EFFECTS OF SEED TUBER SIZE AND NPK FERTILIZER ON SOME YIELD COMPONENTS OF COLEUS POTATO (Solenostemon rotundifolius (Poir) J.K. MORTON)

Abstract

A field experiment was carried out to assess the effects of 3 seed tuber sizes (< 5, 5 ≤ 15 and > 15 g) and 4 levels (0, 100, 200 and 300 kg ha-1) of NPK fertilizer on some tuber yield components of Coleus potato (Solenostemon rotundifolius). Factorial combinations of the 3 seed tuber sizes and the 4 NPK application rates formed 12 treatments evaluated. The treatments were fitted into a Randomized Complete Block Design (RCBD) with three replications. Data were collected on number of healthy and rotten tubers, fresh weight of tubers, length of tubers and girth of tubers. The measured variables differed significantly (P ≤ 0.05) depending on seed tuber size. The smallest seed tuber (< 5 g) recorded the highest number of healthy tubers but was similar to the other seed tubers. Total tuber fresh weight from < 5 g seed tubers (839.1 g) was significantly (p ≤ 0.05) heavier by 51.2 % than that of > 15 g seed tubers (554.8 g). Application of 300 kg NPK ha-1 increased the number of rotten tubers (51) relative to the control treatment (28). The 0 and 100 kg NPK ha-1 treatments produced heavier tubers than the 200 and 300 kg NPK ha-1 treatments. These results signify that the smallest seed tuber (< 5 g) enhanced tuber yield better than the other seed tubers. It is evident that Coleus potato could yield well without NPK fertilization when soil nitrogen is high (i.e. > 0.2 %). further improvement (Prematilake, 2004). Consequently, these tuber crops are propagated by vegetative methods using tubers of varying shapes and sizes. Information on the economic importance and agronomic practices of Coleus potato which has suffered research neglect for several years is limited (Enyiukwu et al., 2014). Concerted efforts at conserving, documenting and promoting the dynamic use of Coleus potato is now required (Olojede et al, 2005). Evidently, agronomic research on Coleus potato is scanty and more are needed before any meaningful advancement on the crop can be made. Although there are coordinated efforts by the National Root Crops Research Institute (NRCRI), Nigeria, to improve the cultural and agronomic practices of Coleus potato production, more associated researches are required in multiple locations and with different experimental treatments. This experiment was therefore designed to investigate the effects of seed tuber size and NPK application on some tuber yield components of Coleus potato. Materials and Methods Keywords: Coleus potato, NPK application, seed tuber, tuber yield, Vom