NITROGEN-FERTILIZER RECOMMENDATIONS FOR GLADIOLUS BASED ON N-MINERAL SOIL ANALYSIS

N.P.A. Groen, J.H.G. Slangen
In bulb production of gladiolus in the open the advice for nitrogen nutrition was, until recently, based upon practical experience and some information from (field) tests, but not on analysis of soil samples. Some years ago the Nitrogen-mineral (N-min) method was developed, which today is used by the Laboratory for Soil and Crop Research in Oosterbeek (The Netherlands) for their advice for nitrogen dressing. The N-min analysis is related to the nitrate (NO3-) and ammonium (NH4+) contents of the soil. Routinely the root layer of 0–60 or 0–30 cm is sampled.

The assessment of the nitrogen content thus measured denotes how much nitrogen is available to the plant for immediate uptake and consequently how much must be added to reach the optimum dose of nitrogen for the plant. We investigated how much nitrogen was absorbed by parts of gladioli both above-ground and underground under growth conditions in the Netherlands.

On the basis of the available supply of nitrogen in the soil, the amount of nitrogen to be absorbed in the coming month, and taking into account a quantity of nitrogen as 'fixed supply', the monthly amount of nitrogen to be added can be calculated.

A more exact specification of the amount of nitrogen to be added is desirable, because too much nitrogen may increase the risk of infestation by Fusarium in gladioli. Moreover, dressing at a time when no nitrogen is taken up by the plant will result in losses, mostly by leaching of NO3-, which are undesirable from a point of view of environmental protection. Using the above-described method the N-min. in the soil is measured at regular times and consequently the nitrogen released from the organic material is to some extent taken into account in the advice. This is important especially if, as practised in the Netherlands, large quantities of liquid manure are used before cropping or in previous years.

In Germany the system has been worked out also and has been applied with reasonable success for vegetables in the open. The method can be adapted for other tuberous plants and bulbs by determining the pattern of absorption of nitrogen and other nutrients.

Groen, N.P.A. and Slangen, J.H.G. (1990). NITROGEN-FERTILIZER RECOMMENDATIONS FOR GLADIOLUS BASED ON N-MINERAL SOIL ANALYSIS. Acta Hortic. 266, 375-380
DOI: 10.17660/ActaHortic.1990.266.49
https://doi.org/10.17660/ActaHortic.1990.266.49

Acta Horticulturae