Soil Fertility Technologies Research Articles

Influence of soil fertility management technologies on phosphorus fractions, sorption characteristics, and use efficiency in humic Nitisols of Upper Eastern Kenya

Fractions of phosphorus (P) and its sorption characteristics are affected by different soil fertility (FM) technologies which ultimately affect crop growth and productivity. However, the response of P fractions and sorption characteristics to soil fertility technologies that integrate diverse amendments is still poorly understood in acidic Nitisols. A randomized complete block design was layout in an acidic Nitisol to determine fractions of P, its sorption characteristics and use efficiencies in acidic Nitisols under various FM technologies in field conditions. The use of minimum tillage + maize residue + inorganic fertilizer + goat manure (MTCrGF) had the highest impact on and significantly increased resin-Pi, NaHCO3-Pi, and maximum P sorption (Smax) by 182, 76, and 52 mg P kg−1. Moreover, NaOH-Pi and Smax concentrations were higher under conventional tillage + maize residue + inorganic fertilizer + goat manure (CTCrGF) by 216 mg P kg−1 and 49 mg P kg−1 than the control. MTCrGF and CTCrGF also had the lowest P bonding energy (0.04 L mg−1). CTCrGF had the highest P partial productivity factor (0.093 and 0.140 kg biomass kg−1 P) and P agronomic efficiency (0.080 and 0.073 kg biomass kg−1 P) during the two cropping seasons. The results demonstrate the positive influence of combining multiple P sources on soil P fractions, sorption characteristics, and use efficiencies. Notably, combining either conventional or minimum tillage with maize straw and applying integrated manure and inorganic fertilizer (MTCrGF or CTCrGF) can increase the labile P concentrations and reduce the potential depletion of the non-renewable rock phosphate and the use of inorganic phosphatic fertilizers for agricultural production.

Directions and reproduction soil fertility technologies in the post-war period in Ukraine

The article is devoted to the study of the military action's negative consequences on the soil fertility state in Ukraine and directions for their reproduction. The topic actuality is that a third of the arable agricultural lands were affected by military actions, which, taking into account the agrarian direction of production in the eastern and southern regions of Ukraine, threatens a significant decrease in the agricultural products' cultivation. The article aims to substantiate the effectiveness of technologies applied to overcome the affect of military activities on soil fertility reproduction in Ukraine. The study reveals the war negative consequences on the soil structure and properties and argues that it will take hundreds of years to reproduce naturally. The main types of warfare-induced disturbances to soil are defined and described: the soil structure modification (bombs craters, sealing, etc.) and chemical disturbances (pollutants input). Taking into account the existing experience of overcoming the military actions consequences in the agricultural soil reproduction, a certain procedure for reproducing the soil fertility with different degrees and causes of damage is proposed. The options for soil reproduction with a natural integrity of genetic horizons violation and methods of removing contamination with heavy metals (mechanical, physico-chemical, and biological) are considered. For the practical implementation of the proposed measures, an approximate costs' calculation of the soil fertility reproducing from the military actions consequences in Ukraine was made. It has been determined that for the reproduction of soil properties and their suitability for use in agricultural production, the greatest expenses (excluding humanitarian demining) are spent on mechanical melioration (81.8 %). However, the expenses amount depends on the number of shell explosion craters and their caliber, and the methods of reproduction the soil agrochemical properties. The peculiarities of legal regulation in soil conservation and the fertility protection, in determination of damage caused to lands and soils of Ukraine as a result of armed aggression against the country are indicated. The performed calculations will become key evidence in terms of damage amount compensation in lawsuits against the aggressor country. Key words: toxic elements, bombturbation, demining, basalt tuff, bioremediation, phytoremediation.

