Sugarcane (Saccharum spp.) is an important economic crop in the tropics and sub-tropics due to its high sucrose content and bioenergy potential. Sugarcane in Ethiopia so far the industry does not have its own breeding program it has always been dependent on importing sugarcane varieties and locally evaluating their performance on yield and diseases.

According to Sundara (2000), in order to enhance productivity and profitability of commercial scale sugarcane cultivation, adoption of high yielding varieties and improved production packages are highly demanding. There are number of reasons for lower cane yield and one of those is the planting of low yielding varieties. Therefore, it is  need  of  the  time  to  introduce new high yielding varieties with good ratoon ability in the country (Chattha and Ehsanullah, 2003). Variety plays a key role in both increasing and decreasing per unit area sugar yield, while use of unapproved, inferior quality cane varieties affect sugarcane production negatively as situation prevails today (Mian, 2006). The solution of low cane yield and sugar recovery problem lies in the planting of improved cane varieties (Chattha et al., 2006). Varieties differ not only in their yield of cane but also in their juice quality. They also differ in the length of time required to reach maturity. There are also very marked responses to the environment, and even different ecological zones within a country. It is for this reason that, if the best selection is to be made, the final stages in a varietal selection program must incorporate trials in a country that must be representative of all the main ecological zones (James, 2004). Important considerations in choosing an appropriate variety are: cane yield, juice quality, age group, suitability to the growing condition (that is, soil type, irrigation level, season etc.), ratooning potential, and resistance to disease and pest and adverse growing condition (Sundara, 2000).

Efforts are being made to increase cane production by introducing high yielding varieties and adoption of improved crop production techniques (Gill, 1999). Success of variety depends upon its adaptability to agro-climatic conditions of the area. Selection of a proper variety to be sown in a particular agro-ecological zone is a primary requisite to explore its yield and sugar recovery potential. Ratoons are important for overall profitability of sugarcane cultivation as they save about 30% in the operational cost, mainly that of seed and reduced expenses for soil management (Sundara et al., 1992). The inherent potential of a variety to give better yields in plant and ratoon crops is of paramount importance for sustaining high productivity. Acceptance of a variety by the farmers now depends very much on its ratooning potential. Thus, sugarcane varieties, which show good performance in plant and ratoon crops, should be promoted for commercial cultivation. In Ethiopia, even if the country has a fertile soil and favorable environmental condition for sugarcane production its average cane yield is limited to about 104 ton/ha/year (Sugar Corporation, 2011) this could be attributed by many factors, of which lack of improved varieties play central role. For this purpose, the variety improvement strategy should guarantee proper substitution of declining or poor performing commercial varieties from its sugarcane germplasm pool following proper field evaluation. Therefore, the government has developed a strategy to import divers improved sugarcane varieties from around similar ecological locations of the glob to secure the upcoming huge development and expansion in sugar industry.

Accordingly, 10 promising sugarcane varieties from the introduced materials,  were  promoted  and  tested  under two soil types of Finchaa agro-ecological condition to identify elite candidate for pre-commercial release. Therefore, the present study was conducted to identify better performer variety/varieties in sugar yield under Finchaa agro-ecological condition. 

Description of the study area

The study was conducted at Fincha’a Sugar Estate during 2003/4 to 2008/9 cropping season. The area is found 330 km west of Addis Ababa, and is located at 9° 31’ to 10° N latitudes and 37° 15’ to 37° 30’ E longitude with an elevation between 1350 and 1650 m a.s.l. The area characterized by average annual rainfall of 1280 mm with a mean minimum and maximum temperature of 14.5°C and 30.6°C, respectively. Moisture demand of the crop is supplemented by sprinkler irrigation.

Experimental design and treatments

The study comprised, eleven test varieties that were promoted from disease evaluation trial and a check variety with better adaptation were considered: B58 230, N53 216, N52 219, M202 46, CP47 193, DB386 60, B59 250, COK 30, B60 163, CO 1148, BO 60349 and NCO334 (Check variety).

All the varieties considered in this study were newly introduction to Finchaa Sugar Estate and were selected based on their performance on variety adaptability trials conducted at Wonji - Shoa and/or Metahara Sugar Estates (Aregaw, 1997, 2000). The evaluation was made based on plant cane and two ratoon crops on the two major soil types of Finchaa (Vertisol and Luvisol). The experiment was laid out in a Randomized Complete Block Design with three replications. Each experimental plot had a size of 29.0 m² (four furrows of 5 m length and 1.45 m space between furrows). For data collection and observation, only the two middle rows were considered. The distance between plots and within replication was 1.5 and 2.9 m, respectively.

Parameters collected and data analysis

During the course of the experiment sprout percent, tiller count, number of millable canes and growth (height) measurement were taken. Moreover cane yield, cane thickness (girth), number of internodes, percent sucrose and estimated sugar yield were measured at harvest by taking 10 random samples from each plot. Except for the varieties used as treatments in this trial other inputs and field operations on the site were made following conventional practices of the Estate. 

