2007/07/01 by Sean M. Westerveld, Sean M Westerveld, Mary Ruth McDonald +2 · 1 citation
Agricultural and Biological Sciences · #Agriculture, Plant Science, Crop Management #Garlic and Onion Studies #Plant Physiology and Cultivation Studies
paper · pdf · doi:10.4141/p06-159
crossref issued 2007/07/01 · crossref published 2007/07/01 · crossref published-print 2007/07/01 · openalex publication_date 2007/07/01 · crossref created 2011/04/24 · crossref deposited 2020/01/05 · openalex created_date 2025/10/10 · openalex updated_date 2026/06/26 · crossref indexed 2026/07/29
A timeline of nitrogen (N) dynamics of the carrot crop was developed based on studies on the effects of N application on carrot growth, N uptake and partitioning, and interactions with Alternaria [ALB; A. dauci (Kühn) Groves and Skolko] and Cercospora [CLB; C. carotae (Pass.) Solheim] leaf blight. Preplant-applied fertilizer N affects yield only when residual N in the top 60 cm of the soil profile is insufficient. The majority of the N required by the crop is taken up beyond 50 d after seeding (DAS). Carrots have a root system that extends to 150-cm depth and >50% of the fibrous root system occurs below 30-cm depth. It is likely that N below 30 cm depth is required beyond 50 DAS, since the majority of the fibrous roots are below 30 cm depth after that stage. There is insufficient time for sidedressed N to leach into the active root system beyond 50 DAS, unless its application is timed before irrigation or rain events. Regardless of the amount of residual N, preplant-applied N is essential for minimizing leaf blight severity. It is possible that leaf blight defences are conferred upon leaf emergence and may benefit from abundant N at this time. A preplant soil nitrate-N test from both the top 30 cm and the 30- to 60-cm depth could be useful for determining residual N levels and for adjusting N fertilizer application rates accordingly. Key words: Daucus carota, Alternaria leaf blight, Cercospora leaf blight, nitrogen uptake, rooting depth, fertilization