The manual of manures

Front matter

THE MANUA OF MANURES

HENRY VENDELMAN:

THE INCREASED PRODUCTIVITY SERIES General Editor : P. Anderson Graham

Contents

CHAP. TAGB

I. Introduction i

II, Manures in General 5-31

CHAPTER I Introduction

The question of manures is of paramount importance to-day, and imfortunately it is not very well understood ; yet on its comprehension depends the future of agriculture on which, as the great war has shown, our existence as a nation must depend.

To be in a position to pay the high wages demanded in these times of scarcity of labour, the farmer must modernise his methods. And if, on the one hand, he tries to reduce the cost of cultivation by the use of labour-saving machinery, he ought, on the other hand, to increase his profits by the employment of artificial manures, as well as that of the farmyard.

But manures increase productiveness only when they are intelligently and judiciously used. It is of no use to apply a lot of manure when the increase in production is worth less than the price of that manure. It is useless to spend a great deal of money on artificial manures, if they are applied at seasons when they will be washed away in the drainage. If they are applied to crops which cannot profit economically by them, not given in the

Introduction

right proportions, or with the right kinds in association, or, above all, if by bu3dng without knowledge the usual price is paid for inferior products, a loss is entailed at the starting point.

Whatever the method of cultivation may be, the quantity and quality of the results obtained will depend chiefly on the influence of manure. Other conditions being equal, the difference in results ought to be attributed entirely to the manures, and this difference is sometimes enormous.

In some cases proper manuring may mean a twofold increase ; in others it will enable us to cultivate soils which otherwise could not have been touched.

We know, too, that between the price of manures and the extra value of crops obtained, thanks to their use, there is a large margin of profit ; but this profit ought to be derived from the judicious use of these manures, and to be able to utilise them judiciously we must understand them.

There are actually on the market such a variety of artificial manures, and they are introduced with so much skill, that it is very easy to be led astray as to their value and the use one should make of them. It is not wisdom either, on the part of the buyer, to rely solely and completely on the seller for advice as to what is useful or necessary for his purpose. He ought to know and be able to judge for Mmself.

" A Manual of Manures " will be not only useful, but essential to the fanner, and he ought always to keep it handy.

He ought to know what elements these manures bring to the soil, under what forms, and in what

Introduction

proportions. He ought to know what kinds of manure he should employ and to be able to calculate the quantities that should be applied to various crops and the seasons favourable for their application, so that they will be most profitable to the plants for which they are intended, and not be merely washed away.

He ought to know what manures can be combined without fear of loss ; how to store them for a length of time without appreciable loss ; how to fix their value on the basis of the units of the fertilising elements which they contain, and the more or less favourable form in which these elements are present. He must not blindly believe in the virtue of manures, or listen to advertising recommendations. He must demand a written guarantee of the number of units of fertilising matter and the forms in which they are presented, confirming these facts by analyses, so as to pay a price, based on the price of the day, corresponding to these units. He ought to know the principal adulterations to which these manures are liable, so as to be forewarned, and exercise care so as to buy well and cheaply.

Knowledge of the subject will prevent him from paying too much for some manures much in demand, wWch for this reason alone have attained a price much beyond their real value.

Finally, he ought to be able to account to himself for the produce which he has obtained per unit of fertilising matter at the most advantageous price at the farm, not forgetting the price of transport, which, in the poorest manures, will be proportionally higher to the unit.

Introduction

All this knowledge is necessary to enable the farmer to handle manures, and having it, he should be able to estimate the exact results obtainable instead of only waiting to see what will come of the employment of haphazard methods.

It is from lack of knowledge that many people are obliged to resort to compound manures and mixtures of all sorts, in which the unit of fertilising matter is always sold at too high a price, a price often comparable to that of the " Aqua Pompae " of old apothecaries, or the alcohol in sedative waters.

We shall say something on the subject of farmyard manure, its formation, its preservation, and its employment, and we should like to call attention to the enormous waste of it which takes place.

We shall make allusion also to green manures, without dwelling on them, however, in order not to increase the size of the book.

Not only farmers, but every one who possesses land or even a garden ought to learn about manures, especially, we think, teachers in country schools, both male and female.

We have intentionally put on one side everything that is difficult in the subject, and everything that could impede easy comprehension. The few unusual terms employed will be explained in a way to make them quite intelligible.

It is the popularisation of the knowledge of manures on which we are intent, convinced that in this direction we can be of some service.