Finally, data were subjected to General Linear Models Procedure (GLM) using SAS software statistical package (SAS, 2002) following a procedure appropriate to the design of the experiment (Gomez and Gomez, 1984). The treatment means that were significantly different at 5% levels of significance were separated using the Duncan Multiple Rang Test (DMRT). 

Sprouting, tillers and millable canes

Combined analysis of the data on plant cane, 1^st  and  2^nd  ratoon; except tillers of 1^st ratoon revealed no interaction between varieties and soil types on percent sprouting, number of tillers and number of millable canes (Appendix Tables 1). Whereas, sugarcane varieties were significantly different from each other on percent sprouting, number of tillers and number of millable canes in all the three cuttings (Tables 1, 2 and 4).

Regarding cane thickness, significantly thicker cane was obtained from variety M202 46, of all the cuttings (PC, 1^st and 2^nd ratoon) followed by B60 163, BO60 349, and B58 230.  Taller plants were produced by variety CO 1148 in all the three cuttings followed by variety COK 30. The plant height and cane girth are the major contributing factors for high cane yield (Rehman et al., 1992). Similarly, in this work, the variety M202 46 and CO 1148, which recorded the highest in cane girth and plant height, respectively were grouped in the first category for cane yield ha^-1 month^-1 (Table 1).

Sucrose content, cane yield, and sugar yield

Combined analysis of variance of the data on cane yield, sucrose content and sugar yield revealed that there is an interaction effect of variety and soil on sucrose content and sugar yield for 1^st ratoon crop and sucrose content for 2^nd ratoon crop, while no interaction in plant cane, cane yield in 1^st ratoon and cane yield and sugar yield in 2^nd ratoon (Appendix Table 1).

In plant cane, when both soil types were combined, variety  N53 216 was rich in sucrose (13.79%) than other varieties followed by DB386 60 (12.63%), in addition except few varieties like B59 250 (7.13%), M202 46 (10.09%) and CO1148 (10.53%) the rest were better in sucrose content than the check variety NCO 334 (11.60%).

In 1^st and 2^nd ratoon, B59 250 was the least  in  sucrose content for both soil types, while M202 46 did so in Vertisol only (Tables 2 and 4). Variety N53 216 is also significantly superior in sucrose content than the check variety in Vertisol of 1^st and 2^nd ratoon (Tables 3 and 5).

Except lower values of DB386 60, B59 250 and B60 163 for plant cane, B59 250 for 1^st ratoon and M202 46 and 386 60 for 2^nd ratoon, the total tonnage of the cane per hectare per month of sugarcane varieties were not significantly different from the check variety NCO 334 (Table 1, 2 and 4). Variety N53 216 and B58 230 got the highest ton per hectare per month cane yield consistently over the three cuttings (Table 1, 2 and 4). Same wise when data for both soil types were combined, variety N53 216 outperformed the existing commercial sugarcane varieties in sugar yield (1.48, 1.91, and 1.50 t ha^-1 month^-1 for plant cane, 1^st ratoon and 2^nd ratoon respectively) (TableS 1, 2 and 4). Except DB386 60, B59 250 and B60 163 for plant cane, N53 216 (significantly higher than the check), B59 250 and M202 46 for 1^st ratoon and M202 46, DB386 60, B59 250 and B60 163 for 2^nd ratoon, the total tonnage of sugar yield per hectare per month of sugarcane varieties were not significantly different from the check variety NCO 334. Variety B59 250 produced the least sugar yield compared to any other variety in all the three cuttings (Table 1, 2 and 4).

Generally, the mean values of cane and sugar yield of the three cuttings indicated that, among the evaluated eleven sugarcane varieties N53 216 and B58 230 were the best performing varieties in both soil types viz. luvisol and vertisol. Beside, BO-60349 and B60/163 were also out standing sugarcane varieties in sugar yield on luvisol and vertisol, respectively (Table 6). On Luvisol, variety N53 216, BO 60349 and B58 230 gave a sugar yield advantage of 25.7, 5.4 and 4.9% over  the  check  variety NCo 334, respectively. On the other hand, variety N53 216, B60 163 and B58 230 gave a sugar yield advantage of 27.9, 2.1 and 1.5% over the check variety NCo 334 on Vertisol. According to Worku and Chinawong (2006) different performances of the same variety on distinct two soil types might have been attributed to the differential response potential to the environment in which it was grown. In agreement with this result, Dillewijn (1952) and Kakde (1985) reported that the differences in the ability of a variety to extract nutrients from different soil types affected its potential to grow under a given soil condition. Better performance of some varieties on both soil types could perhaps indicate their wide adaptation to different soil types.

The authors have not declared any conflict of interests.