Stephen R. Kaffka

Introduction

A sugarbeet seedling emergence trial was conducted on the University of California, Davis campus during the summer of 2000 at the request of Astec Seed Company of Sheridan, Wyoming. This report summarizes the performance of different seed lot-seed treatment combinations in this trial.

Methods

Seeds from two different cultivars/seed lots, one with a poor vigor rating and one with a good vigor rating were selected by Astec, Inc.,. The N-H cultivar (295) was treated using two of Astec's commercial scale coating processes. Bare processed seed from both seed lots was also included (Table 1). We provided seed from Beta Seed, Inc.(B), and sent it to Astec and to Seed Systems, Inc. of Gilroy, California for treatment. Astec provided laboratory scale coatings approximately similar to those used in their commercial scale treatments for the B and HH (249) cultivars. Seed Systems applied their Priming Advance Treatment (PAT) to the Beta seed sample (Table 1). The Mega pellet (MP) and PAT treatments both aim at enhancing emergence rates and cumulative emergence, but using very different approaches. MP treatments use a sophisticated coating material to improve the absorption of water by seeds, while PAT advances the germination process metabolically by exposing seed to water prior to germination. The details associated with these treatments are proprietary.

All these seeds were counted into units of one hundred seed and planted using a cone planter into 30 foot rows. There were 5 replications of each treatment and treatments were arranged in a Randomized Complete Block Design. All plots were furrow irrigated two times. At emergence, each seedling was labeled with a small wooden stake. Using stakes allows for the identification of all emerging seedlings. The stake was removed if the seedling died and the cause of mortality was evaluated visually in the field at that time.

The sum of the number appearing during the counting period is cumulative emergence. The last count, at the four to six true leaf stage was considered to be the final establishment. The difference between cumulative emergence and final establishment is cumulative mortality (post-emergence). If the amount of seed planted is known, pre-emergence losses can be calculated by difference using observed cumulative emergence, corrected for the percent viable seed from laboratory germination tests. Pre-emergence loss is defined from an agronomic perspective. If seedlings had not emerged after two or three irrigations and by the time the majority of seedlings had reached the four to six true leaf stage, they were included in the pre-emergence loss category. They may still been viable, but were of no agronomic use to growers. Late emerging seedlings may also act more like weeds than contribute to crop yields.

Stand counts were made from the first sign of emergence for six days in a row (up to day 11 from irrigation). By that time, the majority of seed in all treatments that would emerge, had emerged. Then, counts were made less frequently afterwards until the four to six true leaf stage was reached. Most seedlings surviving by the final count (day 21 from the first irrigation) had reached the fourth to six true leaf stage. The relative rates of cumulative emergence were calculated for the B cultivar. This cultivar was used to compare MP and PAT treatments versus bare seed. Typically, bare seed will emerge faster than coated seed, or seeds treated with fungicides or insecticides. All values are reported as a proportion of the final cumulative rate of emergence for each treatment.

No post-emergence control of insects occurred during the trials, and herbicides were not used. All data analysis was done using SAS (v7.0). Data was analyzed as a simple RCBD with replications as blocks. Cultivar and seed treatment differences were evaluated using single degree of freedom contrasts. Data were not transformed, because the values analyzed were for the most part within the range not thought to be necessary for transformation, and missing values (seeds failing to emerge) were regarded as lost, or of little agronomic value rather than as viable members of the experimental population (Little and Hills, 1978). By ignoring un-emerged seeds, the assumption of normality becomes reasonable.

Results

A summary of the behavior of the different cultivar/seed lot-seed treatment combinations is provided in Table 2 and Fig. 1 and 2. The B seed lot emerged and survived in significantly larger amounts than the other seed lots, irrespective of treatments or coatings, and the HH cultivar had the fewest seedlings emerge and survive. Within the HH and N-H cultivars, bare seed emerged in the largest amounts, followed by MP coated seeds. Within the B seed, MP coated seeds emerged in the largest amount, followed by PAT and then by bare seed. ANOVA and single degree of freedom contrast statistics evaluating the significance of these differences are reported in Table 3.

Relative rates of emergence for the B cultivar seed are presented in Fig. 3. PAT treated seed emerged marginally faster than bare seed or MP seed. This higher rate did not result in better establishment rates.

Discussion

There were significant differences among the seed lots tested using the same seed coating technology. If a farmer were to have planted the HH cultivar/seed lot, stand failure would have been due primarily to the quality of that seed, irrespective of other management factors. For the N-H seedlot, coatings significantly reduced emergence and correlated survival. The MP coating resulted in more seedlings than the UP, but both inhibited emergence and reduced survival compared to bare seed. This is unusual in our experience with trials at the Davis campus site and elsewhere in California. The lack of fungicide protection on bare seed commonly results in significant seedling loss. Not so in this trial, but I would expect different results if the trial were repeated. Similarly, in 2000, MP treated seed emerged much better than the control treatment (Kaffka, 2000). Results with the B seed lot more closely resembled previous results. It is not clear why seed coatings, particularly the MP coating, resulted in poorer stands. In other trials at Davis and elsewhere, pelleted seeds usually emerge more slowly, but survive in larger amounts than bare seed controls.

There were no significant differences between the MP and PAT treated seeds using lot B. Approximately 10% more MP treated seed emerged, but the number established was nearly identical. PAT seeds emerged marginally faster. Additional comparisons should be carried out.

The absence of the use of an insecticide like imidicloprid likely reduced overall emergence rates. Typically at Davis, 5% to 15% more seedlings emerge and survive when imidicloprid is used with otherwise identical treatments. Had it been used, the survival rate of the B seed lot treatments would have been sufficient to allow a grower to plant to a stand, helping to justify the investment in more expensive seed treatments like insecticide application and sophisticated coatings or priming.

References

Little, T.M., and Hills, F. J. (1978). Agricultural Experimentation. Design and Analysis. John Wiley and Sons. New York.350 p. Kaffka, S.R. (2001). Astec Emergence Trials, summer 2000. Unpublished report.(http://sugarbeet.ucdavis.edu)

Table 1

*Beta Seed lot unknown. Seed treatments applied to HH and Beta seed used lab-scale equipment. Commercial scale equipment was used on N-H.

Table 2

Results of emergence trial

Table 3A

Cumulative emergence: ANOVA at final count. (Mean = 51.1 %)

Table 3B

Single degree of freedom contrasts

Fig. 1. Average cumulative emergence and total establishment for

the three cultivars, (Error bars are s.e.)

Fig. 2. Cumulative emergence by day for each of the cultivars, (Error bars are s.e.)

Fig. 3. Relative rate of emergence for the B cultivar