Quality Test Results
A. Grade Factors
The U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS) has established numerical grades, definitions, and standards for grains. The attributes that determine the numerical grades for sorghum are test weight, broken kernels and foreign material (BNFM), foreign material, total damage, and heat damage. The table “U.S. Sorghum Grades and Grade Requirements” is provided on page 59 of this report.
Summary: Grade Factors and Moisture
Average U.S. Aggregate test weight (59.1 lb/bu or 76.1 kg/hl) was similar to 2015, with 87.8% of the samples at or above the factor limit for U.S. No. 1 grade sorghum (57.0 lb/bu or 73.4 kg/hl), and 96.1% of the samples at or above the limit for U.S. No. 2 grade (55.0 lb/bu or 70.8 kg/hl).
Average U.S. Aggregate broken kernels and foreign material (BNFM) (1.8%) was well below the maximum for U.S. No. 1 grade (3.0%), with 86.5% of the samples also at or below the maximum for U.S. No. 1 grade, and 97.3% of the samples at or below the maximum for U.S. No. 2 grade (6.0%).
Foreign material in the U.S. Aggregate samples averaged 0.6%, well below the maximum value of 1.0% for U.S. No. 1 grade. Over 88% of the samples were at or below the maximum for U.S. No. 1 grade, and almost 99% of the samples were at or below the maximum foreign material allowable for U.S. No. 2 grade (2.0%).
Total damage in the 2016 samples was distributed with 96.4% of the samples having 2% or less total damage (the maximum allowable for U.S. No. 1 grade), and 97.6% having 5% or less total damage (the maximum allowable for U.S. No. 2 grade).
There was no heat damage observed in any of the 2016 samples.
The U.S. Aggregate moisture content levels recorded at the elevator in the 2016 samples averaged 13.7%, with a minimum value of 10.8% and a maximum value of 17.6%.
The generally favorable weather conditions in 2016, especially those during harvest in the Late Harvest growing area, likely contributed to about 63% of the samples being delivered to elevators with 14% or less moisture, compared to 52% in 2015.
1. Test Weight
Test weight (kernel weight per standard container volume) is a measure of bulk density. It is often used as a general indicator of overall quality and as a gauge of endosperm hardness for size reduction and value-added processing. High test weight sorghum takes up less storage space than the same weight of sorghum with a lower test weight. Test weight is initially impacted by genetic differences in the structure of the kernel. However, it is also affected by moisture content, method of drying, physical damage to the kernel (broken kernels and scuffed surfaces), foreign material in the sample, kernel size, stress during the growing season, and microbiological damage. When sampled and measured at the point of delivery from the farm at a given moisture content, high test weight generally indicates high quality, high percentage of hard (or vitreous) endosperm, and sound, clean sorghum. Test weight is usually correlated with kernel true density and reflects kernel hardness and kernel maturity[1].
Results
Average U.S. Aggregate test weight in 2016 was 59.1 lb/bu (76.1 kg/hl), above the minimum for U.S. No. 1 grade (57.0 lb/bu or 73.4 kg/hl), and was about the same as 2015 (58.9 lb/bu or 75.9 kg/hl).
U.S. Aggregate test weight standard deviation in 2016 (1.51 lb/bu or 1.95 kg/hl) was lower than in 2015 (1.68 lb/bu or 2.16 kg/hl).
The 2016 test weight values were distributed with 87.8% of the samples at or above the factor limit for U.S. No. 1 grade, and 96.1% of the samples at or above the limit for U.S. No. 2 grade (55.0 lb/bu or 70.8 kg/hl).
Average Late Harvest test weight (59.4 lb/bu or 76.4 kg/hl) was slightly higher than average Early Harvest test weight (58.4 lb/bu or 75.1 kg/hl) in 2016. This outcome may be attributable to the more favorable 2016 weather conditions for grain-fill in the Late Harvest Area compared to the Early Harvest Area. Average Late Harvest test weight was also higher than average Early Harvest test weight in 2015.
[1] Buffo, R.A., C.L. Weller and A.M. Parkhurst. 1998. Relationship among grain sorghum quality factors. Cereal Chemistry 75(1):100-104.
2. Broken Kernels and Foreign Materials (BNFM)
Broken kernels and foreign material (BNFM) is an indicator of the amount of clean, sound sorghum available for feed and processing. The lower the percentage of BNFM, the less foreign material and/or fewer broken kernels are in a sample. Higher levels of BNFM in farm-originated samples generally stem from combine settings and/or weed seeds in the field. BNFM levels will normally increase during drying and handling, depending on the methods used and the soundness of the kernels. Stress crack formation during dry down or during mechanical drying after harvest will also result in an increase in broken kernels and BNFM during subsequent handling.
Results
Average U.S. Aggregate BNFM in 2016 (1.8%) was well below the maximum for U.S. No. 1 grade (3.0%) and was about the same as 2015 (1.7%).
The 2016 U.S. Aggregate BNFM standard deviation (1.06%) was slightly higher than 2015 (0.93%).
Of the 2016 U.S. Aggregate samples, 86.5% of the samples were at or below the maximum BNFM allowable for U.S. No. 1 grade, and 97.3% were at or below the maximum for U.S. No. 2 grade (6.0%).
No difference was observed between average Early Harvest and Late Harvest BNFM.
3. Foreign Material
Foreign material, a subset of BNFM, is of importance because it has little feed or processing value. It is also generally higher in moisture content than the sorghum itself, and therefore creates a potential for deterioration of sorghum quality during storage. Foreign material also contributes to the spout-line and has the possibility of creating more quality problems and damage because of its higher moisture level, as previously mentioned.
Results
Average U.S. Aggregate foreign material in 2016 (0.6%) was almost half of the maximum value of 1.0% for U.S. No. 1 grade, and was the same as 2015 (0.6%).
U.S. Aggregate foreign material standard deviation in 2016 (0.53%) was slightly higher than 2015 (0.41%).
In 2016, 88.4% of the samples were at or below the maximum foreign material allowable for U.S. No. 1 grade, and 98.8% were at or below the maximum for U.S. No. 2 grade (2.0%).
Average Late Harvest foreign material (0.6%) was slightly lower than average Early Harvest foreign material (0.8%) in 2016. This difference may be attributable to pest pressure and weather conditions at harvest and differences in the growing areas of the samples.
