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Magnesium-fertiliser had no effect on yields although leaf analyses indicated levels lower than recommended (average of four trials). In one trial, sugar content increased significantly.
Manganese-fertiliser had no effect on yields although leaf analyses indicated levels lower than recommended (one trial harvested).
Boron-fertiliser had no effect on leaf content, which in all cases (in contradiction to previous results) was above the recommended level (two fields investigated).
General, there was no obvious differences between the tested techniques when recommended N-levels were In applied and tillage could compensate for compaction caused by self-propelled slurry wagon.
Drilling directly on ridges made in the autumn was most suitable when drilling was performed well in advance of the optimal time for the specific field. Due to dissatisfactory plant emergence – especially when drilling later – this method is not advisable in its tested form.
Autumn drilling resulted in the best yields, when drilling was performed close to the optimal day for the field, whereas deep-harrowing gave the best yields when drilling was delayed beyond the optimal day.
Please confer to NBR-report 729 for a praxis-near comparison of ploughing and deep-harrowing.
Rust has been the dominant leaf disease in three field trials performed in 2020, where powdery mildew has developed 1-2 weeks later than usual. One trial has been inoculated with Ramularia. Two treatments with 0.5 liter Opera per ha have resulted in 15 pct. yield increase in relation to untreated, and net approx. DKK 2,000 per ha. Opera may no longer be sold and may only be used and stored until October 30, 2021. Amistar Gold as well as the new and unapproved products Propulse and Balaya have resulted in sugar yield and net excess no higher than Opera.
In two trials, three products, Kumulus S, Armicarb SP and Serenade ASO, are tested for their effect on leaf diseases as possible solutions for organic sugar beet cultivation. Kumulus S shows effect against powdery mildew and 5-7 pct. additional yield, which gives a positive net contribution for four treatments with 3.5 kg per. ha. Armicarb 85 SP and Serenade ASO show weak effects against powdery mildew and rust. Serenade ASO has in 2020 resulted in a small net profit, but this is not seen in an average of four trials in two years.
Rust has been the dominant leaf disease in 2020. The attacks began in late July and with a relatively weak development until mid-August, after which the attacks increased until harvest. Powdery mildew attacks have begun 1-2 weeks later than rust, and the attacks have been relatively weak. The attacks of Ramularia have been very weak. Cercospora has been less widespread than in 2019, but more widespread than in previous years.
In the leaf disease warning service, 20 fields have weekly been monitored for infestations in a number of varieties. The first attacks of rust have been seen week 30 (July 20-26), and treatments was recommended in fields with incipient attacks. Where first treatment has been performed in week 31 and where harvest has been planned for after mid-October, a follow-up treatment in week 34 has been recommended, where fresh rust pustules could be seen. For fields with lifting later than mid-November, a 3rd treatment could possibly be followed up 3-4 weeks later.
Fungicide seed treatments with Tachigaren and Vibrance SB has been studied in four field trials. The attacks have been more serious than in previous years’ trials – thus an average of 16% of the plants in untreated are attacked by damping off, which has caused plant losses. In 2020, there have been no additional yield in the treated entries. Several years of trial results with Tachigaren show reduction in damping off and higher final plant numbers. Variable yield increase has been obtained with a tendency of 1 per cent increase in average.
Two field trials were carried out to test different fungicide strategies to control powdery mildew (Erysiphe beta) and to minimize fungicide resistance. The treatments included registered products as well as new products including Propulse and Revysol in combination with Comet Pro. Serenade ASO and Kumulus S were also included as alternative products. All fungicide treatments controlled powdery mildew effectively. Kumulus S reduced powdery mildew significantly and comparable to the fungicide solutions. Serenade ASO showed only a low effect on powdery mildew.
Powdery mildew samples from Denmark and Sweden were tested for strobilurin resistance in 2020. Two samples from Denmark and two samples from Sweden were tested positive for strobilurin resistance in a trial under semi-controlled conditions. All four samples harbored point mutation G143A, which has been associated with strobilurin resistance.
