ISSUE 14  August 27, 2009

SUNFLOWER YIELD ESTIMATION

As sunflowers plants start to mature there is a curiosity about yield potential. The yield of sunflower can be calculated by the number of plants per acre, the head diameter, the seed size and the number of filled seeds per head. Yield is calculated by multiplying 2,450 by the "multipliers" from the charts below.

Plant population should be estimated from a number of locations within a field, away from the head lands. The number of plants per 20 feet of row can easily be established. With solid seeded sunflower it is much more difficult to get a good population estimate.

Sunflower population (in rows or solid seeded), plants per 20 feet of row and multiplier to be used in formula.

 Plants per 20 ft of Row Population 14" 28" Multiplier 14,000 7.5 15 0.70 15,000 8 16 0.75 16,000 8.5 17 0.80 17,000 9 18 0.85 18,000 9.5 19 0.90 19,000 10 20 0.95 20,000 10.5 21.5 1.00 21,000 11.3 22.5 1.05 22,000 11.8 23.5 1.10 23,000 12.3 24.5 1.15 24,000 13 26 1.20

The next estimate to establish is the sunflower head diameter. It is important to measure a number of heads in the field. Plants with more space tend to have larger heads.

Sunflower head diameter in inch and multiplier to be used in formula.

 Head Diameter (Inches) Multiplier Head Diameter (Inches) Multiplier 4.5 0.37 7.5 0.91 5.0 0.46 8.0 1.00 5.5 0.55 8.5 1.09 6.0 0.64 9.0 1.18 6.5 0.73 9.5 1.27 7.0 0.82 10.00 1.36

Photo: Average the head diameter by
selecting twenty-five or more sunflower
heads randomly. Try to avoid the

The next multiplier is related to the seed size. Remove several seeds approximately 2 inch from the edge of the head and compare to the seed outlines below.

Seed size and multiplier to use.

 Descriptor Light (L) Medium Light (ML) Medium (M) Medium Heavy (MH) Heavy (H) Multiplier 0.8 0.9 1.0 1.1 1.2 Size

Percentage good seed set: Cut a slice out of the sunflower head and hand remove the seeds and estimate as a percent the filled seeds. When observing 100 seeds of which 15 seeds are either not filled or severely damaged due to insects, the multiplier will be 0.85.

Center seed set: If no seed in the center one inch of the head, multiply by 0.975; if no seed in the center two inches of the head, multiply by 0.95; if there is a hole in the center of the head, multiply by 0.9.

Yield calculation

Yield is calculated by multiplying 2,450 by the multipliers from the charts above. For example: A plot with a stand of 18,000, a head size of 8 inches, a seed size ‘medium heavy,’ good seed count of 85 percent, and no seed in the center two inches.

Multipliers used: 2,450 x plant population x head size x seed size x seed count x center seed set = lbs/acre.

Yield calculations for this field would therefore be: 2,450 x 0.9 x 1 x 1.1 x 0.85 x 0.95 = 1,958 lbs/acre.

If bird damage is visible an estimate of the percent damage (and therefore percent seeds left in the head) can be used to adjust the yield estimate. With 5% of the seeds removed by birds the yield estimate in the example would be 1,958 x 0.95 = 1,860 lb per acre.

Hans Kandel
hans.kandel@ndsu.edu

SPROUT DAMAGE AND FALLING NUMBERS IN WHEAT

The recent rains in much of the state were much needed by the row crops, but were unwelcomed by those with un-harvested small grains. Not only did these rains delay an already late harvest, it raised concerns about grain quality and associated discounts at the elevator. Of most concern is pre-harvest sprouting. As kernels mature, they are resistant to sprouting until they reach physiological maturity. Unfortunately, most of the small grains in the state, though too wet to harvest, are physiologically mature (heads and peduncle lost all of their green color) and are therefore susceptible to pre-harvest sprouting. When mature kernels are subjected to proper moisture and temperature for sufficient time they begin to sprout. The physiological changes needed to produce a new plant require energy and nutrients, so the wheat kernel produces enzymes to breakdown starch (amylases), oil (lipases) and protein (proteases). When moisture levels in the wheat decrease prior to threshing, the sprouting process stops, and if it stops before there are visible signs of sprouting it is called incipient sprouting.

The impact of sprouting on foods produced from wheat depends on the amount of enzymes present and breakdown of the kernel. Sprouting lowers test weight and flour yield, lowering the grade and value to the processor. The impact on baking quality is observed by lower absorption (water added in baking, which reduces bread yield), reduced mixing strength and tolerance, and sticky dough. It can also affect loaf volume, crust strength and crumb texture, whereas a wet and gummy crumb causes problems with slicing and shelf life. The starch degradation and enzyme activity also reduce the quality of Asian noodles. The effects on durum are lower test weight, reduced semolina yield and color. In the processing of semolina and pasta, sprouting increases semolina speck counts, reduces shelf life of dried pasta (due to checking or cracking), increases cooking loss, and produces softer cooked pasta.

The level and impact of sprout damage are not fully realized until it is processed into bread or pasta. Nevertheless, one way that grain buyers can rapidly assess the amount of sprouting that has occurred is with the Falling Number test. The Falling Number test does not directly measure amylase enzyme activity, but measures changes in the physical properties of the starch portion of the wheat kernel caused by these enzymes during the test. In the Falling Number test, the grain is ground into flour and mixed with water in test tubes to form a slurry. The tubes are placed in a boiling water bath (212°F) and automatically stirred for 60 seconds, causing the starch-water slurry to thicken due to starch swelling or "gelatinization". When starch granules become gelatinized, they are increasingly susceptible to degradation by amylase enzymes, which consequently increases the rate of thinning in the slurry. After mixing, the stirrers are released at the top of the slurry and begin to fall. The falling number apparatus records the time for the stirrer to fall through the slurry. The rate at which the stirrer falls is directly related to the amount of starch degradation by amylase enzymes.

There are no standards for falling number, as it is not an official grading factor in FGIS grain inspection and grading process. Generally speaking for wheat, a falling number value of 350 seconds or longer indicates low enzyme activity and very sound wheat. As the amount of enzyme activity increases, the falling number decreases. Values below 200 seconds indicate high levels of enzyme activity. In recent years, grain buyers have discounted wheat for falling number values below 300 seconds. Falling number values are also important overseas, as many of the buyers from export markets have written minimum tolerances of 300 to 350 seconds into their purchase contracts.

When correctly run, the falling number test is fairly repeatable; however, contamination of the sample from a multitude of sources, including the grinder used to make the test flour, can decrease the falling number value. If a small sample of undamaged wheat is ground immediately following a sample with severe sprout damage, without adequate flushing or cleaning of the grinder, substantial contamination is possible. Requesting a second falling number test may improve the results if the grinder used was not adequately cleaned.

Varieties vary in the ability to resist pre-harvest sprouting. The University of Minnesota routinely screens HRSW varieties for this character and the performance of current varieties can be found in their 2008 variety trial publication: www.maes.umn.edu/09VarietalTrials/redspringwheat.pdf.

Brian Sorenson
Director, Northern Crops Institute
brian.sorenson@ndsu.edu

Joel Ransom
Extension Agronomist for Cereal Crops
joel.ransom@ndsu.edu