Increasing the number of sugarbeet seeds that result in established plants could lower variable costs and make sugarbeet production more predictable. But improving emergence by 10% to 20% or more on average under the diverse conditions found in California is difficult to do. To improve stand establishment, some combination of better management of irrigation practice, seed bed preparation, improved planting technology, and greater seed quality (either through culling or seed treatments or both) may be necessary, with required changes varying from farm to farm.

The farmer's stand establishment system as a whole may need to be evaluated. Practices which focus on one management problem like weed control, may adversely affect other goals like rapid and uniform seedling emergence. For example, pre-plant incorporated thiocarbamate herbicides have been shown in our warm weather trials to reduce the number of established seedlings. Water logging of soils, uneven moisture, and excessive salinity can lead to unevenness and disappointing rates of emergence. Uneven seed placement due to rough seed beds or damage to seed by poorly adjusted planters can lead to stand failure even before water is applied. In some locations, insects appear to damage seed and emerging seedlings.

Potential remedies for stand establishment problems exist. Changes in irrigation practice, improved planter maintenance or substitution of improved planter types, changes in tillage and seed bed preparation, improved attention to soil organic matter and soil tilth, and the use of new (but costly) seed treatments like Gaucho® (imidicloprid: an insecticide) and Tachigaren® (hymexazol: a fungicide) are possible. New fungicides are under consideration as seed treatments, and one (amoxystrobilin or Protege®) may offer superior protection against Rhizoctonia compared to current materials, but very little work has been carried out on it elsewhere and none under field conditions in California. Other pre-germination seed treatments like priming increase the rate of emergence and may improve uniformity and final emergence percent. Most seed treatments, however, can have negative as well as positive effects on emergence at times, depending on the treatment and its interactions with the environment in which the seed is placed.

Previous efforts. In 1997, 1998, and 1999, more than twenty stand establishment trials were carried out on research station and farm sites throughout California. Most focused on the perfromance of seed treatments, but some included other factors such as herbicides, irrigation practices, soil amendments, and the effects of salinity. Not all of these trials provided useful data, but all of them increased our understanding of the problems limiting sugarbeet seedling emergence under California's stressful conditions. Summarized briefly, overall results with respect to seed treatments were:

1. There were significant differences among seed treatments in most of the trials. These differences mean that some capacity for improvement in stand establishment is possible based on the use of appropriate seed treatments. Seed treatments using Gaucho® usually performed better than other seed treatments, including the current commercial standard treatment. This suggests that soil insects susceptible to Gaucho® may be damaging sugarbeet stands in many locations.

2. Priming tended to improve emergence, but inappropriate soil moisture conditions may cause primed seeds to fail.

3. The amount of post emergence mortality tended to be more consistent among most seed treatments and in most trials, while pre-emergence mortality varied more widely. Treatments with the highest plant numbers at the four to six leaf stage had the highest cumulative emergence percentage, so any treatment which increases emergence enhances stand more than post-emergence control of seedling losses. Pre-emergence losses are due to a combination of non-viable seed, pathogens, and what appears to be a finite amount of insect damage. Even though post emergence losses to insects appear to be small relative to other causes of mortality, protecting seedlings after emergence can provide an additional 5 % to 15 % more established seedlings on average, perhaps insuring enough seedlings to safely plant to a stand.

4. The sources of post-emergence mortality varied by location, but should be approximately predictable. Commonly, flea beetles and armyworm larvae were observed damaging seedlings.

5. If post-emergence losses can be anticipated quantitatively, and emergence rates increased to approximately 70 % (depending on anticipated post-emergence losses), planting rates can be fine-tuned, and planting to a stand should be feasible. In most of our campus and field station trials, the best seed treatment combinations resulted in 70 % establishment or better. These high rates of establishment also were observed in some field trials. At these rates, planting to a stand is possible, and growers can reduce their costs.

Trials in 2000 were based on previous efforts. One trial at Davis focused on seed treatments; another focused on the effects of pre-irrigation, and a third on the effects of soil amendments.

Objectives:

1. Identify specific environmental and cultural factors causing seeds to fail to germinate and emerge under a variety of sugarbeet production conditions.

2. Conduct field emergence trials to evaluate promising seed treatments under a range of farm conditions.

3. Develop recommendations for the improvement of sugarbeet stand establishment in California.

Procedures:

1. Evaluating new seed protection materials. (May, 1999). New plant protection materials are becoming available including a new, as yet unregistered fungicide (amoxystrobilin) thought to be more effective against Rhizoctonia and Aphanomyces. Amoxystrobilin was compared to currently registered fungicides used in previous trials in an experiment carried out in early May on the Davis campus. The materials used, the rates of application are reported in Tables 1 and 2.

