Optimisation de l’efficience de l’azote dans des rotations intégrant les cultures de légumes industriels en Hesbaye

Management of nitrogen fertilization in cropping systems including industrial vegetable crops in Belgian loam soil

Context

Belgium is the first exporter of frozen vegetables for the European Union with 800 000 t exported in 2002 (source : Unilet, July 2003). In Wallonia, cropped area wih industrial vegetables (French and broad bean, spinach, pea, carrot, Brussel sprouts) have notably developed around the frozen industry Hesbaye Frost s.a. (Ardovries Corporation). In Hesbaye, which is classified as vulnerable area (Nitrate Directive C.E., 1991), the succession of two vegetable crops on a field within the same season and their integration into classical cropping systems with cereals, sugar beat or potato arises new questions. Indeed, high nitrogen needs and superficial root system of some vegetables (spinach for instance) limit their potential to take nitrogen in deep soil profile and lead to apply nitrogen in excess. For other vegetables, characterized by a long growing period (pea or some sprouts for instance), high amounts of nitrogen rich plant residues return to the soil. The major problem in industrial vegetable crops is the management of nitrogen fertilization in order to limit soil nitrogen residues without hampering yield and quality. The research of adapted solutions to this constraints is keeping with the quality channel (Perfect Chart) developed by the consultancy association “Centre Maraîcher de Hesbaye” (C.M.H.) and the growers association Apligeer.

Objectives

This research was developed in regard with problems pointed out by the European concerted action ENVEG (1998-2000) about nitrogen fertilization of vegetables on the one hand, and on the other hand by the industry and the CMH in Belgium. So, in cropping systems including vegetables such as spinach, pea or French bean, researches have concerned three majors axes: 1) Management of nitrogen fertilization of industrial vegetable crops The objective is to limit nitrogen losses to the environment, while ensuring a sufficient optimal yield and quality production. To reach it, we work with the French nitrogen fertilizer recommendation software AZOBIL (Meynard et al., 1996) 2) Environmental impact of vegetable crops during the intercropping period Nitrogen mineral soil profiles were measured from harvest time to spring either under winter crop (cereal), catch crops or with a bare soil in order to manage nitrogen fertilization at cropping system scale. 3) Effect of vegetable crops on subsequent main crops The implications of these industrial vegetable crops on the nitrogen fertilization of subsequent main crops (cereal, sugar beat, potato) are assessed in order to allow maximum valorisation of these supplies in the cropping system.

Results obtained

Management of nitrogen fertilization of industrial vegetable crops This study have allowed a better knowledge of growing phases of spinach and French bean (main crops studied). Results show that spinach is very sensitive to nitrogen: the yield, the nitrogen content and the nitrate concentration in the canopy are proportional to the nitrogen rate applied. AZOBIL recommendation gives satisfaction in terms of yield, quality production and environmental protection (limitation of post harvest soil mineral nitrogen). On the other hand, the splitting of nitrogen rates into two applications without the use of diagnostic tools for the appreciation of plant nitrogen status (measure of plant chlorophyll content and of light reflectance of the canopy) don’t give better results than those obtain with the one application at sowing date. Environmental impact of vegetable crops during the intercropping draining period and effect of vegetable crops on subsequent main crops Catch crops were installed during the draining period before spring crops (sugar beat or potato). Sowing of Phacelia and mustard up to the 15th of September induce a good save of soil mineral nitrogen from autumnal-winter leaching (more than 50 kg N/ha on 60 cm depth). For latter sowing, ray-grass and rye especially must be advice. The growing phases of the spring crop must also be considered when choosing a catch crop in order to avoid a gap with the mineralization kinetic that make nitrate available for the crop (tuber growing phase for potato or sugar accumulation for sugar beat for example). In all the cases, catch crops are a good alternative to avoid leaching. Winter wheat allows to considerably decrease soil mineral nitrogen content coming from previous vegetable crops and then is interesting at environmental point of view. In term of yield potential, the effect of vegetable crops on a subsequent cereal is almost measured on its grain protein content which is essential for its quality.

Partners

- Centre Maraîcher de Hesbaye - Hesbaye Frost s.a. - Apligeer (Growers association)

CRAW off coordinator

GOFFART Jean-Pierre Attaché scientifique Rue du Bordia, 4 B-5030 Gembloux goffart@cra.wallonie.be Tél : 00 32 (0) 81 62 50 04 Fax : 00 32 (0) 81 61 41 52 RENARD Sophie Attachée scientifique Rue du Bordia, 4 B-5030 Gembloux renard@cra.wallonie.be Tél : 00 32 (0) 81 62 50 07 Fax : 00 32 (0) 81 61 41 52