Agronomy Journal 93:232-236 (2001)
© 2001 American Society of Agronomy
PEANUT
Peanut Response to Prohexadione Calcium in Three Seeding Rate–Row Pattern Planting Systems
David L. Jordan,
Joshua B. Beam,
P.Dewayne Johnson and
Jan F. Spears
Dep. of Crop Sci., North Carolina State Univ., Raleigh, NC 27695-7620
Corresponding author (david_jordan{at}ncsu.edu)
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ABSTRACT
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Peanut (Arachis hypogaea L.) in the USA is generally grown in single rows spaced 91 to 102 cm apart. Research suggests that pod yield can be increased by growing peanut in twin rows (18–23 cm spacing) on beds spaced 91 to 102 cm apart. Prohexadione Ca (Ca salt of 3,5-dioxo-4-propionylcyclohexanecarboxylic acid) increases row visibility and in some instances increases pod yield and improves market grade factors. Research was conducted to determine response of peanut grown in three seeding rate–row pattern planting systems (single rows at a seeding rate of 120 kg ha-1 or twin rows spaced 18 cm apart on beds spaced 91 cm apart at seeding rates of 145 and 190 kg ha-1) to prohexadione Ca applied at 50% row closure. Row visibility increased and main stem height was shorter at the end of the season when prohexadione Ca was applied in most environments and for most seeding rate–row pattern combinations when compared with nontreated peanut. Pod yield and gross economic value increased 160 kg ha-1 and $96 ha-1, respectively, when prohexadione Ca was applied irrespective of the seeding rate–row pattern combination or environment. Prohexadione Ca also increased the percentage of extra large kernels (% ELK) but did not affect percentages of sound mature kernels (SMK), other kernels (OK), sound splits (SS), or total sound mature kernels (TSMK). Seeding rate–row pattern combination affected pod yield, market grade, and gross economic value although a consistent trend was not apparent.
Abbreviations: % ELK, percentage of extra large kernels • % OK, percentage of other kernels • % SMK, percentage of sound mature kernels • % SS, percentage of sound splits • % TSMK, percentage of the total SMK
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INTRODUCTION
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PEANUT IN THE USA is generally grown on single rows spaced between 91 to 102 cm apart (Sholar et al., 1995). However, some growers seed peanut in twin rows spaced 18 to 23 cm apart on 91 to 102-cm beds. This approach has become popular in the southeastern USA where tomato spotted wilt tospovirus is a major pest (Baldwin et al., 1998). High plant populations, either through increased seeding rates on single rows or planting on twin rows, reduce infection by tomato spotted wilt tospovirus (Baldwin et al., 1998). The mechanism of reduced infection is not completely understood. Research (Mozingo and Coffelt, 1984; Sullivan, 1991) in the Virginia–Carolina area suggests that higher yields may be possible when peanut is seeded in twin rows compared with seeding in single rows in the absence of tomato spotted wilt tospovirus. However, Kvien and Bergmark (1987) reported no increase in yield of the peanut cultivar Florunner when planted in twin-row patterns compared with single rows in the southeastern USA. This research was conducted before widespread infection of tomato spotted wilt tospovirus. Hauser and Buchanan (1981) suggested that twin-row patterns offered advantages in weed control by covering row middles more quickly than single rows.
Excessive vine growth of some virginia market types typically occurs in the Virginia–Carolina production region. The digging efficiency frequently decreases when rows are difficult to distinguish, and the prevalence of disease often increases when vine growth limits air movement within the canopy (Bauman and Norden, 1971; Gorbet and Rhodes, 1975; Henning et al., 1982; Sholar et al., 1995). Seeding peanut at higher plant populations, either by increasing the seeding rate or by planting in twin rows, may increase vine growth, which could make digging and inverting less efficient. Daminozide [butanoic acid mono (2,2-dimethylhydrazide)] was used to manage excessive vine growth in peanut, but it is no longer commercially available to manage excessive vine growth in peanut. However, prohexadione Ca has shown potential as a replacement for daminozide (Culpepper et al., 1997; Mitchem et al., 1996). Research suggests that prohexadione Ca increases the pod yield, % ELK, and gross value of peanut in certain situations (Culpepper et al., 1997; Mitchem et al., 1996). The response was dependant upon interactions among cultivars, the amount of vegetative growth, and environmental conditions. Prohexadione Ca may reduce vine growth and allow producers to seed peanut at higher rates; it may also increase the utility of seeding in twin rows or better utilize some cultivars.
Most research comparing twin-row seeding with single rows has been conducted with cultivars that are no longer grown on significant hectares. Evaluating the response of cultivars that are currently grown to twin-row seeding would be advantageous. Determining how these cultivars respond to prohexadione Ca would help in establishing the utility of this plant growth regulator. Therefore, research was conducted to compare the vegetative response, pod yield, market grade factors, market value, and gross value of virginia market type peanut as influenced by a seeding rate–row pattern combination and to determine if prohexadione Ca alters the peanut response to these seeding rate–row pattern planting systems.
