Essays in Natural History and Agriculture

by Thomas Garnett

Total for statute acre L2 0 0

Speculating on the probability of a dry summer, I gave it an extra quantity of manure, and I think where guano is used afterwards, as it is by me, the nitrate of soda might be dispensed with, which would bring the cost to L1 2s. 6d. per acre. I should prefer guano to nitrate of soda, because of the phosphates contained in the former. At the distance we are from the sea (about thirty miles) it would seldom be necessary to apply common salt, as the gales of winter generally bring as much as is needed; but last winter we had no high winds, and I thought that where salt was applied with other chemical manures, the wheat was more luxuriant than where there was none; but owing to a misunderstanding of the instructions to that effect, the produce was not kept separate. When the chemical manure was applied, one land was left without, for the purpose of comparison. Guano was sowed on the land on the 29th March, at the rate of something less than 2 cwt. to the statute acre, one side of the field being covered with Peruvian, the other with African, and the land on which no chemical manure had been sowed was half of it covered with guano, and the other half left without anything except lime; but as it was thought desirable to ascertain the value of the chemical manure without guano, half of this patch was sowed with the chemical manure in April, after the long drought of the last spring had set in. A small patch was left without manure, to show the natural condition of the field, and to serve as a comparison with the manured part alongside it, and also with the condition of the field when the experiment commenced, 1841-2, when the unmanured portion yielded only 19 2/3 bushels to the acre. This part of the experiment, however, was frustrated by the carelessness of the men who thrashed out the wheat. The crop was a very good one throughout the field, but was evidently shorter and thinner where there was no lime, and also where guano was applied alone. It was best on the headlands where more lime had been applied. The weather was extremely favourable until the wheat was going out of bloom, but it then changed, and the crop was beaten down by the rain, in some places so thoroughly that it never rose again; and from that time to the day it was reaped (21st August), there were not more than six fine warm days. This cold and ungenial weather would, no doubt, materially affect both the quantity and quality of the crop,—the sample only being just fair. On thrashing out the crop, I find the result to be as follows:—Where the guano and chemical manure were applied, but no lime, the yield was 49 1/5 bushels of 60 lbs. per statute acre; where the land was left unsubsoiled, it was 52 1/2 bushels; when guano alone was applied, it was 42 1/3 bushels; where the chemical manure alone was applied, it was 43 1/2 bushels; where the African guano was applied, it was 45 bushels; where the Peruvian was applied, it was 52 2/3 bushels; on the headlands, where three times the quantity of lime (or 3 1/2 tons per acre) was applied, it was nearly 62 bushels; and where six times the quantity of lime (or 7 tons to the acre), it was 49 2/3 bushels. I give this last result as it was ascertained, but do not consider it conclusive, for the wheat plant on this headland looked quite as well as the other, until it went out of bloom, when from some unknown cause it was partially blighted; an irregular patch from a foot to a yard in width and extending almost from end to end of the headland becoming brown and parched, as if affected by lightning or some atmospheric visitation. With the view of making these results a little clearer to the eye, I subjoin the following tabular statement of the produce per acre in the different parts of the field:—

Bushels of 60 lbs. per statute acre.

Guano alone 42 1/3 Chemical manure alone 43 1/2 Guano and chemical manure, with 24 cwt. lime to the acre, but land unsubsoiled 52 2/3 Guano and chemical manure, but no lime 49 1/5 African guano and lime 45 Peruvian " " 52 2/3 " " and 3 times as much lime 62 " " and 6 " " 49 2/3 Average crop throughout the field 50

