Poultry manure as a concentrated organic fertilizer for crops

Poultry manure is a product excreted from a bird's organism as a mixture of urine and feces, grey-green in color, with a clumpy-porous structure. Like manure, poultry manure contains all the macro- and mesoelements necessary for plants, but in significantly higher quantities. This is explained by the fact that poultry is fed more concentrated feed (Table 110; Wildflush I.R., Kukresh S.P., Tsyganov A.R. et al., 2000).

Table 110 – Water and nutrient content in poultry manure, % of raw mass Bird species H2O N P2O5 K2O CaO MgO SO4

 Chickens 56 2.2 1.8 1.1 2.4 0.7 0.4 Ducks 60 0.8 1.5 0.5 1.7 0.3 0.3 Geese 80 0.6 0.5 0.9 0.6 0.3 1.1

The manure is rich in microelements: 100 g of dry matter contains 15–38 mg of manganese, 12–39 of zinc, 1–1.3 of cobalt, 0.5 of copper, and 367–900 mg of iron. Microelements are released as organic matter decomposes, so they are available to plants for a longer time than the microelements in mineral additives, which act temporarily until they undergo chemical binding into hard-to-access forms. The manure contains 15–40% ash, 2.8–4.5% fat, 14–25% fiber, and 46–48% nitrogen-free extractive substances. The manure of geese and ducks, which feed on more watery food, contains fewer nutrients and more water than chicken manure. The quantity of nutrients in poultry manure can fluctuate significantly depending on the method of poultry keeping.

In poultry farming, four methods of poultry keeping are distinguished: free-range, cage, aviary, and combined.

Free-range keeping of chickens or free-range pasture keeping of geese, turkeys, and ducks is used on breeding and commercial farms, as well as in the parent stock departments of poultry factories.

Cage keeping is characteristic mainly for large specialized poultry factories located near cities and industrial centers.

Aviary keeping. The livestock is kept outdoors in an area fenced with netting, or in light structures with a canopy and open facade. The floor under the canopy is made of metal mesh. Manure is removed 1–3 times a year.

The combined method of keeping is used at poultry factories and large commercial farms when rearing young birds.

Free-range and aviary poultry keeping are considered floor keeping. It can be litter-based on non-replaceable deep litter and litter-free on mesh or slatted floors. This results in litter-based (solid, with a humidity of up to 70%) or litter-free (semi-liquid, with a humidity of 70–90%) manure. With cage keeping, litter-free liquid manure is formed (with a humidity of more than 90%).

Keeping poultry on litter has both positive and negative sides. Peat, straw, sunflower hulls, crushed sunflower stems, and tree leaves are most often used for litter. The humidity of peat should not exceed 45–50%, and for other types of litter – 25–30%. Litter, especially from peat, lowers humidity in poultry houses and purifies the air by absorbing liquid and gases. The use of peat litter prevents poultry from diseases such as coccidiosis and colds, kills parasites, promotes efficient feed utilization, and increases poultry productivity. In addition, litter facilitates the preservation of nutrients in the manure, preventing their losses. A negative side of litter-based poultry keeping is the low stocking density per 1 m2 of the facility. The frequency of litter replacement per year for chickens is 1 time, and for other types of poultry – after each batch. Daily, one chicken requires 100–150 g of litter, and a duck, goose, or turkey requires 200–250 g.

The output of manure depends on the species and age of the bird (Table 111; Novikov M.N., Khokhlov V.I., Ryabkov V.V., 1989).

Table 111 – Manure output from 1000 head of poultry, kg/day. Bird species Humid- Age of bird, days ity of manure, % 1 2 3 4 5 6 7 8 9 22 >22

 Egg-laying chickens and chicks 75 4 14 24 39 61 82 97 114 128 175 189 Meat chickens and chicks 75 11 46 92 130 140 170 200 230 250 280 300 Broilers 76 10 45 90 125 144 182 240 250 – – – Turkeys (light cross) 76 30 98 124 182 224 260 280 310 320 350 378 Turkeys (medium and heavy cross) 75 28 82 125 175 200 225 280 310 361 390 420 Geese and goslings 83 50 140 280 330 360 390 440 450 480 490 490 Ducks and ducklings 83 30 60 90 120 170 200 210 220 230 250 250

The average annual rate of manure output, taking into account drying to 65–70%, is 6.2 kg per adult bird and 4.2 kg per young bird.

