170 TALKS ON MANURES. 



economical artificial manures that could be used for wheat. They 

 contain too little nitrogen. Peruvian guano containing nitrogen 

 equal to 10 per cent of ammonia, would be, I think, a much more 

 effective and profitable manure. But before we discuss this ques- 

 tion, it will be necessary to study the results of actual experiments 

 in the use of various fertilizers for wheat. 



CHAPTER XXVII. 

 LA WES AND GILBERT'S EXPERIMENTS ON WHEAT. 



I hardly know how to commence an account of the wonderful 

 experiments made at Rothamsted, England, by John Bennett 

 Lawes, Esq., and Dr. Joseph H. Gilbert. Mr. Lawes' first syste- 

 matic experiment on wheat, commenced in the autumn of 1843. 

 A field of 14 acres of rather heavy clay soil, resting on chalk, was 

 selected for the purpose. Nineteen plots were accurately measured 

 and staked off. The plots ran the long way of the field, and up a 

 slight ascent. On each side of the field, alongside the plots, there 

 was some land not included, the first year, in the experiment proper. 

 This land was either left without manure, or a mixture of the 

 manures used in the experiments was sown on it. 



I have heard it said that Mr. Lawes, at this time, was a believer 

 in what was called "Liebig's Mineral Manure Theory." Licbig 

 had said that " The crops on a field, diminish or increase in exact 

 proportion to the diminution or increase of the mineral substances 

 conveyed to it in manure." And enthusiastic gentlemen have been 

 known to tell farmers who were engaged in drawing out farm-yard 

 manure to their land, that they were wasting their strength ; all 

 they needed was the mineral elements of the manure. " And 

 you might," they said, " burn your manure, and sow the ashes, and 

 thus save much time and labor. The ashes will do just as much 

 good as the manure itself." 



Whether Mr. Lawes did, or did not entertain such an opinion, I 

 do not know. It looks as though the experiments the first year or 

 two, were made with the expectation that mineral manures, or the 

 ashes of plants, were what the wheat needed. 



The following table gives the kind and quantities of manures 

 used per acre, and the yield of wheat per acre, as carefully cleaned 

 for market. Also the total weight of grain per acre, and the 

 weight of straw and chaff per acre. 



