Introduction
Peanut (Arachis hypogaea L.) is an important food and oil crop in Mississippi (MS) and the United States (U.S.). Approximately 8,900 and 670,000 ha of peanut were harvested in MS and the U.S., respectively, in 2020 (USDA NASS, 2021). Mississippi ranked 7th out of the 13 peanut producing states in total production in 2020 (USDA FAS, 2021). The U.S. is ranked 4th in peanut production worldwide at 2,900,000 metric tons in 2020 (USDA FAS, 2021; USDA NASS, 2021). Total production can be divided into four different market types of peanut. Virginia market types comprise approximately 15% of the U.S. crop while Spanish and Valencia market types account for approximately 5% of the U.S. crop (Boote, 1982; USDA NASS, 2021). Runner market type peanut accounts for approximately 80% of the U.S. market (Boote, 1982; Putnam et al., 1991; USDA NASS, 2021).
During the 130 to 160 days after planting needed for runner types to reach maturity (Boote, 1982; Putnam et al., 1991), peanut is prone to excessive vegetative growth. Peanut produces more vegetative growth than required for maximum pod yield (Mitchem et al., 1996). Excessive vegetative growth can increase the likelihood of disease occurrence and severity due to increased humidity beneath the canopy (Beam et al., 2002; Culpepper et al., 1997; Jordan et al., 2008; Studstill, et al., 2020; Wu and Santelmann, 1977). Excessive vegetative growth can also contribute to damage from equipment traveling through fields during mid- or late-season chemical applications. Reduced digging and harvest efficiency is an additional consequence of excessive vegetative growth often attributed to decreased row visibility (Beam et al., 2002; Culpepper et al., 1997; Jordan et al., 2008; Studstill, et al., 2020; Wu and Santelmann, 1977). Additionally, pods lost from plants during digging can increase with excessive canopy growth contributing to substantial yield loss (Beam et al., 2008). Over the past 40 years, negative effects of excessive vegetative growth have often been managed by plant growth regulators (Beam et al., 2002; Brown and Ethredge, 1974).
Historically, daminozide was applied to peanut to prevent internode elongation (Brown and Ethredge, 1974). Brown and Ethredge (1974) observed increased pods per plant and enhanced row visibility when daminozide was applied. Although daminozide application enhanced row visibility, overall yield and growth response was inconsistent, and product registration was cancelled in 1989 due to health concerns from consumers (Anonymous, 1989; Beam et al., 2002; Culpepper et al., 1997; Mitchem et al., 1996). In early 2000, prohexadione calcium was developed as a suitable alternative to daminozide (Studstill et al., 2020). In comparative studies, peanut growth and yield responded similarly to both prohexadione calcium and daminozide application (Culpepper et al., 1997; Mitchem et al., 1996).
Prohexadione calcium is a plant growth regulator used in apple (Malus domestica Borkh.), grain sorghum [Sorghum bicolor (L.) Moench], oilseed rape (Brassica napus L.), peanut, rice (Oryza sativa L.), tomato (Solanum lycopersicum L.), and wheat (Triticum aestivum L.) to prevent excessive vegetative growth and promote reproductive growth (Grossmann et al., 1994; Mitchem et al.1996; Studstill, et al., 2020). Prohexadione calcium prevents excessive vegetative growth by affecting gibberellin biosynthesis by blocking kaurene oxidase (Nakayama et al., 1990a; Nakayama et al., 1990b; Nakayama et al., 1991). Promotion of reproductive growth is attributed to increased abscisic acid and cytokinin levels (Grossmann et al., 1994; Studstill et al., 2020).
The effects of prohexadione calcium on peanut have been elucidated in several studies. Prohexadione calcium application resulted in increased row visibility, increased overall pod maturity, decreased pod loss, and increased yield (Beam et al., 2002; Jordan et al., 2001; Jordan et al., 2008; Mitchem et al., 1996; Studstill et al.¸ 2020). Studstill et al. (2020) found that, when compared to yields following prohexadione calcium application at 140 g a.i./ha at 50% canopy closure (CC) and at 100% CC (7,600 kg/ha), reduced application rates (70 g a.i./ ha) did not decrease yield (7,500 kg/ha). Mitchem et al. (1996) observed increased yield only when specific application timings were utilized. While these studies elucidated the benefits of prohexadione calcium application, few studies were conducted using modern runner market type peanut cultivars which is the most common market type grown in MS. Furthermore, research regarding prohexadione calcium effects on runner market type peanut growth and yield is lacking.