With cage poultry keeping, water from drinkers may get into the manure, as well as water resulting from artificial dilution to facilitate its removal. The output of manure when water is added to it can be determined by the following formula:

100  V2

100  V1 where: MR – mass of manure diluted with water, t;

Mn – mass of manure of natural humidity, t;

V2 – natural humidity, %;

V1 – actual (increased) humidity of the manure, %.

If we consider that the average humidity of diluted manure is 85%, and Mn = 1 t, then Mr = 1·(85–70):(100–70) = 1·(15:30) = 0.5 t. Consequently, when diluted with water by 15%, the mass of the manure increases by 50%.

How to properly store and stack litter manure

Poultry manure is a highly concentrated organic fertilizer that requires strict adherence to storage rules. If litter manure is left in ordinary heaps, it begins to heat up intensely. This leads to massive losses of nitrogen, which can account for 30 to 60% of its initial content in just one and a half to two months. The use of deep litter in floor-based poultry housing helps to reliably preserve nutrients, reduce the stickiness of the fertilizer, and increase the productivity of the hens.

For proper storage, litter manure is packed tightly into windrows. These are formed to be slightly smaller than those used for manure, while strictly observing technical dimensions. The finished windrow is covered with a 10–15 cm layer of soil containing no more than 25% humus. If the humidity of the raw material drops below 60%, it must be pre-moistened.

• Windrow base width — 4–5 m
• Windrow height — 1.5–2.0 m
• Thickness of soil cover — 10–15 cm
• Critical heating temperature — 55–60 °C
• Nitrogen losses in open heaps — 30–60%

When forming a windrow, mineral components are necessarily added to fix nitrogen. One can choose to apply 5–7% superphosphate, 10–15% phosphorite meal, or 5% phosphogypsum based on the mass of the raw material. For long-term storage, it is advisable to increase the rate of mineral application by 10–15%. To preserve nitrates during long-term storage and prevent the manure from freezing, 0.5–2.0% potassium chloride salts are added to the windrow. To prevent the decomposition of urea, manganese sulfate or waste from the manganese mining industry is used.

Composting technology for manure without litter

Up to 80% of all manure at poultry farms is obtained without litter, with a moisture content of 75 to 90% or more. To understand the scale: an enterprise with 500 thousand laying hens or 6 million broilers produces up to 125 tons of manure and 150 cubic meters of wastewater daily. The most effective way to utilize this volume is to prepare composts with peat, straw, sawdust, bark, or lignin. Moisture-absorbing materials preserve ammonia and liquid waste, and under the influence of manure, their own nitrogen, which is otherwise difficult to access, converts into a form available to crops.

The technology for producing compost includes three main stages, which must be carried out in strict sequence. Operations are organized on open sites, in specialized mechanized storage facilities, or in stationary workshops. Proper adherence to the protocol guarantees uniform maturation of the mixture and eliminates nitrogen losses.

1. Delivery of manure without litter, moisture-absorbing filler, and mineral additives to the mixing area.
2. Thorough mixing of components and forming the mixture into windrows.
3. Keeping the formed windrows on the composting site with periodic aeration.

The mass of moisture-absorbing filler (M, t) per one ton of manure is calculated using the formula: M = (W_m - W_s) / (W_s - W_f), where W_m, W_f, W_s are the moisture content of the manure, peat (or straw), and the mixture, respectively. The daily requirement of the farm for the filler (M_d, t) is determined by the formula: M_d = M × D_m, where D_m is the daily manure output in tons. These calculations help to accurately plan logistics and stocks of components before starting work.

Finished compost should have a fine-crumbly loose structure with a particle size of no more than 120 mm and a moisture content in the range of 60–70%. A neutral or slightly alkaline pH is required, and the organic matter content should be at least 75% with a C:N ratio = 20:30. Readily available forms of nutrients should account for at least 50% of their total volume. There should be no smell of manure, no viable weed seeds, no helminth eggs or larvae, and the share of non-toxic foreign inclusions is limited to 1%.