CHAPTER II The Necessity of Manures

Plants, like all living things, require that ten elements should be put at their disposal under fixed conditions, but to give crops they do not require equal quantities of each of these elements. They show a greater need for some than for others.

Thus, among these ten necessary elements, seven are generally found in sufficient quantities in the soil and in the air.

They are Hydrogen [H], Oxygen [0], Carbon [C], Calcium [Ca], Magnesia [Mg], Iron [Fe], and Sulphur [S].

Three others exist universally and generally, in insufficient quantities to give good crops, and plants require them in relatively large quantities. They are Phosphor [P], Nitrogen [N], and Potash [K]. These are the elements which are universally regarded as manures. In certain cases the magnesia and calcium associated with these manures have also given favourable results, which seems to prove that in these pa.rticular cases there was too little magnesia and calcium in the soil, and that therefore they also became manures. But these elements are present in many manures besides, without being counted as such themselves. The movement which has been attempted in the agricultural world to popularise the use of magnesium as manure can perhaps be considered as coming from an interested source, desirous of raising the price of certain manures by the value attributed to magnesium (Stasfurt salts of potash).

Lime applied separately ought to be regarded as an improvement, and it is for this purpose and to this end that it is especially applied to the soil. It has been noticed, however, that the simple application of lime has been sufficient to render certain soils fertile. It is apparently true that magnesia will constitute a manure in future time if the soil is not regularly reinforced.

Manure, then, is all matter applied to the soil for the purpose of augmenting the quantity of plant food utilisable by the crops. The necessity for artificial manures need no longer be discussed. It has been a recognised fact for so long, and to such an extent, that any one who does not employ them can only be regarded as retrogressive.

Fertile Land.

By fertile land we mean that which contains in a form relatively assimilable, and in addition to a certain quantity of humus, up to a thousand of the chief fertilising elements. One might say that Western Europe contains practically no fertile land. The crops raised there for many ages have taken the fertiUsing elements from the soil in

Exportation

ever increasing quantities, and they have not been restored completely by farmyard manure. Therefore it is necessary to import them.

Exportation.

A more or less important part of the crops produced on the farm does not return to the soil — thus a portion of the wheat, oats, barley, potatoes, etc., grown is sold as such. These cereals and roots contain nitrogen, phosphates, potash, and lime extracted from the soil by the plants. Therefore the total quantity of fertilising elements which these products contain are taken from the farm.

Hay and straw are also sold sometimes, and all this represents an exportation of fertilising matter. On dairy and breeding farms the crops obtained are consumed on the spot. But then they are exported in the animals sold — in the shape of meat, skins and blood, bones, or in the sale of milk — and, further, there is the loss in fertilising matter between the consumption of produce by the animal and its restoration in the form of manure. These losses which are considerable, as we shall see further on, especially in nitrogen and potash, are caused by exposure to air, by fermentation, by dilution, by rain water, and by the loss of urine. The loss of fertilising elements in the air and by drainage is considerable. Those in the drains are carried to the sea and irretrievably lost.

All these depletions, by sale and loss, going on practically for hundreds of years on some soils, have ended by impoverishing them to a point where the usual restitution is not sufficient to maintain their fertility, and sometimes even to the point of ruining the land.

Restitution.

It is necessary to give back to the soil those fertilising elements which the crops have taken from it, and of which there are not enough reserves in the soils, in the form of manure.

This is usually done by means of farmyard manure. But, even under the most favourable conditions of formation and preservation, farmyard manure contains and gives back far less than the total quantity of the elements which the crops have taken from the ground, and so the latter is incapable of maintaining its fertility. Besides, simple restitution, even when complete, is no longer sufficient for our progressive agriculture. We want to get very large crops very economically. To supply the deficit of the ordinary restitution, and to increase the productivity of the soil we must have recourse to

Importation.

This means that we must turn to outside fertilising matters to restore or retain the fertility of the soil, and to increase its capacity. This importation is usually made in two different ways :

1. By concentrated foods (cake, meal, etc.) which are given to the cattle.

2. By bought manures. This second way is preferable because it is more economical.

From the manurial point of view the first way is not advisable because the units of nutritive matter,

The Law of the Minimum

which are the same as those of the manure, but in another form, are dearer than those in the manure. This means converting a product of higher value into one of lower value without counting the losses which arise in the process of transformation.

Improvements.

All modifications applied to the soil, whether physical, physiological or chemical, are classed as improvements, which, without being regarded as manures, help to ameliorate and correct the soil from an agricultural point of view. These improvements are practically as necessary as the manures.

