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The long term management of animal manures
J. agric. Engng Res. (1973) 18, 1-12
The Long Term
Management
of Animal
Manures
J. R. O’~ALLAGHAN*; V. A. DODD?; K. A. POLLOCK* It is argued that land spreading must be the principal method for the disposal of animal manures. Management of the manures is discussed in terms of a model, based on the mass balance of nutrients within a control area. In the steady state, the rate of application must be balanced by the rate of removal. On an annual basis the rate of application is constrained by the rate of evapotranspiration of a crop and the quantities of NPK which are removed, when the crop is harvested. The model takes into account imports of nutrients in the form of feedingstuffs and chemical fertilizers.
1.
Introduction
Improved production oriented technology has lead to an increase in the number of specialist farmers engaged in either crop or livestock production and the concentration of livestock in small feeding areas, even where there is ample land available. Intensive pig and poultry production units may be located on farms of limited acreage, the feedingstuffs being bought or imported into the farm. Under these circumstances, and in some cattle and milk production units, animal manures are no longer regarded as an asset but as a liability to be disposed of rather than utilized. Use of chemical fertilizers has resulted in a situation in which both arable and grass crops can be produced independently of animal manures without an apparent loss in the inherent fertility of the soil.’ In the past, livestock farmers spread animal manures on land in thes pring and autumn in the semi-solid form of farmyard manure. Current housing methods for intensive livestock units do not require bedding material so that the manures may be handled as a liquid that might be pumped out from a livestock unit onto land at any period of the year. Faced with problems of disposal some farmers resort to spreading manures on land at what could be considered as “dumping” rates of application. This paper discusses the second order effects of indiscriminate dumping of animal manures and puts forward guidelines for the rationalization of the management and disposal of manures by land spreading. 2. Characteristics of animal manures In traditional farming a wide range of feeding rations and housing facilities were employed in livestock production; a practice which was reflected in the variation in published figures on the characteristics of manures.** 3 Present day intensive livestock production units in the U.K. operate as closely as practicable to the optimum in terms of food conversion rate and there is a corresponding trend towards standardization of both feeding rations and housing facilities. Animal manures produced in these units are much more homogeneous than heretofore: the characteristics of such manures are given in summary form in Table I. Urine comprises approximately two-thirds by weight of the manure voided by pigs and cattle. The urine of pigs contains approx. 70,40 and 50 % respectively of the total nitrogen, phosphorus and potassium excreted; the corresponding figures for cattle urine are 60, virtually 0 and 70;( respectively. Berryman has reported that two-thirds of the nitrogen, half the phosphorus and all the potassium in cattle and pig manures are available to the plant during the season of application; four-fifths of the nitrogen, half the phosphorus and all the potassium are the corresponding figures for poultry manure. * Department of Agricultural Engineering, University of Newcastle upon Tyne. t Agricultural
Institute,
Dublin.
2
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURLS
TABLE 1
Characteristics of manures produced by animals housed and fed in accordance with current U.K. practice
-
Manure produced per day
Reference
O’Callaghan et al.’ Stewart et aLd Collins5
Fattening pig Poultry 100 laying hens Fattening cattle 200 kg 450 kg cows
B.O. D.
Dry Matter
Total N
(mail)
(%)
(%)
Total P (%)
Total K (0;)
kg
gal
4.54
1.0
21,500
9.5
0.63
0.16
0.19
12.4
2.7
41,700
23.0
1.5
0.55
0.41
10.5 26.0 32.0
2.3 6.0 7.0
15,000 15,000 15,000
11.1 11.1 11.1
0.51 0.51 0.51
0.06 0.06 0.06
0.47 0.47 0.47
The total manure and its nutrient content from different classes of livestock is given in Table II on an annual basis; dairy cows and beef cattle are housed for approx. 5 months p.a. Table III estimates the quantities of manure to be disposed of in the U.K. from housed animals during the year 1971. TABLE II Manure production p.a.
-
-
Annual manure production
kg
Total N
B.O. D.
gal -_
kg
lb
kg
lb
35.7
78.5
10.5
23.1
Fattening pig place (live wt gain 180 kg/place)
1660
365
Poultry 100 laying hens
4550
1000
190
418
68
Fattening cattle 200 kg450 kg
6660
1470
100
220
34
11,700
2570
176
386
60
cow
Total P
kg
150
74.9
-
TABLE III
Quantities of manure to be disposed of from housed animals in U.K., 1971
Livestock
(m~~~~a~)
Nutrients (thousand t) N P ~~__~___
Pigs Cattle Poultry Total
K
B.O.D., Population Equivalents (millions)
2300 9000 1330
66 209 97
17 25 33
20 196 25
11.2 30.7 12.4
12630
372
75
241
54.3
Note: Housing season for cattle taken to be 5 months.
kg
lb
2.7
5.9
3.2
6.9
25.1
55.3
18.7
41.1
4
8.8
31.3
68.9
7.3
131
lb
Total K
16
55
121
J. R.
O’CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
3
The biochemical oxygen demand (B.O.D.,) of animal manures is extremely high. The B.O.D., of domestic sewage is approximately 400 mg/l with an annual B.O.D. load per capita of 20 kg. The population equivalent in terms of B.O.D. load of the manure produced by housed animals in the U.K. in 1971 is estimated at 54.3 mill. The nutrient content of animal manures is also considerable: 0.372 mill t N, 0.075 mill t P and 0.241 mill t K from housed animals. The cost of purchasing a similar quantity of chemical fertilizers is estimated at &62mill based on prices of &O.11, go.15 and EO.O4/kgrespectively of N, P and K. It is relevant to note that the consumption of chemical fertilizers in England and Wales in 1968 amounted to 0.6 mill t N, 0.15 mill t P and 0.3 mill t K. Estimates predict’ that by 1980 the corresponding figures will be 0.9 mill t N, 0.2 mill t P and 0.4 mill t K. 3. Water pollution and animal manures Discharge to inland watercourses of effluents with B.O.D., values exceeding 20 mg/l is restricted by law in the U.K. so that the direct discharge of animal manures to watercourses is forbidden. The efficiency required of a treatment plant in terms of B.O.D. reduction to permit discharge to a watercourse exceeds 99 % for all manures. The presence of excessive quantities of nutrients particularly N and P in watercourses is undesirable-primarily because of nutrient enrichment and increased growth of aquatic plants, particularly algae which can be a serious nuisance. There is interest in this problem in Britain because of the need to obtain potable water from surface sources and to develop the amenity value of rivers, canals, lakes and multi-purpose water reservoirs.* It is reported9 that concentrations of N and P in excess of 0.30 mg/l and 0.01 mg/l respectively may cause serious algal blooming to occur. However other factors are involved and while the conditions under which blooming occurs may not be completely understood there is general agreement that P is associated in most cases with a “bloom” and that the ingress of N and P to watercourses is undesirable. Water containing nitrate N in excessive quantities may be toxic to babies and the W.H.O. recommendations for drinking water in European countries specify a limit of nitrate N of 11.3 mg/l. 4. Land spreading of manure and water pollution When manure is spread on land it is necessary to ensure that there is no surface runoff and that the drainage water does not carry with it excessive quantities of nutrients and organic compounds. The soil-soil organisms- cover crop matrix must effect a degradation and assimilation of the organic compounds together with the “fixing” and subsequent removal of the nutrients in the manure. Because of climatic conditions in the U.K. the moisture content in most soils is at or above field capacity during the months October to April when there is little growth of crops; the seasonal production of grassland in the U.K. is illustrated in Fig. 1. lo If manure is spread on land during this period, there is a risk of both direct surface runoff as well as the leaching out of organic compounds with a high B.O.D. and chemical nutrients, particularly N. The mobility of nitrate N, the form into which the organic nitrogen in manure is converted microbially, has been demonstrated in many experiments. The quantity leached depends on many factors including date and amount of N applied, soil type and cover crop. Under conditions prevailing in the Netherlands, 750 mm average annual rainfall, 250 mm in period November to February and an average N application of 150 kg/ha p.a. on grassland, Kolenbrander’ ’ estimated, as shown in Fig. I, that up to 40 ‘A of the applied N is lost by leaching on sandy soils with a grass cover crop. The losses in heavy clay soils are lower than in sandy soils because of the lower velocity of water movement in clays. Losses are greater in arable crops than in grass. In old arable soils 30 to 60 kg of N/ha may be mineralized each year and in intensively farmed areas much more N may be released.’
