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Low-Input Sustainable Agriculture Production Systems WILLIAM C. LIEBHARDT University of California, Davis During the last five to ten years terms such as sustainable have been used to describe agriculture. Other agricultural terms include regenerative, low-input, ecological, biological, environmentally sound, resource-efficient, and the long-used term organic. This last term is generally used to define production systems which either do not use synthetic pesticides and fertilizers or which seek to reduce their use substantially. These terms and practices have come into use because many farmers, scientists, and policymakers have realized that many current agricultural practices are not sustainable due to economic, environmental, biological, chemical, and human problems related to contemporary agricultural systems. Agriculture as practiced today is a broad continuum ranging from pure organic farming to the use of hydroponics in an almost totally synthetic system. These two views of agriculture represent different philosophies of production. In hydroponics, almost every- thing is brought through the farm gate, and external inputs are maximized. Sustainable systems tend to minimize the use of exter- nal inputs and maximize internal inputs which already exist on the farm. One system tends to dominate or override nature whereas the other tries to use natural processes to the maximum possible extent. Most farmers work somewhere between these two types of production systems. As chemical inputs have become more numerous during the last 50 years, farmers have moved to use these materials to aid in the production of food and fiber. Now, however, the use of chemicals 80
81 is increasingly being questioned. Information drawing comparisons between production systems is still relatively scanty; however, such information was almost nonexistent ten years ago. The information comes from whole farm comparisons, replicated experiments, and side-by-side field comparisons. These comparisons and experiments cover broad classes of farms, farming systems, soils and environmen- tal conditions, and experimental and analytical procedures. Many of these are case studies and, therefore, can be viewed as indicative or suggestive but not definitive. FARM LEVEL COMPARISONS Conventional agriculture can be characterized by the use of sub- stantial quantities of fertilizers, pesticides, petrochemicals, and other capital inputs in order to maximize production of food and fiber. Conventional agriculture reduces the effective boundaries of a pro- duction system to a single crop in a single field in one season. Any production inputs needed to stabilize the system biologically, physi- cally, chemically, and economically are used. For the most part the system is structured by these inputs to conform to the needs of the single crop in order to achieve an optimum yield. Research on such systems tends to be discipline-oriented and deals with individual components. In contrast, sustainable systems are characterized as agriculture which maximizes the use of internal resources on the farm and con- sequently minimizes to the extent possible the use of external inputs. In sustainable agriculture the effective system boundary is usually extended to include an entire farm or management unit, its crop or animal enterprise mix, the crop rotation or sequence, and the flow of materials through the system over time. The terms reductionist versus wholistic have been used to describe the above differences in approach. However, these terms imply value judgments and must therefore be used with caution. All of the studies comparing conventional and sustainable sys- tems have the weakness of non-random sampling of farms, of vary- ing degrees of precision and completeness in data-gathering, and of the limited number of farms studied. The most extensive data are those from a comparison in the midwestern United States, while the most exact and complete single-farm data are those from east-central Pennsylvania. While such data may have weaknesses, it is important when selecting sustainable farms for study to sample from a very
82 small percentage of total farms, since farms differ in structure, size, farm management capabilities, proximity to market, and physical environment. The studies, for the most part, have addressed such differences very well. The first significant study in the late 1970s analyzed the corn yields of 26 comparably-paired sustainable and conventional mixed- grain livestock farms in the western corn belt over a wide range of soil types. The mean yield of corn (Zea mays L.) from the conventional fields was 8.5 percent higher than from the matched sustainable fields, but this difference was not statistically significant. While conventional corn yields tended to be higher than sustainable corn yields under favorable growing conditions, conventional corn yields were lower when conditions were adverse due to drought. Grain from conventional fields had a significantly higher crude protein content, stalk rot (Diplodia), and lodging. Soils from sustainable fields had a significantly higher organic carbon content, higher total nitrogen, but lower Bray 1 phosphorus. Differences in Bray 2 phosphorus, exchangeable potassium, carbon/nitrogen ratio, cation exchange ca- pacity, and pH were not significant. The sustainable farms required about two-fifths as much fossil energy to produce a given value of crop. This work showed that elimination of conventional fertilizers and pesticides does not automatically result in drastic consequences. It also suggested that considerable reduction in chemical use was realistically possible on mixed-grain livestock farms of the western cornbelt. A further systems comparison in the eastern United States compared conventional with sustainable corn and wheat (Triticurn aesitivum L.) production and found that sustainable corn and wheat systems were 29-70 percent and 35-47 percent more energy efficient, respectively, than conventional systems. The long-term sustainability of low-input farms is very apparent in research on complete farms. Results were recently reported from a five-year study (1978-1982) of a 130-hectare crop/livestock farm in eastern Pennsylvania which had primarily used low-input, biological resources since 1973. Crop yields were 10 percent above state and county averages, soil fertility levels were maintained or increased, erosion was reduced, and production costs were 10 percent less than a simulated conventional, high-input farm. Inclusion of forage legumes can be a problem for cash grain farmers because it could reduce their income or result in the production of a crop which is more difficult to dispose of.