Thus certain soils, poor in fertilising elements, have gradually lost their humus as well, because of an insufficient supply of farmyard manure. Cultural operations, aided by bacteriological influence, and natural oxydisation stimulated in most cases by the use of lime, have impoverished the soil in humus to such a degree that chemical manures alone cannot make it fertile. Humus is of great importance. Indeed, it is of such absolute necessity to the soil that it must be considered as seriously as manures. It does not constitute a manure in itself, but soil in which it is lacking is practically sterile, and it is chiefly in these soils that green manures are of the greatest service.

The Law of the Minimum.

The importation of manure is regulated by the Law of the Minimum. In point of fact, the crops are proportionate — all conditions being equal — to the amount of manure that the soil contains in the least quantity. For to obtain the whole of the effect of the given manure, the other manures must be present in the soil in the right proportions. If any one manure is lacking, the addition of other manures, no matter in what quantity, will be incapable of increasing the productivity.

Let us make this clear by means of an example.

Imagine any kind of crop. The liquid in the tub illustrated represents the crop. The tub full represents the capacity of the soil. The planks of the tub represent the manures. The planks are of different sizes, because different quantities of each manure are required ; but the height represents the proportions, which ought to be equal. The plank of nitrogen [N] is of the necessary height, but the planks of potash [K2O] and phosphoric acid [PaOg] are too low, the plank of P2OB coming higher than that of KgO. The quantity of KjO, represented by the size of the plank, is, however, larger than the quantity of P2O5 present and of nitrogen [N] necessary. The proportion of these elements, therefore, is not good.

Possibilities of the Soil

Now, in order to increase the crop, it will be of no use to raise the nitrogen plank, or the height of the water in the tub, because the crop is regulated by the height of the plank of K2O. But, raise the plank of K2O and immediately the crop will be increased in proportion to that rise. Adding to the plank of nitrogen would not increase the crop at all. One would merely have spent money uselessly.

But from the moment that the plank of K2O has passed the plank of P2O6, the increase of K2O, as far as the level of the capacity of the soil will not further increase the crop, because the P2O6 is not in the requisite proportion. This plank also must be raised to the height of the capacity of the soil. It is at this stage that the best results can be expected under the given conditions. It is the strict application of the Law of the Minimum which enables us to put waste lands into cultivation economically.

Each kind of crop has different needs and demands different quantities of manure. Therefore, knowing the requirements of a crop and the elements which are lacking in the soil, one can easily determine the respective quantities of the various manures to use, and give them in the necessary quantities when the requisite proportions have been decided. But there IS a limit to the

Possibilities of the Soil.

Manures cannot be applied indefinitely in the hope of getting a corresponding increase in crops. In spite of using good proportions, there would come a time when an increase of manure would not give a similar increase of production, and the practical limit is when the addition of manure ceases to give good extra value in the produce. In reality one would never push the practice as far as the point where the production did not do more than pay for the manures, though in theory it can sometimes be justified — say by the production of the most nourishment on a given site, thus making a larger head of stock possible.

It is often written and more often said that " basic slag or superphosphate " (of good quality, be it understood) "do not answer." Such a statement proves that the manure has not been given a sufficient trial, and, moreover, that the experimenter is not familiar with the use of chemical manures. One thing is certain. The soil lacks phosphoric acid : the exceptions to this rule are too rare to make one believe anything to the contrary. If basic slag and superphosphates do not respond, it means that they have not been given their proper complement — they cannot respond. They must be given in combination with potash or nitrogen, sometimes with both, and then they will answer. The Law of the Minimum must be satisfied.

The Selection of Manures.

It only remains to decide what manures must be used to bring their importation to the utmost limit of economic possibilities. There are in commerce such a quantity and variety of artificial and chemical manures, that there is some difficulty in choosing. They may be divided into —

Simple Manures

Simple Manures and Compound Manures.

The simple manures contain only one fertilising element, the compound manures more than one. Among compound manures there are some which are naturally compound, that is which contain more than one fertilising element in the matter of which they are made ; for example, guano, bones, etc., and others which are compounded mechanically, that is by mixing two or more maniures, such as fish guano and leather waste ; by mixing natural compound manures and simple manures (fish guano and sulphate of ammonia) ; by mixing simple manures, kainite, and basic slag, or by mixing simple or compound manures with neutral matter (sawdust or sand), for example.

