N-Immobilisierung in Holzfasersubstraten bei der Anzucht von Tomatenjungpflanzen (Lycopersicon lycopersicum (L.) Karst, ex Farw.)

Abstract

N-immobilization of wood fiber substrates during production of vegetable transplants was studied in greenhouse and under phytotron conditions. Tomato transplants were grown on white peat, unimpregnated and impregnated wood fiber with three N-levels respectively. N-immobilization was calculated on the basis of N-balance including N-uptake by plants and residual mineral N in the substrates. In addition, the influence on net photosynthesis rate was examined. Higher N-immobilization was found by increasing of N-application rates. Net-N-immobilization in impregnated wood fiber substrates was comparable to white peat with 100 mg N l -1 . Tomato transplants, cultivated on impregnated wood fiber substrates, showed significantly higher growth compared to plants cultivated in unimpregnated wood fibers. With additional N-fertilization (level N3) the significance of N-immobilization in impregnated wood fiber substrates for the growth of tomato plants could be neglected. However, general recommendations for the amount of fertilizer to be added are difficult, because of strongly varying contents of mineral nutrients in the different substrate loads. Nevertheless, it is necessary to supply wood fiber substrates with nutrient solutions or fertilizer from the beginning of plant culture. Substrates without plants, exposed to the same conditions showed the same tendencies in N-immobilization, as substrates with plants.