Theses and Dissertations Collection

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Effect of method of terracing on some physical and chemical properties of soils of Mgeta, Morogoro, Tanzania
(Sokoine University of Agriculture, 1992) Kisanga, Danielson Ramoz
A field experiment was conducted on cultivated sandy clay loam Chromic Cambisols at Mgeta on the slopes of Uluguru mountains. The objectives were to study the effects of terracing methods on some soil physical and chemical properties and to relate the results to crop performance observed in the field. The main treatments consisted of bench and ladder terraces. The subtreatments were three positions on the slope, and five 10 cm interval soil depth sections. The physical properties assessed were particle size analysis, bulk and particle densities and available water capacity. The assessed chemical properties included pH, CEC, exchangeable cations, carbon, organic total nitrogen, and available phosphorus. There available were significant water capacity, increases in exchangeable clay, silt, calcium and magnesium contents and a decreasing trend in very coarse sand particles along the slope under ladder terraces. In the bench terraces, bulk density increased slightly while total porosity decreased significantly along the slope. Most of the soil physical and chemical properties from the bench terraces were significantly different along the slope, but lacked a defined trend, Exchangeable cations, total nitrogen, and organic carbon for the two main treatments showed a decreasing trend from surface to the bottom of the soil profile. Other soil physical and chemical properties lacked defined trends with depth. The causes of the observed trends in the bench and ladder terraces are respectively attributed to the mechanical movement of soil and gradual but continuous transportation of fine soil materials by water down the slope. The variations in soil physical and chemical properties within and between the two treatments were attributed to the nature of the soils and methods used in the construction of the terraces. Variations in the studied soil properties account for the observed crop performance. In order to improve crop performance and maintain a sustainable crop production at Mgeta, several soil management and conservation measures are proposed.
Chemical and physical properties of some salt affected soils from Morogoro and Kilimanjaro regions, Tanzania
(Sokoine University of Agriculture, 2003) Gervas,Donald
A study was undertaken to assess the types and quantities of soluble salts in some soils of Morogoro and Moshi districts, Tanzania which have been suspected to contain substantial amounts of soluble salts that have contributed to poor crop performances. The selection of the sampling sites was based on soil information and crop performance gathered from the farmers, research and extension reports and soils and geological maps. In total 22 soil samples to the depth of 30 cm were collected from eight sites and analysed for the various soil properties for soil fertility characterization and properties used for the characterization of salt affected soils using the standard recommended procedures. The soils from the eight sites varied tremendously in terms of soil fertility status and amounts of soluble salts. Based on the pH, ECe, ESP and SAR, the soils of SUA Farm 1 and 3, Mafiga 2, Kahe 1 and 2, Kikafu chini 2 and Soko 3 were categorized as saline-sodic, those of SUA Farm 2 and 4, Kidamke 1, Mafiga 1, Kikafu chini 1, Soko 1, 2a, 2 and 4 as sodic, and those of Kidamke 2, and 3, Dakawa 1, 2, 3 and Cholima as not salt affected. The dominant cations and anions in the soils were sodium, calcium, sulphate, bicarbonates and assumed to be mostly Na2SC>4 and NaHCOs. The possible formation, development and accumulation of the soluble salts in the soils include weathering of rocks and accumulation due to poor drainage. For increased and sustainable crop production for the saline-sodic and sodic soils, the soluble salts and exchangeable Na, respectively, have to be reduced by leaching and neutralization using gypsum to levels suitable for chloride, respectively. The soluble salts in the saline-sodic and sodic soils were crop production. The growing of salt tolerant crops like rice could be another soilcrop management option for sustainable use of the saline-sodic and sodic soils.
Effect of ethylene dibromide on the control of white grubs and its impact on cordyceps in soils of the TPC sugarcane estate, Moshi, Tanzania
(Sokoine University of Agriculture, 2001) Kapama,Juma Tuwelango
The populations of white grub pest of sugarcane, and that of Cordyceps, a naturally occurring fungal pathogen of white grubs, were determined in the four fields of the TPC sugarcane estate. The effects of ethylene dibromide (EDB), a commercially Cordyceps. Also the contribution of Cordyceps as the biocontrol agent of white grubs was evaluated both in fields and in the laboratory. White grubs populations (in the four fields) varied significantly among four selected Fields with grub densities varying from 25 000 to 93 000 grubs per hectare. These variations were possibly due to differences in field location and soil types and also the number of crop ratoons. Similarly the populations of Cordyceps differed significantly between fields ranging from 600 to 4000 Cordyceps clavac per hectare. The variations were attributed by initial population of white grubs, and soil properties. Ethylene dibromide significantly reduced the populations of both white grubs and Cordyceps in the treated plots, with maximum impacts al the third week after EDB application. In the laboratory, reduction in the population of white grubs by EDB was consistent to the sliding scale of concentration. Although EDB reduced significantly the germination of the Cordyceps clavae from infected cadavers, its effect on fungal growth and the branching of germinated clavac were not significant. Although estimated mortality of white grubs caused by Cordyceps in stress rearing experiment was low (0.27-27%), from field surveys the contribution of the fungus as a natural control agent of white grubs was very high (54-94%). Studies on the effect of EDB on non target organisms used soil fumigant, was assessed in controlling the white grubs and its impact on in sugarcane fields, and development of alternative white grubs control strategies which are sustainable and less harmful to the environment have been recommended.
