Commodities: Fieldcrops: Peanuts
2009 Peanut Update
UPDATE ON SEEDING RATES FOR PEANUT
R. Scott Tubbs, John P. Beasley Jr., and Albert K. Culbreath
Nearly all agricultural inputs required to grow a successful crop are either at, or approaching, record highs in terms of costs to the grower. This makes it increasingly difficult to maximize profitability and numerous growers are looking for ways to reduce inputs without affecting yield potential. Since fuel prices are currently at a five year low and approximately 50% of fall 2008 prices, this is one welcome relief in sight for 2009. However, fuel prices are very volatile and can not be solely considered for maximizing profit potential. There are many factors that can be altered in peanut production which can cut costs, but the grower assumes certain risks depending on which and how many variables are changed. With the release and increasing availability of highly disease resistant peanut varieties, one area of potential savings could be in seed costs. This savings becomes increasingly important when factoring in seed size of different varieties. Larger seeded varieties cost more per acre than an equivalent seeding rate of a smaller seeded variety since seed is sold by weight and each individual seed weighs more.
Since seed prices have risen drastically in the last two years, it is important to only plant the amount of seed necessary for getting a good stand of plants. Planting excessive seed is a waste of resources for several reasons. Plants will compete with each other for water, light, and physical space, so planting more seed than optimal will not always result in an increased stand since stronger plants will out-compete weaker ones causing them to eventually die. There is also an increased risk of spreading certain diseases (i.e. white mold). Plus, data has shown that yield potential reaches a plateau and is not improved with a greater plant stand beyond a certain point (UGA recommendations are for a final stand of four plants per foot of row).
Plains, GA – 2008
At the Southwest Georgia Research and Education Center in Plains, a trial was conducted in 2008 to evaluate seven peanut varieties using three different seeding rates (5.3 seed per foot [SPF], 6.0 SPF, and 7.0 SPF) on both single and twin row patterns. Pod yields were higher for twin rows (5504 lb/ac) over single rows (5020 lb/ac), regardless of seeding rate or variety. An interaction occurred between seeding rate and variety for yield and final plant stand (Figs. 1 and 2). The only variety displaying a statistical yield difference between seeding rates was ‘FL-07’, in which the 7.0 SPF rate yielded more than the 5.3 SPF rate (Fig. 1). Differences in plant stand were more abundant. The trend shows higher plant stands at the 6.0 or 7.0 SPF seeding rates for all varieties, and lowest plant stands at the 5.3 SPF rate (Fig. 2). However, in only a few instances did the final plant stand drop below the recommended 4 plants per foot of row (most often at the 5.3 SPF seeding rate), and never below 3.5 plants per foot. Also, this did not equate to yield losses for any variety with differences in final plant stand.
There was also an interaction between row pattern and variety for plant stand. All varieties had more than 4 plants per foot of row in the twin row pattern, and had statistically higher stands in twin rows than in single rows with the exception of ‘AP-3’ and ‘Georgia-03L’ varieties which had no statistical difference. Both of those varieties were among the highest in final plant stand in single rows, but among the lowest in final plant stand in twin rows. The other varieties did respond to row pattern in final plant stand, suggesting that plants will compete with each other more heavily in single rows compared to twin rows, eliminating unnecessary plants from the row. The only varieties to stay above the 4 plants per foot threshold in single rows were AP-3 and ‘Georgia Green’ when averaged over all seeding rates. Also, ‘AT 3085RO’ was among the highest in plant stand in twin rows, but among the lowest in plant stand in single rows. This would suggest that AT 3085RO has a favorable response to twin rows over single rows in terms of final plant stand, and all varieties had nearly a 500 lb/ac response in yield for twins over singles.
Differences in tomato spotted wilt (TSW) incidence occurred between row patterns (7.9% in single rows; 4.2% in twin rows) and among varieties (Georgia Green and Georgia-03L approximately 10%, all other varieties were less than 5% incidence). However, there were no differences in TSW incidence among seeding rates (data not shown).
- Differences among varieties within a given seeding rate are indicated by alphabetical notation, where a different letter indicates a statistical difference.
- Differences among seeding rates within a given variety are indicated by error bars (least significant differences), where bars that do not overlap indicate a statistical difference.
- Differences among varieties within a given seeding rate are indicated by alphabetical notation, where a different letter indicates a statistical difference.
- Differences among seeding rates within a given variety are indicated by error bars (least significant differences), where bars that do not overlap indicate a statistical difference.
Attapulgus, GA – 2008
At the Attapulgus Research and Education Center, eight peanut varieties were planted in twin rows with five seeding rates (5.2 SPF, 6.2 SPF, 7.0 SPF, 8.2 SPF, and 8.8 SPF). Four mid-maturity varieties (Georgia Green, ‘Georgia-06G’, Florida-07, and ‘Tifguard’) and four late-maturity varieties (‘Georgia-01R’, ‘Georgia-02C’, ‘C-99R’, and ‘York’) were evaluated. The mid-maturing varieties yielded more than the late-maturing varieties (Fig. 3), and had higher final plant stands with the exception of ‘Georgia-02C’ (Fig. 4). No differences in yield were observed among the seeding rates (Fig. 3). However, there were differences in final plant stand (Fig. 4), although all seeding rates resulted in plant stands above the recommended 4 plants per foot of row.
