Melkassa Agricultural Research Center Research Articles

Effects of Gibberellic acid and 2,4-Dichlorophenoxy Acetic Acid Spray on Vegetative Growth, Fruit Anatomy and Seed Setting of Tomato (<i>Lycopersicon esculentum Mill.</i>)

The experiment was conducted at Melkassa Agricultural Research Center, Ethiopia with the objective to evaluate the effects of different concentrations and combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) and gibberellic acid (GA3) spray on vegetative and reproductive growth components of tomato. The experiment consists of two tomato varieties, one processing (Roma VF) and one fresh market (Fetan), three levels of 2,4-D (0, 5 and 10 ppm) and four levels of GA3 (0, 10, 15 and 20 ppm) arranged in 2x3x4 factorial combinations, in Randomized Completed Block design with three replications. Data were collected on qualitative parameters (vegetative, reproductive growth and external fruit color) through visual observation, and quantitative parameters (seed number per fruit, seed weight per fruit, fruit shape index and average fruit weight). Qualitative data were analyzed using analysis of variance (ANOVA) by SAS (2002) software and mean separation was carried out by DMRT at 5% probability level. The result indicated that tomato plant treated with 2,4-D intended to have increased stem thickness, decreased leaf size induced epinastic and flower bud abscission in both cultivars while GA3 treatment has no retarded growth and flower bud abscission. Application of 2,4-D has responsible in the development of seedless parthenocarpic fruit with increased size but with unfilled cavities especially at higher concentration. On the other hand, GA3 at lower concentration results in normal fruit and seed development but as its concentration increases it results in the development of more proportion of smaller fruits per plant and formation of blotchy ripening on the fruit. Combined application of the two PGRs at lowers concentrations seems to result in the intermediate effects of both PGRs in single application. In general, concentration of the PGRs used and genetic background of the variety determine the response of tomato growth, fruit setting, seed formation and final marketable fruit size.

Determination of Water Requirement and Crop Coefficient for Sorghum (<i>Sorghum bicolor L</i>.) at Melkassa, Ethiopia

Knowledge of crop evapotranspiration (ETc), the combined process of evaporation and plant transpiration, is important in agriculture for scheduling farm operations and designing and managing irrigation and drainage systems. Development of crop coefficient (Kc) can enhance crop evapotranspiration (ETc) estimates in specific crop growth stages. However, locally determined Kc information is not available for many important crops in Ethiopia. This research was, therefore, conducted to determine growth stage specific Kc and crop water use for sorghum (Sorghum bicolor L.) var. Gambella-1107 at the Melkassa Agricultural Research Center which is located in a semi arid climate zone in Ethiopia. Drainage type lysimeter was used to measure Gambella-1107 crop water use under water balance system on a clay loam soil and local weather data were used to determine the reference evapotranspiration (ETo). Crop coefficient was developed from measured ETc and ETo calculated using weather data. The growth stages of the crop were assessed as the seasonal change of plant height (pH), leaf area (LA) and leaf area index (LAI). The yield obtained was 5.3 t ha-1 and the measured LAI were 0.2, 4.2, 4.9 and 1.6 at the initial, development, midseason and late season stages, respectively. The maximum LAI was achieved when the plants reach their maximum height at mid-season stage with high crop evapotranspiration due to leaf enlargement that increases transpiration. The measured ETc values were 53.8, 138.5, 214.4, and 94.0 mm during the initial, development, midseason and late-season stages, respectively, and the seasonal total value was 500.7 mm. The calculated Kc values for the crop were 0.45, 0.83, 1.18 and 0.78 during the initial, development, mid-season and late-season stages, respectively. These values were greater than those reported in FAO publication for sorghum varieties which could be a result of soil, climate and crop genetic differences. This suggests the need for developing site-specific Kc values for proper irrigation management.

