Farmers and researchers on their way to Integrated Nutrient Management
Kenyan farmers taking part in the NUTMON study know that land productivity had been declining for years. They also know that continuous cropping and manure shortages are to blame. The aim of the NUTMON programme is to build on this consciousness and increase farmer awareness of the role of nutrients in agricultural production and to develop a tool that can assess nutrient balance and economic performance at farm level. (ILEIA)
ILEIA Newsletter • 13 nº 3 • October 1997
Farmers and researchers on their way to Integrated Nutrient Management
Kenyan farmers taking part in the NUTMON study know that land productivity had been declining for years. They also know that continuous cropping and manure shortages are to blame. The aim of the NUTMON programme is to build on this consciousness and increase farmer awareness of the role of nutrients in agricultural production and at the same time to develop a tool that can assess nutrient balance and economic performance at farm level.
Nutrient miningKenya is an example of a country where more nutrients are being extracted from the soil than return to it. Although the exact relationship between negative nutrient balances and crop yields is not clear, nutrient mining has lead to declining yields. Like many African countries Kenya needs higher production levels to feed its growing population, a situation which will become increasingly difficult in future as the critical indicators of nutrient output/input and per capita food production show. Stoorvogel and Smaling (1990) found that nutrient outputs exceed inputs by 42kg N, 3kg P and 29kg K ha-1 year-1 and studies show that per capita food production had been steadily declining since the late 1980s (De Jager et al. 1997).
Nutmon-Nutrient ManagementThe NUTMON concept (see Figure 1) integrates different knowledge systems (farmers’ knowledge and scientific knowledge) and sciences (biophysics and economics) to assess nutrient balances and economic performance at farm level and to develop Integrated Nutrient Management (INM). Integrated Nutrient Management is defined as the best possible combination of available nutrient management practices, that is they are biophysically powerful, economically attractive and socially acceptable. The interdisciplinary approach was a necessary response to the fact that farmers' goals are not only economic but cultural, social and ecological as well.
Four Kenya districts, in different ecological areas (Kisii, Kakamega, Embu, Kilifi), were chosen and land-use zones (LUZ) were identified during discussions with local experts and with the help of satellite image interpretation. The objective of this phase of the NUTMON programme was to develop a methodology that would help farmers manage nutrient balance in their fields.
Multi-disciplinary teams of agronomists, soil scientists, livestock specialists, sociologists and economists from the Kenyan Agricultural Research Institute's (KARI) regional research centres made Participatory Rural Appraisals (PRA) in each of the land-use zones. It was the first time that these research teams had made PRAs. They conducted interviews with a cross-section of key individual and group informants including farmers, administrators and extension workers.
Farmer awarenessInterviews confirmed that the farmers interviewed had been aware of the gradual decline in land productivity for several years. They attributed this decline to continuous cropping on the same fields, steadily diminishing supplies of manure as livestock number declined, overgrazing and soil erosion. However, they were not aware of the key role played by nutrients in these processes or how this affected soil productivity.
Farms were selected for the NUTMON programme on the basis of information provided by Participatory Rapid Appraisal. Criteria for selecting two or three farm households in each land-use zone included a willingness to participate in the monitoring programme, cropping pattern, livestock activities, farm size, farm management practices, product marketing and off-farm income activities.
Nutrient monitoringAn initial inventory of household composition, farm and field layout, agricultural activities and nutrient stocks was completed for each farm. This inventory was followed by a monthly monitoring of those on-farm agricultural activities that affect nutrient flows. In addition to the monitoring of nutrient management, the activities of the farm family, their cash income and the allocation of labour were also studied.
The nutrient balance - the product of nutrient inputs and nutrient outputs - was calculated for both the farm as a unit and for its field(s). Nutrient output included harvested crop products and residues, nutrients leached out below the root zone, gaseous losses from the top soil, erosion and human excreta lost because it ends up in deep pit latrines far below the root zone. Nutrient inputs into the system were mineral fertilisers, organic inputs (manure, imported crop residues and feeds), air-borne deposition, biological N-fixation by plants, sedimentation and nutrients extracted from the sub-soil by deep-rooting crops and trees (see Figure 2).
Economic performance indicators were calculated at both activity (crop, livestock and off-farm activities) and farm household level. In addition a number of general farm household characteristics such as household size, labour and consumer units were also determined. The main indicators at activity level were gross margins (gross return minus variable costs) and net cash flows (cash receipts minus cash payments) per unit area. At farm household level net farm income (total gross margin minus fixed costs) and family earnings (net farm income plus off-farm income) were the most important indicators.
Results of nutrient flow analysisThe analysis of the nutrient flows and balances showed that the average nutrient balance of 26 farms was negative for nitrogen (N) and potassium (K) and slightly positive for Phosphors (P) as is shown in Figure 3. The total nutrient balance can be disaggregated into two partial balances. Partial Balance 1 (IN1+IN2-OUT1-OUT2) in Figure 2 consists of direct nutrient inputs and outputs, such as fertilisers and crop harvests. Partial Balance 2 (IN3+IN4+IN5+IN6-OUT3-OUT4-OUT5-OUT6) is made up of biophysical flows such as the fixation of nitrogen and erosion. This desegregation of the overall balances into two partial balances shows that Partial Balance 1 turns positive for the three macro nutrients, which means that, in general, the farmers are compensating for the losses made by harvested products. It is basically the loss processes of Partial Balance 2 that cause overall nutrient depletion.
