Review on the effect of nitrogen and phosphorus fertilizer rates on seed yield of onion (Allium Cepa L.)

Abstract

Onion is an herbaceous biennial monocot cultivated as an annual. In recent estimations, there are about 750 species in the genus Allium, among which onion, Japanese bunching onion, leeks and garlic are the most important edible Allium crops. The higher seed yield in onion cultivars was due to the higher number of seed stalks per plant and to a wider umbel diameter which were influenced by application of N and P fertilizers. The number of flower opening on each day was influenced by the number of hours of sunshine and concentration of phosphorous and nitrogen. N and P treatments tended to lower bolting percentages. The yield of seed per plant increased as the nitrogen in the nutrient solution increased where seed stalks were produced. The early flowering by the application of P fertilizer was due to fact that phosphorus involvement in metabolic and physiological activities. The highest rates of Phosphorus 115 and 147 kgha −1 gives better growth and yield. There is maximum response of onions to Phosphorus fertilization in the range 0-52 kg ha-1. Plant roots take up nitrogen from the soil solution principally as nitrates (NO3-) and NH4 + ions. Nitrate is the preferred form of N for uptake by most plants, and it is usually the most abundant form that can be taken up in well-aerated soils. Nitrogen fertilizer application improves phosphorus uptake from the soil. Onion absorb phosphorous in the form of H2PO4-and H2PO4-. Too much phosphorus level affects plant growth by suppressing the uptake of iron, potassium and Zink.