Chapter 6. Unprocessed Residues

Summary

The value of animal manure varies considerably, depending on the feed and the age and productivity of the animal. Estimates are shown in tables 7. Manure Production - 10. Mineral Content & Feeding Capabiity Of Manure Relative To Nitrogen . These results should be corrected for losses of nutrients.

With nitrogen losses taken into account, most manures are reasonably balanced fertilizers.

Nitrogen losses in animal manure may be due to leaching, volatilization of ammonia, or denitrification of nitrates. Possible ways of contolling them are composting, rotting, and adding chemicals (ammonia losses only).

Typical application rates are about 2 tons/acre for poultry manure and in the range from 5 to 40 tons/acre for other manures.

The nutrient values of hay and straw are tabulated in tables 11. Nutrient Content Of Hay - 13. Comparison Of Cow Manure With Hay And Straw . Both are good sources of nutrients, and legume hay is comparable to manure in nutrient balance. The advantages and disadvantages of mulches, their contribution to humus, and their effect on nitrogen availability are discussed.

Other useful residues are leaves, paper, seaweed, and pond dredgings.

Animal Manure

Data for the tables in this section are from [21], [19], [90], [26], [33], [2], [69], [43], [44], [47], [70], [81], [85], [61], [79], [92], [88], [94], [55].

The Value of Manure

Animal manure is the oldest known fertilizer, recognized for its benefit to the soil and to plant growth. How one thing can be both a disgusting mass of putrefaction and an inestimable treasure to mankind is surely one of the miracles of our world.

A farmer is faced with problems on both sides of this miracle. On the one hand is the necessity of getting rid of a socially undesireable pile of waste; on the other the task of conserving a product whose value represents most of the expense of animal feed.

Tables 7. Manure Production - 10. Mineral Content & Feeding Capabiity Of Manure Relative To Nitrogen illustrate the dilemma. Table 7. Manure Production shows the total manure production per 1000 lbs live weight; also shown are estimates of the daily production from animals of average size. Table 8. Density And Porosity of Manure permits an approximate weight to volume conversion by listing the density and air content of different manures. Table 9. Nutrient Content of Manure indicates the range and average value of the major nutrients in manure. Table 10. Mineral Content & Feeding Capabiity Of Manure Relative To Nitrogen shows the value of the major minerals relative to nitrogen.

Several factors determine the nutrient value of manure. In general, the richer the feed, the more that passes through the animal and the richer the manure. Feed grain, which is richer than hay, produces a richer manure.

The value of manure is inversely related to the weight gain and productivity of the animal. Young animals produce poorer manure than mature animals. Milk-producers generate poorer manure than non-producers. Work animals primarily need only carbohydrates, and most of the nutrients in the feed pass through them.

Animals which do not gain weight or produce a product require nutrients only to replace tissue; the old, dead tissue is sloughed off, and so the nutrient value of their manure is similar to the value of the feed.

The proportionate production and nutrient content of the solid and liquid portion depend upon the feed. The solid part contains live and dead organisms plus components of the feed which are resistant to absorption by the animal. Waste products generated during metabolism pass through the kidneys and are voided in the urine.

Consequently, a high roughage diet will produce a greater proportion of feces, while a more succulent or high nitrogen feed will result in a higher urine content and a higher quantity of nitrogen in the urine. The comparative differences in the nutrient value of the feces and urine are important; nitrogen is more stable in the solid part - which is already partly composted - than in the liquid.

With all the factors that influence the nutrient content of manure, it is of little surprise that tests show such variability. The variability of the distribution of nitrogen and potassium between the solids and liquid of manure is not shown in table 9. Nutrient Content of Manure , because little data is available and the table is already crowded, but it should be high.

Anyone using a dependable, constant source of manure should have it tested at the time of application, rather than relying on uncertain figures. Animal owners should, in addition, obtain a test when the manure is voided, in order to monitor the losses during storage.

Despite the variations shown in the tables, they do tend to confirm some of the generalizations often made to characterize manures. For example, cage layer manure (or hen manure) is very strong and also wet and difficult to handle. Hen feed is the most concentrated of animal feeds, and the manure is unusually rich, particularly in nitrogen, phosphorus and calcium, the last owing to the lime usually added to the feed.

In contrast, broiler manure is drier, because it contains litter to absorb moisture. The nutrient content of broiler manure is the most difficult to predict, probably because of differences in the amount of free run the birds are allowed and in the frequency with which the manure is collected and piled.