Distribution and characterisics of calcretes and calcrete-soil profiles on the Northern lower slopes of Uluguru mountains in Morogoro, Tanzania
(Sokoine University of Agriculture, 1997) Sentozi, Eliab
This study was conducted on the area extending northwards from the footslopes of the Uluguru mountains towards the Ngerengere river. Kihonda transect was selected for detailed characterization of different calcrete forms and the associated soils and regolith so as to understand the origin of calcretes, their characteristics and their influence on soil properties. Near Ngerengere river, the calcrete layer is considerably thinner (27.5 cm) than those on the lower slope (76 cm), midslope (135 cm), crest (106 cm) and neighbouring depression (142 cm) implying the influence of Ngerengere river on calcrete formation. Less developed calcretes occur near the river while the most developed calcretes occur at or near the crest. Nodular, honeycomb and massive calcretes are the major forms of calcretes occurring on the transect. Their proportions along the transect which reflect their lateral extension follows the order: nodular (94.9%), honeycomb (87.2%) and massive (51.3%). A considerable difference in purity exists among different calcrete forms ranging from 47.6% in nodular calcrete, 75.0% in honeycomb and 97.5% in massive form. This difference in purity is explained in terms of their difference in degree of development. A sharp di (Terence in average CaCO3 content ranging from 7.7% in soil solum to 65.0% in calcrete layer exists. The latter implies a lithological discontinuity at the soil-calcrete interface. The difference is gradual from 65.0 to 37.7% at the calcrete-regolith interface. The source of the CaCO3 in the calcretes is therefore the underlying parent material. The calcretes are mainly constituted of micritic calcite. Sparite occurs on top of massive calcrete, in fissures, voids and around the relic minerals implying a multi-phase precipitation of calcite. Minor minerals are quartz, opaline silica and feldspars. The studied calcretes were formed during the last glacial period, about 41,000 or more years ago. The gravel and soil layers are considerably younger.
Influence of soil properties on the dissolution of Minjingu phosphate rock
(Sokoine University of Agriculture, 1999) Mwakisimba, John
Phosphorus is mostly supplied in the form of water soluble fertilisers which are very expensive. Thus resource poor farmers can not afford it. The price of Minjingu phosphate rock (MPR) is relatively lower and may substitute water soluble P fertilisers if found to be agronomically comparable to the traditional P sources. A study was conducted to investigate the extent of M'PR dissolution and extractability of P after dissolution of MPR and to determine soil factors controlling the dissolution of MPR and subsequent levels of extractable P in eleven Tanzanian soils. Also the adsorption characteristics of the experimental soils were determined. P adsorption maxima of the experimental soils ranged from 375.4 to 4110.2 mg P/kg and were directly influenced by A12O3. The amounts of P adsorbed at 0.2 pg P/ml ranged from 22 to 710 pg P/g. The soil with the highest P adsorption maximum had the highest P adsorbed at 0.2 pg P/ml. On the other hand, soils with substantial amount of P in equilibrium solution at zero added P had low P requirement. Some of the soils with high P adsorption maxima had low P requirement. The extent of MPR dissolution in the eleven soils tested ranged from 34 - 97 % of the applied P after 70 day (d) of incubation. High percentage (83%) of the variation in MPR dissolution was accounted for by three soil properties namely percent Ca saturation, OC and P retention capacity. Bray 1 P in the experimental soils ranged from 7.3 to 71.0 % of the dissolved P after 56 days of incubation, with an average of 29.6 % suggesting a high degree of fixation. Bray 1 P was also significantly related to exchangeable Al, Al saturation, soil pH, soil pH buffering capacity and OC. However none of these soil properties accounted for > 50 % of the variation in Bray 1 P. This implies that none of the independent variables tested adequately predicted the dependent variable. Results from this study indicate that MPR has high solubility in acid soils of pH < 5.8 and should thus be evaluated for direct application under field conditions.
Influence of seed storage practices on germination, growth, and yield of Bambara groundnut [Vigna subterranea (L.) Verde].
(Sokoine University of Agriculture, 2003) Mkwachu,Seif Omari
Two experiments were conducted at Sokoine University of Agriculture to assess the influence of storage containers, seed shells and priming treatment on germination, growth and final seed yield of bambara groundnut [Vigna subterranea (L.) Verde.]. Good quality seeds with germination of 95% were stored unshelled and shelled using germination test was conducted as per ISTA methods after priming seeds stored in different containers by soaking for 24 hours, wetting prior to germination with dry germination as the control. The results indicated that germination percentage was decreased in seeds stored in various containers and primed by different treatments. Storing seeds unshelled gave the higher germination of 10.07% compared to those stored after shelling which gave germination of 6.34%. Significant differences (P < 0.05) between storing in different containers were observed. Shelled seeds stored in deep freezer were the best in germination (27%) followed by unshelled seeds stored in basket and hanged over the fireplace (21.94%). Seeds stored in plastic bucket were the least with only 1.45% germination. Also container differences in maintaining 100 seed weight, seed moisture content and proportion of carbohydrate in food reserve was observed. Germination percentage was positively correlated to 100 seed weight (r = 0.88**) and to proportion of carbohydrate in seed food reserve (r = 0.51”3) but correlated negatively to seed moisture content after storage (r = -0.47ns). Strong negative correlation was recorded between seed moisture content and proportion of carbohydrate in seed food reserve (r = -0.93**). This study has shown that differences seven different storage containers for a period of six months. After sixth months, in seed quality induced by different storage containers have major effects only on germination and mean relative growth rate at early growth stages. No significant differences in mean relative growth rate at later growth stages and partitioning coefficients of plants from surviving seeds were observed. Soaking bambara groundnut seeds for in water 24 hours significantly accelerated germination and early seedling growth. No significant differences in yield were observed between priming treatments tested. Based on the results in this study, storing of unshelled bambara groundnut seeds in jute bags or woven basket and hanged over the fireplace is recommended. However, further study is recommended to assess the role of pod drying methods in seed deterioration during storage
Bodemkundige inventarissen : kwaliteit en evaluatie karakterizering, van hun geschiktheid voor specifiek landgebruik / Soil resource inventories : characterization, quality and evaluation of for their adequacy specific land use
(State University of Ghent, Belgium, 1987) Msanya, Balthazar M.
