First author: Superintendent, Eastern Virginia Agricultural Research and Extension Center, Virginia Tech, Warsaw, VA 22572; 2Second author: Associate Professor, Tidewater Agricultural Research and Extension Center, Virginia Tech, Suffolk, VA 23437; Third and fourth authors: Professor and Research Technician, Department of Crop and Soil Sciences, North Carolina State University, Raleigh, NC 27695; Fifth author: Assistant Professor, Department of Plant, Soil, and Agricultural Systems, Southern Illinois University, Carbondale, IL 62901
Large-seeded virginia market type peanut (
Large seeded virginia type peanut is the preferred market type grown in the Virginia-Carolina (VC) region. The price of certified seed is approximately $2.05/kg making the cost of $277/ha, a significant input cost when planting the recommended seed density of 140 kg/ha or 200 thousand seeds/ha (
Peanut yield response to seeding density is cultivar dependent in many crops including corn (
Due to the indeterminate growth habit and the effect of weather on plant development, i.e., dry seasons delay while hot summers rush maturity, determining the optimum digging date is essential for maximizing yield, quality, and the economic return.
The objective of this research was to determine the effect of seeding density and digging date on yield, market grade characteristics, and economic return of more recently released virginia market type peanut cultivars.
Field studies were conducted at four site-yr in 2016 and 2017 at the Tidewater Agricultural Research and Extension Center in Suffolk, VA (36.6658280 N, -76.7292940 W), and the Peanut Belt Research Station in Lewiston-Woodville, NC (36.1322040 N, -77.1690820 W). In 2016, experiments at Suffolk were conducted on a Suffolk loamy sand (Fine-loamy, siliceous, semiactive, thermic Typic Hapludults), while soils at Lewiston-Woodville were on Norfolk sandy loam (Fine-loamy, kaolinitic, thermic Typic Kandiudults). In 2017, experiments at Suffolk were conducted on Eunola loamy fine sand (Fine-loamy, siliceous, semiactive, thermic Aquic Hapludults) while at Lewiston-Woodville the experiment was conducted on the same Norfolk sandy loam soil. These soils are representative of soils across the region where peanut is grown. Plot size was 2 rows (91-cm spacing) by 10.7 m in length. Peanut was planted in conventionally-tilled, raised seedbeds in both years of the experiment. Agronomic and pest management practices other than the specific treatments compared in these experiments were administered uniformly across the entire test area based on Cooperative Extension recommendations for North Carolina and Virginia (
The experimental design was a split-factorial plot arranged in a randomized complete block design with four replications. The main plots were the digging dates including early (130 DAP), physiological maturity (140 DAP), and late (150 DAP) digging. Sub-plots consisted of a factorial arrangement of seeding densities (109, 143, 180, and 200 thousand seeds/ha) and cultivars (Bailey, Sullivan, and Wynne). Plots were planted using a two-row Cole planter on May 19 in Suffolk and on May 16 in Lewiston-Woodville in 2016, and on May 8 in Suffolk and on May 18 in Lewiston-Woodville in 2017. All pertinent information on planting and digging dates are provided in
Planting and digging dates for three Virginia type peanut cultivars, and corresponding days after planting (DAP), by year and location.
Cumulative rainfall and growing degree days (GDD)a by year and location for the growing cycles of 130, 140, and 150 days after planting (DAP).
Harvest was conducted approximately seven to ten d after digging. Pod yield was determined from the plot weight adjusted to 7% moisture and percent foreign material in a 500 g subsample. The same sub-sample was used for grade evaluations. First, fancy pod percentage, pods that do not pass 13.5 mm × 76.2 mm spacing set on the pre-sizer, was determined. Then, pods were shelled and kernels were sorted by size including extra-large kernels (ELK), kernels passing the larger screen but did not pass a 25.4 mm (1-in) × 8.5 mm (21.5/64) screen; mediums, kernels passing the larger screens but did not pass a 25.4 mm × 7.1 mm (18/64-in) screen; and number 1's, kernels passing the larger screens but did not pass a 25.4 mm × 5.9 mm (15/64-in) screen. Lastly, percent of sound mature kernels (SMK) was determined as the sum of ELK, mediums and number 1's. (USDA, 2019). Farmer stock grade characteristics were used to calculate the crop economic value ($/ha) using the USDA Agricultural Marketing Service approach (USDA, 2019).