Properties and nutritional value of dry manure

Thermal drying at a temperature of +600–800 °C is the most effective way to preserve nutrients in manure from cage-based poultry housing. This process reduces the mass of the raw material by 3–4 times and completely destroys pathogenic microflora, helminth eggs, and weed seeds. The result is a loose product with a moisture content of 12–14%, which can be applied to the soil using almost all types of mineral fertilizer spreaders. From 1 ton of raw manure with 65–70% moisture, about 300–350 kg of dry fertilizer is obtained.

• Organic matter — up to 80%
• Nitrogen (N) content — 4–6%
• Phosphorus (P2O5) content — 4–5%
• Potassium (K2O) content — 2.0–2.5%
• Calcium (CaO) content — 5–6%
• Storage humidity — no more than 25%

Dried manure does not have a sharp, unpleasant odor and can be packaged in bags. If humidity requirements are met, the fertilizer can be stored for up to six months with almost no loss in nutritional value: in 6 months, only 2–8% of nitrogen and 4–11% of organic matter are lost. During the drum drying process, the manure is granulated — the fraction ranging from 1 to 5 mm makes up to 75% by weight, and the amount of dust (less than 1 mm) does not exceed 15%. The pH of the fertilizer is close to neutral or slightly alkaline, ranging from 6.8 to 7.8.

In terms of its effect on the harvest, dried manure is similar to mineral fertilizers, but it surpasses them in the duration of its residual effect. Nitrogen in it is present primarily as proteins and their degradation products, and the share of non-protein nitrogen does not exceed 10–12% of the total. Phosphorus is mainly in the form of organic compounds. It is weakly bound by the soil complex into poorly available iron, aluminum, or calcium phosphates and is gradually assimilated by plants as mineralization occurs. Thanks to this, phosphorus from manure is assimilated better than from mineral fertilizers.

Application rules and field distribution schemes

Since dried manure is primarily a nitrogen-phosphorus fertilizer, additional potassium is required for balanced plant nutrition. This is especially important when growing potassium-loving crops on light sandy and sandy loam soils. The fertilizer is effective both during base application (primarily for row crops) and for top dressing.

When working with manure, two factors are critical: uniformity of distribution across the field and immediate incorporation into the soil. Uneven spreading creates areas with toxic concentrations of nutrients, and delays in incorporation lead to the loss of ammonia nitrogen, which quickly volatilizes from an open surface.

Application equipment is selected based on the planned application rate:

• At a rate of 2–5 t/ha, dried manure is distributed using RUM-3 type machines.
• For higher rates, standard manure spreaders are used.

Application rates are calculated individually, based on the crop's need for nitrogen and its content in the fertilizer. On poorly cultivated soils, the dosage is adjusted.

Based on field trial results, one of the following schemes for the combined use of manure and mineral fertilizers is recommended:

• Simultaneous incorporation of manure and mineral fertilizers in the spring for spring crops or in the summer for winter crops.
• Application of manure and phosphorus-potassium fertilizers in the autumn before autumn ploughing, and nitrogen fertilizers in the spring before cultivation (for row crops).
• Application of manure in the autumn before ploughing, and mineral fertilizers in the spring before cultivating the ploughed land.
• Application of manure before ploughing, and mineral fertilizers locally when ridging or planting potatoes in ridges.
• Application of manure for a fallow-occupying forage or green manure crop, and mineral fertilizers for the subsequent winter cereals.

When calculating the application rate, it is necessary to consider the soil type, the crop being grown, and the form of the fertilizer itself. Below are the estimated application rates for various types of manure and composts based on it.

• Dried manure rate for winter cereals — 3–4 t/ha
• Litter-based manure rate for potatoes — 20–25 t/ha
• Liquid manure dose for corn on chernozem — 60–80 t/ha
• Compost rate for sugar beet — 20–25 t/ha

Gas toxicity and safety when handling manure

Poultry manure is characterized by high biological activity. During the process of enzymatic and microbial decomposition of its organic matter, toxic gases are released: hydrogen sulfide, carbon dioxide, ammonia, methane, and carbon monoxide. The accumulation of this gas mixture in enclosed poultry houses and manure storage facilities poses a direct threat to human life.

When inhaling this mixture, a person experiences olfactory paralysis, which causes them to quickly stop sensing the danger. This is followed by the development of suffocation, a drop in pulse, and loss of consciousness.