4. Total Damage
Total damage is the percentage of kernels and pieces of kernels that are visually damaged in some way, including badly ground-damaged, badly weather-damaged, diseased, frost-damaged, germ-damaged, heat-damaged, insect-bored, mold-damaged, sprout-damaged, or otherwise materially damaged kernels. Most of these types of damage result in some sort of discoloration or change in kernel texture. Damage does not include broken pieces of grain that are otherwise normal in appearance. Mold damage is usually associated with higher than desired moisture content levels and temperatures during growth and/or in storage. Mold damage and the associated potential for development of mycotoxins are the damage factors of greatest concern. Mold damage can occur prior to harvest as well as during temporary storage at high moisture and high temperature levels prior to delivery.
Results
Average U.S. Aggregate total damage was 0.4% in 2016, well below the limit for U.S. No. 1 grade (2%).
The 2016 U.S. Aggregate total damage standard deviation (0.50%) was higher than 2015 (0.13%).
Total damage in the 2016 samples was distributed with 96.4% of the samples having 2% or less total damage (the maximum allowable for U.S. No. 1 grade), and 97.6% having 5% or less total damage (the maximum allowable for U.S. No. 2 grade).
Very little total damage (0.1%) was observed in Late Harvest samples, whereas the observed total damage levels for the U.S. Aggregate samples (0.4%) can be attributed to the total damage observed in Early Harvest samples (1.2%). The observed Early Harvest total damage may have been due to early season pest problems, harvest weather and sprouting issues encountered in that area.
Average U.S. Aggregate total damage in 2016 (0.4%) was higher than 2015 (0.1%), largely due to the average total damage of 2016 Early Harvest samples.
5. Heat Damage
Heat damage is a subset of total damage and has separate allowances in the U.S. Grade Standards. Heat damage can be caused by microbiological activity in warm, moist grain or by high heat applied during drying. Heat damage is seldom present in sorghum delivered at harvest directly from farms.
Results
There was no heat damage observed in any of the 2016 samples.
The absence of heat damage likely was due in part to recently-harvested samples coming directly from farm to elevator with minimal, if any, prior drying.
1. Assessing the Presence of Aflatoxins and DON
At least 25% of the minimum number of samples (250) across the sampling area was proportionately collected and tested to assess the impact of the 2016 growing conditions on total aflatoxins and DON development in the U.S. sorghum crop. The sampling criteria, described in the “Survey and Statistical Analysis Methods” section, resulted in a total number of 75 samples tested for mycotoxins.
A threshold established by the U.S. Department of Agriculture (USDA) Federal Grain Inspection Service (FGIS) as the “Lower Conformance Level” (LCL) was used to determine whether or not a detectable level of the mycotoxin appeared in the sample. The LCLs for the analytical kits approved by FGIS and used for this 2016/2017 report were 5.0 parts per billion (ppb) for aflatoxins and 0.5 parts per million (ppm) for DON. The FGIS LCL was higher than the Limit of Detection (LOD) specified by the kit manufacturer of 2.0 ppb and 0.1 ppm for aflatoxin and DON, respectively. Details on the testing methodology employed in this study for the mycotoxins are in the “Testing Analysis Methods” section.
Results: Aflatoxins
A total of 75 samples were analyzed for aflatoxins in 2016. Results of the 2016/2017 Harvest Report are as follows:
Seventy-two samples (72), or 96.0% of the 75 survey samples, had no detectable levels of aflatoxins (below the FGIS LCL of 5.0 ppb). This is below the percentage in 2015, where 100% of the samples tested had no detectable levels of aflatoxins.
Three samples (3), or 4.0% of the 75 samples, showed aflatoxin levels greater than the LCL of 5.0 ppb, but less than or equal to 10 ppb.
No samples (0), or 0.0% of the 75 samples, showed aflatoxin levels greater than 10 ppb, but less than or equal to the Food and Drug Administration (FDA) action level of 20 ppb.
No samples (0), or 0.0% of the 75 samples, showed aflatoxin levels greater than the FDA action level of 20 ppb.
While the 2016 crop season had a slightly lower percentage of samples below the FGIS LCL of 5.0 than 2015, the high percentage of samples testing below the LCL indicated that the contamination level in the domestic crop was negligible. This may have been due, in part, to favorable weather conditions in 2016 (see the “Crop and Weather Conditions” section for more information on the 2016 growing conditions). Most of the growing area received ample moisture and experienced close-to-normal temperatures during pollination and grain-fill in 2016, and as a result, the plants were not under stress.
Results: DON (Deoxynivalenol or Vomitoxin)
A total of 75 samples were analyzed collectively for DON in 2016. Results of the 2016 survey are shown below:
All seventy-five (75) samples, or 100.0% of the 75 survey samples, had no detectable levels of DON (all samples tested less than or equal to the FGIS LCL of 0.5 ppm). This is the same as the percentage in 2015, where 100% of the samples tested had no detectable levels of DON.
No samples (0), or 0.0% of the 75 samples, tested greater than 0.5 ppm, but less than or equal to the FDA advisory level of 5 ppm.
No samples (0), or 0.0% of the 75 samples, tested greater than the FDA advisory level of 5 ppm.
The fact that all survey samples tested below the FGIS LCL threshold of 0.5 ppm showed that the DON contamination level in the domestic crop was minimal. This may have been due, in part, to weather conditions that were not conducive to DON development in 2016 (see the “Crop and Weather Conditions” section for more information on the 2016 growing conditions).
2. Background: General
The levels at which the fungi produce the mycotoxins are impacted by the fungus type and the environmental conditions under which the sorghum is produced and stored. Because of these differences, mycotoxin production varies across the U.S. sorghum-producing areas and across years. In some years, the growing conditions across the sorghum-producing regions might not produce elevated levels of any mycotoxins. In other years, the environmental conditions in a particular area might be conducive to production of a particular mycotoxin to levels that impact the sorghum’s use for human and livestock consumption. Humans and livestock are sensitive to mycotoxins at varying levels. As a result, the FDA has issued action levels for aflatoxins and advisory levels for DON by intended use.
