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Achieving sustainable agricultural development is a vital concern as soil degradation poses a growing threat to the livelihoods of smallholder farmers in the developing world. Previous literature has highlighted the potential for rural population growth to exacerbate this concern by leading to smaller farm sizes and crop production on marginal land. This paper uses a theoretical model to demonstrate a countervailing effect consistent with the work of Esther Boserup: Smaller farm sizes can encourage greater intensification and investment in the soil. Using panel data from the Tanzania National Panel Survey, I test the model and find some evidence consistent with this effect. Smaller farms are associated with greater organic, but not inorganic, fertilizer application, and higher levels of some soil quality proxies. These results suggest that if key resource and information constraints are overcome, population growth need not be an obstacle, and can be a boon, to sustainable agricultural development. [ABSTRACT FROM AUTHOR]

Input subsidy programs (ISP) often have two conflicting targeting goals: selecting individuals with the highest marginal return to inputs on efficiency grounds, or the poorest individuals on equity grounds, allowing for a secondary market to restore efficiency gains. To study this targeting dilemma, we implement a field experiment where beneficiaries of an ISP were selected via a lottery or a local committee. In lottery villages, we find evidence of displacement of private fertilizer and of a secondary market as beneficiaries are more likely to sell inputs to non‐beneficiaries. In contrast, in non‐lottery villages we find no evidence of displacement nor of elite capture. The impacts of the ISP on agricultural productivity and welfare are limited, suggesting that resources should be directed at complementary investments, such as improving soil quality and irrigation. [ABSTRACT FROM AUTHOR]

Aims: Perennial forage grass production has the potential to improve smallholder livelihoods in the tropics. However, nutrient management is often challenging, especially on infertile sandy soils. This study tested whether typical nutrient management limits the productivity and sustainability of perennial forage grass systems on sandy soils. Methods: Nutrient balances were estimated for four fields of either Megathyrsus maximus cv. Tanzania or Urochloa hybrid Mulato II. Nutrient limitations were then evaluated in a nutrient omission experiment. Results: All soils were sandy (< 10% clay), neutral to acidic (pH (CaCl2) 4.6 to 6.7) and had plant-limiting concentrations of total nitrogen, extractable potassium and extractable sulfur. Nitrogen inputs were typically higher than outputs, with balances ranging from −16 kg ha−1 yr−1 to 293 kg ha−1 yr−1, yet concentrations in forage shoots were low at all sites. Phosphorus balances ranged from −5 kg ha−1 yr−1 to 77 kg ha−1 yr−1 and concentrations in forage shoots were adequate. Potassium inputs were low, resulting in balances from −79 kg ha−1 yr−1 to −138 kg ha−1 yr−1 at locations that did not apply inorganic potassium fertilizer. Potassium concentrations in forage shoots were low and omission of potassium resulted in severely depressed biomass production. Inorganic sulfur fertilizers were not applied to forages and the sulfur balance varied from −1 kg ha−1 yr−1 to −24 kg ha−1 yr−1. Sulfur concentrations in shoots were correspondingly low and production was depressed when sulfur was omitted in the experiment. Conclusion: Balanced nutrition was not achieved, despite substantial fertilizer inputs, resulting in deficiencies of potassium and sulfur, inefficient use of nitrogen and excesses of phosphorus. If current practices continue, potassium and sulfur depletion, phosphorus accumulation and soil acidification can be expected. Recommendations for balanced nutrient management that accounts for high rates of removal in biomass, variable concentrations in organic fertilizers, and leaching potential, are needed to sustain the productivity of perennial forages on tropical sandy soils. [ABSTRACT FROM AUTHOR]

Agricultural practices to improve yields in small‐scale farms in Africa usually focus on improving growing conditions for the crops by applying fertilizers, irrigation, and/or pesticides. This may, however, have limited effect on yield if the availability of effective pollinators is too low. In this study, we established an experiment to test whether soil fertility, soil moisture, and/or pollination was limiting watermelon (Citrullus lanatus) yields in Northern Tanzania. We subjected the experimental field to common farming practices while we treated selected plants with extrafertilizer applications, increased irrigation and/or extra pollination in a three‐way factorial experiment. One week before harvest, we assessed yield from each plant, quantified as the number of mature fruits and their weights. We also assessed fruit shape since this may affect the market price. For the first fruit ripening on each plant, we also assessed sugar content (brix) and flesh color as measures of fruit quality for human consumption. Extra pollination significantly increased the probability of a plant producing a second fruit of a size the farmer could sell at the market, and also the fruit sugar content, whereas additional fertilizer applications or increased irrigation did not improve yields. In addition, we did not find significant effects of increased fertilizer or watering on fruit sugar, weight, or color. We concluded that, insufficient pollination is limiting watermelon yields in our experiment and we suggest that this may be a common situation in sub‐Saharan Africa. It is therefore critically important that small‐scale farmers understand the role of pollinators and understand their importance for agricultural production. Agricultural policies to improve yields in developing countries should therefore also include measures to improve pollination services by giving education and advisory services to farmers on how to develop pollinator‐friendly habitats in agricultural landscapes. [ABSTRACT FROM AUTHOR]