Stakeholder Involvement in Upscaling of Soil Fertility Research Output in Tharaka-Nithi County, Kenya

Food insecurity in Sub-Saharan Africa has prompted a lot of research in the development of soil fertility technologies; however, few of the recommendations from soil fertility management research have been put into use by the target end-users. The objective of the study was to investigate information exchange pathways used by researchers in upscaling of soil fertility in Maara and Mbeere South Sub-counties in Kenya. Structured questionnaires were used to collect information from 22 researchers and 240 farmers. Data was analyzed using descriptive statistics like frequency, mean, and percentages, while Chi-square, Kendal's correlation coefficient was used to test the magnitude of the relationship between dependent and independent variables. Inadequate resources materials and poor networking among stakeholders were among the challenges that the researchers faced in the dissemination of their research outputs. The findings also showed that there was a positive and significant correlation between farm size and the mass media approach. Researchers and extension agents should use a mixed approach; this is the use of combined individual, group, and mass media approaches to cater to the different preferences based on socio-economic characteristics of farmers.

Economic evaluation and socioeconomic drivers influencing farmers’ perceptions on benefits of using organic inputs technologies in Upper Eastern Kenya

Declining soil fertility in Sub-Saharan Africa (SSA) is a significant constraint towards increasing agricultural productivity. Soil fertility decline coupled with rapid population growth and low use of organic soil fertility technologies has threatened the population's economic status that lives in the rural area and relies on rain-fed agriculture. We conducted a cross-sectional household survey in the Central Highlands of Kenya (Gatanga and Meru South sub-counties) to determine farmers’ perception of the benefits of using organic resources technologies, socioeconomic drivers influencing their perceptions, and financial returns from the technologies. The selected technologies were; sole animal manure and a combination of animal manure with inorganic fertilizer. We based the benefits of using the selected soil fertility management technologies on four variables; potential to improve soil fertility, crop yields, profitability, and labor requirement. The majority of the farmers strongly agreed that using the selected technologies improved soil fertility, crop yields and were profitable. On the contrary, they agreed it was labor-intensive. Gender of the household head, household size, Tropical Livestock Unit (TLU), access to external labor, access to credit, total land cultivated, age, and years of farming experience were the socioeconomic drivers that significantly influenced farmers’ perception of the use of sole animal manure and animal manure combined with inorganic fertilizer. Results showed that animal manure had the highest financial returns of US$ 440.74 in Gatanga, while in Meru South, animal manure combined with inorganic fertilizer had the highest returns of US$ 456.25. The study highlights that the use of sole animal manure and animal manure combined with inorganic fertilizer is perceived positively by the smallholder farmers and has better financial returns than sole inorganic fertilizer. Thus, the use of selected organic resource technologies should be encouraged by creating more awareness through farmers’ training programs.

Integrated soil fertility management and household welfare in Ethiopia

Integrated Soil Fertility Management (ISFM) is a set of locally adapted soil fertility technologies and improved agronomic practices promoted to enhance soil fertility, crop productivity and incomes of smallholder farmers. While the suite of practices is site-specific, the use of improved seeds, organic and inorganic fertilizers constitute core ISFM technologies. ISFM is mostly related to higher input and labor demand, but there is little evidence whether these investments pay off at the household level. Using data from maize, wheat and teff growing farmers in two agroecological zones in Ethiopia, we assess whether the adoption of core ISFM technologies is associated with changes in household welfare, measured by total household income, food security and education. In addition, we look into resource allocation decisions within the household as potential drivers of welfare outcomes. We use the inverse probability weighting regression adjustment method. Results show that adopting ISFM core components for maize, wheat or teff is associated with higher labor demand as well as income obtained from these crops in both agroecological zones. Yet, only in one agroecological region, it also goes along with enhanced household income, food security and school enrollment. By contrast, in the other region, we find that technology adoption for at least one of the three crops is related to a reduced likelihood of engaging in other economic activities, pointing towards labor reallocation effects. We conclude that welfare outcomes of agricultural innovations can be heterogeneous depending on farmers’ income diversification strategies.

