Abstract
Potassium and nitrogen are the elements present in the highest percentage in the onion dry matter. The objective of this experiment was to evaluate yield and post-harvest conservation of Vale Ouro IPA-11 onion cultivar regarding to nitrogen and potassium levels. The experiment was carried out in Petrolina-PE, Brazil, from June to September 2009. The experimental design was a completely randomized block in a 4 x 3 factorial design, composed of four nitrogen levels (0, 60, 120 and 180 kg ha-1) and three potassium levels (0, 90 and 180 kg ha-1) with three replications. The highest yield of commercial bulbs was achieved at an estimated N level of 172.6 kg ha-1. The lowest yield of noncommercial bulbs was estimated at N level of 147.0 kg ha-1. Lower percentage of smaller bulbs (class 2) were obtained by increasing levels of N x K, with a quadratic effect at the dose of 90 kg ha-1 K2O and minimum production point with 127.6 kg N ha-1 (20.3%). Regarding larger caliber bulbs (class 4), linear effects were found both in the absence and for the level of 90 kg ha-1 of K2O as levels of N were increased. When the highest level of 180 kg ha-1 K2O was applied, the level of 92.8 kg ha-1 of N was estimated as the one that would promote the highest bulb yield of this class (35.4%), and 5.3% was found in the lack of potassium fertilization.
Highlights
Among vegetables, onion (Allium cepa) ranks third place in economic importance in Brazil
The beneficial effect of potassium can be found in different traits of agricultural products, such as color, acidity, resistance to shipping, handling and storage, nutritional value and industrial qualities (Malavolta, 2006)
Onions extract large amounts of potassium, in general, responses by the crop to this nutrient have not been found (Filgueira, 2008) and there are few results that confirm a significant effect of K fertilizer on the yield
Summary
Onion (Allium cepa) ranks third place in economic importance in Brazil. Nitrogen (N) contributes markedly to improving the production of onion, being absorbed in large amounts, exceeded only by potassium (K) (Porto et al, 2007, May et al, 2008). N takes place in other physiological processes vital to the life cycle of plants, such as ion absorption, respiration, cell multiplication and differentiation and inheritance (Epstein & Bloom, 2006). Onions extract large amounts of potassium, in general, responses by the crop to this nutrient have not been found (Filgueira, 2008) and there are few results that confirm a significant effect of K fertilizer on the yield
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