Department of Soil and Geological Sciences

Permanent URI for this communityhttp://10.10.97.169:4000/handle/123456789/23

Browse

Now showing 1 - 5 of 5

Effect of liming acid soils on physico-chemical characteristics of the soils and coffee seedling vigor in Mbozi District, Tanzania
(Sokoine University of Agriculture, 2019) Mfaume, D. P.
Soil acidity is one of the most important soil factors affecting crop growth and ultimately yield and profitability of coffee in Mbozi District Tanzania. Soils tend to be naturally acidic in areas where rainfall is sufficient to cause substantial leaching of basic ions such as calcium and magnesium, which are replaced by hydrogen ions. Most soils in Mbozi District are acidic due to high rainfall and/or the use of soil acidifying fertilizers over a long period of time. Low soil pH causes aluminium and manganese toxicities while calcium, phosphorus and magnesium become deficient. In order to counteract the situation, liming is inevitable. This study was conducted on Ultisols of Mbimba sub- station, located in Mlowo Ward, Mbozi District, Songwe Region Tanzania. The study area is located within latitudes 9 0 05’35.97”S and 9 0 05’13.10”E and longitudes 32 0 57’14.51”E and 32 0 57’22.32”E. The area experiences mean annual rainfall ranging between 1 000 and 1 500 mm with a monomodal distribution pattern. The study aimed at increasing soil productivity for coffee through the use of agricultural lime and ultimately improve livelihoods of the coffee farmers in Mbozi District. Different levels of dolomite lime at 0 kgha -1 , 1 000 kgha -1 , 2 000 kgha -1 and 2 500 kgha -1 were used whereby NPK (22.6.12 +3S) at 150 kgha -1 was used at basal application rate. The field layout was set in a randomized complete block design with three replications. The results indicated that lime at 1 000 kgha -1 and 2 000 kgha -1 increased soil pH between 0.22 and 0.97 units and the increase of P was significant at P<0.001. Lime applied at a rate of 2 000 kgha -1 increased available P concentration by 5.73 - 7.28 mgkg -1 while exchangeable Potassium concentration increased by 0.14 - 6.01mgkg -1 in all 3 levels of lime and K increase was significant at P = 0.05. Soil Ca and Mg increased between 0.19 and 6.82 cmol(+)kg -1 and 0.54 - 1.98 cmol(+)kg -1 respectively after application of dolomitic lime. Plant height increased between 60.4 and 67.1 cm, branches between 29-31, internodes between 23 and 27, canopy width between 74.7 and 79.5cm and stem girth between 8.2 and 9cm. A very strong positive correlation was found between lime and Mg (R 2 = 0.8643), moderate positive correlation between lime and N (R 2 = 0.4453), between lime and P (R 2 = 0.7064), between lime and K (R 2 = 0.4043), between lime and Ca (R 2 = 0.5288) while weak correlation between lime and Na (R 2 = 0.2007. Correlation value of < 0.4 is considered as weak, 0.4 - 0.8 moderate correlation and 0.8˃ as very strong correlation. Thus, the study recommends the use of 2 000 kgha -1 of CaMg(CO 3 ) 2 lime to be used by Mbimba Mbozi farmers in coffee farms.
Effects of limestone, Minjingu phosphate rock and green manure application on improvement of acid soils in Tonga Butare, Rwanda
(Sokoine University of Agriculture, 2003) Nabahungu, Leon Nsharwasi
A study was conducted under pot and field conditions to assess the effects of limestone, Minjingu Phosphate Rock (MPR) and green manures (GMs) on maize yield, soil properties and nutrient uptake. The treatments tested in the greenhouse experiment were four rates of limestone applied either alone or in combination with MPR and/or green manures. In the field experiment, 13 treatments were tested namely an absolute control, recommended rate of NPK and burned lime, NP and limestone, combinations of any two of the following materials: limestone, MPR, Tithonia GM, Tephrosia GM, and combinations of three of these amendments. Soil analysis at the beginning of the experiment revealed that the soil was deficient in N, P, and K, had low levels of Ca and Mg and toxic levels of exchangeable AI. Application of GMs improved the supply of N and K appreciably while limestone played a great role in reducing exchangeable AI. A significant contribution of P was from MPR. A combination of MPR, GMs and limestone supplied ample amounts of N, P, K, Ca, Mg and reduced exchangeable AI and hence resulted into high yield. However, high rates of limestone decreased DM yield and nutrient uptake in the treatment with three amendments. A significant increase in DM yield was obtained in pots, which received a combination of low rate of limestone (1/4 of the lime requirement), MPR and GMs. In general Tithonia application gave higher yields than Tephrosia. These results were consistent with the higher quality of Tithonia biomass relative to Tephrosia biomass. The green manures in combination with MPR increased P uptake significantly. Nutrient concentration data from both field and pot experiments indicated serious deficiencies of P, K and N consistent with soil analysis data but Ca, Mg, Zn and Cu were in the sufficiency range. Furthermore, the results indicated that using a combination of moderate rates of limestone, MPR and GMs is the best strategy in improving acid soils in Tonga, Rwanda.
