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When is maize ready to harvest?

Forecasting the expected date of maize harvest is extremely important to maximise crop value as well as planning rotations. Harvest date is mainly determined by the variety sown and the season.

Maize harvest is dependent on the geographical area, site, season as well as the variety maturity. When assessing a crop it needs to be checked in several locations and not just the perimeter.

The ideal harvest time is when cobs have reached maximum starch yield, have sufficient moisture to compact easily in the clamp and an ideal dry matter (DM) between 32-35%.

When is maize ready to harvest?

Early hybrids will have rapid leaf dieback and so offer a limited harvest window.

Not harvesting at the optimal stage will risk losing feed quality the more the crop over matures. Cutting too early will severely impact potential DM intake, in particular the availability of starch and energy. Poor feed intake, palatability and high acidity all result from maize ensiled before it reaches maturity. Harvesting too late will risk frost damage to the grain, causing moulds and spoilage once ensiled.

Effects of harvesting too early

  • High fresh weight yield, but not maximum DM yield. Water will be stored in the clamp.
  • Harvesting before optimum grain fill compromises starch content and yield. 
  • High fibre rich crop.
  • Compaction easy and ensiles well. Potential loss of nutrients through effluent production.

Effects of harvesting too late

  • Increased harvesting costs and increased field losses.
  • Low digestibility and palatability.
  • Poor clamp stability.
  • Difficult clamp consolidation which will require  a shorter chop length.
  • Soil damage / compaction.

How to assess maize crop maturity

Thumb Nail Test

For a quick in field assessment of crop maturity the thumbnail or the milk line test can be used. If you peel back the sheath on the cob the grains at the top of the cob should have a consistency which is comparable to soft cheese, whilst the grains at the bottom should be like hard cheese. Grains in the middle should just be able to take the imprint of a thumbnail.

Milk Line Test

Break the cob open half way down and remove one of the grain kernals. The milk line is where the solid starch ends and the liquid milk begins. The ideal is to have a 75 – 100% of the kernal yellow in colour (starch) instead of being milky and for no liquid to be excreted when pressed.

Maize - Milk Line Test

Check chop length and cutting height

Managing chop length and quality will help promote consistent feedout and high voluntary intakes. Optimum cutting height is 20cm above the ground level. The lower part of stalk has little feed value and high water content. Chop length has a major impact on the level of effective fibre ultimately provided in the silage. Typical chop length is 20-25mm

Short material will have insufficient effective structural fibre to maintain rumen health. Longer chop length will increase rumination time and rumen function. The kernels are the most nutritious part of maize and holds the starch. The kernels must be damaged or cracked so that they can be digested.

Successful ensiling and clamp management

Ensiling and clamp management is key to preserving the full value of silage but also an area where the biggest losses and waste can occur. Pre-harvest clean clamp of any old silage which cannot be used. A narrow clamp design to limit surface area exposed to air is the most ideal. Fill the clamp quickly but carefully in thin layers, consolidate well but rolling continuously and seal completely for rapid, anaerobic fermentation.

During feedout a tight cut will prevent moulding of the clamp face. Moving quickly across the face will prevent spoilage.

Additive special offers

Afbeelding: Maize additive shaker bottle

Losses are avoidable if maize is stored and clamped correctly and managed to prevent aerobic spoilage. Using an inoculant helps to encourage fermentation and will significantly reduce DM losses.

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For more information

For more information on maximising your maize, our range of additives or for advice please contact your local ForFarmers Forage Specialist or send us an online enquiry:

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