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Materials and methods
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The experiment was conducted in northeastern North Carolina from 1997 through 1999 in commercial fields and at the Peanut Belt Research Station located near Lewiston, NC and the Upper Coastal Plain Research Station located near Rocky Mount, NC. The location and year (referred to as environment), soil series, cultivar, irrigation, and rainfall are presented in Table 1 along with the dates of planting, prohexadione Ca application, digging, and combining. The cultivars NC-V 11 and NC 12C are among the most widely grown peanut cultivars in North Carolina (Spears, 2000). Peanut was planted in conventionally prepared seedbeds at all locations. Cultural and pest management practices were based on Cooperative Extension Service recommendations for the region. The plot size was 4 rows wide by 10 to 15 m long.
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Table 1 Locations and years, soil series and texture, cultivars, irrigation and rainfall, and dates of planting, prohexadione Ca applications, digging, and harvesting
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Peanut was planted in single rows spaced 91 cm apart on elevated beds at a seeding rate of 120 kg ha-1 or in twin rows at seeding rates of 145 and 190 kg ha-1. The twin-row patterns consisted of two rows spaced 18 cm apart on elevated beds with the centers of the twin rows spaced 91 cm apart. Prohexadione Ca at 140 g a.i. ha-1 was applied at 50% row closure (vines touching from adjacent 91-cm beds), followed by a repeat application 2 to 3 wk later using a CO2-pressurized backpack sprayer that was calibrated to deliver 145 L ha-1 at 140 kPa (Table 1). A 30% urea ammonium nitrate solution (vol./vol.) was applied at 2.3 L ha-1 with prohexadione Ca. A nonprohexadione Ca control was included for each seeding rate.
The experimental design was a split plot with four replications. Combinations of seeding rates and row patterns (referred to as seeding rate–row pattern combination) served as main plots while prohexadione Ca treatment served as subplots. Visual estimates of the canopy development were recorded in mid-September using a scale of 1 to 10 where 1 = flat canopy with no row definition and 10 = well-defined, triangular-shaped peanut rows (Mitchem et al., 1996). The main stem height was recorded in mid-September in experiments conducted during 1998 and 1999. The pod yield was determined from the center two rows of each plot. A 500-g sample was removed from each plot at harvest and used to determine the % ELK, % SMK, % OK, % TSMK, and the market value ($ kg-1) using USDA market grade factors for farmer stock peanuts. The gross value ($ ha-1) was determined as the product of the pod yield and market value.
Data were subjected to combined analyses of variance for the seven environments, three seeding rate–row pattern combinations, and two prohexadione Ca treatments (Table 2). Means of the significant main effects and interactions were separated using Fisher's protected LSD test at P = 0.05.
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Table 2 Analyses of variance for main effects and interactions of environment, prohexadione Ca, and seeding rate–row pattern for row visibility, main stem height, pod yield, gross economic value, percentages of ELK, SMK, SS, and TSMK, and market value
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Results and discussion
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The interaction of the environment x prohexadione Ca x seeding rate–row pattern combination was significant for row visibility (Table 2). When analyzed by environment, the interaction of prohexadione Ca x seeding rate–row pattern combination was significant for row visibility at Tyner in 1997, Conetoe and Hobbsville in 1998, and at Lewiston in 1999 (Table 3). Main effects of the seeding rate–row pattern combination and prohexadione Ca also were significant at Tyner in 1998 while only the main effect of prohexadione Ca was significant at Lewiston in 1998 and at Rocky Mount (data not shown). Although variation in the row visibility was noted among the seeding rate–row pattern combination and prohexadione Ca treatment, prohexadione Ca increased the row visibility when peanut was seeded at 120 kg ha-1 in single rows at Tyner in 1997, at Conetoe and Hobbsville in 1998, and at Lewiston in 1999 (Table 3). In these experiments, improvement in the row visibility by prohexadione Ca in twin-row seeding was noted in three experiments (145 kg ha-1 seeding rate) or in one experiment (190 kg ha-1 seeding rate). With the exception of Hobbsville and Tyner in 1998, the row visibility did not differ among seeding rates when prohexadione Ca was not applied (Table 3). Considerable variation was noted in the row visibility among seeding rate–row pattern combinations when prohexadione Ca was applied. The relationships among cultivars, rainfall or irrigation, and the response of peanut to prohexadione Ca at the various seeding rate–row patterns were not readily apparent. At Lewiston and Tyner in 1998 and at Rocky Mount, prohexadione Ca increased the row visibility irrespective of the seeding rate–row pattern combinations (data not presented). Previous research (Culpepper et al., 1997) suggests that the enhancement of row visibility by prohexadione Ca can vary among cultivars or with the same cultivar grown under different environmental or edaphic conditions.