Adoption Intensity of Selected Organic-Based Soil Fertility Management Technologies in the Central Highlands of Kenya

Soil fertility decline continues to be a major challenge limiting agricultural productivity globally. Despite the novelty of organic-based technologies in enhancing agricultural production in Kenya's central highlands, adoption is low. Therefore, we carried out a cross-sectional household survey of 300 randomly selected smallholder farmers to determine the specific organic-based practices by farmers; and the socioeconomic factors that influence the adoption intensity of selected organic-based technologies. We used descriptive statistics to summarize the data and the Tobit regression model to evaluate the socioeconomic determinants of adoption intensity of selected organic-based technologies. We identified nine organic-based technologies that had different adoption rates among the farmers. The majority of the farmers had adopted manure (97%) and manure combined with fertilizer (92%) in Murang'a and Tharaka-Nithi, respectively. Manure was applied to the largest land in Murang'a with 31% of the cultivated land. In comparison, manure combined with fertilizer had the highest adoption intensity in Tharaka-Nithi applied to about 25% of the cultivated land. Gender, age of the household head, level of education, household size, access to external labor, training, Tropical Livestock Unit, agriculture group membership, access to credit, land cultivated, and farming experience influenced the adoption intensity of organic-based technologies among smallholder farmers. Based on the smallholder farmers' adoption behavior, this study can be used to disaggregate the farming households better in order to tailor specific organic-based soil fertility technologies solutions that meet their unique needs. One group would be those households that face specific constraints, as reflected in their low adoption rates, women-headed households and older farmers, and thus require more targeted / intensive efforts to overcome these barriers. The other group would be those households that require less focus because, when confronted with the technologies, they are more likely to adopt them easily, for example, the male-headed households. Hence, the smallholder farmers' adoption behavior, can enable policymakers to form a base for designing appropriate policies that encourage the adoption of organic-based soil fertility technology by smallholder farmers.

Accessibility and Reliability of Information Sources in Dissemination of Soil Fertility Management in Eastern Kenya

Increased recognition of soil fertility depletion as the main factor limiting crop production in many small holder farms in sub-Saharan African has renewed interest in the dissemination of soil fertility management technologies. Despite soil technology development and research outputs, few of the recommendations from various soil fertility management research activities have been adopted by the small-scale farmers on a large-scale level. Only a small proportion of allocated research resources is invested in dissemination among research institutions. The objective of the study was to investigate communication channels used in dissemination of soil fertility management practices in Mbeere and Meru South Districts. Two hundred and forty randomly selected farmers were interviewed. Data collected was analyzed using SPSS. The study revealed that 32.5% of the farmers who used combined organic and inorganic fertilizers received information from government extension officers while 41.3% of the farmers who use animal manure utilized their own farming experience. In disseminating soil erosion control measures, 51.2% of the farmers indicated that, farmer to farmer extension was the most commonly used. Also, 33.8% mentioned demonstration as the main method used in training soil fertility management practices. In general, the most common source of information was other farmers while there was least participation of researchers and agro input dealers in dissemination of soil fertility technologies. Thus, the study recommended more participation of stakeholders other than government extension officers as well as use of combined extension methods with farmer involvement in dissemination of soil fertility management practices. Keywords: manure, extension agents, farmer to farmer extension method, demonstration DOI: 10.7176/DCS/10-11-03 Publication date: November 30 th 2020

Multi-influencing-factors’ evaluation for organic-based soil fertility technologies out-scaling in Upper Tana Catchment in Kenya

