Rotation of Sesbania sesban (L.) Merr., a fast-growing N2-fixing tree, with maize (Zea mays L.) has potential for increasing fertility of tropical soils, where fertilizer use by resource-poor farmers is limited. At two sites in Kenya (Ochinga, with a Kandiudalfic Eutrudox soil, and Muange, with a Kandic Paleustalf), we compared maize yields and financial returns for (i) sesbania grown for three or four seasons followed by three maize crops (sesbania fallow), (ii) one maize crop followed by natural regrowth of vegetation for three seasons and then three maize crops (natural fallow), and (iii) maize monoculture for seven seasons. After the fallows, plots were split with and without added P. Maize responded to P at both sites. Cumulative grain yields for seven seasons of maize monoculture were 8.4 Mg ha1 at Ochinga and 5.6 Mg ha1 at Muange. They were comparable to cumulative maize yields for sesbania fallow (Ochinga, 10.6 Mg ha1 Muange, 4.5 Mg ha1) and natural fallow (Ochinga, 7.7 Mg ha1; Muange, 4.2 Mg ha1), even though maize was grown for only three or four seasons in the fallow treatments. Sesbania fallow was financially attractive at Ochinga (500 mm rain in each season) but not at Muange, where low rainfall (<300 mm in each posffallow season) limited maize yield. Phosphorus fertilization of maize at Ochinga increased (P < 0.2) net benefit for sesbania fallow. Improved fallows have potential to supply nutrients to crops, but they are unlikely to eliminate the need for P fertilizers on P-deficient soils.
Tag: fertilizers
Phosphorus availability and maize response to organic and inorganic fertilizer inputs in a short term study in western Kenya
The use of organic materials as P sources is of considerable interest in smallholder farming systems in tropical Africa, mainly because of their potential as alternatives to inorganic P fertilizers. Field studies conducted in a Nitisol of western Kenya in 1995 (crop 1) and 1996 (crop 2) compared effects of organic and inorganic fertilizers on resin extractable P availability (Pext) and maize (Zea mays L.) yield (MY). Leaf biomass and small twigs of Tithonia diversifolia, Croton megalocarpus, Lantana camara L., Senna spectabilis, Calliandra calothyrsus, and Sesbania sesban, were applied at 5 Mg ha1 (DW), supplying an estimated 9–15 kg P ha1 and 30–212 k N ha1. The inorganic fertilizer was triple superphosphate (TSP), applied at 0 (control), 10, 25, 50, and 150 kg P ha1 with each plot receiving 120 kg N ha1 as urea. All plots received a blank application of 100 kg K ha1 as potassium chloride. Between 92 and 98% (P<0.001) of the variation in Pext was explained by the P added (Padd) from the amendments. Response of MY to Padd was best described by logarithmic function as: Full-size image (<1 K) (R2=0.91) for crop 1, and Full-size image (<1 K) (R2=0.90) for crop 2. Response of MY to Pext was best described by a linear function with R2 ranging from 0.84 to 0.89 for crop 1, and 0.76 to 0.81 for crop 2. Effects of Tithonia and Croton on MY were similar to effects of 50 kg P ha1+120 kg N ha1 as inorganic fertilizer. Although the confounding effects of nutrients other than P in the organic materials on MY were isolated, it appears that reasonable MY can be achieved if adequate amounts of high quality organic materials such as Tithonia and Croton are used as P sources. A term, ‘phosphorus availability index’ (PAI), calculated as: (Pext treatmentsPext control)/P added, was introduced to describe the P availability capacity of the amendments. The PAI values suggested a greater propensity for net P mineralization following addition of all organic materials (except S. spectabilis) than for the inorganic amendments. The PAI results indicate that improvements of soil Pext can come from either P released from organic inputs or increased availability of native soil P following addition of organic and inorganic fertilizers.
Contributions of agroforestry research to livelihood of smallholder farmers in Southern Africa: 1. taking stock of the adaptation, adoption and impact of fertilizer tree options
Agroforestry practies involving fertilizer trees managed in sequential and simultaneous tree-crop systems are key to achieving sustainable food production in Southern Africa as they offer a wider scope for resource-stressed farmers to produce sufficient food for consumption and markets, even where land scarcity and soil fertility are major constraints. In these systems, maize yields have generally increased from less than a tonne per hectare to two or more tonnes, in Malawi, Tanzania, Zambia and Zimbabwe and they have been shown to be comparable to fertilized fields. Application of micro doses of inorganic fertilizers (especially N) in tree-crop systems has generally increased the synergy in nutrient availability thereby producing higher maize yields than unfertilized maize. Fertilizer tree systems are more productive and economically more profitable than unfertilized maize system and the economic impact is high, estimated at US
Agroforestry can improve food security, farm diversification and income generation in Zambia
Fifteen years of research and development work by the World Agroforestry Centre (ICRAF) and its partners in Zambia have refined agroforestry technologies that can have a huge impact on food security and income generation at low cost and while protecting the environment. Current policies are failing to take advantage of these new technologies. Minor policy changes could bring about much greater adoption of these proven technologies with major benefits to farmers and the Zambian economy.
