A study of nutrient balance in selected urban and peri-urban communes in Hue City with high densities of livestock

Vo Thi Kim Thanh

Hue University of Agriculture and Forestry
Hue, Vietnam
vokimthanh@hotmail.com

Abstract

Livestock give the urban and peri-urban people a considerable part of their income, but in many urban and peri-urban areas with high densities of livestock problems have occurred due to accumulation of nutrients, in particular N, P and K. This has resulted in pollution both of soil and drinking water. Hue city reported there were a large number of pigs, poultry, buffaloes and cattle in urban areas. With the information on nutrient balance i.e. the N, P and K entering and leaving the area and levels accumulating in soils and water courses, the study shows that along with high livestock densities a large percentage of the area is presenting nutrient overload. Approximately 4 tonnes/day of fresh manure could be collected from 370 households keeping animals in the study area, not including other waste such as liquid waste from the animal house.

Chemical composition of soil collected around the farm was 0.04% of P₂O₅ and 0.2% of K₂O , and content of P and K in garden water was 1.5 and 6.4 micro-mol/litre, in a local pond 1.4 and 4 micromol/litre and from a river near the survey area 1 and 5 micromol/litre, respectively.

This study emphasizes the need for regulations that will be necessary to avoid large-scale future pollution.

Introduction

In many urban and peri-urban areas with high densities of livestock serious problems have occurred due to accumulation of nutrients, in particular N, P and K. This has resulted in pollution both of soil and drinking water (Bouwman 1997; Skerman 2002). Hue city reported there were a large number of pigs, poultry, buffaloes and cattle in urban areas (Vo Thi Kim Thanh et al 2001), as is the general situation in many parts of South East Asia (Gerber et al 2004).

There is no information on nutrient balance, i.e. the N, P and K, entering and leaving the area and levels accumulating in soils and water courses in Hue city. Information on these is becoming necessary in order to provide a basis for regulations to avoid large-scale future pollution problems. The study is based on a survey to provide preliminary information on nutrient balance in some selected urban and peri-urban areas of Hue City.

Materials and methods

Structured interviews were carried out using questionnaires to collect data from households and administration authorities, and soil and water samples were collected for analysis.

Results and discussion

Population density and land use

Table 1. Population density and land use
	People/ha	Families/ha	Engaged in agriculture (%)	Households with livestock (%)
Urban	124	21	2	9
Peri-urban	31	4	28	39

Data on 6 urban and peri-urban wards were collected from the records of the local offices. These show the total population and number of families per ha of land, and the proportion of agricultural families and proportion that keep animals (Table 1). In both urban and peri-urban areas the number of households keeping livestock was higher than households engaged in agricultural activities.

Livestock numbers in the wards surveyed

Table 2. Livestock numbers (% of total animals)
	Buffaloes	Cattle	Pigs	Chickens	Ducks
Urban	0.1	0.3	13	78	9
Peri-urban	0.1	0.2	19	77	4

According to the data from the local offices, the numbers of chickens were highest and similar in both urban and peri urban areas. The proportion of ducks was twice as high in urban than in peri-urban wards.

Manure disposal from livestock production

Table 3. Manure from livestock production
No of hh	Land (m²/farm)	Keeping livestock (hh)	Manure (kg/ day)
570	1200	370	3751
Data from interviewed households (hh)

The manure from animal production (Table 3) does not include other wastes, such as litter, feed refused and liquid wastes, which also increase nutrient levels in agricultural land and residential areas. A serious problem is that 54% (urban) and 39% (peri-urban) of these households pour wastes into drains or rivers, which will cause water pollution. When manure enters surface waters, excess nutrients and organic materials are added. Increasing nutrient levels can cause excessive growth of aquatic plants and algae. The decomposition of aquatic plants depletes the oxygen supply in the water, creating anoxic or anaerobic conditions which can lead to fish kills (NRDC 2001; Goreau 1994). Also several diseases from microorganisms in livestock waste can be contracted through direct contact with contaminated water, consumption of contaminated drinking water, or consumption of contaminated shellfish (Forum of SustainableAgri-Food Production and Consumption 2002). Between 6 and 5 % of households put livestock wastes into rubbish containers, which may cause complaints from people nearby (Table 4).