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
D \
z
70-
; n B
60-
‘; P
50-
;
40-
h g
30-
x g h r. 0
zoIO -
L
I
Jan
II
Feb Mar
I
Apr
II
II
May
Jun
Jul
Aug
I
Sept
I
Ott
NW
I
Dee
Jon
Time
Fig. 1. (a) Seasonal production ofgrassland in U.K. Daily dry matter production through the year ofperennial rye-grass irrigated and fertilized with 400 kg/ha of N. (b) Nitrogen losses, by leaching, as a percentage of the nitrogen applied during the year to grassland on a sandy soil
Cooke & Williams’* have reported on the analyses of drainage waters from soils of different types and under different cropping routines on a farm at Woburn in Bedfordshire; a summary of the data is shown in Table IV. Most nitrate was found in drainage water from intensively farmed arable crops on sandy soils and least in the drainage from rough grassland receiving little or no fertilizer. Webber, Lane & Nodwell13 reported on the losses of N from corn crops in Canada. It has been established that in most cases the movement of phosphorus in the soil is minimal and mainly by plant uptake, soil erosion and downward movement of soil particles.‘, 13, l4 The ortho-phosphate anion which is the form of phosphorus available to the plant is quickly adsorbed or precipitated as either calcium, iron or aluminium-phosphate, depending on the nature of the soil. P is then released from these forms in response to crop demands. The essential point, however, is that P contained in the manure must first come in contact with the soil. If the manure is washed off the surface or down through sandy soils by heavy rain occurring subsequent to application there is a risk of P gaining access to watercourses. Preliminary results of land spreading trials of animal manures indicate that heavy storms subsequent to application cause loss of both N and P as well as incomplete retention of B.O.D. by the soil.15
J.
R.
O‘CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
TABLE IV
Averages and ranges of analyses on water from land drains at Woburn” NO,-N mg/l
p 41
Land drain from: Average
Range during year
Average
Range during year
22.5 8.0 3.3 20.3
1626 1-24 l-10 1.5-23
0.08 0.08 0.08 044
NJ.30 o-O.75 O-O.30 CM.70
Intensively-farmed area of sandy soils some arable-some grass Grassland on drift over Oxford Clay Area of high and rough neglected grassland Sandy soil-arable crops
Spreading of manure on land during the winter months October to March when crop growth is low carries a risk of pollution to watercourses with chemical nutrients and organic compounds of high B.O.D. In the case of heavy clay soils the risk is mainly one of direct surface runoff and in sandy soils one of infiltration into the drainage waters. 5. Management of land disposal A livestock production unit may be regarded as an input-output system, the various components of which are shown in Fig. 2. The primary input is feedingstuffs which may in whole or in part be imported into the farm. A pig or poultry enterprise on a grassland farm is an example of a unit into which all feedingstuffs may be imported; a beef fattening unit on grass is a unit into which only a portion of the feedingstuffs, barley, may be imported. Secondary inputs may consist of chemical fertilizers or animal manures. A pig and cattle fattening unit on a grassland farm is a typical example of the latter, the primary input for the pig unit is imported feedingstuffs, while the manure from both the pig unit and the beef unit may be supplemented with chemical fertilizers to provide nutrients for the grass, which in turn forms the input for the beef unit. The outputs of the system are animals and animal products such as milk, eggs and animal manures. The manure is usually retained on the farm but it could be exported neat off the farm. Alternatively the manures could be spread on land to produce a crop which is exported off the farm; e.g. pig manure could be spread on grassland and the conserved grass be sold off the farm. Animals and animal products
Off- form dqxsal
I, ------.--____-_
Chemical ferfllizer
!I
l,
1 r-Off-farm feed SO”ICB
-
:
I ! I
Volatlllzatlon
ILlvestockt
Manure
1 +
SOII
DrlWl
I _Run-off
Off-farm process
II 4 crop _ Sales ,1
II
Crop Farm
L_bou~~y_L_______
Fig. 2. Diagram
\/
showing input and output components
_A
of a livestock
and/or crop production
farm
b
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
In a “steady state” condition, which would apply for long-term management solutions to land spreading, the following conditions must be observed: (i) Spread manure during the growing season in order to avoid direct surface runoff and minimize discharge into drains of leached nutrients and organic compounds. (ii) Spread at such rates as to ensure against excessive accumulations of nutrients N, P and K in the soil. (iii) The amount spread even in the growing season should be within the hydraulic loading capacity of the soil. (iv) The crop must not be detrimental to the animals to which it is fed. The permissible hydraulic loading rates of soils in different climatic areas of the U.K. have been discussed in a previous paper by O’Callaghan, Pollock & Dodd.* The hydraulic loading rate was assessed by comparing the actual evapotranspiration with historical rainfall figures and allowing the manure applied to make up any resultant soil moisture deficit. For area of heavy rainfall like Cardigan with a maximum potential soil moisture deficit of 7.5 mm the mean hydraulic loading rate was estimated for grassland at 24,200 gal/ha p.a. ; in low rainfall areas like Essex with a maximum potential soil moisture deficit of 173 mm the corresponding figure was 49,400 gal/ha p.a. The quantity of nutrients taken up by crops depends on the crop type and yield. The amounts of nutrients removed in average harvested yields of a selection of crops grown in the U.K. is shown in Table V,’ from which it can be seen that grass is the crop capable of removing the TABLE V Amounts
Grass Wheat Barley Potatoes Sugar beet
of nutrients in average crop yields, U.K.7
10 4 (grain) 4 (grain) 50 (tubers) 40
250
30
250
80 70 180 230
12 12 25 20
40 30 200 220
most nutrients. The yield of grass and corresponding nutrient removal or uptake may be increased by increasing the amount of N applied. Reid16 has reported on the effects of the long term application of a wide range, O-900 kg/ha, of N on the yield from perennial rye grass swards with and without white clover. The response of dry matter yield to nitrogen application became insignificant above about 500 kg/ha; the yield curves are shown in Fig. 3. The crude protein content, however, continued to increase beyond the point at which D.M. response ceased; the average yield of crude protein was 4.2 kg/kg N applied which corresponds to an N utilization of 67 % (range 3.8 to 4.5 kg/kg of N). As the crude protein content of grass herbage increases the concentration of NO,-N also increases and it is reported ” that the NO,-N level increased from 0.01% to 0.53 % as N application rates increased from 0 to 800 kg/ha. It has been reported that nitrate poisoning of livestock occurred from consuming forage containing in excess of 0.4 to 0.5% of NO,-N. la Wright & DavidsonJ9 reviewed nitrate accumulation in crops and nitrate poisoning in animals. From their data*O it can be calculated that the LDr,,,*level of NO,-N is about 0.5 to 0*7x. Raymond & Spedding*’ concluded that the danger of nitrate poisoning is not significant at levels of N application where the biological and economic responses are worthwhile which according to Reid16 are 450 to 500 kg/ha p.a. * The concentration which is lethal to 50% of exposed animals.
