Molecular Soil Biology 2024, Vol.15, No.5, 227-235 http://bioscipublisher.com/index.php/msb 233 4.4 Effect of water stress on bulb nutritional composition Wet condition favoured bulb nutritional and proximate compositions above drought and waterlogging (Table 3; Table 4). Desclaux (2011) also reported that drought decreased the nutrient uptake in N, K and P of Hordeum vulgare L. Nitrogen uptake was also hindered by waterlogging in bread wheat (Arata et al., 2019). This could be ascribed to negative effect of drought on the microbial mineralization of organic matter, which in turn affects the amount of inorganic nutrients available for plant uptake, potentially impairs the mineral nutrition of plants. Kuchenbuch et al. (2018) showed that low levels of soil moisture due to drought reduced root growth and the rate of potassium inflow in onion plants. Urbina et al. (2015) reported that in monoculture and mixed plants, K decreased under drought while the K content in leaves of peanut plant (Rachis hypogaea L.) was unchanged under drought. Sanchez-Rodriguez et al. (2010) observed a lower concentration and uptake of P in watermelon and cherry tomato under drought condition. Except nitrogen free extract (NFE), all fruit proximate composition parameters were better under wet than waterlogging and drought conditions. Within moisture regimes of wet condition, watering three times per week was optimal. In agreement with this, Suleimon (2017) recorded a decrease in crude protein and crude fibre contents of Brassica napus L. under drought conditions. As obtained in this study, the highest ash content recorded under wet conditions is in line with the findings of Aliyu et al. (2017) who observed an increase in ash content of alfalfa plant under well-watered condition, while the lowest contents were recorded under waterlogged condition. Morad (2012) also reported that there was a significant decrease of N, P, Mg, K, Mn and Zn concentration in wheat and barley shoots by waterlogging. 5 Conclusion and Recommendations The study revealed that onion plants grown under wet conditions performed better in growth and yield as well as nutritional values than under water stress (drought and waterlogging). The plant performed optimally under wet condition and partially under drought while waterlogging had significant negative impact on it. It is therefore, recommended that onions, under sreenhouse condition, can be watered regularly to achieve good yield but watering 3 times per week to field capacity is the best in achieving optimal yield and nutritional values. However, controlled experiments in sreenhouse conditions may not be totally applicable under field conditions. This limitation might influence the applicability of the results to field agricultural practices. There is therefore, a need for a research of this nature on long-time effect on the field. In addition, there is a need to investigate the deficit level at which a reasonable level of water saving can be achieved without significant growth yield loss, which could be of significant importance for both onion production and water conservation. Authors’ Contributions Otitoloju Kekere designed, supervised the research, and prepared draft of the manuscript. Augusta Omolara Ogbedebi set up the experiment and collected data. Yetunde I. Bulu and Taiwo Ekundayo co-designed and monitored the experimental process. Olumakinde Akinbuwa performed statistical analyses of the data. All authors read and approved the final manuscript. References Ahmad A., Khan F., and Ali A., 2021, Nutritional composition and health benefits of onion, Journal of Food Science and Technology, 58(10): 3779-3787. Ahmed M., Qadeer U., and Ashraf M.Y., 2015, Physiological and biochemical attributes of barley cultivars subjected to drought stress at seedling stage, The Journal of Animal and Plant Sciences, 25(1): 166-172. Aliyu A., Buhari A., Mohammed H., and Ibrahim H., 2017, Impact of different moisture regimes on the proximate composition of Alfalfa (Medicago sativa L.), International Journal of Plant and Soil Science, 15(2): 1-7. Aliyu L., Aliyu A., and Adamu K., 2009a, Economic importance and efficiency of onion production in Sokoto Metropolis, Nigeria, Nigeria Journal of Agriculture, Food and Environment, 5(1): 69-73. Aliyu L., Gummada J.A., and Aliyu M., 2009b, Economic Importance of Onion, Journal of Agricultural and Biological Science, 4(4): 11-15. Aliyu L., Tanimu A., and Isyaku, M., 2009c, Onion production in Nigeria: A survey of production trends and constraints, Journal of Horticultural Research, 7(2): 71-78.
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