sign in sign up
<<
Home , Plant breeding, Weed control

MANAGEMENT FOR SUSTAINABLE IN KOREA

Sun-Ho Yoo and Yeong-Sang Jung*

College of Agriculture and Life Science Seoul National University, Suwon, Korea

*College of Agricultural Sciences Kangwon National University Chunchun, Korea

ABSTRACT

This paper discusses the effect on Korea's of modern farming practices, particularly heavy applications of chemical . It outlines the problems which are beginning to be- come serious, and suggests ways in which the situation might be improved. Soil management practices for are discussed, and some suggestions are made on the focus of future research.

INTRODUCTION applied to soils can provide with specific ingredient elements, but not with all the essential Over the last three decades, Korea has elements they need. The other essential for experienced dramatic changes in practices as a growth must be supplied from other sources, result of government-supported programs for the that is, from the soil. Crops can not take up all the development and dissemination of improved agricul- nutrients added as . Thus, farming practices tural technology. The aim of this program was to which use heavy applications of chemical fertilizer achieve self-sufficiency in staple and to in- may cause some elements in the soil to be depleted crease farm incomes. Since the 1960s, Korean and others to be deposited in excess, resulting in a agriculture has done a tremendous job of producing worsening of the soil’s balance and reduced enough for self-sufficiency, and providing con- soil productivity. Some of the surplus chemicals may sumers with of high quality at a reasonable degrade the soil ecosystem and act as pollutants. price. Nowadays, Korean farmers rely more on “Sustainable agriculture” is a topic which chemical fertilizers and than on the tradi- has received considerable attention in recent years tional renewable resources drawn from the farm from environmentalists, agriculturalists, and con- itself. As in other industrialized countries, the pat- sumers. Sustainable agriculture has been given a tern of modern agriculture in Korea has aroused number of different definitions, but the term implies public concern over environmental problems such as three basic values: sustainable agriculture is ecologi- contamination of water by agricultural chemicals, cally sound, economically viable, and socially just residues in food, growing resistance to and humane (Aiken 1983, Dahlberg 1986, Keeny pesticides among and pests, loss of genetic 1990, O’Connell 1991). diversity, loss of natural soil productivity, and aggra- In Korea, sustainable agriculture has re- vated . ceived little attention, mainly because farming has The increased inputs of modern agriculture been focussed on maximizing . It was not until are largely of artificial origin, and may have a nega- 1990 that the term “sustainable agriculture” was tive impact on the environment. Chemical fertilizer publicly discussed for the first time in Korea, in a

Keywords: Soils, Korea, erosion, fertilizer, organic matter, soil management, sustainable agriculture. 1 paper presented at a major national symposium (Yoo Farmers began to make widespread use of agricul- 1990). The senior author (Yoo 1991) in the follow- tural chemicals, as fertilizers and for manage- ing year stressed again the concept of sustainable ment and control. In the 1970s, high yielding agriculture at the Symposium on Conservation of the rice varieties bred by crossing Japonica and Indica Agricultural Environment, held in 1991 by the Ko- types were disseminated throughout Korea, and as a rean Society of Environmental Agriculture. result average rice yields soared to 4.5 mt/ha. Small- In terms of , the scale farmers began to mechanize their farm opera- major components of sustainable agriculture are tions, and heavy inputs of chemical fertilizers and cultural practices and , soil and water pesticides became common. By the mid 1970s, self management, pest and , and integrated sufficiency in rice, the staple , was achieved, and plant-animal production and nutrient cycling. Soil is Korea even recorded a surplus in rice production the key natural resource in agricultural production. during the 1980s. This paper discusses current problems of Korean The recommended levels of fertilizer for soils associated with agricultural productivity, and a different crops were based on a large number of field soil management strategy for sustainable agricul- trials, in which the application rate which gave the ture. maximum yield was taken as the optimum level. In Table 2 we can compare the total amount of fertiliz- Changes in Soil Management in Korean ers recommended by the Rural Development Admin- Agriculture istration (RDA) with the actual fertilizer consump- tion by farmers. There is little difference in the Until the 1920s, Korean farmers made little amounts of and potassium recommended use of chemical fertilizer. The consumption of and those purchased, but the amount of chemical fertilizer in 1925 was only 21,000 mt, so fertilizer purchased by farmers exceeded the recom- farming had to depend mainly on natural soil fertility mended amount by more than 90%. It is clear that and organic . However at this time, rice too much nitrogen fertilizer is being applied. yields from paddy fields were less than 1.5 mt/ha. By At present, farming in Korea uses high 1937, 570,000 mt of chemical fertilizer were being inputs of fertilizers, chemicals and machinery. These applied, and average national rice yields had in- high inputs mainly originate from petrochemical creased to 2 mt/ha. The recommended application energy, which is nonrenewable. A comparison of rates for chemical fertilizers at this time were 26 kg/ inputs, in terms of energy demand, of conventional ha of nitrogen, 34 kg/ha of phosphorus and 39 kg/ha and highly mechanized rice production, is shown in of potassium (Table 1). By the early 1960’s, Korea Table 3. Tillers with a capacity of 8 HP are com- still suffered from a food deficit, and the government monly used for plowing in conventional farming, began a program to boost agricultural production. while heavy machinery such as large tractors for