It may be as well to observe, that the total expense of manure, and of its application to that portion of the field which produced sixty-two bushels per acre (including the guano and the additional quantity of lime used), was at the rate of 81s. per statute acre. Deducting the cost of the nitrate of soda, the utility of which, under the circumstances, I am inclined to doubt, it would have been 63s. 6d. I consider these to be very favourable results, and as offering strong inducements to continue the experiment. I have accordingly had the land ploughed up and cleaned; and it was again sowed with wheat on the 9th inst. Having detailed the general results of the experiment, I beg to offer the following remarks upon some points in it, which seem to me to require a little elucidation. I consider the success of this experiment to be in a great measure owing to the use of soluble silica and magnesia; because, although there is an abundance of silica in the soil, my first crop showed very miserable results, the grain being ill-fed and poor, and the straw soft and discoloured, although the year 1842 was, in this district, very favourable for wheat, the month of August being singularly fine and warm; but when I combined the nitrate of soda with sulphate of magnesia, as in experiment No. 1 in 1843, but still more so when I combined it with the silicate of soda, as in No. 3 of that year, the straw became as strong, firm, and bright as need be desired; and this year when both these salts are combined with nitrate of soda, common salt, and gypsum, I have not only good and bright straw, but also an abundant crop of wheat.

With respect to the lime used, it may be as well to state that the field had not been limed for many years, and although in a limestone district, showed a deficiency of lime on analysis. The soil is a strong loam, on a brick clay subsoil, in which there is little or no lime, although the stony clays, which form the subsoil in a great part of the district, abound in it, containing from twenty to thirty per cent. of carbonate of lime. I had always believed that lime was used in great excess in this neighbourhood, and had, in fact, an idea that its good qualities were overrated, inasmuch as it does not enter into the composition of the plant, except in very minute proportion; but last winter I saw a paper (by Mr. Briggs of Overton) on the possibility of growing wheat on the same land year after year, in which the utility of lime in preventing rust was incidentally touched upon. I also saw Liebig's letters explaining the action of quicklime in liberating potash from the clay; and then I considered it very important to ascertain the proper quantity to be applied. The quantity required to decompose the phosphate of iron was not great, and assuming Liebig's theory of its action in liberating the potash to be true, it seemed to me that an excess of lime would permanently impoverish the land; for, supposing that the crop required 100 lbs. of potash, and as much lime was applied as liberated 500 lbs., what became of the 400 lbs. which did not enter into the composition of the plant? was not a large portion of this 400 lbs. washed down the drains by the rain, and so lost for ever? Perhaps the absence of lime in this field accounts for its beneficial action in the experiment just detailed; but if my supposition is correct, that any excess of potash which may be liberated from the clay by the use of quicklime (that is, any more than may be required to perfect the crop), is washed down the drains, and thus the land is permanently impoverished by the excessive use of lime, it behoves landed proprietors to ascertain what is required, and they should take care to apply no more than is necessary. This caution is most particularly needed in this neighbourhood, where lime is cheap, and where the opinion is prevalent that the more there is applied the better it is for the land, and where it is common to apply ten or twelve tons to the acre. I have stated above that chemical manure was applied to a small portion of the field after the setting-in of the drought in April. The action of this manure showed that a good thing may be very injurious if applied at an improper time; for, although it produced a stimulating effect on the plant immediately after its application, there was too little moisture in the land to dissolve it thoroughly, and thus enable the plants to appropriate it, until the rain came, about the end of June, when the wheat had been in flower some time; but the stimulus was then so great that all the plants threw up fresh stalks (from the roots), which were in flower when the wheat was cut, and it was then found that they had not only impoverished the plants, but had prevented the grain from ripening. This was the case not only in the experimental field, but in several others also, where the chemical manure was sowed after the setting-in of the drought. When the field was sowed with guano, it was thought desirable to cover one part of it with the African, and the other with Peruvian, for the sake of comparison; but as the African did not appear to produce the same stimulating effect as the other, fifty per cent. more was applied, that the cost might be equal (the Peruvian cost 10s., the African 7s. per cwt.); but as the latter application of the African was made when the wheat was just shooting into ear, the same objection applies to the experiment