The other manures are better balanced than poultry manure, but their value is difficult to predict without information on the diet and purpose of the animals. The least variable appears to be horse manure, perhaps an indication that the diet of horses is more predictable. On the basis of its reputation and also the average values in table 9. Nutrient Content of Manure , sheep manure is the strongest of the nonpoultry manures, and indeed it is often sold dried and bagged.

Moisture content is an important characteristic. Horse manure is coarse, light and dry; it is little more than half as dense as other manures. Having a high air content, it heats up very fast. On the other hand, pig and cow manures are wet and cold, and they rot more easily and with less nitrogen loss than horse manure. Sheep manure lies between these extremes; it is moderately coarse and dry and is hotter than cow manure but not as much as horse manure.

The value of manure as a balanced product can be assessed with the help of table 10. Mineral Content & Feeding Capabiity Of Manure Relative To Nitrogen , which lists the average ratio of phosphorus, potassium and sulfur to nitrogen. The table shows that cow manure has about 1/3 as much phosphate as nitrogen and almost as much potash as nitrogen, assuming all the nutrients are conserved.

By comparing such equivalents to the corresponding ratios for crop requirements shown in table 6. Mineral Requirements Relative To Nitrogen , we can determine how well balanced manure is as a fertilizer. This is done in table 10. Mineral Content & Feeding Capabiity Of Manure Relative To Nitrogen , which lists the percent deficits (surpluses are underlined). It shows that cow, horse and sheep manure are low in phosphorus and sulfur, and all manures are low in potassium. For example, if enough cow manure is used to supply all the nitrogen, it will be shy of phosphorus by about 30% for growing hay and grains and about 40% for vegetables.

We are, of course, using a great many averages, and the ability of manure to provide a balanced ration will vary considerably in individual cases. Also, we might be able to minimize losses of most minerals, but it is unrealistic to assume that we can conserve all of the nitrogen. Losses of at least 30% are the rule more than the exception. The second part of table 10. Mineral Content & Feeding Capabiity Of Manure Relative To Nitrogen shows the results of assuming a 50% loss of nitrogen. Then the balance of nutrients is very good, and manure is as close to a complete and balanced fertilizer as one would want. The only exception is poultry manure, which is still significantly short in potassium and overly rich in phosphorus1

Manure Losses

Just because manure has to lose nitrogen in order to be balanced does not mean that we should encourage losses. In the first place we may not need a balanced fertilizer; most soils are lower in nitrogen than in the other nutrients. Secondly, losses will take place without our help. So we need to do all we can to minimize them.

The non-nitrogenous minerals in manure can be conserved by protecting the manure from rain and snow and taking care that the urine does not leach out. With little or no leaching losses, nitrogen will suffer the major loss.

Initially, the major cause of nitrogen loss is volatilization of ammonia. Urine is easily attacked by soil organisms, with the ultimate formation of alkaline ammonium hydroxide. The pH of the manure rises rapidly after it leaves the animal, owing partly to the ammonium hydroxide but primarily to the existence of carbonates in the manure, the result of biological activity while still in the animal's gut.

The instability of ammonium hydroxide under these conditions causes the formation of ammonia, which is lost as a gas. Normally, the ammonia is attacked by bacteria and converted to nitrate by the process of nitrification, but these particular bacteria function poorly if the pH is too high. Thus loss of ammonia can continue for a long time.

Once the pH is below an excessive level (about pH 8), the production of nitrates from ammonia is high and introduces enough acidity to control the pH. This stabilizes the manure, at least so far as ammonia losses are concerned, and then all we need worry about is the loss of nitrates. Even when leaching is controlled, nitrogen losses can occur from denitrification of nitrates 2. Denitrification is difficult to control in the soil and even more so in a manure pile.

The solid part of manure has already been partly decomposed in the animal, and nitrogen in the solids is stable compared to the nitrogen in the urine. The rapid formation of nitrates from the ammonium in the urine is probably the source of most of the nitrogen lost by leaching and denitrification. When urine is collected with the solid portion, nitrogen losses on the order of 50-60% are typical.

Some farmers, particularly in Europe, collect the urine separately and keep it tightly enclosed, with a layer of oil over the surface. The oil cover minimizes losses of ammonia, and denitrification is reduced as well, since the lack of oxygen keeps the ammonium from being oxidized into nitrate3.

