Late Season Nutrients for Bulb Crops

As the growing season progresses, it feels timely for a reminder on one of the key messages on late season nitrogen application from our fodder beet roadshow earlier this year. 

Dr. Jim Gibbs, highlighted how a late season application of nitrogen to fodder beet crops has shown benefits in frost protection to the leaf, where there is “good leaf to protect”, and to aid the bulb withstanding continuous frost and dethaws. 

Trials in both New Zealand and smaller scale in the UK have shown N rates over the crop growing year at 200kg/ha (including FYM and slurries) have boosted crop yields, where the crop is not constrained agronomically e.g. low pH, weed burden, compacted soils, etc.  This is achieved in the New Zealand system through splitting the N application in to 3-4 applications.  Where a light application would be made at sowing in a blend, and then applications as follows: 

Plants that have poor leaf, or are destined for lifting, the 4th application is not required.  Decisions on applying fertilisers late season, must take the environment into consideration e.g. ground conditions for travelling, waterway protection, NVZ rules, etc. 

For soils that had an application of farmyard manure pre sowing, have the added asset of slow-release Nitrogen through the growing season, which must be taken into consideration, when nutrient planning.  Cattle FYM contains in the region of 6kg N/t, with 10% of this N available to the crop, meaning a 20t FYM application would deliver approx. 12kg N released slowly over the growing season. 

With late season N application showing benefits in fodder beet, of retaining the protein and mineral rich leaf, and aiding frost protection in the bulb, it does highlight the question of late season N on other bulb crops such as swedes.