Source: CORNELL UNIVERSITY submitted to
HOMEOSTASIS AND DEGRADATION IN FRAGILE TROPICAL AGROECOSYSTEMS
Sponsoring Institution
State Agricultural Experiment Station
Project Status
TERMINATED
Funding Source
Reporting Frequency
Annual
Accession No.
0194094
Grant No.
(N/A)
Project No.
NYC-107356
Proposal No.
(N/A)
Multistate No.
(N/A)
Program Code
(N/A)
Project Start Date
Sep 1, 2002
Project End Date
Sep 30, 2009
Grant Year
(N/A)
Project Director
Pell, A. N.
Recipient Organization
CORNELL UNIVERSITY
(N/A)
ITHACA,NY 14853
Performing Department
CIIFAD-INTERNAT'L INST FOR FOOD, AGRIC & DEV
Non Technical Summary
Environmental degradation, especially loss of soil fertility, is reducing agricultural productivity and increasing poverty in many areas of Africa. This project will describe the interactions between smallholder farmers in Kenya with the agroecosystem on which they depend for a living to understand how environmental degradation and poverty are related.
Animal Health Component
40%
Research Effort Categories
Basic
60%
Applied
40%
Developmental
(N/A)
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
1020199107030%
1020199301030%
1024010107010%
2050199107010%
3070199107010%
6010199301010%
Goals / Objectives
Empirical research and system dynamics modeling will be used to study nutrient fluxes in fragile, tropical agroecosystems and the bi-directional interactions between the ecosystems and the people who depend on these lands for their livelihoods. Our focus will be on landscapes that are degraded or are at risk of degradation. Whether agroecosystems with growing human demands can continue to provide the ecosystem services needed by farming communities will be explored. The paradox of neighboring subsystems in which some seem to be homeostatic and others do not readily recover from human and natural shocks provides the opportunity to understand the central biophysical and socioeconomic processes that underpin agroecosystem functioning. Interactions in coupled systems may be studied best in well-established systems in which the people and the natural resources are at the margin, as is the case in much of the rural tropics. In these systems, small changes in the natural resource base may have big effects on the people living within the ecosystem, and modifications in human activities may significantly affect ecosystem functioning. When natural resources become degraded and agricultural productivity declines, people become trapped in poverty. Both the causes of the poverty traps and the responses of those who are ensnared in them will be an important focus of this proposal. When households lack access to capital to finance productive investments, they cannot make large, discrete (as opposed to small, continuous) investments in soil fertility that would lead to improvement in soil organic matter (SOM) levels and nutrient availability. Social and cultural factors also shape natural resource management decisions and affect the sustainability of local production systems. Knowledge of how social structures and culture affects environmental stewardship is necessary if we are to understand human responses to natural events. Given the importance of small-holder systems to poverty reduction and to conservation of global biodiversity, this is a model that matters. About 90% of the poorest people in sub-Saharan Africa, those in the bottom income quintile who earn less than one dollar a day, live in rural areas (30). They are primarily agriculturalists, but their land holdings are smaller than those of their parents because of population growth. Land pressures have forced abandonment of traditional fallow systems used to maintain soil fertility resulting in soil degradation, declines in crop productivity and more poverty. Without remediation, the logical option for the next generation is urban migration with its social and political costs. Our work will contribute to understanding the human and biophysical factors that underlie declines in agroecosystem function with the long-term goals of poverty alleviation and environmental protection. Our diverse research sites in Kenya are similar to those in other parts of Africa as well as to some in Asia and Latin America. Thus, our model will have relevance beyond the regions that we are studying.
Project Methods
To model tropical agroecosystems and their economies, a series of subsystem models (crop, livestock, soils and human) will be developed. Then, the subsystem models will be linked dynamically. Field research will be conducted at three locations in Kenya: Embu (subhumid, good market access), Siaya/Vihiga (subhumid, restricted market access) and upper Baringo (semi-arid, poor market access). These sites offer uncommon agroecological diversity and variation in market access and population density within a reasonably compact area without differences in government policy or macroeconomic and political conditions. We plan to build on rich biophysical and socioeconomic data from these sites collected by Cornell, the International Centre for Research in Agroforestry (ICRAF) and the Kenyan Agricultural Research Institute (KARI). These data sets on soil degradation, household decision making, and agricultural activities will enable us to initiate modeling exercises when data collection is still under way. We will model stylized household strategies in each site, emphasizing the switches in people's responses that occur as household circumstances, and crop and livestock productivity change, especially in response to changes in soil fertility. Soil fertility will be assessed by measuring SOM including fractionation into labile and stable pools, N, P and K contents, and soil biological activity using phospholipid fatty acid and terminal restriction length polymorphism analyses. Carbon fluxes through the soil, plant and animal pools will be modeled to predict changes in SOM, plant biomass and animal production. The effects of land use management on C sequestration will be evaluated. By including information on the activity and diversity of the soil biota with data on the size of the labile and stable organic matter pools, our predictions of the extent of soil degradation will be more robust than those based on nutrient balances alone. Other models have described nutrient fluxes and ecosystem functions, but few have attempted to model feedback mechanisms between the social and biological components of agroecosystems. In contrast, the major goal of this project is to develop a model of coupled human and biological processes subject to nonlinearities, time lags, feed back loops and uncertainty. This model will be used to assess the reversibility of soil degradation and more generally the sustainability of agroecosystems subject to forces such as population growth.