Phosphorus adsorption and its relation with soil properties in acid soils of Western Kenya
(Department of Soil Science Sokoine, University of Agriculture, Tanzania., 2014-10) Muindi, E. M.; Mrema, J. P.; Semu, E.; Mtakwal, P. W.; Gachene, C. K.; Njogu, M. K
Low available phosphorus (P) is one of the major hindrances to crop production in acid soils of western Kenya. Although considerable work has been done to establish P levels in the region, there is paucity of information on which to base fertilizer recommendations due to potential crop production differences caused by different soil types and climate. Phosphorus adsorption capacity and its relationship with some soil properties were evaluated in acid soils from nine locations of western Kenya. Adsorption data was obtained by equilibrating the nine soil samples with 30m1 of KH2PO4 in 0.01 M CaCl2, containing 0, 80, 150 and 300 pg m1-1 for 48 hours with shaking for 30 minutes at intervals of 8 hours. Langmuir, Freundlich and Tempkin adsorption models were fitted to the test results and relationship between P adsorption and soil properties determined by correlations. The result of this study showed that the soils were strongly to extremely acidic (pH 4.83 - 3.76), had high exchangeable Al3+ (>2 cmol Al kg-1), Al saturation of (> 20% Al) and calculated maximal phosphorous adsorption varied from 770.83 to 1795.83 mg kg' soil. Comparing the models, Freundlich linear model showed a better fit to the tested soils compared to Langmuir and Tempkin models. The regression coefficients (R2) for the fitted Freundlich P adsorption isotherms was highly significant ranging from (0.995- 1.000) for all tested soils. Analysis of relationship between adsorption maximum and soil attributes revealed that adsorption maximum positively correlated with clay content, exchangeable P, exchangeable acidity and Aluminium saturation and negatively correlation with organic matter and electrical conductivity. Due to differences in maximal P sorption capacities within the tested area, blanket P fertilizer recommendation may affect crop productivity in some sites. There is therefore need for further research to determine optimal Phosphorus requirements for soils in each research site.
Phosphorus retention and the interactive effects of phosphorus, lime and tillage on maize in acid soils of the Kenya Highlands
(Sokoine University of Agriculture, 2016) Muindi, E. M.
Maize (Zea mays) is the most important food crop in Kenya. However, its productivity is greately constrained across the Kenya highlands. Soil acidity and low available phosphorus (P) are among the major hindrances to maize production in acid soils of the Kenya highlands. A survey, greenhouse experiment and field trials were carried out to assess the extent of soil acidity, soil nutrient levels and common soil management practices by farmers that contribute to the poor growth performance of maize in the Kenya highlands. The study also sought to evaluate the interactive effects of tillage, P and lime on maize yields in the acid soils of the Kenyan Highlands. The survey was carried out in nine counties across the Kenya highlands namely: Meru, Embu, Kirinyaga, Nyeri, Kiambu, Nyandarua, Siaya, Busia and Eldoret. Soil acidity and nutrient levels were determined on soil samples taken from the study sites, while farmers’ practices were established by administration of a structured questionnaire. Phosphorus adsorption rates and lime requirements of the soils were also evaluated. The adsorption data were fitted into the Langmuir and Freundlich adsorption equations and the relationships between sorbed P and soil properties determined by correlations. Evaluation of the interactive effects of lime, phosphorus and aluminium was carried out by establishment of a greenhouse pot experiment at Waruhiu Farmers Training Centre, Githunguri - Kiambu. Extremely acidic (pH 4.48) and strongly acidic (pH 4.59) soils were used for the study. Four lime (CaO) rates and phosphorus (Ca (H2PO4)2 rates were used. The liming rates were: 0, 2.2, 5.2 and 7.4 tonnes ha-1 for the extremely acidic soil and 0, 1.4, 3.2, and 4.5 tonnes ha-1 for the strongly acidic soil. Phosphorus application rates were: 0, 0.15, 0.30 and 0.59 g P kg-1 soil for the extremely acidic soil and 0, 0.13, 0.26, and 0.51 g P kg-1 for strongly acidic soil. The experiments were a 42 factorial laid down in a Randomized Complete Block Design (RCBD) and replicated three times. After the greenhouse experiment, field experiments were carried out during the 