Table 1. Recommended application rate of fertilizers for paddy rice

2 plowing, transplanters, power threshers and power Table 3 is based on Pimentel and Pimentel (1986), sprayers, are used in the highly mechanized farm and is only a rough approximation, but we can note operations. The energy input calculation shown in that the energy input for nitrogen fertilizer alone is

Table 2. Comparison of the amounts of fertilizer recommended and applied, Korea 1990

Table 3. Comparison of energy input and output for production in a 0.1 ha farmed by conventional and highly mechanized techniques

3 one third of the total energy input. The use of content was 3.3% between 1936 and 1946, at a time manure in integrated crop livestock farm- when soil fertility was still being maintained with ing can reduce the relative energy input from nitro- organic manure. In the 1960’s, the organic matter gen to one-fifth of the total. content of the soil fell to 2.6%, and simultaneously the average pH rose and the potassium and SOIL FERTILITY STATUS AND SOIL MANAGE- content also increased. This marks the period at MENT PROBLEMS which chemical fertilizers came into widespread use as began. Soil Nutrient Balance As Table 5 shows the phosphorus content in upland soils used for grain crops and is Since one of the principal constraints to more than double the recommended level. In green- plant growth is a deficit of available nutrients in the house soils where vegetables are intensively grown, soil, farmers tend to use more fertilizers to get higher phosphorus exceeds the recommended level by ten yields. In a natural ecosystem, the 16 elements times. Data on the levels of base saturation show that essential for plant growth are kept in balance, the these soils were already saturated with amounts of required by the matched by those bases by 1989. supplied naturally by the soil, including nutrient An excessive use of chemical fertilizers recycling. Agricultural practices, however, have certainly causes economic loss to the farmer, and changed this balance, and fewer nutrients are being gives rise to salt accumulation which may bring recycled as the harvested plant parts are removed about a deterioration in the soil environment (Yoo et from the field. The result is a loss of soil productiv- al. 1974). ity. The water-soluble and mobile constituents The Rural Development Administration has in the soil may be leached out of the root zone, or carried out a large-scale soil testing program since it removed in runoff to pollute the water system. The was established in 1962. Under this program, an nutrients most closely associated with water pollu- enormous number of soil samples have been ana- tion are inorganic nitrogen and phosphorus from lyzed. Table 4 shows a summary of the results of the agricultural land. Fig. 1 and Fig. 2 show the seasonal tests of paddy soils. Most soils in Korea have a low changes in the nitrate and phosphate concentrations pH and organic matter content, and a low level of in water used for . phosphorus (P) potassium (K) and Calcium (Ca). It is clear that even the percolated water There has been a steady decline in the organic matter contains a high concentration of both N and P. This and magnesium content since 1936, while the phos- means that a considerable amount of applied fertil- phorus content has increased. The organic matter izer is being leached out of the root zone (Cho et al. 1989).