The prohexadione calcium product label recommends application of 140 g a.i./ha at both 50% CC and 100% CC, i.e., when 50% and 100% lateral vines initially touch, respectively. Environmental conditions and management strategy may prevent application of prohexadione calcium at these precise timings. Runner market type peanut growers have little information on the implications of applying prohexadione calcium at timings and rates that deviate from the labelled recommendation. Therefore, the objectives of this research are to determine if applying prohexadione calcium to peanut at timings and rates that differ from the labelled recommendation will affect runner-type peanut growth and yield.
Materials and Methods
Research was conducted in 2020 and 2021 at multiple on-farm locations in Mississippi. In 2020, the effect of prohexadione calcium application timing was investigated, while in 2021, both prohexadione calcium application timing and rate were investigated. In each year, three locations were included (Table 1). Treatments and dates for planting, prohexadione calcium application, digging, and harvest in 2020 and 2021 are given in Table 2 and Table 3, respectively. Prohexadione calcium (Apogee® 27.5 WDG, BASF Corp. or Kudos® 27.5 WDG, Fine-Americas) treatments, including the labelled rate of 140 g a.i./ha, were applied with a surfactant blend plus urea ammonium nitrate at 1% v/v (Dyne-A-Pak, Helena Agri-Enterprises). All treatments in 2020 were applied with a tractor-mounted, roller-pump sprayer utilizing ULD 120025 nozzles (Pentair Hypro), whereas all treatments in 2021 were applied with a Mudmaster TM sprayer (Bowman Manufacturing Co.) equipped with a hydraulic roller-pump utilizing ULD 120025 nozzles.
Location, soil series and texture, row spacing, and treatment area for peanut experiments investigating the effect of prohexadione calcium application timing in 2020 and 2021.
Planting dates, application dates, digging dates, and harvest dates in Mississippi in 2020.
Planting dates, application dates, digging dates, and harvest dates in Mississippi in 2021.
Peanut at all locations and years were grown under dryland conditions and peanut cultivar Georgia-06G was seeded at 20 seeds/m at a depth of 4 to 6 cm. All sprayers were calibrated to deliver 187 L/ha at 276 kPa. Agronomic practices including fertilization and pest management were determined by each grower at each location per local recommendations. Application timings were determined by utilizing images from Canopeo (Oklahoma State University, Stillwater, OK) which uses true color images that convert all green reflectance to white and all other light reflectance to black and the percent white to black is calculated (Patrignani and Ochsner, 2015).
Above and below ground peanut biomass samples were collected after digging from a 1-m length of row from each plot and then dried in a forced air dryer at 65ºC for one week. Plant weight, pod weight, and pod count data were collected from these samples. Pod loss data were collected from 1 m2 within each plot. Peanut plants were machine dug and inverted with Amadas Industries ADI-638 at Cruger, Tchula, Carlisle, and Port Gibson locations and ADI-636 in Hamilton and Smithville locations. After digging, pods were machine harvested with Amadas Industries AR2200 and M2120 at Cruger, Tchula, Carlisle, and Port Gibson locations and Amadas Industries A-9990 at Hamilton and Smithville locations. Peanut pods were weighed using a custom dump cart equipped with load cells (Shortline Manufacturing, Shaw, MS).
Treatments were arranged in a randomized complete block design with three replications. Plant weight, pod loss, pod weight/plant, pod count and yield data were analysed using PROC GLIMMIX in SAS 9.4 and data for all parameters are presented as treatment means pooled over location and year (Blouin, et al., 2011; Buol, et al., 2019). Location, year, and interactions of the two were considered random effects. All data were subjected to analysis of variance and means were separated using Fisher’s protected least significant difference (LSD) at α=0.05.
Results and Discussion
Prohexadione Application Timing Experiment – 2020
In 2020, prohexadione calcium application timing had no effect on plant weight, pod loss, pod weight/plant, or pod count (Table 4). Plant weight ranged from 54 to 69 g/m of row. Pod loss (pods/m2) ranged from 5.1 to 6.5 and pod counts (number/plant) ranged from 21 to 26. Pod weight/plant varied from 27 to 34 g. Yield ranged from 6,200 kg/ha to 6,900 kg/ha and responses were observed following prohexadione calcium application. However, varying prohexadione calcium application timing from the labelled recommendation did not affect peanut yield. Applying prohexadione calcium twice in one week at 100% CC was the only application timing to improve peanut yield (6,900 kg/ha) relative to not applying the plant growth regulator (6,200 kg/ha).
