By Jeremy Ross, Extension soybean agronomist/Professor
In my previous post (2019 Soybean Variety Selection (Part 1): Tools to Assist with Soybean Variety Selection), I discussed publications available from the University of Arkansas Division of Agriculture, and what questions should be asked when selecting soybean varieties. In this article, I will discuss several items and the concern with the quality of the soybean seed that will be planted in the coming weeks and months.
Due to the poor environmental conditions during the 2018 harvest, many of the lots of soybean seed that will be planted for 2019 have lower germination and accelerated aging (AA) scores than was observed a year ago (Table 1). Standard germination tests are used to give a reasonable idea of field emergence under favorable conditions. The accelerated aging test is a vigor test that can be used to estimate field emergence under unfavorable conditions. Ideally, high quality seed will have germination numbers above 80% and AA numbers above 65%. Results of the non-certified soybean seed samples tested by the Arkansas State Plant Board (ASPB) as of March 31, 2018 indicated the average germination and AA scores were 86% and 77%, respectively. The average germination and AA of non-certified soybean samples tested as of March 31, 2019 were 76% and 59%, respectively (Table 1). For the 2019 results, 41% of the samples tested below 80% on the germination test, and 46% of the samples tested below 65% for the AA test. This decrease in germination and AA give me great concern with establishing adequate plant stands for 2019. Ever seed lot will not have low germination and accelerated aging, but many will have lower than ideal numbers. Many seed companies have already removed many of the seed lots with very low germination results from the market. Because of this, many of the more popular soybean varieties are in short supply for 2019.
What can we do of 2019?
When it comes to planting seed with poorer than normal seed quality, producers will need to do everything they can to achieve an adequate plant stand with the first planting. The first step is to know what the germination and AA numbers are on each lot of seed to be planted on their farm. All companies test for germination, but not all test for accelerated aging. Some of these results could be as much as 2-3 months old, and depending on storage and handling of the seed, these numbers could be different from the initial tests. Therefore, to know the current status of seed to be planted, results from a current germination and AA test are needed. Soybean seed samples can be sent to the Arkansas State Plant Board – Seed Divisionto be tested for both Germination ($12) and Accelerated Aging ($8). This will be a total of $20 per sample, but money well spent to know how to place your seed during the planting window and how to adjust your seeding rate. Once samples are shipped to the ASPB, it will take 10-14 days to receive the results. So some planning will be needed to ensure results are received from the ASPB prior to planting of this seed.
When the germination results are obtained, seeding rates may need to be adjusted to compensate for lower than ideal seed quality. From research over the past few years, a final plant stand between 80,000 to 110,000 plants per acre is needed to maximize soybean grain yield. To reach these final plant stands with low quality seed, seeding rates may need to be increased 10-20% over normal seeding rates. Since the AA is an indicator of how seed will perform under unfavorable planting conditions (e.g., elevated soil temperatures, dry soil conditions, etc.) which typically occur during the latter part of the planting window, seed lots with higher AA results should be planted during this time.
There has been a lot of discussion on the use of insecticide/fungicide seed treatments on poor quality seed over the past few months. Because of the weather conditions during the 2018 harvest, higher than normal seed borne pathogens have been observed, and fungicide seed treatments may help with these pest. However, in the absence of these seed borne pathogens, seed treatments will not dramatically increase seed quality and emergence. With that said, we are strongly recommending a good insecticide/fungicide seed treatment on each seed lot to preserve the existing quality of each seed lot. With adjusted seeding rates based on a current germination test, seed treatments, adequate soil moisture, proper planting depth, a little luck, and cooperation from Mother Nature, hopefully everyone will have an adequate soybean plant stand with the first planting.