On Guana or Sea fowl Dung—and Experiments on the Culture of Mangel Wurzel. Communicated in a Letter to Sir JOSEPH BANKS, Bart.

To the Right Hon. Sir Joseph Banks, K.B. President of the Royal Society.


BEING, much indebted to you for a Communication on the subject of GUANA, or SEA-FOWL DUNG, which first led to its being noticed as a manure on this island, I beg leave to present you with the accompanying “REMARKS on the CULTURE of MANGEL WURZEL ;” in which you will have the gratification of observing the very powerful effect of the GUANA, when contrasted with HOG'S DUNG and ASHES, or with land unmanured.

I have the honour to be, with great respect,
Your most obedient humble Servant,

St. Helena, 15th October, 1811.


My attention was accidentally directed to the culture of mangel wurzel, which is the white or sugar beet, lately so celebrated in Prussia, by observing the rapid vegetation of its leaves, and the frequent cuttings obtained from solve plants that were set out on the 6th February from a seed-bed sown on the 3d January, 1809 : but it was not until the 21st of June following that I resolved to try the effects of manures ; and, accordingly, a portion of the transplanted mangel wurzel, being 130 plants, was left without manure : 81 plants had a top dressing of hog's dung and ashes, at the rate of about 30 loads, or 360 bushels per acre, and the remaining portion, containing 48 plants, was treated in the same manner with Guana, or sea-fowl dung, in the proportion of only 35 bushels per acre.

If I had predetermined to report on these experiments, I should have made them in a more regular form ; that is, I should have allowed an equal number of plants to each ; but under the circumstances which have led to them, the result shall be given, exactly as they were recorded at the periods of cutting the leaves, and when the experiments were completed.

The three first cuttings not having at the tinge attracted my notice, were not weighed ; I have therefore taken them in the following Table, at the proportions of the 4th, 5th, and 6th cuttings, which is a fair presumption, as they are in general, most productive in the early stages of their growth.

TABLE I.—Exhibiting the Produce in Leaves of 259 Plants of Mangel Wurzel at Plantation-house Garden, from Seed sown on the 3d January, transplanted on the 6th February, and manured on the 21st June 1809.

The plants were placed in rows, two feet asunder, in a blackish stiff soil ; and at the distance of one foot in the rows. An acre planted in this manner would contain 21780 plants ; 48 plants are therefore very nearly (as entered in the Table) the 454th part of an acre ; because 48 × 454 = 21792. In the same manner the other proportions are deduced.

Observing the produce in leaves had diminished at the last three cuttings, and that they ahd also been much infested with caterpillars since they began to decline, I had the roots taken up on the 17th January 1811. From the 22d November to that time the growth of the leaves was inconsiderable ; they were, however, cut off close to the crowns, and the whole, after being pruned of the small fibres, weighed 1196 pounds.

As the roots of the experiment lots were not separately weighed, I deduce their respective produce in the following manner.

As the total weight of the leaves,

Is to the total weight of the roots ;

So is the weight of the leaves from each experiment,

To its proportion of the roots. Then,

lbs.   lbs.   lbs. : lbs.  
2358 : 1196 : :   507 : 257    no manure
2358 : 1196 : : 1093 : 554½ Hog’s dung and ashes
2358 : 1196 : :   753 : 384½ Guana, or sea-fowl dung.

These results being reduced to acreable produce, in the same manner as the leaves in the preceding Table, will be as follows ;

No manure, 257lbs. × 167th = 42919lbs. or 19¼ tons of roots per acre.

Hog’s dung and ashes, 554½lbs. × 269th = 149160lbs. or 66½ tons of roots per acre.

Guana, or sea-fowl dung, 384½lbs. × 454th = 174563lbs. or 77¾ tons of roots per acre.

Now the acreable produce in leaves and roots from each experiment will stand thus :

  Total acreable
Produce of the
Leaves & roots.
No manure 38     tons + 19¼  tons = 57¼  tons
Hog’s dung and ashes 131      + 66½   = 197½  
Guana, or sea-fowl dung 153¼   + 77¾   = 231     

These results are manifest proofs of the great benefit of manuring the lands. They likewise shew the surprising effect of the Guane, from which it may be inferred, that 35 bushels of this manure are equivalent to 35 loads of hog’s dung and ashes ; or, or in other words, that one bushel of the former is, in effect, equal to twelve bushels of the latter.

The fluctuations that were found, at the periods of cutting the leaves, in the effects of these two manures, are rather remarkable, and not easily to be accounted for. The general effect of the Guana, during the whole period from the 21st June 1809 , was superior to the hog’s dung. Yet this last, on six occasions, exceeded the others : but as this and other comparisons, may be made, and a variety of deductions may occur, upon inspecting the following Table, it would be superfluous to add any particular observations.

TABLE II.—Shewing the Produce of Forty-eight Plants of each Experiment, and the Fluctuations in the Produce of Leaves, at the Periods of Cutting.

All the products correspond as nearly as could be expected, with those computed from three different proportions of an acre, in Table I.—it is a proof there can be no material errors in the calculations.