Low adoption of soil fertility technologies, partially attributed to low technology out-scaling initiatives, is a critical hindrance to agricultural productivity enhancement of most smallholder farms in sub-Saharan Africa. Application of geospatial tools for spatial suitability evaluation of soil fertility management technologies can be a breakthrough in their promotion and out-scaling existing novel technological initiatives. The study objective was to develop a data-driven multi-influencing-factor (MIF) geospatial approach for out-scaling organic-resource based soil fertility management technologies. Using the developed geospatial approach, we delineated suitable zones for targeted out-scaling of organic resource technologies in the Upper Tana River (UTC) catchment in Kenya. We acquired multiple datasets from different sources and used them to prepare thematic layers. The factors used included rainfall, elevation, cattle density, bulk density, slope, soil pH, soil organic carbon, cation exchange capacity, drainage, and soil texture. The input layers were georeferenced, converted to raster formats, standardized to a range of 1 to 5, after which we generated the suitability map through a weighted overlay technique. The delineated suitability map showed that about 0.002% of UTR was least suitable, 4.7% marginally suitable, 38.5% moderately suitable, 34.7% medium-high suitable while 0.03% was highly suitable for organic resources out-scaling The results obtained indicate the potential of the geospatial approach as a scaling out methodology for organic-based soil fertility technologies. The suitability delineation established that Nyeri, Murang'a and Meru are the most suitable areas for the use of most organic resources in the Upper Tana catchment of the Central Highlands of Kenya. The suitability maps can inform policymakers, planners, and decision-makers in identifying the suitable sites for the use of organic-based soil fertility resources. Based on this study, we recommend the use of the developed a data-driven multi-influencing-factor (MIF) geospatial approach in the scaling out of the organic-based soil fertility technologies, not only in the study area but also other regions in sub-Saharan Africa.

The status of perception, information exposure and knowledge of soil fertility among small-scale farmers in Ghana, Kenya, Mali and Zambia

ABSTRACTPurpose: Soil fertility is decreasing in many parts of Sub-Saharan Africa. To mitigate this trend, various agricultural technologies are available, but their uptake by farmers has been low. Perception of the problem, information exposure, and knowledge play a major role in adoption of technologies. This study assessed empirically the levels of perception, knowledge and information exposure among African farmers as an indicator for potential adoption of soil fertility technologies.Design/Methodology/approach: The study used survey data of more than 2,400 small-scale farmers selected through random sampling from Ghana, Kenya, Mali and Zambia. The survey investigated socio-economic factors, exposure to media, perception and knowledge of soil fertility and other information.Findings: Many farmers did not perceive soil fertility as a major challenge, except in Mali; farmers were hardly receiving information on soil fertility from professional agricultural sources, and they often lacked accurate knowledge about soil fertility technologies. Radio was by far the most used information source for farmers.Practical implications: The study has exposed the need for interventions to increase awareness, information exposure, and knowledge about soil fertility among farmers to strengthen the adoption of soil fertility technologies. It also calls for innovative ways of strengthening extension services through links with radio.Theoretical implications: The role of communication in the uptake of agricultural innovations is still under-researched, and hence this study exposes the need to investigate in-depth knowledge, perception levels, and quality and frequency of information exposure on various channels of soil fertility management.Originality: This is one of the few studies empirically measuring perception, information frequency on various channels, and knowledge of soil fertility among small-scale farmers in African countries.

Reflections on Efforts Geared toward Improved Soil Fertility and Crop Yields in Kenya

A successful strategy aimed at enhancing crop productivity relies on its ability to be implemented practically in the field (farmers’ field). Many research-based activities and promising soil fertility technologies are largely not adopted. This paper examines the impact of the agricultural research conducted at the University of Eldoret, agricultural institutes and the government of Kenya projects at a farm level on crop yields. Precisely, this paper narrows down to research done with an aim of exploring system approaches that address soil phosphorus and its effect on increasing crop yields in Western Kenya. Strategies like the collaboration of scientists and non scientists (transdisciplinary process) produced successful results. A qualified soil test with differentiated soil testing recommendations increases the yield by about 1.5 t dry maize ha-1. Participating in a transdisciplinary process provides an additional surplus of about 1 t dry maize ha-1 yield. Economically, this is a highly attractive result; given that soil testing costs around 20 USD, a surplus of 1 t dry maize returns approximately 330 USD. Although literature registers success stories of many research work, there is slow and limited adoption rate of the output by farmers. We suggest the development and expansion of transdisciplinary research and creation of Farmer Research Network to seek a one-size-fits-all solution for farmers to adopt technologies with proven success.

