Prohexadione calcium, a plant growth regulator, has been used on virginia market type peanut cultivars for many years to manage excessive vine growth and improve digging efficiency. Prohexadione calcium has not been widely used on runner market type cultivars due to their slower growth habit and sporadic yield response at the labeled rate until recent research showed lower use rates of prohexadione calcium provided similar vine control and enhanced yield response. Large plot experiments were conducted in Colquitt county at the Darrell Williams Research Farm on the Sun Belt Ag Expo to quantify yield and market grade quality and economics of using prohexadione calcium at 105 g a.i./ha on six runner type cultivars. Prohexadione calcium was applied twice during the growing season. The first application was made when 50% or greater of lateral vines from adjacent rows were touching. A second application of each treatment was applied 14d after the first application. The runner type cultivars were Georgia-06G, Georgia-12Y, Georgia-13M, Georgia-14N, TUFRunner TM -297, and TUFRunner TM -511. Similar large-plot experiments were conducted on farms in Baker and Early counties evaluating yield and economic response of prohexadione calcium on Georgia-06G. A non-treated control was used in all experiments. Prohexadione calcium increased pod yield in all experiments ranging from 450 to 650 kg/ha compared to the non-treated control with response similar across cultivars. Prohexadione calcium reduced the dollar value per metric ton (DVMT) as a result of lowering total sound mature kernel (%TSMK) percentages up to 3 points. The higher yields obtained for the prohexadione calcium-treated peanut provided higher gross dollar value return/ha (GDR) in all experiments and higher gross dollar value return/ha above treatment cost (GDRAT) in the on-farm trials. Therefore, prohexadione calcium at 105 g/ha applied twice on runner market type peanut is warranted to improve yield and financial return when excessive vine growth is a concern.

ABSTRACT Prohexadione calcium, a plant growth regulator, is commonly used on virginia market type peanut ( Arachis hypogaea L.) cultivars to manage excessive vine growth and improve digging efficiency. However, use of prohexadione calcium on runner market type cultivars has been minimal. The objective of this research was to evaluate prohexadione calcium on virginia and runner market type peanut cultivars at multiple rates in small-plot (17 site years) and on-farm (5 site years) experiments. Applications of prohexadione calcium were at the manufacturer's recommended use rate of 140 g a.i./ha (1x), 105 g a.i /ha (0.75x), and 70 g a.i /ha (0.5x) rates. A non-treated control was also included in all experiments. Cultivar and treatment responses were evaluated based on mainstem height, yield, total sound mature kernels, and return on investment. Plants treated with prohexadione calcium had greater row definition based on a 1-10 row visibility rating scale. Plant main stem heights were often shortened when prohexadione calcium was applied compared to the control, although response varied by location and by year. Average mainstem heights were 26 cm for non-treated plots and 23 cm for prohexadione calcium treated plots across all virginia market type small plot experiments. Prohexadione calcium did not significantly increase yield at any rate in any small plot experiments regardless of rate. Reduced rates of prohexadione calcium significantly increased yield in all the large on-farm experiments compared to the control. Yield increases ranged from 453 to 731 kg/ha for all prohexadione calcium treatments compared to the control across all large plot on-farm experiments. The greatest return on investment was the 0.75x rate resulting in an increase in revenue of $210 ha −1 . With an increase in yield and return on investment in all large plot on-farm experiments and not in small plot experiments no matter the market type, it is assumed that the growth and yield response to prohexadione calcium may be more pronounced where soil variability is greater, affecting growth, digging, and yield potential. Prohexadione calcium can be beneficial in virginia market type and runner market type peanut cultivars to decrease vine growth and increase yield.

