The research experiment was conducted at the Teaching and Research Farm of the Federal University of Technology Akure (7⁰ 16 N, 5⁰ 12 E) located in the rainforest area of southwestern Nigeria. The location is characterized by bimodal pattern of rainfall with an annual mean of about 1300 mm with mean temperature 27⁰C, and the climate is sub-humid type. The total size of the experimental plot was 80 x 40 m, the land is slightly slope with a pH of 6.5, and the land has been under fallow for some years. The textural class of the soil is sandy clay loam with 35.5% clay, 11.3% silt, and 58.2% sand. The fauna observed on the land were termites and different kinds of ants as this was evident due to the presence of termite mound and ant hill in the experimental site. Larger holes made by small mammals (rodents) were also observed in the land. This is an indication that the soil possibly has a good structure and it is well aerated.

The experimental site has over the years been used for cassava production and was left fallowed for about six years with weeds such as Chromolaenaodorata, Euphorbia heterophylla, Panicum maximum, Pennisetum purpureum,Callopogoniummucunoidesand Leucaena leucocephalla - a shrub predominating on the land before the clearing commenced on the land.

(Table 1) shows the pre and post-planting soil physiochemical properties. The pH of the soil at pre-planting was (6.54) rated medium, and post planting ranged from 4.00-4.63 rated very low to low. The pH of the soil before planting differed significantly (P<0.05) from that of post harvest. The total nitrogen at pre-planting (3.2 g/kg) rated as medium and post planting ranged from 4.3-7.1 g/kg which was rated medium to high. The nitrogen concentration as shown by the table also indicated that soil from plantain (sole) and TMS98/0581 (sole) had high N concentration and differ significantly (P<0.05) from other treatments as indicated with the letter (a), while the pre-planting showed the least N concentration. The soil planted to sole crops had higher N concentration than the intercropped plots, and are significantly different (p<0.05). The organic carbon (OC) at pre-planting was (21.0 g/kg) rated low, and post planting ranged from 17.2-24.7 g/kg and was rated very low to low. The soil from plantain (sole) had the highest OC concentration (24.7 g/kg) and it differed significantly (p<0.05) from other treatments, while plantain + TMS98/0581 at 4 weeks had the least OC concentration (17.2 g/kg). The available phosphorus at pre-planting was (5.41 mg/kg) rated low, and at post planting ranged from (9.09-15.76 mg/kg) rated very low to low. The P concentration of soil sample from pre-planting and TME419 (sole) differed significantly (P<0.05) from P concentration of TME419 and TMS98/0581 intercropped at 4 weeks. Potassium at pre-planting was 0.21 cmol/kg rated low, and at post planting ranged from 0.26-0.31 cmol/kg rated low to medium. The result from the table showed that there was no significant difference for K concentration in all the treatments at post planting.

Varietal Response and Effects of Planting Time on Growth Parameters of Cassava

The varietal response and effects of planting time on cassava plant height is presented in Table 2. Plant height increased appreciably and differed significantly (P<0.05) across treatments throughout the experiment. TME419 planted sole had the highest height (190 cm) at 24 weeks after planting and differed significantly (P<0.05) from TME419 intercropped at the same time (167.08 cm) and TME419 intercropped at 4 weeks (129.20 cm) respectively. TMS98/0581 intercropped at 4 weeks had the least height (80.67 cm) at 24 weeks after planting. There were no significant differences (P<0.05) in the number of leaves at 16 weeks after planting as shown in Table 3. TMS98/0581(sole) had the highest number of leaves (76.65) at 24 weeks after planting, while TMS98/0581 intercropped at 4 weeks had the least number of leaves (37.75) at 24 weeks after planting. The data presented in Table 4showed the effect of cassava variety and time of intercropping on stem girth. The stem girth showed no significant difference (P<0.05) at 4 weeks after planting, for all the treatments. TMS98/0581 intercropped at 4 weeks differed significantly (P<0.05) from other treatments from 8 weeks after planting to 20 weeks after planting, but at 24 weeks, there were no significant differences (P<0.05) with TME419 and TMS98/0581 intercropped at the same time, and differed significantly (P<0.05) with TME419 (sole) and TMS98/0581 (sole) which both had the highest stem girth (2.03) at 24 weeks after planting.

