Minjingu Phosphate Rock Research Articles

Effectiveness of Phosphorus Solubilizing Bacteria on Enhancing Phosphorus Availability from Minjingu Phosphate Rock to Maize in Slightly Acid to Neutral Soils

The aim of this one-year field study was to evaluate the impact of phosphorus solubilizing bacteria (PSB) on increasing the availability of phosphorus locked up in insoluble Minjingu phosphate rock for the maize crop (Zea mays L.) in high soil pH. The study was carried out during one wet season in Nghumbi and Mlali villages in Kongwa District in the Dodoma Region, Tanzania. Based on the pH of their soil and the limiting nutrients, two farms from Mlali village and five from Nghumbi village were chosen at random for field trials. To determine the fertility status, composite soil samples were collected from the chosen farms and examined in a lab. Target treatments included the application of PSB inoculum in combination with various rates of Minjingu phosphate rock (MPR) (0, 20, 30, 40, and 60 KgP ha-1) as a basal fertilizer, placed beneath maize seed and covered with a thin layer of soil. Using a fully randomised block design, the treatments were set up three times. Inadequate levels of N, P, K, and Zn were found in the research area's soil samples. Results indicated the main effect of fields’ characteristics from field No.2 had the highest yield to other fields with significantly (P< 0.001) highest grain yield being 4.4 t ha-1, biological yield of 5.6 t ha-1, and Straw P uptake of 19.63 kg ha-1. Using P or an inoculant (Mx) produced a negligible yield of grain and straw, according to the major effect of treatments. For the studied variables, none of the treatments showed any significant (P =0.427) interaction effects. An intriguing revelation that the study's maize response to native P is provided by interaction effects area is a factor of soil and amount of P released to the soil. We recommend more research on PSB for more than one season in high soil pH before ascertaining the technology to farmers.

The Use of Phosphate Rocks in East Africa: A Review

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.

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

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.

Role of Minjingu Rock Phosphate and Nitrogen Fertilizer in Improving Phosphorus and Nitrogen Use Efficiency in Maize: A Kenyan Case Study

Role of Minjingu Rock Phosphate and Nitrogen Fertilizer in Improving Phosphorus and Nitrogen Use Efficiency in Maize: A Kenyan Case Study

Minjingu phosphate rock solubilization and potential for use of Klebsiella variicola-MdE4 and Klebsiella variicola-MdG1 as biofertilizer for maize production

Limited solubility of the Tanzania’s Minjingu phosphate rock (MPR) in non-acidic soil conditions has held back its potential for widespread use in agricultural production. This study was designed to isolate, characterize and test phosphate-solubilizing bacteria for their potential to increase solubility of MPR and enhance maize plant growth under field conditions. Ten out of 19 isolates showing greatest phosphate solubilization indices on a Pikovskaya agar medium were further characterized for other plant-growth promoting traits including production of IAA, siderophores and ammonia. Two of them, namely isolates-MdE4 and MdG1 substantially outperformed other isolates in phosphate solubilization and production of IAA, ammonia and siderophores. The two isolates molecularly identified as Klebsiella variicola-MdE4 and K. variicola-MdG1 produced up 701, 699 and 750, 680 μg/ml of soluble phosphate from tricalcium phosphate and hard Minjungu rock phosphate, respectively. Additionally, Biorock P- a biofertilizer formulation containing MdE4 and MdG1 co-cultured in a molasses-based modified broth medium retained most of the phosphate solubilizing potential and other plant-growth promoting traits of MdE4 and MdG1. Co-application of MdE1 and MdG1-containing “bio-rock P” and inorganic phosphate at 20 kg P/ha resulted in higher maize grain yield than that of positive control (40 kg P/ha) under field conditions. The two isolates- Klebsiella variicola-MdE4 and K. variicola-MdG1 have the potential for use in a biofertilizer formulation for commercial field applications.

