Maize for Silage
Insight 348


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The ideal harvest drymatter content for maize silage is 30-38%. There are a number of reasons why growers may need to harvest crops earlier than 30% drymatter.

These include:

  • To fill a severe autumn feed deficit
  • Where crops have failed to reach harvest maturity. This can occur when maize is planted in marginal areas, the hybrid that is of too long a maturity is chosen, planting is delayed, the growing season is cool or a combination of these factors.
  • Where plants have been damaged by frost, flood or wind which has slowed the rate of plant development.  


Maize silage yield increases rapidly during the 6 - 8 weeks prior to the ideal harvest point (30 - 38% drymatter) as grain yield accumulates. Early harvested crops produce less yield. Silage quality may also be reduced due to slightly lower plant nutrient levels and/or poorer fermentation quality.

The dry down rate of maize silage varies according to heat unit accumulation but is typically between 0.2% (in cool weather) and 0.5% (in warm weather) per day. Waikato data shows that a maize silage crop harvested at 25% or 28% drymatter will produce 15% or 8% respectively less drymatter yield than when harvested at the ideal drymatter (30 - 38%).


It is important to weigh up the risks and benefits of early harvesting your crop before harvest commences. If harvest must proceed, following the guidelines below will help maximise silage quality.

  1. Measure the actual crop drymatter. Take a representative sample of at least six plants and roughly chop them. Submit them to a commercial laboratory for drymatter analysis. This will help you determine the best management strategy for crop harvest.
  2. Ensure that chop length matches crop drymatter content. Wet crops (<30% drymatter) should be chopped at 18 - 20 mm theoretical chop length to reduce the risk of run-off from the silage stack.
  3. Lift the cutter bar. The bottom part of the plant contains a significant amount of moisture. While lifting the cutter bar on the forage harvester will reduce yield, it will also increase the drymatter content of the material that is harvested. This improves the chance of a quality fermentation and decreases the amount of effluent run-off. Silage effluent is undesirable because it contains valuable nutrients. It is also a powerful biological pollutant New Zealand research has shown that lifting the cutting height from 100 mm to 300 mm increases silage drymatter by 1.5% but decreases yield by 1 tDM/ha. Lifting the cutter bar from 100 mm to 600 mm increases silage drymatter by 3.4% but decreases yield by 2.5 tDM/ha.
  4. Inoculate with Pioneer® brand 11C33 maize silage inoculant. Immature crops have high sugar levels and are more susceptible to poorer aerobic stability. (Aerobic stability is a measure of how long silage remains cool and retains its quality after the stack is opened at feed-out time). Inoculating with 11C33 will improve fermentation quality and reduce the risk of heating at feed-out time. While silage inoculated with 11C33 can be fed immediately after harvest, maximum aerobic stability gains will be made when it is fermented 30 days prior to feeding
  5. Turn off the plant processor. Immature crops will have a reduced amount of starch that is very soft. Processing will result in stover cell damage resulting in increased silage effluent.
  6. Employ good harvest and stack management techniques. Ensure that the material is harvested as quickly as possible. Compact it well but do not over compact as this will increase effluent run-off. Ensure the stack is well sealed. The cover should be weighted down with tyres that are touching and any joins in the cover should be taped. Seal the edges of the stack using sand or lime. Careful feed-out management (e.g. keeping the stack face tight at feed-out time is also critical.
  7. Keep the silage separate. In most cases, it is better to keep immature maize silage separate from higher quality maize silage harvested at the correct time. If you mix the silage you run the risk of a bad fermentation in the whole stack. 


The feed value of wet maize silage depends partly on the degree of crop maturity at silage harvest time. In general it will have higher fibre levels, slightly higher crude protein, lower starch, slightly higher sugar and slightly lower energy content than maize silage harvested at the ideal time.  It is recommended that a representative maize silage sample is taken 30 days after harvest and sent to a commercial laboratory for feed analysis. Your local Pioneer representative can help you to interpret the results and can also provide feeding recommendations.

Contact your local Pioneer representative to arrange a free, no-obligation visit.


Immature Corn Silage. Bill Weiss. Department of Animal Science Ohio State University.

Harvesting Immature or Mature Corn Silage. Dr Limin Kung. University of Delaware.

Management Recommendations for Harvesting Hail-Damaged Corn as Silage. Nutritional Insights. Pioneer Hi-Bred International 2001.


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Revised: Dec 2019
Expires: Dec 2022