Influence of Gypsum Application on Peanut Yield and Quality

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Pawel J. Wiatrak and David L. Wright, Department of Agronomy, and Jim J. Marois, Department of Plant Pathology, North Florida Research and Education Center, 155 Research Road, University of Florida, Quincy 32351; and David Wilson, Department of Plant Pathology, 109 Plant Science Drive, University of Georgia, Tifton 31793-0748

Abstract

Peanut (Arachis hypogaea L.) yield and quality can be influenced by gypsum application. The objective of this study, conducted in 2001 and 2002, was to evaluate the influence of two gypsum applications (0 and 500 lb/acre) on yields and quality of two peanut cultivars (‘Georgia Green’ and ‘C-99R’). Peanut quality test included sound mature kernels riding screen (SMKRS); sound splits; total sound mature kernels (TSMK); other kernels; and total damage, kernels, and hulls. Peanut yields were higher with gypsum application (4343 lb/acre) compared to the treatment without gypsum application (3926 lb/acre) in one of two years. A lower percentage of TSMK (72 and 74%) and greater percentage of total hulls (23 and 22%) were observed when gypsum was applied in one of two years compared to the treatment without gypsum. Averaged across years, a greater percentage of other kernels was observed with gypsum application (4.6%) than without gypsum (4.0%). Cultivar did not influence peanut yields. The percentage of total damage was greater in 2001 (0.8 and 0.1%) and less in 2002 (0.4 and 1.3%) for Georgia Green than C-99R peanuts, respectively. Greater percentages of SMKRS, TSMK, total kernels, and less sound splits and total hulls were obtained for Georgia Green than C-99R peanuts. The results of this study indicate that gypsum applications may help to increase peanut yields in years with higher yields likely due to adequate availability of Ca in the fruiting zone.

Introduction

Inadequate Ca is a problem for peanut (Arachis hypogea L.) production on soils that are acidic and sandy with low cation exchange capacity (2). Due to Mg deficiency (11) and Al toxicity (16) most soils in the southern Coastal Plain require liming (7) to produce optimum peanut yield. Gascho and Parker (7) reported that for soils with low pH the best yields of peanut have been obtained following application of dolomic lime, which increases soil pH, Ca, and Mg over a period of years. However, overliming can cause Mn deficiency in peanut (10).

Calcium is important for adequate kernel development in peanuts (6). Therefore, in low Ca soils, gypsum is applied at flowering to insure adequate availability of Ca in the fruiting zone (0- to 3-inch soil depth) during pod development (3). Gypsum (CaSO₄·2H₂O) rapidly supplies Ca to the soil profile (12) and is effective in increasing Ca in the subsoil and alleviating Al toxicity (16). Ritchey et al. (13) noted that application of gypsum increases Ca, S, and Mn in the soil and generally reduces soil levels of K and Mg.

High rates of preplant fertilizer in the pegging zone can adversely affect kernel development (6) because excess K and Mg can interfere with Ca absorption by developing pegs (8). Cox and Sholar (5) and Sholar et al. (15) noted that when higher rates of preplant fertilizer are needed, incorporation throughout the soil profile is recommended by applying fertilizer to the previous crop or during the autumn preceding the spring of peanut planting. This approach generally allows movement of fertilizer deeper into the soil profile out of the pegging zone.

Peanut fruits absorb Ca directly from the soil solution; therefore, the concentration of soil solution Ca in the fruiting zone is important in determining the availability of adequate Ca during fruit development (4). Results from lime experiments conducted several decades ago may have limited recommendation value due to the adoption of conservation tillage practices, use of greater amounts of fertilizer, increased irrigation, improved cultivars, and greater removal of Ca and Mg by increased crop yields (7). Jordan et al. (8) suggested that production in reduced tillage systems minimizes the ability to incorporate fertilizers below the pegging zone and that residue on the soil surface could impact movement of calcium sulfate (CaSO₄) into the soil reducing Ca availability to pegs. The purpose of the study was to evaluate the influence of gypsum application on yields and quality of Georgia Green and C-99R peanuts planted using a strip-till system.