The data presented in Table 5 showed the effect of cassava variety and time of planting on plantain leaves. There were no significant differences (P<0.05) across the treatment combinations from 4 to 24 weeks, respectively except for plantain (sole) which differed significantly (P<0.05) from other treatments at 12 weeks after planting. Plantain and TME419 planted at the same time had the highest plant height (118.91cm), while plantain and TME419 intercropped at 4 weeks had the least plant height (112.00 cm) at 24 weeks after planting (Table 6). However, there were no significant differences (P<0.05) in the height of plantain for all the treatment combinations. Table 7 showed an increase in pseudo-stem girth for all treatment combinations at 8 weeks after planting, but there was a decline in the pseudo-stem girth from 12 to 24 weeks after planting across the treatment combinations. There were no significant differences (p<0.05) in the pseudo-stem girth from 4 to 24 weeks after planting.

The data presented in Table 8 shows the yield of cassava varieties in response to their various treatment combinations. Sole planted TME419 had the highest tuber weight (0.81 kg) while TMS98/0581 intercropped at 4 weeks with plantain had the least tuber weight (0.31 kg). TME419 intercropped with plantain at the same time had a higher tuber weight (0.78 kg) compared to TMS98/0581 planted sole (0.71 kg), but they did not show any significant difference. Cassava varieties, TME419 had higher tuber weight in all the treatment combinations compared to TMS98/0581 (Table 8).

Theresults further showed that TME419 and TMS98/0581 planted sole, alongside TME419 and TMS98/0581 intercropped at same time did not differ significantly (P<0.05) in tuber girth, while TME419 and TMS98/0581 intercropped at 4 weeks differed significantly (P<0.05) from those intercropped at the same time as indicated with (letter b) in Table 8). TMS98/0581 intercropped at 4 weeks had the least tuber length (21.33 cm) which is significantly different (P<0.05) from all other treatment combinations, while TME419 (sole) had the highest tuber length (44.25 cm). TMS98/0581 (sole), TME419, TMS98/0581 intercropped at same time and TMS98/0581 intercropped at four weeks had significantly different (p<0.05) tuber length. The variety TMS98/0581 planted sole had the highest number of tubers while TME419 and TMS98/0581 intercropped at four weeks differed significantly (P<0.05) from other treatments. The root yield per plant, and the root yield per hectare of TME419 intercropped at the same time did not differ significantly (P<0.05) from TME419 and TMS98/0581 planted sole, but TMS98/0581 intercropped at the same time was significantly different (P<0.05) from TME419 (sole), TMS98/9581 (sole), and TME419 intercropped at same time. Root yield of TMS98/0581 intercropped at the same time or at four weeks differed significantly (p<0.05) from sole crops. The shoot biomass didnot show any significant difference (P<0.05) in all the treatment combinations, which indicate that the time of planting and the variety may have no effect on the shoot biomass. Dry matter yield obtained after oven drying at 105⁰c for 24 hours showed that TME419 and TMS98/0581 intercropped at 4 weeks had the highest dry matter yield of 30.2% and 29.3%, respectively. This may be as a result of intercropping or may be as a result of the increase in soil acidity which may result in thickening of the plant roots. TME419 had the highest dry matter yield for the sole planted cassava varieties and the intercropped at 0 week after planting and 4 weeks after planting respectively, while TMS98/0581 had lesser dry matter yield compared to TME419 across treatment combinations (Table 8).

The data recorded in Table 9 showed that number of branches for TME419 (sole) and TMS98/0581 (sole) was higher than TME419 and TMS98/0581 intercropped at 0 and 4 weeks after planting. TMS98/0581 had higher number of branches compared to TME419 because it is habitually a branching variety. Height at branching was lower for the branched TME419, this was observed in TME419 (sole) and TME419 intercropped at the same time. They branched at 17.91 cm and 19.1 cm respectively, while TME419 intercropped at 4 weeks did not produce any branch. TMS98/0581 intercropped at 4 weeks branched at 13.83 cm compared to the ones planted at the same time which branched at 33.67 cm, and the sole planted which branched at 58.75 cm.

The results presented in Table 10 showed the yield of plantain at harvest. Plantain (sole) recorded the highest bunch weight (10.53 kg), and differed significantly (P<0.05) from other treatment combinations, meanwhile plantain intercropped with TME419 at the same time had the least bunch weight 7.11 kg. There was no significant difference in the bunch weight of the intercropped treatment combinations. The number of fingers, number of hands, length of fingers and girth of fingers did not differ significantly (P<0.05) across the treatment combinations. TMS98/0581 planted at the same time had the least weight of hand 1.53 kg and differed significantly (P<0.05) from other treatment combinations while TME419 intercropped at the same time had the least weight of finger 0.37 kg and was significantly different (P<0.05) from other treatment combinations.

