Agronomic principles in sugar beet production

The sugar content in the beet has to be high and the content of amino-N in the juice has to be low.

Sugar beet is a biennial crop so the yield is determined by the amount of radiation captured in the first year of its growth. It is therefore critical to have this in mind when developing the agronomy strategy. Such a strategy should ensure rapid, early establishment, reducing the time from emergence to full canopy closure, and maximising the time between full canopy closure and senescence. Such a strategy will ensure 90% intercepted radiation and therefore maximum yield. There are a large number of agronomic factors which can influence this, many are within the control of the grower, under given climatic and soil conditions. Seedbed preparation, seed quality, seedling emergence, plant growth, row spacing are all important factors.

Seedbed

Seedbed preparation aims to create a layer of loose dirt, where the seed is placed below on a firm layer of soil with a good structure to depth. This structure ensures the flow of nutrients, air and moisture to the germinating seed. Sowing should be made the first time the soil is workable. Delaying the sowing to the beginning of April can reduce the yield by 0.5% / day due to the later development of the beet giving a reduced amount of leaf cover later in periods with high radiation. Damaging the soil structure should always be avoided, so do not traffic soils when they are wet.

Soil and pH

Sugar beet is very sensitive to pH in the soil and will only produce a high yield when grown in soil with a neutral to high pH. The pH depends on the soil type:

• sandy loam to clay soils the pH has to be 6.5 to 7
• sandy soils the preferred pH is 5.5 – 6.0
• soils high in organic matter the preferred pH is 6.2.

As shown in the picture below, the level of pH also has an influence on the availability of nutrients. At pH values above 7.5, nutrient availability, especially phosphorus, manganese, boron and zinc, can be reduced even though high total amounts of these nutrients may be present in the soil.

Where soil pH is too high or too low, resulting in a ‘lock-up’ of nutrients (frequently micronutrients) in the soil, foliar application of those nutrients will ensure rapid response in the sugar beet and prevent growth from being restricted. Especially boron and manganese can at high levels of pH be unavailable in the soil.

Crop protection

Sugar beet is a poor competitor to weeds, especially from emergence and until canopy closure. Emerging sugar beet plants are small, lack vigour and will take approximately two months to shade the ground. In this time it is very important to keep the beet free of weed. 3-4 applications of herbicide is often necessary. Competition from weeds will give slower development of the sugar beet due to competition for light and nutrients. The slower development of the beet means a smaller leaf area in the period where the solar radiation is high.

Crop rotation

Sugar beets can be exposed to root rot (Pythium, Aphanomyces, Phoma). These are soil living fungi which attack the roots. The symptoms are dark / black roots. The risk is reduced with a good crop rotation with three years between the sugar beet crops. Weak plants are more exposed than healthy plants. Other fungi (powdery mildew, rust and Ramularia) can also attack sugar beets. Another massive threat to sugar beet production that makes a proper crop rotation mandatory in most sugar beet producing areas is the attack by soil borne nematodes.

Summary of agronomic principles

• Create a well- structured soil / seedbed to give optimal soil nutrient and water supply.
• Avoid soil compaction and zones of not decomposed crop residues that may hamper root growth.
• Correct pH issues that affect soil nutrient supply.
• Use major and micronutrients (especially nitrogen, potassium, phosphate, manganese, boron and zinc) to promote early, rapid plant growth and development.
• Create a Nutrient Management Plan to address the crop requirements not fulfilled by the soil supply, paying attention to rates and timings during the construction of the canopy.
• Monitor the crop through its development to address any deficiencies that could prevent the duration of the canopy.
• Pay attention to the sugar quality expected by the end user, and manage the crop nutrient program accordingly.
• Use the Yara tools and services to manage the nutrient plan and maximize profitability.