Action levels specify precise limits of contamination above which the agency is prepared to take regulatory action. Action levels are a signal to the industry that the FDA believes it has scientific data to support regulatory and/or court action if a toxin or contaminant is present at levels exceeding the action level, if the agency chooses to do so. If import or domestic feed supplements are analyzed in accordance with valid methods and found to exceed applicable action levels, they are considered adulterated and may be seized and removed from interstate commerce by the FDA.
Advisory levels provide guidance to the industry concerning levels of a substance present in food or feed that are believed by the agency to provide an adequate margin of safety to protect human and animal health. While the FDA reserves the right to take regulatory enforcement action, enforcement is not the fundamental purpose of an advisory level.
A source of additional information is the National Grain and Feed Association (NGFA) guidance document titled “FDA Mycotoxin Regulatory Guidance”, which can be found at http://www.ngfa.org/wp-content/uploads/NGFAComplianceGuide-FDARegulatory….
3. Background: Aflatoxins
The most important type of mycotoxin associated with sorghum grain is aflatoxin. There are several types of aflatoxin produced by different species of Aspergillus, with the most prominent species being A. flavus. Growth of the fungus and aflatoxin contamination of grain can occur in the field prior to harvest or in storage. However, contamination prior to harvest is considered to cause most of the problems associated with aflatoxin. A. flavus grows well in hot, dry environmental conditions, or where drought occurs over an extended period of time. It can be a serious problem in the southern United States, where hot and dry conditions are more common. The fungus usually attacks only a few kernels on the plant and often penetrates kernels through wounds produced by insects.
There are four types of aflatoxin naturally found in foods – aflatoxins B1, B2, G1, and G2. These four aflatoxins are commonly referred to as “aflatoxins” or “total aflatoxins.” Aflatoxin B1 is the most commonly found aflatoxin in food and feed and is also the most toxic. Research has shown that B1 is a potent, naturally-occurring carcinogen in animals, with a strong link to human cancer incidence. Additionally, dairy cattle metabolize aflatoxin B1 to a different form of aflatoxin called aflatoxin M1, which may accumulate in milk.
Aflatoxins express toxicity in humans and animals primarily by attacking the liver. The toxicity can occur from short-term consumption of very high doses of aflatoxin-contaminated grain or long-term ingestion of low levels of aflatoxins, possibly resulting in death in poultry and ducks, the most sensitive of the animal species. Livestock may experience reduced feed efficiency or reproduction, and both human and animal immune systems may be suppressed as a result of ingesting aflatoxins.
The FDA has established action levels for aflatoxin M1 in milk intended for human consumption and aflatoxins in human food, grain, and livestock feed (see table below).
The FDA has established additional policies and legal provisions concerning the blending of sorghum with levels of aflatoxins exceeding these threshold levels. In general, the FDA currently does not permit the blending of sorghum containing aflatoxin with uncontaminated sorghum to reduce the aflatoxin content of the resulting mixture to levels acceptable for use as human food or animal feed.
If required by the buyer, sorghum exported from the United States will be tested for aflatoxins by FGIS. Sorghum above the FDA action level of 20 ppb or the buyer’s specification cannot be exported unless other strict conditions are met. These requirements result in relatively low levels of aflatoxins in exported grain.
4. Background: DON (Deoxynivalenol or Vomitoxin)
DON is another mycotoxin of concern to some importers of sorghum grain. It is produced by certain species of Fusarium, the most important of which is Fusarium graminearum (Gibberellazeae). Gibberellazeae can develop when cool or moderate and wet weather occurs at flowering. Mycotoxin contamination of sorghum caused by Gibberellazeae is often associated with excessive postponement of harvest and/or storage of high-moisture sorghum.
DON is mostly a concern with monogastric animals, where it may cause irritation of the mouth and throat. As a result, the animals may eventually refuse to eat the DON-contaminated sorghum and may have low weight gain, diarrhea, lethargy, and intestinal hemorrhaging. Additionally, DON may cause suppression of the immune system, resulting in susceptibility to a number of infectious diseases.
The FDA has issued advisory levels for DON. For grain products, the advisory levels are:
5 ppm in grains and grain co-products for swine, not to exceed 20% of their diet;
10 ppm in grains and grain co-products for chickens and cattle, not to exceed 50% of their diet; and
5 ppm in grains and grain co-products for all other animals, not to exceed 40% of their diet.
FGIS is not required to test for DON on sorghum bound for export markets, but will perform either a qualitative or quantitative test for DON at the buyer’s request.
B. Moisture
Moisture content (water weight in kernels per total weight of kernels (i.e., water weight plus dry matter weight) also known as wet basis) is reported on official grade certificates, but does not determine which numerical grade will be assigned to the sample. Moisture content affects the amount of dry matter being sold and purchased. Also an indicator for potential drying, moisture has potential implications for storability, and affects test weight. Higher moisture content at harvest increases the chance of kernel damage occurring during harvesting and drying. Moisture content and the amount of mechanical drying required will also affect stress-crack formation, breakage, and germination. Extremely wet kernels may be a precursor to high mold damage later in storage or transport. While the weather during the growing season affects yield and the development of the kernels, harvest moisture is influenced largely by the timing of harvest and harvest weather conditions.
Results
The U.S. Aggregate moisture content recorded at the elevator in the 2016 samples averaged 13.7%, with a minimum value of 10.8% and a maximum value of 17.6%.
U.S. Aggregate moisture content standard deviation in 2016 (0.95%) was lower than 2015 (1.19%).
The 2016 moisture values were distributed with 62.7% containing 14% or less moisture; 14% is the moisture level used by most elevators as the basis for discounts and a level considered safe for storage for short periods during low winter-time temperatures.
Late Harvest average moisture content was slightly lower than Early Harvest average moisture content in 2016 (13.7% and 13.8%, respectively) and 2015 (14.0% and 14.5%, respectively). This difference may have been due to longer in-field dry down in the Late Harvest Area than in the Early Harvest Area. A longer harvest window and more favorable harvest weather conditions likely contribute to longer in-field dry down.
In 2016, the generally favorable weather conditions, especially during harvest in the Late Harvest Area, likely contributed to 62.7% of the samples being delivered to elevators at or below 14% moisture, compared to 52% in 2015.
