Maize for Silage
Insight 324


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New Zealand dairy farmers, whether farming conventionally or organically, struggle with the same issue.  Namely, how do you consistently and profitably produce milk within a pasture based system? New Zealand dairy cows tend to have less than optimal lactation lengths and higher than optimal empty rates.  While there are a variety of reasons for this, lack of feed at critical times of the season is a key issue.  Conventional dairy farms have increasingly turned to supplementary feed to fill this feed gap. 

Making money out of quality home-grown supplementary forages is easy.  Firstly, stocking rate must be correct to ensure optimal pasture harvest throughout peak pasture growth periods. This creates feed deficits during parts of the year when pasture growth is lower. These can be filled with a cost-effective, high quality forage such as maize silage. Maize silage works on organic dairy farms because it is a readily available, consistently high quality feed that can be grown on-farm at a relatively low cost! 

Maize silage is a key supplementary feed that can be used by organic dairy farmers to fill the feed gaps created by higher stocking rates and variable grass production. It can be either grown on-farm or a run-off enabling the farmer to maintain absolute control of the product being fed to the herd.  Maize also provides a great sink for any excess dairy effluent coming from the shed. Many other imported supplementary feeds like molasses, PKE and grains are either not suitable for use on organic dairy farms or very expensive.

This technical insight deals with both how to successfully grow, harvest and store an organic maize for silage crop and then how to profitably feed it.

A. Growing organic maize for silage

Maize is the organic farmer’s dream crop.  It grows rapidly, it produces a lot of drymatter and equally importantly, it produces a lot of energy in the form of starch.  To ensure crop success there are a few steps which need to be followed.  These are outlined below:

1. Paddock selection

Successful establishment of a maize crop relies upon following all the recommended steps at the correct time. If possible, select your paddock in the early autumn. Walk the whole area and check for the following:

1.1     Perennial grass weeds (e.g. couch and mercer grass).

If perennial weeds (e.g. couch/twitch, mercer grass, kikuyu) are not controlled they can cause a significant reduction in maize yield.  Avoid using paddocks which have a major perennial weed problem.

1.2     Drainage.

Maize does not perform well in waterlogged soils. Water logging can also encourage weeds like willow weed to invade the crop. This can reduce maize yield and also impact on silage quality, palatability and stock health. Drain any areas where water ponds develop to allow earlier cultivation, better weed control and reduction in nutrient leaching.

2. Soil test

Soil test to determine the most suitable fertiliser and lime input.  Fertiliser requirements will vary greatly depending on the history and fertility status of the paddock. Long-term dairy pastures which have had a history of effluent application may require no fertiliser while continually cropped paddocks or run-out sheep and beef farm pastures sometimes require capital fertiliser applications. Soil core to the depth of cultivation - normally 150 mm and up to 300 mm on peat soils. Increase lime application in areas where contour correction is required especially on heavy soils and peats.

Fertiliser: Organic certified fertiliser must be used. Fortunately the two key minerals maize needs for growth (potash and nitrogen) are available organically at reasonable prices. Sources include muriate of potash (MOP), chicken litter and dairy shed effluent. 

3. Maize hybrid selection

It is important to choose the correct Pioneer® brand maize hybrid for your area. Your local Pioneer representative will have a variety of hybrids that better suit growing maize organically, contact them for regionally appropriate advice. Some important factors to consider include:

3.1    Comparative relative maturity (CRM).

This is an indication of the growing period from planting to harvest. The actual crop growing period will vary according to the amount of heat the crop receives (i.e. spring, summer and autumn temperatures) during the season. The warmer the season, the shorter the period from planting to harvest. See the Pioneer® brand maize silage catalogue for average planting and harvest dates for Pioneer hybrids in your area. Note: The comparative relative maturity of the hybrid is not the number of calendar days from planting to harvest.

3.2    High total DM and grain yield.

Hybrids must have a high total drymatter yield as well as a high grain yield to achieve maximum metabolisable energy yield per hectare. Grain yield is important as grain contains 70% more metabolisable energy and greater carbohydrate levels than stover (the green part of a maize plant).