Plantain and TME419 planted at the same time had the highest LER of 1.48, while plantain and TMS98/0581 intercropped at the same time had an LER of 1.23 (Table 11). Plantain and TME419 intercropped at 4 weeks had an LER of 1.22. Plantain and TMS98/0581 intercropped at 4 weeks had the least LER of 1.11. The treatment combination with the highest ATER was the Plantain + TME419 planted at the same time with 1.5, while plantain + TMS98/0581 intercropped at 4 weeks had the least ATER of 1.14. Plantain + TMS980581 intercropped at the same time had an ATER of 1.17 while plantain + TME419 intercropped at 4 weeks had an ATER of 1.34.

(Table 12) showed the cost of production (input) and the income (output) per hectare for the sole crops and the intercrops. The cost of producing sole cassava was lower at ₦208,000/ha compared to the cost of producing sole plantain which was ₦283,350/ha. The cost of production in the intercrop was higher at ₦345,860/ha because, it required more labour and planting materials compared to the sole crops. From the sole treatments, plantain (sole) had the highest net farm income of ₦581,450/ha compared to TME 419 (sole) which had net farm income of ₦566,500/ha and TMS98/0581 (sole) which had a net farm income of ₦510,500/ha. From the intercropped treatment combinations, plantain + TME419 intercropped at the same time had the highest net farm income of ₦866,440/ha, while plantain + TMS98/0581 intercropped at 4 weeks had the least net farm income of ₦566,140/ha. TMS98/0581 intercropped at the same time had a net farm income of ₦653,840/ha, and TME 419 intercropped at 4 weeks had ₦680,140/ha net farm income. TME419 (sole) had the highest return per ₦1 invested ₦3.567, while plantain + TMS98/0581 had the least return per ₦1 invested ₦2.579. TME419 intercropped at the same time had the highest returns on investment (₦3.416) for the intercrops.

The result of the pre-planting soil analysis carried out on the soils showed that the soil in the experimental site was a sandy clay loam according to soil textural triangle. The low nutrient concentration at pre-planting may be as a result of the opening of the fallowed land which involved uprooting of trees and shrubs, which might have exposed the nutrients to leaching and volatilization. The pH of the soil decreased from the pre-planting pH of 6.54 (slightly acidic) to a pH less than five (< 5) which were 4.62, 4.63, 4.63 (low) for the sole crops and 4.46, 4.47, 4.00, 4.20 (very low) for the intercropped treatment combinations. There was an increase in nutrient concentration when post planting soil analysis was carried out. The increase in nitrogen concentration, organic matter, available phosphorus, calcium, magnesium, potassium, and sodium in the soil may be as a result of the decomposition of the organic materials (leaves from trees, broad leaf weeds, succulent shrubs left in the soil when the land was opened, as well as the protection of the soil from exposure to sunlight and direct impact of rain fall by the cultivated crops.

The effects of the dry spell encountered during the dry season from November 2015 to March 2016 resulted in the decline in pseudo stem girth of the plantain which resulted in the lodging of poorly developed stands, as well as decline in the number of functional leaves to an average of (2.5) leaves per stand, this reduction in the number of leaves may be a kind of survival strategy for the plant 20. The plant increased in height at a very slow rate, and contrary to the complete canopy formation at 5 - 6 months stated by 4, it took 9 months to obtain complete canopy cover. This may be as a result of late planting, and reduced rainfall frequency and quantity in 2015 rainy season.

The time of planting cassava into plantain in an intercrop is very important. The reduced height of the cassava intercropped at 4 weeks was a sign that plantains are quick to establish their roots. This was supported by Lavigne 21 report that the root extension rate is at 2 - 4 cm per day, being 30 % faster during the daylight hours. The cassava intercropped at 4 weeks could not attain a higher height compared to those intercropped at the same time due to competition for soil nutrients and moisture by plantain though they had higher height compared to those intercropped at the same time at 4 weeks after planting but they could not keep up with the competition from 8 to 24 weeks after planting. At 16 weeks after planting, the sole planted cassava and those planted at the same time with plantain experienced a decline in number of leaves, this may be as a result of older leaves shedding in order to reduce the rate of transpiration during the dry spell 20, 22,23.