B. Moisture
Moisture content (water weight in kernels per total weight of kernels (i.e., water weight plus dry matter weight) also known as wet basis) is reported on official grade certificates, but does not determine which numerical grade will be assigned to the sample. Moisture content affects the amount of dry matter being sold and purchased. Also an indicator for potential drying, moisture has potential implications for storability, and affects test weight. Higher moisture content at harvest increases the chance of kernel damage occurring during harvesting and drying. Moisture content and the amount of mechanical drying required will also affect stress-crack formation, breakage, and germination. Extremely wet kernels may be a precursor to high mold damage later in storage or transport. While the weather during the growing season affects yield and the development of the kernels, harvest moisture is influenced largely by the timing of harvest and harvest weather conditions.
Results
The U.S. Aggregate moisture content recorded at the elevator in the 2016 samples averaged 13.7%, with a minimum value of 10.8% and a maximum value of 17.6%.
U.S. Aggregate moisture content standard deviation in 2016 (0.95%) was lower than 2015 (1.19%).
The 2016 moisture values were distributed with 62.7% containing 14% or less moisture; 14% is the moisture level used by most elevators as the basis for discounts and a level considered safe for storage for short periods during low winter-time temperatures.
Late Harvest average moisture content was slightly lower than Early Harvest average moisture content in 2016 (13.7% and 13.8%, respectively) and 2015 (14.0% and 14.5%, respectively). This difference may have been due to longer in-field dry down in the Late Harvest Area than in the Early Harvest Area. A longer harvest window and more favorable harvest weather conditions likely contribute to longer in-field dry down.
In 2016, the generally favorable weather conditions, especially during harvest in the Late Harvest Area, likely contributed to 62.7% of the samples being delivered to elevators at or below 14% moisture, compared to 52% in 2015.
C. Chemical Composition
Chemical composition of sorghum is important because the components of protein, starch, oil, and tannins are of significant interest to end users. The chemical composition attributes are not grade factors. However, they provide additional information related to nutritional value for livestock and poultry feeding and other processing uses of sorghum. Unlike many physical attributes, chemical composition values are not expected to change significantly during storage or transport.
Summary: Chemical Composition
In 2016, U.S. Aggregate protein concentration averaged 8.5% (dry basis), with a standard deviation of 1.10%.
U.S. Aggregate starch concentration averaged 72.6% (dry basis) in 2016, with a standard deviation of 0.91%. Almost all the 2016 samples had at least 70% starch.
U.S. Aggregate oil concentration averaged 4.4% (dry basis) in 2016. Over half (52.8%) of the 2016 samples had an oil concentration of 4.5% or higher.
All samples had no detectable levels of tannins (below 4.0 mg CE/g), the same as in 2015.
1. Protein
Protein is very important for poultry and livestock feeding, as it supplies essential sulfur-containing amino acids and helps to improve feed conversion efficiency. Variation in protein concentration from year to year is usually inversely related to variation in starch concentration and yield[1]. Results are reported on a dry basis (protein weight in kernels per total dry matter weight of kernels).
Results
In 2016, U.S. Aggregate protein concentration averaged 8.5%, which is within recognized levels found in literature for U.S. sorghum hybrids.
The lower average U.S. Aggregate protein concentration in 2016 (8.5%) compared to 2015 (10.9%) was consistent with slightly higher average yield in 2016 (76.5 bu/ac or 4.80 mt/ha) versus 2015 (76.0 bu/ac or 4.77 mt/ha). The decline in average protein may also be attributed to differences in hybrid seeds planted between 2016 and 2015.
The 2016 U.S. Aggregate protein standard deviation was 1.10% in 2016, compared to 1.02% in 2015.
Protein concentration range in 2016 (4.2 to 14.5%) was greater than in 2015 (6.8 to 14.1%).
Protein concentration in the 2016 samples was distributed with 61.0% below 9%, 36.2% between 9 and 10.99%, and 2.8% at or above 11%.
Average Late Harvest protein concentration (8.6%) was higher than average Early Harvest protein concentration (8.2%) in 2016. Average Late Harvest 2. Starch
Starch is an important factor for sorghum and is related to metabolizable energy for livestock and poultry. Levels of starch in sorghum may also be of interest to processors, as starch provides the substrate for several value-added processes. High starch concentration is often indicative of good kernel maturation/filling conditions and reasonably moderate kernel densities. Variation in starch concentration from year to year is usually inversely related to variation in protein concentration. Results are reported on a dry basis (starch weight in kernels per total dry matter weight of kernels).
Results
U.S. Aggregate starch concentration averaged 72.6% in 2016, a level within recognized levels found as reported in literature for any commercial hybrid sorghum sample, compared to 73.2% in 2015.
The 2016 U.S. Aggregate starch concentration standard deviation (0.91%) was slightly greater than 2015 (0.80%).
2.Starch
Starch concentration range in 2016 (67.4 to 76.8%) was greater than in 2015 (68.7 to 75.6%).
Starch concentration in the 2016 samples was distributed with 68.3% between 70 and 72.99%, 21.5% between 73 and 73.99%, and 10.1% equal to or greater than 74%.
Average starch concentration for Late Harvest samples (72.7%) was essentially the same as that for Early Harvest samples (72.4%). The starch concentration averages for the 2015 Late Harvest and Early Harvest samples were also comparable.concentration was also higher than Early Harvest protein concentration in 2015.
[1] Worker, Jr., G.F. and J. Ruckman. 1968. Variations in protein levels in grain sorghum grown in southwest desert. Agronomy Journal 60(5):485-488.
3. Oil
Oil is an essential component of poultry and livestock rations. It serves as an energy source, enables fat-soluble vitamins to be utilized, and provides certain essential fatty acids. Oil may also be an important co-product of sorghum value-added processing. Results are reported on a dry basis (oil weight in kernels per total dry matter weight of kernels).
Results
Average U.S. Aggregate oil concentration in 2016 (4.4%), within a recognized range of oil concentration values in literature for U.S. sorghum hybrids, was similar to 2015 (4.5%).
The 2016 U.S. Aggregate oil concentration standard deviation (0.25%) was about the same as 2015 (0.27%).
Oil concentration range in 2016 (2.7 to 5.2%) was slightly greater than in 2015 (3.0 to 5.1%).
