Abstract
The in-season trend of onion biomass and its yield depend on the dynamics of nitrogen (N) and sulfur (S) uptake. This hypothesis was verified based on a three-year (2009, 2010, 2011) field study (Poznan University of Life Sciences). The experimental factors consisted of N: 0, 60, 120 and S: 0, 30, 60 kg ha−1. The dynamics of onion total dry weight (TDW), total N uptake (TNU), and total S uptake (TSU) were determined at 10-day intervals. The in-season course of TDW and TNU was best described by the expolinear and TSU by the quadratic growth model. Sulfur uptake increased in onion at day after emergence (DAE) 40, independent of its rate with respect to SN control, resulting in increased N by 50%, and consequently higher yield. The maximum absolute S uptake rate (SCm), a factor defining yield, increased progressively with the N rate, but only in the absence of S application. Plants fertilized simultaneously with S and N showed a more complicated impact on SCm. The N rate of 120 kg ha−1 resulted in SCm reduction, leading to a yield drop. The expolinear model indicated an onion growth disturbance, revealed under unfavorable growth conditions, leading to yield depression.
Highlights
Vegetables from the Allium genus, such as onion (A. cepa), garlic (A. sativum), and leek (A. ampeloprasum var. porrum), are among the main sources of bioactive compounds in the human diet all over the world
Field tests on onion (Allium cepa L.) growth during the growing season were conducted in 3 consecutive years, 2009, 2010, and 2011, at the Brody Experimental Farm (University of Life Sciences in Poznan; 52◦ 440 N, 16◦ 280 E)
The key objective of the present study was to explain the impact of progressively increasing rates of N and S fertilizers on the dynamics of onion biomass during the growing season and eventually on its yield
Summary
Vegetables from the Allium genus, such as onion (A. cepa), garlic (A. sativum), and leek (A. ampeloprasum var. porrum), are among the main sources of bioactive compounds in the human diet all over the world. Vegetables from the Allium genus, such as onion (A. cepa), garlic (A. sativum), and leek Porrum), are among the main sources of bioactive compounds in the human diet all over the world. Onion (Allium cepa L.) is the most widely cultivated species of the genus. Both onion parts—leaves, but especially the bulb—are rich sources of bioactive compounds, mainly polyphenols, among which flavonoids dominate, characterized by elevated antioxidant and antibacterial activities. The qualitative health attributes of onion are widely exploited in human protection against cancer, high blood pressure, and infection [1,2]. Onion consumption has reached high levels in the United States and Europe [3]. The highest yields, at levels of 48–52 t ha−1 , are reached in the United States and the Netherlands, while the world average is much lower at around
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