Manganese (Mn) is an essential element needed for peanut (Arachis hypogaea L.) growth and development (Gascho and Davis, 1995) serving as a cofactor in kinase and transferase enzymatic reactions in plants (Horst, 1986). Deficiencies of Mn are often associated with production on high pH soils (Gascho and Davis, 1995) but can be corrected with Mn-containing fertilizers applied topically (Gascho and Davis, 1995).
Introduction
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 (Jordan et al., 2018). Research conducted in Virginia, on virginia type peanut, in the 1980's indicated that higher seeding density (215 thousand seeds/ha) produced significantly (P<0.01) higher yield and economic value than lower seeding density (144 thousand seeds/ha) (Mozingo and Coffelt, 1984). Similarly, studies on runner type peanut had positive relationships between seeding density and pod yield. For example, when increasing seeding density from 10 to 20 seeds/m, Sorenson et al. (2004) reported 8.5% pod yield increase and Sconyers et al. (2007) showed 16% higher yields when planting 22.6 seeds/m compared to 12.5 seeds/m. Sarver et al. (2016) reported that increasing seeding density from 3.3 plants/m to 13.1 plants/m increased pod yield from 5200 kg/ha to 6500 kg/ha, and decreased Tomato spotted wilt virus (genus Tospovirus; family Bunyaviridae) (TSWV).
Peanut yield response to seeding density is cultivar dependent in many crops including corn (Zea mays L.) (Nafziger, 1994), soybean [Glycine max (L.) Merr.] (Buerlein, 1988), and peanut (Sullivan, 1991). The new available virginia type cultivars showed improved yield, i.e. in Virginia, average state yield during the 1980's was 2976 kg/ha and during the last decade 4560 kg/ha, (USDA, 2019); and biomass (Simmons, personal communication) than the old cultivars. Therefore, to produce optimally, the new cultivars may require more nutrients and water, which could be supplied at no additional costs by decreasing plant population to make more resources available to individual plants. If newly released cultivars can produce similar yields with less plants per hectare, reducing the seeding density could greatly lower the cost incurred by growers in the Virginia-Carolina region.
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. Jordan et al. (2003) showed that digging within the optimum harvest maturity window (Williams and Drexler, 1981) did not affect yield or grade. Literature has consistently reported, however, that digging either too early or too late produced negative effects on peanut yield and quality (Mozingo et al., 1991; Wright and Porter, 1991; Jordan et al., 1998). For example, digging peanut two wk early reduced yield by 15% (Wright and Porter, 1991); and delayed digging caused decrease to both pod yield and gross value, with economic loss as high as $500/ha (Mozingo et al., 1991; Jordan et al., 1998). However, in North Carolina, early maturing cultivars responded differently to digging with some being more stable in terms of yield and economic value over digging dates than others (Jordan et al., 1998). Research is limited with respect to defining response to digging date of more recently released virginia market type cultivars. Generally, virginia market types require 135 to 155 DAP to reach maturity, while runners may need over 155 DAP (Balota et al., 2018).
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.
Acknowledgements
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.
Literature Cited
Balota M. Phipps P. 2013. Comparison of Virginia and runner-type peanut cultivars for development, disease, yield potential, and grade factors in eastern Virginia. Peanut Sci. 40: 15- 23.
Balota M. Isleib T.G. Oakes J. Anco D. 2017. Peanut Variety and Quality Evaluation Results. I. Agronomic and Grade Data. Virginia Cooperative Extension.