Narcissus and Daffodil

68 G.R. Hanks
(as well as natural erosion) on sloping sites can move pesticide residues into watercourses.
Concentration of pesticides has been recorded in colluvium and in the
sediment of surface pools where the watertable was high (Harrod et al., 1991;
Harrod and Rickson, 1994).
Soil
Silts or very fine sandy loams are ideal for narcissus growing. In the UK, bulbs are
grown successfully on a variety of silt, silt loam, brick-earth and peat soils. In the
Netherlands, narcissus were traditionally grown in sandy soil and it was once
considered that bulb quality could not be maintained on heavy silt clay soils
(de Vroomen and de Groot, 1991). However, they are now grown on the heavier
polders, factors involved including the pressure on prime agricultural land and
the need, on sandy soils with a high water content, to practice regular soil sterilisation
to control nematodes. There have been few comparisons of growth in different
soil types, although Szlachetka (1976) reported better narcissus growth in light
black-earth soils than in heavy alluvial soils. It has been reported that narcissus
bulbs were larger and more susceptible to base rot when grown on peat, rather
than mineral, soils (ADAS, 1982a).
According to ADAS (1985a), bulb soils should be deep, fertile, well drained
and moisture retentive (water holding capacity >40 mm per 300 mm depth),
while the level of organic matter should be >3% and the pH value should generally
be between 6.0 and 7.5. In the bulb growing areas of eastern England,
typical mineral soils have 2.5–3.0% organic matter, while peat soils may have up
to 25% (J.B. Briggs, personal communication). Weed control is difficult in highly
organic soils. Narcissus bulbs are susceptible to poor growth due to compaction
(De Haan and van der Valk, 1971). Although the observed root spread of narcissus
was similar in different soil types, it was low in comparison with tulips, so a
good soil structure is needed (Rees, 1972). Heavy soils, stones and clods can
damage bulbs and make lifting difficult, requiring the use of stone and clod
removers. In ‘sticky’ soils it may be difficult to produce soil-free bulbs unless
bulbs are washed, a process which spreads diseases and creates disposal problems
(ADAS, 1987).
Crop rotation and site history
Crop rotation should aim to maintain a good soil structure and reduce pest,
disease and weed problems. Leys, peas, barley or early potatoes often form part
of the rotation with narcissus. Preceding crops leaving a high residue (e.g., cauliflowers)
should be avoided, as high levels of soil nitrogen may encourage basal rot
(Hanks et al., 1998a). Rotations should allow adequate time for soil preparation
before bulb planting. Narcissus should not follow crops treated with sulphonylurea
herbicides, which can cause morphological damage (Greenfield, 1987). With
‘two-year-down’ growing, foliar fungal diseases generally become a problem in the
second year, so first- and second-year narcissus crops should not be planted adjacent
to each other (Melville, 1980).
At least four years should elapse between growing narcissus in a rotation, or
six years where stem nematode has been found. In sandy soils, deep ploughing