ABSTRACT Weed control is an integral part of peanut ( Arachis hypogaea L.) production systems. Paraquat is a staple postemergence (POST) herbicide used in peanut production in the Southeast US. Inorganic liquid nutrient (ILN) concentrates are liquid fertilizers that are recommended for use by producers in tank-mixtures with paraquat by some distributors. Irrigated and non-irrigated field trials were conducted to quantify the safening effect of ILN in various herbicide tank-mixtures on peanut and determine the suitability as tank-mix replacements for bentazon. Field studies indicated similar POST herbicide responses for peanut injury. Greenhouse experiments evaluated POST paraquat tank-mixtures with ILN for weed control and biomass reduction. Paraquat plus S -metolachlor caused significant leaf burn and stunting. Greatest peanut foliar injury occurred 3 d after treatment (DAT) but was transient. For the irrigated field trial, paraquat plus S -metolachlor plus ILN had similar injury levels as compared to paraquat plus S -metolachlor plus acifluorfen plus bentazon at 22 to 25%. For the non-irrigated field study, the application of paraquat plus ILN had 10% injury compared to paraquat at 22%. While injury was the greatest directly following application, peanut was able to recover with no yield or grade loss for both the irrigated and non-irrigated studies. In the greenhouse study, the effect of ILN varied by weed species and reduced leaf injury on several broadleaf weeds. While the addition of ILN to the various paraquat tank-mixtures initially reduced injury, it did not correspond to increases in yield or grade. The variability in weed control, transient injury mitigation, and no yield increase indicates that Georgia peanut growers will receive no benefit for including ILN in their paraquat tank-mixtures but if needed to improve crop nutrition, ILN will not reduce weed control.

ABSTRACT Many guidelines for agronomic management of peanut ( Arachis hypogaea L.) are well-established when considered individually. However, crop productivity is typically driven by more than one variable and the interactions of multiple practices are not as easily derived. With an ever-changing availability of new cultivars with greater disease resistance, improved yield and/or grade potential, and varying growth characteristics, there is a steady need for agronomic research in both the immediate and distant futures. In some cases, traditional agronomic experimentation on variables such as rotations, tillage and land management, timing of planting, row pattern and spacing, seeding rate, irrigation, plant growth regulators, inoculant/biological products and fertilization need to be revisited every several years when a new cultivar becomes commercially relevant. This is especially true with differing climates and soil types in various growing regions. The effects of climate and weather along with pest pressure, pest management programs, and maturity characteristics of cultivars are also drawing the attention of peanut agronomists to improve predictability of optimum maturity. Yet, peanut agronomists are also attempting to adapt new ideas to assist with management decisions and increase revenue potential for growers to stay competitive in a very volatile commodity market domestically and with fluctuating export opportunities. The adoption of technologies such as GPS guidance, seed monitors, aerial imagery, and variable rate planting or spraying equipment are becoming more common to assist growers with better precision in planting and digging practices, ensuring proper seed placement, and assessing problematic areas in the field for site-specific in-season management decisions. So many excellent achievements have been made through the collaborations of scientists of the American Peanut Research and Education Society over the last 50 years, and there is no doubt that similar collaborations remain strong throughout the current membership to lead us into the future.

ABSTRACT Calcium improves seed formation and development of peanut kernels. Two primary sources of Ca fertilization in peanut are gypsum (CaSO 4 ) and dolomitic lime (CaMg[CO 3 ] 2 +CaCO 3 ). Objectives of this research are to determine whether gypsum, lime, or application of both influences pH, extractable [Ca], [Mg], and [K] in the soil along with nutrient absorption, yield, and total sound mature kernels (TSMK) in peanut pods in irrigated compared to non-irrigated conditions. Experiments conducted in Tifton, GA in 2016 and 2017 evaluated Ca treatments with no supplemental Ca fertilizer, gypsum (330 kg Ca/ha) applied at first bloom, lime (897 kg Ca/ha) applied at planting, and lime (897 kg Ca/ha) applied at planting followed by gypsum (330 kg Ca/ha) applied at first bloom. Irrigating increased soil pH, [Ca] and [Mg] in pods, plus yield and TSMK of peanut. Irrigation also decreased [K] in pods, which was correlated with increased pod [Ca]. Soil pH and soil [Ca], [Mg], and [K] were influenced by fertilizer treatment, along with [Ca] and [Mg] in pods. Applications of lime increased pH and soil [Ca]. Lime also increased soil [Mg] when applied alone, but not when gypsum was also included. Application of gypsum reduced soil [Mg] when applied alone, but not when lime was included. The inclusion of both lime and gypsum reduced soil [K] compared to no application. These results display the competition of cations in soil. In peanut pods, using lime and gypsum increased [Ca] compared to no application, or only lime. However, when only gypsum was used, it reduced [Mg] in pods compared to a lime application or no fertilization. Although Ca fertilization did not affect yield, TSMK was greater when lime followed by gypsum were applied in sequence than where neither were applied in 2016. It is important to realize that applications of Ca can also influence concentrations of other cations important for growth. Peanut growers are encouraged to conduct soil tests to ensure soil [Mg] is not deficient or borderline before choosing to apply gypsum, and may require a supplemental Mg fertilizer if dolomitic lime was not applied.