Progress 10/01/06 to 09/30/07

Outputs
OUTPUTS: Our goal is to explore the relationships between environmental degradation and poverty in the Kenyan highlands on smallholder farming systems in two sites, Embu in Eastern Province and the Madzuu in Vihiga District. Crop and livestock productivity have been declining because of decreasing soil fertility. Our examination of the farming systems considers four components: humans, soils, crops, and livestock. Household-level questionnaires on socio-economic status were administered to farmers in both locations (116 in Embu,123 in Madzuu and 260 on the soil chronosequences) to establish farmers' economic status to enable us to determine whether and how farmers escape from or are trapped in poverty. With these data, we investigated how livelihood strategies, social networks, farmer group participation and institutional partnerships influenced poverty affected poverty dynamics. Soil samples were collected from plots of farmers in the socio-economic surveys. Although the soils from Madzuu differed from those in Embu in nutrient and organic matter content, there was little variation within location. The land in Madzuu had been cultivated for more than 70 years so soil degradation was extensive. Reliance only on data from Madzuu and Embu could not provide us with the data needed to understand the dynamics of soil degradation so we identified chronosequences based on time of conversion from forest to agriculture. Three soil chronosequences with 6 to 8 time points each were identified. The chronosequences have been used to determine the rate and nature of soil degradation, the dynamics of repletion of degraded soils through addition of inorganic and organic soil amendments and whether the quality of organic matter applied affects repletion. The rate of decrease of the stocks of C and nutrients in soils after conversion from forest occurred rapidly during the first 15-25 years of continuous cultivation. After the initial period of rapid degradation, equilibrium was reached with little change in soil organic matter or nutrient levels. Those farmers whose land has recently (<25 years) been converted to agriculture should consider adding organic matter and nutrients before declines in crop yields are evident. This is particularly important because the Kenyan government has sharply restricted the conversion of forest to agricultural use. Without appropriate soil management, yields and the incomes of smallholder farmers will continue to decline. Addition of organic matter has been postulated to improve soil fertility by several mechanisms. A second major effort of our project has been to develop a model using system dynamics to describe the complex interactions between farmers and their natural resource bases. The structure of the Crops, Livestock and Soils in Smallholder Economic Systems (CLASSES) model includes three integrated submodules. Model evaluation activities are largely complete. The model was tested to determine its ability to generate behaviors observed in available data for soil nutrient depletion and for the emergence and persistence of poverty traps. In general, these tests indicate that the model is quite adequate for its stated purpose. PARTICIPANTS: Amudavi, D., Brown, D.R., Hogset, H., Kimetu, J.M., Kinyangi, J.M., Liang, B., Marenya, P.P., Mude, A.G. and Stephens, E.C. all are or have been graduate students and/or post-doctoral fellows at Cornell. Kroma, M.M., Thies, J.E., and Solomon, D. are Cornell faculty or staff. The rest of the co-authors are from multiple institutions. Partner organizations: World Agroforestry Centre, Nairobi, Kenya and Kenyan Agricultural Research Institute, Nairobi, Kenya. TARGET AUDIENCES: Our target audience continues to be policy-makers, those interested in international development, international non-governmental organizations and smallholder farmers.