Is the trouble required to minimize nitrogen losses worthwhile? It is certainly arguable whether nitrogen is the most important component of manure. Much of the phosphorus is available, and the trace elements in manure are inconvenient to supply in inorganic form. Perhaps most important are organic substances in manure - various enzymes, vitamins and hormones - whose benefits individually are largely unknown, but which together give manure an aura otherwise reserved for gold. Indeed some people prize manure most highly for its non-nitrogenous value, and they plant clover to supply the nitrogen.

On the other hand, many farmers rely on manure for much if not all of the nitrogen they need, and minimizing losses for them is important.

One way to reduce losses, though not often practical, is to spread the manure immediately as it becomes availabile. If manure is so fresh that no substantial amount of ammonia has formed, and if it is spread thinly on a warm, dry day, it need not be tilled in quickly, because drying will delay the breakdown of the urea.

If manure is not entirely fresh it should be turned under or spread before a rain, because drying will hasten the volatilization of ammonia which will have already formed. Some crops, however, do not respond well to fresh manure, and the flavor of others is tainted. Manure should not be spread on frozen ground or when runoff losses are likely to be high.

One possible way to store manure is to compost it, by mixing it with carbonaceous material and enough air and water. According to theory, carbonaceous residues intercept and stabilize the nitrogen. In practice, nitrogen is often lost from compost for three reasons:

Another option for storing manure is to rot it by keeping it in an anaerobic state. In the absence of oxygen, organic acids produced by fermentation help to keep the pH down. Furthermore, with the lack of air, the ammonia is not transformed to nitrate, and denitrification cannot take place. To make a good pile, the manure should be slightly moist and well packed; traditionally it is trampled by the animals. If allowed to dry out, air will seep in and the manure will lose ammonia. If too moist, it will putrefy and emit offensive odors.

The problems of rotting are similar to those of composting, but the tolerances are not so narrow. Even if the surface dries out, the interior is usually moist enough to maintain a state of rotting. If the manure is too wet, the addition of soil will absorb excess moisture.

A third way to reduce losses of nitrogen is to add material that will absorb the ammonia directly. Bedding is one possibility, but bedding is usually chosen for economy and used only in sufficient quantity to absorb enough moisture so that the animals are clean and comfortable. The most common materials, wood chips and straw, are poor at absorbing ammonia. The best are peat moss and soil, with as much humus as possible; even then a large amount is necessary.

An experiment in France showed that about half as much soil as cow manure, on a volume basis, is required for effective absorption of ammonia, and about 1-1/4 times as much peat as cow manure. Most northeastern American soils contain more humus than French soils, so perhaps less would be required, but one would have to experiment to find out.

Adding soil with manure to a compost pile may be an effective way to reduce nitrogen losses.

A fourth way possible for those who have the animals that produce manure is to separate the urine from the solids and treat it separately, as already noted. Decomposition of urine is the main source of excess ammonia.

Yet another way to reduce nitrogen losses is to add chemicals to stabilize the ammonia by neutralizing the rise in pH. Pure sulfur, for example, is oxidized by sulfur-loving bacteria to sulfuric acid. Or sulfuric acid itself has been used on occasion. Other chemicals, such as gypsum, ferrous sulfate, and superphosphate (which contains gypsum) have also been tried with mixed results. Any neutralizing effect of gypsum or ferrous sulfate is due to the calcium in gypsum or the iron in ferrous sulfate; these precipitate the carbonate associated with ammonium carbonate.

One problem with using chemicals to precipitate carbonates is that eventually the precipitates redissolve, driving the pH back up again. But the hope is that by then the ammonia will have been stabilized. In this respect, ferrous sulfate is better than gypsum, because the precipitate of iron carbonate takes longer to redissolve.

Another problem, however, is that enough chemicals must be added to also neutralize all the carbonates in the manure, not just those associated with ammonium. And a third problem is that no one has investigated the effects of these chemicals on the availability of other nutrients. The iron in ferrous sulfate, for example, is likely to lock up phosphorus and manganese.

There is a small amount of evidence that gypsum improves biological activity in some unexplained way, and this may hasten the stabilization of ammonia. Experiments with gypsum, however, have had variable results, and quantities varying from a few percent, on a weight basis, to over 100% (for poultry manure) have been recommended. Experimentation is still being carried out with all these chemicals, but so far their advantages are uncertain.

Another proposed claim for stabilizing nitrogen is the use of rock phosphate. If it is successful, however, the reason is obscure. Rock phosphate has a slow but definite liming capability, which is the opposite to what one would want to prevent a rise in pH. In addition rock phosphate is extremely insoluble at the pH level to which manure rises. Perhaps in some unknown way rock phosphate improves biological activity; or the clay in colloidal rock phosphate may be able to adsorb ammonia; or it may be able to adsorb gases from putrefaction, leading one to believe that ammonia is being conserved.