Over half of 2016 U.S. Aggregate samples (52.8%) had an oil concentration at 4.5% and higher, 32.9% between 4 to 4.49%, and 14.2% equal to or less than 3.99%.
Late Harvest samples had an average oil concentration of 4.4%, whereas the Early Harvest samples had an average oil concentration of 4.3%.
4. Tannins
Tannins are present in sorghum varieties that have a pigmented testa within their kernels. Chemically, tannins are compounds that are large molecules comprised of smaller phenolic molecules (catechins, epicatechins, etc.). These compounds, which have antioxidant and other possible health benefits, are widely distributed in nature. For example, they are found in grapes, bark, tea leaves, etc., influencing aroma, flavor, mouth-feel, and astringency. While present in sorghum varieties grown around the world, more than 99% of sorghum currently grown in the United States is tannin-free due to decades of breeding efforts to eliminate tannins from sorghum hybrids. Tannins have effects on nutritional and functional properties as a result of interactions of the tannins with nutrients in the kernel. Livestock and poultry growth performance can be negatively affected by the presence of tannins in sorghum-containing rations. Current non-tannin sorghum varieties grown in the United States have virtually the same energy profile as corn in feed rations. Results are reported as being below 4.0 milligrams of catechin equivalents (CE) per gram sample (4.0 mg CE/g) or above. Values below 4.0 mg CE/g generally imply absence of condensed tannins2,3.
[2] Awika, J.M. and L.W. Rooney. 2004. Sorghum phytochemicals and their potential impact on human health. Phytochemistry 65(9):1199-1221.
[3] Price, M.L., S. Van Scoyoc and L.G. Butler. 1978. A critical evaluation of vanillin reaction as an assay for tannin sorghum. Journal of Agricultural and Food Chemistry 26(5):1214-1218.
D. Physical Factors
Physical factors include other quality attributes that are neither grading factors nor chemical composition. Tests for physical factors provide additional information about the processing characteristics of sorghum for various uses, as well as its storability and potential for breakage in handling. The storability, ability to withstand handling, and processing performance of sorghum are all influenced by sorghum’s morphology. Sorghum kernels are morphologically made up of three parts: the germ or embryo, the pericarp or outer covering, and the endosperm. The endosperm represents about 82 to 86% of the kernel and consists of soft (also referred to as floury) endosperm and of hard (also called vitreous) endosperm, as shown at right. The endosperm contains primarily starch and protein, whereas the germ contains oil and some proteins. The pericarp is comprised mostly of fiber, with a small coating of waxy material. Softer and smaller kernels usually require less energy than harder and larger kernels to reduce to similar particle size4.
Summary: Physical Factors
Average U.S. Aggregate kernel diameter (2.61 mm) and 1000-kernel weight (TKW) (28.17 g) were both higher in 2016 than in 2015, indicating slightly larger kernels in 2016 than in 2015.
Average U.S. Aggregate kernel volume (20.57 mm3)is within a normal range reported in literature and is slightly higher than 2015, confirming larger kernels in 2016 than in 2015.
U.S. Aggregate kernel true density averaged 1.370 g/cm3, which is within the range of values suitable for size reduction in feed preparation. Three-quarters of the 2016 samples’ true density was between 1.345 and 1.389 g/cm3.
Average U.S. Aggregate kernel hardness index (67.1) was lower than 2015 (71.0). This may imply less energy needed for grinding the 2016 crop compared to the 2015 crop (on an equivalent weight basis) to a similar particle size.
Late Harvest samples had higher average true density, TKW, hardness, test weight, and protein concentration than the Early Harvest samples in 2016 and 2015.
[4] Healy, B.J., J.D. Hancock, G.A. Kennedy, P.J. Bramel-Cox, K.C. Behnke and R.H. Hines. 1994. Optimum particle size of corn and hard and soft sorghum for nursery pigs. Journal of Animal Science 72(9):2227-2236.
1. Kernel Diameter
Kernel diameter (reported in mm) directly correlates with kernel volume, affects size reduction behavior and material handling practices, and may indicate maturity of kernels. Size reduction refers to reducing kernels (large particles) to ground material (small particles), commonly through grinding/milling. Size reduction, energy consumption, decortication efficiency, and yield of kernel components depend on diameter. Decortication refers to the removal of the pericarp and germ from a kernel by attrition or abrasion, with minimal removal of endosperm before subsequent grinding/milling. The smaller the kernels, the more care and concern required in handling. Incomplete kernel fill and unexpected weather conditions may contribute to small diameter values.
Results
Average U.S. Aggregate kernel diameter in 2016 (2.61 mm) had a value within a recognized range reported in literature for any commercial sorghum hybrid sample, and was higher than 2015 (2.53 mm).
The 2016 U.S. Aggregate kernel diameter standard deviation (0.10 mm) was about the same as 2015 (0.09 mm).
Kernel diameter range in 2016 (2.20 to 3.01 mm) was greater than in 2015 (2.18 to 2.90 mm).
In 2016, kernel diameters were distributed so that 22.8% of the samples had kernel diameters of 2.7 mm or greater, 66.9% between 2.5 and 2.69 mm, and 10.3% less than 2.5 mm.
2. 1000-Kernel Weight
1000-kernel weight (commonly referred to as TKW) is the weight for a fixed number of kernels, and is reported in grams. Kernel volume (or size) can be inferred from TKW, since as TKW increases or decreases, kernel volume will proportionally increase or decrease. Kernel volume affects drying rates. As kernel volume increases, the volume-to-surface-area ratio for the kernel becomes greater, and drying time to a desired moisture level takes longer. Kernel weights tend to be higher for specialty varieties of sorghum that have high amounts of hard (vitreous) endosperm.
Results
TKW averaged 28.17 g for the U.S. Aggregate in 2016, a value within a recognized range of TKW values in literature for U.S. sorghum hybrids.
Average U.S. Aggregate TKW in 2016 was higher than in 2015 (26.30 g).
U.S. Aggregate TKW standard deviation in 2016 (2.15 g) was slightly greater than in 2015 (2.00).
TKW range in 2016 (19.30 to 37.13 g) was greater than in 2015 (19.49 to 34.66 g).