Impacts
The rate of decrease of the stocks of C and nutrients in soils after conversion from native tropical forest occurred rapidly during the first 15-25 years of continuous cultivation. After the initial period of rapid degradation, equilibrium was reached with little change in soil organic matter or nutrient levels. There are important practical applications these findings. Those farmers whose land has recently (<25 years) been converted to agriculture should consider adding organic matter and nutrients before declines in crop yields are evident. This is particularly important because the Kenyan government has sharply restricted the conversion of forest to agricultural use. Without appropriate soil management, yields and the incomes of smallholder farmers will continue to decline. Addition of organic matter has been postulated to improve soil fertility by several mechanisms. Most of the beneficial effects of adding organic matter over a 2-year period were related to release of nutrients resulting in subsequent improved crop nutrition. The added organic matter was most effective in the most degraded sites. The short duration of the experiment precluded drawing conclusions on the effects of the quality of organic matter on long-term soil restoration. When farmers' fertilizer application rates were compared with soil organic carbon (SOC) levels, farmers concentrated their fertilizer applications on more fertile soils. The relationship between daily per capita income and SOC was stepwise with a low equilibrium when soil organic carbon levels were less than 3%, a rapid increase between 3 and 4% SOC with a higher equilibrium over 4%. Because we linked soil science and economic data, we have been able to address an issue that has been of concern to economists, soil scientists and development practitioners to explain the low use of fertilizer by smallholder farmers. Those who recommend fertilizer as a means to address soil degradation are correct that it can increase nutrient availability, but the response is non-linear. Fertilizer is beneficial for degraded land but only if it is applied at rates in excess of what poor farmers typically land can afford. Several large foundations now are involved in extensive agricultural development projects trying to restore soil fertility in large areas of Africa with a long-term goal of substantially reducing poverty. Our findings on farmers' perceptions of soil fertility, on how farmers decide to allocate their sparse resources, on the importance of farmers' networks and on the negative return to fertilizer applications at rates that farmers can afford are important contributions to this debate. Our data from the chronosequence on degradation dynamics - and on responses to organic and inorganic soil amendments are similarly important. These socio-economic and biophysical data from the soil chronosequence enable us to predict rates of soil degradation and repletion and the affordability of different restoration strategies. Several of the groups involved in large-scale international development initiatives have contacted us to discuss the results of the Biocomplexity project and its implications for their programs.