2014 long rains and 2014/15 short rains in Waruhiu Farmers Training Centre, Githunguri, Kiambu County. The objective of the study was to assess the interactive effects of tillage, P and lime in the management of soil acidity, P-uptake and maize growth performance. Tillage practices evaluated included: ploughing, strip tillage and use of hand hoe while fertilizer lime combinations included: DAP + lime (DAPL), TSP + lime (LP), TSP alone (P) and lime alone. The experiment was laid down in the Randomized Complete Block Design (RCBD) with split plot arrangement. Lime and P rates applied were 3.2 tonnes ha-1 and 52kg P ha-1, respectively. Data collected included: maize plant height, number of leaves, internode interval, P-uptake at 30 days after emergence and at tasseling stage, grain yield, and soil chemical characteristics. Information gathered through personal interview via questionnaires revealed that most farmers (>96%) were not aware of the soil acidity problems and management strategies. The farmers also lacked sources of information about new technologies or innovations and < 37% were members of farmers’ training groups. Additionally, among the 4% who were aware of soil acidity, only less than 8% had ever tested their soils for soil acidity. Farmers who had applied lime on their farms at least once were also < 3% in all sites. On the basis of overall soil fertility manangement, >80% of the farmers in the research area applied both fertilizer and manure in their farms, with the majority using diammonium phosphate (DAP), calcium ammonium nitrate (CAN) and farmyard manure. However, a negative balance was identified between livestock keeping and fertility manangement, with <8% of the farmers returning crop residues back to the farm. Correlation analysis showed that there were significant relationships (P ≤ 0.05) between farmer education level, farmer training groups, fertilizer usage and crop yields. It is, therefore, concluded that more farmers’ awareness is critical for effective manangement of acid soils in the Kenya Highlands. Soils in all the study sites were strongly to extremely acidic (pH 4.83 - 3.76), had high exchangeable Al (>2 cmol Al kg-1), and high Al saturation (> 20% Al), which most maize germplasms grown in Kenya are sensitive to. The cation exchange capacity was low (CEC < 15 cmol kg-1) in Siaya, Busia and Eldoret while available P was low (<10 mg P kg-1 Bray 1) for all sites. The P adsorption data showed that average maximal adsorbed P of the soils were high (1 383- 2 238 mg kg -1 soil) while SPR varied from 189.43 mg P kg-1 in Eldoret to 529.76 mg P kg-1 in Nyeri. Freundlich P adsorption isotherms were found to have the best fit for all the tested soils (r2 = 0.882 - 0.990). Additionally, analysis of the interaction between P adsorption maxima and soil properties revealed that there was a positive relationship between P adsorption maxima and clay content, extractable P, exchangeable acidity and aluminium saturation. Conversely, organic matter and electrical conductivity negatively correlated with P adsorption maxima. Greenhouse pot experiments revealed that there existed good lime-Al-P interactions in acid soils of the Kenya Highlands. The interactions significantly (P ≤ 0.05) increased soil pH, extractable P, Ca, plant P uptake and maize yields. The interactions were also found to negatively affect exchangeable Al, oxalate Al, dithionate Al and P adsorption levels in the soils. Use of 7.4 tonnes ha-1 lime for the extremely acidic soils and 4.5 tonnes ha-1 or the strongly acidic soils significantly reduced exchangeable Al and standard phosphate requirement (SPR) by > 70% compared to lower lime rates. Similary, use of 0.59 mg P kg-1 soil reduced SPR of the soil by 40% while 0.51 g P kg-1 reduced SPR by > 73% in strongly acidic soils. It was, however, observed that there was no significant difference between combination of 7.4 tonnes ha-1 with either 0.59 g P kg-1 or 0.3 g P kg-1 in extremely acidic soils or combination of 4.5 tonnes ha-1 with either 0.51 g P kg-1 or 0.26 g P kg-1 in strongly acidic soils. This shows that the lower lime and P rates can be efficient in the management of soil P in these soils. Analysis of the relationship between lime and P availability showed that liming significantly (P ≤ 0.05) and positively correlated with soil pH, available P, exchangeable Ca, Langmuir maximum adsorption constant and Langmuir constant related to binding energy. Lime also negatively correlated with SPR and exchangeable Al. It was, therefore, concluded