Effects of Mulch and Irrigation System on Sweet Onion: I. Bolting, Plant Growth, and Bulb Yield and Quality

Abstract

<jats:p>Sweet onions (<jats:italic>Allium cepa</jats:italic> L.) are typically grown on bare soil and irrigated with high-pressure systems such as sprinklers or center-pivots. The objective of this study was to determine the effects of irrigation system and mulch on bolting, bulb yield and bulb quality over 3 years. The experimental design was a split plot, where the main plot was irrigation system (drip or sprinkler) and the subplot was the type of mulch (bare soil, black plastic film or wheat straw). The results showed that individual bulb weight and bulb yields under drip irrigation were similar to those under sprinkler irrigation. Plants grown on bare soil had the highest total yield during the three seasons and among the highest marketable yield. There were no consistent differences in the bulb number or yield of plants on plastic film mulch compared to those of plants on wheat straw mulch. Plants on wheat straw mulch had reduced foliar nitrogen content. Variability in yields among mulches and seasons was partly explained by changes in seasonal root zone temperature and soil water potential. Total and marketable yields and weight of individual bulbs increased with increasing root zone temperatures up to an optimum at 15.8 °C, followed by reductions in yields and individual bulb weight at &gt;15.8 °C. Onion bolting increased with decreasing foliage nitrogen content, with plants on wheat straw having the highest bolting incidence. Bolting also increased with decreasing root zone temperatures for the season. Total and marketable yields increased with decreasing mean seasonal soil water potential down to -30 kPa. Irrigation system and mulches had no consistent effect on the soluble solids content or pungency of onion bulbs.</jats:p>

Effects of Mulch and Irrigation System on Sweet Onion: II. The Epidemiology of Center Rot

“…Although there were signifi cant differences in yield due to treatments (Diaz-Perez et al, 2003), those differences could not be attributed to center rot. There were no signifi cant differences in bulb weight among infected bulbs acquiring infections during the earliest to the latest rating periods.…”

“…Higher levels of center rot occurred on onions grown in black plastic in 2000 and in black plastic and bare ground in 2001. The hastening of the onset of center rot by black plastic may be due to the higher soil temperatures observed (Diaz Perez et al, 2003). Center rot has been considered a warmweather disease in onion because it generally occurs during the warmer months when onions are grown.…”

“…Also, in 2000, but not 2001, straw mulch accounted for a greater delay in onset of center rot compared to bare ground, whereas black plastic was associated with an increase in the onset of the epidemic in both years (Fig.2). Unfortunately, the benefi ts of disease control observed on straw mulch may be negated by lower yields and delayed harvest (Diaz-Perez et al, 2003).…”

Effects of Nonwoven Polypropylene Covering during Overwintering on Growth and Bulb Yield of Intermediate-day Onion

“…Soil temperature and moisture content with transparent mulch, black mulch, or NPP covering during the onion growing season were higher than when no mulch was used (Diaz-Perez et al, 2004;Siwek et al, 2013;. Using a plastic mulch or covering is particularly effective for increasing soil temperatures during overwintering and for enhancing the initial vegetative growth of overwintered onions .…”

Effect of Pozzolan and Nitrogen Fertilizer in Reducing Irrigation Water and Soil Moisture Stress in Three Eggplant Cultivars (solanum melongina)

“…Mulches reduce moisture losses through evaporation and other positive effect on soil productivities and accordingly improvement of plant vigor as well as their seedlings (Groenevelt et al, 1989;Ossom et al, 2001;Diaz-Perez et al, 2004;Raemarkrishana, 2006;Kittas et al, 2006;Moreno and Moreno, 2008;and Dong et al, 2007and Dong et al, , 2008and Dong et al, ,2009.…”