Fodder Beet and Sugar Beet
N advice for fodder beet and sugar beet is shown in Table 1. Note that in higher summer rainfall areas, more N is required to achieve optimum yields.
|Table 1: N for fodder beet and sugar beet, subject to different rainfall amounts1 (kg/ha)|
|Rainfall (mm) April - June|
|1. For late-sown crops, reduce N by 20% if sown after April|
Phosporous, Potassium, Magnesium and Boron
The P, K, Mg and B nutrient and trace element advice for fodder beet are given in the soil index system and the accompanying footnotes. Although uptake of P by fodder beet and sugar beet is low compared with N and K, fertiliser P inputs are important because of high response by the beet crop.
Table 2 relates to non-K fixing soils of average clay content with adjustments for K-fixing and clayey soils. Beet has a high K requirement, in common with other carbohydrate-producing root crops. Although Na can substitute for K, it cannot completely replace the K requirement. There is no detrimental effect from using Na at levels found in beet compounds.
Where the soil test for Mg is 25 mg/l or less (see Table 4-6), a response to Mg application is possible, although there is very little experimental evidence for such a response. Magnesium limestone should be used when lime is required on soils of Mg indices 1 or 2.
|Table 2: P and K recommendations for fodder beet and sugar beet (kg/ha)|
|Soil P,K, Mg Index3||P||K + Na||Mg|
|1. Add 70kg/ha K for K fixing Athy soils series.|
|2.Subtract 50kg/ha for micaceous, clayish east Cork soils|
|3. Where soil P test is above 15mg/l, no fertiliser is necessary.|
A response to S has been observed on sandy loam. This element is included in beet compounds. If not included it should be supplied at 20 kg/ha on S responsive soils.
Boron leaches readily from all soils. This effect is severe in light sandy soils and less so in heavy soils but B application is generally necessary for all beet crops and especially for sugar beet. Boron uptake is severely restricted during periods of drought in all soil types. Thus, even when soil concentrations are above the critical level, B deficiency can still occur in sensitive crops. Where deficiency is likely to occur, a source of B may be included in the fertiliser to supply 3.0 kg/ha of B. Where the soil test results are less than 1 mg/l B, it may be worthwhile to supplement the soil application with one or more foliar sprays.
Easily Reducible Maganese
Manganese deficiency (speckled yellows) can occur in beet when the pH is above 7.0 but is more likely at pH above 7.5. However, it has been recorded at pH 6.5 or lower in peats and dark soils with high organic matter content.
Manganese deficiency is controlled effectively by the application of foliar sprays of Mn compounds, e.g. manganese sulphate, Mn-chelate or inorganic formulations. The incorporation of manganese oxide in the seed pellet has proved very successful in preventing early deficiency. It works best when supplemented by a foliar spray at the 4-leaf stage.