In many countries a lot of soil resource inventories (SRIs) particularly soil surveys have been made and are still being made. Their objectives are generally well stipulated and known, yet there are indications that these documents are not sufficiently being used both in developing and developed countries. It is against this background that the present study was started. The intention has been to look for ways of characterizing SRIs and to evaluate their adequacy for specified land uses. This way it was hoped that reasons behind the limited use of such documents could be identified and hence help to frame recommendations for future soil inventories. The data base in this study comprises (a) a total of 176 soil survey reports (including accompanying maps) from 46 countries, (b) 70 70 completed questionnaires from soil surveyors representing 40 countries and (c) 94 completed questionnaires from users of soil maps and reports representing 35 countries. Using the 176 SRIs, a general inventory of the documents was made as a first attempt to characterize them. Then indices to characterize the SRIs in terms of their cartographic attributes were developed. These indices were highly correlated with each other. Other observations on cartographic attributes indicated that (a) the concept of map linear reduction factors is not consistently used and (b) information on soil description sites is only rarely given in SRIs. In relation to the information content of map legends and soil reports it was observed that (a) most SRIs are produced by free survey method; (b) the most commonly used attributes in soil mapping are texture, drainage, landform, topography, parent material and soil depth; (c) information on density of field observations is often lacking in SRIs and is commonly vaguely presented; (d) USDA and FAO/Unesco classification systems are the most widely used internationally; (e) most SRIs contain interpretive data and (f) information on purity of mapping units is often not given in SRIs and in many cases only partly presented. Two methods are developd and described for estimating the utility of base maps. It was noted that many SRIs do not bear information about their compliance with specified base map accuracy standards. With regard to general legibility of SRIs, it was observed that (a) provision of instructions on how to use the SRIs is mostly neglected and (b) glossary of specialized terminology and ranges of soil properties of mapping units are commonly not provided in the documents. A method is developed and described for characterizing and systematically evaluating information given in map legends and soil reports about mapping units in function of specified land uses. Furthermore, a comprehensive method is also described for the assessment of the predictive adequacy of SRIs for three land uses in function of (a) cartographic attributes, (b) map legend and soil report attributes and (c) base map attributes. Guidelines outlining the assessment procedure are provided. This method was applied on 66 selected semi-detailed and detailed SRIs from 17 countries. Following strictly the stipulated criteria of adequacy it was found that only about 27 « of the documents are completely adequate for predicting performance of both corn and oil palm, and about 30 % can be considered adequate for predicting performance of Eucalyptus deglupta (forestry). A preliminary study on the adequacy for prediction of soil erosion hazards was done on 50 selected SRIs from 18 countries, Based on the adequacy criteria per se, it was found that most of the documents could be said to be adequate for the use in question, It was also noted that (a) although information on climate is given in all documents, winds are frequently not described; (b) information on topography is normally limited by the lack of contour lines printed with soils information or the lack of contour maps appended to the soil maps and (c) information on soil permeability is often not described. Analysis on the answers given by respondents of the questionnaire to soil surveyors shows that (a) soil surveyors to a great extent determine the nature of SRIs to be made and only occasionally do users have the opportunity to do so; (b) some terminologies and criteria used in soil survey eg. soil survey intensity, field soil mapping procedures and purity of mapping units are not conceived and used consistently; (c) most soil surveyors do not monitor utility of the SRIs they make; (d) soil maps are sometimes too complicated and (e) publicity about SRIs has not sufficiently been made. The results from the questionnaire to users of soil maps and reports indicate among other things that (a) soil surveys are still considered very important in development projects; (b) there are problems of knowing about the existence of soil maps, yet communication media such as radio, television and newspapers have not been used significantly to ameliorate the situation; (c) major problems encountered while using soil maps and reports include poor legibility, problems of location on the maps, use of vague and in some cases complicated terminology, A revised questionnaire to users of soil maps and reports has been proposed to accomodate changes that will take it more useful as a source of information. To put everything in a nutshell, it can be said that indeed, existing SRIs do present serious bottlenecks that need attention in future inventories. For this a series of recommendations has been suggested at various levels of the study.
The use of mulberry (morus alba) dry leaves as a protein Supplement for Tanzania blended goats fed with low-quality roughage
(Sokoine University of Agriculture, 2001) Temu,Vitalis Wilbald Kisingo
A study was conducted to evaluate the effect of substituting Morns alba dry leaves (MDL) for sunflower seed cake (SSC) as a protein supplement on the performance of blended goats fed with poor quality roughages. In a growth study, 32 growing blended goats (4 to 7 months old) weighing 14±2.4 kg were randomly allocated to four dietary rations so formulated that MDL replaced 0, 50, 75 and 100% SSC as a source of supplementary nitrogen in treatments T, T, T3 and T4 respectively. There animal received an amount of its respective treatment ration estimated to meet its DCP requirements (adjusted fortnightly) for maintenance plus an allowance for 50 gd'1 live weight gain. Each animal was also given 10 and 2% of its estimated dry matter intake (DMI) as hominy meal (HM) and mineral mix respectively plus ad libitum fresh drinking water daily. After the 84 days of growth study, 3 males from each treatment were slaughtered for carcass yield and killing-out characteristics. Nutrient digestibilities and N utilization were measured in a digestibility trial with 4 treatment groups each with 3 mature males. Tj ration (100% SSC), was poorly accepted by the animals leading to slow growth rates and weight losses towards the end of the growth study. There were significant treatment effects on daily feed intakes with highest values in T3 and lowest in T,. Energy intakes were significantly (P<0.05) lower (2.6 MJ ME d'1) for T1 and higher for the other groups, which were not significantly (P>0.05) different. Tj animals showed poor growth but the other groups gained between 30 and 53 g d'1, the highest being for T4. Highest feed conversion ratio was in T, which differed significantly (P<0.05) from the rest of the were 8 animals (4 and 4 $) in each group. On top of the basal diet (hay) each iii treatments. Hot carcass weight (HCW) % of slaughter weight (SW), was highest in T, followed by T3, T4 and Tt in decreasing order. SW, empty body weight (EBW), HCW and gut fill were significantly (P<0.05) influenced by the treatments, the mean (P>0.05) treatment effects on gut fill. Yield of total edible non-carcass components was significantly (P<0.05) higher in T4 than T3, T2 and T,, the order being reversed when expressed as % of EBW. There were no significant (P>0.05) treatment effects proportions of lean in the sample joints from animals in all treatment groups. Sample joints from T, animals had the lowest fat and the highest bone proportions (P<0.05) than T2, T3 and T4 animals whose differences were generally small and insignificant (P>0.05). All treatment rations supported positive N balances, high in vivo feed digestibility with higher energy intakes being associated with rations containing higher levels of MDL. It was concluded that, MDL can substitute SSC as a protein supplement to growing meat goats without reduction in performance and that a better effect of CP supplementation is achieved when some SSC is offered together with M. alba preferably in the ratio of 25 : 75 (SSC : MDL) in terms of DCP contribution for meeting maintenance and a growth rate of 50 gd'1. The use of SSC as a sole protein supplement to growing goats on poor quality roughages is likely to cause low dietary energy intake leading to lower feed utilization efficiency.
