Dr. Seth. L. Naeve and Dr. James H. Orf

The American Soybean Association and the US Soybean Export Council have supported a survey of the quality of the US soybean crop since 1986.This survey is intended to provide new crop quality data to aid international customers with their purchasing decisions for the upcoming year.

According to the October 12, 2007 United States Department of Agriculture, National Agricultural Statistics Service (USDA-NASS) crop report, the total US soybean production area is expected to decrease 16% from last year to 25.4 million hectares harvested. With average yields also expected to be lower than in 2006, total US soybean production is expected to be only 70.8 million MT. If realized, this will be only slightly larger than the poor 2003 crop, of 66.7 million MT, and a large decrease from 2004-2006 crops that averaged 85 million MT (Table 1).

By August 24, 2007 sample kits were mailed to 9,193 producers. Producers were selected based on total land devoted to soybean production in each state, so that response distribution would closely match soybean production. One thousand six hundred eighty five samples were received by October 31, 2007. These were analyzed for protein and oil concentration by near-infrared spectroscopy (NIRS) using a Perten DA7200 diode array instrument (Huddinge, Sweden) equipped with calibration equations developed by Perten in cooperation with the University of Minnesota. Regional and national average protein values were determined by computing weighted averages using state and regional soybean production values, so that average values better represent the crop as a whole. Results can be found in Table 2.

Foreign Material (FM) was estimated by sieving and handpicking non-soybean material from each sample according to Federal Grain Inspection Service (FGIS) standards where, “Foreign material is defined as all material that readily passes through an 8/64 inch (3.2 mm), round-hole, perforated sieve and any material other than soybeans remaining atop the sieve.” For this analysis, splits and otherwise broken soybeans were not considered. Foreign material is simply provided on a percentage basis. Seed weights were estimated by counting and weighing 1000 seeds from each sample. Foreign material and seed weight summaries can be found in Table 3.

Some international customers have expressed interest in soluble sugar concentrations within the US soybean crop. Soluble sugars are difficult to accurately quantify by traditional wet chemical analysis and NIRS technology. A small subset of samples (41) were randomly selected to represent total soybean production by state, and analyzed for soluble sugar concentrations using high performance liquid chromatography (HPLC) at the University of Missouri Analytical Laboratories. Results can be found in Table 4.

^1.Prepared for the American Soybean Association and the United States Soybean Export Council Quality Mission to Asia, 12-19 November, 2007
^2.Assistant Professor and Professor, respectively, Department of Agronomy and Plant Genetics, University of Minnesota, St. Paul, MN 55108

Average protein and oil concentrations for the overall US soybean crop were similar, to those described in the 2006 quality survey. Average US soybean protein concentration was 0.9% higher in 2007, at 35.4% and average oil was 0.5% lower, at 18.7%, when compared with 2006 (Table 5). Region by region analysis indicates almost identical trends as were seen in 2006, except that regional protein concentrations tended to be nearly 1 percentage points higher, while oil was about 0.5 percentage points lower.

Foreign material found in samples was on average very low.Foreign material among 1685 farmer collected samples averaged 0.37%, with an overall range of 0 to 28%.Of 1685 samples, 1611 had FM below 1%, and 74 (4.4%) had FM greater than 1%.Only 23 (1.4%) had FM above 2%.While there was a tendency for samples harvested from Southern states to have somewhat above average FM, individual samples with above 2% FM could be found in all regions.

Seed size does provide some insight into the environmental conditions present during the production season.Seed size can also be correlated with changes in protein and oil concentration due to these same environmental conditions.In general, environmental stresses such as drought in the early seed filling period (late July and early August) tend to reduce the number of seeds on individual plants, if conditions return to normal later these remaining seeds can expand resulting in larger than average seeds size.Alternatively, stresses at the end of the seed filling period (late August through September) reduces the energy available for each seed and seed size may be smaller than average.

In 2007, seed size tended to be largest in Northern Iowa, Sothern Minnesota, Wisconsin, Michigan, as well as several East coast states. Seed size tended to be smaller across the Southern ranges of the US soybean production area.The large seed size noted in the northern states in 2007 is likely due to midseason drought that occurred in this range.Late season rainfall allowed the smaller number of remaining seeds on each hectare to fully expand and enlarge.Smaller seeds in the southern states are likely do to the season long drought found there.

