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Updated October 2020 URL: http://www.kingcorn.org/news/timeless/TestWeight.html grain Test load Considerations for Corn R.L. (Bob) Nielsen Agronomy Dept., chrischona2015.org Univ. West Lafayette, IN 47907-2054 email address: rnielsen at chrischona2015.org.edu Twitter:
The official minimum allowable test weight in the U.S. For No. 1 yellow corn is 56 lbs/bu and for No. 2 yellow corn is 54 lbs/bu (USDA-AMS (FGIS), 1996). Corn serial in the U.S. Is marketed top top the basis of a 56-lb "bushel" nevertheless of test weight. Even though grain moisture is not part of the U.S. Standards for corn, serial buyers pay on the basis of "dry" bushels (15 to 15.5% grain moisture content) or discount the market price come account for the drying expenses they intend to incur handling wetter corn grain.
Growers worry around low check weight because local serial buyers regularly discount their sector bids for low test weight grain. In addition, growers are naturally disappointed as soon as they supply a 1000 bushel (volumetric bushels, that is) semi-load of grain the averages 52-lb test weight because they only get paid because that 929 56-lb "market" bushels (52,000 lbs ÷ 56 lbs/bu) add to they receive a discounted price because that the low test load grain. On the other hand, high test weight grain makes growers feel an excellent when they provide a 1000 bushel semi-load that grain that averages 60 lb check weight since they will gain paid because that 1071 56-lb "market" bushels (60,000 lbs ÷ 56 lbs/bu).
These emotions encourage the belief that high test weight grain (lbs of dry matter per volumetric bushel) is associated with high grain returns (lbs. Of dry issue per acre) and vice versa. However, there is small evidence in the research literature that grain test weight is strongly concerned grain yield.
Hybrid variability exists for grain check weight, yet does not automatically correspond to differences in genetic yield potential. Grain test weight for a provided hybrid regularly varies from ar to field or year to year, but does not instantly correspond come the overall yield level of an environment.
Similarly, grain native high yielding areas does not necessarily have higher test weight 보다 that from lower yielding fields. In fact, test weight of grain harvested from severely stressed areas is occasionally greater than the of serial from non-stressed fields, as confirmed in Fig. 2 because that 27 corn hybrids grown at 3 locations with widely differing yield levels in Kansas in 2011. Another example from Ohio through 22 hybrids grown in typical in the dryness year that 2012 and the much better yielding year that 2013 also indicated no relationship in between yield level and also grain test weight (Fig. 3).
Conventional dogma suggests that short test load corn serial decreases the handling efficiency and quality of handle end-use commodities like corn strength (U.S. Seed Council, 2020), back the research literature does not repeatedly support this belief. Similarly, short test corn grain is regularly thought come be worse for pet feed quality, back again the research literary works does not support this belief (Laborie, 2019; Rusche, 2020; Simpson, 2000; Wiechenthal Pas et al., 1998). Even if it is or not low test load grain is inferior to greater test load grain may depend top top the reason of the low test weight in the an initial place.Common causes of low Grain Test load
The 2009 corn harvest season in Indiana (late chop maturation, so late harvest) was an instance of one wherein there were more reports of low test load corn grain than great or above average test weights. There were generally six determinants that accounting for many of the low test weight grain in 2009 and also four shared a usual overarching effect.
First and also foremost, growers should recognize that test weight and grain moisture room inversely related. The higher the serial moisture, the reduced the test weight AT THAT suggest IN TIME. As grain dries in the field or in the dryer, test load naturally boosts as lengthy as kernel integrity stays intact. Check weight increases as grain dries partly since kernel volume often tends to shrink through drying and also so an ext kernels pack right into a volume bushel and partly due to the fact that drier serial is slicker which tends to encourage kernels come pack an ext tightly in a volume bushel. Because of this in a year like 2009 with many of the early harvest reports of grain moisture ranging from 25 come 30% instead of the usual starting moisture level of around 20 come 23%, it need to not be surprising that test weights were reduced than expected.
Hellevang (1995) readily available a basic formula for estimating the rise in test weight through grain drying. In its most basic form, the equation is (A / B) x C; wherein A = 100 - dried moisture content, B = 100 - wet humidity content, and also C = test load at wet humidity content. The writer does not say, however I suspect this simple formula is most applicable in ~ a "normal" variety of harvest moistures; as much as moistures in the mid- to high 20"s.
Example: dry moisture = 15%, Wet humidity = 25%, Test weight at 25% = 52 lbs/bu.
Estimated test weight at 15% humidity = ((100 - 15) / (100 - 25)) x 52 = (85/75) x 52 = 58.9 lbs/bu
An older referral (Hall & Hill, 1974) provides an alternative suggestion for adjusting test load for harvest humidity that also accounts for the level that kernel damage in the harvested grain (Table 1). The table values are based upon the premise the kernel damage itself lowers test load to start with and that further drying of damaged grain outcomes in much less of an increase in check weight that what wake up in undamaged grain. Compared to the outcomes from making use of Hellevang"s an easy formula, adjustments to test weight making use of these tabular values have tendency to an outcome in smaller adjustments come test load for high humidity grain at harvest, but larger adjustments because that drier grain in ~ harvest.
Stress during Grain Fill
Secondly, thirdly, and fourthly; drought stress, late-season foliar leaf illness (primarily gray sheet spot and northern corn sheet blight), and also below common temperatures transparent September of 2009 all brought about a far-reaching deterioration of the crop"s photosynthesis machinery start in early on to mid-September the "pulled the rug out from beneath" the effective completion of the serial filling duration in part fields; resulting in less 보다 optimum strength deposition in the kernels. Fifthly, early October frost/freeze damage to late-developing, immature areas resulted in sheet or entirety plant fatality that efficiently put an end to the grain-filling procedure with the same an adverse effect on test weight.
Finally, ear rots (diplodia, gibberella, etc.) were prevalent throughout many locations of Indiana in 2009. Kernel damages by these fungal pathogens outcomes in light-weight, chaffy grain that likewise results in short test weight diseased grain, broken kernels, and also excessive level of international material. This cause of low test load grain obviously outcomes in worse (if not toxic) pet feed quality grain, i can not accept end-use processing aftermath (ethanol yield, DDGS quality, strength yield and also quality, etc.), and difficulties in save on computer the damaged serial without further deterioration.
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