Effect of prohexadione calcium application timing on peanut growth and yield pooled over environment in Mississippi in 2020.
Prohexadione Application Timing and Rate Experiment – 2021
In 2021, prohexadione calcium application affected pod count and peanut yield, but had no effect on plant weight, pod loss, or pod weight/plant (Table 5). Plant weight ranged from 46 to 55 g/m of row. Pod loss (pods/m2) ranged from 3.9 to 4.7 and pod weight/plant varied from 23 to 29 g. Following the recommended prohexadione calcium application timing, pod count per plant was greater (21 pods/plant) compared to those observed following two applications of prohexadione calcium in one week at 100% CC (16 pods/plant). Yield ranged from 6,800 kg/ha to 7,300 kg/ha and responses were observed following prohexadione calcium application. No prohexadione calcium application timing or rate resulted in different peanut yield than that observed following the recommended application timing and rate of 140 g a.i. applied at 50% CC followed by 140 g a.i. at 100% CC. Similarly, applying prohexadione calcium at any specific time or rate did not affect yield relative to the non-treated control. The only difference in peanut yield was observed following a single 140 g a.i./ha application at 100% CC (7,300 kg/ha) compared to yield following either a single application of 280 g a.i. of prohexadione calcium at 100% CC (7,000 kg/ha) or two applications of 140 g a.i. within one week at 100% CC (6,800 kg/ha).
Effect of prohexadione calcium application timing and rate on peanut growth and yield pooled over environment in Mississippi in 2021.
These results deviate slightly from other literature that has investigated prohexadione calcium application effect on pod loss and peanut yield. However, a large portion of previous research was conducted using Virginia market type peanut. Beam et al. (2002) observed reduced pod loss following prohexadione calcium application whereas in our work, no difference in pod loss was observed due to prohexadione calcium application. It has also been noted in previous research that yield response following prohexadione calcium application is inconsistent (Culpepper et al. 1997; Jordan et al. 1997; Jordan et al. 2008; Mitchem et al. 1996). Beam et al. (2002) observed increased yield following prohexadione calcium application but noted variation in magnitude and significance of response between cultivars. Studstill et al. (2020) observed no differences in yield of runner market type peanut following application of prohexadione calcium. However, they also observed increased yield following application of prohexadione calcium at 105 g ai/ha compared to a non-treated control. These data differ from previous results as we observed no difference in peanut yield following application at labelled rates or timings. Cultivar, variation in vine growth, soil type and texture, environmental conditions, and cultural practices may contribute to variation in yield response and should be investigated further with runner type peanut (Jordan et al. 2000; Studstill et al. 2020).
Summary and Conclusions
The objectives of this research were to determine if applying prohexadione calcium to peanut at timings and rates that differ from the labelled recommendation will affect runner market type peanut growth and yield. Peanut growth as defined by plant weight, pod loss, and pod loss/plant was unaffected by prohexadione calcium application. Yields from all treatments, including those from non-treated areas, were similar to those observed following application of the label recommendation of one application at 50% CC + one application at 100% CC at 140 g a.i./ha. Also noteworthy, only one prohexadione application treatment, two applications of 140 g a.i./ha within one week at 100% CC, resulted in increased yield compared to the non-treated control. Numerous previous studies have elucidated the benefit of prohexadione calcium application for management of excessive vegetative growth while also noting variation in yield response to prohexadione calcium application. Therefore, application of prohexadione calcium to manage excessive vegetative growth should be considered in MS peanut production; however, yield response may be inconsistent.
Acknowledgements
Funding for this project was provided by the Mississippi Peanut Promotion Board.
Literature Cited
Anonymous. 1989. Daminozide (Alar) pesticide cancelled for food uses. United States Environmental Protection Agency. https://www.epa.gov/archive/epa/aboutepa/daminozide-alar-pesticide-canceled-food-uses.html. Accessed:19 September 2022.
Beam J. B., Jordan D. L., York A. C., Isleib T. G., Bailey J. E., McKemie T. E., Spears J. F., and Johnson P.D.. 2002. Influence of prohexadione calcium on pod yield and pod loss of peanut. Agron. J. 94(2):331-336.
Blouin D. C., Webster E. P., and Bond J.A.. 2011. On the analysis of combined experiments. Weed Tech. 25(1):165-169.
Boote K. J. 1982. Growth stages of peanut (Arachis hypogaea L.). Peanut Sci. 9(1):35-40.
Brown R., and Ethredge W.. 1974 Effects of succinic acid 2,2-dimethylhydrazide on yield and other characteristics of peanut cultivars. Peanut Sci. 1(1):20–23. doi: https://doi.org/10.3146/i0095-3679-1-1-7.