Effects of some industrial organic wastes on maize grain yield and some soil properties
(Sokoine University of Agriculture, 2003) Timbula,Kastory Matembele
A study was conducted to evaluate paper sludge and pyrethrum marc as alternative sources of plant nutrients using maize as a test crop. The study was carried out at Magadu Morogoro, Tanzania. Kaaya (1989) classified the soil of Magadu as Oxic Haplustult. Laboratory analyses revealed the soil to be clay, compacted and acidic with low CEC (11.2 Cmol(+) kg'1) Total nitrogen, (0.09 %) exchangeable Ca (1.77 Cmol (+)kg‘‘ ) and Na (0.67 Cmol (-j-)kg'1 were low, exchangeable K (0.69 Cmol (-i-)kg'1) and Mg (1.51 Cmol (-r)kg'1 were high, extractable Fe (46.48 mg kg'1) and Mn (70.06 mg kg'1) were very high while Cu (1.14 mg kg'1) and Zn (0.51 mg kg'1) were adequate for plant growth. Four rates of paper sludge and pyrethrum marc (0, 10, 20, and 30 tons ha'1) on air-dry basis were applied to soil in a randomized block design. The wastes were characterized before incorporation into the soil. Paper sludge and pyrethrum marc were alkaline and acidic in reaction respectively. Paper sludge had high C/N (37.7) C/P (245) and Ca/Mg (105.22) ratios .The high C/N and C/P ratios mean that biological immobilization of nitrogen and phosphorus would be the major limiting factors for this waste to be used as a source of plant nutrients. High Ca/Mg ratio indicates that paper sludge can be used as a liming material. Paper sludge had lower sodium adsorption ratio (SAR) (0.22) as compared to pyrethrum marc (0.62). This suggested that sufficient Ca and Mg are present to counteract the negative effects of sodium. Levels of Fe (333.4) Mn (543.71) Cu (21.00) and Zn (42.9) for paper sludge and 107.55; 901.85; 14.4 and 51.00 respectively for pyrethrum marc, were well within the limits for environmental pollution. Maize grain yield in plots amended with pyrethrum marc increased from 0.64 to 3.33 tons ha’1 with increasing iii rate of pyrethrum marc while in plots treated with paper sludge grain yield decreased from 1.43 to 0.52 tons ha"‘as the rate of application of paper sludge increased. The Increasing the rates of the wastes ameliorated the bulk density from 1.50 tol.38 mg cmrivas associated with decrease in soil bulk density. For pyrethrum marc treated plots, soil pH, OC, total N, extractable P and exchangeable Ca, Mg, and Na and CEC increased with increasing rates of the waste. Cu and Fe were significantly lowrelative to the control, and Zn was higher than the control. Soil pH, exchangeable Ca and CEC of the plots amended with paper sludge increased with increasing rates of the material from 5.28; 2.61; 10.57 to 7.7914.74; 14.20 respectively. Increasing the rates of paper sludge had a negative effect on exchangeable Mg, K, Na, and extractable P. Total nitrogen and organic carbon were not statistically different from for the lowest rate and 0.81 mgkg'1 for the highest rate of paper sludge). Zn was not statistically different compared to the control, and Fe was significantly lower than the control. Both wastes alleviated Al and Mn concentrations remarkably
Effect of cultivar, rates, and time of nitrogen fertilizer Application on yield and yield components of lowland irrigated rice (Oryza sativa l)
(Sokoine University of Agriculture, 2003) Zakayo, Joel Absalom Moses
Nitrogen (N) is one of the major elements required by rice (Qryza saliva L) plants for growth and development. Nitrogen deficiency in rice is caused by losses of the element from the soil- plant system, mainly through denitrification, ammonia volatilization, leaching and runoff. Thus, careful management of N both in terms of rates and timing of application is essential in order to improve its utilization by the plants. An experiment was therefore conducted at Mkindo irrigation project in Mvomero district, Tanzania to evaluate the response of three rice varieties to different rates and times of N application. A split-split plot design with three replications was adopted. The main plots contained three rice varieties (TXD85, TXD306 and Supa). The sub- plots contained four rates ofN (0,40,80,and 120 kg N ha'1) while the sub-sub plot represented four times of N application (Tl=single dose in dry' soil before transplanting, T2=two equal splits: half dose each in dry soil before transplanting and at initial tillering, T3=three equal splits: one- third dose each in dry soil before transplanting, initial tillering and panicle initiation, T4=two equal splits: half dose each at initial tillering and panicle initiation). Dry' mass accumulation varied significantly (P<0.05) among treatments. Highest dry' mass accumulation was recorded in TXD 306 and the lowest in Supa. More dry' mass was attained with 120 kg N ha-1 applied as T4 and the lowest without N. Application of N as T4 gave the highest dry' mass, while the low'est with N as Tl. Grain yield increased significantly (P<0.05) with increasing N rates in cultivars TXD 85 and TXD 306 up to 120 kg ha' The yield increase in Supa w'as only up to 80 kg N ha'1 after which it declined. Time of N application significantly (P<0.05) affected grain yield in rice with highest Ill results suggest that grain yield increased proportionately with increased N availability in the soil. Grain yield variation among treatments was found to be associated with variations in the number of panicles/m2, panicle weight and number of grains/panicle. Among growth parameters, grain yield w'as significantly (P<0.01) influenced by grain dry mass, stem dry' mass, and total dry mass. Leaf dry' mass had no direct contribution to the observed variation in grain yield. Nitrogen use efficiency (NUE) varied among treatments. TXD 306 recorded highest NUE and low'est in Supa. Highest NUE w'as realized with low N rates (40 w'as therefore concluded that, economic optimum N rate for TXD 85 and TXD306 was 120 and 80 kg N ha’1, respectively, applied as T4 while for Supa was 40 kg N ha'1 applied as T4.
