Complete: Plant populations and N rate

Timescale: 2011 - 2013
Project Lead: E Burks, C Walters and G Milford
Project Sponsor: BBRO

Project Summary

Assessment of the impact of increased plant populations and N rates on high-fertility soils

Main Objectives

In his recent address to the BBRO 2013 Grower Conference, Robert Olssen of Nordic Beet Research made the point that grower generated knowledge is often ahead of R & D advice. There are indications many UK growers are adapting these generally-recommended plant populations to their own particular circumstances. Recent British Sugar surveys of grower practice, for instance, show that, whereas many growers on sand, loamy sand, and sandy and clay loam soils may achieve their maximum yield with 80-100,000 plants/ha, many growers on fertile silt and fen-peat soils are obtaining increasingly greater yields with plant populations beyond 120-140,000/ha.

Outcomes / Key Message For Growers And Industry

The current recommended populations for sugar beet are based on experiments done in the 1970s, 1980s and early 1990s. Few of these tested populations above 120,000 plants/ha, and even fewer tested whether high plant densities require extra nitrogen. However, many commercial sugar-beet growers on those on fertile soils (many in France but some in the UK) claim yield gains from higher than recommended populations supplemented with extra N. 

The results of the single experiment reported here support this grower-driven approach.  The experiment was not as clear cut as intended - illustrating the risk of relying on single experiments to produce clear-cut decisions on agronomic practice. Even so, we were able to show that extra yield could be obtained from high-yielding crops on fertile silt soils by establishing more than 125,000 plants/ha and supplying them with an extra 50 kg N/ha. The response to increased plant numbers in this trial are in line with those of the previous 2010 BBRO seed rate and spatial arrangement trial[1]. Obviously, more trials are needed to confirm the findings of this initial trial.

Recent British Sugar grower surveys indicate ample opportunities for using higher than recommended seed rates and extra N on some of the UK’s more fertile sugar-beet soils. For example, although over 60% of sugar-beet growers on silt soils succeed in establishing the recommended populations of 85-100,000 plants/ha, very few establish populations greater than 125,000 plants/ha (Fig. 1) or apply extra N.

There are also reasons to believe the crops grown use of some of the organic soils might benefit from much higher plant densities with the aim of constraining shoot growth and shifting the partitioning of dry matter more toward the root. However, Crops grown on N-rich organic soils will not require any extra N.


[1] BBRO 10/04: Seed rates and optimal spatial arrangement of seeds for maximum yield and profitability. Final report, May 2011.


Share on
BBRO is a not for profit making company.
We are set up jointly by British Sugar plc and the National Farmers' Union.

British Sugar
National Farmers' Union