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

A major constraint to crop production in Sub-Saharan Africa is nutrient deficiency, especially phosphorus (P) deficiency. Phosphorus plays a crucial role in photosynthesis but is usually deficient in acidic soils since it is converted to less available forms, affecting crop yields. There is a need to improve phosphorus availability to crops for maximum production. This study assessed Minjingu phosphate rock fertilizer's impact on maize yields, soil chemical composition, and cost-effectiveness in acidic humic nitisols of Tharaka Nithi County, Upper Eastern Kenya. A field experiment in a randomized complete block design (RCBD) was set during long rains (SR2017) and Short rains (LR2018) seasons. The treatments were Minjingu phosphate rock, manure, Tithonia diversifolia, Minjingu phosphate rock + manure, Tithonia diversifolia + Minjingu phosphate rock, Calcium Ammonium Nitrate (CAN) + Triple Superphosphate (TSP), and a control. Soil samples were collected at a depth of 0–20 cm before and at the end of the experiment for pH, P-sorption, and other soil nutrient determinations. Other auxiliary data collected included labor and input costs besides output prices. The CAN+TSP treatment had significantly higher grain yields (6.86 Mg ha-1), while Minjingu phosphate rock on its own had the second-lowest than the control treatment (3.0 Mg ha-1). Also, a similar trend in the stover yields was observed. Minjingu phosphate rock combined with either manure or Tithonia diversifolia led to a significant increase (over 100%) in the phosphorous levels. Sole application of Minjingu phosphate rock increased soil iron levels while magnesium, copper, and zinc levels decreased significantly. Other than the control, all treatments significantly lowered the P-sorption levels. However, CAN+TSP had the highest P-sorption (913 mg kg−1)while Tithonia diversifolia had the lowest (744 mg kg−1). During the LR2018 season, all treatments reached a break-even point, and the net benefit was significantly higher at P < 0.05. Conclusively, the use of phosphate rock, either solely or in combination with organic elements, improved yields, soil chemical composition, P-sorption and was very cost-effective.

Maize Productivity, Economic Returns and Phosphorus Use Efficiency as Influenced by Lime,Minjingu Rock Phosphate and NPK Inorganic Fertilizer

Maize Productivity, Economic Returns and Phosphorus Use Efficiency as Influenced by Lime,Minjingu Rock Phosphate and NPK Inorganic Fertilizer

English

Phosphorus deficiency majorly constrains maize (Zea mays L.) production in acidic soils of western Kenya. This requires high doses of expensive inorganic P fertilizers to correct. Recommended rock phosphates and manures are lowly adopted because of low solubility and P content respectively. A Randomized Complete Block Design experiment was conducted for two seasons to assess effect of a cheaper alternative P source, Phosphorus fortified Tithonia compost (PCM), on growth and yield of maize and lablab-intercropped maize on two sites with different soil fertility. The experiment was set up on seven farms per site in Kapkerer (low fertility) and Koibem (higher fertility). Three P source treatments of Minjingu rock phosphate (MRP), Phosphorus fortified Tithonia compost and Triple Super Phosphate (TSP) were applied at an equivalent rate of 26 kg P/ha for maize and maize-lablab intercrop. Data on plant height, Leaf Area Index (LAI), aboveground biomass, leaf P concentration and grain yield were collected. PCM treatment significantly (p&le;0.05) increased maize height, LAI, aboveground biomass and grain yield compared to TSP in Kapkerer. No significant differences were noted in leaf P concentrations. PCM is a good alternative to expensive inorganic P fertilizers in acidic soils of western Kenya. Key words: Tithonia P-fortified compost, Rock phosphate, intercropping, lablab.

English

A glasshouse experiment was conducted to evaluate the effect of composting coffee pulp with phosphate rock on phosphorus (P) availability for plant uptake. Coffee pulps composted with or without phosphate rock and Minjingu phosphate rock applied alone were evaluated as source of P for tomato growing on a Chromic Acrisol. All P sources were applied at varying rates of 0, 20, 40, 60, 80 and 100 mg P kg-1 and all other limiting nutrients were adjusted to recommend levels using industrial fertilizers and/or reagent grade laboratory salts. Phosphorus uptake of tomato plants receiving coffee pulp composted alone, Minjingu phosphate rock alone and coffee pulp composted with Minjingu phosphate rock increased 11, 13 and 18 times above the control. Observed P concentrations in tomato plants receiving external P sources were 23, 36%and 110% of the concentrations in control plants. Composting coffee pulp with Minjingu phosphate rock was concluded as a potential technique for improving phosphorus availability and uptake by tomato. Key words: phosphate rock, coffee pulp, phosphate rock enriched compost, tomato, phosphorus uptake.