Effect of phosphate rock placement methods and incorporation of organic residues on phosphorus availability and maize yields in two soils with different phosphorus fixing capacities
(Sokoine University of Agriculture, 2004) Merumba, Mgeta Steven
A study was conducted under pot and field conditions to evaluate the effects of Minjingu phosphate rock (MPR) placement methods and organic residues on MPR dissolution, P availability and maize yields in two soils with different P fixing capacities. Observations from two field experiments, one at Sasanda, Mbeya and another at Magadu, Morogoro were continued to evaluate the effect of continued addition of organic materials (OM) banded with MPR on MPR dissolution, P availability and maize yields. One field experiment was carried out at Sasanda to evaluate the effects of different rates of OM applied together with MPR on MPR dissolution, P availability and maize yields. For the continued experiments, the treatments tested were control, broadcasted MPR, 2 to 5 cm width strip banded MPR, 20-cm wide MPR band incorporated to 10 or 20 cm depth, and 20-cm MPR band + O.M incorporated down to 10 or 20 cm depth. These were tested only in the field. For the new experiment the treatments tested were control, broadcasted MPR, 2 to 5 cm width strip banded MPR, 20-cm wide MPR band incorporated to 20 cm, and 20- cm band MPR + OM applied together at 2, 4, 6 and 8 t/ha and incorporated down to 20cm depth. Field experiments were laid using Randomized Complete Block Design (RCBD) with four replications while pot experiment was laid using Complete Randomized Design (CRD) with three replications. Dry matter yields (DM) yields, P uptake, P concentrations, extractable P and grain yields were used to assess the effects of these treatments. The results showed that continued incorporation of OM banded together with MPR significantly (P=0.05) improved MPR dissolution, P availability, and increased grain yields. This was supported by highest maize grain yield (3.01 t/ha) obtained from these continued observations, which was higher than the maximum (2.27 t/ha) obtained in the previous study from the MPR + OM incorporated down to 20 cm depth. The results of the new experiment showed that banding of MPR together with OM at the rates of 2, 4 6 and 8 t/ha significantly (P=0.05) increased MPR dissolution, P availability, and maize grain/ dry matter yields. The increase was in proportion to the increased rates of OM. For example, in the pot experiment, MPR + OM increased DM yields from 14.14 to 76.17 g/pot and 4.10 to 70.87 g/pot in Magadu and Sasanda soils, respectively. In the field experiment, MPR + OM at 2, 4 and 6 t/ha increased extractable P in the soil from 0.18 to 0.47 mg/kg and maize grain yields from 0.36 to 3.38 t/ha. The increase was also proportional to the increased rates of OM. The highest extractable P (0.47 mg/kg) and grain yields (3.38 t/ha) were observed from MPR + 6 ton OM/ha.
Strategies for establishing adequate phosphorus levels in three soils with different phosphorus fixing capacities
(Sokoine University of Agriculture, 2004) Eliuth, Stephan Ngailo
A study was conducted under pot and field conditions to establish adequate levels of phosphorus in three soils with different P fixing capacities. These soils were from Magadu, Morogoro District, classified as Oxic Haplustidt, Sasanda, in Mbozi District, classified as Drystropept and Nkundi in Nkasi District, classified as Acruoxic Kancliustult. A pot experiment was conducted at SUA- Department of Soil Science while field experiment was carried out at Sasanda in Mbozi District in Mbeya region. The treatments were 0, 40, 80 and 160 mg P/kg of soil for Nkundi, 0, 100, 200 and 400 mg P/kg of soil for Magadu and 0, 800, 1600 and 3200 mg P/kg of soil for Sasanda soil. For field experiment the treatments were 0, 800, 1600 and 3200 kg P/ha. The sources of P were TSP and MPR. There were seven treatments for field and eight treatments for pot experiment. The experiment was laid out in a Randomized Complete Block Design. The tested crop was maize {Zea mays var UH 615). The objectives of the study were to identify rates of P required for optimizing maize dry matter grain yields, and associated available P levels in the soils. Results of the study showed that, both TSP and MPR were effective sources of P in the soils studied. Both TSP and MPR significantly (P = 0.05) increased DM and grain yield, P uptake and available P over the control by 97.7, 95.8, 76,8 and 95.3%, respectively in Sasanda soil. This was attributed to 95.3% increase in available P in the soil after TSP and MPR application in Sasanda soil. This was supported by the highest grain yield, DM yield, and P uptake of 2.97 t/ha, 64.18 g, and 124.8 mg/kg at the rates of 3200 kg P/ha and 3200 mg/kg, respectively in Sasanda soil. However, MPR was slightly less effective than TSP for most of the aspects studied. The optimum rates were 160, 200 and 3200 mg P/kg for Nkundi, Magadu and Sasanda soils, respectively under pots. However, these rates have to be confirmed under field conditions. In Sasanda field experiment, P application did not significantly (P = 0.05) increase available P and the available P was below the critical level. This was attributed to high fixing capacity of the soil. The rale of 1600 kg P/ha gave the highest grain yield of 2.97 t/ha in the current study. Results from the current study indicated that MPR has the potential of supplying P for maize production therefore it could be used as an alternative source of P to TSP. A large, one-time application of P on highly P deficient soils is not always the solution for correcting P deficiency in all soils like in Sasanda soil. A gradual seasonal P application might be the most cost-effective approach for high P-fixing soils.
Agronomic evaluation of some industrial wastes as alternative sources of plant nutrients in Morogoro District, Tanzania
(Sokoine University of Agriculture, 2001) Ndaki, Stephen Mhoja Mashauri
A study’ was conducted at Magadu. Morogoro. Tanzania to evaluate the industrial wastes as alternative sources of plant nutrients and/or soil conditioners. The soil of Magadu was classified by Kaaya (1989) as Oxic Haplustult. The soil was characterised in this study for its physical and chemical properties prior to planting of the test crop. The analytical data showed that the soil was strongly acidic with a pH of 5.1. Total N. available P. %OC, exchangeable Ca and Na. CEC. and DTPA extractable Zn were in the low range. Exchangeable Mg was in the medium range, while exchangeable K. DTPA extractable Fe, Mn and Cu were high. In the field a randomised complete block design was used to evaluate the wastes using maize as test crop. The rate of waste application were 5.24 4.8, 4.25, 4.5 and 3.7 tonnes/ha of waste tea, wattle bark chippings, waste tobacco, wood ash and saw dust respectively. Prior to soil incorporation, the wastes were analysed for their chemical properties. Maize dry matter yields were significantly higher in plots which received 5.24 tonnes/ha of waste tea followed by plots which received 4.25 and 4.5 tonnes/ha of waste tobacco and wood ash respectively. Maize grain yields were significantly higher in waste tea and wattle bark chippings amended plots than in the other waste amended plots. At the end of the growing season the soil was analysed to evaluate the residual effect of wastes on soil properties. Soil pH, available water capacity, available P, % OC, total N, exchangeable bases, CEC, DTPA extractable Zn and Cu in waste amended plots increased in the top 15 cm of soil relative to the control plots. DTPA extractable Fe and Mn, exchangeable Al and acidity were significantly reduced in all waste treatments. Total N and % OC in wood ash and saw dust amended plots were at par with those found in control plots. The results from the field suggested that when applied at agronomic rates, industrial wastes can produce satisfactory plant growth and yields. The results revealed further that waste application on a long term basis will allow good build up of soil organic matter and plant nutrients which in turn will improve on soil productivity. It is recommended that N supplement to wood ash which is rich in almost all macro and micronutrients (except N) would balance its nutrient supply to plants. A glasshouse decomposition experiment was carried out with some wastes including sawdust and wattle bark chippings in perforated plastic litter bags. The wastes were either surface applied or buried to 10 cm depth in wooden troughs. The decomposition process which was monitored at 0. 3, 6, 9, and 12 weeks of incubation revealed that soil incorporated wastes decomposed and released nutrients faster than surface applied ones.