Even when chemical additives do work, they only limit ammonia losses and have no effect on denitrification. Loss of ammonia occurs only initially, while the pH is still high; denitrification is a threat as soon as nitrates begin accumulating.

Of the three alternatives - composting, rotting, and the use of chemicals - rotting is probably the easiest and may be the most satisfactory if the conservation of nitrogen is the primary objective. However cage layer manure is difficult to rot successfully. It tends to putrefy instead, giving off disagreeable odors. It is probably best composted or spread directly.

Cold composting with added soil may be a reasonable alternative.

Manure Application Rates

Although desireable, it is not always practical to test manure, and so guidelines are necessary. Recommended application rates are usually based upon the contribution of nitrogen.

We can make an approximate estimate of the amount of nitrogen added by manure as follows: According to table 9. Nutrient Content of Manure , fresh cow manure with urine can be expected to contain about 11 lbs of nitrogen/ton. About half of that nitrogen should be available the first year. With losses taken into account, the actual amount available should be about 3-4 lbs nitrogen/ton of manure.

At the opposite extreme, cage layer manure might contain about 30 lbs of nitrogen/ton. The nitrogen is much less stable in poultry than in cow manure, and perhaps about 25 lbs should be available the first year. After losses, the amount of nitrogen remaining in the soil might be half this amount, or about 12 lbs of nitrogen/ton, 3-4 times that of cow manure.

Usual rates of application of cow manure are 5-40 tons/acre. For corn or hay, 20-30 tons are often spread, applied to corn before planting or spread onto hayfields in three applications. Vegetables would benefit from 5-20 tons/acre, and small grains from 0-8 tons/acre (depending on the chances of lodging), applied before seeding. These rates should be decreased if manure is spread every year4

Horse manure can be applied at similar rates. However, sheep and pig manure usually have a higher nitrogen content, and less should be used. Rotted manure can be used at a lower rate also.

The nutrients from rotted manure are more available than from fresh manure, owing to the additional decomposition. A customary practice is to use rotted manure on fast-growing crops and fresh manure on slower ones. Fresh manure has adverse effects on root crops, especially carrots, which tend to produce forked roots. Rotted manure is good for improving nutrient and water retention of sandy soils; the coarseness of fresh manure loosens up heavy soils.

Poultry manure is much more concentrated than other manures, and its nitrogen is available more quickly. Pollution from poultry manure is a greater threat to groundwater supplies than other manures. Application rates of 2 tons/A are often satisfactory. Rates should not exceed 5 tons/acre without monitoring groundwater purity.

A reasonable comparison among manures is that one ton of poultry manure is equivalent to two tons of pig manure and four tons of cow manure, all at a semi-dry state (about 25% moisture) [18].

Hay And Straw

Hay is the air-dried cuttings of a green field crop, and straw is the cuttings taken with the grain. If the hayfield is managed without herbicides, it often sustains many varieties of plants, maturing at different times. As a result, hay usually contains weed seeds. Seed-free straw is easier to obtain. Hay, however, has a better balance of nutrients.

Table 11. Nutrient Content Of Hay shows the nutrient content of various varieties of hay and table 12. Nutrient Content Of Straw of straw [19], [50], [70], [71], [72], [85], [1], [79]. Table 13. Comparison Of Cow Manure With Hay And Straw compares the value of hay and straw with cow manure.

If legume hay and manure are supplied in such quantities that the nitrogen content is the same, then table 13. Comparison Of Cow Manure With Hay And Straw shows that the hay supplies approximately the same amount of major nutrients as manure but less of the trace elements. The outstanding exception is boron, but that is because the boron data for legumes came from a single test of alfalfa and is unlikely to be representative of all legumes, maybe not even of alfalfa5.

The results are similar with nonlegume hay and straw. They have, however, relatively more of the major elements, because they contain much less nitrogen.

Table 13. Comparison Of Cow Manure With Hay And Straw indicates that, as a fertilizer, legume hay is a reasonable alternative to manure, and nonlegume hay might be also if it were supplemented with nitrogen. Hay, however, has disadvantages. Bulkier than manure, it is more difficult to spread over a large area; it does not have the decomposition products of manure; and it may have more weed seeds.

Hay does have advantages over manure. It has a greater energy content and will contribute more to total biological activity of the soil; possibly its decomposition will produce similar organic byproducts already present in manure. Because nitrogen is more stable in hay than in animal urine, its loss is less likely.