In the 2016 samples, TKWs were distributed with 24.1% at 30 g or greater, 70.5% between 24 and 29.99 g, and 5.5% less than 24 g.
The slightly greater average TKW in 2016 for Late Harvest samples (28.30 g) than for Early Harvest samples (27.79 g) generally parallels the slightly higher test weight average in 2016 for Late Harvest samples than for Early Harvest samples.
3. Kernel Volume
Kernel volume (or size), reported in mm3, is directly related to kernel diameter and is often indicative of growing conditions. If conditions are dry, kernels may be small due to stunted development. If drought hits later in the season, kernels may have lower fill. Small kernels are more difficult to handle and, due to their having a greater surface-area-to-volume ratio than large kernels, greater amounts of endosperm are removed during decortication, reducing yield of endosperm-derived products.
Results
Kernel volume averaged 20.57 mm3 for U.S. Aggregate samples in 2016, a value within a recognized range of values reported in literature for any commercial sorghum hybrid sample.
Average U.S. Aggregate average kernel volume in 2016 was greater than 2015 (19.34 mm3), confirming larger-sized kernels in 2016 than in 2015.
The 2016 U.S. Aggregate kernel volume standard deviation (1.65 mm3) was greater than 2015 (1.44 mm3).
Kernel volume range in 2016 (13.51 to 26.97 mm3) was greater than in 2015 (14.31 to 25.40 mm3).
In the 2016 samples, kernel volumes were distributed with 8.7% less than 18 mm3, 68.9% between 18 and 21.99 mm3, and 22.4% equal to or greater than 22 mm3.
The average kernel volume for Late Harvest samples (20.60 mm3) was slightly higher than the average for Early Harvest samples (20.50 mm3) in 2016. Average kernel volume was also higher for Late Harvest samples than Early Harvest samples in 2015.
4. Kernel Density
Kernel true density (kernel weight per kernel volume, reported as g/cm3) is a relative indicator of kernel hardness, which is useful during size reduction operations. Genetics of the sorghum hybrid and the growing environment affect kernel true density. Sorghum with higher density is typically less susceptible to breakage in handling than lower-density sorghum. Most sorghum used for feed has true density values ranging from 1.330 to 1.400 g/cm3. Sorghum with density greater than 1.315 g/cm3 is judged suitable for processing to brewers’ grits and stiff porridge, whereas sorghum with density less than 1.315 g/cm3 is suitable for processing into soft bread flour and starch.
Results
U.S. Aggregate kernel true density averaged 1.370 g/cm3 in 2016, which falls within a recognized range of kernel true density values in literature for U.S. sorghum hybrids.
Average U.S. Aggregate kernel true density in 2016 was higher than 2015 (1.359 g/cm3), indicating that, on average, kernels from the 2016 crop weighed more than similarly-sized kernels from the 2015 crop.
The U.S. Aggregate true density standard deviation in 2016 (0.028 g/cm3) was greater than in 2015 (0.013 g/cm3).
True density range in 2016 (1.208 to 1.522 g/cm3) was greater than in 2015 (1.295 to 1.402 g/cm3).
In the 2016 samples, kernel true densities were distributed with 1.6% below 1.315 g/cm3, 2.4% between 1.315 and 1.329 g/cm3, 7.1% between 1.330 and 1.344 g/cm3, and 89.0% at 1.345 g/cm3 and above.
The greater average true densities for Late Harvest samples (1.375 g/cm3) than for Early Harvest samples (1.356 g/cm3) in 2016 generally corresponds to the higher test weight and protein averages for Late Harvest samples than Early Harvest samples in 2016.
5. Kernel Hardness Index
Kernel hardness affects resistance to molds and insects, size reduction behavior, and the end use of sorghum. Sieving behavior, size reduction energy consumption, particle size distribution of ground material, and yield of kernel components depend on hardness. Harder sorghum not only produces coarser or larger particles than softer sorghum; it also requires more energy per mass of sorghum to achieve similar particle size distribution during size reduction. As a result, grinding/milling for optimum particle size for livestock or poultry feed may be costlier for harder sorghum than for softer sorghum. Test weight and kernel density correlate with hardness. Kernel hardness index is a dimensionless number, with increasing value indicating kernels increasing in physical hardness.
Results
Kernel hardness index averaged 67.1 for U.S. Aggregate samples in 2016, a value within a recognized range of kernel hardness index values in literature for U.S. commercial sorghum hybrids.
Average U.S. Aggregate kernel hardness index in 2016 was less than 2015 (71.0), indicating slightly softer kernels in 2016 compared to 2015.
The U.S. Aggregate kernel hardness index standard deviation in 2016 (6.3) was about the same as in 2015 (6.2).
Kernel hardness index range in 2016 (41.7 to 88.2) was less than in 2015 (37.1 to 91.5).
In the 2016 samples, kernel hardness indices were distributed so that 4.7% of the samples had kernel hardness indices of 80 or greater, 95.2% had 40 to 79.99, and none had less than 40.
The slightly greater average kernel hardness index for Late Harvest samples (67.6) than for Early Harvest samples (65.7) in 2016 and 2015 generally parallels a higher test weight average for Late Harvest samples than Early Harvest samples in 2016 and 2015.
A. 2016 Harvest Highlights
Weather conditions before and at planting, throughout the growing season, and even during harvest play a major role in the evolution of the sorghum plant and ultimately in the sorghum grain yield and quality. For U.S. sorghum production, two main harvest areas, Early Harvest Area (EHA) and Late Harvest Area (LHA), are highlighted.
For the Early Harvest Area (EHA), the 2016 growing season was on or ahead of schedule for most of the region. Precipitation from the February to April period was above- or much above-average, which imposed a wetter early-growth period (from planting until pollination) compared to the historical period of 1895 to 2016. Wet conditions lingered across the Texas coastal area and east-central portion of the EHA until harvest time, while drier conditions developed within the continental area (to the northwest) during the reproductive phase until harvest. The 2016 sorghum crop condition for the EHA improved until after pollination, but was slightly diminished as the crop approached harvest time.
The following list highlights the key events of the EHA for the 2016 growing season:
Average temperatures during the early planting time frame (from February until April) were above the historical average (2 degrees Farenheit higher than the average for the 1981-2010 period), providing warm temperatures for rapid emergence conditions.