Field Trials Using Two Cultivars and Two Gypsum Rates

Field trials with ‘Georgia Green’ and ‘C-99R’ peanuts were conducted in 2001 and 2002 on a Dothan sandy loam (fine, loamy siliceous, thermic Plinthic Kandiudults) at the University of Florida’s North Florida Research and Education Center in Quincy, FL. The experimental area, following winter fallow, was sprayed with glyphosate (Roundup Ultra) at 0.63 lb a.i./acre plus 2,4-D (Weedar 64) at 0.49 lb a.i./acre on 24 April in 2001 and glyphosate at 1.25 lb a.i./acre on 18 and 26 March in 2002. Treatments consisted of two peanut cultivars (Georgia Green and C-99R) and two gypsum applications (0 and 500 lb/acre). Prior to planting peanuts in strip-till, rows were subsoiled with a Brown Ro-till implement (Brown Manufacturing Co., Ozark, AL). Georgia Green and C-99R cultivars were planted using a Monosem air planter (A.T.I. Inc., Lenexa, KS) at 4 seeds per ft of row on 25 May and 10 April in 2001 and 2002, respectively. Each plot was 30 ft long and consisted of six rows (18 ft wide) with 3-ft row spacing.

The site was treated with pendimethalin (Prowl 3.3 EC) at 0.83 lb a.i./acre after planting (pre-emergence) to control weeds. Gypsum (cacium sulfate) was surface-applied at first bloom. Approximately 40 days after emergence, imazapic (Cadre 70 DG) was applied at 0.1 oz a.i./acre. Early (Cercospora arachidicolla S. Hori) and late [Cercosperidium personatum (Berk. & M.A. Curtis) Deighton] leaf spot were controlled with chlorothalonil (Bravo S) at 0.78 lb a.i./acre applied every two weeks beginning 40 days after planting.

Georgia Green peanuts were dug on 16 October and 3 September in 2001 and 2002, respectively, and harvested 2 to 3 days later. The hull-scrape method was used to determine the maturity of peanuts prior to digging. The C-99R cultivar was dug and combined 1 week later than Georgia Green peanuts due to later maturity.

Yield data were collected from the two adjacent middle rows of each plot and dried to 10% moisture before yields were determined. A 2-lb sample was removed from each plot and graded using standards established by the U.S. Federal State Inspection Service. Grades include sound mature kernels riding screen (SMKRS), sound splits, total sound mature kernels (TSMK), other kernels, and total damage, kernels, and hulls. Market grade values are expressed as a percentage of total subsample weight.

The experimental design was a randomized complete block with four replications arranged as a split plot. Peanut yields; SMKRS; sound splits; TSMK; other kernels; and total damage, kernels, and hulls were analyzed using PROC MIXED (14). Years, cultivars, and gypsum applications were considered fixed effects. Blocks and interactions including blocks were assumed to be random effects. The main effect was year, subplot was cultivar, and gypsum application was the sub-subplot. The PROC MIXED procedure of SAS with the LSMEANS PDIFF option was used to compare cultivars and gypsum applications. The difference between means for cultivars and gypsum applications was considered significant at P ≤ 0.05.

Response of Peanut Yield and Quality to Gypsum Application

The interaction of year by gypsum rate was observed for peanut pod yield (Table 1). Gypsum increased peanut yield in 2001 by 417 lb/acre, but did not affect yield in 2002 (Table 2). Previous research suggests inconsistent results with gypsum application to peanuts (1, 2). Peanut yields, averaged across years, were not influenced by cultivar (Table 1). Main et al. (9) reported higher yields for the cultivar C-99R than for Georgia Green at some locations, but Georgia Green yielded higher that C-99R in other locations. Our results indicate that similar yields can be expected from C-99R and Georgia Green peanuts and gypsum application may increase peanut yields in some years.

Table 1. Effect of year, cultivar, and gypsum application on yields, sound mature kernels riding screen (SMKRS), sound splits, total sound mature kernels (TSMK), other kernels, total damage, total kernels, and total hulls at Quincy, FL in 2001 and 2002.

Effect	Yield	SMKRS	Sound splits	TSMK	Other kernels	Total damage	Total kernels	Total hulls
Year (Y)	***	NS	NS	**	NS	*	***	***
Cultivar (C)	NS	***	*	***	NS	NS	***	***
Y x C	NS	NS	NS	NS	NS	***	NS	NS
Gypsum (G)	NS	NS	NS	NS	*	NS	NS	NS
Y x G	*	NS	NS	*	NS	NS	NS	**
C x G	NS	NS	NS	NS	NS	NS	NS	NS
Y x C x G	NS	NS	NS	NS	NS	NS	NS	NS

*, **, *** Significant at the 0.05, 0.01, and 0.001 probability levels, respectively.

Table 2. Peanut yields, total sound mature kernels (TSMK), total hulls, and total damage under two gypsum application rates and two cultivars at Quincy, FL in 2001 and 2002.