Effects of Phosphorus Sources and Application Rates on Nitrogen and Phosphorus Concentrations and Phosphorus Use Efficiency in Rice Plant

A study was conducted to determine the effects of nitrogen (N) and phosphorus (P) concentrations and P use efficiency from Minjingu phosphate rock (MPR), Minjingu mazao and Triple Super Phosphate (TSP) fertilizers under irrigated rice (Oryza sativa L.) production in Lekitatu village, Meru district, Arusha region, Tanzania. The initial soil pH in the two experimental sites was slightly alkaline while total N and available P was low and medium respectively. Randomized Complete Block Design (RCBD) with three replications was adopted and phosphorus was applied at the rates of 0, 20, 40 and 60 kg P ha-1 as MPR, Minjingu mazao and TSP. Nitrogen was applied uniformly at a rate of 60 kg N ha-1 as urea taking into account the 10% N contained in the Minjingu mazao fertilizer. Phosphorus application increased N and P contents in the rice plants and phosphorus use efficiency (PUE) with the increase of P levels from 0 to 60 kg P ha-1 for all P sources. The site 1 had more PUE than site 2 due to higher moisture content. These effects were due to increased availability and nutrients uptake by plants, particularly P. Based on the results, it is recommended that; Minjingu mazao at the rates of 40 to 60 kg P ha-1, MPR and TSP at a rate of 60 kg P ha-1, respectively have to be adopted for sustainable soil P use in rice production areas of Lekitatu village.

Effect of Applying Organic Amendments and Chickpea Integration on Soil Chemical Properties in Different Cropping Systems in Central Kenya

A study was carried out to determine the effect of applying farm yard manure (FYM) and Minjingu rock phosphate (MRP) on soil available nitrogen, phosphorus and organic carbon. The study involved field experiments under varying precipitation pattern, soil fertility levels and cropping systems over four growth seasons. The experimental design was a randomized complete block (RCBD) with four replications in a split plot arrangement where the main plots were the three cropping systems; monocropping, intercropping and crop rotation and the split plots were FYM and MRP and sampling done at crop physiological maturity. Soil pH, N, P K and C increased in the different treatments in the following order control &amp;lt; MRP &amp;lt; FYM in the three cropping systems across the four growing seasons at both sites. In maize under rotation with chickpea control had; 0.281% N, 2.82% C and 10.68 ppm P. FYM; 0.554% N, 4.41% C and18.24 ppm P. MRP; 0.45% N, 3.6% C and 41.08 ppm P. Maize chickpea intercrop control; 0.389% N, 3.192% C and 13.4 ppm P. FYM; 0.531% N, 4.98% C and 41.02 ppm P. MRP; 0.49% N, 4.08% C and 50.9 ppm P. Soil under maize monocrop exhibited; control; 0.2% N, 2.59% C and11.26 ppm P. FYM; 0.416% N, 3.83% C and 18.01 ppm P. MRP; 0.28% N, 3.13% C and 26.1ppm P. Almost a similar trend was observed in maize and tomato plots at both sites in all the growing seasons. Thus it can be deduced that, FYM and MRP application and legume integration in cropping systems improves soil fertility.

English

Low use efficiencies of inorganic fertilizers coupled with their rising costs has diverted attention of farmers towards organic sources. A study was conducted in Yatta sub-county between October 2012 to February 2013 short rains and April-August 2013 long rainy seasons to evaluate how tillage, cropping and organic inputs influenced soil nutrient status. A randomized complete block design with a split-split plot arrangement replicated three times was used. The main plots were tillage practices (TP): Split-plots comprised the cropping systems (CS) while split-split plots were organic inputs, plus the control. The test crops were sorghum and sweet potatoes (Impomea batata) with Dolichos (Dolichos lablab) and chickpea (Cicer arietinum L.) added either as intercrops or in rotation. Soil was randomly sampled at 0 to 30 cm depth at the onset of the experiment and at maturity of test crop for NPK and % organic carbon (OC) analysis. Significant (P≤0.05) high level of K (1.91 Cmol/+kg), available P (51.45 ppm), total N (0.19%) and OC (2.19%), in combined TR, intercrop sorghum/chickpea with application of Minjingu rock phosphate (MRP)+ farmyard manure (FYM) during SRS of 2012 compared to the other treatment combinations was observed. Comparing different organic inputs, tillage practices and cropping systems combined tied ridges (TR), intercrop of sorghum/chickpea and MRP+FYM and FYM increased the soil nutrients status. Therefore, soil organic inputs such as MPR and FYM are viable alternatives to inorganic fertilizers for improving the soil nutrient status. The study therefore recommends incorporation of the organic inputs in combination with TR, as well as intercropping with legumes in their cropping systems to improve soil health and resilience. Key words: Cropping systems, tillage practices, organic inputs, semi-arid, soil nutrients.

