THE ROLE OF N FERTILIZATION IN RELATION TO THE KEEPING QUALITY OF ONION

In the first place I must say, that we have had some very nice experiments, in co-operation with Dr Preters of the famous Fertilizing Institute at Harm /near Gromingen/ in Holland.

In the second place I must tell you, that I got the graphes just before departure from the Netherlands. As, it is quiete impossible to inform myself more in details from here, I can only tell you about our work, what I remember myself.

During the growing seasons in 1978/79 80/81 and 82 we had totally 37 field-experiments, spread over different onions-areas in the Netherlands. The main scope was to know, if it is possible to opply nitrogen-fertilizer for onions, on the base of the quantity of mineral-nitrogen, as found by means of soil-analysis.

First of all we found, that there is a very, very great variation in the quantity of mineralized nitrogen in the soil/up to 90 cm deep/ in all those years in different places.

This variation has been:	1978	17 – 167	kg min N/ha
	1979	45 – 139	"
	1980	53 – 162	"
	1981	36 – 127	"
	1982	36 – 194	"

We used the following doses of nitrogen during the years after zero, respectively 50–100–150 and 200 kg N/ha.

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