ABSTRACT Paraquat postemergence (POST) applied is often used to control broadleaf and grass weed species in peanut in the Southeast US. The objective of this study was to determine the effects of POST herbicide tank-mixtures including paraquat on vegetation, yield, and grade for runner-type peanut cultivars under irrigated and non-irrigated conditions. Two separate experiments (irrigated and non-irrigated) were conducted in 2016 and 2017 in Ty Ty and Plains Georgia. Georgia-06G, Georgia-14N, TUFRunner™ ‘511’, and FloRun™ ‘157’ cultivars were evaluated. Herbicide tank-mixtures included paraquat, paraquat plus acifluorfen plus bentazon, paraquat plus acifluorfen plus bentazon plus S -metolachlor, and paraquat plus acifluorfen plus bentazon plus acetochlor. Leaf burn, stunting injury, yield, and grade were evaluated. There were no interactions between herbicide and cultivar for all variables. Paraquat alone resulted in significantly greater foliar injury (3 DAT) than the other herbicide treatments for the irrigated (34 to 16%) and non-irrigated (28 to 15%) studies. Stunting for paraquat alone was noted at 15 and 35% for irrigated and non-irrigated, respectively. Similarly, in both studies, Georgia-06G and TUFRunner™ ‘511’ yielded 10 to 12% greater than Georgia-14N and FloRun™ ‘157’. Overall, the herbicide tank-mixtures did not have a negative effect on yield. With no interactions observed, these herbicide treatments can be used in conjunction with the given runner-type peanut cultivars in either irrigated or non-irrigated conditions without concern for excessive injury or decline in yield or grade.

ABSTRACT Standard row spacing for peanut ( Arachis hypogaea L.) in Georgia is 91-cm in a single-row pattern. Narrower row spacings are often used in crops grown in rotation with peanut. Therefore, converting peanut to narrower row spacing may be easier and beneficial to some growers if cultivars and seeding rates can be identified that can be grown in narrow rows without a reduction in yield and grade. Based on current University of Georgia recommendations, peanut is typically planted at 19 seed/m with a 91-cm row spacing. Using narrower row spacing and constant seeding rates, increased seed costs would be observed. The objectives of this research were to evaluate the influence of cultivars and seeding rate in peanut planted in 76-cm single rows on yield, grade, and tomato spotted wilt virus ( tospovirus ) (TSWV) incidence. Experiments were conducted in 2008, 2010, and 2014 in Tifton, GA and in 2014 at Camilla, GA. Treatments were comprised of three cultivars (varying each year) and three seeding rates (14, 17, and 19 seed/m). Results indicate that pod yield, grade, and TSWV incidence were not affected by seeding rate. Seeding rate significantly influenced plant density where 14, 17, and 19 seed/m seeding rates resulted in 12.1, 13.2, and 13.8 peanut plants/m, respectively equating to a 9% and subsequent 4% increase in plant density as seeding rate increased. Seeding rate did not affect the rate of canopy closure, but cv. Georgia-12Y and TUFRunner ™ ‘511’ had faster canopy closure than Georgia-06G. Peanut grade (total sound mature kernels) was not influenced by seeding rate, but did differ between cultivars. From these results, it can be concluded that 76-cm single-row can provide adequate yield and grade across multiple seeding rates. In addition, this study confirms that cultivar selection is the primary means for reducing TSWV incidence and altering grade in 76-cm peanut production.

