Narcissus and Daffodil

70 G.R. Hanks
compaction and its effects on clod formation and reduced crop growth, bed
formers are used to produce an even soil particle density prior to planting. All
cultivations should take account of the need to reduce soil compaction by reducing
machinery movements and the area affected by wheelings.
Soil disinfection
In the UK, where bulbs are grown on heavier soil, it is not usual to use soil disinfection
on a field scale. However, nematodes move more freely in sandy soils, and in
the Netherlands soil disinfection is routinely used in bulb growing. Prior to assigning
a field for narcissus production, soil samples should be sent to a diagnostics
laboratory for identification and counts of nematodes present, including stem
nematode, virus vector nematodes and PCN, as appropriate. Sterilants used in the
Netherlands include metam-sodium and dichloropropene, which should be used
at sufficient depth to control the target organisms (up to 40 cm for Pratylenchus).
Soil disinfection may also be used to control soil-borne fungi such as white root rot
(Mantell and Wheeler, 1973).
Fertilisers
Fertilisation for narcissus should aim to maintain adequate levels of phosphate
(P 2 O 5 ) and potash (K 2 O) in the soil and to supply adequate (but not excessive)
nitrogen (N). Nutritional experiments with narcissus have proved difficult because
of the reserves within the bulbs (Bould, 1939; Hewitt and Miles, 1954). Long-term
experiments showed that there is little short-term response to N or P 2 O 5 , that
adequate K 2 O is needed, and that fertilisers do affect growth in subsequent years
(NAAS, 1961; Wallis 1966, 1967b, 1968). K is beneficial in the second year of
growth (Fodor and Sólymos, 1975).
Fertiliser recommendations for general bulb growing under UK conditions are
given in MAFF (1994). Soil samples should be taken well in advance of planting
for the determination of P 2 O 5 , K 2 O and magnesium (Mg) levels, while N requirements
are usually based on the previous cropping of the land, the highest rates
being applied following demanding crops such as cereals. The maximum rates
suggested, where the index has fallen to zero for a particular nutrient, were (in kg/ha)
100 N, 125 P 2 O 5 , 250 K 2 O and 150 Mg, after deducting the amount of nutrients
applied as organic manures. If necessary to apply magnesium, kieserite or calcined
magnesite is used, unless liming is also necessary, in which case magnesian
limestone is used. P 2 O 5 , K 2 O and Mg are usually applied after ploughing and
worked in before planting, but it is recommended that N is applied later as a topdressing,
shortly before crop emergence (to avoid scorching the foliage); this
reduces leaching by winter rainfall. In practice, growers may prefer to apply a
compound fertiliser before planting. Manganese deficiency may occur in narcissus
grown on soil where the pH is high, and manganese sprays should be applied in
advance of deficiency becoming evident.
There may be advantages to applying fertilisers as split-dose applications (preplanting
and as a spring top-dressing) (Parker, 1935) and to counter the effect of
rain (Lyakh, 1988), but there was no advantage of using repeated high rates of N
(Lees, 1960). No advantage was demonstrated in trials of applying fertiliser into