Browsing by Author "Vanlauwe, B."

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    Changes in Soil Organic Matter as Influenced by Organic Residue Management Regimes in Selected Experiments in Kenya
    (Springer, 2007) Waswa, B.S.; Mugendi, Daniel N.; Vanlauwe, B.; Kung’u, J.
    The failure to understand the dynamics of soil organic matter (SOM) is a major limitation to the sustainability of smallholder production systems that predominantly relied on organic resources for the maintenance of soil fertility. This study evaluated the influence of organic resource management on SOM in three selected experiments in central and western highlands of Kenya. Results showed that soil carbon (C), nitrogen (N) and carbon-13 (13C) values in the three experiments were depending on the amounts of the organic residues applied as well as the duration of application indicating that organic residue management practices have a profound impact on the final contribution to the SOM pools. Kabete experiment had the narrowest C, N and 13C values pointing to its young age as well as the low quantity of the organic residues applied. On the other hand, Embu experiment had soil C values above the critical level of 2.0% indicating a positive effect of continued application of organic residues. In all the three sites, aggregate mineral fraction (MF) size distribution were dominated by macroaggregates (250–500μm and >500 μm) which on average accounted for about 72%, 65% and 69% of the dry soil weight for Maseno, Kabete and Embu experiments, respectively. Similarly higher proportions of aggregate light fractions (LF) C and N were observed in macroaggregate fractions for the three experiments with organic treatments having higher proportions. The 13C signatures of the LF in the macroaggregates (>250 μm) were more negative as compared to the 13C values in the microaggregate (53–250 μm) LF suggesting a more C contribution from C3 vegetation to the most recently incorporated SOM pool
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    Dissemination of Integrated Soil Fertility Management Technologies Using Participatory Approaches in the Central Highlands of Kenya
    (Springer Netherlands, 2011-06) Mugendi, Daniel N.; Mugwe, Jayne; Mucheru-Muna, Monicah; Karega, R.; Muriuki, J.; Vanlauwe, B.; Merckx, R.
    Declining soil fertility and productivity is a critical problem facing smallholder farmers in the central highlands of Kenya. A study to improve soil fertility and farm productivity within the smallholder farming systems in the area was carried out from 2003 to 2006. The specific objectives were to identify farming system constraints, evaluate and disseminate potential integrated soil fertility management (ISFM) interventions using participatory approaches, assess achievements and impacts, and document learning experiences emanating from the methodologies used. The participatory approaches used were Participatory Rural Appraisal (PRA), mother–baby approach (with emphasis on demonstration), farmer groups, stakeholders planning meetings, village training workshops, cross-site visits and participatory monitoring and evaluation. The core problems identified were low crop and fodder yields that were caused by erratic rainfall, soil erosion, low soil fertility and small land sizes. There was high participation of farmers in all the partnership activities, and this possibly contributed to the high uptake of the technologies for testing by farmers whereby after only 2 years a total of 970 households were testing the new technologies. Maize yields at the farm level increased by more than 150% following use of the new ISFM interventions and about half of the farmers within the groups planted close to 500 trees propagated in the group nurseries. We recommend that pathways to reach more farmers should concentrate on demonstrations, farmer training grounds, field days and farmer groups and that a policy framework should be put in place to impart appropriate skills in ISFM to the extension workers.
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    The diversity of rural livelihoods and their influence on soil fertility in agricultural systems of East Africa – A typology of smallholder farms
    (2010) Tittonell, P.; Muriuki, A.; Shepherd, K.D.; Mugendi, Daniel N.; Kaizzi, K.C.; Okeyo, J.; Verchot, L.; Coe, R.; Vanlauwe, B.