ABSTRACT Achieving and maintaining an adequate plant stand is a major priority when making planting and early season management decisions in peanut ( Arachis hypogaea L.). Unpredictable and often extreme weather and high disease pressure in the southeastern United States can contribute to poor emergence and below-optimum plant stands. When plant stand is affected, replanting may be agronomically justified. This study was designed to determine i) the effect of plant stand on pod yield, market grade, and disease incidence in peanut seeded in a twin row pattern, (ii) if replanting is a viable option in a field with a below adequate stand and, iii) the best method for replanting peanut when an adequate stand is not achieved. Field trials were established at two locations in south Georgia in 2012 and 2013 to evaluate peanut production at four plant stands (7.4, 9.8, 12.3, and 14.8 plants/m [total plants/m across both units, or ‘twins' of the twin row pattern) and four replant methods (no replant, destroy the original stand and replant at a full seeding rate, add a reduced rate of seed to supplement the original stand with a single row between the original rows, and supplement with two additional rows with one between and the other next to the original rows). Replanting occurred when the stand had been established, an average of 24 days after initial planting. Pod yield at a stand of 12.3 plants/m was 6.6 and 5.8% greater than at a stand of 7.4 and 9.8 plants/m, respectively, with no benefit from increasing plant stand beyond 12.3 plants/m. Market grade was also maximized at 12.3 plants/m. Disease incidence was unaffected by plant stand. Yield was increased by supplementing an initial stand of 9.8 plants/m in both a single additional row and in two additional rows by 8.3 and 6.6%, respectively. A full replant of the original stand always resulted in lower yield, while grade was slightly increased in the full replant treatment. While an initial stand of 12.3 plants/m was needed in order to maintain yield potential, replanting via supplemental seed addition can recover lost yield at stands below this level.

ABSTRACT The University of Georgia Extension recommendation for optimum plant stand in peanut ( Arachis hypogaea L.) is 13.1 plants/m, although previous work has shown that yield potential can be maintained at lower plant stands. The unpredictable and often extreme weather and the ubiquity of pathogens in the region often contribute to poor emergence and poor plant stands. When plant stand is adversely affected, replanting the field may be a practical option. The objectives of this study were to determine i) the effect of plant stand on yield, grade and disease incidence, ii) at what plant stand peanut gains an advantage from replanting and iii) the best method for replanting peanut when an adequate stand is not achieved. Field trials took place in Plains, GA in 2011, 2012, and 2013; and Tifton, GA in 2012 and 2013 to evaluate peanut production at six plant stands (3.3, 4.9, 6.6, 8.2, 9.8, and 11.5 plants/m, in addition to a 13.1 plants/m control) in combination with three replant practices; i) no replant, ii) destroy the original stand and replant at a full seeding rate, and iii) add a reduced rate of seed to supplement the original stand) in a randomized complete block design. A positive linear trend for yield and a negative linear trend for tomato spotted wilt Tospovirus incidence were discovered as plant stand increased. Yield advantages from replanting occurred via supplemental seed addition to initial stands of 3.3 and 8.2 plants/m. Destroying the initial stand and completely replanting was never beneficial when compared to the other two replant practices. Replanting is warranted via supplemental seed addition at plant stands equal-to or below 8.2 plants/m.