Crop Water Productivity of Irrigated Teff in a Water Stressed Region

In water stressed regions such as the Central Rift Valley of Ethiopia, increasing Crop Water Productivity (CWP) is imperative for sustainable food and water security. This paper presents CWP of Teff (Eragrostic Tef), a staple food in Ethiopia and an important export crop. Field experiments were conducted under irrigated agriculture during the dry seasons in the periods: 1) November 2010 to March 2011; and 2) December 2011 to April, 2012 at Melkassa Agricultural Research Centre in Ethiopia. Teff crop was irrigated at sixteen different water application depths ranging from 100 to 25 % of the optimum Crop Water Evapotranspiration (ETc.) during the four growing stages, the initial, development, mid season and late season. The effect of seeding rates of 25 kg/ha and 10 kg/ha on lodging and yield of the crop was also determined. The main results were: 1) At 25 % deficit irrigation applied for the whole growth period, Teff CWP was the highest at 1.16 and 1.08 kg/m3 respectively for the seeding rates of 25 kg/ha and 10 kg/ha; 2) the CWP slightly decreased to 1.12 and 1.07 kg/m3 when the 25 % deficit was applied during the late season stage; 3) the crop yield response factor (Ky) of 1.09 and 1.19 was obtained for seeding rates of 25 kg/ha and 10 kg/ha respectively; the equivalent biomass response factor (Ky) was less at 0.88 and 0.96 respectively.

Advanced evaluation of cowpea (Vigna unguiculata ) accessions for fodder production in the central rift valley of Ethiopia

The experiment was conducted at Adami Tulu Research Center in 2004 with 37 selected lines of grain type cowpea (Vignia species) germ-plasm introduced from Melkassa Agricultural Research Center, Lowland Pulse Improvement Program for the advanced nursery trial. Dolichos lablab (Lablab purpureius both var. Highworth and Rongai) and cowpea (Vignia ungiculata var. white worder training type) were included as a control for herbage yield and quality evaluation and ranking. The top ten accessions of cowpea (IT82D 889, TUX 1948-01F, TVU 1142 4, IT85F 2687, 82D 504-4, IT84D-448, IT93K2046-2, IT87D 551-1, IITAUK91-12, 87D -1802,) and Dolichos lablab var. Rongai was selected using the visual observation data taken during the 2004 growing season and promoted for further advanced evaluation. Advanced evaluation was carried out during the growth period, 2005 and 2006, using randomized complete block design (RCBD) of three replication of plot size 3 × 2 m. Fresh weight yield, hay yield, grain yield of both years showed statistically significant difference among accessions (p<0.005) during both growing periods. There was statistically significant difference in percentage dry matter (DM%), percentage organic matter (OM%), percentage ash (ASH%) and percentage crude protein (CP%) (P<0.0001) and the highest value of 88.94, 79.32, 12.09 and 22.3% were shown by accessions IITAUK91-12, IT87D 551-1, 87D -1802 and IT93K 2046-2, respectively. The different accessions responded to the different seasons differently based on the rainfall duration in their herbage and grain yield that needs further categorization. Key words: Adami Tulu, Dolichos lablab, herbage var. Rongai yield.

Effects of Gibberellic acid and 2,4-dichloro-phenoxyacetic acid spray on fruit yield and quality of tomato (Lycopersicon esculentum Mill.)

Experiment was conducted at Melkassa Agricultural Research Center, centeral rift valley of Ethiopia from September 2008 to January 2009 with the objective to determine the effects of different concentrations and combinations of 2,4-dichlorophenoxyacetic acid (2,4-D) and gibberellic acid (GA3) spray on fruit yield and quality of tomato. The experiment consisted of two tomato varieties-one processing (Roma VF) and one fresh market (Fetan), three levels of 2,4-dichlorophenoxyacetic acid (2,4-D) (0, 5 and 10 mg l-1) and four levels of gibberellic acid (GA3) (0, 10, 15 and 20 mg l-1) arranged in 2 × 3 × 4 factorial combinations, in Randomized Completed Block Design with three replications. The result showed that increased in fruit length from 5.44 to 6.72 cm at 10 mg l-12,4-D combined with 10 mg l-1 GA3 above the control. Increased fruit weight by 13% due to 2,4-D and reduced fruit weight in single or combined application of GA3 with 2,4-D. Fruit pericarp thickness was increased by about 50% due to 2,4-D and GA3 application above the control. Titratable acidity, total soluble solids and lycopene content were also increased due to combined application of 2,4-D and GA3 spray. Lower fruit pH is another quality attributes of tomato affected by 2,4-D application while that of GA3 has no effect. Final fruit yield were significantly improved above the control even though both varieties responded deffirently. For Roma VF, GA3 at concentration of 10 and 15 mg l-1 resulted in maximum fruit yield of 69.50 and 67.92 ton ha-1, respectively in the absence of 2,4-D. For Fetan, maximum marketable fruit yield of 74.39 and 74.20 ton ha-1 was obtained from treatment combinations of 10 + 15 and 5 + 0 2,4-D and GA3, respectively. Hence, yield increment of about 35% for Roma VF and 18% for Fetan were produced at 10 mg l-1 GA3 and 10 + 15 mg l-1 2,4-D and GA3, respectively over the control. Significant increase in fruit size and weight due to 2,4-D and increased fruit number due to GA3 spray contributed to increased fruit yield. The results indicated that both PGRs are important in tomato production to boost yield and improve fruit quality under unfavorable climatic conditions of high temperature. Therefore, it is important to further investigate application methods and concentrations of the PGRs under concern in different growing conditions on different tomato cultivars. Key words: Gibberellic acid, 2,4-dichlorophenoxy acetic acid, tomato,Lycopersicon esculentum Mill, fruit yield, quality.

