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Communication Dans Un Congrès Année : 2004

Nitrate accumulation in protected lettuce

Résumé

A series of experiments have been carried out on soil grown protected lettuce to identify the main causes of nitrate accumulation in both summer and winter harvested crops, and to compare the merits of various N fertilizer management practices for minimizing nitrate concentrations in their heads at maturity. The results suggest that nitrate will tend to accumulate in lettuce shoots when the nitrate supply exceeds the N demand of the crop, especially during the summer. It also accumulates when there is a reduction in solar radiation, or when parts of the lettuce head become subjected to shading due to increased canopy density. More nitrate accumulates in winter because: growth rate tends to decline more quickly than nitrate uptake rate; there is less light energy to reduce nitrate into organic forms of N; winter crops appear to use N more effectively for dry matter production; and yields are often lower so relatively more nitrate is available to accumulate in the crop. Despite this, the risk of contravening EU legislation on nitrate can be greater in summer when maximum limits are lower and nitrate concentrations in lettuce heads are more variable. Studies of different management practices showed that winter crops required less N fertilizer than summer crops because of their slower growth, more effective utilization of N in their tissues and lower final yield. The type of N fertilizer had no effect on marketable head weight, provided it was applied according to crop requirement. Use of slow release fertilizers, nitrification inhibitors or organic fertilizers to restrict availability of nitrate in the soil reduced nitrate concentrations in the heads in the short term, but subsequent release of nitrate increased its accumulation in following crops. Splitting applications of nitrate fertilizer between a base dressing and liquid feeds did not affect yield, but any application of N within about 14 days of harvest tended to increase nitrate concentrations in the crop at maturity. The implications of these observations for the UK protected lettuce industry are discussed.
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Dates et versions

hal-01279335 , version 1 (25-02-2016)

Identifiants

  • HAL Id : hal-01279335 , version 1
  • PRODINRA : 202619
  • WOS : 000222371800033

Citer

I.G. Burns, A. Lee, Abraham Escobar Gutiérrez. Nitrate accumulation in protected lettuce. 26. International Horticultural Congress, Aug 2002, Toronta, Canada. ⟨hal-01279335⟩
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