Publications

  • Barrett, C.B., Marenya, P.P., McPeak, J., Minten, B., Murithi, F., Oluoch-Kosura, W., Place, F., Randrianarisoa, J.C., Rasambainarivo, J. and Wangila, J. 2006. Welfare dynamics in rural Kenya and Madagascar. J. of Dev. Stud. 42:1:248-277.
  • Brown, D.R., Stephens, E.C., Ouma, J.O., Murithi, F.M. and Barrett, C.B. 2006. Livelihood strategies in the rural Kenyan highlands. African J. of Ag. Res. Econ., 1(1): 21-36.
  • Hogset, H. 2007. On Economic Transfers Through Social Networks in Kenya's Smallholder Sector, in Barrett, C.B., Mude, A.G., and Omiti, J.M. Editors, Decentralization and the Social Economics of Development, CABI, Wallingford, UK. pp 189-224.
  • Kimetu J., Lehmann J., Pell, A. and Thies, J. 2007. Carbon sequestration and mitigation of carbon dioxide accumulation in the biosphere: the role of biochar in tropical agricultural systems. International Agrichar Initiative (IAI) 2007 Conference, April 27-May 2 2007, Terrigal, Australia. p 36.
  • Kinyangi, J., Solomon, D. Liang, B., Lerotic, M., Wirick, S., and Lehmann, J. 2006. Nanoscale biogeocomplexity of the organo-mineral assemblage in soil: application of STXM microscopy and C 1s-NEXAFS spectroscopy. Soil Sci. Soc. of Am. J. 70:1708-1718.
  • Lehmann, J., Kinyangi, J. and Solomon, D. 2007. Organic matter stabilization in soil microaggregates: implications from spatial heterogeneity of organic carbon contents and carbon forms. Biogeochem., 85:45-57.
  • Lehmann, J., Solomon, D. and Kinyangi, J. 2006. In-situ assessment of the spatial association of organic carbon and clay mineral forms in soil. Soil Science Society of America, Annual Meeting, Indianapolis, November 12-16, 2006. Abstract No. 119-6.
  • Amudavi, D. 2007. The Effects of Farmer Community Group Participation on Rural Livelihoods in Kenya. in Barrett, C.B., Mude, A.G., and Omiti, J.M. (eds.), Decentralization and the Social Economics of Development: Lessons from Kenya. CABI, Wallingford, UK pp159-188.
  • Amudavi, D., Kroma, M.M. and Davis, K. 2006. Understanding effects of institutional partnerships on performance of rural groups in Kenya. pp. 24-35. in Vreyens, J.D. (ed.), AIAEE 2006 Proceedings of the 22nd Conference AIAEE "International Teamwork in Agriculture and Extension Education", Clearwater Beach, Florida. Available at: http://www.aiaee.org/2006/index.html
  • Liu, J., Dietz, T., Carpenter, S.R., Alberti, M., Folke, C., Moran, E., Pell, A. N., Deadman, P., Kratz, T., Lubchenco,, J., Ostrom, E., Ouyang, Z., Provencher, W., Redman, C.L., Schneider, S. H. and Taylor, W.W. 2007. Complexity of coupled human and natural systems. Science. 317:1513.
  • Liu, J., Dietz, T., Carpenter, S.R., Folke, C., Alberti, M., Redman, C.L., Schneider, S.H., Ostrom, E., Pell, A.N., Lubchenco, J., Taylor, W.W., Ouyang, Z., Deadman, P., Kratz, T. and Provencher, W. 2007. Coupled natural and human systems. Ambio 36:640-649.
  • Marenya, P.M. and C.B. Barrett. 2007. Household-level determinants of adoption of improved natural resources management practices among smallholder farmers in western Kenya. Food Policy 32(4): 515-536.
  • Solomon, D., Lehmann, J., Kinyangi, J., Amelung, W., Lobe, I., Ngoze, S., Riha, S., Pell, A., Verchot, L., Mbugua, D., Skjemstad, J. and Schafer, T. 2007. Long-term impacts of anthropogenic perturbations on the dynamics and molecular speciation of organic carbon in tropical forest and subtropical grassland ecosystems. Global Change Biol. 13: 511-530.