The PROC Mixed procedure in SAS (
To determine which seeding density was the most economical, a cost analysis was performed. Seed weight (kg/ha) was calculated for each individual seeding density. Since there was no interaction with cultivar, seed weight was averaged across the three cultivars. Seed price was $0.38/kg (
Gross return ($/ha) was also calculated for each seeding density using a selling price of $0.09/ha (
Economic return for seeding density was calculated by subtracting the total seed cost from the gross return, and it was used to determine which seeding density was most profitable. A sensitivity analysis was performed in which the selling price was increased in increments of 10% until the highest yielding seeding density produced the highest economic return. In addition, we decreased seed cost in increments of 10% until the highest yielding seeding density produced the highest economic return. Finally, the seed cost was dropped simultaneously with increasing price until the highest yielding seeding density produced the highest economic return.
Peanut requires at least 600 mm precipitation from planting to physiological maturity (
Peanut is known to require 2200 GDD from planting to physiological maturity, but new cultivars are increasingly earlier maturing than older cultivars. For example, virginia market type cultivars developed at the turn of the century needed 1800 GDD to mature, in comparison with 2500 GDD needed by cultivars developed prior to that (
Main effect of site-year, cultivar, seeding density and digging date, and the interaction of site-year × digging date × cultivar were significant for pod yield at
Analysis of variance for peanut pod yield, economic value, percentage of extra-large kernels (ELK), sound mature kernels (SMK), and fancy pods.
Peanut pod yield response to seeding density across all site-years, cultivars and digging dates. Means with the same letter are not significantly different from each other according to Fisher's protected LSD test at P ≤ 0.05.
At Suffolk in 2016, among the three cultivars, there was no significant difference for pod yield between the 130 and 140 DAP digging dates, i.e. cultivar average was 4900 kg/ha for 130 DAP and 5090 kg/ha for 140 DAP; but the 150 DAP digging date had the lowest pod yield for all cultivars, 3890 kg/ha (
Effect of site-year, digging date, and cultivar on pod yield.
At Lewiston-Woodville in 2016, the 140 DAP digging date produced significantly greater pod yield for all three varieties than 130 and 150 DAP digging dates (
For grade characteristics, ELK, SMK, and fancy pods, main effects were significant for site-year, cultivar and digging date, but not for the seeding density. With the exception of digging date × cultivar for the ELK and site-year × digging date × cultivar interaction for all grades, the other interactions were not significant (
Effect of digging date and peanut cultivar on extra-large kernels (ELK).
Similarly, digging at 140 DAP resulted in the highest SMK for all three varieties at Suffolk in 2016 and Lewiston in 2017; but in other site-years, SMK was cultivar dependent (
Effect of site-year, digging date, and peanut cultivar on sound mature kernels (SMK).
While ELK and SMK are major grade factors in calculation of the gross economic return, fancy pod content is not. However, for in-shell product commercialization, fancy pod content is important. Interestingly, and unlike for the ELK and SMK, fancy pods were highest when digging early, at 130 DAP, compared with later digs (
Effect of site-year, digging date, and peanut cultivar on percentage of fancy pods.
ANOVA for the economic value followed a similar pattern with pod yield, with main effect of site-year, cultivar, seeding density and digging date, and the interaction of site-year × digging date × cultivar being significant at
Effect of site-year, digging date, and peanut cultivar on peanut economic value.
This study showed that the highest seeding density of 200 thousand seeds ha−1 produced the highest yield (
Economic return for seeding density in peanut. Seed cost represents the cost to the grower, and yield price is the selling price after harvest from
Our results indicated that increasing the seeding density from 109 thousand seeds/ha to 200 thousand seeds/ha increased the pod yield across all site-years, similarly for all cultivars. However, the seeding density producing the highest yield did not result in the highest economic return, as the increase in yield was not enough to compensate for the increased seed cost. Instead, the 143 thousand seeds/ha seeding density ensured the greatest economic return for the farmer; this agrees with the current recommendations for peanut production in Virginia. According to our results, the optimal time to dig the Virginia market type peanut cultivars currently grown in the VC region is at 140 DAP. This is because these cultivars appear to need at least 1400 GDD and no more than 1600 cumulative GDD to reach optimum maturity and, therefore, maximum pod yield. However, the decision on when to dig should be monitored on a field-to-field basis as not just temperature, but other factors may affect yield, such as the amount of precipitation at or right before digging.
This work was supported with funding from the National Peanut Board, North Carolina Peanut Growers Association, Virginia Peanut Board, and Virginia Crop Improvement Association. Appreciation is expressed to staff at both research stations for technical assistance with this research.