The objective of this research was to determine if bulk density of in-shell peanuts, called pod bulk density can be used to accurately estimate farmer stock grade factors such as total sound mature kernels and other kernels. Physical properties including pod or in-shell bulk density, pod size, and kernel size distributions are measured as part of the cooperative Uniform Peanut Performance Tests (UPPT). Using physical property data from three years (2002–2004) of UPPT, analysis of variance were performed to determine the effect of bulk density, location, year, peanut type, and cultivar on percent total sound mature kernels (TSMK), other kernels (OK), and farmer stock value (FSV). Results indicated that all effects in the model were significant in predicting both TSMK and FSV and accounted for most of the variation (R2=0.80). Linear regressions of the UPPT (2002–2004) data (with pod bulk density as a single factor) showed that TSMK and FSV increased as pod bulk density increased with poor R2 values (R2=0.2). A second set of data collected during the 2005 peanut harvest by Federal State Inspection Service (FSIS) had similar results. Location and peanut type were highly significant factors in the variation of TSMK, OK, and FSV. Overall correlation of grade factors with pod bulk density, location, and type was poor (R2>#x3c;0.5). Based on these data, pod bulk density cannot be used to accurately estimate TSMK and OK for marketing farmer stock peanuts. Observed pod bulk density averaged for UPPT (all years) and FSIS was 316 kg/m3 for runner, 427 kg/m3 for spanish, 491 kg/m3 for valencia, and 258 kg/m3 for virginia peanuts.
The farmer stock grading system was developed and implemented during the 1960's (
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Small grains are typically marketed based solely on bulk density or test weight, moisture content, and dockage or foreign material.
The objective of this research was to determine if pod bulk density can be used to accurately estimate farmer stock grade factors such as total sound mature kernels (TSMK), other kernels (OK), total kernels (TK=TSMK+OK), and farmer stock value (FSV) for the purpose of marketing.
A known mass of cleaned pods were poured into an acrylic box with inside dimensions measuring 22.9 cm wide, 22.9 cm long, and 30.5 cm tall and equipped with a vibrator motor (Model 3M564, Dayton Electrical Mfg., Niles, IL). The surface of the pods was manually leveled, and then an acrylic plate was lowered into the box until it rested on the peanut surface. Using the bottom edge of the plate, the peanut depth was recorded from the scales mounted on each side of the box. The average depth was used to calculate the total volume occupied by the peanuts including void space. The pod bulk density was calculated by dividing the sample mass by the bulk volume.
The vibrator was operated for 60 s and the peanut depth was recorded again from each side of the box. The pod bulk density was calculated in the same manner as described above. The pod bulk density computed from measurements recorded before vibration was called the “loose-filled” pod bulk density. The “settled” pod bulk density refers to the bulk density calculated from measurements recorded after vibration.
Peanut breeders collaborate in testing advanced breeding line peanut cultivars through the Uniform Peanut Performance Tests (UPPT). Standard cultivars of each peanut market type along with advanced selections from the various peanut breeding programs are planted and grown at nine locations across the United States (
Summary of loose-fill pod bulk density, grade factors and farmer stock value obtained from the 2002, 2003, and 2004 Uniform Peanut Performance Tests (UPPT).
Analysis of variance (P >#x3e; F) of factors to estimate total sound mature kernels (TSMK), other kernels (OK), and farmer stock value (FSV) for 2002, 2003, and 2004 UPPT data.
During farmer stock marketing of the 2005 peanut crop, the Federal-State Inspection Service (FSIS) in Alabama, Georgia, North Carolina, and Texas collected pod bulk densities data on all four peanut market types (runner, spanish, valencia, and virginia). Peanuts were offered for official inspection and grading to the FSIS. The official farmer stock sample (foreign material sample) was weighed and recorded according to the normal grading procedure. The foreign material sample was cleaned using the approved FSIS foreign material machine. In addition to measuring TSMK, total kernels (TK=TSMK+OK) were also measured for the 2005 study. Data were sent to the state office, error checked at the state office then forwarded to the USDA, ARS, National Peanut Research Laboratory in Dawson, Georgia. FSIS data from the 2005 crop years were analyzed using a paired t-test to determine any difference between loose-fill and settled pod bulk densities. Analysis of variance was used to determine the effects of peanut type, moisture, location, and pod bulk density on TSMK, OK, TK, and FSV. The degrees of freedom associated with each factor are shown in
Summary of pod bulk density, total sound mature kernels (TSMK), other kernels (OK), total kernels (TK), and farmer stock value (FSV) obtained during the study conducted during the 2005 peanut crop harvest.