Progress 01/01/06 to 12/31/06

Outputs
To better understand the relationships between environmental degradation and poverty, we studied the following areas: 1) characterization of soil organic matter to learn about its rate of degradation and contributions to soil fertility, 2) economic well-being of smallholder farmers on land with varying soil fertility, 3) effects of soil degradation on maize and bean yields, 4) contributions of livestock manure to soil fertility and nutrient balances and 5) development of a nonlinear dynamic model to integrate economic and environmental aspects of integrated crop-livestock farming systems in the East African highlands. Soil organic matter is an important aspect of soil fertility in weathered degraded soils in the tropics. Using soils from a 100-year cultivation chronosequence in western Kenya, we used a two-step fractionation process to characterize soil organic carbon into pools related to seasonal C dynamics, aggregation and long-term soil C stabilization. Using mass spectrometry evaluations of the &#948;13C signature, we were able to establish that a new lower equilibrium was used after 40 years of cultivation. Cultivated soils had less light and aggregate-associated carbon compared to forest soils. On the same plots with various soil amendments, data on crop yields and on the economic status of the farmers were collected to determine whether the soil fertility of recently converted soils can be economically maintained through soil amendments using chemical fertilizers, green manure crops (Tithonia) and livestock manure. For soils in cultivation for more than 20 years, addition of nitrogen and phosphorus is necessary to maintain maize yields. For plots in cultivation for more than 25 years, nitrogen from manure was immobilized in the soil and not rapidly available for plant uptake. Tithonia was a more effective amendment than triple super phosphate on older conversions. Information on what incentives are needed to induce farmers to make environmental investments also was obtained. Because livestock manure is the most commonly used soil amendment, experiments were undertaken to establish the variation in the chemical composition of manure from confined dairy cows related to diet, length and method of storage as well as the degradation rate of the manure in the soil. Much of the last year has been devoted to developing a nonlinear dynamic model with integrated crop, soil, economic and livestock components to describe the relationships between soil degradation and poverty. The preliminary version of the model is currently being evaluated prior to running simulations to predict how the system would behave under different economic and environmental conditions.

Impacts
Because the goal of this project is to understand the dynamics of environmental degradation and poverty in the Kenyan highlands, the results should be relevant to a broad group of people including participating farmers, their advisors and policy makers. Farmers should be able to make informed decisions about how to avoid falling into poverty and how to maintain soil fertility to maintain crop yields. At the policy level, understanding that only about 9 percent of the people who were below the Kenyan poverty level of $.53 per day in 1989 were able to escape poverty unassisted by 2002 will provide government officials with useful information on who becomes poor, who escapes poverty and some of the reasons why. We now have a better understanding of how severely a soil can be degraded while retaining the potential for remediation. This information can help farmers and extension workers decide when and how to add nutrients and organic matter to soils to restore and maintain their fertility.

Publications

  • Riha, S.J., C.B. Barrett, L.E. Blume, J.M. Kinyangi, C.J. Lehmann, P.P. Marenya, D.M. Mbugua, C.F. Nicholson, D. Parsons, L.V. Verchot, and A.N. Pell. 2006. Long-term human and biophysical dynamics of soil degradation in the Kenyan Highlands. World Congress of Soil Science, June 9-15, 2006, Philadelphia, PA.
  • Kapkiyai, J.J., S.D. DeGloria, J.M. Duxbury, A.N. Pell, B. Vanlauwe and D.M. Mbugua. 2006. Household level influence on spatial variability of soil properties in Western Kenya. World Congress of Soil Science, June 9-15, 2006, Philadelphia, PA.
  • Ngoze, S., S.J. Riha, J.M. Kinyangi, J. Lehmann, L. Verchot, D.M. Mbugua and A.N. Pell. 2006. Soil fertility degradation and management in the highlands of Kenya. World Congress of Soil Science, June 9-15, 2006, Philadelphia, PA.
  • Kinyangi, J., J. Lehmann, A. Pell, J. Thies, L. Verchot, D. Mbugua, S. Ngoze, and S. Riha. 2006. Soil organic matter stabilization and associated degradation threshold dynamics. World Congress of Soil Science, June 9-15, 2006, Philadelphia, PA
  • Pell, A.N. 2006. Animals as part of soil systems. In: Biological Approaches to Sustainable Soil Systems. Eds. Uphoff, N.T., A. Ball, E. Fernandes, H. Herren, O. Husson, M. Laing, C. Palm, J. Pretty, P. Sanchez, N. Sanginga and J. Thies. CRC Press pp 241-253.
  • Rothman, J.M., E.S. Dierenfeld, and A.N. Pell. 2006. Diet of the Bwindi gorillas in relation to nutritional quality. 21st Congress International Primatological Society. June 25-30, 2006. Entebbe, Uganda.
  • Frey, J.C., J.M. Rothman, A.N. Pell, J.B. Nizeyi, M.C. Cranfield, and E.A. Angert. 2006. Bacterial diversity in the feces of a silverback gorilla (Gorilla beringei) in Bwindi Impenetrable National Park, Uganda. 21st Congress International Primatological Society. June 25-30, 2006. Entebbe, Uganda.


