nitrogen
Nitrogen is an element that is essential for the economic production of onions. Nitrogen affects the yield, ripening, quality, storage and resistance to diseases. Deficiency of this element reduces fuel size and overall performance. Also, the lack of nitrogen delays ripening and may increase the shriveling of the cuttings in storage.[1]
Excess nitrogen reduces yield and product quality. If more nitrogen is applied before planting than the plant needs, it can reduce plant establishment and promote weed competition and overgrowth. Excess nitrogen in the form of vinegar also has a negative effect on plant growth, and its excessive consumption at the end of the season delays ripening, and this can increase the shriveling of cuttings in storage [1].
phosphorus
Generally, onion is more affected by phosphorus deficiency during the early stages of growth. The reason is that the limited root system and low soil temperature reduce the diffusion or movement of phosphorus to the surface of the roots. Phosphorus deficiency causes growth to stop and development slows down in onions. The amount of lime in the soil reduces the effectiveness of phosphorus fertilizer, so with the increase of lime in the soil, the consumption of phosphorus fertilizer should be increased.
potassium
The abundance of potassium in plants is equal to nitrogen and in some cases even more than that, this element in plants reaches about eight percent of the dry weight of leaves. Although potassium does not play a structural role in the plant like nitrogen, its existence is very necessary for the plant. The essential role of potassium in many physiological and biochemical processes in plants, including photosynthesis, protein synthesis, increasing the transport of photosynthetic materials, maintaining water balance and stimulating enzyme activities, has been proven. [2] In practice, the importance of potassium in relation to performance and quality has been proven. Onion has been reported [3,4]. Potassium is able to convert about 40% of excess nitrate nitrogen in the plant into protein and in this way prevent the accumulation of nitrate in onions [5]. Sufficient amount of potassium in the stalk is important in the storage quality of onions. Potassium deficiency in onions is detected by browning of the tips of older leaves and the production of weak stems. Therefore, it is very necessary to use the right amount of potassium fertilizer in different stages of onion growth to maintain onion growth and quality [6].
sulfur
Onion is one of the important storage vegetables whose quantitative and qualitative characteristics and storage life are affected by environmental conditions and various factors, especially sulfur nutrition. The importance of sulfur nutrition in onions comes from the fact that lack of sulfur causes late ripening of onions, softening of the tissue, thickening of the neck, reduction of hardness and the ability to keep it in storage [7]. Sulfur is an essential food element in onion production, but excessive sulfur increases onion spiciness, which can be undesirable for fresh consumption.
The proposal of Yadnegar Structures Company (Cinco) for onion fertilization is as follows:
Powder NPK chemical fertilizers and liquid fertilizers, liquid sulfur, potassium sulfate and zinc sulfate.
[1] Brown, B. 2000. Southern Idaho fertilizer guide: Onions. Coop. Ext. System Agr. Expt. Sta., Univ. Idaho CIS1081.
[2] Marschner, P. 2012. Marschner’s Mineral Nutrition of Higher Plants. Third Edition. Academic Press, Elsevier.
[3] Yadav, R.L., N.L. Sen, M.S. Frageria, and R.S. Dhaka. 2002. Effect of Nitrogen and Potassium Fertilization on Bulb Production Quality of Onion. Haryana J. Hort. Sci. 31(3+4):297-298.
[4] Masalkar S.D., K.W. Lawande, R.S. Patil, and V.K. Garande. 2000 Effect of potash levels and season on physico-chemical composition of white onion Phule Safed. Acta Hort. 688. p. 17-18.
[5] Malkouti, Mohammad Jafar, Ahmad Baybordi, and Seyed Jalal Tabatabai 2003. Optimum use of fertilizer is an effective step in increasing yield, improving quality and reducing pollutants in vegetable and summer crops and improving the level of community health. Publication of applied agricultural sciences. Tehran, Iran. Page 338
[6] Subba Rao, A. and M. S. Brar. 2002. Potassium, In Fundamentals of Soil Science, Indian Society of Soil Science, Division of Soil Science and Agril. chem. IARI New Delhi-110012, 21: 380-369.
[7] Rabinowitch, H.D. and J.L. Brewster. 1990. Introduction. In: Rabinowitch, H.D. and J.L. Brewster (eds) Onions and Allied Crops, Vol. 1. CRC Press, Boca Raton, Florida.
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