In Poland, irrigation increased the firmness of bulbs grown on a mineral soil compared with an organic soil, and subsequently those from the mineral soil stored better (Perlowska and Kaniszewski, 1988). Smart (1986, quoted by Brice, 1994) compared onions from three contrasted fenland soils in the UK: a sandy soil gave earlier-maturing onions with superior skin quality to those from both peaty and silty soils.
In Oregon, USA, a calculated irrigation threshold of 27 kilopascals (kPa) was recommended: decay due to neck rot (Botrytis allii) increased during storage when field water use was higher (Shock et al., 1998). In Maharashtra, India, the effect of withholding irrigation for 12 days prior to harvest, followed by 3 days' curing, resulted in lower storage losses compared with later irrigation and longer curing times (Bhonde et al., 1996). Current recommendations are to apply the final irrigation 10-15 days before onion harvest (Bhonde, 1998).
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