IMPROVING THE USE OF NITROGEN IN BRASSICA ROTATIONS

Applying the right amount of nitrogen fertiliser to ensure optimum crop yield and quality makes sound economic sense and helps to reduce the levels of potentially leachable nitrogen in the soil.
Current national recommendations allow up to 50 kg/ha N for soil and crop residues from a preceding brassica crop which has received 200 kg/ha N. An experiment was set up in 1988 to examine the nitrogen responses of crops grown in an intensive brassica rotation at various levels of residual soil nitrogen.
The crops grown were early summer followed by autumn cauliflowers in 1988, Brussels sprouts in 1989 and spring barley in 1990.

Maximum yields of high quality produce were obtained with a total of 540 kg/ha N; 300 kg/ha applied to the first cauliflower crop, 120 kg/ha to the second cauliflower cropped, and 120 kg/ha to the Brussels sprouts.
This also gave near maximum yields of spring barley without further N application.
Apart from the first cauliflower crop, these rates were all substantially below the current recommended rates which would have totalled 750 kg/ha N over the 3 years.
Quality and date of harvesting were not significantly affected by the reduced

Workshop on Ecological Aspects of Vegetable Fertilization in Integrated Crop Production in the Field

C.R. Rahn, C.D. Paterson, L.V. Vaidyanathan

https://doi.org/10.17660/ActaHortic.1993.339.18