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Sokoine University of Agriculture Institutional Repository (SUA IR). This repository was built and is maintained by the university library (Sokoine National Agricultural Library-SNAL) , in order to collect, preserve and disseminate scholarly output generated by University research community (staff and students) members.
This repository hosts a variety of openly accessible materials including: scholarly articles and books, theses and dissertations, conference proceedings and technical reports. For assistance about depositing your research output in the repository click here. SUA IR Policy click here or any queries contact us at snal@sua.ac.tz.
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Recent Submissions
Effectiveness of Fanya Chini terraces on soil properties and crop yield in the north-wester!' part of the Uluguru mountains, Morogoro, Tanzania.
(Sokoine University of Agriculture, 2001) Mkoba, Appia Paul
A field experiment was conducted in the north-western part of the Uluguru
Mountains, Morogoro District, to determine the effect of Fanya chini terraces on
selected soil chemical and physical properties and crop performance. Eighteen
experimental plots of 12 m x 3 m were established on farmers' fields. Plots with
Fanya chini terraces were compared with those with no conservation structures.
Maize (Zea mays L.) was used as the test crop. No inorganic fertiliser was applied in
order to reflect farmers’ practices in the area. Soil samples from the experimental
plots taken at the beginning (initial) and at the end (final) of the study were analysed
to assess the changes in soil physical and chemical characteristics that had occurred
during the cropping period.
Most of the observed soil chemical variables were slightly (but insignificantly) higher
in plots that had no conservation structures (unconserved plots) and their magnitude
tended to increase along the slope. Organic carbon, total nitrogen and exchangeable
calcium showed a significant increase (P = 0.05) in unconserved plots in the final soil
samples. There was a significant difference (P = 0.01) in PR between the Fanya chini
terraced plots and unconserved plots both at the beginning and at the end of the
experiment. Fanya chini terraced plots had mean PR value of 0.69 and 1.81 MPa
compared to unconserved plots which had mean PR values of 0.78 and 1.71 MPa at
the beginning and at the end of the experiment, respectively. Maize grain yield and
biomass were not significantly different between the Fanya chini terraced and
unconserved plots. However, grain yield and biomass were relatively higher in the
unconserved plots and they tended to increase along the slope. The exposure and
spread of the subsoil from the Fanya chini channels that were about 30 to 50 cm deep may have resulted into the reduced soil fertility and the resultant lower yield observed under Fanya chini terraces. Fanya chini terraces are not the best soil conservation measure on steep slopes. Where they are already in place, Fanya chini terraces should be complemented with other soil surface management practices.
Irrigation scheduling based on penetrometer depth technique.
(Sokoine University of Agriculture, 2001) Moses, Chibuye Mambwe
Efficient and profitable irrigation scheduling strategies are needed particularly in the arid and semi arid regions where available water resources are becoming more limited due to population growth and/or climate. Salinisation of ground water resources due to inappropriate water use is equally threatening large areas of productive irrigated land. To help sharpen the predictive capability of farmers with regard to soil water status, a study to model a simplified approach to irrigation
scheduling based on soil resistance to penetration was undertaken at Sokoine University of Agriculture in Tanzania. Two locations representing two different soil types namely clay soil (SI) and sandy clay loam soil (S2) were used. Each location comprised of three blocks which were further subdivided into three plots. Three irrigation timing schedules were allocated to the plots in a Complete Randomised Block Design. Penetration depth at randomly selected spots was measured before and after irrigation for all the plots. The gravimetric determination of soil moisture content for each of the four penetrometer legs up to the penetration depth was done.Thereafter, two of the plants around the penetrometer were randomly selected, dug out and their tap length measured. The corresponding soil moisture content for the root length starting from average penetration depth to the entire extent of the root was then determined. The results showed that penetration depth is linearly related (r = 0.91 for SI and r = 0.82 for S2) to soil moisture content within the zone of penetration. Beyond average penetration depth, the soil moisture content for SI correlated poorly (r = 0.32) with average penetration depth while S2 correlated relatively high (r = 0.78). However, the multi variable model (i.e. root length and average penetration depth as variables) showed improved and highly positive correlation coefficients (r = 0.94 for SI and r = 0.96 for S2) with root zone moisture content beyond the penetration depth. Calibration of an individual soil type would make possible the relationship to be developed between penetration depth and depth of irrigation application otherwise the models would simulate soil moisture content.Model validation by using the t-test showed no significant difference (p < 0.05) between observed and simulated values for all the three models developed. The observed and simulated moisture contents of both models 2 and 3 in each of S1 and S2 were compared by using the t-test. The results showed no significant difference (p<0.05) although the mean simulated root zone moisture content of model 2 was closer to the mean observed root zone moisture content than the mean simulated value of model 3 for both locations. The results have shown that the penetrometer depth approach can be used to indicate soil moisture status and/depth of irrigation application in the upper soil of 0 - 30 cm which is used by farmers as an indicator of the soil water status and hence influences irrigation scheduling decisions.
