Agronomic and financial benefits of direct Minjingu phosphate rock use in acidic humic nitisols of Upper Eastern Kenya

Ndeleko-Barasa, Emily Mwake; Mucheru-Muna, M.; Ngetich, Felix K.

doi:10.1016/j.heliyon.2021.e08332

Cited by 4 publications

(3 citation statements)

References 45 publications

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“…Omenda et al (2021) reported that treatments with sole PR gave low yields and did not differ significantly with the control with no P input. Ndeleko- Barasa et al (2021) similarly reported that TSP had significantly higher grain yields (6.86 Mg ha -1 ) than MPR (3.0 Mg ha -1 ) in Upper Eastern Kenya.…”

Section: Responses Of Crops To Phosphate Rocks In East Africamentioning

confidence: 91%

The Use of Phosphate Rocks in East Africa: A Review

Opala

2022

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The use of locally available phosphate rock (PR) has often been proposed as a cheaper alternative to the more expensive superphosphate fertilizers to alleviate severe phosphorus deficiencies that threaten food security in East Africa. Extensive research has therefore been conducted in the region over the years focusing on the PR sources, their reactivity, agronomic effectiveness and the economics of their use and adoption. The agronomic effectiveness varied with the type of PR, the site, seasons and crop. Minjingu PR was the most promising among the PRs for direct application but others such as Panda, Sukulu and Busumbu PR were largely ineffective. The financial returns due to use of PR ranged from negative to positive but in many cases were economically not attractive. The adoption of PR use among farmers was dismal with the unavailability of the PR in the market and high cost, paradoxically being cited as the main constraints to its adoption. To enhance the chances of adoption, it is recommended that participatory approaches to research that involve the targeted beneficiaries especially the PR marketers and smallholder farmers be used.

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Section: Responses Of Crops To Phosphate Rocks In East Africamentioning

confidence: 91%

The Use of Phosphate Rocks in East Africa: A Review

Opala

2022

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“…These fertilizer products are used on acidic soils and are also exported to neighboring countries. Kenya uses considerable amounts of fertilizer products derived from Minjingu phosphate rock (Kifuko et al 2007;Ndungu-Magiroi et al 2015;Ndeleko-Barasa et al 2021) and thus has the second highest average uranium concentration among the investigated countries in this study as indicated in Table 4.…”

Section: Uranium Concentration In Major Phosphate Fertilizers Used In...mentioning

confidence: 92%

Uranium in phosphate rocks and mineral fertilizers applied to agricultural soils in East Africa

Mwalongo

Haneklaus

Lisuma

et al. 2022

Environ Sci Pollut Res

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Phosphate rock, pre-concentrated phosphate ore, is the primary raw material for the production of mineral phosphate fertilizer. Phosphate rock is among the fifth most mined materials on earth, and it is also mined and processed to fertilizers in East Africa. Phosphate ore can contain relevant heavy metal impurities such as toxic cadmium and radiotoxic uranium. Prolonged use of phosphate rock powder as a fertilizer and application of mineral fertilizers derived from phosphate rock on agricultural soils can lead to an accumulation of heavy metals that can then pose an environmental risk. This work assesses the uranium concentrations in four major phosphate rocks originating from East Africa and four mineral phosphate fertilizers commonly used in the region. The concentration measurements were performed using energy-dispersive X-ray fluorescence spectrometry. The results showed that the uranium concentration in phosphate rock ranged from as low as 10.7 mg kg−1 (Mrima Hill deposit, Kenya) to as high as 631.6 mg kg−1 (Matongo deposit, Burundi), while the concentrations in phosphate fertilizers ranged from 107.9 for an imported fertilizer to 281.0 mg kg−1 for a local fertilizer produced from Minjingu phosphate rock in Tanzania. In this context, it is noteworthy that the naturally occurring concentration of uranium in the earth crust is between 1.4 and 2.7 mg kg−1 and uranium mines in Namibia commercially process ores with uranium concentrations as low as 100–400 mg kg−1. This study thus confirms that East African phosphate rock, and as a result the phosphate fertilizer produced from it can contain relatively high uranium concentrations. Options to recover this uranium are discussed, and it is recommended that public–private partnerships are established that could develop economically competitive technologies to recover uranium during phosphate rock processing at the deposits with the highest uranium concentrations.

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“…This study revealed that from all reviewed articles, the concentration of U from Minjingu P fertilizers from Tanzania ranged from 200 to 600 mg kg −1 , which is similar to what is found in open-pit commercial uranium mines in Namibia. Minjingu P fertilizers have been reported to be used in neighboring East African countries such as Kenya, Uganda, the Democratic Republic of Congo (DRC), Burundi, Rwanda, and Zambia, so this issue can hardly be described as a local phenomenon, but does indeed affect millions [32][33][34][35].…”

Section: Introduction 1background Informationmentioning

confidence: 99%

Uranium Dissemination with Phosphate Fertilizers Globally: A Systematic Review with Focus on East Africa

Mwalongo,

Haneklaus,

Lisuma

et al. 2024

Sustainability

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Growing concern has been expressed about uranium (U) accumulation in agricultural soils caused by the long-term application of mineral fertilizers. More than 80% of naturally occurring U transfers from phosphate rock (PR), the raw material used in mineral fertilizer production, to phosphorus (P) fertilizers. These fertilizers are then distributed on agricultural soils, where the U could accumulate over time and become a risk to the environment. The objective of this work was to review the reported content of U in P fertilizers, its potential dispersion in soils, and its uptake by plants in different countries in the world as reported in the literature. The articles for this systematic review were selected from the Scopus database published between 2003 and 2022. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) protocol were used. A total of 54 articles were assessed based on the standard inclusion and exclusion criteria. U concentrations in P fertilizers, agricultural soil dissemination, and plant uptake for available data were obtained and assessed. In order to compare a set of related data from the collected articles, box and whisker plots showing the distribution of U in P fertilizers are presented by region. The results from the reviewed articles show that the U concentrations in P fertilizer were in the range of 0.1–653 mg kg−1. Interestingly, Minjingu P fertilizers from Tanzania, which are used in six East African countries, showed the highest U concentrations (159 to 653 mg kg−1, average 390 mg kg−1). The reported U concentrations for these fertilizers are, in fact, comparable to those of conventional low-grade uranium deposits mined in Namibia and elsewhere. Additionally, approximately 96% of the reviewed articles indicate that fertilized soil has higher U concentrations than non-fertilized soils, hinting at a measurable effect of mineral fertilizer use. The review recommends U extraction during mineral fertilizer production so that potential environmental risks can be reduced and U resources that would otherwise be lost can be recovered and used to substitute conventional U mining elsewhere.

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Agronomic and financial benefits of direct Minjingu phosphate rock use in acidic humic nitisols of Upper Eastern Kenya

Cited by 4 publications

References 45 publications

The Use of Phosphate Rocks in East Africa: A Review

The Use of Phosphate Rocks in East Africa: A Review

Uranium in phosphate rocks and mineral fertilizers applied to agricultural soils in East Africa

Uranium Dissemination with Phosphate Fertilizers Globally: A Systematic Review with Focus on East Africa

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