Biological P cycling is influenced by the form of P fertilizer in an Oxisol

Phosphate rock (PR) is an alternative fertilizer to increase the P content of P-deficient weathered soils. We evaluated the effects of fertilizer form on indicators of biological cycling of P using an on-farm trial on a Rhodic Kandiudox in western Kenya. Treatment plots were sampled after 13 cropping seasons of P applications as Minjingu phosphate rock (PR) or as triple super phosphate (TSP) (50 kg P ha−1 season−1), as well as a P-unfertilized control (0 kg P ha−1 season−1). Soils (0–15 and 15–30 cm) were analyzed for microbial biomass P (Pmic), activities of acid phosphomonoesterase, alkaline phosphomonoesterase, and phosphodiesterase, and sequentially extractable P fractions. P additions as Minjingu PR yielded 299% greater Pmic than TSP at 0–15-cm depth despite similar labile P concentrations in the two P fertilization treatments and stimulated activities of acid phosphomonoesterase (+39%). When added in the soluble form of TSP, a greater percentage of total soil P was present in mineral-bound forms (+33% Fe- and Al-associated P). Higher soil pH under Minjingu PR (pH 5.35) versus TSP (pH 5.02) and the P-unfertilized treatment (pH 4.69) at 0–15-cm depth reflected a liming effect of Minjingu PR. The form of P fertilizer can influence biological P cycling in weathered soils, potentially improving P availability under Minjingu PR relative to TSP via enhanced microbial biomass P and enzymatic drivers of P cycling.

Effects of compost type and storage conditions on climbing bean on Technosols of Tantalum mining sites in Western Rwanda

AbstractLittle is known about the effects of compost application to reclaim artisanal mining sites for agriculture in Central Africa. A field experiment was therefore conducted to examine the effects of locally available organic household waste composted under traditional (pit under leaf shade) versus improved management (pit under double plastic sheeting) and mixed with either Tithonia diversifolia biomass or Minjingu Phosphate Rock (13–15% P) on climbing bean sown on degraded Technosols (former Tantalum mining sites) and un‐mined control soils (Cambisols). Both soil types were derived from pegmatite. After 6 months of composting, nutrient concentrations in traditional compost were 0.27–0.32% N, 0.06–0.08% P, and 0.20–0.22% K. Comparative values in amended compost were 1.02–1.65% N, 0.10–0.31% P, and 0.41–1.13% K. In farmyard+solid waste, composted under traditional system, dry matter was 65.4%, pH 6.7, and C : N ratio 13.0, as opposed to 81.5% DM, a pH of 8.6, and a C : N ratio of 8.6 in farmyard+solid waste+Minjingu phosphate under improved compost, and 68.3% dry matter, a pH of 8.4, and a C : N ratio of 7.4 for Tithonia+farmyard+solid waste under improved conditions. Compared to bean (Phaseolus vulgaris L.) grain yields of 0.28 (mined soil) and 0.11 (unmined soil) without amendments, the application (on a dry matter basis) of 5 t compost ha−1 led to yields of 3.54 t DM ha−1 for improved compost Tithonia+farmyard+solid waste on mined soil versus 2.26 t DM ha−1 (P &lt; 5%) for the same treatment at the un‐mined sites. The yield obtained for farmyard+solid waste+Minjingu phosphate composted under improved conditions averaged 3.06 t DM ha−1 at mined sites compared with 2.85 t DM ha−1 at un‐mined sites (P &gt; 5%). All amendments were more effective in enhancing bean yields on Technosols with significant positive effects with improved compost than on Cambisols.