I.
R.
O‘CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
-
Gross Pure
---
-
clover
I
I
0
and
grass
I
I
I
I
400 N
I
I
I
800
(kg/ho)
Fig. 3. Curves of total yields qf herbage dry matter and herbage crude protein
Excess K in herbage is associated with deficiencies of sodium, calcium and magnesium and the consumption of such herbage often gives rise to hypomagnesaemia. It is reported’ that increasing the concentration of K in herbage dry matter above 1.6% does not give worthwhile increases in yield and increases the risk of hypomagnesaemia in cattle. The utilization of K by grass is close to 100 % so that high application of K results in high concentrations in the herbage.*’ The risk of hypomagnesaemia may be ameliorated by supplementation of the diet with magnesium but levels of K in excess of 3 % are associated with more general mineral imbalances in the animal. McAlister14 reported on the effects on herbage of applying excess P and K arising from land spreading of manures. Soil analyses indicated very high levels of P and K in the surface soil and that 2 types of damage in grass swards occurred; in one the grass sod was easily pulled out by grazing animals and in the other, areas of the sward tended to die off in winter and early spring. The effect was very consistent for K, but variable for P. It is concluded that where grass is grown for conservation the amount of manure applied should be such as to limit the equivalent N application to below 500 kg/ha and that at this level of application yields in the region of 10 to 12 tonnes D.M. can be expected. The corresponding P and K application should be equivalent to approx. 0.2% and l-5 to 3.0% respectively in the resultant crop, although it must be recognized that many soils would benefit from having their total P content raised substantially above existing levels.
8
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
It must be appreciated that not all the nitrogen contained in manures will be utilized by the grass. Some losses by volatilization are inevitable but little experimental evidence on the significance of this loss is available. Where manures are spread on grazed areas the P and K ingested in the herbage is largely recirculated. Hutton, Jury & Daviesz3 reported that the faeces of cows fed entirely on grass contained 26 %, 66 % and 11% respectively of the N, P and K ingested and that the corresponding figures for urine were 53 %, 0 % and 81% respectively. Animal manures spread on grazed areas may cause a health hazard to grazing animals. Cases have been reported24 of poultry pathogens being passed to dairy cows grazing areas on which poultry manure has been applied. It is recommended that if manures have to be spread on grazed areas then the land should not be grazed for at least 6 weeks. In addition the palatability of herbage is affected by excessive dressings of manure unless adequate time is allowed between application and grazing. Cereals respond in a different manner than grass to increasing N, P and K applications. Nitrogen increases yield linearly up to approx. 100 to 150 kg/ha but at higher levels the yield is depressed and the risk of lodging increases. The recommended N dressing for wheat depends on the previous cropping but rarely exceeds 190 kg/ha’ and that for spring barley 150 kg/ha. An additional advantage in using conserved grass as the cover crop in lieu of cereals is that it is feasible to cut grass 3 and in some areas 4 times p.a., each cut of which may receive equivalent N applications of up to approx. 120 to 150 kg/ha, whereas with cereals it would be impracticable to employ multiple dressings. The long term management of animal manures by land spreading must take into account the cropping pattern on the land. The amount of manure applied should be determined on the basis of the nutrient requirements of the crop grown and the permissible hydraulic loading rate, although the latter will probably only be limiting in areas of high rainfall. The following examples are given to illustrate the principles involved. Example I
150 cows plus 1500 pig fattening places 15 kg/cow day for 150 days Winter feed requirements = 340 t dry matter for cows Manure data (a) Pig unit
0.48 million gal/annum Storage tank-O.23 million gal Nutrients/annum N = 15,750 kg P= 4OOOkg K = 4740 kg
(b) Cow unit
O-385 million gal/annum Storage tank-O.16 million gal Nutrient content of storage tank N = 3720 kg P = 460kg K = 3440 kg Assume 10% loss of nutrients. Total manure to be spread/annum-O*708 million gal N = 17,520 kg Nutrients-P= 4OOOkg K = 7340 kg
J.
R.
O’CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
Assume low rainfall area, 3 cuts of grass total equivalent ponse of 20 kg D.M./kg of N applied Conserved Yield t
area ha
of 500 kg/ha,
and res-
34 340
Corresponding
P application
1.2 % of yield D.M.
Corresponding
K application
2.4% of yield D.M.
Hydraulic
N application
load-20,800
gal/ha
Note that there will be an accumulation
of P.
Example 2 10,000 laying hens plus 500 beef cattle Winter
feed requirements for cattle
Manure
8 kg head/day for 150 days = 600 t dry matter
data
(a) Poultry
unit
0.10 million gal/annum Storage tank-O.042 million
gal
Nutrients/annum N = 6800 kg P = 2500 kg K1870kg (b) Beef unit
0.735 million gal/annum Storage tank 0.31 million
Nutrients
gal
in storage tank N = 7100 kg P = 830 kg K = 6530 kg
Assume Total
10% loss of nutrients
manure
to be spread/annum--0*40
Nutrients-
Assume
million
gal
N = 12,500 kg P == 3000 kg K =:= 7500 kg high rainfall
area 2 cuts of grass, response
Expected
yield from organic
Required
yield
Supplement
area
Hydraulic
load
N = 248 t =6OOt
with approx.
Conserved
18 t of chemical
N
= 100 ha = 4000 gal/ha
Corresponding
P application-0.50%
Corresponding
K application-l
Supplement
of 20 kg D.M./kg
of D.M. -25 % of D.M.
with ~1.5 t of fertilizer
K, to give 1.5% in the crop.