Biophysical and socio-economic tools for assessing soil fertility: A case of western hills, Nepal

The middle mountain region of Nepal, which occupies some 30% of the total land, is the homeland of 45% of the total population, with agriculture being the main source of their livelihoods. Hill farming is primarily based on organic manure with livestock, forest and crops being major components of an integrated system. The aim of this study is to develop and promote improved methods for research and development organizations to identify cost-effective and appropriate soil fertility management strategies through; providing an improved understanding of the biophysical and socio-economic factors affecting the adaptability of sustainable soil management strategies in hillside systems, developing methodologies for evaluating soil fertility technologies and management systems for differently resource farmers in different farming systems, and strengthening the capability of local professionals in collaborating institutions to provide useful information to farmers. The work is placing emphasis on promoting cost-effective methods of soil fertility management, building on farmers' own knowledge and systems. Participatory techniques have been used for gaining a better understanding of fertility indicators, trends and existing soil management practices during 2000/01 in the western hills of Nepal. Farmers are now concerned that increasing amounts of chemical fertilizer at increasingly higher cost have to be applied, soils are becoming “harder” and production is declining. As a result farmers in four agro-ecological zones opted to either test methods for “improving” the quality of farm yard manure (FYM), or “improve” crop residue management. Early results show that through covering the FYM with black plastic sheets, yield increases of over 30% can be achieved. The use of participatory farm management techniques is providing a basis for local NGOs and farmers to evaluate their own experiments and develop soil fertility technologies and systems for their environments.DOI: http://dx.doi.org/10.3126/ajn.v1i0.7536 Agronomy Journal of Nepal (Agron JN) Vol. 1: 2010 pp.1-9

Impact of integrated agricultural research and development on adoption of soil fertility management technologies among smallholder farmers of Southern Africa

This paper sets out to determine the impact of Integrated Agricultural Research for Development in three selected countries of Southern Africa. Agricultural productivity in Southern Africa faces several challenges, of which poor soil fertility strikes out as the priority problem inhibiting increased productivity in farmers’ fields. While several soil fertility management technologies are being promoted in the region, their uptake by smallholder farmers remains very low. In order to mitigate the challenges that African countries are facing in agricultural production, Forum for Agricultural Research in Africa (FARA) through Sub Saharan Africa Challenge Programme (SSA CP) introduced Integrated Agricultural Research for Development (IAR4D) as an institutional innovation designed to promote agricultural productivity through the adoption of appropriate technologies. Two data sets collected through questionnaire survey at the beginning of the SSA CP project and at the end of the project are used in this paper. Local average treatment effect is used to measure the impact of IAR4D on adoption of integrated soil fertility management technologies. Study findings show that after two years of implementing IAR4D, adoption of soil fertility technologies improved in one of the projects being implemented. Otherwise, IAR4D had an insignificant impact on adoption of soil fertility management technologies in all the three participating countries. Local average response functions shows that socioeconomic factors are more important in influencing adoption than participating in research. Key words: Innovation, action research, agriculture, fertility, adoption, Southern Africa.

Production efficiency and economic potential of different soil fertility management strategies among groundnut farmers of Kenya

This paper provides the economic evaluation of different soil fertility replenishing technologies (use of inorganic fertilizers, organic manure, and rhizobium inoculant) that were tested during field studies and recommended to groundnut farmers. Data on soil fertility technologies used by households, groundnut yields, and resource use and farm and farmers characteristics were collected through administration of a questionnaire to a sample of 332 farmers from three districts of western Kenya. The data was analyzed to determine whether adoption of the technologies would increase household incomes and production efficiency. Benefits and costs of each technology were computed through the use of budgets. Technical and allocative inefficiencies are investigated by fitting a Cobb-Douglas production function. The technical efficiency of the farmers varied between 0.56 and 0.69 while labor allocative efficiency varied between 0.81 and 0.93. Farmers applying organic fertilizers only were technically more efficient but had lower potential yield compared to farmers who applied inorganic or a combination of organic and inorganic fertilizers. Use of inorganic fertilizers lead to a benefit cost ratio of up to 3:1. Organic manure had the lowest benefit-cost ratio (2.2:1) even when compared with that obtained when farmers did not apply any fertility replenishing input resulting from high cost of labor required to use this technology. There is a high potential for farmers to increase their groundnut yields and incomes by improving on production efficiency and by fertilizing their groundnut farms. Key words: Cost-Benefit ratios, Groundnuts, Kenya, Production efficiency, Production function