Table 4. Changes in the chemical properties of paddy soils, 1936­1988

4 Table 5.Table Changes in the chemical properties of upland soils

5 Fig. 1. Nitrate levels in water in reservoirs and paddy fields, Korea

Source: Kim et al. (1989)

Fig. 2. Phosphate levels in water in reservoirs and paddy fields, Korea

Source: Kim et al. (1989)

6 Yoon and Yoo (in Yoo 1991) analyzed to 1982, using different cropping systems, ranged nitrate levels in the soil profile after nitrogen fertil- from 0.1 mt/ha year from the plot planted in grass to izer in the form of urea had been applied to grassland. 226 mt/ha year from the clean tilled plot (Table 6). The nitrogen application rate was 140 kg/ha. Al- A large amount of nutrients can be lost from though this rate was only one-half of the recom- surface soil as the topsoil erodes. Measurements in mended level, a large amount of nitrate moved down a corn field found that 15.5 kg of nitrogen and 10 kg into the subsoil (Fig. 3). The nitrate concentration of phosphorus were washed away by runoff water (as measured by a lysimeter) in the leachate under with topsoil when 21.5 mt of topsoil were eroded in fallow conditions was much higher than when the a year (Table 7). If the loss of fixed forms of these field was under grass (Fig. 4). The results clearly elements in the soil particles and organic matter lost showed that large amounts of nitrate could leach out were included, this amount would be even higher. of the root zone, particularly if the soil had no crop For example, a fertile soil contains 2 - 4 kg of cover, to become a potential pollutant of groundwa- nitrogen in one metric ton of soil. Therefore, the ter. 21.5 mt of eroded soil particles might remove 43 to 86 kg of nitrogen, which corresponds to half the Erosion amount applied in the form of chemical fertilizer in one year. No-tillage reduced soil losses by 62% and Using the USLE formula, Jung (1976) esti- nutrient losses by 32%. mated that potential soil loss from erosion from In traditional farming, most animal wastes steep slopeland (22.5% slope) could be as high as were returned to cropland as fertilizer. One cow 485 mt/ha year, but suggested that this could be produces about 30 kg of wastes every day, while a reduced to less than 13 mt/ha year with proper soil pig produces 6 kg. The total annual production of conservation measures. Jung et al. (1985) con- animal wastes in Korea is estimated to be 37 million ducted a 2 x 10m2 lysimeter study on a sandy loam mt (Table 8). This is enough to cover Korea’s whole soil with 20% of slope. Measured soil loss from 1977 area of agricultural land at a rate of 16.9 mt/ha, and

Fig. 3. Seasonal changes in mineral nitrogen in grassland soil

Source: Yoo (1991) 7 Fig. 4. Changes in nitrate N concentration in leachate (Yoo 1991)

Table 6. Soil loss from a sandy loam with Table 7. Nutrient losses from corn field, 20% slope under different 1979­80 cropping systems, 1977 to 1982

Source: Jung et al. 1985

Source: RDA 1989

could substitute for 44% of the nitrogen which was thousand ha. However most livestock wastes are not applied in the form of chemical fertilizer in 1990, as used for agriculture, but are discharged into streams well as 67% of the phosphorus, and 70% of the and rivers. The efficient recycling of animal wastes potassium. If we assume that the maximum rate at in Korea is one of the most urgent problems in order which animal wastes should be applied is 50 mt/ha, to protect water quality. the amount produced in Korea would cover 750