Adoption of agroforestry and the impact on household food security among farmers in Malawi
Agroforestry is increasingly regarded as an important adaptation and mitigation strategy against climate change. In particular, the use of fertilizer trees has been promoted as a practice that contributes to improved soil fertility through nitrogen fixation, by increasing supply of nutrients for crop production. While a lot of the evidence on the impact of fertilizer trees relies on on-farm experiments and correlational analysis, there is a paucity of rigorous evidence under actual smallholder farming conditions. This paper analyzes the impacts of adopting fertilizer trees such as Gliricidia sepium and Faidherbia albida on household food security. We draw on survey data of 338 farmers in Malawi and use an endogenous switching regression to rigorously analyze adoption impacts. Econometric results show that use of fertilizer tree adoption increases the value of food crops by 35%. Disaggregation of the impacts through stratification by land ownership further reveal that farmers with smaller farms of up to 2 acres realize the highest gains. Furthermore, fertilizer tree use in conjunction with improved maize seed also significantly increased value of food crops. This study offers preliminary insights that contribute to an emerging field of research on quantitative assessment of agricultural interventions such as agroforestry practices using novel analytical approaches. We provide some policy insights and recommend the need for future research to be designed around development initiatives that consider fine-scale variation in social, economic and ecological context of farmers to improve uptake and adaptation to realize the full potential of agroforestry in improving soil fertility and household food security.
Tillage and fertilizer effect on maize and soybean yields in the Guinea savanna zone of Ghana
Background: The most limiting factors for sustainable maize production in smallholder farming systems of sub-Saharan Africa, especially the savanna agro-ecological zone, are erratic rainfall pattern and low soil fertility. Methods: Research was conducted with smallholder farmers in 2013 and 2014 in two communities in the Upper West Region of Ghana to evaluate the effects of NPK mineral fertilizer (64-38-38 kg ha-1 N-P2O5-K2O, respectively) on growth and yield of maize at Bompari, and 375 kg ha-1 of YaraLegume™ fertilizer (0-18-13 NPK + 3 CaO + 2 MgO + 4 S) on growth and yield of soybean at Doggoh, under no-tillage (using pre-plant application of glyphosate) and conventional tillage (using hand hoe). Results: Mean grain yields of both maize and soybean were higher in 2014 than 2013. In both years, no-tillage and conventional tillage had similar effect on soybean plant height, pods per plant and aboveground dry matter production. Averaging over fertilizer treatment, grain yield of no-tillage soybean was 51% higher when compared with tilled soybean in 2014 only. Mean grain yield of no-tillage maize was 68% higher than that of tilled maize in 2013 only. Regardless of tillage method, fertilizer application significantly increased maize and soybean grain yields. Application of fertilizer to soybean resulted in 59% (193 kg ha-1) and 54% (474 kg ha-1) increase in grain yields in 2013 and 2014, respectively, over no fertilizer treatment. Mean grain yield of maize was 140 and 252% higher with fertilizer treatment in 2013 and 2014, respectively. No-till system showed cost savings due to reduced labour mainly for weed control. Conclusion: The results of these studies showed that no-tillage with fertilizer, whether for maize or soybean, generally resulted in the highest grain yields. No-tillage also gave the highest economic returns. Farmers can get better returns to the money invested in herbicide for producing maize and soybean under no-till than with their traditional practice even on degraded savanna soils with low levels of plant available nutrients. © 2017 The Author(s).
Participatory evaluation of integrated pest and soil fertility management options using ordered categorical data analysis
Maize is becoming the major food crop around Lake Victoria. Major constraints to its production are Striga, stem borer, and declining soil fertility. Innovative integrated technologies have been developed: the’push-pull’ system (intercropping with Desmodium and surrounded by Napier grass), soybean and Crotalaria rotations, and imidazolinone-resistant (IR) maize seed. In 12 demonstration trials in four villages in Siaya and Vihiga districts (Kenya) and two villages in Busia (Uganda) in 2003 and 2004, 504 farmers evaluated all cropping systems and a mono-cropped continuous maize, each cropped with IR or local maize, and supplemented or not with fertilizer, totaling 16 treatments. Farmers evaluated all treatments for yield, resistance to Striga and stem borer, improvement of soil fertility, and provided an overall evaluation score, using an ordered scale of 1 (very poor) to 5 (very good). Data were analyzed using ordinal regression, estimating log odds ratios. The results show significant preferences for all treatments over the control. Push-pull with IR and fertilizer had the highest log odds ratio (2.93), so the odds of farmers preferring this treatment are 18.7 times the odds that farmers prefer the control. The odds ratios for the other push-pull combinations were generally highest (9-15), followed by the rotation systems with Crotalaria (3.5-7.0), and soybeans, especially with IR maize and fertilizer (odds ratio of 5.7). In mono-cropping systems, IR maize was only appreciated in combination with fertilizer, and then only in 2004. Push-pull and Crotalaria were more appreciated in 2004 than in 2003. Farmers in Vihiga had a stronger preference for push-pull, and those in Busia for soybean rotations. Significant differences among farmers were observed, but the effects were small. Women appreciated push-pull more than men, while other technologies were gender-neutral. Older farmers were more likely to prefer push-pull and Crotalaria with fertilizer. Livestock ownership was not found to have an effect on technology preferences. Measured yield, stem borer and Striga infestation all had significant but small effects, although their inclusion did not eliminate the treatment effects, indicating that other factors are still important. OLS of the scores for different criteria on the overall score shows yield to be the most important criterion (coefficient of 0.40), followed by soil fertility enhancement (0.25) and Striga resistance (0.13). Labor saving (0.09) and stem borer resistance (0.03) are relatively minor criteria. This research shows that scoring and analysis with ordinal regression is a convenient way to solicit and analyze farmers’ preferences for new technologies, with wide applicability in farming systems and participatory research. Its application here shows that farmers like the new technologies, especially push-pull, but that there are substantial differences between years, sites and farmers. The use of this method can be very helpful to define and focus further research and formulate specific and targeted recommendations for agricultural extension.