Straw also has a respectable amount of nutrients, although it has lost most of its nitrogen and phosphorus to the harvested grain.

Hay and straw are excellent mulches. Hay adds more nutrients, but straw usually has fewer weed seeds. Weeds, however, are not as much of a problem in mulch as they are in residues turned into the soil. Weeds which become a nuisance grow from the mulch and can be easily pulled out, and those that come up the following year can be smothered by another layer of mulch.

Mulches provide several non-nutrient benefits to the soil. They establish an excellent physical environment for soil organisms, and they are food for organisms which prey on pathogens. Varieties of fungi which consume nematodes are stimulated by mulches.

Mulches, however, have disadvantages. Some of the decay products may be toxic to seeds and new seedlings; to avoid this, mulch should be be applied only after a plant is well established.

Mulches also keep the ground cool and render it unsuitable for warm-weather crops. The cool and damp environment may encourage insect pests. It may induce plant rot if the mulch is packed too closely around the base of the plants.

One should be cautious about purchasing bales of hay or straw or any mulch material that has been stored for a long time. If the material was stored under anaerobic conditions while moist it may have turned sour; if so, it could damage growing crops. Sour residues smell sour, with an odor similar to vinegar, ammonia, sulfur or silage. Any mulch, especially hay but sometimes even packaged bark chips, will decompose. So smell it to be sure. Chances are that if hay or straw is dried properly, it will last a reasonable time, but even so, if it is to be stored, one suggestion is to compost it [12].

The immediate nutrient content of a mulch is difficult to estimate. Soluble substances will leach into the soil, including potassium and water-soluble organic substances. The portion of the mulch in contact with the soil will break down, and, slowly, the rest of the mulch will follow.

People who mulch continuously can assume a carryover from previous years and that almost all the nutrients are available, except for leaching and nitrogen losses. Nitrogen losses other than through leaching should be small, because the nitrogen tends to become available slowly enough that excesses of soluble nitrogen do not accumulate.

It may be interesting to calculate the fertilizing value of a mulch, assuming that all nutrients eventually move into the soil. As an example we could consider a mulch made by tearing apart bales of hay into one inch layers and placing them evenly on the ground. A bale of hay or straw is about 14 by 20 by 32 inches and may weigh about 40 lbs. A bale divided into one-inch layers can cover about 62 square feet of soil, and about 700 bales, weighing about 14 tons, would be required to cover an acre.

If each bale is made up of a nonlegume hay of average nutrient value as characterized in table 11. Nutrient Content Of Hay , the hay would contain about 350 lbs of nitrogen, 150 lbs of phosphate and 530 lbs of potash. So much nitrogen would appear to produce an excess, but table 11. Nutrient Content Of Hay shows that such hay will have a C/N ratio of about 32. With this ratio, 11,000 lbs of carbon accompanies the nitrogen. Most of the nitrogen will be tied up by soil organisms attacking the carbon, although after a period of decomposition and oxidation of carbon, some will become available. Some of the phosphorus and potassium will also become absorbed into the soil and be made relatively unavailable, but annual applications of such a mulch is bound to result in a large accumulation of available nutrients.

To produce 14 tons of hay, one might need about 3 acres of orchardgrass, and probably more of timothy. On this assumption, mulching a garden with one-inch layers of baled hay requires a hayfield about 3-5 times the size of the garden.

Lawn clippings are similar to a non-legume hay. They are a good soil activator and fertilizer, even though not enough may be available for a mulch. One problem is that they tend to compact and are best used with a bulking agent, such as a small amount of hay, straw or other residues.

Other Local Residues

Leaves

Leaves are often easily available, and no doubt they are a good source of nutrients. Their complete fertilizer value, however, can only be inferred, because only the analyses of their macronutrients is available in the literature. The average NPK content of deciduous leaves is about 0.8% nitrogen, 0.15% phosphate and 0.15 - 0.5% potash (0.15% in evergreen needles, 0.5% in deciduous leaves).

The most likely fertilizer value of leaves, however, is in their trace elements and sulfur content. Before a leaf dies and drops from the tree, most of the macronutrients (probably except sulfur) have already drifted back into twigs and branches. Micronutrients, however, are immobile and remain in the leaf. Consequently, leaves can be expected to contain appreciable quantities at least of copper, iron, manganese, and perhaps other trace elements.

Leaves have to be managed carefully in order to realize their maximum benefit. If collected together in a mass, they form a compact, impenetrable mat when wet. To avoid this, they should be either shredded or mixed with coarse materials. Either way they can be spread directly, turned into the soil, or composted.