In a field trial with sugar beets with attack of thrips, seed treatment with Gaucho WS 70 (60 g imidacloprid) indicate a yield increase of 6 per cent. No yield increase is obtained with seed treatment with Force 20 CS (10 g tefluthrin). In another field trial with precrop beets (to provoke insect pressure) and infestation of pygmy mangold beetles, approx. 35 pct. yield increase is obtained with seed treatments with Gaucho WS 70 and Force 20 CS. Additional insecticide applications against thrips and pygmy mango beetles have not significantly increased sugar yield. In both trials, there have been weak infestations of peach potato aphids (Myzus persicae), but no occurrence of virus yellows has been observed. Effect of Pirimor 500 WG, Teppeki and Movento SC 100 against peach aphids is indicated. Effect of Karate 2.5 WG against peach aphids is indicated to be very low.
In three field trials, weed control strategies are investigated. Strategies without Betanal and Betanal Power have resulted in 8-9 pct. weed coverage whereas 2-4 pct. coverage is obtained with Betanal and Betanal Power treatments. The differences have not produced any clear yield differences. Betanal Power replaced with Betanal has indicated comparable effects. Nortron is indicated to most effective when incorporating the product from timing T2 in these trials – which is mainly because of few late germinating species. There are minor differences between the tested doses of Nortron – with a tendency of dose/response. The results indicate slightly better effect of Centium (less plants per m2), where it is applied post emergence compared to Centium applies pre-emergence. The best effect of Centium is reach where Centium is used both pre-, and post-emergent.
Herbicide strategies to control volunteer oil seed rape have been studied. There is a tendency in the trial that the strategies with Centium before emergence have had an improved effect against the dominant weed species (rapeseed (BRSNN), black bindweed (POLCO) and cleavers (GALAP)) in this year’s experiment – which was not evident in the 2018 and 2019 results.
Herbicide treatment strategies in and between the rows in combination with hoeing are studied. The base is a standard strategy in the rows with two times hoeing which is then compared with different herbicide strategies between the rows with Centium, Boxer, and Proman.
The weed control in the rows has been effective and there is no clear difference between the different entries.
Between the rows, the plots that have received an early hoeing have had a weed cover on a level with standard practice, except for cleavers (GALAP), which have not been controlled at an acceptable level.
There is a tendency for the entries treated with Boxer and Proman to have an effect over untreated, but not on a par with standard practice or the early hoeing.
Ploughing prior to sugar beets – in fields that normally were not ploughed – resulted in yields that on a four-year average were three percent higher (not statistically significant).
Delayed drilling (false seed bed) markedly reduced the amount of weed (measured as weed left in the field in July when hoeing was finalized).
Weed burning just before emergence of beets approximately halved the amount of weed when drilling was not delayed whereas burning had less or no effect when used in combination with delayed drilling.
The results from this and recent years will be compiled into an organic sugar-beet-growing guide.
Hoeing with combined hilling had the best effects against weed in this comparison of more mechanical-based weed control methods.
Correct timing and adjustment of equipment is essential in al mechanical weed control and may have influenced the results.
The was no significant yield effect between the methods when weeds were chemically controlled until the four-leaf stage.
Hoeing with hilling had a negative effect on sugar content (0.2 points) and cleanness (0.7 point).
In all year, placement of organic fertilisers at drilling resulted in increased yields. Yield increases differ between trials, years and placement methodology. Generally best results have been obtained with liquid fertilisers or solids fertilisers when applied 1-2 weeks (placed with GPS) prior to drilling. In 2020, there was, however, no difference between liquid and solid fertiliser and less effect of placing pelleted hen manure prior to drilling.
Use of organic fertiliser can be technically challenging due to high application rates. Equipment for organic fertiliser is less common and cannot handle some liquid fertiliser.
When choosing sugar beet varieties, the most important parameter is yield capacity. Comparing varieties there is a large variation in terms of yield and revenue. This year 81 varieties were tested in six yield trials for the recommended list of Danmark. The variety Cascara KWS is the market variety with the best economy at +951 DKK per hectare compared to the average of all marketed varieties. It was followed by the marketed varieties: Fenja KWS, Falster, Nasser, Daphna, Selma KWS and Skelby. The difference between varieties in the trials this year is from +951 to -2.650 DKK per hectare.
This year in total eight ALS-tolerant candidates from two seed companies were tested. The yield level was significantly lower compared to the market segment without this trait.