Effect of organic and inorganic fertilizers on sweetpotato genotypes for yield stability
A field experiment was carried out in 2013 and 2014 at the National Root Crops Research Institute, Umudike, in the rainforest zone, to evaluate the effect of organic and inorganic fertilizer on sweetpotato genotypes for yield stability. The experiment was carried out using a split plot in a randomized complete block design replicated three times. The treatments included ten fertilizer levels (NPK 15:15:15 fertilizer (100kg/ha, 200kg/ha, 300kg/ha); poultry manure (10t/ha, 20t/ha, 30t/ha and combination of NPK 15:15:15 and poultry manure: 5t/ha+50kg/ha NPK, 10t/ha+100kg/ha NPK, 15t/ha+150kg/ha NPK and 0t/ha PM/NPK as control); and eight sweetpotato genotypes: Centennial, Ex-Oyunga ,UMUSPO/3 UMUSPO/1, NRPS/05/3D, Ex-Igbariam, TIS/8164, and TIS/87/0087 were involved in the trial. Data on some growth and yield parameters were measured and subjected to Genotypes and Genotype -by- Environment interaction (GGE) biplot and Additive Main effects and Multiplicative interaction (AMMI).The results revealed that UMUSPO/1 (G8), TIS/87/0087 (G6) and TIS 8164 (G5) had significant mean saleable root yield (t/ha) above the grand mean and largest IPCA1 scores respectively, while Centennial (G2) Ex-oyunga (G4) and NRSP/05/3D (G1) had low saleable root mean yield and lowest IPCA1 score. Results also showed that yield increase are not totally due to genetic potential of the cultivars but also due to improved agronomic practices with observed good yields supported by environments such as 10t/ha poultry manure in 2014 (E12), 10t/ha poultry manure + 100kg/ha NPK in 2013 (E9), 5t/ha poultry manure + 50kg/ha NPK in 2013 (E8) and 30t/ha poultry manure (E4) in 2013. From the results, sweetpotato farmers can cultivate any of the genotypes in any of the E4, E8, E9 and E12 environments for high saleable root yield of sweetpotato.
Keywords: Organic, inorganic, AMMI, genotype x environment interaction and saleable root yield
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