N applied,
300 kg/ha p.a
10
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURLS
Example 3 1000 pig places-manure
spread on conserved grassland and crop exported off the farm
Manure data 0.365 million gal/annum Storage tank-O.1 5 million gal Nutrients/annum, N P K
assuming 10 % loss = 9450 kg = 2390 kg = 2840 kg
Land spread at equivalent N application of 500 kg/ha-3
cuts
Conserved area-l 9 ha Yield -190 t Corresponding P application 1.26 % of D.M. Corresponding K application 1.50% of D.M. Hydraulic load-19,200 gal/ha. Note that there will be an accumulation of P. In the examples illustrated a total grass yield 10 t/ha dry matter and a storage period of 5 months have been chosen; these will of course vary from region to region-in colder regions with high rainfall resulting in a lower yield and a later start to the growth season it will be necessary to provide for storage from October to, say, mid-April. It is normal to recommend that at least 6 weeks should elapse between spreading manure and cutting grass, to avoid palatability problems as well as to enable the manures to be adequately broken down. This is particularly important for the first cut of grass, normally taken in late May or early June for which the manure should be spread as early as possible, viz. March or early April. Cattle manure should be applied as early as possible for the first cut because, due to a high fibre content, it has a slow breakdown rate. The examples illustrate the benefits of locating pig and poultry units as closely as possible to grass farms and the difficulties that may arise when they are located in areas where there is no outlet for animal manures. Problems of water pollution have arisen in the Republic of Ireland15 due to intensification of farmyard enterprises, based on pig production from feed imported to the farms, in areas of poor soil on which little farming is carried out, the land being used mainly as a dumping ground for the manures produced from the pigs. 6. Discussion It is submitted that present methods of water conservation and river management which are based on whole hydrological regions rather than on individual points of water abstraction and effluent discharge could be usefully applied to the overall management of animal manures. The farm boundary as shown in Fig. 3 would be replaced by the region’s perimeter or the catchment area of a river basin. Livestock and crop production units could be regarded as point sources of manure production and consumption respectively; chemical fertilizer use could also be monitored and by this means an overall balance for the region established. Nutrient imbalances in a single farm, groups of farms or indeed even in whole regions could be identified and controlled and the haphazard location of intensive livestock production units in unsuitable areas avoided. An assessment of the proposed management programme for animal manures should be part of a Local Authority’s examination of a planning examination for a livestock production unit. The applicant should either farm the land on which manure is to be spread, or have negotiated spreading rights on adequate areas prior to the granting of permission.
J. R. O’CALLAGHAN;
V.
A.
DODD;
K.
II
A. POLLOCK
At the present time there is considerable research both in Europe and the U.S. on feasibility studies of both sanitary and chemical engineering techniques and their possible application in the treatment of animal manures. Considerable emphasis has been laid on biological aerobic oxidation, mainly because of legal constraints on the B.O.D., of effluents discharged to water courses. It would appear that the main contribution of the process will be in the field of odour control, as the process enables a dissolved oxygen concentration to be maintained, thus eliminating odour. Even where a considerable reduction is made in B.O.D. there is little or no reduction in the nutrients contained in the manure, save in certain circumstances where a reduction in nitrogen is possible. Such effluents are likely to be returned to land where disposal should still be made on the basis of an examination of the characteristics of the effluent, with particular reference to its nutrient content and the cropping routine employed. The use of screens, filter presses and similar devices is under examination for separating the urine and faeces components of manures, often with a view to disposing of the liquid fraction by land spreading on the farm and exporting the solid fraction off the farm. Again the land spreading of the liquid fraction should be carried out at such times and rates as to prevent an accumulation of excessive nutrients, in the soil, crop or watercourse. In this context it is relevant to note that the urine fraction of manure, particularly from cattle, contains little phosphorus but most of the nitrogen and potassium so that it may require “balancing” by supplementary dressings of chemical fertilizers. Drying of animal manures, particularly poultry manure, is an example of a technique which enables manure to be transported off the farm in a more convenient form than wet or raw manure and which widens the area over which disposal is possible. 7. Conclusion Animal manures are an integral part of livestock production which can be utilized with considerable benefit in conjunction with chemical fertilizers in the growing of crops with a consequent saving in the consumption of the latter. If manures are regarded as a waste to be disposed of it is considered that the practice will be detrimental to some components of the environment. In certain situations, and particularly in the case of livestock units located on the periphery of urban developments, it may be necessary to condition or treat manures prior to land spreading. More research is required on odour control by aeration and it is submitted that this and other work on treatment should be carried out in the likelihood that the ultimate sink for the manure, whether conditioned or not, will be the soil, the safe loading capacity of which must be considered as an integral component in the scheme as a whole. Acknowledgements The authors are grateful to the Agricultural Research Council for provision of funds to the University for research work on animal operation.
manures and to the Director,
Agricultural
Institute,
Dublin,
for his co-
REFERENCES
Modern Farming and Soil. H.M.S.O., 1970 * O’Callaghan, J. R.; Pollock, K. A.; Dodd, V. A. Land spreading of manures .from animal production units. J. agric. Engng Res., 1971 16 280 ’ O’Callaghan, J. R.; Dodd, V. A.; Poflock, K. A.; O’Donoghue, P. A. J. Characterization of waste treatment properties of pig manure. J. agric. Engng Res., 1971 16 399 A Stewart, T. A.; McIlwain, R. Aerobic storage ofpoultry manure. Proceedings of international symposium on livestock wastes, Ohio. Am. Sot. agric. Engrs, 1971 261 ’ Collins, D. P. Agricultural Institute, Personal Communication, October 1972 6 Berryman, C. Residual values of slurries. Paper presented at the N.A.A.S. Soil Scientists Open Confer’
ence, 1968, Paper SS/O/l16 ’ Cooke, G. W. Fertilizing for maximum yield. Crosby Lockwood, 1972
12
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
a Owens, M. Nutrient balance in rivers. Water Treatment and Examination, 1970 19 239 ’ Vollenweider, J. R. Scientific fundamentals of the eutrophication of lakes and flowing waters, with particular reference to nitrogen and phosphorus. O.E.C.D. Report, Paris 1968 ‘O Anslow, R. C.; Green, J. 0. The seasonalgrowth ofpasture grasses. J. agric. Sci., Camb., 1967 67 109 ” Kolenbrander, G. J. Nitrate content and nitrogen loss in drainage water. Neth. J. agric. Sci., 1969
17 246 I2 Cooke, G. W.; Williams, R. J. B. Losses of nitrogen and phosphorus from agricultural land. Water Treatment and Examination, 1970 19 253 l3 Webber, L. R.; Lane, T. H.; Nodwell, J. H. Gutdelines to land requirements for disposal of liquid manure. University of Guelph, Canada, Paper presented at 8th Industrial Water and Waste Water Conference, Lubbock, Texas, June 1968 l4 McAllister, J. S. V. Nutrient balance on livestock farms. Paper presented to Potash Conference, Hurley, June 1970 I5 The management and disposal of animal manures in the catchment area of Lough Sheelin, Co. Cavan, Ireland. Agricultural Institute, Dublin, April 1972 ‘6 Reid, D. The effects of the long term application of a wide range of nitrogen rates on the yields of perennial rye grass swards with and without white clover. J. agric. Sci., Camb., 1972 79 291 ” Blaxter, K. L. Fertilisers and animal production. Proc. Fertil. Sot., 1968 105 ‘* Hanway, J. S. The nitrate problem. Special Report, No. 34, Iowa State University, August 1963 I9 Wright, M. J.; Davidson, K. L. Nitrate accumulation in crops and nitrate poisoning in animals. Adv. Agron. 1964 16 197 2o Holmes, W. The use of nitrogen in the management of pasture jar cattle. Herb. Abstr., 1968 38 265 21 Raymond, W. F.; Spedding, C. R. W. The efict of fertilizers on the nutritive value and production potential of forages. Proc. Fertil. Sot., 88 1965 22 Rogers, P. A. M. The significance of artificial nitrogenous and potassic fertilizers in the aetiology of hypomagnesaernia and grass tetany. It-. vet. J., 1967 21 162 23 Hutton, J. B.; Jury, K. E.; Davies, E. B. Studies of the nutritive value of New Zealand dairy pastures. 5. The intake and utilisation ofpotassium, sodium, calcium, phosphorus, and nitrogen in pasture herbage by lactating dairy cattle. N.Z. J. agric. Res., 1967 10 367 24 Taken for Granted. Report of the Working Party on Sewage Disposal. H.M.S.O., 1970 41
The Long Term
Management
of Animal
Manures
J. R. O’~ALLAGHAN*; V. A. DODD?; K. A. POLLOCK* It is argued that land spreading must be the principal method for the disposal of animal manures. Management of the manures is discussed in terms of a model, based on the mass balance of nutrients within a control area. In the steady state, the rate of application must be balanced by the rate of removal. On an annual basis the rate of application is constrained by the rate of evapotranspiration of a crop and the quantities of NPK which are removed, when the crop is harvested. The model takes into account imports of nutrients in the form of feedingstuffs and chemical fertilizers.