3.3    High population adaptability.

High plant populations are necessary to ensure high silage yields. All Pioneer® brand maize hybrids have been fully tested for their adaptability to high populations and fulfil this requirement. It is important to plant as high a population as possible to maximise suppression of all developing weeds.

3.4    Drought tolerance.

If planting into paddocks with drought prone soils choose a maize hybrid with a good drought tolerance rating.

3.5    Plant shape.

Light suppression is really important to prevent weed growth.  Choose a hybrid with more prostrate rather than erect leaf shape. Your local Pioneer representative can assist you in identifying more prostrate hybrids.

4. Choose your ideal planting date

Maize loves heat! Aim to plant organic crops when the soil temperature is consistently above 14°C and day temperatures are above 18°C.  For most areas this will be late October or early November. Planting once soil temperatures are warmer will allow the maize to grow quickly so stands a better chance of outcompeting weeds.

5. Cultivate as soon as possible

Once the ideal planting date has been chosen, begin cultivating at least six weeks prior to this. The aim of the cultivation process is not only to prepare a seedbed to plant into but also to reduce the weed bank and kill harmful insects (e.g. Argentine Stem Weevil, Black Beetle and Greasy Cutworm).  You may need to cultivate the ground three or four times before planting.  Check the ground regularly and when sufficient weeds have germinated, run a spring-tine cultivator or some other similar implement over the ground. 

6. Contour and lime

If contouring is not required apply lime just after the initial cultivation. If contouring is required, undertake cultivation and apply lime when shaping is completed. Apply extra lime where drain banks or humps have been removed, especially on peat or clay soils.

7. Fertiliser

Spread and incorporate the fertiliser dressing at least a week before planting.

8. Final cultivation

If more than 24 hours have elapsed or it has rained since the last pass of the cultivator, make a further pass with a surface cultivator (e.g. rotor-tiller), before planting.  If the soil is very dry and there is still a significant number of weeds present only cultivate the soil very lightly and shallowly so that you kill the weeds but prevent too much soil moisture loss.

9. Planting

Maize hybrids for silage must be precision planted. Choose a competent contractor with well-maintained machinery who drives at the speed recommended by the drill manufacturer.

10. Insect control

Organic maize is limited when it comes to insect control. Starving them through effective cultivation and a long fallow period is the most effective means of ensuring the young maize seed is protected.

Greasy Cutworm: Greasy Cutworm moths will lay eggs in the months prior to planting. Infestations are sporadic but tend to be more common in weedy paddocks dominated by docks and chickweed. When these paddocks are planted, small caterpillars can persist through short cultivation periods. Larger caterpillars cut and consume small seedlings when the plants are 50 – 300 mm high. Later infestation does not kill the plant but may weaken the base of the stem and cause lodging.

Infestation can be avoided - Cutworm caterpillars may be damaged or starved by cultivation and removal of plant matter seven or more days prior to planting.

For information about insect control in maize crops: refer to “Plant Protection in Organic Arable and Vegetable Crops – a growers resource”, Crop and Food Research publication (2005).

11. Weed control

Post emergent weed control is best achieved by:

11.1  Pre-plant cultivation to reduce the size of the weed seed bank.

11.2  Choosing prostrate leafed maize hybrids and planting them at high populations.

11.3  Inter-row cultivating when the plants are knee high.

12. Crop checks

From about six days after planting check crop emergence. Full emergence normally occurs 7 - 14 days from planting depending on temperature. Walk the crop every second or third day checking for insect and bird damage and weeds.

12.1  Greasy Cutworm. The symptoms of Greasy Cutworm in the crop are plants that have been cut off at ground level. Greasy Cutworm is a dark coloured caterpillar that feeds at night and burrows down into the soil during the day.

12.2  Bird damage. If you find small seedling plants pulled out of the ground with the roots still attached, it is probably bird damage. Birds can be attracted to the area by seed left on the surface of the ground when the planter lifts at the end of each planter run or on tightly turned corners.  If you note seed on the ground at planting, draw your contractor's attention to the problem.  If ducks are a problem and soil temperature is 14°C or higher, adjust the planting depth to 65 mm. 

