YIELD AND NITROGEN UPTAKE OF BROCCOLI AND SOIL NITRATE STATUS AS INFLUENCED BY RATE AND TIMING OF NITROGEN APPLICATION

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  • 1 Dept. of Horticulture, Virginia Tech, Blacksburg, VA 24061

A Preliminary study conducted in 1985 indicated no significant yield response to 8 treatments ranging in amount of total N applied from 56 to 290 kg N/ha. Treatments in 1986 were as follows: base rate N at 0, 56, 112, and 168 kg N/ha with 0, 1, or 2 sidedressings at 56 kg N/ha each applied at 3 and 6 wks after seeding. Yield differences for base rate n were significant at the first harvest only, while sidedressing effects on yield were significantly different for 3 of the 4 harvests and total yield. Nitrogen uptake during the first 32 days after seeding (DAS) was minimal, 0.17 kg N/ha/day, but increased to 8.05 kg N/ha/day during head formation (55 to 77 DAS). Initial soil nitrate status was high in the top 25 cm (52 kg N3O /ha) but decreased to 10.6 kg NO3/ha in the control plot by the end of the season. Sidedressings, prior to and during head formation, are recommended to maintain an adequate available N supply throughout the growing season.

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