Nitrogen fixation and biomass productivity of indigenous legumes for fertility restoration of abandoned soils in smallholder farming systems

Most legume-based soil fertility technologies often fail to make the desired impact on nutrient-depleted soils partly due to low N2-fixation rates and poor biomass productivity. A study was conducted in the 2004/05 and 2005/06 rainfall seasons to evaluate biomass productivity and N2-fixation of indigenous legumes on nutrient-depleted fields under low (450- 650 mm yr−1) to high (> 800 mm yr−1) rainfall areas of Zimbabwe. Legume species, mostly of Crotalaria, Indigofera and Tephrosia genera, were sown in mixtures on disturbed soil. Indigenous legume fallows (indifallows) produced 2–5 t biomass ha−1 under low and 5–15 t biomass ha−1 under high rainfall. They significantly (P<0.05) out-yielded natural fallows by 84% and a sunnhemp (Crotalaria juncea) green manure fallow by 32% over a growth period of six months. Cumulatively, indifallows produced more biomass (~29 t ha−1) than natural fallows (~ 8 t ha−1) over two seasons. Indigenous legumes derived 61–90% of their N from the atmosphere with amounts fixed ranging from 2–57 kg N ha−1 under medium rainfall conditions to 1–173 kg N ha−1 under high rainfall. Application of P increased indifallow biomass productivity by 15% under low rainfall, and N2-fixation by 32% and 18% under low and high rainfall, respectively. These results demonstrated that indigenous legumes generate sufficiently high biomass and fix nitrogen on nutrient-depleted fields where most conventional green manure and grain legume cultivars often fail to establish.

User Acceptability of Sustainable Soil Fertility Technologies: Lessons from Farmers' Knowledge, Attitude and Practice in Southern Africa

ABSTRACT Low soil fertility is one of the greatest biophysical constraints to agricultural production in sub-Saharan Africa. “Improved fallow,” an agroforestry-based soil fertility replenishment technology was developed in response to the depletion of soil fertility and increasing difficulty of small-scale farmers to afford mineral fertilizers. The biophysical performance of the technology to improve soil fertility and increase crop yield has been well demonstrated and efforts are being made to enhance the adoption its adoption by farmers. There is relatively little information and systematic feedback regarding farmers' perception and knowledge of the technology. Using data collected from a stratified sample of 302 farmers in Zambia, this study analyzed farmers' knowledge, attitudes, and perceptions of soil fertility and food security problems, highlighting implications for user acceptability and the development of sustainable soil fertility management technologies. Results show that farmers have good understanding of soil fertility issues, its linkage to food security and household welfare indicators. They appreciate improved fallow because it responds to the critical problems of low soil fertility and provides additional benefits to the household. However, there are some challenges to the widespread uptake of the technology including land constraints, property rights availability of seeds, and knowledge-intensive nature of the technology. Farmer acceptability and improved adoption of the technology will be influenced by the extent to which efforts are taken to meet these challenges. Farmers' response on knowledge, attitude, and perception provides valuable inputs for further development and modification of the technology. Beyond technology development, an understanding of farmers' preference and other contextual issues-within which the technology is expected to be adopted-will enable researchers to develop appropriate sustainable technologies and enhance user acceptability of the same. The study shows that technical characteristics are important but not exclusive conditions for farmers' acceptability and adoption of good agricultural technologies by farmers.