2. Analyzing the effects of farm irrigation practices. At times, seed is planted into dry or moderately moist soil and then can remain for days to longer than a week before irrigation water is applied. Seeds are very hydroscopic, and can absorb water from relatively dry soils. Delayed irrigation may harm seeds, particular primed seeds which need relatively less moisture from surrounding soil to germinate. We evaluated the effects of delayed irrigation on primed and un-primed seed on a site at the Davis campus. A subset of the plots was pre-irrigated, and a second set was not pre-irrigated. Primed and un-primed seed were planted into these plots 14 days, 7 days, and one day before irrigation was applied. The effects on emergence and final stand establishment of different pre-irrigation treatments and planting to irrigation intervals was evaluated. This was the second year of this trial.

3. Evaluating soil amendments. Loam soils in California have a tendency to crust. Sodic soils also can form resistant crusts, but for different reasons. Sugarbeet seeds have less capacity to emerge through crusts than many other agronomic crops. To evaluate the usefulness of soil amendments on emergence, the effects of two different soil amendments (Gypsum and Poly-acrylamide-PAC) were compared to a control treatment using both sprinkler and furrow irrigation methods. Gypsum was applied to the tops of 30 inch beds at two different rates ( 400 and 800 lbs per acre) and PAC at one rate (20 lb per ac) immediately after planting and before irrigation. Both primed and non-primed seed also were compared.

Results and discussion

There was severe armyworm pressure on seedlings throughout the duration of all of three Davis trials in 2000. Post-emergence losses were larger than encountered in previous years. Because the trials are counted daily or every few days (frequent field re-entry), it is not possible to control armyworms using traditional pesticides, so post-emergence losses are exaggerated compared to growers' fields. As a consequence, the most useful information resulting from these trials is emergence data, rather than post-emergence mortality and establishment, particularly in 2000.

Seed treatment comparisons.

Cumulative emergence. Primed seed (PAT) treated with Gaucho, Apron and Thiram emerged at the highest rate. Greater than 70 % of the seed emerged under stressful conditions. This difference was significant (Tables 3, 4). In general emergence was favored by the use of Gaucho (Table 4). Since Gaucho is an insecticide, with no documented effect on plant diseases, we can infer that there is some insect damage occurring to seed and emerging seedlings that is prevented by its use. There was no significant difference between the use of Gaucho at 20 g per unit (100,000 seeds) and 45 g per unit. This has implications for cost savings for growers. The new fungicide (Protégé), had no effect on seedling emergence (Table 4).

Final establishment. Gaucho-treated seeds resulted in better large numbers of established seedlings, though seedling numbers were low due to excessive armyworm predation (Tables 5, 6). No other seed treatments influenced final establishment.

Post-emergence mortality. Large amounts of insect predation on seedlings were observed (Tables 7, 8, 9, 10). For the most part, the amount of loss was proportional to the number of seedlings present, although Gaucho-treated seeds had lower post-emergence mortality on average.

Irrigation practices:

Irrigation and seed treatments interacted (Fig. 1 to 4). Priming increases the moisture potential of seeds and advances metabolic processes associated with germination. It can be thought of as making seeds more sensitive and responsive to soil moisture conditions. Compared to film coated seed, primed seed emerged at lower rates in beds had been pre-irrigated and the initial irrigation following planting was delayed more than a day. Primed seed emerged at similar or greater rates than film coated seed if beds had not been pre-irrigated or if irrigation following planting occurred within a day. Primed seed emerged poorly if soils had been pre-irrigated, but initial post planting irrigation was delayed more than a week. If irrigation occurred shortly after planting, the performance of primed seed was superior. Residual soil moisture was sufficient to initiate germination, and when the beds were irrigated, seeds emerged quickly. There were few differences in performance between seed treatments when beds had not been pre-irrigated. The low value for PAT treated seeds in fig. 4 (1 day) is the result of a planting problem.. These results taken together suggest that delays between planting and irrigation can adversely affect the performance of primed seed when soil moisture is present at levels too limiting for germination.

Soil amendments:

There were no significant difference on average between sprinkler-irrigated and furrow-irrigated plots in this trial. There was a significant difference between PAC treated soil and the control (no soil amendment) in cumulative emergence and final establishment, but not with respect to post-emergence mortality (Fig. 5). Treatment interactions among irrigation practices, soil amendments, and seed treatments were observed. The best treatment combination (PAC, primed seed, sprinkler irrigation) resulted in 81 % emergence. Under furrow irrigation, the same seed and soil treatment combination resulted in 78 % emergence, both excellent levels. In general, there was a tendency for soil amendments to improve overall emergence, though differences for the most part were not significant.

Conclusions

1. The use of an insecticide with seed continues to result in increased emergence rates compared to seed treatments in which it is absent. This leads to the inference that loss of seed and emerging seedlings prior to visual emergence occurs commonly in most of the locations where these tests have occurred. A seed insecticide seems to be important in insuring higher rates of emergence.