Effects of Land Degradation in the uplands on Land use Changes in the Plains: The case study of Chimala River Catchment in the Usangu plains
(Sokoine University of Agriculture, 2002) Mwalukasa, Emmanuel Hudson
A study was carried out in Chimala River catchment in Makete-Iringa (uplands) and Mbarali-Mbeya (plains), Tanzania to relate land use changes occurring in the plains to upland degradation. The objectives of this study were: (a) to establish land use/cover inventory for the catchment; (b) to assess upland vegetation degradation; (c) to assess upland soil erosion by gully expansion; (d) to assess catchment soil fertility status; (e) to assess the Chimala River water flow trend; and (f) to assess the socio-economic activities related to land degradation. Aerial photographs and satellite images were used, interpreted and analysed using GIS ArcView/ArcINFO and ERDAS Imagine softwares. Mean monthly water levels were compared using a student t-Test. Soil samples were collected from four different forest-covers for organic carbon (OC) content analyses. Total nitrogen (N) contents were estimated using C:N ratios. A structured questionnaire and SPSS programme were used to collect and analyse socio-economic survey data. Results showed that upland grassland decreased by 3.6% and 45.8% for 1963-77 and 1977-2001 periods respectively due to extending cultivation activities. On the scarp, dense and open woodlands decreased by 56.2% and 4.6% respectively for 1963-77 while for 1977- 2001 dense woodland decreased by 100% due to firewood collection; open woodland increased by 21.2% through regeneration. Gully erosion expanded by 206% between 1963 and 1977 because of poor land management but decreased by 69% for 1977-2001 through natural recovery and afforestation. Consequently upland vegetation degradation and gully erosion caused soil transfer from the mountains and deposition in the plains. About 0.4% (1977) and 0.6% (2001) of the catchment area under irrigation were abandoned to bushland due to siltation problems. River valleyiii soils in the plains indicated adequate OC (3.4%) due to alluvial deposition thus attracting more agricultural activities. Low OC (0.61-1.09%) indicated low N (0.06- 0.11%) as a limiting factor for paddy rice production in upper areas of the plains. No significant variations (P<0.05) in the stream flows of Chimala River were observed between 1960 and 1993 as a result of upland degradation. It is therefore concluded that upland degradation has contributed significantly to land use changes/degradation occurring in the plains that calls for more efforts to safeguard land resources in the uplands by concerned stakeholders
Soil fertility assessment and microbial enhanced solubility of Minjingu phosphate rock in neutral to slightly alkaline soils of Kongwa district
(Sokoine University of Agriculture, 2023) Nhunda, Daniel Masumbuko
To optimize production of maize and other crops, assessment of soil fertility should be done in agricultural areas from which cite specific fertilizer recommendations will be established. This study was conducted in selected fields of Kongwa district in Dodoma Region to assess the soil fertility status and maximize availability of Phosphate from Minjingu phosphate rock (MPR) for maize production through the use of phosphate solubilizing bacteria (PSB). The specific objectives of the study were to determine the levels of N, P, K, S, Mg, Ca, Na, Zn, Cu, Fe and Mn in soils and evaluate capability of phosphate solubilizing bacteria (PSB) on enhancing P availability from Minjingu Phosphate Rock (MPR) and evaluate field characteristics in slightly acid to neutral soils. Assessment of soil fertility status was done by analysing soils from twenty-four maize growing areas of Kongwa district. Composite soil samples of top soils (0 – 20 cm depth) were collected for physical and chemical analysis. Organic carbon was determined by the Walkley-and Black wet oxidation method (Nelson and Sommers, 1982) and total nitrogen (TN) by the micro-Kjeldahl procedure (Loria et al., 2005). Available P was extracted using Bray-1 and Olsen methods of Bray and Kurtz (1945) and measured by Spectrophotometer following colour developed by molybdenum blue method (Murphy and Riley, 1962). Exchangeable bases were extracted by ammonium acetate saturation method (Thomas, 1986) and cation exchange capacity was determined from NH 4+ saturated soil colloids and displaced using 1 M KCl, then determined by Kjeldahl distillation method for estimation of cation exchange capacity (CEC) of the soil (Robertson and Philip et al., 1999). Extractable sulphur (SO4 2- S) was extracted using calcium monophosphate (Ca(H 2 PO 4 ) 2 .H 2 O), then determined by the turbidimetric method as described by Moberg (2001). The EC for soil samples from Kongwa was measured by using EC meter in a 1:2.5 soil: water (or CaCl 2 for pH only) extract as described by McLean, (1982).Extractable metallic micronutrients e.g., Cu, Fe, Zn and Mn, were extracted by diethylenetriaminepentaacetic acid (DTPA) as described by Lindsay and Norvell (1978). Results indicated that 48% of the sampled fields were sandy clay loam, 26% were sandy loam and the remaining whad a clay or loamy sand textural classes. Soil pH ranged from extremely acid (3.52) to moderately alkaline (7.7), organic carbon ranged from very low to medium (0.19-1.60%) and total N values were very low to low (0.01-015%). Also, results indicated 42% of soils had P deficiency and 16.7% with inadequate S. In addition, 45.8% of the soils had inadequate exchangeable K and exchangeable Mg were very low to high (0.29-4.06cmol (+) kg -1 ). Exchangeable Ca was low to very high (1.06 to 10.04 cmol (+) kg -1 ) with favourable base saturation for crop production. The CEC ranged from very low (2.62cmol (+) kg -1 ) to medium (18.9 cmol (+) kg -1 ). Extractable micronutrients such as Cu, Fe, and Mn were adequate but Zn was inadequate in 58% of the soils. The study area had poor soil fertility is poor with deficiencies in N, P, K, Zn, Mg, and Ca, hence calling for proper management to improve crop production. Phosphorus (P) is one of the major growth-limiting macronutrients required for proper plant growth and it is contained within nucleic acids, enzymes, coenzymes, nucleotides, and phospholipids. One of the ways to replenish P in soils is the use of inorganic fertilizers such as Minjingu Phosphate rock. The challenge is that, phosphate rock (PR) generally requires P-deficient acidic soils with pH of less than 6.2 for P to be released and become available for uptake. Application of PR in neutral to slightly alkaline to soils (pH >6.2) is therefore discouraged since PR solubility is very low in such soils and therefore can not supply sufficient available P to plants. Phosphate solubilizing bacteria have a capability among others, of producing organic acids which in turn lowers the local acidity of the soil in which they operate. The lowering of the pH will/may bring about right conditions for solubility of MPR . Maize trials were established in two villages (Nghumbu and Mlali) of Kongwa District to assess effectiveness of PSB in solubilizing