Progress 01/01/05 to 12/31/05

Outputs
Progress has been made on data analysis and model development to increase understanding of the relationships between poverty and environmental degradation in Kenya. Graduate students in Crop and Soil Science have made progress describing different soil organic matter (SOM) fractions of soils collected from a 100-year chronosequence using mass spectrometry and changes in the delta-13 signature. In forest soils, large amounts of light and aggregate associated SOM (22 percent and 7 percent of soil weight) are retained while agricultural cultivation results in loss of both fractions (2 percent of soil weight-long term equilibrium) and the subsequent dominance of organo-mineral associated organic matter (98 percent of soil weight). The C:N ratio of forest and cultivated soils does not appear to influence mineralization and immobilization transformations (MIT) (C:N=25), suggesting that a MIT equilibrium is maintained in soils where rapid transformations in C and N are occurring between SOM pools. Physicochemical binding in organo-mineral complexes of soil micro-aggregates contributes to carbon stabilization in soils. We combined nano-scale sample processing with synchrotron based scanning transmission x-ray microscopy (STXM) and near edge x-ray absorption fine structure spectroscopy (NEXAFS) to investigate the protection of carbon within interior and exterior pore regions of intact soil micro-aggregate sections. We observed a highly patchy, near random nano-scale distribution of C that was stabilized between pore spaces and bound to the mineral domain. Phosphorus and nitrogen dynamics on the chronosequence of soil fertility degradation have been assessed after application of high or low quality organic material as sources of P and N. We have measured crop responses to N and P fertilizer on smallholder farms at different intervals after conversion from forest and we are determining to what extent the process of soil degradation is reversible. In addition, samples have been collected from the same sites for analysis of gas evolution and shifts in microbial communities. We now have 4 complete seasons of crop yield data from these sites as well as from Madzuu. The contribution of animals to nutrient cycling on the same smallholder farms is under investigation as well. Dacron bag experiments have been conducted to determine the rates of decomposition of high and low quality manure to predict the value of manure as a soil amendment. On the economics side, we are studying why many farmers fail to behave according to microeconomic logic when it comes to decisions about investment in soil fertility. Although the data have been collected, analysis is still underway. One of the goals of our project is to develop a dynamic model of the linked biophysical and social systems. On the biological side, the main focus of the model is to track nitrogen and phosphorus within the boundaries of the farm system accounting for soil amendments, crop use, soil status and the impact of animals. During the past year, considerable effort has been expended to refine this model. With some additional structural development, the model should be ready for calibration and testing.

Impacts
Because the goal of this project is to understand the dynamics of environmental degradation and poverty in the Kenyan highlands, the results should be relevant to a broad group of people including participating farmers, their advisors and policy makers. Farmers should be able to make informed decisions about how to avoid falling into poverty and how to maintain soil fertility to maintain crop yields. At the policy level, understanding that only about 9 percent of the people who were below the Kenyan poverty level of $.53 per day in 1989 were able to escape poverty unassisted by 2002 will provide government officials with useful information on who becomes poor, who escapes poverty and some of the reasons why. We now have a better understanding of how severely a soil can be degraded while retaining the potential for remediation. This information can help farmers and extension workers decide when and how to add nutrients and organic matter to soils to restore and maintain their fertility.

