Complete: Seed rates for the new sugar regime

Timescale: 2005 - 2009
Project Lead: Unknown
Project Sponsor: BBRO

Project Summary

The last experiments on the effects of plant population density on the performance of UK sugar-beet crops on which much of our current advice is based were done over 30 years ago (Hull & Jaggard 1971) and last reassessed nearly 20 years ago (Jaggard 1990). The main conclusion was that the optimum plant population density for maximum yield was 65,000 plants/ha on good soils increasing to about 85,000 plants/ha on poor soils. Although yields were not improved at higher than optimal densities, sugar content and beet quality (amino-N, potassium and sodium contents) were improved. Very high densities increased dirt tare. The few experiments done since (primarily those funded by the SBREC and done by British Sugar plc and Broom’s Barn between 1989 and 1996 to examine interactions between variety, spacing and plant population density) largely confirm these basic findings, and show that beet grown at high densities were more uniform in size with fewer harvesting losses (Bee & Jaggard 1996). Other work on crown size and frost physiology shows that high planting densities decrease crown height and beet water content suggesting that such beet should be less susceptible to frost damage (PJ Jarvis, unpublished).

Main Objectives

1. To determine, on the major soil types, the effects of three in-row seed spacings on plant uniformity, yield and beet quality at two seedling establishment percentages on large strip plots to allow the costs and benefits at the commercial scale to be evaluated. 2. To compare, the effects of the same treatments as in Objective 1 on yield and beet quality using 50 and 60 cm rows using standard experimental plots on a sandy soil. 3. To use recent British Sugar plc survey data from commercial fields to determine the distributions of seed rates and plant population densities in commercial sugar-beet fields and thus pinpoint the risks that might arise from any changes to current practice and identify any improvements that may be needed. 4. To combine information from the experimental and survey work to produce new recommendations for the most cost-effective seed spacings for the new sugar regime.

Outcomes / Key Message For Growers And Industry

The 11 experiments in this study have shown that sugar-beet growers should aim to achieve 80,000 plants per hectare. There is no significant yield loss if this target is exceeded when seedling establishment is unexpectedly good, but if populations fall well short of the target there is risk of yield losses on some sites. The soil type and expected level of yield does not affect the target plant population. Dense plant stands had a tendency to have a larger dirt tare than sparse stands, but this difference was not sufficient (seldom more than 1% dirt tare) to shift the target density, especially as some of the soil would fall off the roots during cleaning and loading. Grower’s success or otherwise in achieving an adequate plant population does not seem to be linked to soil texture type, sowing date or seed rate, but is very dependent upon to seedling establishment they are manage to achieve. This is clearly a topic that needs further research to find the causes and solutions to the problem, and this is illustrated by the observation that, despite our best efforts, two of our trials failed through poor establishment. Staff from Broom’s Barn and British Sugar will jointly investigate possible approaches to this research and produce a proposal for consideration in 2010.

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We are set up jointly by British Sugar plc and the National Farmers' Union.

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