Robert J. Delve

Organic inputs for soil fertility management in tropical agroecosystems: application of an organic resource database

Organic resources play a critical role in both short-term nutrient availability and longer-term maintenance of soil organic matter in most smaller holder farming systems in the tropics. Despite this importance, there is little predictive understanding for the management of organic inputs in tropical agroecosystems. In this paper, an organic resource database (ORD) is introduced that contains information on organic resource quality parameters including macronutrient, lignin and polyphenol contents of fresh leaves, litter, stems and/or roots from almost 300 species found in tropical agroecosystems. Data on the soil and climate from where the material was collected are also included, as are decomposition and nutrient release rates of many of the organic inputs. Examples of uses of ORD are provided in the paper: (1) nutrient contents (including median values and ranges) and other resource quality parameters of farmyard manure and crop residues are compared to that of alternative nutrient sources such as different plant parts and plant types; (2) nutrient stocks found in farm boundary hedges are estimated and evaluated as a source of nutrients for soil fertility management; (3) hypotheses regarding the indices and critical values of N, lignin, and polyphenol contents for predicting N release rates are tested; (4) organic materials for soil fertility management experiments are selected. This database, when coupled with models and decision support tools, will help advance organic matter management for soil fertility improvement from an empirical to a predictive practice.

Implications of livestock feeding management on soil fertility in the smallholder farming systems of sub-Saharan Africa

The role of livestock in nitrogen cycling in mixed crop‐livestock farming systems of sub-Saharan Africa was explored. Cattle were fed a range of diets to investigate the effects on partitioning of nitrogen between urine and faeces and on the chemical composition of the manures produced. The trade-offs in efficiency between using the feed resources as a direct soil amendment for crop production compared with feeding to livestock and use of the manure as a fertiliser are discussed. Increased dry matter (DM) and nitrogen intake of a poor quality basal diet (barley straw) was achieved by supplementation with 15 and 30% of DM offered as Calliandra calothyrsus, Macrotyloma axillareor poultry manure. Urinary-N excretion for the basal diet (0.5 mg kg 1 liveweight (W) per day) was similar to C. calothyrsus at 15 and 30% supplementation (1.3 and 0.8 mg kg 1 W per day, respectively) and M. axillare at 15 and 30% supplementation (0.4 and 0.6 mg kg 1 W per day, respectively). In contrast, feeding poultry manure, a supplement containing highly degradable N, resulted in larger excretions of excess rumen ammonia as N in the urine, 17.5 and 23.2 mg kg 1 W per day for 15 and 30% supplementation, respectively. Diets containing the largest rate of C. calothyrsus supplementation had the lowest digestibility of N in the acid detergent fibre (ADF) and neutral detergent fibre (NDF) fractions. This was reflected in faeces from cattle fed diets supplemented with C. calothyrsus, which had substantially greater amounts of N bound to fibre (ADF and NDF) fractions than faeces from the other diets. When incubated in leaching tubes prunings of C. calothyrsus showed net N mineralisation from week 2, whereas barley straw, M. axillare and poultry manure immobilised N for >28, 24 and >28 weeks, respectively. Faeces derived from supplementation with C. calothyrsusand M. axillare resulted in shorter nitrogen immobilisation in leaching tubes (16 weeks) than supplementation with poultry manure (24 weeks) when compared with faeces derived from animals fed straw only (28 weeks). Similarly, reduced N uptake from 10-week-old maize plants was observed in pots to which faeces had been added compared with the control treatment. A second crop of maize had increased N uptake. Feeding poor quality crop residues like barley straw to animals produces manures with a decreased capacity to immobilise mineral N in the soil. This was shown

Challenges and lessons when using farmer knowledge in agricultural research and development projects in Africa.

Farmer participatory research (FPR) approaches are now considered mainstream and are especially applicable for developing appropriate technology options in complex, diverse and risk-prone regions, where local adaptations are crucial. Although the advantages of using farmer knowledge to guide scientific research are numerous and well documented, the challenges and potential pitfalls that befall biophysical researchers, in particular, when using FPR approaches have received much less attention, especially in sub-Saharan Africa. Our experiences show that in certain cases, the methods used to collect farmer knowledge are flawed, leading to inaccurate or incomplete information being gathered. This potentially leads to the development and promotion of unsustainable, unprofitable or socially unacceptable technologies. This paper uses a series of examples to illustrate that discrepancies between farmer and researcher observations may occur because (i) farmers and scientists may not have sufficient insight into the systems complexity, (ii) farmers and scientists use different reference frameworks, and (iii) methodological errors may lead to farmers intentionally or unintentionally providing false or ‘desired’ information to achieve (short-term) benefits. This paper concludes by providing guidelines to improve the integration of farmer and scientific knowledge in order to develop appropriate technology options that are both environmentally sound and adaptable to local conditions.

Drivers of land use change and household determinants of sustainability in smallholder farming systems of Eastern Uganda.