1.
Introduction
Improved production oriented technology has lead to an increase in the number of specialist farmers engaged in either crop or livestock production and the concentration of livestock in small feeding areas, even where there is ample land available. Intensive pig and poultry production units may be located on farms of limited acreage, the feedingstuffs being bought or imported into the farm. Under these circumstances, and in some cattle and milk production units, animal manures are no longer regarded as an asset but as a liability to be disposed of rather than utilized. Use of chemical fertilizers has resulted in a situation in which both arable and grass crops can be produced independently of animal manures without an apparent loss in the inherent fertility of the soil.’ In the past, livestock farmers spread animal manures on land in thes pring and autumn in the semi-solid form of farmyard manure. Current housing methods for intensive livestock units do not require bedding material so that the manures may be handled as a liquid that might be pumped out from a livestock unit onto land at any period of the year. Faced with problems of disposal some farmers resort to spreading manures on land at what could be considered as “dumping” rates of application. This paper discusses the second order effects of indiscriminate dumping of animal manures and puts forward guidelines for the rationalization of the management and disposal of manures by land spreading. 2. Characteristics of animal manures In traditional farming a wide range of feeding rations and housing facilities were employed in livestock production; a practice which was reflected in the variation in published figures on the characteristics of manures.** 3 Present day intensive livestock production units in the U.K. operate as closely as practicable to the optimum in terms of food conversion rate and there is a corresponding trend towards standardization of both feeding rations and housing facilities. Animal manures produced in these units are much more homogeneous than heretofore: the characteristics of such manures are given in summary form in Table I. Urine comprises approximately two-thirds by weight of the manure voided by pigs and cattle. The urine of pigs contains approx. 70,40 and 50 % respectively of the total nitrogen, phosphorus and potassium excreted; the corresponding figures for cattle urine are 60, virtually 0 and 70;( respectively. Berryman has reported that two-thirds of the nitrogen, half the phosphorus and all the potassium in cattle and pig manures are available to the plant during the season of application; four-fifths of the nitrogen, half the phosphorus and all the potassium are the corresponding figures for poultry manure. * Department of Agricultural Engineering, University of Newcastle upon Tyne. t Agricultural
Institute,
Dublin.
2
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURLS
TABLE 1
Characteristics of manures produced by animals housed and fed in accordance with current U.K. practice
-
Manure produced per day
Reference
O’Callaghan et al.’ Stewart et aLd Collins5
Fattening pig Poultry 100 laying hens Fattening cattle 200 kg 450 kg cows
B.O. D.
Dry Matter
Total N
(mail)
(%)
(%)
Total P (%)
Total K (0;)
kg
gal
4.54
1.0
21,500
9.5
0.63
0.16
0.19
12.4
2.7
41,700
23.0
1.5
0.55
0.41
10.5 26.0 32.0
2.3 6.0 7.0
15,000 15,000 15,000
11.1 11.1 11.1
0.51 0.51 0.51
0.06 0.06 0.06
0.47 0.47 0.47
The total manure and its nutrient content from different classes of livestock is given in Table II on an annual basis; dairy cows and beef cattle are housed for approx. 5 months p.a. Table III estimates the quantities of manure to be disposed of in the U.K. from housed animals during the year 1971. TABLE II Manure production p.a.
-
-
Annual manure production
kg
Total N
B.O. D.
gal -_
kg
lb
kg
lb
35.7
78.5
10.5
23.1
Fattening pig place (live wt gain 180 kg/place)
1660
365
Poultry 100 laying hens
4550
1000
190
418
68
Fattening cattle 200 kg450 kg
6660
1470
100
220
34
11,700
2570
176
386
60
cow
Total P
kg
150
74.9
-
TABLE III
Quantities of manure to be disposed of from housed animals in U.K., 1971
Livestock
(m~~~~a~)
Nutrients (thousand t) N P ~~__~___
Pigs Cattle Poultry Total
K
B.O.D., Population Equivalents (millions)
2300 9000 1330
66 209 97
17 25 33
20 196 25
11.2 30.7 12.4
12630
372
75
241
54.3
Note: Housing season for cattle taken to be 5 months.