Intercropping of maize with grain-legume crops predominates on smallholder farms in East Africa. However, the growth and development of crops and their interaction with fertilizer in intercropping systems are not well understood. We sought to answer the questions: (i) what are the effects of fertilizer on the growth and development of maize-pigeonpea and maize-lablab intercropping systems under variable agroecological conditions? (ii) what are the residual effects of two seasons of sole and intercrops of maize, pigeonpea and lablab on a succeeding maize crop? We studied pure stands of maize, long-duration pigeonpea, medium-duration pigeonpea and lablab, and additive intercropping combinations on eight farms in Babati, Tanzania. The intercropping combinations studied were: maize with long-duration pigeonpea, maize with medium-duration pigeonpea and maize with lablab. Three fertilizer levels were applied: no fertilizer; 40 kg P ha−1; and 90 kg N ha−1 + 40 kg P ha−1. The P was applied at planting in the form of triple superphosphate to both maize and legumes, thus in intercrops the 40 kg P ha−1 was shared between maize and legume. The N was spot-applied in the form of urea in three equal splits, only on maize. The trials were implemented for two consecutive cropping seasons (2017/2018 and 2018/2019), without changing treatments and plot locations. To evaluate the residual effect of grain legumes, we planted a sole crop of maize in the third season (2019/2020) in all plots, with no addition of fertilizer. Maize and pigeonpea were sown simultaneously, while lablab was relay-planted one month after maize. Maize dry matter (DM) and grain yield were not significantly affected by the presence of legumes, but were about twice as large in 2017/2018 as in 2018/2019 season, likely due to the considerably higher rainfall in the 2017/2018 season. Legume productivity was more consistent across the two seasons. Legume crops in the intercrops produced significantly less DM and grain yield than in their respective pure stands, but maize yield did not differ significantly between sole and intercrops. The productivity of maize was significantly increased by N fertilization, but the legumes responded positively only to P fertilizer in the 2017/2018 season. Land-equivalent and area-time-equivalent ratios of intercropping systems were consistently greater than one. The DM and grain yield of maize following two seasons of legumes was consistently larger than in plots where maize was grown continuously. The P-fertilizer applied in the preceding seasons had significant residual effects on the yield of the succeeding maize crop. The temporal niche complementarity of pigeonpea and lablab with maize minimized competition in the intercrops, although intercrops are clearly more demanding in labor at planting and harvest. Overall, our results showed the superior performance of maize-legume intercropping over sole maize, both in terms of additional grain yield within a season and the residual effects in the succeeding season. We did not observe biotic constraints in the succeeding maize crop. Maize-legume intercropping with fertilizer application was effective in enhancing the productivity of smallholder cropping systems. [ABSTRACT FROM AUTHOR]

Summary: Through decentralized targeting of input vouchers new agricultural input subsidy programs aim to more effectively reach their objectives and target population. But, lingering fears of elite capture remain. These are borne out in the 2009 input voucher program in Kilimanjaro, Tanzania. Sixty percent of the voucher beneficiaries were households with village officials. This significantly reduced the targeting performance of the program, especially in unequal and remote communities. When targeting the poor, greater coverage and concentration in higher trust settings mitigated these concerns. Scrutiny remains important when relying on decentralized targeting, as is a clearer sense of purpose of input vouchers. [ABSTRACT FROM AUTHOR]

Abstract: Productivity of maize–pigeonpea cropping systems is dependent on facilitative and competitive interactive effects on resource availability. Controlling these interactions may benefit farmers through increased productivity associated with optimized crop yields. Previous research on maize–pigeonpea culture in Sub-Saharan Africa has focused on yield and soil fertility, but provided inadequate information on the mechanisms of possible interspecific competition. We employed a factorial field experiment to examine yield and nutritional responses of maize and pigeonpea to cropping systems (sole maize, intercropping, and improved fallow), N and P fertilizer additions, and cattle manure additions in Dodoma, Tanzania. The study objectives were to assess competition between crops and to determine how manure or fertilizer inputs may mitigate such interactions to improve yields. Intercropping enhanced maize yield over sole maize only when fertilized, reflecting probable nutrient competition. Improved fallows alone or with fertilizers (1.2–1.6Mgha−1) increased maize yields over sole maize (0.6Mgha−1). These increases were attributed to pigeonpea facilitation through soil nutrient replenishment, reduced competition associated with sequential cropping arrangements, and added nutrients from fertilization. Combined fertilizer and manure applications also improved maize and pigeonpea yields. Plant nutrient diagnosis indicated primary and secondary P and Ca deficiencies, respectively associated with P-fixation and leaching of cations due to high soil acidity and exchangeable Al. Maize competed strongly in mixture suppressing biomass and grain yields of the unfertilized pigeonpea by 60% and 33%, respectively due to limited soil nutrients and/or moisture. These yield reductions suggest that the intercropped pigeonpea did not recover from competition after maize harvesting that reduced competition. Optimizing yields of both maize and pigeonpea would require the addition of prescribed fertilizer when intercropped, but applications can be reduced by half under the improved fallow system due to alleviating interspecific competition. [Copyright &y& Elsevier]