A large sample-to-sample variability in all soluble sugar values was identified (Table 4). This indicates that local environmental conditions may play a large role in determining relative concentrations of important soluble sugars. On average, samples contained 39.4 mg / g sucrose, 34.6 ma / g stachyose, and 7.6 mg / g raffinose. Southern states tended to have lower concentrations of sucrose and stachyose and higher concentrations of raffinose. This same trend was noted in the 2006 survey.

April average daily temperatures were below normal across most of the Midwest, following much warmer than normal temperatures the last ten days of March. Early April temperatures averaged 7-11°C below normal across the Midwest. In Minnesota, the first week of April brought a spring snow storm, and the third week brought 2-3 times normal weekly precipitation in the form of showers and thunderstorms. Spring flooding at various locations in the Midwest persisted throughout April.

May average daily temperatures were generally above normal for almost all of the Midwest. Precipitation was generally above normal, resulting in flooding across North central Missouri and Southwestern Iowa, slowing planting but not generally adversely affecting crop conditions. Moderate drought conditions set in across parts of Missouri, Kentucky, Minnesota, Wisconsin, and Ohio; this assisted planting greatly.

June rainfall was below normal for many parts of the Midwest in the first part of the month, but late June rains across most of the region eased concerns for the developing corn and soybean crops. Most of Kentucky, and southern Ohio, however, were in severe drought. June temperatures were generally near normal.

July was unusually cool and dry. Approximately 75% of the Midwest region experienced drought conditions. Beneficial rains fell over portions of the region (Iowa, Illinois, Indiana, Ohio, and Kentucky) later in the month, but areas of Minnesota, Iowa, Missouri, and Wisconsin were missed by the rains and experienced their driest Julys in recorded history.

August saw severe drought conditions in the northern and southern thirds of the Midwest, while the central third received record rainfall resulting in major flooding. Maximum temperatures records were set in the southern Midwest through southern Illinois, southern Indiana, Kentucky, and parts of Ohio.

September was a mixture of near normal and well above normal temperatures in the Midwest. Rain fell where it was cooler and not where it was warmer. In the northern half of the Midwest drought conditions improved from near record rainfall, but drought conditions in the southern portion of the Midwest continued, and were beginning to again move northward into Illinois, Indiana, and Ohio. Temperatures were warmer than normal for much of the region, but not record-setting.

Overall, the midseason drought affected soybean yields more than any other weather phenomena. It significantly reduced yields in major soybean producing states such as Minnesota, Iowa, Illinois, Indiana, and Missouri.

The most serious production problem for individual US producers was found in the southeastern US where an extreme drought affected soybean crops throughout the season, especially during the late season. The drought had a major affect on yields in eastern states of North Carolina, Virginia, and Maryland, as well as mid-south states of Tennessee and Kentucky. In theses states, yields are expected to be reduced by one-third when compared with last year, and total production is expected to be down by 43%.

Soybean Rust (Phakopsora pachyrhizi) is a fungal pathogen of soybean that is know to cause very large yield losses in South America. Soybean rust was first reported in the continental US in November of 2004. Soybean rust is spread by spores, but it requires a living host to remain viable over winter periods. In the US it is known to over-winter on a weedy plant - kudzu - in areas of Florida and extreme southern Texas. Outbreaks of soybean rust on commercially produced soybean crops were noted since 2005. Each year, soybean rust has spread further into the central soybean producing regions of the US. In 2007, soybean rust was identified in 19 states, including Iowa, Illinois, and Missouri. However, rust was identified very late in the season, after it would affect soybean yields or composition. Applications of fungicides to reduce losses from rust were not needed in most states. Fungicide application for rust was recommended only in Florida, Mississippi, Louisiana, Arkansas, and Oklahoma. In these states, rust suppression through fungicide applications has reduced production losses to the disease to extremely low levels. While producers in the Central soybean producing region are more cognizant of the potential for rust and rust management, it currently appears that future large scale rust infection and subsequent fungicide applications will be rare, at best.

National Agricultural Statistics Service. 2007. Available at http://usda.mannlib.cornell.edu/usda/current/CropProd/CropProd-10-12-2007.pdf (verified 7 November 2007). USDA-NASS, Washington, DC.

Federal Grain Inspection Service. 2004. Test Weight. In Grain Inspection Handbook II (Chapter 10). Washington DC: USDA-GIPSA-FGIS.