    Technological interventions to address the problem of poor productivity of smallholder agricultural systems must be designed to target socially diverse and spatially heterogeneous farms and farming systems. This paper proposes a categorisation of household diversity based on a functional typology of livelihood strategies, and analyses the influence of such diversity on current soil fertility status and spatial variability on a sample of 250 randomly selected farms from six districts of Kenya and Uganda. In spite of the agro-ecological and socio-economic diversity observed across the region (e.g. 4 months year−1 of food self-sufficiency in Vihiga, Kenya vs. 10 in Tororo, Uganda) consistent patterns of variability were also observed. For example, all the households with less than 3 months year−1 of food self-sufficiency had a land:labour ratio (LLR) < 1, and all those with LLR > 1 produced enough food to cover their diet for at least 5 months. Households with LLR < 1 were also those who generated more than 50% of their total income outside the farm. Dependence on off/non-farm income was one of the main factors associated with household diversity. Based on indicators of resource endowment and income strategies and using principal component analysis, farmers’ rankings and cluster analysis the 250 households surveyed were grouped into five farm types: (1) Farms that rely mainly on permanent off-farm employment (from 10 to 28% of the farmers interviewed, according to site); (2) larger, wealthier farms growing cash crops (8–20%); (3) medium resource endowment, food self-sufficient farms (20–38%); (4) medium to low resource endowment relying partly on nonfarm activities (18–30%); and (5) poor households with family members employed locally as agricultural labourers by wealthier farmers (13–25%). Due to differential soil management over long periods of time, and to ample diversity in resource endowments (land, livestock, labour) and access to cash, the five farm types exhibited different soil carbon and nutrient stocks (e.g. Type 2 farms had average C, N, P and K stocks that were 2–3 times larger than for Types 4 or 5). In general, soil spatial variability was larger in farms (and sites) with poorer soils and smaller in farms owning livestock. The five farm types identified may be seen as domains to target technological innovations and/or development efforts
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    Effect of Reduced Tillage and Mineral Fertilizer Application on Maize and Soybean Productivity
    (2012) Kihara, Jimmy H.; Bationo, A.; Waswa, B.; Kimetu, J.M.; Vanlauwe, B.; Okeyo, J.; Mukalama, J.; Martius, C.
    Reduced tillage is said to be one of the potential ways to reverse land degradation and ultimately increase the productivity of degrading soils of Africa. We hypothesised that crop yield following a modest application of 2 t ha−1 of crop residue in a reduced tillage system is similar to the yield obtained from a conventional tillage system, and that incorporation of legumes in a cropping system leads to greater economic benefits as opposed to a cropping system involving continuous maize. Three cropping systems (continuous maize monocropping, legume/maize intercropping and rotation) under different tillage and residue management systems were tested in sub-humid western Kenya over 10 seasons. While soybean performed equally well in both tillage systems throughout, maize yield was lower in reduced than conventional tillage during the first five seasons but no significant differences were observed after season 6. Likewise, with crop residue application, yields in conventional and reduced tillage systems are comparable after season 6. Nitrogen and phosphorus increased yield by up to 100% compared with control. Gross margins were not significantly different among the cropping systems being only 6 to 39% more in the legume–cereal systems relative to similar treatments in continuous cereal monocropping system. After 10 seasons of reduced tillage production, the economic benefits for our cropping systems are still not attractive for a switch from the conventional to reduced tillage.
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    Fertilizer nitrogen recovery as affected by soil organic matter status in two sites in Kenya
    (Springer, 2007) Karunditu, M.W.; Mugendi, Daniel N.; Kung’u, James; Vanlauwe, B.
    Management of nitrogen (N) nutrition is a vital aspect in maize production systems ofKenya. In Central andWestern parts of Kenya, high population density has eliminated the use of traditional fallow farming systems for replenishing soil fertility while high unevenly distributed rainfall increase chances of N leaching. A study was conducted at Maseno, and Kabete to investigate the fate of fertilizer N in the soil-plant system using treatments that had been receiving leaf prunings of Calliandra calothyrsus and Tithonia diversifolia. Two microplots were installed in the main treatments to which labelled fertilizer was applied. At the beginning and at the end of 2002 long rains, soil was sampled to 200 cm for N and 15N enrichment analysis at the two trials. Also at the end of the season plant samples were collected for N and 15N analysis. At Maseno trial, evenly distributed rainfall and the influence of organic resource quality enhanced good fertilizer nitrogen recovery in the maize crop. Also substantial nitrate movement down the soil profile was observed in the control followed closely by calliandra at the end of the 2002 long rains season. At Kabete trial recorded the poorest fertilizer N recovery due to unevenly distributed rainfall. Limited soil moisture reduced both soil and fertilizer N uptake which was reflected in high N in the top soil and low recovery in plant. Most of the nitrate-N was left in the tp soil as a result of low rainfall which couldn’t move it into the lower soil depths