The main stem height was affected independently by prohexadione Ca and the seeding rate–row pattern combination (data not presented). Although the interaction of the environment x seeding rate–row pattern combination x prohexadione Ca was not significant, the interactions of the environment x prohexadione Ca and the environment x seeding rate–row pattern combination were significant (Table 2). When pooled over the seeding rate–row pattern combinations, the late-season main stem height was shorter in four of six environments when prohexadione Ca was applied. Other research (Beasley et al., 1998; Jordan and Swann, 1999) has demonstrated that the main stem height is often shorter following the application of prohexadione Ca when compared with nontreated peanut. The greatest magnitude of height differential was noted at Lewiston during both years and at Rocky Mount (Table 4). The cultivar NC 12C, which exhibits excessive vine growth and a relative tall main stem, was grown at Lewiston. At Rocky Mount, where NC-V 11 was planted, the conditions in 1999 were favorable for excessive vegetative growth (Table 1). In contrast, the conditions at Tyner in 1997 and at Hobbsville and Conetoe in 1998 were relatively dry (Table 1). Under dry conditions, excessive vegetative growth would not be expected, and this may help partially explain the shorter main stems and fewer differences among prohexadione Ca treatments in these environments.
The effect of the seeding rate–row pattern combination on the main stem height was more difficult to explain than the effect of prohexadione Ca. When pooled over prohexadione Ca treatments, the seeding rate–row pattern combination had no effect on the main stem height at Lewiston in 1998 (Table 4). In contrast, the main stem height differed among seeding rate–row pattern combination in the other environments. In three environments, there was no difference in the main stem height when comparing peanut in twin rows seeded at 145 kg ha-1 to peanut in single rows seeded at 120 kg ha-1 (Lewiston during both years and at Rocky Mount). At Tyner and Hobbsville in 1998, the main stems were taller when peanut was planted in twin rows at 145 kg ha-1 compared with peanut seeded in single rows at 120 kg ha-1. The opposite response was noted at Conetoe in 1998. The main stems were taller in four of six environments when peanut was planted in twin rows at a seeding rate of 190 kg ha-1 compared with the other seeding rate–row pattern combinations (Table 4). This most likely resulted from greater competition among plants that were grown under higher plant populations.
Although the interaction of the environment x prohexadione Ca x seeding rate–row pattern combination was not significant for the pod yield or gross value ($ ha-1), the main effects of prohexadione Ca and the interaction of the environment x seeding rate–row pattern combination were significant for both parameters (Table 2). When pooled over the environments and seeding rate–row patterns, prohexadione Ca increased the pod yield and gross value by 160 kg ha-1 and $96 ha-1, respectively (data not presented). Other research (Culpepper et al., 1997) has shown increased pod yield and gross value when prohexadione Ca was applied to peanut when compared with nontreated peanut. Beasley et al. (1998) reported no interaction of prohexadione Ca application and four runner market-type peanut cultivars grown in single vs. twin rows.
The seeding rate–row pattern combination did not affect the pod yield at Lewiston or Tyner during 1998 (Table 5). However, in three of six environments (Lewiston in 1999, Tyner in 1997, and Hobbsville in 1998), the pod yield was increased when peanut was planted in twin rows at 145 kg ha-1 compared with single row planting at 120 kg ha-1. Sullivan (1991) reported that the pod yield of the cultivar NC-V 11 increased 190 kg ha-1 when peanut was seeded in twin rows compared with single-row seeding. The peanut seeding rate in that study was 25% higher in the twin-row pattern compared with the single rows. In our study, seeding the cultivar NC-V 11 in twin rows at 145 kg ha-1, rather than in single rows at 120 kg ha-1 (18% higher seeding rate), resulted in a 380 to 480 kg ha-1 yield increase in three studies (Tyner in 1997 and Coneote and Hobbsville in 1998) (Table 5). The pod yield of this cultivar did not differ among these seeding rate–row pattern combinations at Tyner in 1998 or at Rocky Mount. Increasing the seeding rate from 145 to 190 kg ha-1 did not increase the pod yield in any environment and actually reduced the pod yield at Rocky Mount.
There was no difference in the gross value among seeding rate–row pattern combinations at Lewiston during 1999, at Tyner in 1998, or at Rocky Mount (Table 6). At Tyner in 1997 and at Hobbsville, the gross value was higher when peanut was planted in twin rows at 145 kg ha-1 compared with single-row seeding at 120 kg ha-1. However, the opposite response occurred at Lewiston in 1998. There was no advantage in gross returns by increasing the seeding rate to 190 kg ha-1 in twin-row plantings in five of six experiments. The decrease in the gross return when peanut was seeded at 145 kg ha-1 at Lewiston in 1998 could not be explained.
