Irrigation Criteria for Drip-irrigated Onions

Abstract

<jats:p>Long-day onion (<jats:italic>Allium cepa</jats:italic> L. `Vision') was subjected to five soil water potential (SWP) treatments (–10, –20, –30, –50, and –70 kPa) using subsurface drip irrigation in 1997 and 1998. Onions were grown on 1.1-m beds with two double rows spaced 0.56 m apart and a drip tape buried 13 cm deep in the bed center. Soil water potential was maintained at the five levels by automated, high-frequency irrigations based on SWP measurements at 0.2-m depth. Onions were evaluated for yield and grade after 70 days of storage. In 1997, total and colossal (bulb diameter ≥102 mm) yield increased with increasing SWP, but marketable yield was highest at a calculated –21 kPa because of greater decomposition in storage in wetter treatments. In 1998 total, marketable, and colossal-grade onion yield increased with increasing SWP. Onion profits were highest with a calculated SWP of –17 kPa in 1997, and at the wettest level tested in 1998. Storage decomposition was not affected by SWP in 1998. Maintenance of SWP at –10 and –20 kPa required, respectively, 912 and 691 mm of water in 1997 and 935 and 589 mm of water in 1998. Onion crop evapotranspiration from emergence to the last irrigation totaled 681 mm in 1997 and 716 mm in 1998.</jats:p>

Nutrient content and yield in relation to top breakover in onion developed from greenhouse‐grown transplants

“…During the 2 years precipitation amounts were different, with that in 2006 being nearer to normal. It was found that marketable production was increased under more frequent irrigation 13. However, Shock et al 13 conducted their work under normal growing conditions for the location.…”

“…It was found that marketable production was increased under more frequent irrigation 13. However, Shock et al 13 conducted their work under normal growing conditions for the location. The relatively more normal, drier conditions in Oklahoma appeared to be more conducive to plant development and deposition of most nutrients in bulbs.…”

“…Problems can occur during this time that may result in reduced quality. This has led to the concept of undercutting bulbs when convenient, which can stimulate maturation,13 rather than harvesting when a specific amount of breakover has occurred 14. The time between the beginning of top breakover and until most, or all, of the tops have broken over may affect nutrient content in bulbs.…”

Distribution of limited irrigation water based on optimized regulated deficit irrigation and typical metheorological year concepts

“…In this case, the curve number used was 82: Hydrologic soil group "C"; "Good" hydrologic condition; "Row crops"; and "Contoured labour" (land slope < 2%). The first K y stage of onion [K y (i)] is divided in two substages to differentiate between establishment [K y (i )] (where no high stress should by applied) and vegetative development [K y (i )] (where higher stress is allowed) (Shock et al, 2000;Bekele and Tilahun, 2007) (Fig. 3).…”

“…The irrigation amounts in the area under no deficit conditions should be around 700 mm (López-Urrea et al, 2009a). Results of several deficit irrigation (DI) experiments (Shock et al, 2000;Martín de Santa Olalla et al, 2004;Kadayifci et al, 2005;Bekele and Tilahun, 2007) indicate that to obtain maximum yield it is necessary to avoid water deficit, especially during the bulb development, while during the vegetative and ripening periods the crop appears to be less sensitive to water deficit.…”