Leaves can also be rotted alone, to form leaf mold, but no advantage of rotting over composting seems to exist, and rotting can take several years unless the leaves are well shredded. Evergreen needles decompose very slowly and are probably best used as a protective and decorative mulch for ornamentals and trees.

Paper

Paper is useful as a mulch to suppress weeds. It also has value for its cellulose but has little or no nutrient value for plants. It may be used in a new strawberry bed or, for that matter, any garden. To keep the paper from being blown away, staple sheets end to end to form a long roll which, when unrolled, may be held down by stones, branches or hay. Punch holes for planting.

Alternatively, shred the paper and use it as any other mulch.

One potential problem is the possible hazard of heavy metals in the printing inks. According to the USDA, the ink used in newspapers is free of lead and therefore safe to use as a mulch. Also, the Minnesota Pollution Control Agency [9] has found that, if mixed paper is used (such as paper from different magazines), any toxic materials are present in such negligible quantities that no danger exists. Unmixed paper may be satisfactory also, but one would need more information.

Seaweed

Seaweed is a good soil amendment but is usually a practical residue only for gardens of small to moderate size. The nutrient content of seaweed varies with the species and the time of year when gathered, but typical values, on a dry weight basis, are 1.2 - 5% nitrogen, 0.2 - 1.3% phosphate, 2.8 - 10% potash, about 0.02% boron, 0.001% copper, 0.05% iron, 0.05% manganese, 0.002% molybdenum, 0.004% zinc, and numerous additional elements at lower concentrations.

Suppose that a person is able to haul 100 lbs of air-dried seaweed (perhaps five times this amount of fresh seaweed) to a 3000 sq ft garden. According to the above figures, this amount will supply the equivalent of 17 - 70 lbs of nitrogen/acre, 3-18 lbs phosphate/acre, 40 - 140 lbs potash/acre, and about 0.3 lbs boron, 0.01 lbs copper, 0.7 lbs iron and manganese, 0.02 lbs molybdenum, and 0.05 lbs zinc, all per acre.

A comparison of these figures to those in tables 3. Estimated Fertilizer Requirements - Field Crops - 5. Average Nutrient Requirements For Vegetables shows that the quantities of NPK supplied by this amount of seaweed are significant, since the phosphorus, potassium and much of the nitrogen are readily available. Boron seems to have a reasonable presence, and possibly molybdenum, but the quantities of the other trace elements do not seem to be significant. The micronutrients furnished by seaweed are of questionable value despite their impressive diversity.

Where crops such as potatoes are grown directly in seaweed on top of the ground, the trace elements may be more influential.

Perhaps the most important merit of seaweed is its content of assimilable organic materials, in particular the growth hormones. In this respect seaweed is rivalled only by animal manure and compost [78]. On the other hand, research in British Columbia with kelp [11] concludes that even the growth hormones have questionable value. Possibly seaweed is worthwhile only to people living near the coast, where it can be foraged rather than purchased.

The salts in seaweed, which need not be washed off for application to most soils or for composting, may provide additional nutrients, particularly magnesium.

Pond Dredgings

The use of pond dredgings as a fertilizer is practically unknown in the U.S. but is popular in China. Fed by a stream, the pond collects the silt carried by the flowing water and becomes a reservoir of nutrients. The pond may be partitioned into two or more sections, each of which is independently drainable. Then one section can be drained each year and the dredgings transferred to the soil6


1 A recently obtained 10-year average indicated that, taking losses into account, the phosphate content is about half the nitrogen content of cow manure, 3/4 the nitrogen content of pig manure, and equal to the nitrogen content of poultry manure. Potash is 1-1/4 times the nitrogen content of cow manure, half the nitrogen content of pig manure, and 1/3 the nitrogen content of poultry manure. See [18].    [return to text]

2 see chapter 10. Nitrogen - losses     [return to text]

3 One innovation which was developed by a farmer in Quebec for stabilizing animal urine is to use molasses as a starter in an aerated tank of urine (anyone interested in further information should contact Joe Smillie, RR #3 Erle, Weedon, PQ-C JOB 3JO, Canada)    [return to text]

4 Summarized from [92].    [return to text]

5 Alfalfa has a high boron requirement, but this does not necessarily mean that it is a good accumulator: it may simply be inefficient at extracting boron from the soil.    [return to text]

6 Scott and Helen Nearing built such a pond at their home in Maine.    [return to text]

© 2013 Robert Parnes

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