Can Peg Strength Be Used as a Predictor for Pod Maturity and Peanut Yield?

Mesocarp hull color is the current standard to estimate digging date and peanut (Arachis hypogaea, L.) maturity with acceptable yield and grade. Subjectivity of pod color and pod placement on a color chart may give a false indication of when to dig peanuts. The objective was to determine if peg strength could be used to predict pod maturity, digging date, and resultant peanut yield. Peanut peg strength was collected for two years (2011 and 2012) on three peanut cultivars (Georgia-06G, Georgia-09B, and Tifguard), at multiple plant dates (2012 only) and multiple harvest dates to determine the relationship between peg strength versus pod maturity, peanut loss, and peanut yield. Peg strength was determined using an electronic force gage that would measure peak force. Average peg strength was different for all three cultivars with Georgia-06G having the greatest average peg strength followed by Georgia-09B, and Tifguard. In general, peanut yields were greater at early plant and harvest dates and decreased with time. Conversely, peanut pod loss was lower with early plant and harvest dates but increased with later harvest dates. There was a strong positive linear relationship between peg strength and peanut yield for each cultivar. However, there was a relatively small difference with peg strength values between the maximum and minimum peanut yield. There was no relationship between peg strength and mesocarp color (pod maturity, R2 = 0.007). Small differences in peg strength and the non-relationship between peg strength and pod maturity implies: 1) a large sample size would be needed to predict peanut yield, 2) the large sample size would increase time and manpower to determine average peg strength values, and 3) peg strength was not a valid criteria to determine pod maturity or predict digging date. Overall, peg strength may be useful to describe cultivar characteristics but may not be sufficiently robust to predict pod maturity digging date, or peanut yield.