Publications

  • Barrett, C.B. 2005. Mixing qualitative and quantitative methods of analyzing poverty dynamics. in Odhiambo, W., Omiti, J.O. and Muthaka, D.I., eds., Proceedings of the Workshop on Quantitative and Qualitative Methods for Poverty Analysis, Kenya Institute for Public Policy Research and Analysis, Nairobi.
  • Barrett, C.B. 2005. Poverty Traps and Natural Resources Management. in Wright, R.T., Environmental Science, 9th Edition, Pearson Prentice Hall, Upper Saddle River, NJ.
  • Brown, D.R., and Barrett, C.B. 2005. Maize-Bean Intercropping and Smallholder Productivity in Kenya's Highlands. Kenya BASIS Policy Research Brief Number 8, USAID, Washington, DC.
  • Marenya, P.P. and Barrett, C.B. 2005. Adoption of Integrated Natural Resources Management Practices Among Smallholder Farmers in Western Kenya. Kenya BASIS Policy Research Brief Number 5, USAID, Washington, DC.
  • Mbugua, D.M., A.N. Pell, D.G. Fox and Schofield, P. 2005. The effects of proanthocyanidins from Calliandra calothyrsus and the alkaloid spartein on in vitro fiber digestion. Anim. Feed Sci. Technol.121:1-2:89-107.


Progress 01/01/04 to 12/31/04

Outputs
Small changes in the natural resource base may have important consequences for poor smallholder farmers in the highlands of central and western Kenya. Likewise, modest changes in human activities may alter ecosystem functioning in these frequently degraded environments. Our goal is to capture the dialog between farmers and their environment in order to measure, understand and model the interlinked biophysical and socioeconomic processes characteristic of small crop-livestock farms in Kenya. We have collected data from 239 farms in two sites in central and western Kenya (Embu and Vihiga districts) on soil chemistry and biology, crop and livestock production, socioeconomic conditions, land use, and on-farm and off-farm labor allocation and investment patterns. To determine the effects of cultivation on soil fertility, soil samples have been collected from a chronosequence in an area where plots have been cultivated from 1 to more than 100 years (8 time points) with 4 complete blocks. Total soil carbon and the aggregate light and free light fractions of soil organic matter decrease with time of cultivation while the organo-mineral fraction increases. Surveys have been administered to measure poverty dynamics of agricultural households. In our western Kenya site in Vihiga District, we found evidence of all of the indicators of poverty traps. Those who remained non-poor over time started off with statistically significantly higher endowments of land, improved livestock and educated family members, as well as greater and more remunerative off-farm employment to generate cash necessary to invest in chemical fertilizer and other critical integrated soil fertility management interventions. Considerable effort has been expended to link social and biophysical aspects of the agro-ecosystem in a dynamic model in order to explore the relationships between farmers' perceptions of their options and biophysical and economic processes. Our prototype bioeconomic model includes modules for soil fertility and herd dynamics, cash resources and labor flows as well as crop and livestock production and the use of livestock manure as a soil amendment, reproducing the typical dynamics of the human and natural resource system. This simple model demonstrates the fertility and income dynamics common in the study area, where even minimal soil nutrient amendments (such as might be obtained by intercropping beans with maize and leaving residues on the field to be grazed by small animals during the dry season) can generate persistent gains in soil health and farmer well-being. The model, with minimal soil amendment (as might be obtained by inter-cropping beans and maize and leaving residues for grazing during the dry season), reflects fertility and income dynamics common in the study area. Fertility is very high when land is converted from forest and declines rapidly to a low-level dynamic equilibrium sufficient to meet only basic consumption needs. After 10 years (20 seasons), there is no further accumulation of surplus and receipts are only adequate to meet basic consumption needs. Without minimal soil amendment, the system collapses after 15 years.

Impacts
The goal of our project is to understand the on-going conversation between farmers and their natural resource base in areas where both soil degradation and poverty are serious problems (more than 50 percent of our respondents earn less than $.50 per day). By understanding these relationships, we hope both to alleviate poverty and to prevent further degradation of the agroecosystem. This research should have broad applications in the densely-populated highlands of eastern and southern Africa, areas that have high levels of poverty and environmental degradation. In these areas, most of the poor live in rural areas and about seventy percent of the rural population is involved in agriculture.