Assessment of soil fertility status of three soils after four years of continuous application of different nutrients
(Sokoine University of Agriculture, 2004) Mbanzibwa,Deusdedith
A study was undertaken to assess the fertility status of three soils following four years of continual application of different nutrients. The three soils were from Mlingano, Nkundi and Sasanda, which are classified as Rhodic Kandiustox, Acruoxic Kandiustult and Dystrict Haplustand, respectively. The study was conducted under both field and glasshouse conditions. For the pot experiment conducted at the SUA glasshouse all three soils were used whereas field experiment was conducted only at Nkundi site. Soils for pot experiment were taken from absolute control plots and from plots treated with TSP and MPR at the rate of 120 kg P/ha. Under field study one more treatment, namely control for P was included. The results showed that application of different nutrients, except nitrogen, led to build up in levels of applied nutrients. Application of MPR or TSP increased levels of Bray 1-P from low to medium and high levels, respectively, in Nkundi and Mlingano soils. In Sasanda soil, Bray 1-P remained below 5 mg P/kg despite application of TSP and MPR. This was attributed to high P fixation capacity of Sasanda soil. In Nkundi soil, MPR application raised Bray 1-P from 5.0 mg P/kg to 41.7 mg P/kg whereas in Mlingano soil Bray 1-P was raised from 2.6 mg P/kg to 39.4 mg P/kg. Application of TSP raised Bray 1-P to above 105 mg P/kg in Mlingano and Nkundi soils but only to 4.7 mg P/kg in Sasanda soil.
Zinc and copper increased to sufficient levels in all soils due to application of zinc sulphate and copper sulphate fertilizers. Use of TSP or MPR decreased soil pH in Mlingano and Nkundi soils but the decrease was less in soil treated with MPR. For instance in Mlingano soil, pH decreased from 5.5 to 5.4 and 5.0 for soils treated with MPR and TSP, respectively. However in Sasanda soil MPR increased soil pH from 5.0 to 5.3 and there occurred no shift in pH in plots treated with TSP. Residual P increased significantly (P = 0.05) the maize dry matter and grain yields in plots treated with TSP and MPR. The increase in dry matter and grain yields due to residual P from MPR and TSP were comparable. In Mlingano and Nkundi soils, diy matter yields ranged between 7.29 and 64.77 g/pot whereas in Sasanda soil it ranged between 2.12 and 22.10 g/pot. At Nkundi site, residual P from MPR and TSP gave yields of 4.23 and 4.73 t ha'1,respectively. Yield in absolute control and control for P treatments were 1.03 and 1.83 t ha'’, respectively. It was concluded that residual P from MPR and TSP had comparable effects on maize production.
Evaluation of sprinkler irrigation performance at Simunye Sugar Estate in Swaziland.
(Sokoine University of Agriculture, 1995) Magongo,Bongani Harmon
The performance the evaluated study irrigation system at Simunye,objectiveswere:parameters,(1)To identify the original parameters,(2)To investigate performance parameters,whether the system is operating as designed,and (3)To recommend suitable changes in the operation and system configurations that could be implemented to improve the irrigation efficiency.
