170 TALKS ON MANURBS. 



economical artificial manures that could be used for wheat. They 

 contain too little uitrogt-n. Poruviaii tjuano conlaininir nitrogen 

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

 effective and profilal)le manure. But before we discuss this ques- 

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

 in the use of various fertilizers for wheat. 



CHAPTER XXVII. 

 LAWE3 AND OILBEHTS EXPERIMENTS ON WHEAT. 



I hardly know how to commence an account of the wonderful 

 experiments made at Kolhamsted, Eufjland, by John Bennett 

 Lawes, Esq., and Dr. Jo.Kcph II. (Jilbert. Mr. La wes' first sy.ste- 

 matic experiment on wiieat, rommenced in the autunm of 1H4J3. 

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

 selected for the j>urpose. 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 e.xiK'riment proper. 

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

 manures used in the experiments was sown on it. 



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

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

 had .said that " Tiie crops on a field, dimiiiisli or increa.se in exact 

 proportion to the diminution or increase of the mineral sul)stance3 

 conveyed to it in manure." And enthusia.stic gentlemen have been 

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

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

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

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

 tinis save much time and labor. Tlie ashes will do just as much 

 pood as the manure it.self." 



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

 do not know. It looks as thouglj the exi)eriments the first year or 

 two, were made with tlie expectation that mineral n'.anures, or the 

 ashes of plants, were wliat 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. 