Moving from the western to the eastern part of the EHA, above-average and much above-average moisture conditions increased during the early planting period (making the period the wettest on record in these areas) and continued until harvest in several areas.
Excessive precipitation produced above-average moisture conditions, specifically for the central part of Texas, impacting yield and harvest.
Pollination and reproductive periods experienced near-average temperatures, promoting a normal crop development and setting up the crop for high yield potential.
For the Late Harvest Area (LHA), the 2016 growing season started near-average, compared to the 2015 season. However, planting in May was slightly delayed due to wet conditions and temperatures above the historical temperature average (1985–2016). The 2016 sorghum crop condition for the LHA remained fairly constant from early emergence until harvest (June to October), with more than 70% of the crop having achieved a Good or Excellent condition rating[1].
The following list highlights the key events of the LHA for the 2016 growing season:
Warm temperatures were recorded during planting (from May until June), 2 degrees Fahrenheit above the historical average for 1986 to 2016, speeding up the emergence of the crop.
Heavy precipitation, specifically during the month of May, affected planting and delayed early-season crop growth progress.
Pollination was characterized by wet moisture conditions and near-average temperatures, which created favorable conditions for floret fertility and grain formation.
Above-average temperatures in the Texas Panhandle (from July until August) potentially impacted maximum yield on irrigated areas. However, temperatures for pollination and grain-filling in areas further north during September were near- or slightly above-average, and had good conditions for the yield components of grain numbers and grain size.
Warm temperatures during harvest time (4-6 degrees Fahrenheit higher than the average for the 1981-2010 period) accelerated maturity, natural drying, and harvest during October.
The following sections describe how the 2016 growing season weather impacted sorghum development and yield for both the EHA and LHA in the U.S. sorghum production regions.
[1] A ‘Good’ rating means that yield prospects are normal. Moisture levels are adequate and disease, insect damage, and weed pressures are minor. An ‘Excellent’ rating means that yield prospects are above normal, and the crop is experiencing little or no stress. Disease, insect damage, and weed pressures are insignificant.
B. Planting and Early Growth Conditions
Near- to above-average precipitation and temperature did not affect planting progress
Weather (i.e., temperature, solar radiation, precipitation) and environmental factors present a complex interaction with the genotype (sorghum hybrids) and management practices used in sorghum production (i.e., timing of planting, soil fertility, pesticide applications). These factors – weather and environment, genotype, and management practices – are referred to as the “G x E x M” interaction. Grain yield in sorghum is a function of the number of plants per acre, number of tillers[1] per plant, number of grains per head, and final seed weight per individual grain. Ultimately, potential sorghum yield depends on the influence of the G x E x M components on all the yield factors previously noted.
As general guidelines, wet and cool planting conditions can decrease uniformity, delay emergence, or hinder early plant growth, which may result in a lower number of plants and/or lower yields per area. Sorghum can compensate for small stand reductions via tillering capacity. The tillering capacity will also be affected by the G x E x M interaction. The genotype selected will set the genetic potential for that plant to produce tillers. The environment’s availability of resources (with/without stress conditions) will impact the plant’s growth. Lastly, management practices that can promote tillering, such as wide-row spacing, lower seeding rate, and better nutrition, will also impact the plant’s development. Optimal moisture and warmer conditions than normal early in the growing season are beneficial for proper root establishment and plant-to-plant uniformity. This is because these conditions promote the development of deeper root systems for adequate anchorage and sustain continuous access to water and nutrients during the growing season.
Early Harvest Area (EHA)
Overall, early planting conditions from February to April in the EHA were impacted by relatively above-normal temperatures and above-normal precipitation. Moving from west to east across the EHA, precipitation ranged from 5 to more than 20 inches in the spring. Planting was ahead of or near the average, with a slight delay in planting progress in April, when compared to the average for the 2011-2015 period.
Late Harvest Area (LHA)
Planting progress started near-average, with a slight delay during the month of May, which was caused by excess precipitation experienced in many areas across the region. The 2016 LHA planting season spanned from April until July, with the largest planting progress made between late May to late June. Overall, the crop condition remained fairly constant from early planting until harvest time (more than 70% in Good or Excellent crop condition).
[1] Tillers are stems smaller than the main plant stalk that can also develop fertile heads.
C. Late Vegetative and Pollination Conditions
Wet conditions and near- or slightly above-average temperatures favored pollination
Total time from emergence to pollination depends on the planting date, weather conditions for this period (temperature and precipitation), and the sorghum hybrid. High temperature stress after growing point differentiation (approximately 30 days after emergence) delays heading1 and decreases seed set (number and size of seeds), affecting final yields. Delayed planting may result in delayed pollination. If pollination occurs later than normal during the growing season, it increases the likelihood of the crop being exposed to excessive heat at blooming, which could jeopardize yields and final grain numbers. Temperatures below 40°F during grain-fill can negatively impact the ability of the plant to fill the grains, thus affecting final yields. Hybrid selection also affects the length of time from planting until mid-pollination; short-season hybrids have a shorter time from emergence to flowering than the full-season hybrids, and therefore have lower yield potential compared to the full-season hybrids.
Early Harvest Area (EHA)
Sorghum heading in the EHA was concentrated from late-June to early-August, the time during which the most heading progress was made. Wetter than normal conditions and near-average temperatures dominated the vegetative period until pollination time. Excess precipitation in some areas may have challenged tiller production and slowed plant growth, consequently reducing nutrient uptake and impacting potential yield. In addition, heading progress was slightly delayed during July, compared to the average for the 2011-2015 period. However, the cool temperatures favored the blooming process, resulting in low probability of grain abortion. While normal or slightly above-average temperatures occurred during the grain-fill period, the main challenge for sorghum’s production environment was related to the wet conditions at the end of the season.
Late Harvest Area (LHA)
Sorghum heading for the LHA spanned from early-August to early-October, with more than 50% of the LHA crop heading during the month of September. For the northern section of this area, if flowering took place in early- to mid-September, the probability of reaching maturity before the first freeze was lowered because of the lack of accumulation of growing degree days2. Conditions for the late vegetative heading phase remained wet, but with average temperatures. These conditions favored the pollination time and the early phase of grain-filling, which in turn, positively impacted potential seed size. Across the LHA region, the grain-fill period went from a wet to dry moisture condition, and experienced normal to slightly above-average temperatures. The impact of the warmer temperatures on yields varied, depending on the timing of the crop development; late-planted crops had a shorter grain-fill period than the early-planted crops.
