Carbon and nutrient losses during manure storage under traditional and improved practices in smallholder crop-livestock systems - evidence from Kenya

In the absence of mineral fertiliser, animal manure may be the only nutrient resource available to smallholder farmers in Africa, and manure is often the main input of C to the soil when crop residues are removed from the fields. Assessments of C and nutrient balances and cycling within agroecosystems or of greenhouse gas emissions often assume average C and nutrient mass fractions in manure, disregarding the impact that manure storage may have on C and nutrient losses from the system. To quantify such losses, in order to refine our models of C and nutrient cycling in smallholder (crop-livestock) farming systems, an experiment was conducted reproducing farmers’ practices: heaps vs. pits of a mix of cattle manure and maize stover (2:3 v/v) stored in the open air during 6 months. Heaps stored under a simple roof were also evaluated as an affordable improvement of the storage conditions. The results were used to derive empirical models and graphs for the estimation of C and nutrient losses. Heaps and pits were turned every month, weighed, and sampled to determine organic matter, total and mineral N, P and K mass fractions. Soils beneath heaps/pits were sampled to measure mineral N to a depth of 1 m, and leaching tube tests in the laboratory were used to estimate P leaching from manure. After 6 months, ca. 70% remained of the initial dry mass of manure stored in pits, but only half of or less of the manure stored in heaps. The stored manure lost 45% of its C in the open air and 69% under roof. The efficiencies of nutrient retention during storage varied between 24–38% for total N, 34–38% for P and 18–34% for K, with the heaps under a roof having greater efficiencies of retention of N and K. Laboratory tests indicated that up to 25% of the P contained in fresh manure could be lost by leaching. Results suggest that reducing the period of storage by, for example, more frequent application and incorporation of manure into the soil may have a larger impact on retaining C and nutrient within the farm system than improving storage condition

Agroforestry as a climate change mitigation practice in smallholder farming:evidence from Kenya

The promotion of agroforestry as a mitigation practice requires an understanding of the economic benefits and its acceptability to farmers. This work examines the agroecological and socio-economic factors that condition profitability and acceptance of agroforestry by smallholder farmers in Western Kenya. We differentiate the use of trees according to the permanence of carbon sequestration, introducing a distinction between practices with “high mitigation benefits” (timber) and practices with “low mitigation benefits” (fuelwood). This study goes beyond the analysis of incentives to plant trees to identify incentives to plant trees that lead to high mitigation outcomes. We show that environmental factors shaping the production system largely drive the choice for planting trees with high mitigation benefits. Most trees in the area are used for fuelwood, and the charcoal economy outweighs economic factors influencing planting of trees with high mitigation benefits. Larger households tend to produce more fuelwood, while high mitigation uses are positively related to the education level of the household head, and to the belief that trees play a positive role for the environment. Where trees contribute significantly to incomes, the norm is that they are owned by men. We conclude that although agroforestry is not perceived to be more profitable than traditional agricultural practices, it plays an important economic and environmental role by supporting subsistence through provision of fuelwood and could relieve pressure upon common forest resources. In areas with high tree cover, it also represents a way of storing capital to deal with risks and cope with uncertainty

The use of woodland products to cope with climate variability in communal areas in Zimbabwe

Common lands provide smallholder farmers in Africa with firewood, timber, and feed for livestock, and they are used to complement human diets through the collection of edible nontimber forest products (NTFPs). Farmers have developed coping mechanisms, which they deploy at times of climatic shocks. We aimed to analyze the importance of NTFPs in times of drought and to identify options that could increase the capacity to adapt to climate change. We used participatory techniques, livelihood analysis, observations, and measurements to quantify the use of NTFPs. Communities recognized NTFPs as a mechanism to cope with crop failure. We estimated that indigenous fruits contributed to approximately 20% of the energy intake of wealthier farmers and to approximately 40% of the energy intake of poor farmers in years of inadequate rainfall. Farmers needed to invest a considerable share of their time to collect wild fruits from deforested areas. They recognized that the effectiveness of NTFPs as an adaptation option had become threatened by severe deforestation and by illegal harvesting of fruits by urban traders. Farmers indicated the need to plan future land use to (1) intensify crop production, (2) cultivate trees for firewood, (3) keep orchards of indigenous fruit trees, and (4) improve the quality of grazing lands. Farmers were willing to cultivate trees and to organize communal conservation of indigenous fruits trees. Through participatory exercises, farmers elaborated maps, which were used during land use discussions. The process led to prioritization of pressing land use problems and identification of the support needed: fast-growing trees for firewood, inputs for crop production, knowledge on the cultivation of indigenous fruit trees, and clear regulations and compliance with rules for extraction of NTFPs. Important issues that remain to be addressed are best practices for regeneration and conservation, access rules and implementation, and the understanding and management of competing claims on the common lands. Well-managed communal resources can provide a strong tool to maintain and increase the rural communities’ ability to cope with an increasingly variable climate

Population overlap and habitat segregation in wintering Black-tailed Godwits Limosa limosa