Results of economic analysis
The economic analyses at activity level showed that cash crops, as compared to staple crops, were far more profitable and at the same time had less negative nutrient balances than food crop because more inputs were invested in them (Figure 4). However, at farm level a higher nutrient loss was calculated for the more market-oriented farms. This seeming contradiction was caused by the way the households managed their livestock.
Assessing sustainabilityThe following indicators were calculated to assess the overall ecological and economic sustainability of this sample. On average 32% of the net farm income was based on nutrient mining. In other words, the farm income would be reduced by 32% if the depleted nutrients were actually replaced. About 54% of the farms generate returns from agriculture that are insufficient to meet basic food and non-food requirements. Farms in this category were already dependant on off-farm income for their survival.
Changes in perception and practiceNUTMON monitoring results showed that although farmers were not familiar with nutrient flows and their role in soil productivity, in general they were balancing crop harvest nutrient outputs with inputs such as manure and fertilisers. During the process of monitoring it was clear from the changes farmers made in their farming system that they were becoming more aware of the importance of assessing nutrient balances. One woman farmer bought three bags of fertiliser for her tea plot instead of one because, as she said "I'm taking more from the land than I'm giving to it". NUTMON farmers in an Embu land zone changed their manuring practice: instead of waiting to use their old livestock corral as a location for planting crops until a new corral had been established, they began to move corral manure to their various fields. This resulted in more efficient nutrient applications. The quality of the manure also improved because farmers began to protect it from the effects of the sun. Although it is not yet clear how NUTMON farmers used the economic performance indicators of their various activities, they were very keen to know whether they were making a profit or loss.
Evaluating the roleThe results of the pilot project showed that determining nutrient balances provides an insight into the flow patterns within and in and out of the farming system. As such the concept of nutrient balance is an important learning and evaluation tool in optimising nutrient management. The partial balances derived for the NUTMON farms indicated that in most cases it was more worthwhile to conserve nutrients by taking measures against leaching and erosion than it was to make further fertiliser applications which, in any case, often lead to higher losses. These nutrient flows can be analysed and linked to economic data so that the most important nutrient outflows can be reduced by taking cost-effective measures. Partial nutrient balance can also be used to classify farms in order to design more specific and effective policy measures and extension services.
The additional socioeconomic evaluation can be used as an indicator of how much room there is for manoeuvre an individual farm household has when particular solutions are being considered. Such an evaluation enables an assessment of the profitability of certain interventions and, as research results showed, this was clearly an important criteria in farm household decision making.
The next stepThis pilot project dealt with one aspect of the NUTMON concept and produced tools for monitoring and analyses that, with minor modifications, can be used elsewhere in Africa. One objective of the NUTMON programme is to develop a complete tool for nutrient management which will include surveys, manuals, data entry and analysis software capable of assessing economic and environmental sustainability at farm level. It is hoped that this will become available before July 1998.
Farmers, governments and NGOsThe farmer-expert in soil fertility management must be able to observe, infer and anticipate and, on this basis, take decisions for actions that will be subsequently implemented and evaluated. This means that farmers must be stimulated to develop their knowledge of the nutrient flow within their farms and how this relates to crop productivity. NGOs, extension agencies and governments are also potential end-users of NUTMON results, although they may have other requirements. Governments, for example, will be interested in the economic impact of nutrient mining and the effect of certain policies on the financial position of the farm household and the ecological sustainability of its farming system. To meet such demands, representative farm samples have to be selected and linkages between nutrient balances and yields have to be quantified. NGOs, on the other hand, will be more concerned with practical applications such as the economic and ecological effect of certain soil conservation measures and less interested in setting up intensive monitoring systems. This means that simplified and less data-demanding tools will have to be developed.
Although there is still much to be done, an integrated science package is being developed which, when combined with farmers' knowledge can be used in a joint effort to reduce nutrient mining and encourage the development of more sustainable farming systems.
- De Jager A., Kariuku I, Matiri FM, Odendo M and Wanyama JM. (forthcoming 1988) Linking economic performance and nutrient balances in different farming systems in Kenya: a synthesis towards an integrated analyses of economic and ecological sustainability. In: Agric. Ecosystems Environ. (in press)
- Smaling EMA 1991 Africa's soils are being mined. In: ILEIA Newsletter, May 1991, Leusden, The Netherlands.
- Stoorvogel JJ, and Smaling EMA., 1990 Assessment of soil nutrient depletion in Sub-Saharan Africa, 1983-2000. Report 28, DLO Winand Staring Centre for Integrated Land, Soil and Water Research (SC-DLO), Wageningen, The Netherlands
- Van den Bosch H, De Jager A, and Vlaming J (forthcoming 1988) Farm-NUTMON: a tool to determine the nutrient flows and economic performance of Kenyan farming systems. In: Agric. Ecosystems Environ. (in press)
- Pol, F. van der, 1993. Analysis and evaluation of options for sustainable agriculture, with special reference to southern Mali. In: H. van Reuler and W.H. Prins (eds). The role of plant nutrients for sustainable food crop production in Sub-Saharan Africa. VKP, Leidschendam, The Netherlands.