kg
lb
2.7
5.9
3.2
6.9
25.1
55.3
18.7
41.1
4
8.8
31.3
68.9
7.3
131
lb
Total K
16
55
121
J. R.
O’CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
3
The biochemical oxygen demand (B.O.D.,) of animal manures is extremely high. The B.O.D., of domestic sewage is approximately 400 mg/l with an annual B.O.D. load per capita of 20 kg. The population equivalent in terms of B.O.D. load of the manure produced by housed animals in the U.K. in 1971 is estimated at 54.3 mill. The nutrient content of animal manures is also considerable: 0.372 mill t N, 0.075 mill t P and 0.241 mill t K from housed animals. The cost of purchasing a similar quantity of chemical fertilizers is estimated at &62mill based on prices of &O.11, go.15 and EO.O4/kgrespectively of N, P and K. It is relevant to note that the consumption of chemical fertilizers in England and Wales in 1968 amounted to 0.6 mill t N, 0.15 mill t P and 0.3 mill t K. Estimates predict’ that by 1980 the corresponding figures will be 0.9 mill t N, 0.2 mill t P and 0.4 mill t K. 3. Water pollution and animal manures Discharge to inland watercourses of effluents with B.O.D., values exceeding 20 mg/l is restricted by law in the U.K. so that the direct discharge of animal manures to watercourses is forbidden. The efficiency required of a treatment plant in terms of B.O.D. reduction to permit discharge to a watercourse exceeds 99 % for all manures. The presence of excessive quantities of nutrients particularly N and P in watercourses is undesirable-primarily because of nutrient enrichment and increased growth of aquatic plants, particularly algae which can be a serious nuisance. There is interest in this problem in Britain because of the need to obtain potable water from surface sources and to develop the amenity value of rivers, canals, lakes and multi-purpose water reservoirs.* It is reported9 that concentrations of N and P in excess of 0.30 mg/l and 0.01 mg/l respectively may cause serious algal blooming to occur. However other factors are involved and while the conditions under which blooming occurs may not be completely understood there is general agreement that P is associated in most cases with a “bloom” and that the ingress of N and P to watercourses is undesirable. Water containing nitrate N in excessive quantities may be toxic to babies and the W.H.O. recommendations for drinking water in European countries specify a limit of nitrate N of 11.3 mg/l. 4. Land spreading of manure and water pollution When manure is spread on land it is necessary to ensure that there is no surface runoff and that the drainage water does not carry with it excessive quantities of nutrients and organic compounds. The soil-soil organisms- cover crop matrix must effect a degradation and assimilation of the organic compounds together with the “fixing” and subsequent removal of the nutrients in the manure. Because of climatic conditions in the U.K. the moisture content in most soils is at or above field capacity during the months October to April when there is little growth of crops; the seasonal production of grassland in the U.K. is illustrated in Fig. 1. lo If manure is spread on land during this period, there is a risk of both direct surface runoff as well as the leaching out of organic compounds with a high B.O.D. and chemical nutrients, particularly N. The mobility of nitrate N, the form into which the organic nitrogen in manure is converted microbially, has been demonstrated in many experiments. The quantity leached depends on many factors including date and amount of N applied, soil type and cover crop. Under conditions prevailing in the Netherlands, 750 mm average annual rainfall, 250 mm in period November to February and an average N application of 150 kg/ha p.a. on grassland, Kolenbrander’ ’ estimated, as shown in Fig. I, that up to 40 ‘A of the applied N is lost by leaching on sandy soils with a grass cover crop. The losses in heavy clay soils are lower than in sandy soils because of the lower velocity of water movement in clays. Losses are greater in arable crops than in grass. In old arable soils 30 to 60 kg of N/ha may be mineralized each year and in intensively farmed areas much more N may be released.’
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
D \
z
70-
; n B
60-
‘; P
50-
;
40-
h g
30-
x g h r. 0
zoIO -
L
I
Jan
II
Feb Mar
I
Apr
II
II
May
Jun
Jul
Aug
I
Sept
I
Ott
NW
I
Dee
Jon
Time
Fig. 1. (a) Seasonal production ofgrassland in U.K. Daily dry matter production through the year ofperennial rye-grass irrigated and fertilized with 400 kg/ha of N. (b) Nitrogen losses, by leaching, as a percentage of the nitrogen applied during the year to grassland on a sandy soil
Cooke & Williams’* have reported on the analyses of drainage waters from soils of different types and under different cropping routines on a farm at Woburn in Bedfordshire; a summary of the data is shown in Table IV. Most nitrate was found in drainage water from intensively farmed arable crops on sandy soils and least in the drainage from rough grassland receiving little or no fertilizer. Webber, Lane & Nodwell13 reported on the losses of N from corn crops in Canada. It has been established that in most cases the movement of phosphorus in the soil is minimal and mainly by plant uptake, soil erosion and downward movement of soil particles.‘, 13, l4 The ortho-phosphate anion which is the form of phosphorus available to the plant is quickly adsorbed or precipitated as either calcium, iron or aluminium-phosphate, depending on the nature of the soil. P is then released from these forms in response to crop demands. The essential point, however, is that P contained in the manure must first come in contact with the soil. If the manure is washed off the surface or down through sandy soils by heavy rain occurring subsequent to application there is a risk of P gaining access to watercourses. Preliminary results of land spreading trials of animal manures indicate that heavy storms subsequent to application cause loss of both N and P as well as incomplete retention of B.O.D. by the soil.15
J.
R.
O‘CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
TABLE IV
Averages and ranges of analyses on water from land drains at Woburn” NO,-N mg/l
p 41
Land drain from: Average
Range during year
Average
Range during year
22.5 8.0 3.3 20.3
1626 1-24 l-10 1.5-23
0.08 0.08 0.08 044
NJ.30 o-O.75 O-O.30 CM.70
Intensively-farmed area of sandy soils some arable-some grass Grassland on drift over Oxford Clay Area of high and rough neglected grassland Sandy soil-arable crops
Spreading of manure on land during the winter months October to March when crop growth is low carries a risk of pollution to watercourses with chemical nutrients and organic compounds of high B.O.D. In the case of heavy clay soils the risk is mainly one of direct surface runoff and in sandy soils one of infiltration into the drainage waters. 5. Management of land disposal A livestock production unit may be regarded as an input-output system, the various components of which are shown in Fig. 2. The primary input is feedingstuffs which may in whole or in part be imported into the farm. A pig or poultry enterprise on a grassland farm is an example of a unit into which all feedingstuffs may be imported; a beef fattening unit on grass is a unit into which only a portion of the feedingstuffs, barley, may be imported. Secondary inputs may consist of chemical fertilizers or animal manures. A pig and cattle fattening unit on a grassland farm is a typical example of the latter, the primary input for the pig unit is imported feedingstuffs, while the manure from both the pig unit and the beef unit may be supplemented with chemical fertilizers to provide nutrients for the grass, which in turn forms the input for the beef unit. The outputs of the system are animals and animal products such as milk, eggs and animal manures. The manure is usually retained on the farm but it could be exported neat off the farm. Alternatively the manures could be spread on land to produce a crop which is exported off the farm; e.g. pig manure could be spread on grassland and the conserved grass be sold off the farm. Animals and animal products
Off- form dqxsal
I, ------.--____-_
Chemical ferfllizer
!I
l,
1 r-Off-farm feed SO”ICB
-
:
I ! I
Volatlllzatlon
ILlvestockt
Manure
1 +
SOII
DrlWl
I _Run-off
Off-farm process
II 4 crop _ Sales ,1
II
Crop Farm
L_bou~~y_L_______
Fig. 2. Diagram
\/
showing input and output components
_A
of a livestock
and/or crop production
farm
b
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
In a “steady state” condition, which would apply for long-term management solutions to land spreading, the following conditions must be observed: (i) Spread manure during the growing season in order to avoid direct surface runoff and minimize discharge into drains of leached nutrients and organic compounds. (ii) Spread at such rates as to ensure against excessive accumulations of nutrients N, P and K in the soil. (iii) The amount spread even in the growing season should be within the hydraulic loading capacity of the soil. (iv) The crop must not be detrimental to the animals to which it is fed. The permissible hydraulic loading rates of soils in different climatic areas of the U.K. have been discussed in a previous paper by O’Callaghan, Pollock & Dodd.* The hydraulic loading rate was assessed by comparing the actual evapotranspiration with historical rainfall figures and allowing the manure applied to make up any resultant soil moisture deficit. For area of heavy rainfall like Cardigan with a maximum potential soil moisture deficit of 7.5 mm the mean hydraulic loading rate was estimated for grassland at 24,200 gal/ha p.a. ; in low rainfall areas like Essex with a maximum potential soil moisture deficit of 173 mm the corresponding figure was 49,400 gal/ha p.a. The quantity of nutrients taken up by crops depends on the crop type and yield. The amounts of nutrients removed in average harvested yields of a selection of crops grown in the U.K. is shown in Table V,’ from which it can be seen that grass is the crop capable of removing the TABLE V Amounts
Grass Wheat Barley Potatoes Sugar beet
of nutrients in average crop yields, U.K.7
10 4 (grain) 4 (grain) 50 (tubers) 40
250
30
250
80 70 180 230
12 12 25 20
40 30 200 220
most nutrients. The yield of grass and corresponding nutrient removal or uptake may be increased by increasing the amount of N applied. Reid16 has reported on the effects of the long term application of a wide range, O-900 kg/ha, of N on the yield from perennial rye grass swards with and without white clover. The response of dry matter yield to nitrogen application became insignificant above about 500 kg/ha; the yield curves are shown in Fig. 3. The crude protein content, however, continued to increase beyond the point at which D.M. response ceased; the average yield of crude protein was 4.2 kg/kg N applied which corresponds to an N utilization of 67 % (range 3.8 to 4.5 kg/kg of N). As the crude protein content of grass herbage increases the concentration of NO,-N also increases and it is reported ” that the NO,-N level increased from 0.01% to 0.53 % as N application rates increased from 0 to 800 kg/ha. It has been reported that nitrate poisoning of livestock occurred from consuming forage containing in excess of 0.4 to 0.5% of NO,-N. la Wright & DavidsonJ9 reviewed nitrate accumulation in crops and nitrate poisoning in animals. From their data*O it can be calculated that the LDr,,,*level of NO,-N is about 0.5 to 0*7x. Raymond & Spedding*’ concluded that the danger of nitrate poisoning is not significant at levels of N application where the biological and economic responses are worthwhile which according to Reid16 are 450 to 500 kg/ha p.a. * The concentration which is lethal to 50% of exposed animals.