8 Table 8. Annual production of livestock wastes in Korea

SOIL MANAGEMENT FOR may result in a build-up of dangerous residues. For SUSTAINABLE AGRICULTURE example, fused phophate and silicate fertilizers may contain heavy metals such as copper, cadmium or Maintaining Soil Quality even uranium. Although these do not appear to be serious soil contaminants at present, there should be Improving soil quality for better plant careful long-term monitoring of the mass balance growth has long been a primary objective of soil and behavior of these elements. The mass balance of science, but many problems of soil quality remain. carbon, water, and the many gases involved in agri- Loss of soil quality can result from the mismanage- culture and the wider ecosystem, also deserve more ment of soil resources, in the absence of information attention. For example, the methane and nitrous on how to manage it properly. A soil management oxide produced in agricultural production will affect strategy for sustainable agriculture must be based on air quality in the same way as those produced by the maintaining soil quality in the long term (Table 9). industrial sector. Soil properties have changed as a result of intensive cropping, , and the heavy use Use of Organic Matter of agrochemicals. The present recommended rates for fertilizers in Korea were set when soil fertility The maintenance of soil organic matter has was rather low, so it is not appropriate to apply these been a key point in soil management for generations. to the soils of today or in the future. The accumula- Organic matter is the principal reservoir of nitrogen tion of some nutrient elements in soil is already and other nutrients. It increases the soil buffering evident, and it is time to re-evaluate soil fertility. capacity, helps maintain a good soil texture and Nitrogen is the most important plant nutri- protect soil from erosion, and maintains a healthy ent. Plants absorb nitrogen at different rates, accord- community of soil microorganisms (Cho 1986). ing to their growth stages. If there is an excess of soil Although organic matter should not be considered a nitrogen, the surplus will be lost by denitrification panacea in modern agriculture, the maintenance of a and/or by leaching. A correct assessment of the high soil organic matter content is always desirable, amount of available nitrogen, based on soil testing, is and appropriate management of the soil organic therefore highly desirable. matter is critical in achieving profitable, sustainable The composition of complex commercial and environmentally friendly agriculture (Hoeft and fertilizers should be reexamined and adjusted. The Nafziger 1988, Darst and Murphy 1989). Crop repeated use of chemical fertilizers which contain residues should be returned to the soil where they are exactly the same constituents will accelerate the cut, possibly after composting. Mechanization will accumulation of unused elements. aid in the transport of heavy, bulky organic materials A long-term dependence on chemical fertil- such as rice . It must be emphasized that izers for macro nutrients may possibly result in the modern does not represent a retreat depletion of , leading to hidden prob- to the past, but is an improved agricultural system. lems of deficiency. It is necessary to More research on the role of organic farming is pay more attention to micro elements. required if we are to reduce the level of inputs needed The excessive use of chemical fertilizers to maintain the agricultural ecosystem. Selection of

9 Table 9. Soil management problems and research needs for sustainable agriculture

proper crops and cropping systems will minimize Use of Livestock Wastes nutrient losses while increasing the level of soil organic matter. The use of animal wastes from livestock farming is desirable, but at present in Korea there are Reduced Tillage various difficulties in doing this. The few larger livestock tend to be located near urban areas, Conservation tillage is a form of low-input or in hilly areas far from the croplands where the agriculture, in that it requires a lower input of energy organic resources are needed. More than two-thirds and labor, and minimizes disturbance to the soil. of Korea’s livestock farms are rather small, and However, whether reduced tillage gives good results farmers tend to stock them at a very high density in partly depends on the soil type. It is not suited to order to reduce capital input and management costs. poorly drained soils, or soils compacted by heavy These small farms generally dispose of animal wastes machinery. Reduced or no-tillage may also need without giving them any pretreatment. The Ministry heavier applications of to control . of the Environment does regulate the disposal of The process of tilling the soil rapidly incorporates animal wastes by law (Kim 1991), and requires organic materials into the soil matrix, while no- livestock farms to have a treatment system for animal tillage leaves organic materials undisturbed and strati- wastes, but these regulations apply only to large fied in the topsoil. Runoff water, drying and wetting, farms. Treatment systems suitable for small farms and freezing and thawing, will have different effects should be developed, and farmers provided with the on soil properties and soil microorganisms (Stinner necessary financial assistance to install them. Effi- and House 1989). The advantages and disadvan- cient waste management would not only cut down on tages of no-tillage should be examined according to pollution, but provide crop farmers with a useful the particular local situation. source of cheap organic fertilizers.

