Botanical and Agronomic Characteristics of Azarshahr Red Onion
Azarshahr Red Onion is a long-day, open-pollinated local landrace with a growth period of 180 to 190 days, primarily cultivated in East Azerbaijan Province. The outer skin of Azarshahr Red Onion ranges from red to dark red. The bulbs have an average weight of 169.55 grams, a diameter of 7.61 cm, a length of 4.94 cm, a shape index (length-to-diameter ratio) of 0.65, a leaf length of 29.42 cm, an average of 9.49 leaves, 8.14 edible layers, 2.36 centers, 12.15% dry matter content, and 10.26% soluble solids.
Land Preparation and Soil Management for Azarshahr Red Onion Seed Cultivation
Onion cultivation requires a uniform and light-textured topsoil. Therefore, sandy loam to loamy soils with high organic matter are best suited for its growth. Planting onions in heavy clay soils is not recommended due to root growth inhibition and harvesting difficulties, while sandy soils are avoided because of high water and fertilizer requirements. Regardless of soil type, the ideal pH for onion cultivation ranges from 6 to 6.8, although alkaline soils are also acceptable. Onions are sensitive to soil salinity, which can significantly reduce yield; thus, saline soils are unsuitable for onion cultivation.
Land preparation begins with plowing in the fall, followed by disking before sowing to create a fine seedbed and prevent soil compaction. In light soils, a light rolling may be performed after preliminary tillage.
Traditional Method of Planting Azarshahr Red Onion
In the traditional method, after land preparation, the field is divided into plots. Seeds are then sown by broadcasting and covered with about 1.5 cm of sand. The germination time depends on temperature and moisture availability. Throughout the growth period, weed control is usually done manually (hand weeding) or by using herbicides. During crop management, about 1.5 to 2 tons per hectare of chemical fertilizers are applied. However, excessive fertilizer use not only leads to products containing non-permissible elements but also degrades soil structure.
Planting Time for Azarshahr Red Onion in the Traditional Method
In cold regions such as East Azerbaijan Province, where winter frost occurs, onions should be planted as soon as spring frost ends. The spring sowing window is limited, as the soil temperature must be sufficiently warm to allow for seed germination and seedling emergence. Delayed sowing results in insufficient plant growth and the production of thick-necked plants instead of bulbs.
Early sowing is also risky; if germinated seeds are exposed to temperatures below -2°C for more than two days, they may be damaged. Even if the seeds are not directly killed by low temperatures, germination will be delayed, leading to seedling death. Additionally, soil crusting can hinder seedling emergence.
Considering climatic conditions, the planting season in the province extends from late March to late April.
Seed Rate for Azarshahr Red Onion in the Traditional Method
Several factors, such as soil type and quality, seed vigor, and planting method, influence seed consumption rates. In traditional cultivation, the seed rate is relatively high, reaching up to 20 kg per hectare. However, with careful sowing practices and the use of high-quality seeds, the seed rate can be reduced to about 10 kg per hectare.
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