I.
R.
O‘CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
-
Gross Pure
---
-
clover
I
I
0
and
grass
I
I
I
I
400 N
I
I
I
800
(kg/ho)
Fig. 3. Curves of total yields qf herbage dry matter and herbage crude protein
Excess K in herbage is associated with deficiencies of sodium, calcium and magnesium and the consumption of such herbage often gives rise to hypomagnesaemia. It is reported’ that increasing the concentration of K in herbage dry matter above 1.6% does not give worthwhile increases in yield and increases the risk of hypomagnesaemia in cattle. The utilization of K by grass is close to 100 % so that high application of K results in high concentrations in the herbage.*’ The risk of hypomagnesaemia may be ameliorated by supplementation of the diet with magnesium but levels of K in excess of 3 % are associated with more general mineral imbalances in the animal. McAlister14 reported on the effects on herbage of applying excess P and K arising from land spreading of manures. Soil analyses indicated very high levels of P and K in the surface soil and that 2 types of damage in grass swards occurred; in one the grass sod was easily pulled out by grazing animals and in the other, areas of the sward tended to die off in winter and early spring. The effect was very consistent for K, but variable for P. It is concluded that where grass is grown for conservation the amount of manure applied should be such as to limit the equivalent N application to below 500 kg/ha and that at this level of application yields in the region of 10 to 12 tonnes D.M. can be expected. The corresponding P and K application should be equivalent to approx. 0.2% and l-5 to 3.0% respectively in the resultant crop, although it must be recognized that many soils would benefit from having their total P content raised substantially above existing levels.
8
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
It must be appreciated that not all the nitrogen contained in manures will be utilized by the grass. Some losses by volatilization are inevitable but little experimental evidence on the significance of this loss is available. Where manures are spread on grazed areas the P and K ingested in the herbage is largely recirculated. Hutton, Jury & Daviesz3 reported that the faeces of cows fed entirely on grass contained 26 %, 66 % and 11% respectively of the N, P and K ingested and that the corresponding figures for urine were 53 %, 0 % and 81% respectively. Animal manures spread on grazed areas may cause a health hazard to grazing animals. Cases have been reported24 of poultry pathogens being passed to dairy cows grazing areas on which poultry manure has been applied. It is recommended that if manures have to be spread on grazed areas then the land should not be grazed for at least 6 weeks. In addition the palatability of herbage is affected by excessive dressings of manure unless adequate time is allowed between application and grazing. Cereals respond in a different manner than grass to increasing N, P and K applications. Nitrogen increases yield linearly up to approx. 100 to 150 kg/ha but at higher levels the yield is depressed and the risk of lodging increases. The recommended N dressing for wheat depends on the previous cropping but rarely exceeds 190 kg/ha’ and that for spring barley 150 kg/ha. An additional advantage in using conserved grass as the cover crop in lieu of cereals is that it is feasible to cut grass 3 and in some areas 4 times p.a., each cut of which may receive equivalent N applications of up to approx. 120 to 150 kg/ha, whereas with cereals it would be impracticable to employ multiple dressings. The long term management of animal manures by land spreading must take into account the cropping pattern on the land. The amount of manure applied should be determined on the basis of the nutrient requirements of the crop grown and the permissible hydraulic loading rate, although the latter will probably only be limiting in areas of high rainfall. The following examples are given to illustrate the principles involved. Example I
150 cows plus 1500 pig fattening places 15 kg/cow day for 150 days Winter feed requirements = 340 t dry matter for cows Manure data (a) Pig unit
0.48 million gal/annum Storage tank-O.23 million gal Nutrients/annum N = 15,750 kg P= 4OOOkg K = 4740 kg
(b) Cow unit
O-385 million gal/annum Storage tank-O.16 million gal Nutrient content of storage tank N = 3720 kg P = 460kg K = 3440 kg Assume 10% loss of nutrients. Total manure to be spread/annum-O*708 million gal N = 17,520 kg Nutrients-P= 4OOOkg K = 7340 kg
J.
R.
O’CALLAGHAN;
V.
A.
DODD;
K.
A.
POLLOCK
Assume low rainfall area, 3 cuts of grass total equivalent ponse of 20 kg D.M./kg of N applied Conserved Yield t
area ha
of 500 kg/ha,
and res-
34 340
Corresponding
P application
1.2 % of yield D.M.
Corresponding
K application
2.4% of yield D.M.
Hydraulic
N application
load-20,800
gal/ha
Note that there will be an accumulation
of P.
Example 2 10,000 laying hens plus 500 beef cattle Winter
feed requirements for cattle
Manure
8 kg head/day for 150 days = 600 t dry matter
data
(a) Poultry
unit
0.10 million gal/annum Storage tank-O.042 million
gal
Nutrients/annum N = 6800 kg P = 2500 kg K1870kg (b) Beef unit
0.735 million gal/annum Storage tank 0.31 million
Nutrients
gal
in storage tank N = 7100 kg P = 830 kg K = 6530 kg
Assume Total
10% loss of nutrients
manure
to be spread/annum--0*40
Nutrients-
Assume
million
gal
N = 12,500 kg P == 3000 kg K =:= 7500 kg high rainfall
area 2 cuts of grass, response
Expected
yield from organic
Required
yield
Supplement
area
Hydraulic
load
N = 248 t =6OOt
with approx.
Conserved
18 t of chemical
N
= 100 ha = 4000 gal/ha
Corresponding
P application-0.50%
Corresponding
K application-l
Supplement
of 20 kg D.M./kg
of D.M. -25 % of D.M.
with ~1.5 t of fertilizer
K, to give 1.5% in the crop.