Distinct breeding populations of migratory species may overlap both spatially and temporally, but differ in patterns of habitat use. This has important implications for population monitoring and conservation. To quantify the extent to which two distinct breeding populations of a migratory shorebird, the Black-tailed Godwit Limosa limosa, overlap spatially, temporally and in their use of different habitats during winter. We use mid-winter counts between 1990 and 2001 to identify the most important sites in Iberia for Black-tailed Godwits. Monthly surveys of estuarine mudflats and rice-fields at one major site, the Tejo estuary in Portugal in 2005-2007, together with detailed tracking of colour-ringed individuals, are used to explore patterns of habitat use and segregation of the Icelandic subspecies L. l. islandica and the nominate continental subspecies L. l. limosa. In the period 1990-2001, over 66 000 Black-tailed Godwits were counted on average in Iberia during mid-winter (January), of which 80% occurred at just four sites: Tejo and Sado lower basins in Portugal, and Coto Dontildeana and Ebro Delta in Spain. Icelandic Black-tailed Godwits are present throughout the winter and forage primarily in estuarine habitats. Continental Black-tailed Godwits are present from December to March and primarily use rice-fields. Iberia supports about 30% of the Icelandic population in winter and most of the continental population during spring passage. While the Icelandic population is currently increasing, the continental population is declining rapidly. Although the estuarine habitats used by Icelandic godwits are largely protected as Natura 2000 sites, the habitat segregation means that conservation actions for the decreasing numbers of continental godwits should focus on protection of rice-fields and re-establishment of freshwater wetlands

Management intensity controls soil N2O fluxes in an Afromontane ecosystem

Studies that quantify nitrous oxide (N2O) fluxes from African tropical forests and adjacent managed land uses are scarce. The expansion of smallholder agriculture and commercial agriculture into the Mau forest, the largest montane forest in Kenya, has caused large-scale land use change over the last decades. We measured annual soil N2O fluxes between August 2015 and July 2016 from natural forests and compared them to the N2O fluxes from land either managed by smallholder farmers for grazing and tea production, or commercial tea and eucalyptus plantations (n = 18). Air samples from 5 pooled static chambers were collected between 8:00 am and 11:30 am and used within each plot to calculate the gas flux rates. Annual soil N2O fluxes ranged between 0.2 and 2.9 kg N ha− 1 yr− 1 at smallholder sites and 0.6–1.7 kg N ha− 1 yr− 1 at the commercial agriculture sites, with no difference between land uses (p = 0.98 and p = 0.18, respectively). There was marked variation within land uses and, in particular, within those managed by smallholder farmers where management was also highly variable. Plots receiving fertilizer applications and those with high densities of livestock showed the highest N2O fluxes (1.6 ± 0.3 kg N2O-N ha− 1 yr− 1, n = 7) followed by natural forests (1.1 ± 0.1 kg N2O-N ha− 1 yr− 1, n = 6); although these were not significantly different (p = 0.19). Significantly lower fluxes (0.5 ± 0.1 kg N ha− 1 yr− 1, p < 0.01, n = 5) were found on plots that received little or no inputs. Daily soil N2O flux rates were not correlated with concurrent measurements of water filled pore space (WFPS), soil temperature or inorganic nitrogen (IN) concentrations. However, IN intensity, a measure of exposure of soil microbes (in both time and magnitude) to IN concentrations was strongly correlated with annual soil N2O fluxes

Synthesis of chitosan oligomers/propolis/silver-nanoparticles composite systems and study of their activity against Diplodia seriata

The synthesis and characterization of composites of oligomeric chitosan with propolis extract which allow the incorporation of a third component (silver nanoparticles) are reported, together with their application in aqueous or hydroalcoholic solutions with a view to the formation of adhesive substances or nanofilms for the protection of vineyards against harmful xylophagous fungi. The antimicrobial properties of the association of the two biological products or those resulting from the incorporation of silver nanoparticles (NPs) are studied and discussed. The efficacy of the chitosan oligomers/propolis/silver NPs ternary system is assessed in vitro for Diplodia fungi. A preliminary study on the convenience of replacing propolis with gentisic acid is also presented

Conversion of natural forest results in a significant degradation of soil hydraulic properties in the highlands of Kenya

Land use change, especially conversion of native forests can have large impacts on water resources. Large scale conversion of native forests to agricultural land has occurred in the last few decades in the Mau Forest region. To quantify and understand landscape hydrologic responses, this study aimed at evaluating the effects of land use on soil infiltration, saturated hydraulic conductivity, bulk density, sorptivity, and soil moisture retention. A total of 136 plots representing five different land uses (native forest: n = 39, forest plantations: n = 14, tea plantations: n = 24, croplands: n = 23 and pasture: n = 36) were sampled in three catchments with similar parental material in the Mau Forest region, Western Kenya. Native forest topsoils (0–5 cm) had a bulk density of 1.0 ± 0.2 g cm−3 which was similar to values found for topsoils of forest plantations (1.1 ± 0.2 g cm−3), but significantly lower than topsoils from croplands (1.4 ± 0.2 g cm−3), tea plantation (1.3 ± 0.3 g cm−3) and pastures (1.4 ± 0.2 g cm−3). Similarly, soil infiltration rates were higher in native forest (76.1 ± 50 cm h−1) and in forest plantation (60.2 ± 47.9 cm h−1) than in croplands (40.5 ± 21.5 cm h‐1), tea plantations (43.3 ± 29.2 cm h−1) and pastures (13.8 ± 14.6 cm h−1). Native forest had the highest topsoil organic carbon contents (8.11 ± 2.42%) and field capacity (0.62 ±0.12 cm3 cm−3), while the highest permanent wilting point was recorded for pasture soils (mean of 0.41 ± 0.06 cm cm−3). The highest plant available water capacity was recorded for soils in native forest (mean of 0.27 ± 0.14 cm cm−3). Our study indicates that land use changes result in a significant degradation of soil hydraulic properties, which has likely resulted in changes of the regional water balance. Given the magnitude in which managed land use types have changed infiltration rates in our study area, we conclude that changes in land use types occurring in our study region in the last decades have already affected the hydrological regime of the landscapes and the compositions of flow components. The reduction in infiltration and hydraulic conductivity could result in increased surface run-off, erosion and frequency of flooding events