D.D. Onduru

Assessing sustainability of low-external-input farm management systems with the nutrient monitoring approach: a case study in Kenya

In the search for Integrated Nutrient Management practices in response to the widely observed soil fertility decline in Sub-Saharan Africa, the potential of low-external-input and organic farming remains to be systematically examined. The nutrient monitoring concept was used to assess the impact of technologies on nutrient flows and economic performance at activity and farm household level in Machakos district, Kenya. The nutrient flows and balances and economic performance indicators of farms practising low-external input agriculture (LEIA) technologies for a number of years were compared with a group of farms practising conventional farm management. Based upon monitoring two farming seasons, it was concluded that both subsistence-oriented farm management systems result in serious N-depletion and that 60–80% of farm income is based upon nutrient mining. No significant differences could be found between the LEIA and conventional farm management group. Only if LEIA farm management reduces nutrient losses through leaching and gaseous losses can a positive impact on nutrient balance be expected. Off-farm income plays a crucial role, especially in the conventional management group, in keeping farm household income levels above the poverty line. High-level compost application treatments in maize are attractive if labour and organic inputs are available. # 2001 Elsevier Science Ltd. All rights reserved.

Facilitated learning in soil fertility management: assessing potentials of low-external-input technologies in east African farming systems

The paper describes the facilitated learning process of farm households and district policy makers in addressing the problem of soil nutrient depletion. The process is applied in a case study in four districts in Kenya and Uganda during the period 1997-1999, where the potentials of low-external input technologies (LEIA) in addressing the soil nutrient depletion problem were assessed. Working through an inclusive process of dialogue, observation, diagnosis, experimentation and exposure to different types of knowledge, participants made a thorough analysis of the current soil fertility situation and tested various LEIA options for improving soil fertility management. In all four research sites the future agricultural productivity is threatened by soil nutrient depletion. Maximal use of locally available nutrients through LEIA techniques, combined with optimal use of external nutrients appears to be the most appropriate strategy in the existing economic environment. Long-term and intensive collaboration between research institutions on the one hand and extension services, non-government and community based organisations on the other are a prerequisite for a successful and sustainable implementation of a facilitated learning approach. Involvement of stakeholders in the various stages of the research process, including the planning and project formulation is essential for an effective follow-up and implementation of the results. More attention needs to be paid to the development of communication tools to enable an effective interaction between policy makers and researchers

Farm nitrogen flows of four farmer field schools in Kenya

Re-use of nutrients within farming systems contributes to sustainable food production in nutrient limited production systems. Re-use is established when nutrients pass through several farm compartments before they leave the farm via marketable products. In this paper re-use of nitrogen is examined as an indicator for sustainable soil fertility management. Re-use (RU, kg farm−1) was defined as the amount of nitrogen that was translocated within one farm divided by the sum of transitions between farm compartments within a farm. In 2002, a total of 101 farms belonging to 4 farmer field schools in Kenya were analysed using the NUTMON (now known as MonQI) toolbox. The farms were distributed over 4 farmer field schools located in two agro-ecological zones. RU was positively related to the net farm income and to crop yields. However, data were scattered and often local farm conditions veiled the relation between nitrogen management strategies and farm performances. The results of this paper demonstrate that different agro-ecological zones with diverse production constraints have developed different in-farm nitrogen management strategies that are best adapted to the local conditions, but may have different environmental impacts.

Ecological and agro-economic study of small farms in sub-Saharan Africa

Land degradation, rising population and poverty in sub-Saharan Africa threatens the agricultural sustainability and productivity, quality of the environment and socio-economic wellbeing of rural populations. We studied farm ecological, economic and social sustainability, productivity and production risks in the Mbeere District of Eastern Kenya. We used a soil nutrient monitoring methodology to collect data from 30 households. Ecological sustainability was threatened by soil nutrient decline at rates of 1.7 kg P and 5.4 kg K ha−1 half year−1 while N was nearly balanced in soils. Soil phosphorus and potassium stocks, in the cultivated soils, declined at rates of 0.3% and 0.1% half year−1, respectively. Farm economic returns were positive, albeit low, and could not sustain the livelihoods of the households. All the 30 households were living below the poverty line of 1 US dollar a day. Farm productivity was low, with livestock and yields of major staple food crops below on-farm target yields. To spread out the risks of production, farming households were cultivating an average of 4.7 crop fields, keeping more than two types of livestock and practising intercropping systems. Intercropping maize-beans reduced nutrient decline and raised household incomes compared with monocropping of either of the two crops. Despite the low rates of nutrient decline, high risks of production and the low crop yields, the livestock productivity and farm economic performance put the sustainability of these farming systems into question. The low levels of nutrient decline in small farms averaging at 1.7 kg P and 5.4 kg K ha−1 half year−1 contrasts with the high nutrient depletion rates on macro-scale levels, e.g. 20–40 N, 3.5–6.6 kg P and 20–40 kg K ha−1 year−1 for Eastern African countries and 22 kg N, 2.5 kg P and 15 kg K ha−1 year−1 for sub-Saharan Africa. These findings indicate that the extent of nutrient decline and conservation differs across sub-Saharan Africa. The positive contribution of intercropping to nutrient balances suggests the need to encourage farmers to adopt such systems rather than monocropping.

Soil Quality and Agricultural Sustainability of Dryland Tropical Farming Systems

Abstract A study was carried out to investigate soil quality of dryland farming systems of Mbeere District, Eastern Kenya and its implications on agricultural sustainability. Soil sampling was done in years 2002 and 2004 from 30 study farms and same sampling sites and from paired adjacent land-use systems (bush fallow and cultivated fields). Physical, chemical and biological laboratory analyses were carried out. Factor analysis showed that the main soil quality indicators for evaluating sustainability of the dryland farming systems of the district were texture; organic matter, exchangeable bases (Ca, Mg, K, and Na); extractable nutrients (P and Zn); and acidity (pH). Cultivated soils were characterised by low pH, nutrient deficiencies (N, P, Cu, and Zn) and low organic matter and a decline in organic C, total N, exchangeable K and extractable P across time. They were also lower in exchangeable bases and microbial biomass C than adjacent bush fallow soils. We conclude that the soils are degraded and farming systems are partially unsustainable and may increasingly be so in the near future if declining soil quality is not addressed.

Soil Quality and Agricultural Sustainability of Dryland Tropical Farming Systems: A Case Study in Mbeere District

Abstract A study was carried out to investigate soil quality of dryland farming systems of Mbeere District, Eastern Kenya and its implications on agricultural sustainability. Soil sampling was done in years 2002 and 2004 from 30 study farms and same sampling sites and from paired adjacent land-use systems (bush fallow and cultivated fields). Physical, chemical and biological laboratory analyses were carried out. Factor analysis showed that the main soil quality indicators for evaluating sustainability of the dryland farming systems of the district were texture; organic matter, exchangeable bases (Ca, Mg, K, and Na); extractable nutrients (P and Zn); and acidity (pH). Cultivated soils were characterised by low pH, nutrient deficiencies (N, P, Cu, and Zn) and low organic matter and a decline in organic C, total N, exchangeable K and extractable P across time. They were also lower in exchangeable bases and microbial biomass C than adjacent bush fallow soils. We conclude that the soils are degraded and farming systems are partially unsustainable and may increasingly be so in the near future if declining soil quality is not addressed.