which does to the chemical manure applied after the drought had set in—viz., that there was not sufficient moisture in the soil to dissolve it thoroughly until the plant was too far advanced to benefit by it; and therefore its failure would be no proof of the value of the African as compared with the Peruvian, which was the object of the experiment. It is true, no bad effects followed the application similar to those produced by the misapplication of the chemical manure in dry weather, yet if soluble salts like the latter did not find sufficient moisture in the ground when applied in April, there is reason to suppose that the former would not do so when applied in May. I regret the failure of the experiment without any manure, as I think the result would have shown satisfactorily that the land is so far from being impoverished by this system of cropping, that it is improving every year. I think, however, that this is shown by the produce of the land manured with guano alone. In the first year's experiment the produce from guano alone was 27 bushels per acre, and both straw and wheat were very indifferent in quality. This year the produce from guano alone is 42 1/3 bushels; and although neither straw nor wheat are so good as upon the adjoining lands, they are both very much better than they were in 1842. It will be observed that the result from the unsubsoiled portion is very good, and if nothing more were said about it, people would be led to conclude that there was no advantage in subsoiling. But this, in my opinion, would be a great mistake; for to say nothing of the advantage which the unsubsoiled portion would derive from the drainage which it received from the subsoiling on each side of it, I found, when the field was ploughed up this autumn, that whilst the unsubsoiled portion was stiff and heavy, the subsoiled part was comparatively friable and loose, like a garden, and will, I expect, show its superiority in the succeeding crops. It must be borne in mind, in reading these experiments, that we have here one of the most unfavourable climates in the kingdom for growing wheat, from the excessive quantity of rain that falls, three times more rain falling annually in the north of Lancashire than at York, and this, no doubt, is very prejudicial to the success of such a series of experiments as I have been detailing. It has been objected to these experiments, that allowing all to have been done which is here detailed, it leads to no important conclusion; for although it may be practicable to grow wheat every year, in a small field like the one experimented on, it is not so on a large scale. But the objectors should remember that there is not the seed of a single weed sowed with the manure; and therefore if the land is thoroughly cleaned, and kept so, by hoeing the crop in the spring, it will require very little labour to fit it for another. But I shall be better able to speak on this head next harvest, having sowed wheat on an oat stubble with once ploughing. It is said there are no weeds in Chinese husbandry, and if they can eradicate them completely, so may we, if we adopt the same methods and follow them up as perseveringly. Again, admitting that it is not practicable to grow wheat on the same land year after year on a large scale, yet if we can double the crop in those years in which we do grow it, by the application of chemical manures (and the same manures are applicable to all cereal crops), will not that be a conclusion worth arriving at? That it is possible to do so, is, I think, sufficiently shown by the results I have obtained. What, then, may we expect when these experiments are infinitely multiplied and varied, under the superintendence of skilful and experienced men, who will devote their whole time and attention to the subject? Will raising the average produce from twenty-five to fifty bushels per acre be the utmost limit to which improvement can be carried? I believe not. In conclusion, I would urge on all owners and occupiers of land, the importance of devoting at least a small field to agricultural experiments, as I think there can be no doubt that, if these are carefully and systematically made and followed up by agriculturists generally, we shall be so far from needing an importation of corn in average years that we shall have a large surplus to spare for our neighbours.

NOTE.—In the use of silicates of soda and potash one precaution is very necessary—viz., that you really have a soluble silicate, and not a mere mechanical mixture of ground flint and soda: this is a very different thing, and one, if it be not carefully guarded against, which will lead to nothing but disappointment. Again, the silicate may be properly made in the first place, but in a long exposure to the atmosphere the soda attracts carbonic acid, and the soda is liberated, and this has defeated my expectations more than once. Again, though I consider it desirable to defer the application of it until vegetation has fairly started in the spring, yet, in one instance, I delayed the application of it so long, that there was not moisture to dissolve it until the end of June, and then the wheat began to shoot afresh from the roots and the crop was seriously injured by it: but this was in an exceedingly dry spring, and might not happen again for many years.

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To the same.

LOW MOOR, 18th December, 1845.