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THE TROPICAI, ACmCVLTURlSt, [March j, i 



from; nii.l therefore tliere is no loss from storeage. 

 So, in buying sulphate that has been in stock for 

 some timti, the arlvautnge is likely to be on the side 

 of the biivoi- ; but nitrate increases in weight by 

 absorbing raoioture, and is conse<iuently reduced or 

 attenuated in valr.c to a corresponding extent. The 

 advantage to a purchaser, in being able to go to the 

 nearest gas-works, and exami.ve and (if he desires it) 

 analyze the sulphate before purchasing it, is evident. 

 In order to place the Hothamsted eiperiments in 

 their proper light, it will be necessary to indicate the 

 l)lan of operation, as described in the memoranda ; 

 and also to glance briefly at a few general principles 

 respecting the use of manures. Sir, .T. B. Lawes was 

 the founder of the Rothamstod experimental station. 

 Soon after entering into the pos.session of his hereditary 

 property there, in 1834, he commenced a series of 

 trials in different manuring substances, first with 

 plants in pots, and afterwards in the field. Of all 

 the experiments so made, those in which the neutral 

 phosphate of lime — in bones, bone ash, and apatite — 

 was rendered soluble by means of sulphuric acid, and 

 the mixture applied for root crops, gave the most 

 striking results. These results, obtained on the small 

 scale, led to more extensive trials. A permanent 

 laboratory was established in 1843 ; and from this 

 date down to the present, a permanent staff of 

 chemists, a.ssistants, botanists, clerks, &o., has been 

 maintained at the station, in addition to chemical 

 assistance in London, Berlin, and elsewhere. The 

 whilu has been maiutivined entirely at the cost of the 

 owner, who has further set apart a sum of £100,000, 

 as well as certain areas of land, for the continuance j 

 of the investigations after his decease. The general 

 scope and jilan of the field experiments has been to [ 

 grow some of the most important crops of rotation, 

 each separately, year after year, for manj years iu 

 succession, on the same land, without manure, w|ith 

 farmyard manure, aud with a great variety of chemical 

 manures; the fame <lescription of manures being, as 

 a rule, applied year after year on the same plots. 

 Experiments on an actual course of rotation, without 

 manures and with different manures, have also been 

 made. These experiments included wheat, barley, 

 oats, beans, clover, turnips, sugar-beet, mangel-wurzel, 

 potatoes, and grass. Samples of all the crops are 

 taken and bro-jght to the laboratory, where weighed 

 portions, after being partly dried, aro preserved for 

 reference or further examination. The experiments 

 upon them include examination for water aud ash — 

 sometimes the complete analysis of the latter--and 

 the .determination of nitrogen, whether as albuminoids, 

 amides, or nitric acid. Iu the case of wheat, the 

 experiments have extended to the flour obtained from 

 it; the sugar from the beet, mangel-wurzel, and 

 potatoes has been determined; and the botanical 

 composition has also received careful attention. A 

 large number of samples of soil, at various depths, 

 have been taken and analyzed ; also tested for absorptive 

 capacity, as regards w.iter and ammonia. Again, the 

 rwiifall and drainsge have also been the subjects of 

 many cxpcrimeiitB ; aud the amount of water trans- 

 pired by pljnis. the assimiUtion of nitrogen, and 

 .'*th«f topics, have also rficelvy! attention. Sotiiv very 

 '■)i!i»u.st)«'p cxpei'iiueB.tii ou utiieisb bsve bpen iijcluded ; 



i'mcl, altboutjli tnunj' of the fedults of tb« iavcstigatious 

 lave been given to the world, as abONe mentioned, a 

 arge i<roportion remains unpublished. 