Similar to results at Plains, there were significant differences among varieties for TSW, with the late maturing varieties having higher TSW incidence than the mid-maturing varieties in most comparisons, with the exception of Georgia Green. Again, there were no differences in TSW among seeding rates.
- Differences among varieties or seeding rates are indicated by alphabetical notation, where a different letter indicates a statistical difference.
- Differences among varieties or seeding rates are indicated by alphabetical notation, where a different letter indicates a statistical difference.
Midville, GA – 2008
Four mid-maturity peanut varieties (Georgia-06G, AT 3085RO, Tifguard, and Georgia Green) were planted in twin rows at four seeding rates (4.4 SPF, 5.2 SPF, 6.2 SPF, and 7.0 SPF) at the Southeast Georgia Research and Education Center in Midville. Variety GA-06G had the highest yield, and there were no statistical differences among the other three varieties (Fig. 5). When averaged over all seeding rates, GA Green had the lowest final plant stand, and there were no statistical differences among the other three varieties (Fig. 6). No differences in yield were observed among the seeding rates (Fig. 5). However, there were differences in final plant stand (Fig. 6), with the two lower seeding rates resulting in lower plant stands than the two higher seeding rates. Incidence of TSW was so low at this location that it was not evaluated.
- Differences among varieties or seeding rates are indicated by alphabetical notation, where a different letter indicates a statistical difference.
- Differences among varieties or seeding rates are indicated by alphabetical notation, where a different letter indicates a statistical difference.
Tifton, GA – 2008
Four mid-maturity peanut varieties (Georgia-06G, Florida-07, Tifguard, and Georgia Green) were planted on April 23 in single rows at four seeding rates (3 SPF, 4 SPF, 5 SPF, and 6 SPF) at the Coastal Plain Experiment Station, Lang Farm. Stands that resulted from the 4 seeding rates were lower in Florida-07 than in the other three varieties in three of the four seeding rates, but stands were similar for the other varieties at all seeding rates except 6 SPF (Fig. 7).
Variety Georgia Green had the highest final incidence of TSW across all seeding rates. For Georgia Green, incidence of TSW was lower at 6 SPF than for 3 SPF (Fig. 8). There were no differences in TSW incidence among seeding rates for any of the other three varieties, and the three varieties were similar for TSW incidence (Fig. 8).
Yields of Florida-07, Georgia-06G, and Tifguard were higher than those of Georgia Green, and seeding rate had no effect on yield in any cultivar (Fig. 9).
Summary
There were yield and stand differences among varieties at all locations. Except at Tifton, yields and stands were highest and TSW incidence was lowest for GA-06G for all other locations and seeding rates when interaction occurred. Other new varieties like Florida-07, Tifguard, and AT 3085RO were consistently among or near the highest in yields and stands and lowest in TSW. It was also noted that AT 3085RO had a greatly reduced stand in single rows (among the lowest of all varieties tested) than in twin rows (among the highest of all varieties tested) at the Plains location. The data suggests that AT 3085RO is better suited to twin row planting than single row planting because of the improved plant stand since there was no difference in yield.
There were differences in plant stand among the various seeding rates used in these trials, and higher seeding rates resulted in higher plant stands. However, final plant stands remained above the recommended 4 plants per foot at seeding rates of 5.2 SPF or higher in most instances, with the exception of several specific varieties at Plains. Seeding rate also had no effect on yield for any location, except for one interaction effect with Florida-07 peanut in which higher yields occurred at 7.0 SPF compared to 5.3 SPF.
Despite there being no differences in TSW among seeding rates in any of these studies, there were reductions in plant stand at lower seeding rates. Reduced plant stands are at a greater risk of severe TSW infection than higher plant stands when stands drop below 4 plants per foot of row. This should be considered when planting varieties that are more susceptible to TSW such as Georgia Green. Severity of TSW has been low in the southeast the last few years, but a more severe outbreak could potentially be devastating to susceptible varieties if they have a less than optimal stand resulting from planting a lower seeding rate. Since Georgia Green is a smaller seeded variety, planting a reduced seeding rate will not be a large savings in seed costs, which is not worth the risk. However, larger seeded varieties like Florida-07, Georgia-06G, and Tifguard which have strong resistance to TSW could result in a significant savings in seed cost without a major increased risk to TSW incidence by reducing seeding rate from 6 SPF to 5 SPF. The key result is achieving 4 plants per foot of row at final stand, which should be possible when planting high quality seed with good germination at an appropriate seeding rate.
Therefore, it is recommended that Georgia Green should still be planted at 6 SPF, but newer varieties with excellent resistance to TSW may be planted at 5 SPF to keep total seed cost competitive with Georgia Green on a per acre basis. Although these results show no loss in yield potential when dropping seeding rate below 5 SPF, there is a reduced stand and thus potentially an increased risk of greater losses to TSW in circumstances with more severe disease pressure. Thus, it is not recommended to reduce seeding rate below 5 SPF at this time, regardless of variety planted.