Effects of nitrogen fertilization and plant spacing of early swedes (Brassica napus rapifera Metzg.) under plastic [root cracking]

agricultural chemicals agronomic characters calidad composition contenido de materia seca crops cruciferas forrajeras cultivation cultivo cultivo protegido cultivos culture sous abri dry matter content economic plants engrais escandinavia espacement espaciamiento europa europe feed crops feed crucifers feed roots fertilizantes nitrogenados fertilizers hortalizas (plantas) inorganic compounds methode methods nitrate nitrates nitratos nitrogen fertilizers noruega norway plantas plantas forrajeras plante plante de culture plante racine plants pratique culturale productividad productivity produit agrochimique profitability protected cultivation protection quality rendement rendimiento rentabilidad root crops root vegetables rutabaga rutabagas sales salts scandinavia scandinavie sel spacing vegetable crops weather control yields