k general glance at the operations comprised in the 

 wtoie l)roceSs of praparing laud, for the purpose of 

 growing crops i( m.y kindj is necessary to enable u,s 

 to appreciate the pirt played by the addition of 

 manures to the soil. The mechanical conditions of 

 the soil have a most important effect, and tlie laborious 

 work ineideiital to diggiug, ploughing, or otherwise 

 preparing the land is undertaken for the purpose of 

 rendering the soil light and porous, and of reducing 

 6ome portion of it at least to a state of division suffici- 

 ently fine to enable the various constituents contained 

 in "it to be assimilatid by the plants. For the 

 f.iribrnnre of th's purpose, the farmer usually looks 

 tj tUki ijiUral pbwuuwtBu el (itiu or wist, •» » source 



of the necessary moisture; though sometimes this is 

 supplied, wholly or in part, by artificial means. But 

 the soil must not be so moist as to cake together ; 

 and therefore the drainage of the land, for the purpose 

 of removing any excess of moisture, forms an important 

 department in agriculture. Kven after every care in 

 the way of properly working up the laud, much 

 depends on the weather ; so it is evident that only 

 by means of such gigantic and long-continued experi- 

 ments as those the records of which we are now 

 considering, can any accurate information, suitable 

 to form data for the formulation of rules for the 

 guidance of the agriculturist, be obtained. 



It is evident that manures may directly affect th« 

 soil only, and through this medium afford the desired 

 benefit to the crop; or they may be fitted for direct 

 assimilation by the roots of the plants, and inert as 

 regards the soil. Three kinds of action are recognized 

 by the agriculturist. These are, first, mechanical action, 

 such as when sand is added to a heavy clay soil to 

 render it lighter and capable of maintaining the 

 desired condition of fine division; secondly, chemical 

 afftioT^, as when a substance is added which induces 

 actual chaHges in the constitution of the soil, as 

 shown by analysis, which render it more suitable for 

 the support of the desired crop ; aud. in addition 

 to these, there are the rather obscure results known 

 as "physiological action." Examples of all of these 

 are afforded by the experiments before us. AVith 

 regard to the latter, wo may remark that the proverb 

 '* What is one man's meat is another man's poison " 

 applies with equal force to the \egetable kingdom. 

 Most remarkable experiences are ou record as to the 

 strange effect of certain substances ou vegetation — 

 results for which chemistry is quite unable to account. 

 Nitrate of soda appears to act directly upon the 

 roots of the plants, without in any way atlecting the 

 soil. It is a very qui^k-acting manure, and but for 

 this it would be almost useless ; as, on account of its 

 ready solubility in water, it passes away with the 

 drainage. Indeed, it appears that a considerable 

 proportion of it must always be wasted iu this way. 

 Sulphate of ammonia is entirely different in this 

 respect. The soil has a sort of affinity for this 

 substance; and consequently it does not pass off with 

 the drainage water, like nitrate. The ammonia is 

 gradually decomposed by the action of the soil ; the 

 nitrogen taking the form of nitrates, and the nitrates 

 would be liable to pass off with the drainage-water, 

 like nitrate of soda. In this manner, therefore, some 

 of the nitrogen of the ammonia may be lost to th» 

 plants, if the salt has been applied any considerable 

 time before it is required. Consequently, a certain 

 amount of loss may result from applying the sulphate 

 in the autumn instead of in the spring, as previously 

 obsprved. The fact that the nitrogen must be con- 

 verted into nitric acid before it is used by the plant 

 has not been lost sight of by those interested in 

 nitrate, who claimed that in this salt the nitrogen is 

 provided in exactly the form in which it is required. 

 But, as we have seen, this property is attended by 

 rapid action, which is not permanent. Some go so 

 far as to say that the nitrate leaves the soil rather 

 worse than 'bofore it was used, We have heard of 

 imtutices In which ni'r.ite was ajipllrd to grain crops, 

 aud proiluced a spltndid crop of green, but exhausted 

 its powers before maturity was reached, leaving the 

 crop in an unripe and immature condition; aud it is 

 easy to understand that heavy rains, coming late irt 

 the season, might have this effect. Sulphate, however, 

 if it does not produce such iniiKediate startling effects, 

 ' IS lovinil to impfovfl the Condition of the land. Nd 

 iWbt the chemical actions betwi en it and the soil; 

 which result in the gradual liberation of nitric acid, 

 also serve to assist the mechanical distintejration 

 which is necessiry to set free some of the constituents 

 in such a form as to be absorbed by the plant. 



While the advantages achieved by the application 

 of nitrate arc confined to the increase iu crops obtained 

 durin' the sea.sou in which it is applied, this rule 

 eanuo't be adopted in the case of sulphate. The 

 furmtr io cuiuijletely K&biuotiid iu » siuglw euMou, mi 