Smallholder farming systems in sub-Saharan Africa have undergone changes in land use, productivity and sustainability. Understanding of the drivers that have led to changes in land use in these systems and factors that influence the systems’ sustainability is useful to guide appropriate targeting of intervention strategies for improvement. We studied low input Teso farming systems in eastern Uganda from 1960 to 2001 in a place-based analysis combined with a comparative analysis of similar low input systems in southern Mali. This study showed that policy-institutional factors next to population growth have driven land use changes in the Teso systems, and that nutrient balances of farm households are useful indicators to identify their sustainability. During the period of analysis, the fraction of land under cultivation increased from 46 to 78%, and communal grazing lands nearly completely disappeared. Cropping diversified over time; cassava overtook cotton and millet in importance, and rice emerged as an alternative cash crop. Impacts of political instability, such as the collapse of cotton marketing and land management institutions, of communal labour arrangements and aggravation of cattle rustling were linked to the changes. Crop productivity in the farming systems is poor and nutrient balances differed between farm types. Balances of N, P and K were all positive for larger farms (LF) that had more cattle and derived a larger proportion of their income from off-farm activities, whereas on the medium farms (MF), small farms with cattle (SF1) and without cattle (SF2) balances were mostly negative. Sustainability of the farming system is driven by livestock, crop production, labour and access to off-farm income. Building private public partnerships around market-oriented crops can be an entry point for encouraging investment in use of external nutrient inputs to boost productivity in such African farming systems. However, intervention strategies should recognise the diversity and heterogeneity between farms to ensure efficient use of these external inputs.

Participatory Photography as a Qualitative Approach to Obtain Insights into Farmer Groups

Participatory methods and visual tools are increasingly popular as qualitative approaches for enriching and complementing quantitative survey tools for understanding livelihoods and assessing and documenting impacts of development projects. However, the use of visual tools for analyzing and documenting social processes is still in its infancy. This article reports on an innovative attempt in adopting existing methods of using disposable cameras to stimulate interviews and focus group discussions with groups of smallholder farmers and to obtain new insights into farmer group dynamics and social capital of groups.

The Dynamics of Social Capital in Influencing Use of Soil Management Options in the Chinyanja Triangle of Southern Africa

Social capital has become a critical issue in agricultural development as it plays an important role in collective action, such as, management of common resources and collective marketing. W hilst literature exists on the role of social capital in the use and adoption of improved agricultural technology, such literature is fraught with issues of the measurement of social capital beyond membership of farmers in groups. W e hypothesiz ed that different types of social capital influence the adoption of soil management options differently. This study looked at the measurement of social capital, differentiating between the main types of social capital and employed factor analysis to aggregate indicators of social capital into bonding, bridging, and linking social capital. Using logit analysis, the role of these types of capitals on influencing use of different soil management options was analyz ed. The study found that bonding, bridging, and linking social capital all influence the adoption and use of different soil management options differently, a trend that might be similar for other agricultural technologies as well. The study recommends more research investments in understanding the differentiated outcomes of these forms of social capital on use and adoption of technologies to further guide agricultural interventions.

Contending with Complexity: The Role of Evaluation in Implementing Sustainable Natural Resource Management

Three case studies show that natural resource management (NRM) research aimed at sustainably improving the well-being of African small-holder farmers is complex, and that monitoring and evaluation (M&E) is an essential tool in coping with this complexity, supported by an ‘innovation systems’ view of the adoption process. In the case studies, researchers adjusted their activities and outputs on the basis of learning from M&E. Many of the insights came through identifying farmer innovations, which also proved a source of improvements to the respective technologies. Together, better understanding and iterative improvements made eventual widespread impact more likely. Farmers also learnt from M&E exercises and this learning facilitated adoption. The understanding of the early adoption process provided by M&E can provide a foundation for more plausible impact assessment.

Gender equity and social capital in smallholder farmer groups in central Mozambique

This case study from Búzi district, Mozambique investigated whether gender equality, in terms of male and female participation in groups, leads to gender equity in sharing of benefits from the social capital created through the group. Exploring the complex connection between gender, groups, and social capital, we found that gender equity is not necessarily achieved by guaranteeing men and women equal rights through established by-laws, or dealing with groups as a collective entity. While there were no significant differences in the investment patterns of men and women in terms of participation in group activities and contribution of communal work, access to leadership positions and benefits from social capital were unequally distributed. Compared with men, women further found it difficult to transform social relations into improved access to information, access to markets, or help in case of need.

Determinants of Fertiliser Use by Smallholder Maize Farmers in the Chinyanja Triangle in Malawi, Mozambique and Zambia

Abstract Farm surveys in Malawi, Zambia and Mozambique were carried out to assess the determinants of fertiliser use given continued low yields, low organic matter and general poor soil health in southern African soils. Regression modelling showed that fertiliser use was influenced by household and farm characteristics. In addition, it was also influenced by social and human capital and farmers’ perceptions of the effect of fertilisers on soil fertility. Farmers who perceived fertilisers as bad for their soil were less likely to adopt their use. This is a key result, as the emerging discussions on a green revolution for Africa, as well as the continued food crisis discussion, are prompting increased fertiliser use as an immediate intervention for increasing nutrient inputs into agriculture in the developing world. Increased policy efforts should be placed not only on increasing access to fertilisers but also on evolving farmers’ perceptions and attitudes towards fertiliser use.

Decomposition and Nutrient Release from Intra-specific Mixtures of Legume Plant Materials

Abstract Because farmers use mixtures of leaves and stems as a soil amendment, data of leaves, stems, and a leaf/stem mixture of Indigofera constricta and Mucuna pruriens from a 20‐week litterbag study were analyzed to assess their decomposition, nutrient release, and possible interactions within mixtures. Decomposition and nitrogen (N)–release patterns were leaves≥mixtures≥stems, whereas phosphorus (P)–release patterns were the opposite (P<0.05). Leaves released 110–130 Kg N ha−1, and mixtures released 30% less. A similar ratio was obtained for P release. This suggests that nutrient release from leaf/stem mixtures is overestimated when only leaves are considered. Decomposition and nutrient‐release patterns of mixtures occasionally differed from estimated patterns by 2–5% (P<0.05), indicating that minor interactions took place. However, estimations based on the amount of released nutrients generally showed non significant interactions. This suggests that the impact of low‐magnitude interactions within mixtures during its decomposition on soil fertility are negligible when considering total nutrient release.