[1] Heading, the process in which sorghum heads are exerted and visible on the plant tops, occurs after boot stage and before flowering.
[2] Growing degree days is a parameter related to heat accumulation in order to predict plant development stages.
D. Maturity and Harvest Conditions
Wet conditions and near- or slightly above-average temperatures favored harvest
When the sorghum plant reaches physiological maturity (or black layer), the grain achieves its final maximum dry mass and nutrient content. Prior to reaching the black layer stage, freezing temperatures could lower test weight (through small seeds), impede final maturity, and consequently reduce yields. Once maturity has been reached and until harvest time, sorghum grain will dry down from about 35% to around 20% moisture. The dry down rate is influenced by hybrid maturity, grain moisture at the beginning of dry down, and temperature during the dry-down period. If sorghum does not dry down sufficiently, the higher-moisture grain remains soft and becomes more susceptible to pericarp breakage, as well as becomes more difficult to thresh.
Early Harvest Area (EHA)
The majority of EHA sorghum was harvested by the end of August. From late-June to early-August, harvest progress was 20% above average for the 2016 growing season compared to the average of the 2011-2015 period. Overall, the 2016 growing season was ahead of or near the average for the 2011-2015 period for planting, heading, and harvesting. The main weather factor for this season was the constant wet conditions extending from planting to harvest. The wet conditions were excessive in some specific areas, affecting growth and crop yield potential. For this area, freeze has not been an issue. The main production issue for the EHA in 2016 was the sugarcane aphid (Melanaphis sacchari), which infested and damaged some of the crop. The infestation of this pest can impact plant health, final grain number and seed weight, and consequently yield and grain quality. Data are still being collected to understand the main effects of this pest on sorghum yield and quality.
Late Harvest Area (LHA)
While the greatest LHA harvest progress was from late-September to early-November, close to 80% of the LHA sorghum crop was harvested by late-October. Harvest progress in 2016 was slightly ahead of the average for the 2011-2015 period. Similar to the EHA, LHA average planting progress for 2016 was close to the average planting progress for the 2011-2015 period. However, heading and harvesting progress in 2016 were ahead of the average for the 2011-2015 period. The main weather factor affecting the 2016 crop in the LHA was the moisture condition, remaining wet from the planting season until well after pollination. Similar to the 2015 season, there was also no widespread early freeze that may have slowed maturity and enabled pericarp-cracked grain or led to harvest and disease issues. In the northern section of the LHA, specific areas may have been affected by early freeze temperatures, and therefore possibly interrupting grain-filling and affecting grain size and quality.
In specific areas across the LHA, the early-season wet conditions created an environment that could have caused poor root establishment and compaction problems. Wet conditions prevailed until late pollination and early grain-filling. During the current growing season, the sugarcane aphid (Melanaphis sacchari) impacted sorghum production, primarily from the mid-vegetative to late-reproductive stages, in the Texas Panhandle region and areas in Oklahoma. It also was introduced to new areas by advancing to North Central Kansas. Depending on when this infestation took place, aphids could have impacted yield by affecting the leaf area. The aphids could have also affected yield later in the crop development when seed is set by impacting the number of grains set and their weight, and thus potentially also affecting grain quality. In addition, sooty mold fungal disease was encountered in some plants affected by the aphids, consequently reducing yield and quality.
E. Comparison of 2016 to 2015 and 2011-2015
2016 was ahead on planting, heading, and harvesting
Early Harvest Area (EHA)
While the average 50% planting progress milestone was around early-April in the 2015 season, producers in the EHA reached 50% planting progress about one month earlier in 2016 (mid-March). The 2016 planting progress was similar to the average planting progress recorded for the 2011-2015 period. Planting progress by mid-April in 2016 (80%) was 30% ahead of the 2015 season (50%).
Despite the early-season precipitation slowing plant growth, the 50% heading progress threshold for the 2016 season (mid-July) was ahead by approximately three weeks compared to the 2015 season (early-August). Heading progress for the 2016 season was similar to the average for the 2011-2015 period.
From the late reproductive phase until harvest, wet and warmer grain-fill conditions improved the crop. Harvest progress for the 2016 EHA was two weeks ahead of the average of the 2011-2015 period, until 80% of the crop was harvested by the end of August. For the EHA, freeze events were not of concern for reducing yields and impacting grain quality.
Throughout much of the 2016 season, the sorghum crop in the EHA had a steady Good or Excellent crop condition rating that varied around 60%. The average rating improved until the crop reached the heading phase and then declined below a 60% rating of Good or Excellent. This rating reflected the challenges in sorghum production experienced early in the 2016 growing season, including wet early-season conditions, which affected plant growth and yield potential. The lowered crop rating also reflected the wet conditions that extended late into the season and pest infestation, both of which affected yield.
Late Harvest Area (LHA)
In 2016, sorghum producers experienced similar conditions to the 2015 season up until late May. After this point, farmers made steady progress, moving from 20% to 80% planted progress in only three weeks (until mid-June). This progress quickly outpaced 2015 LHA planting progress. Overall, 2016 planting progress was similar to the average of the 2011-2015 period.
Weather conditions in 2016 favored crop progress from the vegetative stage until heading time. Fifty percent of the 2016 crop was heading in early September, and this progress was approximately two weeks earlier than in 2015 and the average of the 2011-2015 period. From the late reproductive stage until harvest, drier and warmer grain-fill conditions hastened maturity and harvest time, with crop progress for 2016 ahead of 2015 and the average of the 2011-2015 period. Freeze events were of concern for reducing yields in the LHA, but problems were isolated to the north-central and northwestern sections.
The 2016 LHA sorghum crop condition rating was near 70% from early planting until harvest. This crop condition rating implied good plant health, normal vegetative development, and good plant growth. The average crop condition for the 2011-2015 period was at or below 50%, portraying a better season for 2016 relative to the average for the 2011-2015 period. The more favorable sorghum conditions in 2016 than in 2015 were also reflected in the projected slightly higher yields in 2016 than in 2015.