MPR in neutral to slightly alkaline soils and two factors were tested, which are field characteristics (in which treatments were sites), the second factor was PSB co-applied with MPR. Maize trials were established using randomized complete block design (RCBD), the seven sites ,PSB inoculum co-applied with different rates of Minjingu phosphate rock (MPR) (0 – 60 kg ha -1 ). Limiting nutrients such as N and S were corrected then Minjingu RP was applied as basal fertilizer during planting by placing it below the seed and covering with a thin layer of soil followed by a co-culture of PSB inoculant at 5 mL (10 9 bacteria per litre) poured around each plant four days after emergence. Maize plants were harvested at maturity then grain and straw samples were analysed for N, P and K content, phosphorus uptake and phosphorus use efficiency were calculated. Using the soil data, it was found that Nitrogen was the main limiting nutrient in all seven fields. The limiting nutrients in Nghumbi were N and K while N, P, K and Zn were limiting nutrients in Mlali village. In the trial fields, the main effect of fields’ characteristics indicated that the performance of maize and its analyzed parameters (N, P, K, S, Mg, Ca, Na, Zn, Cu, Fe and Mn) were significant (P < 0.001) across the fields reflecting heterogeneity in nutrient levels. There was no significant effect of PSB treatments on maize grain yield and straw yield. Results also did not show significant (P =0.427) interaction effects of field characteristics and treatment combinations on the measured variables in maize because of drought experienced in the study area. The findings of the present study, apart from setting site-specific fertilizer recommendations, also suggest that the performance of maize in the study area depends on the soil nutrient status, especially for native P, N, and K. The studied soils need external nutrient inputs and proper management to optimize crop production and more research is recommended on PSB for more than one season in neutral to slightly alkaline soil before ascertaining the technology to farmers because in this season PSB did not enhance solubility of MPR due to drought experienced in the study area.
The use of coal ash from power plants as a soil conditioner
(University of Nottingham, 2015) Sanga, Hilda Gerald
The disposal of coal ash, produced in large quantities by power plants as a by-product of coal combustion, is a significant environmental concern. Coal ash can be used as an agricultural soil conditioner because of its liming potential and the presence of many essential plant nutrients. However, recommendations for the agricultural use of coal ash should be based on sound knowledge of the coal ash characteristics, particularly the concentrations of potentially toxic elements (PTEs) in the ash. Due to the uptake of PTEs by crop plants it may pose risks to human health following the consumption of food crops. The aim of this study was to evaluate the potential for the safe application of power station derived coal ash to soil as a beneficial disposal route. The specific objectives included; (i) testing the variability of fly ash obtained from different sources in the UK, Czech Republic and Tanzania, (ii) quantifying the short- and long-term changes in soil characteristics induced by applications of ash, (iii) determining the effects of coal ash on soil enzyme activities, (iv) quantifying the utility of coal ash as a fertilizer by evaluating its effect on growth and yield of wheat and (v) assessing risks of long-term use/multiple applications of coal ash to arable soils. Coal ash from the Czech Republic, the UK and Tanzania was characterized; the latter two were used in pot experiments to determine their effects on soil enzyme activities, wheat growth and PTE uptake when added to two contrasting soil types (woodland and arable sandy loams). Two incubation experiments were undertaken to quantify short- and long-term effects of the coal ashes on soil characteristics. Calculations were also performed to evaluate the probable risks of increased contamination of soil and plant material as well as human ingestion of PTEs following repeated applications of fly ash to arable soils. Coal ashes from each source contain varying quantities of essential nutrients and PTEs due to differences in coal ranks and the combustion conditions of the power plants producing each ash. Different batches of ash from the UK and from Tanzania had different characteristics, despite coming from the same industrial source within the respective countries. Application of the first batch of ash collected in the UK (UK1) to woodland soil increased the soil pH, soil respiration and nutritional status during a two-year incubation experiment. Soil amendment with high UK1 ash concentrations (8-16%) contaminated the soil with PTEs through the experiment. In a four-month incubation experiment, the effects of different coal ashes applied to acidic woodland soil varied depending on the characteristics of each individual ash and the amount of ash applied. In a pot experiment designed to evaluate the effect of coal ash on microbial activities, soil amendment with the UK1 ash increased the pH of woodland and arable soils, while application of the TZ1 ash reduced the pH of both soils. Application of low concentrations (0-4%) of UK1 ash to both soils increased dehydrogenase and urease activities and wheat growth while application of TZ1 ash at high concentrations (8-16%) inhibited the enzyme activities. In pot experiments to evaluate the effects of ash on wheat growth, application of 0- 32% of the UK1 ash to woodland and arable soils increased soil pH while application of the TZ1 ash at 0-32% decreased the pH of both soils. Soil amendment with 0-4% of either UK1 or TZ1 ash increased the concentrations and extractability of nutrients and wheat growth and yield, but application of 16-32% of both ashes to both soils contaminated the soils and wheat plants with PTEs. Despite PTE uptake by plants, grain PTE concentrations were within the FAO/WHO 'safe' limits for ingestion, except for As and Cd in grains from plants grown in woodland soil amended with the highest concentrations of UK1 and TZ1 ash respectively, which were both present in higher than acceptable concentrations. Soil and plant concentrations and human consumption of selected PTEs (As, Cd, Cr, Pb and Zn) were calculated following simulated annual applications of TZ1 ash to an arable soil for five consecutive years. This showed that, even when residual contamination over a 25-year period was considered, applications of 2% ash to the soil are unlikely to breach 'permissible' standards for soil, wheat grain contamination and human dietary intake of PTEs, which were far below 'permissible' limits. It would be possible to apply ash with similar characteristics to TZ1 more frequently or over more than five cropping cycles. In conclusion, coal ash can be used as an agricultural soil conditioner; however, low concentrations (0-4%) and the strategic agronomical use of ash, specifically targeting problematic soils, are highly recommended for future studies.