Publications

  • Pell, A.N., Barrett, C.B., Lehmann, C.J., Amudavi, D., Blume, L.E., DeGloria, S.D., Duxbury, J. M., Duxbury, Harawa, R., Kadzere, I., Kapkiyai, J.J., Ketterings, Q.M., Kinyangi, J.M., Kroma, M.K., Marenya, P.P., Markewich, H.A., Mbugua, D.M., Medvecky, B.A., Menete, M.Z., Ngoze, S.O., Nherera, F.V., Owiyo, T., Riha, S.J., van Es, H.M., and Watkins,C.B. 2004. Natural Resource Management at Cornell: Graduate Education, Research, and Modeling. Rockefeller Foundation Meeting on Soil Fertility, September 20-23, 2004, Nairobi, Kenya.
  • Owiyo, T., Shepherd, K., DeGloria, S.,Walsh, M. and Pell, A.. 2004. A comparative analysis of soil quality as a function of land use; Evidence from modeling hyperspectral data. Rockefeller Foundation Meeting on Soil Fertility, September 20-23, 2004, Nairobi, Kenya.
  • Pell,A.N., Mbugua, D.M.,Verchot, L.V., Barrett, C.B., Blume, L.E., Gamarra, J.G.P., Kinyangi, J.M., Lehmann, C.J., Odenyo, A.O., Ngoze, S.O., Okumu, B.N., Pfeffer, M.J., Marenya, P.P., Riha, S.J. and Wangila, J. 2004. The Interplay Between Smallholder Farmers and Fragile Tropical Agroecosystems in Kenya. Symposium on Frontiers in Biocomplexity: Reciprocal Interactions between Human and Natural Systems. AAAS Annual Meeting, February 14, 2004, Seattle, WA.


Progress 01/01/03 to 12/31/03

Outputs
The goal of this project is to determine the relationship between smallholder farmers in Kenya and their agroecosystem. During the past year, we have collected and analyzed approximately 2000 soil samples from research sites in Embu in central Kenya and Madzuu in Vihiga District using near-infrared spectroscopy with appropriate calibrations using standard wet chemistry techniques. Using the spectral data and a soil fertility index that includes effective cation exchange capacity, pH, exchangeable K, extractable P and N mineralization potential, it is clear that the soils in Embu are less degraded than those in Madzuu. Farmers make informed decisions about where they plant which crops although the patterns differ among sites. In Embu, the most fertile plots are those with tea and pasture, the two most lucrative cash crops. In Madzuu, the most fertile plots are those for the home gardens. In Madzuu, the worst land is used for tea which is regarded as a crop of last resort. To examine the dynamics of degradation in western Kenya, we have identified plots that were converted from forest to agriculture 100, 70, 50, 30, 15, 5 and less than 3 years ago. Samples from the forest have served as the control. Six blocks including each of the 8 conversion times have been identified based on conversations with village elders and by consulting local records. Soil samples from three farms in each conversion time for each of the blocks have been taken and subjected to NIR analysis. We also are determining fractions of soil organic matter (SOM) on these soils. These fractions provide a good index of soil degradation. Preliminary data show that the amounts of soil organic carbon and soil enzyme activities decrease rapidly over the first ten years following conversion. Experiments have been established on the same village and chronosequence plots to determine how the nutrients in these plots can be replenished. As a result, we should have useful information on the dynamics of soil degradation and soil repletion to use for the development of a dynamic model. Samples from the chronosequence plots also are being analyzed to look at differences in microbial populations from plots converted to agriculture at different times. We are using DGGE and T-RFLP to detect these changes. An important aspect of our project is to develop a dynamic model with feedback loops between farmers and their natural resource base. The structure of this model has been developed and we now are refining it and parameterizing it. This model includes a human decision-making component, a biophysical component that includes submodels for crops, soils and livestock and mechanisms by which decisions by the farmer affect ecosystem function and vice versa.

Impacts
The goal of our project is to understand the on-going conversation between farmers and their natural resource base in areas where both soil degradation and poverty are serious problems (more than 50 percent of our respondents earn less than $.50 per day). By understanding these relationships, we hope both to alleviate poverty and to prevent further degradation of the agroecosystem.

Publications

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