Long-term effects of TSP and Minjingu phosphate rock applications on yield response of maize and soybean in a humid tropical maize–legume cropping system

Crop production in sub-Sahara Africa is constrained by low soil phosphorus (P) content. A study was conducted in western Kenya to explore alternative P inputs and ways of optimizing their effectiveness and profitability. A field experiment established in 2007 studied the effects of Minjingu phosphate rock (MPR) and triple superphosphate (TSP) on maize, common beans and soybean yield. MPR and TSP were applied seasonally at a rate of 0, 12.5, 25 and 50 kg P ha−1 either alone or in combination. Application of P, irrespective of amount, resulted in significantly higher grain yield and total biomass for maize, common beans and soybean compared with the 0 P treatment. Applying P at 12.5 kg ha−1 resulted in significantly (ρ ≤ 0.05) lower maize, common beans and soybean grain yields than all the other P rates. On the other hand, application of P at 25 kg ha−1 resulted in similar yields to the higher P application rates. Relative agronomic effectiveness of MPR was similar for both maize and soybeans in most seasons, confirming that MPR has high potential for direct application in these soils. Switching from no application to P applied at 12.5 and also 25 kg P ha−1 attracts a marginal rate of return of at least 200 %. Switching from 25 kg P ha−1 to any of the other options attracted MRR < 200 %. This implies that adoption of either MPR or TSP by farmers in western Kenya is profitable for maize and soybeans production, given that MRRs were above 100 % minimum acceptable rate of return which is a requirement for farmers to change from one technology to another.

The Potential of Minjingu Phosphate Rock for Water Defluoridation

In some parts of Tanzania, fluoride ion concentrations in potable water are higher than recommended by WHO. Consequently, searches for economically and technically viable strategies are required to address this problem. This work aims to determine the potential of phosphate rock mined from Minjingu area in Northern Tanzania as water de-fluoridatant. The results obtained are reported herein. The rock particles were chemically activated and then characterised by XRF, XRD and nitrogen physisorption. Results showed that the main component of chemically activated rock particles was calcium hydroxyapatite with Ca/P ratio of 1.55 whereas the main component of non-activated particles was calcium fluoroapatite (Ca/P ratio of 1.66). The results also indicated that activated rock material was mesoporous with a BET surface area of 57.4 m2/g. Results for water defluoridation showed that the material had a fluoride ion percentage removal of about 90%, when the adsorbent dose was 8 g, contact time of 30 minutes, initial fluoride ion concentration 5 mg/L, pH values of 6.0 to 7.2 and batch volume of 50 mL. The material could be regenerated using 1% NaOH and reused in the water defluoridation process. Therefore, Minjingu Phosphate Rock (MPR) is potential water de-fluoridatant.

Minjingu phosphate rock availability in low-pH highly weathered soil as affected by added salts

Concentrations and identity of ions in the soil solution may affect soil phosphorus (P) reactions and P availability. In this study, the magnitude of these reactions was evaluated following the application of Minjingu phosphate rock (MPR) combined with chloride and carbonate salts of Na and Ca within an incubation experiment. Twenty-one days later NaOH-P and HCl-P were determined. This investigation was undertaken with the aim of identifying the role of Ca-ion activity in the liquid phase on the solubilization of MPR and formation of insoluble Ca-P phases. The increase in pH was higher with Na2CO3 than with CaCO3, while both CaCl2 and NaCl resulted in slight decreases in pH. The dissolution of MPR was higher overall when MPR was applied singularly than for the combined application of the phosphate rock with salts of calcium or sodium after 60 days of incubation. Dissolution of MPR decreased as levels of CaCO3 or CaCl2 increased but the decrease was more pronounced in CaCO3-treated than in CaCl2-treated soils. Ca-ion activity in the liquid phase is the main factor responsible for the insolubilization of MPR and the formation of insoluble Ca-P phases (HCl P). The formation of Ca-P solid phases increased with the concentration of Ca-ions, and was governed by the pH and nature of the accompanying anion. For soils with low levels of exchangeable cations and where liming is a recommended intervention measure, Ca from lime will form insoluble P phases and reduce the dissolution of PR and P availability to plants.