Replicable tools and frameworks for bio-carbon developments in West Africa
This working paper is intended to help countries in West Africa, and local communities and farmers to adopt climate-smart land management practices that enhance carbon sequestration. Abating greenhouse gas emission from land use should not, in the African context, limit a community’s development. Hence, promoting a High Value Biocarbon community of practice should first address the livelihoods of inhabitants through increased socioeconomic development opportunities. The document highlights the importance of interventions like agroforestry in attaining good quality and quantity of products by highlighting the significance of growing fruit and vegetable trees, nitrogen-fixing trees against heavy fertilizer usage, protection of standing biomass, utilization of improved wood energy stoves and land restoration. The substantial amount of information and data required to execute each of the projects are given in detail in this working paper, together with the socioeconomic and environmental benefits, costs incurred, monitoring requirements, proposed management schemes and capacity building. The rates of success of the projects can be measured by conducting carbon inventories, estimating the amount of carbon dioxide emissions released, and carrying out surveys among locals to ascertain the quality and quantity of produce and market values. The challenges and barriers experienced in implementing biocarbon development projects can be addressed by increasing the number of training workshops offered on conducting carbon inventories, bridging the gaps in research and development, increasing access to capital and improving infrastructure development. It is fundamental to ensure progress in these statures to encourage further sustainable farming techniques for the benefit of the environment, society and the economy.
A New Paradigm for Evidence-Based Land and Soil Management Recommendations
There has been a failure in developing evidence-based land, soil and crop management recommendations due to two fundamental limitations. The first limitation is that target areas have not been defined and properly sampled when setting up experiments or observations, which has prevented sound inference of results to the area of interest. The second limitation is that uncertainty in the evidence used to make the recommendations has been ignored, thereby pushing the decision risk on to the farmer or land user, and robbing the researchers of the knowledge required on how to reduce uncertainty and improve recommendations. Currently, the data used to develop recommendations are rarely traceable. Recommendations are rarely validated in a systematic way. A surveillance framework for making evidence-based land, soil and agronomic recommendations is presented and illustrated with an example of developing fertiliser recommendations in the Africa Soil Information Service (AfSIS). The cropland areas of a country are first identified as the region of interest. A statistically valid sampling scheme is used for siting soil sampling campaigns and agronomic trials. Low cost and rapid spectral measurement methods are used to handle the large numbers of sample analyses required. The approach permits unbiased estimates of soil constraints and crop responses to be made and mapped with the aid of remote sensing covariates. Uncertainty in recommendations is presented to end users and value-of-information analysis used to pinpoint where further information is required to improve recommendations and reduce end-user decision uncertainty.
Effects of cultivation practices on biomass partitioning of Boerhavia diffusa L.
Although traditional knowledge on the medicinal properties of Boerhavia diffusa L. of the family Nyctaginaceae is known, production potential, assimilate partitioning to economic yields and agronomic requirements for commercial cultivation are poorly understood. Consequently, the objective of this study was to identify agronomic practices that could partition more assimilate to economic components to obtain optimum yield from cultivation. A factorial experiment was carried out at the University of Peradeniya Experimental Station, Dodangolla, Sri Lanka from July 2006 to August 2008. Treatments include two types of planting materials, five types of fertilizers and five harvesting methods. The results revealed that the seedlings performed better than cuttings in all studied parameters. Among types of fertilizers, the recommendation for Ipomoea batatas (L.) Lam. (Sweet potato) was the best for production of below ground dry matter in seedling plants. The optimum rate of below ground dry matter was attained at 8 months after planting (MAP) in seedlings. Organic or inorganic fertilizer recommendation for Trianthema portulacastrum L. (Sarana) was the most suitable for harvesting of above ground dry matter of seedling plants. The study also showed that B. diffusa could be managed by repeated harvesting of above ground dry matter as a leafy vegetable at two month intervals up to six months followed by harvesting the entire plant at eight MAP for medicinal as well as a leafy vegetable. Implications of research findings are discussed.