When the roots were taken up, on the 17th of January last, very few of them were in a decayed state; some had rotted in the centre: but, in general, they were sound and good ; not­withstanding they had remained above two years in the soil ; that is, from the period of sowing the seed. The four largest roots weighed as follows :

No. 1 28 pounds.
2 11 ditto.
3 19 ditto.
4 20 ditto.

Having thus detailed these experiments, I shall now proceed to offer a few remarks, which will shew the important benefits that might soon be derived from a general, and extensive culture of this excellent vegetable.

It certainly possesses advantages over every other plant hitherto introduced in field culture.—Its produce is immense, and I have found it to grow, with considerable luxuriance, upon land where no other vegetation was ever seen.[1] It has also the singular property of being unmolested by an insect (I believe the dolphin fly) which is here extremely destructive to cabbages, turnips, and radishes. I have very often observed, where alternate plants of cabbage and mangel wurzel were growing in the same rows, and touching each other, that whilst the former were absolutely anni­hilated by that destructive insect ; not one was to be seen on the mangel wurzel leaves. This extraordinary circumstance seems to favour Lord Bacon's notions (however much they have been exploded) that some insects “breedeth of dew and leaves in spring ; and commonly when the East winds have much blown—the cause whereof is, the dryness of that wind ; for, to all vivification upon putrefaction, it is requisite the matter be not too moist."

But, whatever may be the origin of those insects, it is of little consequence to the present subject. I have merely stated a fact, which may possibly attract notice, and may be of some use to those who are engaged in the contemplation of matters of this nature.

The mangel wurzel, when fairly established in the soil (which, like every other crop upon an extensive scale, ought to be just before the expected rains in January and February, or in July and August), will soon acquire such vigour as to become almost independent of rain : for having a tap root, penetrating 12 to 18 inches, or more, into the soil, it will always find sufficient moisture, at that depth, for carrying on the process of vegetation. In the course of five or six months, from the seed, if sown or planted in good soil, three cuttings of the leaves may be obtained, which may average about three pounds from each plant ; and the roots will then have attained the weight of five to ten pounds each. Wherefore it seems to me, after every attention I have given this subject, that the most profitable culture would be to take three cuttings of the leaves, and at the third cutting, to dig up the roots:—these, as well as the leaves, afford a nutritious food for cattle, sheep, hogs, &c.—The leaves are also an excellent substitute for spinage.

It is very probable that a more abundant produce from mangel wurzel than appears in my experiments, might at all times be secured, if the lands were manured, and carefully prepared for its reception, and the proper seasons of sowing and planting attended to. In a piece of strong land, at Plantation-house, newly broken up, without being manured, some of the plants from seeds sown on the 3d of January, were set out on the 6th of February, 1809.—On the 11th of October following, I sent on board His Majesty's Ship Lion, fifty of those plants, which were the finest I had ever seen. The following were the weights and circumferences of the five largest :

  Weight of the whole plant.   Circumference of the roots.
  lb. oz.   ft. in.
No. 1 41 3   2 1
2 39 1   1 9
3 39 6   1 10
4 38 0   2 0
5 37 14   1 11

At Long Wood, Colonel Broughton has lately taken up some very fine specimens from land that was not manured : they were of six months growth from the seed—the leaves had been cut twice. Many of the roots weighed from six to ten pounds each but admitting even the lowest of these rates, and allowing one pound of leaves at each cutting, the produce would be eight pounds from each plant; which, at 20,000 plants to an acre, would be 160,000 pounds, or about 70 tons per acre, of nutritious food for cattle, in the short period of five or six months from the time of sowing the seed. Can any thing place the importance of the culture of mangel wurzel in a more obvious point of view than this deduction ?

But the largest plant that has yet been produced here, is one I sent to England, with several others, in July, 1810.—It was raised from seed, put in the ground on the 3d of March, and transplanted to land newly broken up, on the first of May, 1809 ; when it was taken up in July (that is, at sixteen months from the period of sowing) the circumference of the crown of the root measured 37 inches. It had about twenty strong horizontal branches, two or three inches in diameter.—The leaves and small ends of those branches were cut off, and weighed 52 pounds. The root and remaining parts of the branches on it, in the state it was sent to England , weighed 63 pounds.—In all, the weight of this one plant, from unmanured land, was 115 pounds. I have been since informed it was by far the largest of the kind ever seen in England.

15th October, 1811.

  1. This was determined by an experiment I made soon after my arrival here. I selected a barren ridge, between two deep ravines, on the north-west side of High Knoll. From its situation and declining surface, no moisture could be retained. On the 27th August 1808 it was trenched, and on the following day sown with sixteen different sorts of seed, so that it had not the advantage of the meliorating effects that might have been derived from exposure to the air and atmosphere. For a long time there was no appearance of vege­tation ; at length, in the beginning of April, 1809, seven months after sowing, and when it had been soaked by the rains, I observed the drill of mangel wurzel one connected line of fine thriving plants : the fifteen rows of other seeds, excepting a few of the rape, had not vegetated. This is a positive proof that mangel wurzel would grow in almost any soil or situation. The seeds which were sown at the same time as the mangel wurzel, were coffee, cotton, wheat, barley, oats, peas, buck wheat, spring tares, luccrne, burnet, sanfoin, silla, chicory, rape, and sunflower.—Not a plant of any of these, except the rape, which soon after died, ever appeared.

 Section XI