Nitrogen Nutrition Effects on Nitrate Accumulation of Soil‐Grown Greenhouse Butterhead Lettuce

Abstract

Leafy vegetables are the major source of dietary nitrate intake of humans. Nitrates can have many detrimental effects on human health besides some beneficial effects. A further reduction in nitrate concentration thus can represent added value for vegetable products rich in carotenoids, vitamins C and E, selenium, dietary fiber, plant sterols, and so on. Though nitrate accumulation is governed by a plenitude of factors (i.e., genetic setup, environmental conditions and nutrients), the factor most readily controllable is nitrogen nutrition. This study examined the dependence of butterhead lettuce crops' nitrate concentration on soil mineral nitrogen (N) content. It was shown that the effect of the soil's mineral N content at harvest was strongly associated with the nitrate concentration of lettuce at a low to intermediate mineral N content (,100 kg N ha 21 ). This demonstrates the importance of N-fertilization practices. Results of 24 comparative experiments, based on two different N-fertilization recommendation procedures, did show that an N application difference at the start of the growing period has an effect on the nitrate concentration at harvest. A lower N application at either recommendation resulted in 71% of the experiments (17/24) having a lower leaf nitrate concentration. The head weight was negatively affected in only 2 of these 17 experiments. Minimizing the N input and hence lowering the soil N content at harvest points to the possibility of further reducing the nitrate concentration level in greenhouse lettuce, while having no significant negative effect on economic yield.

Effect of organic compost and inorganic nitrogen fertigation on spinach growth, phytochemical accumulation and antioxidant activity

“…Despite vitamin C being influenced by nitrogen fertilization ( Lee and Kader, 2000 ; Salomez and Hofman, 2009 ), spinach leaf-blade and petiole AsA were not affected by the treatments ( Figure 2 A). This may be related to the fact that the response of AsA to nitrogen may be not linear and/or vary with the cultivar.…”

Screening for genotype and environment effects on nitrate accumulation in 24 species of young lettuce

“…Although more recent work has shown that these potential health concerns were somewhat exaggerated,7, 17, 18 the EU legislation remains in place (albeit with a proposed minor relaxation of some of the limits), and is likely to be extended to include other salad crops such as rocket (rucola; Eruca sativa L.) in the near future 19. Since the legislation was introduced, some progress has been made in improving cultural practices (including better management of the N supply) to reduce net accumulation of nitrate in protected lettuce crops 20–22. However, options are limited for growers in many northern European countries, particularly in wintertime when the light quality in their glasshouses is poor, because nitrate accumulation under these conditions is only weakly dependent on N supply 21, 23, 24.…”

Agronomic, physiological and quality response of romaine and red oak-leaf lettuce to nitrogen input

“…Nitrogen demand in lettuce crops is particularly high in the last third of the growing cycle, and sub-optimal N supply may lead to N deficiency with consequent yield reduction, poor quality and maturity delay (Salomez and Hofman, 2009). On the other hand, over applications of N, exceeding crop N demand, may cause N luxury consumption with consequent nitrate accumulation (Di , and increase the risks of N losses, causing environmental pollution and contamination of water bodies and drinking water.…”