Dry Bean Response to Fertilization Using Minjingu Phosphate Rock and Composted Tughutu (Vernonia subligera O. Hoffn)

Aims: The objectives of the study were toevaluate the effects of organic materials from Tughutu (Vernonia subligera O. Hoffn) and locally available Minjingu phosphate rock or commercial Triple super phosphate fertilizer on the plant growth and amount of phosphorus (P) and calcium (Ca) content in bean shoots (Phaseolus vulgaris L.) and their residual effects in the soil after harvest. Study Design: The experiments were set up as a randomized complete block design Place and Duration of Study: Field experiments were conducted in famers’ fields in the Western Usambara Mountains in Tanzania. Methodology: Each farmer’s field was assigned as a replicate. The experimental treatments consisted of six plots as follows: control, Minjingu Phosphate Rock (MPR) or Triple Super Phosphate (TSP) each at 26 kg P ha, Tughutu at 2.5 t dry matter ha and Tughutu at 2.5 t dry matter ha combined with Minjingu Phosphate Rock or Triple Super Phosphate at 26 kg P ha. Results: The dry matter yield and amount of P and Ca in bean shoots significantly increased by supplying the organic and inorganic fertilizers above the control treatment. Addition of P fertilizers alone or in combination with Tughutu also modified the soil pH and significantly increased the concentration of P and Ca in the soil at harvest. Conclusion: Overall, combination of Minjingu phosphate rock or Triple super phosphate with Original Research Article Ndakidemi; AJEA, 6(1): 51-59, 2015; Article no.AJEA.2015.064 52 Tughutu enhanced the effectiveness of these fertilizers and resultedin better growth and greater P and Ca amount in the shoots as well as their concentration in the soil at harvest.

Effect of Sources of Phosphorus on Phosphorus Sorption in Cambisols and Ferralsols of Western Kenya

The influence of two organic materials (OMs); Tithonia and FYM and inorganic materials; triple superphosphate (TSP) and Minjingu phosphate rock (MPR) and Busumbu phosphate rock (BPR), when applied alone or in combination, on P sorption at two sites, Kakamega and Bukura, in western Kenya was investigated. The soil at Bukura was a Ferralsol while that at Kakamega was a Cambisol. A randomized complete block design with 3 replications was used. All the P inputs were uniformly broadcast on the plots and then incorporated into the top soil (0-15 cm) in April 2007. Soils were sampled at 4 and 9 weeks after incorporation of phosphorus inputs (WAI) from each of the treatments and the soil P sorption characteristics determined. The equilibrium P concentration which represents the amount of P in the equilibrium solution at zero P sorbed was < 0.2 mg P L regardless of the input combination used. The P sorption capacity of the soil at Kakamega was low compared to that at Bukura and was generally not affected by the treatments. None of the P sources significantly reduced the amount of P sorbed at Kakamega. However at Bukura, the amount of P sorbed (q) was significantly lower than the control for only Tithonia when applied alone and FYM applied in combination with TSP at 4 and 9 WAI. Tithonia applied with TSP Original Research Article Opala; IJPSS, 6(2): 64-72, 2015; Article no.IJPSS.2015.097 65 significantly reduced q at 4 WAI but not 9 WAI while FYM applied alone was able to lower q at 9 WAI. None of the inorganic P sources, when applied alone, reduced the P sorption capacity of the soils. The results demonstrate that OMs have the potential to reduce P sorption in soils that are high in P sorption, but where the P sorption is relatively low, the application of OMs to reduce P sorption may not be useful.

The Effects of Phosphate Fertilizers and Manure on Maize Yields in South Western Kenya

Phosphorus, nitrogen and Striga hermonthica are the major constraints to maize production in the Nyanza Province of Kenya. Field trials were conducted on-farm in Nyanza Province to investigate the effects of phosphate fertilizers and manure on maize yields. The experimental design was a Randomized Complete Block Design (RCBD) with maize as the test crop. The maize was top dressed with calcium ammonium nitrate (CAN) fertilizer at a uniform rate of 30 kg N/ha diammonium phosphate (DAP), Minjingu rock phosphate (MRP) and triple super phosphate (TSP) fertilizers were applied at 60 kg/ha P2O5, farmyard manure (FYM) at 10 t/ha and a non-phosphorus (P) treatment (control) plus lime only. Responses (P ≤ 0.01) from grain yield, total dry matter yield and harvest index to phosphate fertilizers and manure treatments were found. Nutrient uptake and removal by the crop increased (P ≤ 0.01) due to fertilizers and manure application. Phosphate fertilizers and manure application increased (P ≤ 0.01)) available soil P, agronomic phosphorus use efficiency (APUE) and Physiological P use efficiency (PPUE). The results indicate that phosphate fertilizers and manure applications are essential to improve maize yield and nutrient P use efficiency.