10 Protection of Non-cultivated Land A large amount of organic materials from livestock farms is being discharged untreated into The area of uncultivated marginal land in water courses rather than applied to agricultural rural areas is increasing. These uncultivated land. At present it is not practical for small-scale slopelands are highly susceptible to erosion if left increase livestock farmers to treat their farm wastes without a good vegetation cover. Proper measures and convert them into organic fertilizer. Not only to control soil erosion in such areas should be technological support is needed for such farmers, but developed and put into practice. also some financial support to subsidize the cost of treatment facilities. The advantages and disadvan- CONCLUSION tages of conservation tillage and low-input agricul- ture should be carefully and systematically tested in Over the past three decades, modern agri- a range of sites, so as to develop the best combina- cultural technology in Korea has been very success- tions of current and traditional farm practices and ful in increasing productivity. Nowadays, however, modern technology. we are faced with difficult environmental problems that arise, not only from industrialization, but from agriculture itself. Agricultural are urgently REFERENCES required to provide economically and socially ac- ceptable alternatives to help solve these problems. Aiken, W. 1983. The Goal of Agriculture. Sustainable agriculture may be defined as In: Agriculture, Change, and Val- an agricultural system which gives farmers a profit- ues, R. Haynes and R. Lamer (eds.). able livelihood while conserving agricultural re- Vol. I.. Cransville University, USA, pp. sources and environmental quality. It makes effi- 29-54. cient use of resources produced on the farm, reduc- Cho, S.J., C.S. Park and D.E. Eom. 1986. ing the need for commercially produced inputs. Soil Science. (3rd Edition). Hyangmun- Good soil management is a core component. Sa, Seoul. 396 pp. (In Korean). Soil testing should be the first step in man- Cho, J.K., K.H. Han and J.S. Kwon. 1989. aging soil for sustainable agriculture, so we can Evaluation of Agriculture on Water Qual- know what the problems are now, and what prob- ity. '89 Res. Rept. Chem. Dept. ASI, lems are likely to arise in the future. Soil testing over RDA. Korea: 5-13. the past 30 years has shown that most soils in Korea Dahlberg, K.A. 1986. New Directions for are acidic, and have a low organic matter content and Agriculture and Agricultural Research. too low a level of many available nutrients for good Rowman & Allenheld Pub., USA: pp436. plant growth. Continuous applications of chemical Darst, B.C. and L.S. Murphy. 1989. Soil fertilizer containing the major nutrient elements have organic matter: An integral ingredient in resulted in both the accumulation of unused con- crop production. Better Crops 74, 1: 4- stituents, and the hidden depletion of minor ele- 5. ments. Excessive use of chemical fertilizers has Hilderbrand, P.E. 1990. ’s role in become a cause of environmental pollution, and is sustainable agriculture: Integrated farming partly a result of the fact that the present recom- systems. Jour. Prod. Agr. 3: 285-288. mended levels of fertilizers were determined at a time Hoeft, R.G. and E.D. Nafziger. 1988. Sus- when soil fertility was quite different from what it is tainable agriculture. Better Crops 72, 2: now. A reexamination of both soil fertility and how 9-11. this is measured would be a useful preparation for Jung, Y.S., J.S. Shin and Y.H. Shin. 1976. more efficient fertilizer management. The recycling Erodibility of soils of Korea. Jour. Ko- of nutrient and chemical components on agricultural rean. Soc. Soil Fert. 9: 109-115. land should be evaluated. Jung, P.K., M.H. Ko and K.T. Um. 1985. Large amounts of Korea’s fertile surface Discussion of cropping management fac- soils are being lost as a result of erosion. In recent tors for estimating soil loss. Jour. Kor. years the area of fallow land has been increasing, as Soc. Soil Fert. 18: 7-13. farmers leave for the cities, and these abandoned Kim, S.P. 1991. Counter-plan for conserva- fields are very vulnerable to erosion. Proper man- tion of the agricultural environment. Pro- agement practices and measures to control soil ero- ceedings of the Symposium on Conserva- sion are necessary. tion of Agriculture. Korean Soc. Env.