that lime and P positively interact to reduce Al and P adsorption in acid soils in the Kenya highlands. Further research is, however, required to evaluate the short and long term effects of the lime-P interaction on crop yields, availability of other plant nutrients and the soil environment under field conditions. Results from field experiment revealed that tillage-P- lime interactions significantly (P ≤ 0.05) increased soil pH, available P, CEC, Ca, maize growth, maize plant P-uptake and yields, and reduced soil exchangeable Al. Plough-LP interactions significantly (P ≤ 0.05) led to > 90% increase in soil pH, extractable P, CEC, Ca, and > 90% reduction of exchangeable Al as compared to the control. Plough-DAPL interactions on the other hand also led to > 96% increase in soil CEC and extractable P. Similary; plough-DAPL and plough-LP interactions significantly (P ≤ 0.05) increased maize plant height, P- uptake, drymatter yields and grain yields. Plough-DAPL or LP interactions significantly increased grain yields by > 70% as compared to the control treatment. Integrating plough with either DAPL or LP was, therefore, found to be effective in the manangement of soil acidity for increased maize production in Kiambu in the Kenya highlands. Further research is, however, required to ascertain the longterm effects of the integration on maize production, soil acidity and overall soil fertility status of the soils in the Kenya highlands.
Potential of phosphate solubilising bacteria for enhancing Minjingu rock-phosphate solubility and phosphorus-use efficiency for sustainable maize production in acid soils
(Sokoine University of Agriculture, 2021) Kwaslema, Damiano Raphael
Maize is a primary staple crop for over 80% of Tanzanians, accounting for more than 70% of the country's starch requirements. Small-scale farmers produce the majority of the crop, with production unpredictable and inconsistent with agricultural requirements. Despite the fact that total maize production has increased over the last decade, owing primarily to extensification, yields per unit area remain low, averaging around 1.6 Mg/ha and translating to just 17.8 to 26.7 percent of the feasible yield. In order to fulfill the demands of the country's fast rising population, maize production must be increased. Low soil fertility, which has been related to inadequate fertilization and poor soil fertility management practices, is one of the reasons for low maize production. Soil phosphorus (P) insufficiency is one of the most critical soil fertility concerns in most Tanzanian soils, owing to the preponderance of soils with high Phosphorus-fixing capacity. Water-soluble P fertilizers (WSF) and local rock phosphates (RP) have been advised to ease the P deficit problem. While WSF are agronomically very effective, their application is limited due to their expensive cost, whereas directly applied RP are associated with delayed agronomic effectiveness and low plant phosphorus consumption efficiency. A potent solution to the low reactivity of RP is its co-application with phosphate- solubilising microorganisms (PSMs) in an appropriate carrier or carbon source. PSMs are soil microorganisms, capable of converting the insoluble P sources into its plant available forms. When co-applied with RP, PSMs could help solubilize the insoluble P in RP. However, there is limited knowledge on PSMs characterized and selected based on their ability to solubilize local phosphate rocks while utilizing locally available, naturally occurring organic carbon sources. To evaluate potentials of PSB-RP combination of maize productivity, the first specific objective was set to characterize phosphate solubilising bacterial (PSB). Forty (40) PSBs were previously isolated from various agricultural fields in eastern and southern highlands of Tanzania. Eleven (11) Isolates were selected, molecularly identified, screened for plant-growth promoting traits such as (1) ability to solubilize three P-sources namely ferric-, tricalcium-, and hard Minjingu rock phosphate, (2) Indole Acetic Acid (IAA) production, (3) Siderophore production, (4) Ammonia gas production, (5) Hydrogen cyanide (HCN) gas production, and (6) Activity against phytopathogenic fungi. The second objective was to examine the influence of organic carbon sources and fertilizer- grade nitrogen sources on phosphate solubilising abilities of PSBs. Three organic carbon sources namely Molasses (ML), sunflower seedcake (SC), and filter mud (FM) were initially evaluated for their