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How Growing Conditions Affect Silage Quality


How Growing Conditions Affect Silage Quality

Growing environments have a tremendous influence on silage quality. The same hybrid grown in different locations during the same year can deliver significantly different relative silage yields, starch content and neutral detergent fiber digestibility (NDFD). That’s why universities and seed companies only compare different hybrids grown side by side in the same location.

It’s not valid for nutritionists to peg hybrid genetics as the primary cause of nutritional differences, says Bill Mahanna, Ph.D., DuPont Pioneer Global Nutritional Sciences Manager. The influence of growing conditions (especially moisture) is a major source of the nutritional variability within hybrids across years and locations.

The University of Illinois attributes 19% of grain yield performance to hybrid genetics. The remaining influences are the result of weather (27%), nitrogen (26%), the previous crop (10%), plant population (8%), tillage (6%) and growth regulators (4%).

Is Dry, Moderate Heat Ideal?

Studies suggest cool, dry years are best for corn silage quality. In fact, slight moisture stress might actually stimulate grain production. Accumulated growing degree days after silking are the most important in affecting corn silage nutritional value because that influences grain (starch) yields.

The specific timing of environmental stress during the development of the corn plant also is important. Weather before and after silking may interact to affect the final corn silage nutritive value. Growing conditions prior to silking affect corn plant height (and yield) and fiber digestibility; growing conditions after silking appear to exert a stronger effect on corn grain yield and total dry matter digestibility.

A 2013 field study by DuPont Pioneer looked at five genetically different corn silage hybrids grown in 15 environmentally diverse locations in Michigan. This study showed that the growing environment had a highly significant effect on yield, starch content and NDFD. Total accumulated growing degree days positively influenced starch content. Precipitation for the entire growing season ranged from 14.0 to 25.5 inches and was negatively related to crude protein (likely due to nitrogen leaching) and NDFD. Locations that received fewer than 16 inches of precipitation had lower yields but greater NDFD (48.3% versus 45.8%).

What Causes NDFD Variation

University and seed company plots show minimal genetic differences (3% to 4% units) among silage hybrids for NDFD (excluding brown midrib hybrids). The variation in NDFD that nutritionists observe — from farm to farm and from season to season — is due more to environmental factors such as growing conditions and harvest timing. Nutritionists working in the Midwest and East, with fewer irrigated acres and more weather variability, struggle to quantify and manage corn silage digestibility. In general, dry conditions during stalk development enhance fiber digestibility while wet conditions that improve whole-plant yield tend to reduce fiber digestibility.

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