Field-Experiments on Permanent Pasture. 433 



of 5 cwts. of potash salts and 5 cwts. of mineral superphosphate 

 per acre, which was employed on Plot 4, gave an increase of 

 only 10 cwts. and 5 stones per acre, or barely more than the 

 common salt on Plot 6. 



As the addition of superphosphate to g;uano on Plot 9 had a 

 beneficial effect, the maximum produce being obtained on that 

 plot, it is impossible that the combined effect of potash salts and 

 superphosphate upon grass land, can be less favourable than that 

 of potash salts alone. Notwithstanding all the care and pre- 

 caution which the experimenter may take in conducting field 

 experiments, he must be prepared to find his experiments vitiated 

 in a great measure if he undertakes occasional field trials upon 

 land, the adaptability of which for field trials has not been 

 specially tested in previous years. This circumstance is a source 

 of frequent disappointment and prevents in a measure the con- 

 tinuation of field experiments by practical farmers, who as a rule 

 are not in a position to set aside one or more fields exclusively 

 for experimental purposes. 



Whatever may be the value of the grass experiments at 

 Crook's Farm as a guide to others, they no doubt will have 

 shown to Mr. G. P. Smith that the productive powers of his 

 permanent pasture may be greatly and, I doubt not, profitably 

 increased by the judicious application of manures which, like 

 the mixture of guano and superphosphate or good farmyard 

 manure, incorporate with the soil to which they are applied, all 

 the elements of fertility, the removal of which in the produce, 

 without an adequate restoration, must inevitably lead to the 

 gradual exhaustion and deterioration of grass land. 



Judging from the effects which Peruvian guano produced on 

 Plots 7 and 8, Mr. Smith's pasture appears to be specially 

 deficient in available nitrogen and in phosphates ; for it will be 

 seen that the guano alone nearly doubled the produce, and that 

 the mixture of guano and superphosphate produced fully twice 

 as much grass as the average yield of the two unmanured plots. 



Some of the manures which were used in the preceding ex- 

 periments produce, it is well known, a more immediate effect on 

 grass land than others which act but slowly, and for that reason 

 are more permanent in their effect upon pasture land. When 

 manuring experiments upon permanent pasture are taken in hand, 

 it is not enough to weigh the produce of a single season, -but the 

 experiments should be continued for a period of not less than 

 four years in succession. This has been done by my friend and 

 former pupil ^Ir. G. Y. Wall, of Durham, who, in 1869, began a 

 series of experiments on permanent pasture, all the results of 

 which he communicated to me for four years in succession. 



VOL. X. — S. S. 2 F 