11 Agr, pp. 191-212. Suweon, Korea. Kim, K.S., B.Y. Kim, J.G. Yoon and K.H. Parr, J.F., R.I. Rapendick, I.G. Yangberg and Han. 1989. Survey on water quality of R.E. Meyer. 1990. Sustainable Agricul- irrigation water in water systems through- ture in the . In: Sustainable out the country. Research Report, 1989. Agricultural Systems, C.A. Edwards et al. Institute, Korea, pp. (eds.). Soil Cons. Soc. Ankeny, Iowa, 13-28. USA. Keeny. D. 1990. Sustainable agriculture: Pimentel, D.S. 1986. Energy and other definition and concepts. Jour. Prod. Agr. natural resources used by agricuture and 3: 281-285. society. In: New Directions for Agricul- Läuchli, A. 1987. Soil science in the next ture and Agricultural Research, K. twenty-five years: Does play Dahlberg (ed.). Rowman & Allanheld, a role? Soil Sci. Soc. Am. Jour. 51: USA: pp. 259-287. 1495-1509. RDA. 1985. Soils of Korea and their im- Lee, C.H., S.G. Cheon, W.K. Shin and H.S. provement. ASI, RDA, Suwon, Korea: Ha. 1990. Effects of silica and pp 71. application on the availability of accumu- RDA. 1989. The Report on the 10-Year lated phosphate in paddy and upland soils. Soil Amendment Project in Korea, J.H. Jour. Kor. Soc. Soil Fert. 23: 281-286. Han, (ed.). Rural Development Adminis- McCracken, R.J. 1987. Soils, soil scientists, tration (RDA), Korea, p. 508. and civilization. Soil. Sci. Soc. Am. Jour. Reganold, J.P., R.I. Pandedick and J.F. Parr. 51: 1395-1400. 1990. Sustainable Agricultural Systems. Menzel, R.G. 1991. Soil science: The envi- Soil and Water Conservation Society, ronmental challenge. Soil Sci. 151: 24- Ankeny, Iowa, USA. 29. Simonson, R.W. 1991. Soil science – Goals FAO/MA, The Netherlands. 1991. Sustain- for the next 75 years. Soil Sci. 151: able Agriculture and Rural Development 7-18. in Asia and the Pacific. Regional Docu- Smith, R.M. and W.L. Stamey. 1965. De- ment No. 2, S-Hertogenbosh, The Nether- termining the range of tolerable erosion. lands. 24 pp. Soil Sci. 100: 414-424. FAO/MA, The Netherlands. 1991. The Den Stinner, B. and G.J. House. 1989. The Bosh Declaration and Agenda for Action search for sustainable agroecosystems. on Sustainable Agriculture and Rural De- Jour. Soil and Water Cons. 44: 111-116. velopment. Report of the Conference on Tinker, P.B. 1985. Soil in a changing Sustainable Agriculture and Rural Devel- world. J. Soil Sci. 36: 1-8. opment. 13 pp. Yoo, S.H. 1990. Present status and Pros- O’Connell, P. Sustainable agriculture. In: Ag- pect on Soil Pollution in Korea. The riculture and the Environment, 1991 21st Century Committee Report. Seoul Yearbook. U.S. Printing Office, pp. 175- National Univ. Korea, p. 41. 185. Yoo, S.H. 1991. Soil management for sus- Oelhaf, R.C. 1978. Organic Agriculture: tainable agriculture: In: Proceedings of a Economic and Ecological Comparisons Symposium on Conservation of Agricul- with Conventional Methods. Montclair, ture, Korean Society Env. Agr., Korea, New Jersey, USA. pp. 79-95. Park, Y.D. 1991. The present situation of Yoo, S.H., Y.S. Jung and Y.H. Shin. 1974. using nitrogen fertilizer and its effects on Deterioration of the physical and chemical upland crops in Korea. Paper delivered properties of vinyl house soils by continu- at the International Seminar on Increasing ous cropping. J. Kor. Soc. Soil Nitrogen Efficiency in Upland Crop Pro- Fert. 7: 227-234. duction, June 23-30, 1991. RDA,

12 DISCUSSION

Dr. Hsieh was interested in the marked increase of nitrate leaching in Korea over recent years, and asked whether Korea shared Taiwan’s problem of a high nitrate level in some crops, especially vegetables. Dr. Yoo agreed that there was some evidence of this, especially in vegetable crops, although the problem was probably not as serious in the cooler climate of Korea.

Dr. Umali, referring to Dr. Yoo’s report of fertilizer losses in the field and his data that only 35% of applied potassium was absorbed by the crop, asked whether losses were reduced if the soil had a high organic matter content, so that there was e.g. less leaching or more absorption by the plant. Dr. Yoo thought it was likely that organic matter had both these effects, and pointed out that since 1960 in Korea, an increasing level of nitrogen fertilizer had been applied while the organic matter content of the soil had decreased. This had meant a fall in the CEC, so that the rate of absorption was also reduced. Most farmers in Korea were not able to get as much organic matter for their farms as they would like: livestock and crops were produced in different areas, which made recycling difficult. However, if farmers were able to apply as much organic matter as they needed, they would be able to improve the absorption capacity of the soil.

Dr. Reganold commented that one problem in using organic matter with chemical pesticides is that leaching studies of pesticide residues had found that leaching of pesticides is less when organic matter is applied, and there is also greater absorption of pesticides by the plant. Not only the presence of organic matter affects the rates at which pesticides are leached or absorped, but even the type of organic material applied.

13