Data from 393 UPPT samples harvested during the 2002–2004 crop years were analyzed and are summarized in
Results of analysis of variance using location, year, peanut type, cultivar, and bulk density to model TSMK, OK and FSV are shown in
The analysis of variance for spanish type peanuts is not shown because there was only one cultivar included in the UPPT. In general, the TSMK (
Tests were conducted during 2005 on a total of 480 samples of runner type peanuts in Alabama, Georgia, and Texas. Both loose-filled and settled pod bulk density were measured on 496 runner lots, but the grades were not completed on 16 samples in which the moisture content exceeded 10% wet basis. Data were collected on 25 lots of spanish type peanuts in Texas, and 132 virginia type lots in North Carolina and Texas. Twenty-two lots of valencia type peanuts were tested in Texas. The loose-fill bulk density ranged from 240.5 to 697.6 kg/m3 for runner type peanuts (
As expected, market type had a significant effect on peanut pod bulk density.
The grade factors observed for each market type tested are shown in
As in the data from the 2002–2004 UPPT, analysis of variance indicated for the 2005 data significant effects of market type and location (
Analysis of variance (P >#x3e; F) of factors affecting the farmer stock grade and value determined during the 2005 harvest season conducted by Federal-State Inspection Service.
Even where a predictable mathematical relationship could be developed, the large uncertainty associated with the prediction would be unacceptable for the buying and selling of peanuts. The FSV showed a nonlinear increase with settled pod bulk density (
Analysis of the 2002 to 2004 UPPT and 2005 FSIS data yielded similar results. Pod bulk density alone would not adequately predict grade factors or value for marketing. This is apparently contrary to results obtained by
In contrast, bulk density is determined by the total volume occupied by a mass of peanuts, including void space between pods. The void space among peanut pods is affected by the shape and size of the pods and the manner in which they settle. This can be seen in the differences in bulk density between market types. Spanish peanuts tend to be small pods with many single seeded pods. A virginia type peanut usually has a very large pod with a thick hull. Virginia type peanuts are also very long relative to the smaller diameter of the seed. As seen in
While in-shell bulk density is an important physical property, these data indicate that it is not an acceptable method of determining peanut value at farmer marketing. A method that measures individual pod density similar to the density separations by
Previous research had indicated that pod density could be used to estimate grade factors for marketing farmer stock peanuts. Therefore, data were collected from two different sources during the 2002 to 2005 harvests to determine the feasibility of using pod bulk density to estimate marketable peanut quality and value. General trends showed that as pod bulk density increased SMK, SS, TSMK, and TK, FSV increased. Percent OK decreased as pod bulk density increased. However, uncertainty associated with the grade value predictions based on pod bulk density was unacceptable. Based on these data, pod bulk density determined by measuring the bulk volume of a known weight of in-shell peanuts, will not suitably replace the grade factors determined in the current grading system. A system to measure individual pod density may result in better and acceptable estimates of the amount of edible peanuts in a farmer stock load.
The authors gratefully acknowledge the cooperation of the peanut breeders from the land grant universities and USDA, ARS and allowing use of the UPPT data for these studies. We give thanks to the state offices of the Federal-State Inspection Service including Wayne Bryant (NC), Donald Dozier (AL), Sonny Hooks (GA), Jerry Shugart (TX), and Ron Wood (GA). Invaluable technical support was provided by Hank Sheppard and Dan Todd of the National Peanut Research Laboratory.
Agricultural Engineer, Research Leader, USDA, ARS, National Peanut Research Laboratory, Dawson, Georgia 39842
Research Agronomist, Research Leader, USDA, ARS, National Peanut Research Laboratory, Dawson, Georgia 39842
Research Leader, USDA, ARS, National Peanut Research Laboratory, Dawson, Georgia 39842
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