SUMMARY OF RESEARCH OPTIMISING NITROGEN, PHOSPHORUS AND POTASSIUM NUTRIENT RATE COMBINATIONS FOR ENHANCED POTATO (SOLANUM TUBEROSUM L.) GROWTH, TUBER YIELD AND QUALITY IN RWANDA

By Adrien Turamyenyirijuru, PhD Student in Agronomy, Department of Crops, Horticulture & Soils (CHS)/Faculty of Agriculture/Egerton University  

Potato is considered a strategic commodity with the potential to improve food and nutrition security, and even generate income in Rwanda. Despite its potential, potato intensification levels remain low in Rwanda, translating into low yield. The low yield is mainly due to the decline in soil fertility coupled with the adoption of blanket fertiliser recommendations.

EXPERIMENTS

Field experiments were conducted in Birunga, Mudende [L₁]) and Buberuka, Rwerere [L₂] highlands Agro-Ecological Zones (AEZs) of Rwanda, during season A 2017 [S₁] and B 2017 [S₂] to determine the effects of varying rates of N, P and K on growth and yield of potato.

The experiments were laid out using a randomised complete block design with factorial arrangement, with four replicates. Factors were N rates (N_X); (i) N₁-0 kg ha^-1, (ii) N_{2 –} 50 kg ha^-1 (iii) N_{3 –} 100 kg ha^-1 ; P₂O₅ rates (P_X); (i) P₁-0 kg ha^-1, (ii) P_{2 –} 50 kg ha^-1 (iii) P_{3 –} 100 kg ha^-1and K₂O rates (K_x); (i) K₁– 0 kg ha¹and (ii) K₂– 50 kg ha^-1. Stem height, number of main stems per plant, leaf area index and tuber yield were measured.

Potato farm management N, P, K site-specific

ANALYSIS

Analysis of variance for the data, performed using SAS-version 9.2, revealed the existence of soil fertility gradient, with difference statistically significant between the two locations and farms within both locations. In general, the two locational and seasonal results showed similar response patterns with regard to effects of N, P, K and their combinations (N×P×K) on potato growth, tuber yield and quality. Effects of location, N, P, K and N×P×K were found to be significant on all growth, tuber yield and quality traits except the number of main stems per plant, while effects of seasons were significant on all growth and yield attributes and non-significant on the number of main stems per plant and all potato quality traits. With regard to tuber yield, L₁, S₂, N₃, P₃ and K₂ factor levels and N₃×P₃×K₂ performed better than other treatments. N₃×P₃×K₂ recorded highest tuber yields: (32.73 ± 0.43) t ha^-1[L₁] and (29.36 ± 0.41) t ha^-1 [L₂] and (31.05 ± 0.52) t ha^-1for pooled ANOVA. Contrarily to what happened at L₂, effects of N₃ and N₂ on tuber yield as well as N₃P₃K₂ and N₂P₃K₂ were not significantly different from each other.

Airoponic mini tubers

With regard to potato quality, except 331, 231 and 131 treatments which were found suitable for making potato salad, whole boiled and canned potatoes, all other treatments (with >1.080, > 14%, >20% and < 0.30% of specific gravity, starch, dry matter and reducing sugar content, respectively) were qualified suitable for making French fries, chips and dehydrated potatoes (flakes). N₂, P₃ and K₂ are recommended to L₁ whereas N₃, P₃ and K₂ are recommended to L₂.