Characteristic		2001	2002	2001	2002	2001	2002
Characteristic		Yield (lb/acre)		TSMK (%)		Total Hulls (%)
Gypsum (lb/acre)	0	3926 b†	2785 a	69 a	74 a	26 a	22 b
Gypsum (lb/acre)	500	4343 a	2636 a	69 a	72 b	25 a	23 a
Characteristic		Total Damage (%)
Cultivar	C-99R	0.1 b	1.3 a
Cultivar	Georgia	0.8 a	0.4 b

^† LSMEANS within a column followed by the same letter are not different at P ≤ 0.05.

The SMKRS was influenced by cultivar (Table 1). Averaged across years, greater SMKRS was obtained from Georgia Green than C-99R peanuts (Table 3). These results agree with Main et al. (9) who reported larger percentage of SMKRS for Georgia Green than C-99R peanuts. Gypsum application did not influence the percentage of SMKRS (Table 1). Adams and Hartzog (1) also noted that the SMKRS was generally not affected by gypsum application. However, Adams et al. (2) noted that increases in SMKRS occurred for some cultivars at soil Ca levels higher than that required for maximum yield. Generally, greater percentage of SMKRS may be expected from Georgia Green than C-99R.

Table 3. Influence of cultivar and gypsum application on sound mature kernels riding screen (SMKRS), sound splits, total sound mature kernels (TSMK), other kernels, total kernels, and total hulls at Quincy, FL in 2001 and 2002.

Characteristic		SMKRS	Sound splits	TSMK	Other kernels	Total kernels	Total hulls
Characteristic		%
Cultivar	C-99R	63 b†	7.3 a	70 b	NA	75 b	25 a
Cultivar	Georgia Green	67 a	5.8 b	72 a	NA	77 a	23 b
Gypsum (lb/acre)	0	NA‡	NA	NA	4.0 b	NA	NA
Gypsum (lb/acre)	500	NA	NA	NA	4.6 a	NA	NA

^† LSMEANS within a column followed by the same letter are not different at P ≤ 0.05.

^‡ NA = not applicable.

Cultivars influenced the percentage of sound splits (Table 1). Greater percentage of sound splits, averaged across years, was obtained from C-99R than Georgia Green peanuts (Table 3). However, Main et al. (9) noted that the percentage of sound splits was similar for C-99R and Georgia Green peanuts. The percentage of sound splits was not affected by gypsum application to peanuts (Table 1).

An interaction of year by gypsum application was found for the percentage of TSMK (Table 1). Gypsum application decreased the percentage of TSMK in 2002, but not in 2001 (Table 2). The TSMK was also influenced by cultivar (Table 1). Averaged across years, the percentage of TSMK was greater from Georgia Green than C-99R peanuts (Table 3). In contrast, Main et al. (9) reported either similar or greater TSMK for C-99R than Georgia Green peanuts.

The percentage of other kernels was influenced by gypsum application (Table 1). Greater percentage of other kernels was obtained with gypsum application compared to the treatment without gypsum application (Table 3). Cultivar did not influence the percentage of other kernels (Table 1). Main et al. (9) reported similar percentage of other kernels for both peanut cultivars in three tests over two years; however, this percentage was lower from C-99R than Georgia Green in one location.

A year by cultivar interaction was found for the percentage of total damage (Table 1). The percentage of total damage was greater for Georgia Green than C-99R peanuts in 2001 and greater for C-99R than Georgia Green peanuts in 2002 (Table 2). Gypsum application did not influence the percentage of total damage (Table 1). Generally, the percentage of total damage for C-99R and Georgia Green peanuts varies across years.

The interaction of year by gypsum application was observed for the percentage of total hulls (Table 1). Gypsum application increased the percentage of total hulls in 2002, while the percentage of total hulls was not influenced by gypsum application in 2001 (Table 2). The percentage of total hulls was also influenced by cultivar (Table 1). Averaged across years, greater percentage of total hulls was obtained from C-99R than Georgia Green peanuts (Table 3). These results indicate that the percentage of total hulls varies across years and may be greater from C-99R than Georgia Green peanuts.

Conclusion

Gypsum application increased yields and the percentage of total hulls, and decreased the percentage of TSMK in one out of two years. Averaged across years, gypsum application increased the percentage of other kernels. Peanut yields were not influenced by cultivar. The percentage of total damage was greater for Georgia Green in the first year and greater for C-99R peanuts in the second year of the study. The results of this study indicate that under strip-till management systems gypsum application may help to increase peanut yields in years with high potential yield by increasing Ca availability in the fruiting zone.

Acknowledgment

This research was supported by the Florida and Georgia Agricultural Experiment Stations, and approved for publication as Journal Series No. R-10012.

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