Tuesday, December 10, 2013

Rain Wreaks Havoc on Corn Silage Quality in 2013

This article was originally written for and distributed to farmers and other members of the agricultural industry in western New York.

Preliminary analyses are indicating that the quality of new crop corn silage is considerably lower in 2013 than in 2012. Higher fiber content, lower fiber digestibility, lower starch content, and smaller ears can all be linked back to higher than normal rainfall this year. Slower than normal dry-down also delayed corn silage harvest on many farms. However it appears that BMR varieties have weathered the storm better than conventional varieties.

2013 Corn Silage
In the November 2013 edition of Hoard’s Dairyman, Dr. John Goeser of Rock River Laboratory discusses the decreased corn silage quality in the Midwest and the Northeast, Figure 1. “Starch levels have decreased and NDF (fiber) levels have increased, decreasing energy levels. To make matters worse, TTNDFD (total tract fiber digestibility) has also dropped from last year’s crop.”

Figure 1. Midwest and eastern U.S. region corn silage crop quality from 2011 to 2013.

The data from the Northeast region included 2012 & 2013 samples from over a dozen farms in western New York, Figure 2. Samples included conventional hybrids, BMR varieties, along with some Shredlage corn silages.

These changes in fiber content and fiber digestibility are due to the higher than normal rainfall experienced in both regions. Like all plants, corn transfers water from its roots, through its xylem, and out its leaves into the atmosphere. Think of the corn plant as a giant straw. In wet years that straw needs to move a lot more water from the soil into the air. The plant senses this and reinforces the strength of the xylem by adding more cellulose (increase in NDF) and more lignin (decrease in total tract fiber digestibility) in order to handle the increased evapotranspiration load.

Despite these overall trends there were considerable differences between the BMR and the conventional varieties, Table 1. BMR samples had no change in CP content, while conventional varieties lost 0.5% on average. BMR samples also had higher CP content (~0.5% in 2012 and ~0.9% in 2013) than conventional varieties. While all corn silage had increased NDF in 2013, the BMR corn silage experienced less than half the increase (~1.3%) seen in conventional varieties (~4%). Surprisingly, the lignin content actually dropped in BMR varieties (-0.5%), but increased as expected in conventional varieties (+0.2%). BMR varieties also had increased starch content in 2013 (+1.6%) compared to the drop in starch (-3.5%) in conventional varieties. Fiber digestibility as measure by TTNDFD and Dynamic NDF kd also showed that BMR silages dropped less than conventional silages in 2013.

Table 1. BMR & Conventional Corn Silage from Western NY 2012 & 2013
*CP = crude protein %DM, NDF = neutral detergent fiber %DM, Lignin & Starch are % DM, TTNDFD = total tract NDF digestibility, Dynamic NDF kd = % of NDF digested per hour.

Besides changing the plant physiology of the corn silages, forage quality was changed by the high rainfall conditions through high losses of nitrogen throughout the region. Many farms went back in and put on 50-60 lbs/acre of nitrogen as a side-dressing or through drop-nozzles at tasseling. Numerous fields that did not receive any additional nitrogen had smaller than normal ears as a result.

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