Assessment of the fertility status of soils of rice growing areas of Same District, Kilimanjaro Region, Tanzania.
(Sokoine University of Agriculture, 2003) Amur, Nyambilila
This study was conducted to assess the fertility status of the soils of rice growing areas of Same district. Thirty soil samples were collected from ten different sites where rice is grown. Following laboratory analysis, three bulk soil samples were collected from Kisiwani, Ndungu and Kihurio for pot experiments. The laboratory analysis included determination of total N, organic carbon, P by Bray 1 and Olsen methods, and exchangeable bases by ammonium acetate saturation. The micronutrients were determined by extracting with 0.005M DTPA at pH 7.3. The response of rice (Oryza saliva L) variety super SSD5 to N, P and K, as well as to different levels of Zn were assessed in a glasshouse experiment where plants were grown for 56 days. The harvested plant samples were analysed for N, P, K, Ca, Mg, Zn and Fe using the HNO3-H2O2 wet digestion procedure. The results showed that all the soils in this study were deficient in N. About 53% of the soils had low available P. All the soils had adequate levels of K, Ca, Mg and Na, with the exception of soils from Ndungu, which had a low K, supply. Also, most of the soils had low Zn levels, and only two sites had adequate Zn levels. Soils from Mbugani had low Fe while the rest had adequate Fe and Cu. The glasshouse experiments showed that application of N, P and K increased rice dry matter yields in all the soils used. It was further revealed that Zn supplementation in addition to NPK also increased rice dry matter yields further. The results also indicated that the uptake of each nutrient applied was consistent with the dry matter yields increases. It was concluded that most of the soils under rice cropping in the district were deficient in N, P and Zn and required fertilisation using these nutrients. Iron was also required in Mbugani soils, whichiii were deficient of this element. Field experiments are recommended to confirm these initial findings.
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.
Screening coalmon bean [Phaseolus vulgaris l. savi] genotypes adapted to low soil phosphorus
(Sokoine University of Agriculture, 2006) Mourice, Sixbert Kajumula
Two screen house pot experiments were conducted to identify bean genotypes, diverse in their places of origin and seed size, based on vegetative growth and P uptake and final grain yield for adaptation to low phosphorus. Three phosphorus levels; low P (0 added P), medium P (40 mg P/kg soil) and high P (160 mg P/kg soil) were main plots whereas 27 genotypes were subplots, in a split-plot laid out in a completely randomised design. The test soil was very fine, kaolinitic Kanhaplic I-Iaplustult. Out of 27, seven bean genotypes were further evaluated for yield components and final grain yield at low P in the same soil. Shoot biomass, root biomass, shoot P concentration and P uptake increased with increased P supply and genotypic variability in these parameters was significant (P < 0.05). Genotypes G92, PRETO 143, MILENIO, VEF 88(40), BAT 477, A785, ANT 22, DOR 714 and AFR 708 performed better than other genotypes at low P level; also their response to P addition was significant. It was revealed that P was a major limiting factor to bean growth in the soil used for the experiment. Number of pods/plant increased significantly with increase in P levels and was correlated with grain yield at low P and adequate P. P treatments did not affect the seed size of genotypes. Genotypes BAT 477, MILENIO, DOR 714 and A785 had significantly higher grain yield than other genotypes at low P and may be favoured in the selection process. Although genotypes produced some grain yield at low P, soil fertility improvement by applying medium P or appreciable amounts of organic manure may improve yields and increase productivity per unit area.
Screening coalmon bean (Phaseolus Vulgaris L. Savi) genotypes adapted to low soil phosphorus
(Sokoine University of Agriculture, 2006) Mourice, Sixbert Kajumula
Two screen house pot experiments were conducted to identify bean genotypes, diverse in their places of origin and seed size, based on vegetative growth and P uptake and final grain yield for adaptation to low phosphorus. Three phosphorus levels; low P (0 added P), medium P (40 mg P/kg soil) and high P (160 mg P/kg soil) were main plots whereas 27 genotypes were subplots, in a split-plot laid out in a completely randomised design. The test soil was very fine, kaolinitic Kanhaplic H0aplustult. Out of 27, seven bean genotypes were further evaluated for yield components and final grain yield at low P in the same soil. Shoot biomass, root biomass, shoot P concentration and P uptake increased with increased P supply and genotypic variability in these parameters was significant (P < 0.05). Genotypes G92, PRETO 143, MILENIO, VEF 88(40), BAT 477, A785, ANT 22, DOR 714 and AFR 708 performed better than other genotypes at low P level; also their response to P addition was significant. It was revealed that P was a major limiting factor to bean growth in the soil used for the experiment. Number of pods/plant increased significantly with increase in P levels and was correlated with grain yield at low P and adequate P. P treatments did not affect the seed size of genotypes. Genotypes BAT 477, MILENIO, DOR 714 and A785 had significantly higher grain yield than other genotypes at low P and may be favoured in the selection process. Although genotypes produced some grain yield at low P, soil fertility improvement by applying medium P or appreciable amounts of organic manure may improve yields and increase productivity per unit area.

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