Effect of Phosphorus Application on Growth, Yield and Quality of Seed Potato (Solanum Tuberosum L.) Varieties Propagated from Rooted Apical Cuttings in Kenya

Abstract

Potato (Solanum tuberosum L.) is the world’s fourth most important food crop after maize, rice and wheat. In Kenya, it is the second most consumed crop after maize and mainly produced by small-scale farmers. Potato production in Kenya is limited by a number of constraints for example pest and diseases, climatic changes, lack of quality seed and low soil fertility. Farmers plant seeds saved from previous harvest, which are degenerated due to pest infestation and disease infection. Management of fertilizer phosphorus is a critical component of potato production systems. Studies on effect of phosphorus on growth, yield and quality of potato propagated from rooted apical cuttings in Kenya have not been done. The objective was to determine the effect of phosphorus rates on growth, yield and quality of seed potato varieties propagated from rooted apical cuttings. The study was done at Egerton University demonstration field, the Kenya Agricultural and Livestock Research organization (KALRO) research field in Molo and a farmers’ field in Mauche, Njoro. The field experiments were conducted using randomized complete block design (RCBD) with split plot arrangement and replicated three times. Main plot factors were potato varieties (Shangi, Dutch Robyjn, Unica and Wanjiku) and the sub plot factors were phosphorus levels (0, 30, 60, 90 kg P ha-1). Data on growth and yield parameters were collected and subjected to analysis of variance (ANOVA) using SAS version 9.3. Phosphorus rates had significant effect (P˂ 0.05) on plant survival and number of stems and marketable tuber yield. The interaction effects of phosphorus rates and varieties on plant survival, plant height, plant biomass, number of eyes and tuber size was significant (P˂ 0.05). The rates of 60, 90, and 30 kg P ha-1 recorded 16.12, 15.54 and 14.62 tubers per hill, respectively, which were not significantly different but higher than control. The interaction of Wanjiku and 30 kg P ha-1 gave the highest biomass weight of 0.42g and the highest number of large sized tubers of 15.67 per plant. The main effects of variety (P˂0.01) and phosphorus rates (P˂0.05) significantly affected days to physiological maturity and marketable tuber yield. The application of phosphorus had significant effect on starch content, dry matter and specific gravity of tubers. Unica variety recorded higher phosphorus use efficiency at both study sites. Application rate of 30 kg P ha-1 was optimum for the development and yield of potato under the study conditions. The rooted apical cuttings of Wanjiku, Shangi and Unica varieties can be used by the farmers for potato propagation in order to obtain high yield of potato in the study areas and other areas of similar agro ecological zones. Further studies on effect of phosphorus on the growth of rooted apical cuttings in comparison with the conventional tubers are recommended.