83 The 1980 summary report prepared for the U.S. Congress on sustainable agriculture states the conclusions which have been drawn from all of these studies. These conclusions are: ⢠Yields per acre are generally equivalent or slightly less than those of conventional agriculture; however, some farms have significantly higher than average yields. ⢠Few or no insecticides, fungicides, or herbicides are used. ⢠Production costs are lower by as much as 30 percent, and average about 12 percent lower. ⢠Energy inputs per unit produce are 50 to 63 percent less. ⢠A higher proportion of production cost is comprised of labor and machinery cost than on conventional farms. ⢠Soil erosion is significantly reduced. These studies are based on data derived exclusively from inte- grated crop/livestock or field crop farms. None are from vegetable or fruit operations. Also, the data are only suggestive because of limi- tations of the case study approach. However, taken as a whole, the studies lend sufficient credibility to the six conclusions listed above to warrant continued research on a farm-wide basis with a broad sam- pling of farms as well as on a controlled, field plot level. The striking results, if confirmed, could have substantial significance for a large proportion of U.S. farms growing similar crops. The environmental implications of reduced disruption from agriculture are also highly significant. There is growing evidenceâalthough some is very circumstan- tialâof efficiencies of nutrient flow in sustainably managed systems that are quantitatively different from those in conventional systems. A study of two cash crop farms in the Palouse region of eastern Wash- ington stateâone using sustainable methods and the other conven- tional methodsâshows similar results. These side-by-side farms were compared for two years with respect to yield and soil characteristics. The sustainable farm had not received fertilizer nutrient input since 1909. It used a winter wheat/spring pea (Pisum satuvum L.)/Austrian winter pea (Pisum sativum, pp, arvense (L) Poir)/green manure or summer fallow rotation. The conventional farm was under a winter wheat/spring pea rotation in which commercial nitrogen and phosphorus fertilizers were used. Soil test data showed increasing levels for organic matter, extractable phosphorus, and potassium for the sustainable farm when compared to the conventional farm. This suggests an upward flow and accumulation of soil nutrients
84 in the upper part of the soil horizon which is similar to natural soil-building processes. The downward movement and leaching of chemicals in the soil under conventional methods has had major implications of ground water contamination by excess nutrients. The higher levels of extractable phosphorus on the sustainable farm is interesting as it was the conventional farm which received application of the phosphorus fertilizer. Neither farm received potassium fertilizer; however, the sustain- able farm had almost double the amount of extractable potassium as compared to the conventional farm. Both farmers reported yields about equal to or greater than historic yields and local averages. Overall, the measured average yields of both farms were within one to two percent of each other (sum of two crops of wheat and one pea crop) when comparing sustainable and conventional fields. These yield comparisons, however, are difficult to make because they were in different fields on different, but adjacent, farms. Input costs were substantially less on the sustainable farm and the environmental im- pact was substantially reduced as a result of different inputs. Rill erosion on the conventional sampling sites was greater by a factor of 3.9, which indicates a significant difference in soil loss between the two systems. Average long-term changes calculated in soil nitrogen and phos- phorus pools resulted in substantial deficits of 44 and 14 kg/ha/yr, respectively, on the sustainable farm and 23 and 5 kg/ha/yr on the conventional farm. However, nutrient deficits were not reflected in lower soil nitrogen and phosphorus levels in the plot areas tested on the sustainable farm, indicating that reduced soil erosion and greater efficiency of nutrient cycling more than compensated for the outflow from crop harvest. These results indicate substantially more effi- cient nutrient use in sustainable systems. Investigators did not know where the nutrients came from in the sustainable system nor where they went in the conventional system, suggesting that there is much to be learned about these production systems, and underscoring the importance of a systems approach in future research. Contemporary agricultural systems typically rely on chemical inputs to maintain natural balance. To test the necessity of these inputs, Michigan workers during the 1980s studied paired sustainable and conventional farms which grew commercial onions. Control sites were set up which lacked both the chemical sprays of the conventional sites and the biological structuring of the sustainable sites; therefore, outputs fluctuated wildly.
85 The sustainable sites, while free of chemical inputs, contained a highly structured system of organisms which alone maintained a natural balance. Although the conventional sites were sprayed to decrease pest population levels, this artificial system was not as effective as the natural structure of the sustainable systems. Conven- tional farmers using repeated sprays of sevin, parathion, diazinon, and malathion experienced higher levels of onion fly for much of the season than did sustainable farmers. It has been reported that sustainable farms experienced fewer pest problems, but this is only preliminary evidence taken from a very pest-susceptible crop. This is an example of predator/prey and parasite/host relation- ships. Pesticides used in these systems have also caused secondary pest outbreaks. Much needs to be learned about these relationships, yet even the basic information is not available. Environments have been created which favor the development of resistance and decreased genetic diversity. REPLICATED RESEARCH COMPARISONS Research was recently reported comparing crop rotations and manure to agricultural chemicals in dryland grain production in Nebraska. A four-year crop rotation with manure was compared to corn monoculture with fertilizer, herbicides, and insecticides. The rotation also had herbicide and fertilizer treatment and fertilizer-only treatment. Corn yields for the rotational system were substantially higher than yields for the continuous corn system. Weeds were major deter- rents to corn and soybeans on the areas with no herbicides. Tillage with a disc was used for both corn and soybeans which creates con- ditions that favor weed problems, so it is not surprising to find that there is a problem when herbicides are not used. It may be neces- sary to change other practices when weed control is changed because soil management and particularly tillage greatly influences what is produced in terms of weed competition. When corn was under heat and drought stress, yields of corn grown in crop rotation with manure only were comparable to yields of corn grown in rotation with fertilizer plus herbicides, and were better than yields for continuous corn with fertilizer, herbicides, and insecticides. Under good growing conditions corn yields with herbicides, fertilizer, and insecticides were greater than corn yields in the rotation with manure.