physicochemical properties according their comparative potentials to enhance solubilisation of Tri-calcium phosphate (TCP) and Ferric phosphate (FP) by ten PSB isolates. In place of glucose, 20 g per liter of either ML, SSC or FM were added in Pikovskaya Agar (PVK) broth. Accordingly, a double-modified synthetic minimal media (dSMM) was prepared which contained all components of the Pikovskaya broth, except the carbon and Nitrogen source. The third objective focused on evaluating the influence of organic carbon sources and fertilizer-grade nitrogen sources on antifungal efficiencies of PSB isolates against phytopathogenic fungi. Each of the PSB isolate was grown in the modified synthetic minimal agar medium supplemented separately with either ML, SSC, FM, or glucose as the sole source of carbon. Accordingly, agar plates were spot-inoculated with different PSB isolates on one end of the 9 cm diameter Petri dish and test fungi on the other end. Antifungal efficiency (AE) of each PSB under each treatment was determined. Lastly, influence of co-application of MPR and PSBs in a molasses-based carrier was evaluated for enhancing maize yield and phosphorus use efficiency. Field experiments were laid out in randomized complete block design in quadruplicates under two sites, Madaba and Magadu, respectively located in the southern highlands and eastern zones of Tanzania. The soils of each study area were characterized for soil fertility parameters. Experimental treatments were PSB inoculum co-applied with varying P rates (0, 20, 40, 60, and 80 kg P /ha) from MPR. Two P rates without PSB inoculum (0 and 40 kg P /ha) were set respectively as absolute and positive control. Soil available P, maize grain yield, biomass yield, phosphorus uptake, and use efficiency for each treatment were evaluate at harvest maturity. The results indicated that six bacterial isolates had the highest homology with the known strains of the genus Klebsiella, two isolates related to the strains of genus Burkholderia, while one isolate is still unidentified. All PSB isolates were positive for ammonia production test with highest amount being 168.3 ug/ mL produced by Klebsilla sp.- NA19a while none of the isolates exhibited ability to produce hydrogen cyanide gas. The highest amount of IAA produced was 24.32 ug/ mL by Klebsilla sp.- SI-SP1. Similarly, Klebsilla sp-NA5 showed a significantly (P≤ 0.05) bigger solubilisation index on ferric phosphate agar plate while K. variicola spp.-MdG1 showed highest solubilisation index on ZnCO 3 agar plates. All the eleven isolates inhibited growth of F. proliferatum on agar plates with the highest inhibition of 47.7% by Burkholderia sp.-MK10. Among organic carbon sources tested, molasses significantly (P ≤ 0.05) enhanced solubilisation of both tri-calcium and ferric-Phosphates compared to filter mud or sunflower seedcake while urea-containing media resulted into a significantly (P ≤ 0.05) lower amount of P-solubilized as compared to fertilizer-grade or laboratory-grade ammonium sulfate (SA) as N source. The evaluation of antifungal activity showed that the use of molasses as carbon source retains most of antifungal activity of isolates but filter mud and sunflower seedcake do not. Fertilizer-grade SA enhanced the antifungal activity of most bacterial isolates than urea. Furthermore, the bacterial isolates under study retained their antifungal efficiencies whether yeast extract is included in the growth media. A study on field evaluation of RP-PSB co-application revealed the following. The characterized soils of both study sites were acidic and deficient of nitrogen, phosphorus, and potassium. The data collected at harvest time indicated that soil available P of both sites responded positively to increasing P rates from Minjingu rock phosphate + phosphate solubilising bacteria (Bio-rock). Unlike Magadu soil, sole application of PSB inoculum in soils of Madaba increased soil available P to values statistically comparable to applying either sole MPR at 40 kg P /ha or 20 kg P /ha + PSB inoculum. Compared to applying sole MPR at 40 kg P /ha, maize grain yield, P uptake and phosphorus use efficiency (PUE) were improved by inoculation of PSB combined with either 20 kg P /ha or 40 kg P /ha. It is recommended, for enhanced maize productivity and efficient use of phosphorus, co-application of PSB inoculum and Minjingu RP at 20 kg P /ha for the soils of Madaba and 40 kg P /ha for the soils of Magadu.

Browse

Browsing Department of Soil and Geological Sciences by Subject "Acid soils"