The results showed that there were no available design parameters on which the system of Simunye Sugar Estate was designed. The system showed a uniformity coefficient (Cu)of 76%,which is within recommended Cu range for design market acceptance.The Distribution uniformity obtained was 61% and the potential application efficiency for the low-quarter (PELQ) was found to be 54%.Both of these parameters were lower than the recommended ones, and they were significantly different when compared with the recommended ones of at least 67% and 75-85%, respectively.The actual application efficiency for the lower-quarter (AELQ) was found to be 45% which is too low when compared to the PELQ.The minimum basic infiltration rate of the soils irrigated by sprinkler system was 5 mm/h. Factors which contributed to the non-uniformity of the system were wind velocity and wind the direction operating pressure (which was too high or lower than the recommended one for the system), evaporation losses,and the sprinkler spacing. From the results it was shown that management of the irrigation system had an effect on the poor performance of the system.
Effects of Mswiswi watershed degradation on stream flow in Usangu village irrigation project
(Sokoine University of Agriculture, 1997) Malongo,Gerald Wanda Sere
The effect of Mswiswi watershed degradation on stream flow was investigated as one of 5 watersheds used by Usangu Irrigation Project as source of water. The watershed was calibrated upon itself by establishing four watershed degradation scenarios as the basis for comparison of watershed degradation parameters and stream flow characteristics. The established degradation scenario were 1960-65, 1965-75, 1975- 86 and 1986-92. The 1960-65 degradation scenario was taken as the control period i.e the period for which watershed degradation was at the minimum level. Therefore all parameters of watershed degradation and stream flow of certain probabilities in
1960-65 were compared with the same parameters in other three scenarios.Watershed degradation evidence analyzed from aerial photographs of 1977 and 1992 shows that: watershed forest loss was 0.105 , 0.032 and 0.497 km2/year for mixed forest,forest reserve and low dense miombo woodland, respectively. Soil degradation through gully expansion was 0.049 km2/year.The study shows that precipitation in Mswiswi watershed is decreasing from 1963-1986. This has been evidenced by decreasing trend of 5-year moving averages of precipitation and precipitation of certain probabilities. Comparison of watershed degradation parameters in four degradation scenarios shows that there were a differences among scenarios as a result of degradation. There was a general decreasing trend of parameters such as watershed storage and watershed loss factor from degradation scenario of lower order (1960-65) to scenario of higher order (1986-92). This means that the trend of decrease in watershed degradation parameters was from 1963-1989. Watershed degradation parameters such as curve number and watershed degradation factor were, on the contrary, increasing from 1963-1989. The decrease of watershed loss and watershed storage indicate that watershed was degrading as has been evidenced by watershed forest loss. Similar indication of watershed degradation was shown by increase of curve number and watershed degradation factor.
This study shows that there was a relationship between increasing trend of runoff and increasing or decreasing trend of watershed degradation parameter from one degradation scenario to another for a particular probability of exceedance. Runoff of 10 % probability was increasing from watershed degradation scenario of lower order to scenario of higher order as watershed storage and loss factor of the same probability was decreasing. The trend of changes in base flow of particular probability of exceedance was more related to the trend in which watershed degradation factor of the same probability was varying. Stream flow from Mswiswi watershed is affected by both climatic changes and watershed degradation. To evaluate the effect of watershed degradation alone, the developed runoff and base flow models were run for equal rainfall events, so as to see how the watershed in the process of degradation in different periods was responding or would respond to the same rainfall events. The results of model utilization show that runoff was increasing as the watershed was degrading for equal rainfall events. In the case of base flow, the results of model utilization show that watershed degradation was causing cyclic trends of base flow variability. The maximum and minimum base flow for equal rainfall were having recurrence intervals of ten years. The magnitude of maximum and minimum base flow was decreasing with time as watershed was degrading for equal rainfall events.