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Sweet potato productivity in India is either stagnated or lowering down over the past many years.The main reasons for low yield are conventional blanket recommendation of fertilizers, lower nutrient use efficiency and imbalance in the use of fertilizers. Recommendation of major nutrients, nitrogen, phosphorus and potassium (NPK) based on quantitative approaches will augment sweet potato production per unit area by increasing the nutrient use efficiency. The present study calibrated the Quantitative Evaluation of Fertility of Tropical Soils (QUEFTS) model for the estimation of NPK requirements and fertilizers recommendations for different target yields of sweet potato. The QUEFTS basically work on the principle of NPK nutrient interactions and climate adjusted yield potential of a region. Published data sets from several field experiments related to NPK carried out till date were collected to reflect the environment variability. The results of the present study showed that to produce one ton tuber, 16:6:18 kg N, P and K respectively would be needed with the internal efficiencies of 61:167:57 kg tubers kg -1 NPK removed. The maximum accumulation and dilution (kg tuber kg -1 nutrient removed) of N Downloaded by [Wilfrid Laurier University] at 04:31 23 June 2016 A c c e p t e d M a n u s c r i p t 2 (40, 80), P (96, 272) and K (30, 85) were also derived as standard parameters in QUEFTS for optimum fertilizer recommendation in tropical and sub-tropical regions of India. The observed yields of sweet potato with different amount of nutrients were in agreement with the values predicted by the model. Therefore, it is utmost important to have the results of the study validated in major growing environments of India for fertilizer recommendation in sweet potato.

The effect of different hermetic and non-hermetic closure-types (aluminum foil, cotton bung, cotton plug, polypropylene cap and Steristopper) on potato (Solanum tuberosum L.) plantlets growth and chlorophyll contents was studied in three genotypes belonging to different maturity groups. Plantlets grown in culture tubes closed with aluminum foils and polypropylene caps had higher fresh mass and shoot length, but lower chlorophyll contents, higher senescence index and various morphological abnormalities. Non-hermetic closures like cotton plugs and Steristoppers were found optimum for plant growth without any morphological abnormalities. Besides, these plantlets exhibited low senescence index and had higher chlorophyll contents that favour acclimation to ex vitro conditions.

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