YIELD OF CASSAVA (Manihot esculenta Crantz) VARIETIES AS INFLUENCED BY NPK APPLICATION AND STEM PROPERTIES IN TWO AGRO-ECOLOGIES OF NIGERIA

Abstract

Cassava is a major staple and commercial crop in the tropics, its yield is constrained by factors such as decline in soil fertility and use of inappropriate planting materials. Fertiliser application and use of appropriate planting materials could improve yield of suitable cassava varieties. However, there is dearth in knowledge on appropriate fertiliser formulations, application rate and qualities of stem cuttings for improved cassava varieties. Therefore, effects of different fertiliser formulations, application rates and stem portions and lengths of stem cuttings on cassava yield were evaluated in two agroecologies of Nigeria. Experiments were conducted at Ikenne (Rain-Forest), Ibadan and Tsonga (DerivedSavanna). Four cassava varieties: TMEB419-(V1), IBA010040-(V2), IBA011412-(V3) and IBA070593-(V4) were planted and four fertiliser formulations [NPK15:15:15-(F1), TSP+KCl-(F2), urea+KCl-(F3) and urea+TSP-(F4)] were applied, so as to supply 0, 45- (R45) or 75-(R75) kg N, P2O5 and K2O/ha. The experiment was a 4 × 4 × 2 factorial in a Randomised Complete Block Design (RCBD) with three replicates. Controls were no fertiliser-(F0). In another experiment, the four cassava varieties with three stem portions: Basal-(S1), Middle-(S2) and Top-(S3) and two stem cutting lengths (cm): 15-(L15) and 30-(L30) were laid out as a 4 × 3 × 2 factorial in a RCBD replicated three times. Plants were spaced at 1.0 × 0.8 m and harvested at 12 months after planting. Data estimates on Fresh Storage Root Yield‒FSRY (t/ha), Dry Storage Root Yield‒DSRY (t/ha) and Plantable Stem Yield‒PSY (t/ha) were analysed using descriptive statistics and ANOVAα0.05. Cassava varieties, fertiliser formulations and rates and their interactions were significantly different for all variables. Combination involving V3+F1+R75 resulted in significantly higher FSRY than all others. The FSRY ranged from 9.5±0.6 (V4+F4+R45) to 22.5±0.6 (V3+F1+R75). The DSRY ranged from 2.2±0.1 (V4+F4+R45) to 5.3±0.2 (V2+F2+R75), while PSY ranged from 7.8±0.3 (V1+F4+R75) to 15.4±0.3 (V2+F0). Thevi FSRY for R75 (15.4±0.8) was higher than that of R45 and F0 by 1.1% and 11.9%, respectively. The FSRY was in the order 29.4±0.9-Ikenne ˃24.8±0.6-Ibadan ˃18.5±0.8- Tsonga. The order of FSRY was 22.5±0.6 (V3) ˃19.4±0.4 (V2) ˃12.7±0.3 (V1) ˃12.4±0.6 (V4). Overall, PSY for F0 was the best and increased from 12.5±0.5 (Tsonga) to 18.1±0.4 (Ibadan) to 21.9±0.6 (Ikenne). Across the sites, FSRY ranged from 10.3±2.1 (V4+S3+L15) to 26.4±0.8 (V3+S2+L30). The DSRY ranged from 0.9±0.6 (V4+S3+L15) to 4.7±0.6 (V2+S2+L30) and PSY ranged from 2.5±1.1 (V4+S3+L15) to 9.6±0.3 (V3+S1+L30). The DSRY of L30 was 25.2% higher than L15 (2.4±0.2) and declined from 3.7±0.8 (Ikenne) to 3.3±0.7 (Ibadan) to 1.4±0.3 (Tsonga). The FSRY increased from 9.8±0.6 (S3) to 11.7±0.6 (S2) to 12.1±1.2 (S1). The PSY declined from 16.5±0.6 (Ibadan) to 14.7±0.9 (Ikenne) to 9.5±1.1 (Tsonga). Application of NPK 15:15:15 at 75 kg N, P2O5 and K2O ha-1 to TMEB419 in derived savanna and Urea+KCl at the same rate to IBA011412 in rain forest enhanced yield of cassava. A 30 cm basal stem cutting portion should be adopted for increased storage root production.