2. Seed treatments interact with the environmental and biological conditions in seed beds. A treatment like priming can both improve and harm emergence, depending on soil moisture and irrigation practice. Newer, more expensive seed treatments cannot be used in isolation from other management practices. To gain positive results from priming, careful irrigation practice also is required.

3. Soil amendments that reduce crust strength may help improve emergence in soils that tend to crust. PAC treatments resulted in high rates of emergence, compared to controls in this year's trial. Results from this trial are preliminary, however, and additional evaluation of available amendments is required.

List of figures:

Fig. 1. Comparison of irrigation treatment means using film coated seed. Error bars are standard errors.

Fig. 2. Comparison of irrigation treatment means using primed seed. Error bars are standard errors.

Fig. 3. Comparison of seed treatment means in pre-irrigated plots. Error bars are standard errors.

Fig. 4. Comparison of seed treatment means in dry (not pre-irrigated) plots. Error bars are standard errors.

Fig. 5. Comparison of treatment means for cumulative emergence, final establishment, and cumulative mortality as influenced by soil and seed treatments. Error bars are standard errors.

PAC: (Polyacrylamide) at 20 lbs per acre applied in a 4 to 5 inch band, G1: gypsum at 400 lbs per acre applied in a 3 to 4 inch band; G2: gypsum at 800 lb per ac; C: control, no soil amendment.

Table 1

Seed treatment testing objectives (2000 Trials-Davis)

Betaseed 4776R (lot # 134022030P; 96.3% germ)

Table 2

Key to codes used

Table 3

Seed treatment comparisons. Cumulative emergence treatment means (Davis, 2000)

* lower rate of Gaucho (20 g/unit)

Table 4

Seed treatment comparisons. Cumulative emergence contrasts (Davis, 2000)

1. Tests whether priming increases cumulative emergence. A significant results means that it does. 2. Tests whether there is a difference between high and low rates of Gaucho on emergence. A significant result suggests that higher rates are better. 3. Tests the average of treatments with Gaucho against the average of treatments without Gaucho. A significant results means that Gaucho enhances cumulative emergence. This contrast excludes the primed treatment. 4. Tests other wise identical treatments for the effectiveness of Protégé. A significant difference means that Protégé treated seeds emerged better.

Table 5

Seed treatment comparisons. Final establishment treatment means (Davis, 2000)

* lower rate of Gaucho (20 g/unit)

Table 6

Seed treatment comparisons. Final establishment contrasts (Davis, 2000)

1. Tests whether priming increases final establishment. A significant results means that it does. 2. Tests whether there is a difference between high and low rates of Gaucho on emergence. A significant result suggests that higher rates are better. 3. Tests the average of treatments with Gaucho against the average of treatments without Gaucho. A significant results means that Gaucho enhances final establishment. This contrast excludes the primed treatment. 4. Tests other wise identical treatments for the effectiveness of

Protégé. A significant difference means that Protégé treated seeds survived better.

Table 7

Seed treatment comparisons. Cumulative post-emergence mortality means (Davis, 2000)

* lower rate of Gaucho (20 g/unit)

Table 8

Cumulative post-emergence mortality contrasts (Davis, 2000)

1. Tests whether priming increases post emergence mortality. A significant results means that it does. 2. Tests whether there is a difference between high and low rates of Gaucho on post emergence mortality. A significant result suggests that higher rates are better. 3. Tests the average of treatments with Gaucho against the average of treatments without Gaucho. A significant results means that Gaucho increased post emergence mortality numbers in an absolute sense. This contrast excludes the primed treatment. 4. Tests other wise identical treatments for the effectiveness of Protégé. A significant difference means that Protégé treated seeds had less mortality.

Table 9

Proportional post-emergence mortality means (Davis, 2000)

* lower rate of Gaucho (20 g/unit)

Table 10

Proportional post-emergence mortality contrasts (Davis, 2000)

1. Tests whether priming increases mortality proportionally. A significant results means that it does. 2. Tests whether there is a difference between high and low rates of Gaucho on the proportion of seedlings dying. A significant result suggests that lowr rates are better. 3. Tests the average of treatments with Gaucho against the average of treatments without Gaucho. A significant result means that Gaucho decreased post emergence mortality as a percent of emerged seedlings. This contrast excludes the primed treatment. 4. Tests otherwise identical treatments for the effectiveness of Protégé. A significant difference means that Protégé treated seeds had proportionally lower mortality.

Fig.1. Irrigation trial, film-coated seed. Means of irrigation treatments. (Error bars are standard errors in all the figures).

Fig. 2. Irrigation trial, primed seed. Means of irrigation treatments.

Fig. 3. Irrigation comparisons. Seed treatments

Fig. 4. Irrigation comparisons. Seed treatments

Fig. 5. Soil amendment comparisons.

1. Department of Agronomy and Range Science, University of California, Davis. srkaffka@ucdavis.edu