191 1.] Summary of Agricultural Experiments. 1019 



Effect of Weeding and Hoeing on Roots (Univ. Coll., Reading, 

 Results of Expts., 1909). — This experiment has been carried out with 

 mangolds for three years, with the following results : — 





Tons per acre. 



1907. 



1908. 



1909. 



Average. 



Kept clean by hand weeding ... 



15! 



33i 

 37? 

 391 

 40 



i6f 



3°i 



36! 



38 



3H 



32* 



34 



3if 



34 



21 

 32 



36i 

 36i 

 37i 



The 1909 results are not so striking as those of the first two years.. 

 The ground had carried a crop of maize in the previous year, and was 

 thus left in a condition fairly free from weeds, owing to the successive 

 hoeings that crop received. Taking the average of the three years, 

 one hoeing added eleven tons per acre to the crop, compared with the 

 rows on which singling only and no weeding was done. A second 

 hoeing added about four tons more per acre. Further hoeing and 

 weeding by hand gave but a small increase. The fact that the hand- 

 weeded rows gave the heaviest crop appears to show that the benefit 

 of hoeing is due to the killing of the weeds rather than to improvement 

 in the texture of the soil. 



Destruction of Charlock by Calcium Cyanarnide (Univ. Coll. of N.- 

 Wales, Bangor, Agric. Dept., Bull. 1, 1909). — A preliminary experiment 

 to test the effect of calcium cyanarnide on charlock was tried at Madryn. 

 Two plots, each one-twentieth of an acre in size, were dressed with 

 calcium cyanarnide, one at the rate of 120 lb. per acre, and the other 

 at the rate of 80 lb. per acre. The charlock, of which the rough and 

 smooth leaved varieties were present, was rather irregular in growths 

 some of the plants being in full flower, while others were just com- 

 mencing to bud. The dressings were applied on June 3rd. A fortnight 

 later little or no effect could be seen, either on the charlock or on the 

 corn. All the weeds present had recovered from the temporary check 

 which they had suffered. 



Destruction of Thistles (Field Expts. in Staffs, and Salop, and at 

 Harper Adams Agric. Coll., Joint Rept., 1909). — In 1907 and 1908 

 dressings of salt and of sulphate of copper were found to have little 

 effect on thistles^ and in 1909 this treatment was given up and only 

 cutting practised. Three cuttings in the year were found so effective 

 that at the end of the second year there was little left to deal with, and 

 in the third year the plots were practically cleared. 



By checking the growth of the thistle above ground in the early 

 summer the development of the underground stem is hindered and the 

 plant cannot spread so freely. The second growth which follows is 

 not so strong, and the seed-producing stems are not so luxuriant. 

 Second cutting in July further weakens the vigour of the plant, and 

 this is further checked by the third cutting. The same treatment in 



4 C 2 



