Issue 27
March 2000

Can you plant sprout-damaged seed and still get a good crop?

By Dr. Michael Peel,
NDSU Extension Small Grains Specialist
mpeel@ndsuext.nodak.edu

Weather conditions during the small grain harvest of 1999 resulted in higher than normal levels of pre-harvest sprouting in wheat, durum, and barley.  The effects of sprouting can be detrimental to seed viability and seedling vigor.  Before planting sprout-damaged seed, a determination of potential impact on productivity should be made.

Sprouting, or germination, generally only occurs when a kernel has matured and dried to a harvest ripe stage.  Germination then begins when a kernel absorbs water which activates a number of enzymes that break down starch and proteins producing some basic constituents required for respiration.

Sprouting or the germination process can be initiated multiple times in barley and wheat. The process has the indirect effect of lowering test weight and each time it occurs the viability of the seed will be reduced.  The lowered test weight is a result of seed swelling and loss of carbohydrates due to expenditure of energy.

Identifying sprout damage

The extent of sprouting can be evaluated in several ways. The simplest and probably most effective way is to visually inspect the seed. Visible indicators of pre-harvest sprouting include weathered appearance, seed swelling, a split seed coat leaving the embryo exposed, and emergence of the coleoptile and radicle (the seedling shoot and root).   In wheat and durum, a falling number test is used to measure the level of enzyme activity.  Falling numbers below 300 generally indicate pre-harvest sprouting has occurred.

The effect of pre-harvest sprouting on germination and seedling vigor is correlated to the extent of damage.  Research data is limited but indicates that sprouted kernels with no visible damage to the germ perform well in standard germination tests.  Seed with low levels of pre-harvest sprouting can have germination that is nearly as good as that of undamaged seed. However, when such seed is subjected to accelerated aging the percent of germination can drop dramatically.  Seed with an exposed germ or ruptured seed coat where either the radicle or coleoptile emerged perform less in standard tests.  Furthermore, seed with exposed germ structures is susceptible to physical damage during handling.

Impact on performance

The impact on performance depends on the level of sprouting, seeding environment, and environmental conditions during early crop growth.

Emergence of seedlings from severely sprouted grain, exposed germ and shoots, can be one third of total planted seed.  Poor emergence can be further compounded by deep seeding.  A typical seedling mortality of undamaged wheat or barley is in the range of 10 to 20%.

Recommended plant populations for wheat and barley are 1.2 to 1.3 million plants per acre.  Under favorable growing conditions, sufficient moisture and cool conditions during vegetative growth, plant populations of 0.5 million will yield nearly the same as 1.3 million plants. That's because under the favorable conditions, plants will tiller sufficiently to compensate for a smaller plant population.  However, under hot dry conditions wheat and barley switch very quickly from vegetative to reproductive growth.  This results in less tillering and a smaller yield potential from the reduced plant population.

Planting sprout-damaged seed can compound anything that impedes the ability of a new seedling to emerge and produce leaves required for good seedling vigor.  These conditions may include waterlogged soils, dry soils, and crusting.

Seed treatments are usually recommended when seeding in cool wet soils typical of ND and northwest MN.  However, seed sprouted to the point that the seed coat has split and exposed the germ can be damaged by the seed treatments.

Before using sprout-damaged seed, the percent germination should be determined so seeding rate can be adjusted accordingly. Percent germination can be easily determined using a simple paper doll test.  Simply place 200, or more if you feel inclined, randomly selected seeds on heavy duty paper towels, roll the towels up and secure the role with paper clips, wet the towel and place it in a bread bag.  Then place it in a location that remains about 50 to 60o F.  After two days count the germinated seed and divide that number by the total tested for percent germination.  (This test is only as representative of a seed lot as the sample used.)  Thus, if 184 of 200 kernels germinate, your percent germination is 92%.  To compensate, increase seeding rate by 8%.  When percent germination falls below 90%, consider using a different seed lot.

The conservative approach when deciding if a seed lot should be used is to determine the potential impact.  A few simple guidelines can be followed:  Seed that has sprouted so severely that the radicle and coleoptile are visible should not be used.

• Wheat or barley known to have sprout damage with low test weight (less than 56 lb/bu for wheat and 42 lbs/bu for barley) should not be used.

• If sprout-damaged seed is used, increase seeding rate to compensate for reduced germination. Increase seeding rate by 1% for each 1% decrease in percent germination.

• Do not use sprouted seed that has been stored for more than one year.