Soil fertility Status, Management, and Research in East Africa

This study reviews and synthesizes the soil fertility status, management among smallholder farmers and research in the three countries of east Africa, namely Kenya, Tanzania and Uganda. We observe that many studies note the declining soil fertility, mainly due to soil fertility mining, putting crop production in an unsustainable path. Studies have shown that the current soil fertility management practices of recycling crop residue; biomass transfer; short fallow and other organic practices appear to be inadequate to replenish the nutrient outflow. Consequently, a number of case studies have shown crop yield decline in the region. Soil fertility research in east Africa has concentrated on producing recommendation for monocrop systems while most smallholder farmers plant crops in complex intercropping and mixed cropping systems. Additionally even though agricultural prices and soil characteristics are dynamic, recommendations are always based on static input-output price ratio and soil conditions. This research approach and assumptions render many recommendations irrelevant to smallholder farmers. Consequently, adoption of soil fertility technologies in the region is low, even though many farmers appreciate the benefits of these technologies. The need to revise the current soil fertility recommendation such that they take into account the dynamic nature of soils and agricultural prices is apparent. Key words: East Africa, fertilizer recommendations, trials and use, nutrient mining, soil fertility Eastern African Journal of Rural Development Vol.20(1) 2004: 94-112

Farmers' taxonomies as a participatory diagnostic tool: Soil fertility management in Chihota, Zimbabwe

Soil infertility is a major constraint to food production in the communal areas of Zimbabwe. Smallholders in the region recognize the problems of low soil fertility and have devised ways of coping with them. This study describes the use of farmers' taxonomies of themselves and their soils to identify and understand the options they have, and the constraints they face in managing poor soil fertility in Chihota, a sub-humid communal area of north central Zimbabwe. It is part of an effort by a group of agricultural researchers and extensionists working on improved soil fertility technologies, to better integrate their work with farmers in order to expose the latter to promising technologies, get feedback on the technologies merits and feasibility, and help farmers experiment with them. The results show that these farmers have relatively sophisticated taxonomies, which provide a good picture of the resources, constraints, and concerns they have about soil infertility and ways to manage it. The taxonomies are an important framework for integration of technical interventions with farmers' requirements, systems, and circumstances.

Note on phosphorus and cultivar enhancement of biological nitrogen fixation and productivity of maize/bean intercrops in Malawi

Little attention has been given to soil fertility technologies for maize ( Zea mays L.)/bean ( Phaseolus vulgaris L.) intercrops common in Africa, and yields and bean biological nitrogen fixation (BNF) remain perpetually low. This study investigated the effect of 30 kg ha −1 P fertilizer and improved bean cultivars on intercrop yields and bean BNF (measured by the N-difference method) at two sites with nutrient deficient soils typical of high altitude cropping systems in Malawi. Following farmer practice, maize was the dominant crop of the intercrop and bean a low density `bonus' crop. Phosphorus application to the maize/bean intercrop consistently enhanced maize and bean yields and BNF. Yields of the improved cultivars were about 150% higher than farmer cultivars at both 0 and 30 kg P ha −1. BNF was increased by about 90% in improved cultivars compared to farmer cultivars, with the exception of one site in 1996/97. A trial conducted at nine sites on-farm was used to evaluate a fertilizer strategy of P (30 kg ha −1) and N (30 kg ha −1) applied to a maize/bean intercrop versus sole maize. Yields and economic evaluation indicated high mean net benefits for an average cost/price scenario for fertilizer application to maize/bean intercrop: net benefit was US$192 ha −1, compared to unfertilized sole maize, net benefit US$62 ha −1. Net benefit for fertilizing sole maize was US$86 ha −1. Fertilizing maize/bean intercrops is a promising technology for smallholder farmers in upland, P-deficient soils, in areas where beans as a sole crop are not valued sufficiently to be fertilized by subsistence farmers.