Generally speaking, preference should be given to simple manures for the following reasons.

1st. The first and more important reason is that simple manures are generally, or one might say always, cheaper by the unit than compound manures. They can be obtained practically direct from their source, so that their purchase lies between the producer and the consumer only. There is no middle man, no handUng and no useless transport.

2nd. They are easily used ; only containing one fertUising element one can calculate exactly the quantity of each variety required. As much as is necessary of any determined element can be given independent of the quantities of other manures. With compound manures this is scarcely possible, because they will not contain the proportion of elements suitable to a given soil.

3rd. Different manures require to be used at different depths in the soil. For example, it is not good to plough or harrow in Chili nitrate, while slag or kainite generally require to be well incorporated with arable soil. Hence one can easily use simple manures at the depth which suits them best, whilst in using compound manures this is not possible. Being mixed, some will be too deep, and others not deep enough.

4th. Different manures need to be applied at different seasons. One would not use nitrate in November, because it would be irretrievably lost, though slag could very well be used on arable at this season without any such risk. Each manure has its corresponding time for application. With compound manures, in which of course all the elements are applied at once, sometimes one or more of them is not used at the time which suits it best.

5th. Simple manures used alone are not subject to the losses which arise as a result of certain mixtures in chemical manures, such as loss of ammonia [NH3].

6th. Being simple and supplied straight from the source, they are less subject to adulteration.

Compound manures, again, are generally too dear. The reason why is not difficult to understand. Their price ordinarily includes —

1. The cost to the producer of each of the simple manures of which the mixture is compounded.

2. The cost of transport from the producer to the manufacturer of the mixture.

3. Handling and cost of storage here.

Simple Manures

4. The cost of the making of the mixture.

5. Putting up into sacks and storing again.

6. Fresh cost of transport to the place where it is to be used.

7. General cost, trade charges, makers' profit ; and it is easy to understand that even with the most honest manufacturer, the price of the unit of fertilising matter will sensibly increase the cost and often not the value.

Besides, many compounds actually on the market enjoy an unmerited popularity, and fetch a price far beyond their real value simply as the effect of the law of supply and demand. Everybody knows them, everybody wants to have them. The output is limited, and the maker can easily demand a high price and still refuse orders. This shows that people buy by recommendation and habit, and not by knowledge of the subject. Manures ought always to be bought by the unit of fertilising material.

Many people still purchase by the ton, without even considering what that ton contains, or in any case without considering how much the units of fertilising material will come to. But it is not the ton of manure which is fertile, but the units of fertiUsing matter in it. When one pays good money one has a right to receive good manure ; and the purchaser should always compare the price of units of fertilising matter so as to buy that which under a similar form will cost the least.

The best way of ascertaining what one is buying is by analysing the manure, and to bring analysis into general use should be the work of an Agricultural Union. This society should occupy itself with buying various artificial manures for its members, itself controlling the value of the manures.

In the mean time each farmer could calculate for himself the price per unit that should be asked, and could have the analysis made for his guidance in a deal of any great importance.

Here is a means of calculating.

In the Guide to Experiments for 1915 for the County of Northumberland we find that the superphosphate employed contains soluble phosphoric acid equal to 26 per cent, phosphate of lime, and that it was worth £2 17s. per ton. Phosphoric acid, then, corresponds to 26 units of phosphate of lime. Therefore the unit per ton will come to £2 17s. -f- 26 = 2s. 2d. approx.

Now, taking this price of 2s. 2d. per unit to the ton as a standard price, and supposing a super content of soluble phosphoric acid equal to 40 per cent, phosphate of lime, one would pay 40 units x 2S. 2d. = £4 6s. 8^. to the ton, and would gain an advantage in using this, as we shall see when we come to consider the cost of transport. Chloride of potash [KCl] costs £g per ton, and contains about 50 per cent, potash (K2O), so that the unit of potash costs here 3s. jd. per ton. If we take kainite, supposing it contains, for example, 13 per cent, of K2O to replace the KCl, we should pay 3s. yd. X 13 = £2 7s. per ton, and we should pay even a little too much.

The same ought to be paid, for the unit of fertilising matter in compound manures as in simple. For each unit of fertilising matter, the standard price corresponding, should be calculated, and the buyer

The Richest Manures

should determine for himself the value of the manure in comparison with the merchant's price. These are problems in the solving of which the farmer ought to be very skilled, and their understanding would in itself be of great service to him annually.