The main effect of prohexadione Ca was significant for the % ELK while all of the other main effects and interactions were not significant for this parameter (Table 2). When pooled over the experiments and seeding rate–row pattern combinations, the % ELK increased from 47 to 50% (data not presented). Culpepper et al. (1997) reported that prohexadione Ca increased the % ELK and % TSMK. A higher % ELK suggests that peanut was maturing more quickly following prohexadione Ca application or that mature pods were staying on the plant longer. The mechanism of increased % ELK of harvested farmer stock peanut has not been elucidated. Although Mitchem et al. (1996) reported that prohexadione Ca increased the % ELK, it did not affect the percentages of SMK or TSMK.
The seeding rate–row pattern combination did not affect the % ELK (data not presented). The main effects and interactions of the environment, prohexadione Ca, and seeding rate–row pattern combinations were not significant for the percentages of SMK, SS, OK, and TSMK or for the market value ($ kg-1). Previous research by Sullivan (1991) suggested that seeding in single rows vs. twin rows did not affect the market grades of the cultivars NC 7, NC 9, NC 10C, and NC-V 11. In these studies, the seeding rate in twin rows was 25% higher than the seeding rate in single rows.
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Summary
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The results from these studies suggest that while variable response may occur to the increased row visibility and decreased main stem height caused by prohexadione Ca, the increased pod yield, % ELK, and gross value were consistent across the seven environments involved in this study. These seven environments consisted of differences in management practices such as cultivar selection, irrigation, and digging and harvesting conditions as well as environmental conditions such as rainfall. The yield response to prohexadione Ca has been inconsistent in other studies (Beasley et al., 1998; Culpepper et al., 1997; Jordan and Swann, 1999).
The response of peanut to the seeding rate–row pattern combination was more variable than the response to prohexadione Ca. While seeding at 145 kg ha-1 in twin rows increased the yield over single rows seeded at 120 kg ha-1, this response was not consistent across all environments. These data also suggest that increasing the seeding rate in twin rows from 145 to 190 kg ha-1 is of no economic value.
The increase in the gross value by prohexadione Ca was $96 ha-1. Although this was a significant increase, the cost of both prohexadione Ca and application (two applications in this experiment) will most likely determine the utility. However, the benefits of enhanced row visibility at the farm level could not be documented in this small-plot research. The impact of prohexadione Ca on pest reaction has not been documented nor has the mechanism of enhanced yield been elucidated. Further research in these areas may assist in determining the overall utility of prohexadione Ca. While twin-row seeding was advantageous in some of the experiments, there was no clear trend providing a general recommendation on twin-row seeding vs. seeding in single rows. These data, however, suggest that seeding rates that exceed 145 kg ha-1 in twin-row patterns most likely will be of no economic benefit.
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ACKNOWLEDGMENTS
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BASF Corporation and the North Carolina Peanut Growers Association provided financial support. Appreciation is expressed to Chowan Farms, Jimmy Worsley, Douglas Baker, the Upper Coastal Plain Research Station, and the Peanut Belt Research Station for assistance with these studies. Carl Murphy, Brenda Penny, Michael Williams, Lewis Smith, and James Pearce provided technical support.
Received for publication March 11, 2000.
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REFERENCES
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- Baldwin, J.A., J.P. Beasley Jr., S.L. Brown, J.W. Todd, and A.K. Culbreath. 1998. Yield, grade, and tomato spotted wilt incidence of four peanut cultivars in response to twin row versus single row planting patterns. Proc. Am. Peanut Res. Educ. Soc. 30:51.
- Bauman, R.W., and J.A. Norden. 1971. Effect of growth regulators on vegetative and reproductive characteristics of six peanut genotypes. J. Am. Peanut Res. Educ. Assoc. 3:75–90.
- Beasley, J.P. Jr., G.E. MacDonald, C.K. Kvien, and S. Rushing. 1998. Response of four runner peanut cultivars to prohexadione calcium plant growth regulator. Proc. Am. Peanut Res. Educ. Soc. 30:53.
- Culpepper, A.S., D.L. Jordan, R.B. Batts, and A.C. York. 1997. Peanut response to prohexadione calcium as affected by digging date. Peanut Sci. 24:85–89.
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- Henning, B.J., A.H. Allison, and L.D. Tripp. 1982. Cultural practices. p. 123–138. In H.E. Pattee and C.T. Young (ed.) Peanut science and technology. Am. Peanut Res. and Educ. Soc., Yoakum, TX.
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ABSTRACT
INTRODUCTION
