International Journal of Horticulture, 2024, Vol.14, No.4, 207-217 http://hortherbpublisher.com/index.php/ijh 208 flowers) (Teshome et al., 2015). Onions are day length sensitive; several onion types exist depending upon latitude at which they grow. Onion prefers well-drained sandy loam with high content of organic matter (Sitote and Tadese, 2018). The optimum altitude ranging from 700 and 2,200 meter above sea level (masl) and optimum growing temperature lies between 15 °C and 23 °C (Anon, 2003). The crop requires 350-500 mm of water over the growing season (https://www.fao.org/land-water/databases) hence adequate moisture possibly through irrigation is important in the production of onions. Onion has shallow root system so it extracts very little water from depths beyond 60 cm. Thus, upper soil areas must be kept moist to stimulate root growth and provide adequate water for plant. Onion growth and development is greatly influenced by mulching and irrigation (Rahman et al., 2013). Mulching is an important technology which decreases the loss of soil water through evaporation and conserve soil moisture thus reduces the irrigation requirements, increasing root development, reducing weed attack and inducing earlier harvest of crop (Mahajan et al., 2007). The most common objective of mulching is to enhance crop growth by altering soil temperature and conserving soil moisture (Lamont, 2005). Onion is ideally adapted to developing without extreme heat or cold or abundant rainfall in a moderate climate. Bolting is induced by low temperature during the rabi season, whereas abrupt rise in temperature causes early maturity and small sized bulbs (Khokhar, 2009). Sudden temperature rise starts in the month of March-May during which crop evapotranspiration rises (4-10 mm per day) leading to depletion of soil moisture level causing water stress to plant thereby, early maturity of bulbs and low yield (Abasi et al., 2009). To fill this soil moisture gap onion requires frequent, light irrigations (10-15) to keep the soil root zone moist; this has led to more water use even in water-scarce areas. 2 Materials and Methods 2.1 Experimental site The research was conducted at Local farmers field at Lamahi Municipality, ward no.5, Kolahi of Dang, Nepal. The geographical location of the sites was 27.865789º N latitude and 82. 526935º E longitude with the elevation of 266 masl. The climatic condition of Lamahi is sub-tropical with more than 80% of the total annual rainfall during the monsoon season from June to September. Since the crop is winter season crop, the winter temperature usually ranged from 12 °C to 22 °C. The soil of research field was loamy soil with pH 6.5. 2.2 Description of materials used in experiment: 2.2.1 Varietal details Nasik Red N53 variety of onion was selected for the research experiment. It is medium red skin colored hybrid variety, flat oval in shape, sowing round the year with good yielding capacity. The bulb looks attractive and have good storing ability. 2.2.2 Seedling preparation Nasik Red N53 variety of seeds were sown in the nursery bed to prepare the seedling of onion. Onion seed was soaked prior to sowing. A fine seed bed was prepared with adequate amount of organic matters and fertilizers. 7-10 weeks old seedlings are usually transplanted in the main field under ideal growing conditions. 2.2.3 Mulches As inorganic mulching, white plastic with 30-micron thickness was used in the experiment. Similarly, Rice straw, rice husk, neem leaves, banana leaves and saw dust were used as organic mulches. These mulches were weighed initially and 1kg/plot were kept in the simultaneous treatment plots.
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