N applied,
300 kg/ha p.a
10
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURLS
Example 3 1000 pig places-manure
spread on conserved grassland and crop exported off the farm
Manure data 0.365 million gal/annum Storage tank-O.1 5 million gal Nutrients/annum, N P K
assuming 10 % loss = 9450 kg = 2390 kg = 2840 kg
Land spread at equivalent N application of 500 kg/ha-3
cuts
Conserved area-l 9 ha Yield -190 t Corresponding P application 1.26 % of D.M. Corresponding K application 1.50% of D.M. Hydraulic load-19,200 gal/ha. Note that there will be an accumulation of P. In the examples illustrated a total grass yield 10 t/ha dry matter and a storage period of 5 months have been chosen; these will of course vary from region to region-in colder regions with high rainfall resulting in a lower yield and a later start to the growth season it will be necessary to provide for storage from October to, say, mid-April. It is normal to recommend that at least 6 weeks should elapse between spreading manure and cutting grass, to avoid palatability problems as well as to enable the manures to be adequately broken down. This is particularly important for the first cut of grass, normally taken in late May or early June for which the manure should be spread as early as possible, viz. March or early April. Cattle manure should be applied as early as possible for the first cut because, due to a high fibre content, it has a slow breakdown rate. The examples illustrate the benefits of locating pig and poultry units as closely as possible to grass farms and the difficulties that may arise when they are located in areas where there is no outlet for animal manures. Problems of water pollution have arisen in the Republic of Ireland15 due to intensification of farmyard enterprises, based on pig production from feed imported to the farms, in areas of poor soil on which little farming is carried out, the land being used mainly as a dumping ground for the manures produced from the pigs. 6. Discussion It is submitted that present methods of water conservation and river management which are based on whole hydrological regions rather than on individual points of water abstraction and effluent discharge could be usefully applied to the overall management of animal manures. The farm boundary as shown in Fig. 3 would be replaced by the region’s perimeter or the catchment area of a river basin. Livestock and crop production units could be regarded as point sources of manure production and consumption respectively; chemical fertilizer use could also be monitored and by this means an overall balance for the region established. Nutrient imbalances in a single farm, groups of farms or indeed even in whole regions could be identified and controlled and the haphazard location of intensive livestock production units in unsuitable areas avoided. An assessment of the proposed management programme for animal manures should be part of a Local Authority’s examination of a planning examination for a livestock production unit. The applicant should either farm the land on which manure is to be spread, or have negotiated spreading rights on adequate areas prior to the granting of permission.
J. R. O’CALLAGHAN;
V.
A.
DODD;
K.
II
A. POLLOCK
At the present time there is considerable research both in Europe and the U.S. on feasibility studies of both sanitary and chemical engineering techniques and their possible application in the treatment of animal manures. Considerable emphasis has been laid on biological aerobic oxidation, mainly because of legal constraints on the B.O.D., of effluents discharged to water courses. It would appear that the main contribution of the process will be in the field of odour control, as the process enables a dissolved oxygen concentration to be maintained, thus eliminating odour. Even where a considerable reduction is made in B.O.D. there is little or no reduction in the nutrients contained in the manure, save in certain circumstances where a reduction in nitrogen is possible. Such effluents are likely to be returned to land where disposal should still be made on the basis of an examination of the characteristics of the effluent, with particular reference to its nutrient content and the cropping routine employed. The use of screens, filter presses and similar devices is under examination for separating the urine and faeces components of manures, often with a view to disposing of the liquid fraction by land spreading on the farm and exporting the solid fraction off the farm. Again the land spreading of the liquid fraction should be carried out at such times and rates as to prevent an accumulation of excessive nutrients, in the soil, crop or watercourse. In this context it is relevant to note that the urine fraction of manure, particularly from cattle, contains little phosphorus but most of the nitrogen and potassium so that it may require “balancing” by supplementary dressings of chemical fertilizers. Drying of animal manures, particularly poultry manure, is an example of a technique which enables manure to be transported off the farm in a more convenient form than wet or raw manure and which widens the area over which disposal is possible. 7. Conclusion Animal manures are an integral part of livestock production which can be utilized with considerable benefit in conjunction with chemical fertilizers in the growing of crops with a consequent saving in the consumption of the latter. If manures are regarded as a waste to be disposed of it is considered that the practice will be detrimental to some components of the environment. In certain situations, and particularly in the case of livestock units located on the periphery of urban developments, it may be necessary to condition or treat manures prior to land spreading. More research is required on odour control by aeration and it is submitted that this and other work on treatment should be carried out in the likelihood that the ultimate sink for the manure, whether conditioned or not, will be the soil, the safe loading capacity of which must be considered as an integral component in the scheme as a whole. Acknowledgements The authors are grateful to the Agricultural Research Council for provision of funds to the University for research work on animal operation.
manures and to the Director,
Agricultural
Institute,
Dublin,
for his co-
REFERENCES
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12
LONG
TERM
MANAGEMENT
OF
ANIMAL
MANURES
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17 246 I2 Cooke, G. W.; Williams, R. J. B. Losses of nitrogen and phosphorus from agricultural land. Water Treatment and Examination, 1970 19 253 l3 Webber, L. R.; Lane, T. H.; Nodwell, J. H. Gutdelines to land requirements for disposal of liquid manure. University of Guelph, Canada, Paper presented at 8th Industrial Water and Waste Water Conference, Lubbock, Texas, June 1968 l4 McAllister, J. S. V. Nutrient balance on livestock farms. Paper presented to Potash Conference, Hurley, June 1970 I5 The management and disposal of animal manures in the catchment area of Lough Sheelin, Co. Cavan, Ireland. Agricultural Institute, Dublin, April 1972 ‘6 Reid, D. The effects of the long term application of a wide range of nitrogen rates on the yields of perennial rye grass swards with and without white clover. J. agric. Sci., Camb., 1972 79 291 ” Blaxter, K. L. Fertilisers and animal production. Proc. Fertil. Sot., 1968 105 ‘* Hanway, J. S. The nitrate problem. Special Report, No. 34, Iowa State University, August 1963 I9 Wright, M. J.; Davidson, K. L. Nitrate accumulation in crops and nitrate poisoning in animals. Adv. Agron. 1964 16 197 2o Holmes, W. The use of nitrogen in the management of pasture jar cattle. Herb. Abstr., 1968 38 265 21 Raymond, W. F.; Spedding, C. R. W. The efict of fertilizers on the nutritive value and production potential of forages. Proc. Fertil. Sot., 88 1965 22 Rogers, P. A. M. The significance of artificial nitrogenous and potassic fertilizers in the aetiology of hypomagnesaernia and grass tetany. It-. vet. J., 1967 21 162 23 Hutton, J. B.; Jury, K. E.; Davies, E. B. Studies of the nutritive value of New Zealand dairy pastures. 5. The intake and utilisation ofpotassium, sodium, calcium, phosphorus, and nitrogen in pasture herbage by lactating dairy cattle. N.Z. J. agric. Res., 1967 10 367 24 Taken for Granted. Report of the Working Party on Sewage Disposal. H.M.S.O., 1970 41