86 In Pennsylvania on a mixed-crop/livestock farm, eleven repli- cated field studies in 1979 and 1980 on corn following alfalfa showed that supplemental nitrogen as ammonium nitrate or poultry manure did not increase grain yield. This shows that mixed-crop/livestock farms with legumes and manure have excellent potential for internal- ization of nitrogen production. Other work has shown that insertion of a legume into a row crop such as corn has potential to internalize nitrogen production. Research on overseeding of legumes into row crops during the growing season or soon after harvest in Delaware, Kentucky, New Jersey, North Carolina, Tennessee, and Maryland has shown that nitrogen in the above-ground biomass was 100 to 225 kg/ha and that yield potential was increased in addition to the nitrogen which was derived from the legumes. THE TRANSITION A major problem for farmers wanting to change their production practices from high inputs of chemicals to a system which uses less or none at all has been a lack of specific information on how to make such a change. Research was initiated in 1981 in Pennsylvania to determine procedures which a farmer could follow in making the transition. The research was initiated on land which had been in a cash grain sequence with fertilizer and pesticides for many years. A cash crop sequence with all contemporary agricultural chem- icals was compared to two low-input sustainable systemsâa cash grain system relying on legumes and an animal system with legumes and manure. Rotations were started at three points to determine the effect of crop sequence on the transition process. It was found that the conversion process was satisfactory when small grain, legume hay, or soybeans were the initial crops and corn did not enter the rotation until the third year. In a system where nitrogen and weeds were the limiting factors, a soybean/small-grain legume/corn rotation re- sulted in a satisfactory transition; corn in the first or second year was not satisfactory. Further work in 1986 with a low-input sustainable cash grain rotation showed that relay cropping of barley and soy- bean was superior to soybeans alone with herbicides. This work also showed that a diverse cash grain rotation utilizing corn, soybeans, small grain, and legume cover crops resulted in excellent internal weed control and nitrogen production. The low-input sustainable system had lower production costs and higher net return than the
87 conventional system, although the corn/soybean conventional rota- tion also had good nitrogen levels and weed control provided by fertilizers and herbicides. INSTITUTIONAL CHANGES Agriculture is an integrated system of knowledge and technolo- gies and should be dealt with accordingly. A more wholistic sys- tems approach to research is needed. Much needed information falls between departmental lines or subject matter areas. Reductionist research creates many undetected problems for the producer as well as the consumer. Reductionist approaches to research in the areas of soil fertility and pest control have led to nutrient runoff and leaching, resistant species of insects and weeds, environmental contamination, and unbalanced production systems with significant soil, health, and economic costs. Research is also necessary on the following topics: ⢠As animals have become more crowded, stress and disease are more prevalent; therefore, antibiotics are needed. Recent reports show that antibiotics in animal feeds have led to food animals which are a major source of anti-microbial-resistant salmonella infections in humans. ⢠New information indicates a relationship exists between fertilizer use and nitrate levels in well water and the incidence of some types of cancer in Nebraska. This shows why systems research from field to consumption is important. ⢠In the past (1950-1975) yield benefits of rotations were over- looked and almost forgotten as it appeared that fertilizers and biocides could substitute for a rotation. Evidence now shows that in spite of all management inputs a farmer might impose, there is still a yield advantage to be obtained from rotations. ⢠Tillage now has a major impact on the erosivity of soils. Conser- vation or reduced tillage is a relatively effective technique, but at present it is a pesticide-intensive system. Use of allelopathic crops, ridge tillage, and other cultural practices could result in crop management which is less dependent on these biocides. Agriculture is now in a major transition. In the future infor- mation will be the driving force regarding farming decisions. This information will make use of biological, chemical, physical, and envi- ronmental principles to develop production systems which are more efficient in the use of resources, which provide the producer with a
88 better net return, and which do not create health and environmental problems. REFERENCES Liebhardt, W.C., and R. Harwood. 1986. Organic farming: 1986 technology public policy and the changing structure of American agriculture. Office of Technology Assessment, Congress of the United States. Popendick, R.I., L.L. Boersma, D. Colocicco, C.A. Kraeile, P.B. Marsha, A.S. Newman, J.F. Parr, J.B. Swan, and I.G. Youngberg. 1980. Report and recommendations on organic farming. USDA, Science and Education Administration. Beltsville, Maryland. Proceedings of a symposium on sustainability of California agriculture. 1985. University of California, Davis.