Table 4. Manure disposal (% of interviewed households)
	Urban	Peri-urban
Give away	12	8
Use as fertilizer	11	40
Store	8	7
Put in rubbish container	15	6
Pour in drains or rivers	54	39

N, P, K from crop and livestock production

About 9% of the families interviewed use NPK fertilizer in their fields and gardens.Results from soils and watercourses analyzed show the consequences on soil and water (Table 5). The data from the soil analyses show that the content of P₂O₅ amounted to overload; however, the samples were selected from the land around the animal houses and in farm gardens, and so were un-typically high values.

Table 5. P and K content in soils and water courses
	'n'	Mean	Median	SD	SEM	Minimum	Maximum
In soil (%)
P₂O₅	30	0.04	0.04	0.01	0.001	0.3	0.6
K₂O	30	0.19	0.2	0.05	0.009	0.1	0.3
In water courses (μmol/litre)
Pond
P₂O₅	6	1.4	1.3	0.7	0.3	0.8	2.7
K₂O	6	4.0	3.6	1.1	0.5	3.1	6.2
River
P₂O₅	2	1.1	1.1	0.2	0.1	1	1.3
K₂O	2	5.1	5.1	0	0	5.1	5.1
Garden
P₂O₅	7	1.5	1.2	0.8	0.3	0.8	2.6
K₂O	7	6.4	4.1	4.4	1.7	3.6	15.4

P and K concentrations in ponds and gardens were variable, because they depend on the number of livestock kept. The maximum concentration of P₂O₅ found was 2.6 μmol/litre and of K₂O 15.4 μmol/l, in water from a garden in Thuan Loc ward, where the farmer spread directly the wastes from his pig house onto the garden. Also in Thuan Loc, the P and K concentrations in pond water were highest because the ward includes high numbers of livestock (20 cattle, 319 pigs, 3100 chickens and 230 ducks on 114 farms of those interviewed, and 39% of these pour wastes from the animal houses into the drains). In Phu Hiep ward the second highest concentrations of P and K in pond water were found (1.4 and 4.1 μmol/litre). The concentration of P in water below which growth of aquatic plants and algae decreases is 0.1 μmol/litre according to Goreau (1994). Also in this ward high numbers of livestock are kept: 10 cattle, 563 pigs, 1567 chickens and 300 ducks in the 120 households interviewed, and 64 % of the farmers pour the wastes from the animal house into the drain or river.

Conclusions

The survey and chemical analyses provide preliminary information on nutrient balance and the potential environmental impacts of producing livestock in the city.
The higher economic development of areas were related to the high densities of animals in urban and peri-urban areas, where uptake of nutrients by crops is low.
These observations suggest that there is high potential for better integration of crop and livestock activities in peri-urban areas. An animal keeping policy formulation is needed and development of technologies such as the biogas system in the urban areas is required. Also needed are control instruments (land/livestock balances; environmental authorization), economic instruments (subsidies for investment in manure management equipment), the integration of environmental objectives in livestock and agricultural sectorial policies, and the selection of the best manure management technological packages according to local objectives and constraints.

References

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Goreau T J 1994 Coral Reefs, Sewage, and Water Quality Standards. http://globalcoral.org/CORAL%20REEFS.%20SEWAGE,%20AND%20WATER%20QUALITY%20STANDARDS.htm

Natural Resource Defense Council 2001 Facts about Pollution from Livestock Farms. http://www.nrdc.org/water/pollution/ffarms.asp

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Sustainable Agri-Food Production and Consumption Forum 2002 Sectors: Livestock Farms . Environmental Pollution Caused by Livestock Manure http://www.agrifood-forum.net/home.asp

Vo Thi Kim Thanh 2001 Survey on urban and rural livestock systems in central Vietnam. MSc Thesis. Swedish University of Agricultural Sciences, Department of Animal Nutrition and Management, Uppsala, Sweden.