Fruit yield and quality of drip-irrigated tomato under deficit irrigation

The competition for limited amount of world fresh water is increasing at a fast rate. The agricultural sector is the major water user and also the most inefficient. As a result, the economic return from a unit of water is the lowest for agricultural sector. Therefore, in the wake of dwindling water availability, it is becoming imperative to look for ways of maximizing yield and quality of produce per unit of water. This is especially important in countries like Ethiopia, where there is severe water shortage in the arid and semi-arid areas. In this study, a field experiment was conducted at Melkassa Agricultural Research Center, Ethiopia to study the effects of moisture stress on the yield and quality of two tomato cultivars; Melka Shola and Melkassa Marglobe used as salad. The two tomato cultivars were exposed to four irrigation water deficit levels expressed as percentages of potential evapotranspiration (ETc) as: 0%ETc, 25%ETc, 50%ETc, and 75%ETc deficit. The total plant biomass decreased with stress level while the fruit dry matter increased. As a result, the harvest index (fruit dry matter weight/plant dry matter weight) was increased with stress level. At a given stress level, the harvest index of Melka Shola was higher than that of Melkassa Marglobe. Both the number and size of tomato fruits were found to decrease with moisture stress. The incidence of sun-scald and blossom end rot was higher in the more stressed plants (75%ETc) deficit. The total soluble solid (TSS) content was significantly affected by irrigation treatments. The total soluble content was increased with stress level while the fruit water content was decreased. The fruit total soluble content (TSS) of the stressed plants was also significantly different between the tomato cultivars. Melkassa Marglobe cultivar had higher total soluble solute content than Melka Shola cultivar. The higher total soluble solute content of Melkassa Marglobe might be the reason why this cultivar is preferred by consumers for use as a salad. It has been observed also that small animals and birds fed more on this cultivar than on the Melka Shola cultivar.

Comparative Studies of the Influence of Relative Humidity and Temperature on the Longevity and Fecundity of the Parasitoid,Cotesia flavipes

The parasitoid, Cotesia flavipes (Cameron) (Hymenoptera: Braconidae), was introduced for biological control of the stemborer, Chilo partellus (Swinhoe) (Lepidoptera: Crambidae), in eastern and southern African countries. The parasitoid became firmly established in Ethiopia, with varying density and distribution in various regions of the country indicating that there are factors regulating the success of the parasitoid. From previous studies, it was known that the population of the parasitoid released, the type of host, and temperature highly affect some of the biological parameters of the parasitoid. The current studies were undertaken to understand the individual and interactive effect of temperature and relative humidity on the longevity and fecundity of C. flavipes. The study was conducted on C. flavipes collected from the Melkassa Agricultural Research Center Experimental Field, Ethiopia. C. flavipes was reared in the laboratory on C. partellus feeding on pieces of sorghum stem. The longevity experiment was conducted at 10, 20, 30 and 40 °C, while the fecundity experiment was conducted at 20, 25, 28 and 30 °C. For both experiments 40–50%, 60–70% and 80–90% relative humidity regimes were used. The results obtained indicate that the interactive effect of temperature and relative humidity significantly affected the longevity, the number of oocytes, and fecundity of C. flavipes implying that the two factors play an important role in the success of the parasitoid as a biocontrol agent against C. partellus. The results obtained suggests the importance of the selection of target release sites for maximum efficiency of the parasitoid, which can have a positive impact on the on-going augmentative release of C. flavipes in Ethiopia.