Maize for Silage
Insight 302


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The timing of silage maize harvest and harvest management factors such as chop length and compaction have a major impact on the quality and quantity of the resultant silage. Most farmers rely on contractors to harvest their crops. Choice of contractor is an important step in ensuring a quality product.


Choose a reliable contractor with well-maintained equipment. Ensure that he is prepared to vary chop length and processor settings if crops are too wet or too dry. Book your harvest contractor as soon as your crop is in the ground.  Make sure that he can apply Pioneer® brand 1132 or 11C33 maize silage inoculant to your crop as it is harvested. Keep in touch with your contractor as your crop nears maturity.


The ideal time to harvest your maize silage crop is when the whole plant drymatter is between 30 - 38%. Harvesting a crop too early will result in a yield sacrifice. High drymatter losses can occur as plant fluids run from the stack or bunker taking away valuable sugars and nutrients. Late harvest may result in a loss of quality as plant stover (leaf and stalk) increase in fibre and become less digestible. Dry crops are also difficult to compact properly. Please Note: Bulletins giving further details on the harvesting and storage of wet and dry maize crops are available. Contact your local Pioneer representative on 0800 PIONEER (0800 746 633) for a copy.

In a crop that is still green (i.e. not frosted or drought stressed), the first sign that harvest is approaching is the husk covers turn slightly yellow-brown. There are several ways in which you can determine when your crop is between 30-38% whole plant drymatter. Please note that the following guidelines should only be used to determine if the crop is ready to harvest. There is a Code of Practice for the Trading of Maize Forage available free of charge from the Foundation for Arable Research, PO Box 80, Lincoln 7640, or telephone 03 325 6353, or by visiting their website: This document outlines weighing as well as drymatter testing requirements for trading crops. A four page summary of this Code of Practice is also available, either from the Foundation of Arable Research or by phoning Pioneer toll-free on 0800 PIONEER (0800 746 633).

1.Milk line

The whole plant drymatter can be estimated by looking at the milk line of the grain. To check whether your crop is in the range of 30 - 38% drymatter:

  1. Take a cob from a plant that is at least 20 rows into the crop. The plant that you take the cob from must be in a uniformly planted row.
  2. Break / snap the cob in half and discard the end of the cob that was attached to the plant.
  3. Hold the point of the cob downwards and remove a kernel from the "snapped" end.
  4. Keep the kernel the same way up as when you removed it from the cob. Slide your fingernail along the length of the kernel starting at the flat (dented) end of the kernel.

  5. Note the point where the solid starch ends and the liquid milk begins. The maize hybrid will be ready for harvest when the milk line is two thirds of the way down the kernel (see Fig 1).
  6. The milk line test is only indicative that harvest time is near. The only sure way to test plant drymatter is though the microwave test or by sending a plant to a suitable laboratory (see the next two points).

2. Plant moisture content

The moisture content in the plant (leaves and stem) can vary widely.

A drought stressed crop may have all leaves up to the cob browned out and no moisture in the stem. In such situations the drymatter percentage of the crop can be higher than the milk line indicates.

3. Microwave drymatter test

Call the Pioneer toll-free on 0800 PIONEER (0800 746 633) to obtain a bulletin detailing how to do a microwave drymatter test.

4. Laboratory analysis

Many commercial laboratories can measure the drymatter content of chopped whole plant maize samples. Some can also handle whole plants. It will take at least three days for your samples to be processed and often considerably longer. Remember that the result of a drymatter test will only be accurate if a good representative sample is submitted.


Inform your contractor once you have determined that your crop is close to harvest. Make sure that you organise all the machinery, labour and supplies (e.g. cover, Pioneer® brand inoculant and tape) that will be required if these are not supplied by the contractor.

Chop length

The ideal chop length is 10 - 15 mm. This is a theoretical chop length and you will find some particles that are shorter or longer in your silage. Some longer particles are beneficial as they stimulate the rumen of the animal that is being fed.  If your silage is very dry (greater than 38% drymatter), decrease the chop length to 5-9 mm. In the case of very wet crops (less than 30% drymatter) chop length may be increased up to 20 mm.

A good method of testing whether the chop length that you are using is correct for the moisture level is to take a handful of the harvested maize and squeeze it. The palm of your hand should feel moist. If you can wring water out of the material, you are almost certain to have run-off from your silage stack. Either increase the chop length or delay the harvest. On the other hand, if the maize silage does not stay compressed after squeezing, the maize is too dry. Chop length should be shortened.

Kernel Processing

Use a kernel processor to ensure that 99% (target minimum 80%) of the kernels are broken into at least four pieces.

Pioneer® brand 1132 maize silage inoculant

This is a bacterial silage inoculant that is used to enhance silage quality. Pioneer® brand 1132 contains bacteria that are specially selected to give a faster, more efficient fermentation. As a result you get more milk or meat per tonne of forage ensiled.

Pioneer® brand 1132 is water soluble and non-corrosive.  Most contractors have the equipment to apply 1132 as your silage is chopped. Make sure that you have adequate inoculant to treat the entire harvested crop.  Inoculant requirements for a range of crop drymatter yields are shown in the table below:

Crop yield (tDM/ha)*Small bottles (treat 50 tonnes)
of 1132 or 11C33 (per ha)
20 1.21
22 1.33
24 1.45
26 1.58
28 1.70

*Inoculant is applied on a wet tonne basis.
Wet tonnes = dry tonnes divided by the drymatter content.

In this table we have assumed that the drymatter percentage is 33%.

Pioneer® brand 11C33 maize silage inoculant

11C33 contains a unique blend of Lactobacillus plantarum and Lactobacillus buchneri giving excellent drymatter recovery while also minimising losses at feed out time.  When compared to the control in trials, 11C33 improved drymatter by 2.5% and reduced heat giving longer bunklife and silage stability.

For information on the storage of maize silage see Pioneer Technical Insight 303: Storing a Maize Silage Crop.

For more information call the Pioneer Advice Line toll-free on 0800 PIONEER (0800 746 633)

Pioneer® brand products are provided subject to the terms and conditions of purchasing, which are part of the labeling and purchase documents.

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The information in this publication is general in nature only. Although the information in this publication is believed to be accurate, no liability (whether as a result of negligence or otherwise) is accepted for any loss of any kind that may arise from actions based on the contents of this publication.

© 2021, Genetic Technologies Limited. No part of this publication can be reproduced without prior written consent from Genetic Technologies Limited.

Revised: Nov 2020
Expires: Nov 2022