Buol J. T., Reynolds D. B., Dodds D. M., Mills J. A., Nichols R. L., Bond J. A., Jenkins J. N., and DuBien J.L.. 2019. The effect of cotton growth stage on response to a sublethal concentration of 2, 4-D. [: Weed Tech.], 33(2):321-328.
Culpepper A.S., Jordan D.L., Batts R.B., and York A. C.. 1997. Peanut response to prohexadione calcium as affected by cultivar and digging date. Peanut Sci. 24(2):85–89. doi: https://doi.org/10.3146/i0095-3679-24-2-5.
Grossmann K., König-Kranz S., and Kwiatkowski J.. 1994. Phytohormonal changes in intact shoots of wheat and oilseed rape treated with the acylcyclohexanedione growth retardant prohexadione calcium. Physiologia Plantarum 90(1):139-143.
Jordan D.L., Beam J.B., Johnson P.D., and Spears J.F.. 2001. Peanut response to prohexadione calcium in three seeding rate–row pattern planting systems. Agron. J. 93(1):232-236. https://doi.org/10.2134/agronj2001.931232x.
Jordan D. L., Nuti R. C., Beam J. B., Lancaster S. H., Lanier J. E., Lassiter B. R., and Johnson P.D.. 2008. Peanut (Arachis hypogaea L.) cultivar response to prohexadione calcium. Peanut Sci. 35(2):101-107.
Jordan D. L., Swann C. W., Culpepper A. S., and York A.C.. 2000. Influence of adjuvants on peanut (Arachis hypogaea L.) response to prohexadione calcium. Peanut Sci. 27(1):30-34.
Mitchem W.E., York A.C., and Batts R.B.. 1996. Peanut response to prohexadione calcium, a new plant growth regulator. Peanut Sci. 23(1):1–9. doi: https://doi.org/10.3146/i0095-3679-23-1-1.
Nakayama I., Kamiya Y., Kobayashi M., Abe H., and Sakurai A.. 1990. Effects of a plant-growth regulator, prohexadione, on the biosynthesis of gibberellins in cell-free systems derived from immature seeds. Plant and Cell Physiology 31(8):1183–1190. https://doi.org/10.1093/oxfordjournals.pcp.a078033.
Nakayama I., Miyazawa T., Kobayashi M., Kamiya Y., Abe H., and Sakurai A.. 1990. Effects of a new plant growth regulator prohexadione calcium (BX-112) on shoot elongation caused by exogenously applied gibberellins in rice (Oryza sativa L.) seedlings. Plant and Cell Physiology 31(2):195-200. https://doi.org/10.1093/oxfordjournals.pcp.a077892.
Nakayama I., Miyazawa T., Kobayashi M., Kamiya Y., Abe H., and Sakurai A.. 1991. Studies on the action of the plant growth regulators BX-112, DOCHC, and DOCHC-Et. In Takahashi, N., Phinney, B.O., and MacMillan J. (eds). Gibberellins. Springer, New York, NY. 311-319. https://doi.org/10.1007/978-1-4612-3002-1_30.
Patrignani A., and Ochsner T.E.. 2015. Canopeo: A powerful new tool for measuring fractional green canopy cover. Agron. J. 107(6):2312-2320.
Putnam D., Oplinger E.S., Teynor T.M., Oelke E.A., Kelling K.A., and Doll J.D.. 1991. Peanut: Alternative field crops manual. Purdue University. https://www.hort.purdue.edu/newcrop/afcm/peanut.html. Accessed 19 September 2022.
Studstill S. P., Monfort W. S., Tubbs R. S., Jordan D. L., Hare A. T., Anco D. J., Sarver J. M., Ferguson J. C., Faske T. R., Cresswell B. L., and Tyson W.G.. 2020. Influence of prohexadione calcium rate on growth and yield of peanut (Arachis hypogaea). Peanut Sci. 47(3):163-172.
USDA FAS United States Department of Agriculture Foreign Agricultural Service 2021. Oilseeds: World Markets and Trade. Retrieved from: https://usda.library.cornell.edu. Accessed: 06 January 2022.
USDA NASS United States Department of Agriculture National Agricultural Statistics Service 2021. Crop Production. Retrieved from: https://usda.library.cornell.edu. Accessed: 06 January 2022.
Wu C.H., and Santelmann P.W.. 1977. Influence of six plant growth regulators on Spanish peanuts. Agron. J. 69(3):521-522.