368 Handbook of herbs and spices
Effect of nutrition on chemical composition
Compost is widely used to increase soil fertility, usually practised by incorporating the
compost into the upper soil layer. This study questions the rationale behind this practice.
Compost was applied as a mulch and compared with compost worked into the soil in
a growth experiment with leek (‘Siegfried Frost’). Each of the eight combinations of
variables (application method, compost type, and soil type) was repeated three times
with 20 leeks in each replicate. Significantly higher yields were obtained with compost
applied as a mulch. Here, the yield averaged 78 g fresh weight per leek, compared to
59 g per leek from plots with compost incorporated. Compost mulching also resulted
in significantly higher-quality leeks, including more first-class leeks, longer and
thicker shafts, and a generally better appearance. The advantage of placing the compost
on the soil surface rather than thoroughly mixing it with the soil can be attributed to
a higher availability of plant nutrients (Reeh and Jensen 2002).
Staugaitis and Viskelis (2001) investigated the effects of N rates (0, 60, 120, 180,
240 and 340 kg/ha) on the yield, quality and storability of leek cultivars Rival and
Pandora in 1996–99 at the Lithuanian Institute of Horticulture. N fertilizers increased
the above ground mass of leek and marketable yield. N at 300 kg/ha increased the
biomass by 2.2 times and marketable yield by 1.8 times, and yield was over 40 t/ha
in all years. Leek yield increased with increasing N rate, and the yield in the control
increased only by 1–2 t/ha. N increased the contents of N, K and nitrates, and reduced
the contents of sugars, vitamin C (ascorbic acid), dry soluble compounds and dry
matter. The best storability was obtained with N at 180 kg/ha. N content at 180 kg
N/ha was 158 kg/ha, while that at 300 kg N/ha was 193 kg/ha. Analysis of N balance
showed that it is optimum to use 180 kg N/ha. About 30% of accumulated N stays in
the crop residue. At 180 and 240 kg N/ha, approximately 50 kg N/ha was left with the
plant residues. The effects of N were similar in both cultivars.
Brunsgaard et al. (1997) compared the effect of a range of N levels on leek quality
in dietary experiments with rats. Protein content increased with N applications, while
during the autumn the protein content tended to fall; the total biological food value
rose over time from September to November. In a three-year study where leeks
received N at 100, 200 or 300 kg/ha, P 2 O 5 at 70, 140 or 210 kg/ha and K 2 O at 140,
240 or 360 kg/ha applied in various proportions before and after planting, it was
found that in years with high rainfall the optimum results were obtained with high N,
medium P 2 O 5 and low K 2 O rates, whereas in years with low rainfall the best results
were obtained with the lowest rate of all three nutrients. N and P reduced leek
vitamin C content whereas K increased it. The leek sugar content rose with rising
NPK rates. Increasing the number of top dressings augmented the vitamin C content
but reduced that of sugar (Kolota 1973).
Bloem et al. (2004) reported that onion (Allium cepa) and garlic (Allium sativum)
were among the earliest cultivated crops and have been popular in folk medicine for
centuries. Alliins (cysteine sulfoxides) are the characteristic sulfur (S) containing
secondary metabolites of Allium species like onions, shallot, garlic, leek and chives
and they have taste and sharpness that are criteria for pharmaceutical quality. The
influence of the S nutritional status on the content of secondary S containing metabolites
was shown for different Allium species. It was the aim of this study to investigate the
influence of the S and nitrogen (N) supply on the alliin content of onion cv. Stuttgarter
Riese and garlic cv. Thermidrome and to evaluate the significance for crop quality. In
a greenhouse experiment, three levels of N and S were applied in factorial combinations
of 0, 50 and 250 mg S pot–1 and 250, 500 and 1000 mg N pot–1. Eight plants were