We have spoken of the very bad habit of using manure by the hundredweight or ton. For the most part such manuring indicates nothing. Here is an example. There are basic slags which contain 21 to 25 per cent. Ph. Ac. ; there are others which contain 40 to 41 per cent, and even more. It is obviously impossible to make comparison between fields on which the first is employed and those where one has used the second. Supposing, for example, that we employ 18 to 28 ton units of Ph. Ac. per acre, or 4 ton units of Potash to the acre, etc. We have so many acres to manure, and we must look for a manure which will give us these quantities at the most advantageous price.

The Richest Manures.

On principle one would buy the richest manures — that is those containing the most units of fertiUsing matter to the same weight. When at the place of origin the price of the unit of the same manure is the same, the manure which costs most is the cheapest to buy. This is obvious, because a manure containing only 15 pejr cent, fertilising matter will cost in transport, sacks, time lost in spreading just as much as that which contains 30 per cent, fertilising matter, and in the end it is the units of fertilising matter which count.

These additional costs are spread in the first case over 15 units, and in the second, over 30. The difference is sometimes so great that it is often even better to take muriate of potash (KCl) in preference to kainite, though the unit of Potash costs decidedly more in the former than in the latter, because of the very important additional expenses ; but these in the kainite are based on 12 to 13 units, while in the KCl on 50 units of Potash [K2O].

The comparative richness of the manure to be employed must therefore always be considered, and the price of the imit ought to be calculated when distributed on the fields. In this way all the costs are included.

Among manures some are of rapid action, others slow. Preference ought to be given, as a rule, to the rapid, because they will repay outlay more quickly. Very often manure merchants advance arguments in favour of those of their wares of which the action will still be felt in the following year, or even for many succeeding years. But supposing — ^which is not always the case — that all the fertilising elements will be assimilated after a greater or less number of years, the argument is not worth anything. Each particle of manure can only be absorbed once by the plants, and it can only pay when it is absorbed. Therefore the more quickly it is absorbed the more quickly will it pay. To equalise the price of the unit it is a mistake to buy now a manure which will not repay the outlay in three years or more. Generally it is preferable to use manures of such action that they will reimburse their cost the same year that they

Assimilability

are applied, and to give each year the quantities of manure required.

Besides, in using manure of slow action, how many units will the plants find at their disposal during the first year and during each of the succeeding years ? There is no room in modern agriculture for all this waiting and all this uncertainty. Manures of very slow action ought rather to be regarded as improvers and not as manures, and then should be bought at a very low price.

Yet another manure is one having a more or less progressive action, finishing in a year or thereabouts. The action of these manures depends on their assimilability, which again depends on many factors. There are two especially, of very great importance, first their solubility, and second their fineness. The nature of the soil and the species of vegetation also play an influential part.

Assimilability.

The most important point about manures is their assimilability. A non-assimilable matter is not a manure, although it may contain nutritive elements. Certain mineral phosphates are only assimilable with difficulty, or not assimilable at all in ordinary soils, so that they often do not possess any fertilising value. This is why their introduction into more assimilable fertilising matter really constitutes an adulteration of the product. Other manures are more assimilable though not entirely so, and not immediately. These are the manures of more or less slow action. Others, again, are rapidly and immediately assimilable and these are the best

t9 manures. They are those which most rapidly repay outlay, and their employment is the most advisable.

I. Mineral Tricalcic Phosphates — Coarse and Inassimi-

LABLE.

A. While the crop is growing.

A poor crop.

B. After the crop.

It remains unchanged.

Assimilability is generally in proportion to the solubility.

Solubility.

Manures which are soluble in water are, as a rule, regarded as very assimilable. A good example is the Ph. Ac. in superphosphates.

Then come the manures soluble in weak acids, the chief of which is basic slag, soluble in 2 per cent, of alkaline citrate. These are justly regarded as soluble manures, although less so than the superphosphates ; while the phosphates soluble in strong acids are justly considered as only slightly assimilable.

Those particularly which are only soluble in strong acids have, however, different degrees of assimilability for the same chemical form. This

Solubility

difference may arise from the more or less violent way in which they have been formed, from the very

2. Phosphoric Acid in Basic Slag. Different Solubility, SAME Fineness.

During the crop.

Total phosphoric acid.

Poor crop.

Phosphoric acid soluble in weak acids.

Good crop.

• = Insoluble. O = Soluble. The general argument is that the total phosphoric acid will act next year — perhaps. The likelihood is that it will not — perhaps never.