ABSTRACT Peanut ( Arachis hypogaea L.) is a legume and requires nodulation by Bradyrhizobia to convert atmospheric N into a plant usable form. Peanut inoculants place large volumes of viable Bradyrhizobia near the emerging root of the plant to infect it ensuring N-fixation. Peanut seedlings are susceptible to feeding by thrips (Thysanoptera: Thripidae), which transmit Tospovirus leading to tomato spotted wilt (TSW) and can result in yield decline. Phorate is a common in-furrow insecticide used to reduce thrips feeding on the plants, and hence reduce the risk of TSW infection. However, placing phorate in the same furrow with living Bradyrhizobia has raised concerns about phorate potentially reducing efficacy of inoculants. Experiments were designed to test liquid and sterile peat formulations of Bradyrhizobia inoculant with two peanut cultivars in-furrow at planting, both with and without phorate insecticide to determine yield, grade, and growth parameters on peanut. Research was conducted on a non-irrigated loamy sand with no prior history of growing peanut in Tifton, GA in 2013 and 2014. There were no negative effects on peanut yield or grade, or other measured parameters when phorate was included in-furrow with inoculants. Yields with inoculants were equal or greater (up to 32% more) than non-inoculated peanut, and grade was improved (+1.2 to 1.4%) when using the liquid formulation instead of the sterile peat formulation or non-inoculated peanut. Other indicators of improved plant performance using inoculants over non-inoculated plants included the abundance and activity of nodules on the roots and time to row closure (vegetation overlap of bare soil). These data indicate there are no detrimental effects to peanut inoculant when also including phorate insecticide in-furrow.

ABSTRACT Stand establishment has been a challenge for organic peanut production in the Southeastern United States. Field experiments were conducted in 2007 and 2009 in research plots certified for organic production to evaluate the potential of genotype selection, shelling procedure, and seed treatment with Bacillus subtilis to improve stand establishment and seedling emergence rates, reduce incidence of Aspergillus crown rot, and increase seedling biomass. Seed of 15 peanut genotypes were mechanically shelled or hand-shelled, and treated with B. subtilis or untreated prior to planting in early June. Percent stand was estimated for each plot 17–21 days after planting (DAP), and percent seedlings affected by Aspergillus crown rot and plant biomass were estimated 21–24 DAP. Seed treatment significantly affected stand establishment for three genotypes each year, Georgia-01R both years, C-99R and Tifguard in 2007, and C34-24-69 and C724-19-25 in 2009. In all of these cases, the hand-shelled plots had significantly greater stands than the mechanically shelled plots for untreated and/or B. subtilis treated seed. B. subtilis treatment improved stands for two of the mechanically shelled treatments that significantly responded to hand shelling. Despite low incidence, there was a significant reduction of crown rot in the hand-shelled plots compared to the mechanically shelled plots across years and genotypes. The cultivar Georganic, which has been planted to organic peanut systems in Georgia in recent years, was among the genotypes with the lowest seedling establishment rates and biomass. Based on these results, it is recommended that sorting thresholds for damaged seed be higher for seed destined for organic production, and that breeding efforts that include assessments of factors involved in seedling establishment and growth be prioritized.

ABSTRACT Identifying effective weed control regimes for organic peanut is paramount for improving the feasibility of organic production. Tine cultivation is a proven effective method for reducing in-row weed populations in several crops. Field trials were therefore conducted in 2008 and 2009 to assess the effects of tine cultivation combined with sweep cultivation and supplemental hand-weeding on weed control and overall productivity of two peanut cultivars under organic management. Tine cultivation regimes consisted of two frequencies (once per week or twice per week) for three durations (3 wk, 4 wk, or 5 wk). All cultivation treatments were also cultivated with flat sweeps at least once and hand-weeded periodically during the growing season. A non-cultivated, non-weeded control was included for comparison. All cultivation treatments significantly reduced annual grass populations in 2008 and Florida pusley populations both years. Cultivated treatments also resulted in denser plant stands for peanut (9.2 plants/m to 13.2 plants/m) than the non-cultivated control (5.9 plants/m to 7.9 plants/m). Pod yields in cultivated treatments ranged from 3502 kg/ha to 3823 kg/ha and were all significantly greater than yields in the non-cultivated control (1630 kg/ha). Also, net revenues generated by cultivated treatments ranged from ($3333/ha to $3637/ha) and were greater than that of the control ($1795/ha). Cultivation frequency had little effect on weed control and peanut productivity. However, the 4- and 5-wk durations displayed potential for improving peanut yield, grade, and net revenue over the 3-wk duration, especially when annual grass weeds were predominant. Cultivating once weekly for 4 or 5 wk with a tine cultivator, along with at least one sweep cultivation and supplemental hand-weeding, is a viable, economical option for providing adequate weed control and maximizing productivity of organically-managed peanut at current market premiums.