But the cassava varieties intercropped at 4 weeks did not experience any decline in its number of leaves up to 24 weeks after planting, this might be as a result of the competition they experienced from the day they were planted which resulted in their slow growth. At 24 weeks after planting, the cassava intercropped at 4 weeks showed significantly lesser number of leaves compared to the sole planted and those intercropped at the same time. This is an indication that late intercropping may have effect on cassava number of leaves. The stem girth for TMS98/0581 intercropped at 4 weeks was consistently less compared to other treatment combinations; this may be as a result of competition for light. The yield obtained from the cassava showed that the yield of (TME419) intercropped with plantain at the same time was of no significant difference (P<0.05) with TME419 and TMS98/0581 planted sole in terms of tuber length, tuber girth, tuber weight, root biomass, and shoot biomass. TME419 was significant (P<0.05) in terms of performance compared to TMS98/0581 intercropped regardless of planting time and variety. The TME419 and TMS98/0581 intercropped at 4 weeks, showed a significantly low yield except in the case of tuber weight and shoot biomass for TME419, and shoot biomass for TMS98/0581 which did not differ significantly (P<0.05) from the sole planted and those intercropped at the same time. TMS98/0581 intercropped at the same time had a lesser root yield which was significantly different (P<0.05) from the sole crop, and TME419 planted at the same time. Therefore, with the result of the yield obtained from each cassava treatments, TME419 had the highest yield which may be as a result of its less competition for light due to the plant architecture, which further buttress the point made by Reddy and Willey 24 and Agele et al.15 that plant architecture allows one intercrop to capture sunlight that would not otherwise be available to others. This is important to growth and yield of cereal and legume crops. Agele et al. 15 stated as well that the branching habit of the cassava plant is important to farmers who practice intercropping because it affects both the yield of cassava and the crop grown in association with it. Also the time of planting contributed as well to the higher yield obtained from the intercrop. Intercropping cassava with plantain at the same time gave a higher yield for the two cassava varieties (TME419 and TMS98/0581) used in this experiment, compared to intercropping at 4 weeks. This may be because there was a competition gap for the nutrient requirement stage of the two crops. This may be related to the reports of ^{23, 25} that intercropping system were most rewarding in terms of yield of the component crops when there was a competition gap between the periods the component crops made maximum demand on the micro environment (soil nutrient, moisture, light). The low yield recorded for TME419 and TMS98/0581 intercropped at 4 weeks was confirmed by 26 that cassava planted 3 weeks after groundnut significantly decreased cassava storage root yields as compared to cassava planted at the same time as groundnut in the cassava-groundnut intercrop, probably due to the inter specific competition for growth resources (space, moisture and nutrients) between the two crops. Plantain (sole) had the highest yield while TME 419 intercropped at the same time had the least plantain yield, and the other treatment combinations had lesser yield which differ significantly (P<0.05) from the yield of plantain (sole). This confirmed the report ofwhich demonstrated that intercropping with cassava reduced plantain yield relative to sole crop. The land equivalent ratio for all the treatment combinations were greater than one (>1), plantain + TME419 at same time had the highest LER 1.48, which was an indication that 48% more land would be required to obtain the same yield in sole crops as obtained in intercrop. This might be an indication that the combination will be the most compatible compared to other treatments. Plantain + TMS98/0581 at the same time had an LER 1.23 which was an indication that 23% more land will be required to obtain the same yield in sole crops as obtained in intercrop. Plantain + TME419 had an LER 1.22 which is an indication that 22% more land will be required to obtain same yield in sole crops as obtained in intercrop. Plantain and TMS98/0581 intercropped at 4 weeks had an LER 1.11 which is an indication that 11% more land will be required to obtain same yield in sole crops as obtained in intercrop. The LER obtained implies that there was a yield advantage, this confirms the reports of 15, 20 that when LER is greater than 1 or more, it signals yield advantage and a ratio less than 1, is yield disadvantage. The ATER obtained from all treatment combinations was greater than 1, this may be an indication that the ATER obtained in all the treatment combinations was advantageous in terms of land used and the time for which the intercrop lasted.

The cost benefit analysis revealed that intercropping plantain using TME419 at the same time had more economic advantage compared to plantain sole, TMS98/0581 intercropped at the same time and at 4 weeks had lesser return per ₦1 invested compared to TME419 intercropped at the same time and at 4 weeks. The result further revealed that planting TME419 and TMS98/0581 sole had higher return on investment compared to plantain sole, but in the long run plantain will be most profitable, because there would be little cost on maintenance before the next harvest compared to the initial cost of production.