To alleviate P deficiency in Tanzania and elsewhere, direct application of local phosphate rock (PR) can be an attractive alternative to imported fertilizers, for example, triple superphosphate (TSP), provided crop responses to PR and TSP are comparable. The deposit at Minjingu (MPR) in Tanzania consists of hard MPR and soft MPR. These PRs were compared with each other and with TSP on four acidic soils low in plant-available Ca and P in a greenhouse experiment by determining relative maize yield, P uptake, and relative agronomic effectiveness (RAE). TSP produced significantly stronger responses than MPRs but only with the first crop (RAE=40–70%), whereas MPRs were more effective with a second crop (RAE=106–150%). Similar responses to hard and soft MPR (and TSP with a second crop) indicate that the currently unutilized hard MPR, which constitutes 60% (4.8×106 Mg with 10.6% P) of the Minjingu phosphate deposit, can be utilized. [ABSTRACT FROM AUTHOR]

Despite improvements in production incentives, agricultural output in Africa remained sluggish through the 1990s. Low use of purchased inputs may be part of the cause of persistently low productivity in African agriculture. This article analyzes the roles of relative prices and transactions costs in explaining low use of chemical inputs among Tanzanian coffee growers. A sample selection model indicates that output prices exert great influence on input purchases and that both fixed and variable transactions costs affect input use decisions. Travel costs in input and output markets have distinct effects on input usage, implying distinct avenues for interventions to promote more intensive use of agricultural inputs. [ABSTRACT FROM AUTHOR]

Background: The wide distribution of malaria mosquito breeding sites within tropical environments limits the mosquito larval source management efforts to control malaria. Rice farming contributes substantially in supporting malaria mosquito productivity in tropical countries. To overcome this challenge, this study was carried out to determine the effect of applying a mixture of biolarvicide and fertilizer on mosquito larvae density in rice farms under semi-field conditions in Tanzania. Methods: A semi-field experiment was designed to determine the timing of application of a biolarvicide, Bacillus thuringiensis israelensis (Bti) and fertilizer (di-ammonium phosphate-DAP or urea) and assess their effect on mosquito larvae density and rice grain outputs. The experiment had five blocks (4 treatment arms and one control arm) and each had four replicates. Treatment arms had different intervals of days between treatments for mixtures of fertilizer and biolarvicides. The dosages used were 10 g of Bti/16 M2 and 160 g of DAP/Urea/16 m2. Results: In overall, the intervention blocks (with biolarvicide) had lowest mean mosquito larvae abundance compared to control block (F = 22.42, P < 0.001). Similarly, the control arm maintained highest density of Anopheles gambiae sensu lato larvae compared to interventions blocks (F = 21.6, P < 0.001). The best determined timing for application of Bti was in 7 and in 10 days (F = 3.753, P < 0.001). There was neither significant different in mean rice grain harvest per ten panicle (F = 1.453, P = 0.27) nor mean difference in rice grain harvest (F = 1.479, P = 0.26) per intervention arms. Conclusion: The findings of this study have shown that application of a mixture of Bti and fertilizer have impact on both mosquito larvae density and maintaining yield rice harvest. Thus, application of a combination of biolarvicide and fertilizer can be an alternative approach in malaria mosquito intervention among rice farming communities of rural Tanzania. [ABSTRACT FROM AUTHOR]

Background: The use of larval source management as a supplementary intervention for malaria control has not been widely used in rural Africa due to perceived high costs and complex logistics. To reduce the cost of larviciding in rice farming communities, concurrent application of biolarvicides and fertilizer in rice fields was introduced to control malaria vectors larvae and improve rice grain yields. The present study determined rice farmers' perceptions and acceptability in the use of a combination of biolarvicide and fertilizers in farming practices. Methods: This was a qualitative study conducted among rice farmers at Kilangali village, south-central Tanzania. Semi-structured interviews and three focus group discussions (FGDs) were conducted with men and women who participated in the biolarvicide and fertilizer application project. The interviews and discussion focused on knowledge, attitudes and perceptions of participants on the use of the innovation in their farming practices and their willingness to pay for the innovation. Results: A total of 40 (mean age = 38.8 ± 10.12 years) rice farmers were involved in the study. Overall, all farmers agreed that it was possible to apply the two products concurrently with minimal challenges. The trust on the safety of biolarvicides on both human and paddy health was high. Respondents reported no challenge in preparation and applying the product in their rice fields. Over half (56.6%) of the participants reported an average decrease in mosquito density in their households and a quarter (26.6%) of them reported a decrease in mosquito population in their farms. Similarly, 93.3% of the participants reported that the intervention had reduced malaria risk in their households. In general, all participants expressed willingness to contribute to a biolarvicide and fertilizer programme and to use the approach in their farming practices. Conclusion: Community-based concurrent application of biolarvicides and fertilizer in rice fields was feasible and led to a perceived reduction in mosquito density. Willingness to pay for the larviciding/fertilizer approach was expressed by participants and they accepted to use the approach in their future farming practices. However, the impact of this approach on malaria transmission and rice grain harvest need to be evaluated in a large-scale programme. [ABSTRACT FROM AUTHOR]