as a whole looked rather better than the mustard. Also 

 the pots in which lime had been used, either alone or in conjunc- 

 tion with the two mineral manures, began to show to advantage, 

 both with tares and with mustard ; these differences remained 

 more or less throughout the summer. The influence of super- 

 phosphate and of sulphate of potash was hardly apparent. 



The weather was very unfavourable in June, and when 

 warmer weather came in July it was almost too late to allow the 

 plants to benefit fully. 



It should be noted here that the entire Stackyard Field series 

 was somewhat inferior to the Lansome Field series. 



