MODELING THE EFFECTS OF CROP SPACING AND INORGANIC FERTILIZER ON THE POTATO TUBER YIELD AND SIZE USING FIRST ORDER TWO-LEVEL FACTORIAL DESIGN

Abstract

The essential nutrients for growth and productivity to all living organisms, specifically plants are Nitrogen, Phosphorus and Potassium. However, there are other factors that contribute to optimum yield of crops; these factors are land availability, farming techniques, crop spacing, organic fertilization and climatic conditions. The current research study investigated the optimal levels of potato tuber yield and size, recorded the impact of crop spacing and inorganic fertilizers (nitrogen and phosphorus) as factors of interest that are known to affect the production of potato crop, and to compare the model fit using both full and fractional factorial experiment. A two-level full factorial and the fractional factorial experiments   3 2 with three replicates were employed to measure the impact of the selected factors on the potato tubers. The study used the Randomized Complete Block Design (RCBD), where land acted as blocks and treatments randomized within blocks. The first order models were fitted by using the method of least squares. The data collected was subjected to data analysis using descriptive statistics and Inferential Statistics ANOVA utilizing R statistical software. The descriptive statistics was presented by use of frequency distribution tables. Results indicate that the highest average optimum yield was 18.64 t ha-1 when nitrogen and phosphorous were supplied at the higher rates of 80 kg ha-1 and 155 kg ha-1 respectively with crop spacing of 65 cm by 20 cm and lowest average yield was 12.12 t ha-1 when nitrogen and phosphorus were supplied at lower rates of 40 kg per hectare and 77 kg per hectare respectively with spacing of 75 cm by 30 cm. Furthermore, the average optimum size of potato tuber was recorded as 12.18 cm when nitrogen, and phosphorus was supplied at 40 kg per hectare, and 155 kg per hectare with crop spacing of 75 cm by 30 cm and smallest average size of potato tuber was recorded as 8.74 cm when nitrogen, and phosphorus was supplied at lower rate of 40 kg per hectare and 77 kg per hectare respectively with spacing of 65 cm by 20 cm. The effect crop spacing shows a negative linear effect on the yield of potato tubers only but significant on both yield and size of potato tuber whereas nitrogen (N) and phosphorus (P) shows positive linear effects on both the yield and size of potato tuber with phosphorus being significant in all models. Additionally, the use of fractional factorial experiment gave better model fit  80% 2 R  when compared to full factorial experiment  60% 2 R  . The obtained results are close to the national estimates on the yield of potato tuber which stands at 14 tons hectare and the global average of 17.2 tons per hectare respectively. The current study will be important in designing the necessary interventions within country in order to improve production of potato crop.