Interaction of Nitrogen Fertility and Plant Populations on Transplanted Broccoli and Cauliflower Yields

As broccoli populations increased from 24,000 to 72,000 plants/ha at N rates of 112, 168, or 224 kg/ha, head weight decreased linearly. Increasing the N rate from 56 to 224 kg/ha at any population linearly increased broccoli head weight and marketable yields, and decreased cull yields. Broccoli yields were highest at 72,000 plants/ha and 224 kg N/ha. No marketable cauliflower curds were produced at 56 kg N/ha at any population evaluated. As populations increased from 24,000 to 72,000 plants/ha with N rates held constant at either 112 or 224 kg/ha, marketable curd weight decreased linearly and cull production increased linearly. Increasing the N rate from 112 to 224 kg/ha did not increase marketable curd weight or yields at any population. Increasing the N rate to 112 kg/ha or higher reduced cull production at 24,000 plants/ha, but not at populations of 36,000 or higher. Cauliflower yields were optimized at 24,000 plants/ha and 112 kg N/ha based on reduced cull production, satisfactory curd weights, and transplant economy.