12.3  Seedling weeds. Inter-row cultivate just prior to canopy cover.

B. Harvesting and ensiling maize silage

The secret to making good silage is to ensure that it is harvested at the right time, compacted into an air tight stack and then kept air tight until it is ready to be fed out.  It is important to follow the correct procedure in order to make great maize silage.  This is:

1. Organise your contractor

Ensure you make contact with your chosen contractor earlier rather than later.  Get them involved with the whole harvesting process.  Make sure that they understand that your maize is organic maize to ensure there are no mistakes made. On an organic farm, outside contractors are required to have cleaned their equipment before entering the property. Giving your contractor plenty of notice of your job will allow them to plan your work after a normal clean down procedure. A standard “contractor” form needs to be completed each time a contractor brings equipment onto the property to confirm their machinery was cleaned - your organic certifier can provide you with a template. 

2. Choose the site of your stack

Many farms already have a bunker available to use. When building a new bunker or stack choose the site well.  It needs to be on free draining ground, close to where the maize is going to be fed.  It also needs to be a reasonable distance from walls, fences, drain banks etc. to ensure stack tractors can run off the stack when rolling.

3. Timing of harvest

The ideal time to harvest your maize for 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. 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. Call Pioneer toll-free on 0800 PIONEER (746 633).

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. 

4. 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:

4.1 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.

4.2 Break / snap the cob in half and discard the end of the cob that was attached to the plant.

4.3 Hold the point of the cob downwards and remove a kernel from the "snapped" end.

4.4 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.

4.5 Note the point where the solid starch ends and the liquid milk begins. The hybrid will be ready for harvest when the milk line is two thirds of the way down the kernel (see Fig 1).

4.6 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 lab (see the next two points).

5. Plant moisture content

The moisture content in the plant (leaves and stem) can vary considerably. This is especially evident immediately after an extended dry period following rain. Plants re-hydrate and can hold significant amounts of moisture in the period immediately after a rain event ends a dry period.

To check the content of moisture in the maize stalk, grasp the stalk at the inter-node below the cob and pull the top of the maize plant over so as to fracture the stalk.

Lift the top part of the stalk back to the upright position and twist the top portion of the stem noting the amount of fluid evident where the stalk is fractured. If there is only a small amount of moisture showing between the stem fractures then the milk line drymatter percentage guide will hold true. But if there is a significant amount of fluid and it runs down the stem, downward drymatter percentage adjustment will need to be made.

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 indication on the kernels.

6. Microwave drymatter test

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

7. 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, and often considerably longer, for your samples to be processed. Remember that the result of a drymatter test will only be accurate if a good representative sample is submitted.

8. Communicate with your contractor

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, tape and tyres) that will be required if these are not supplied by the contractor.

9. 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.

10. Processor settings

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

11. Inoculant

Pioneer® brand maize silage inoculants have not been registered for use on organic maize silage.  However, maize silage with its high starch content can still be well ensiled, if it has been harvested well, compacted well and kept air tight.

12. Compaction equipment

Good compaction is the key to making top quality silage. Take into account the rate at which the silage is being harvested when planning machinery requirements for compaction. Compaction is a function of vehicle weight, rolling time, and depth of spread of harvested material. Remember that wheeled vehicles have a higher weight per surface area and achieve better compaction than tracked vehicles of an equal size. If a small tractor that you plan to use has duals, remove the outside wheels, increase the tyre pressures and attach weights.

13. Silage covers

Use a new, high quality plastic cover. Make sure that you have silage tape that is compatible with the cover.

14. Spreading loads

Fill the bunker or stack as quickly as possible to minimise exposure to the air. Where possible, fill in a wedge shape (Fig 2). This will give good compaction and minimise the amount of time that the maize silage is exposed to the air. Spread each load into a 100-150 mm layer so that it can be compacted properly. If large loads are being delivered to a stack site, dump the loads in front of the stack. Build the stack by taking small loads to the stack layering as you go to achieve the desired shaping.

Figure 2: Filling in a wedge shape


15. Seal the stack

After the last load has been delivered continue compacting until the surface of the stack or bunker is firm.  Cover the stack with a high quality cover, place tyres on top so they touch and seal around the base of the stack with sand, dirt or lime.

Silage covers: In organic farm systems it is encouraged to give consideration to the recycling of silage covers.

C. Feeding maize silage profitably

The principles behind feeding maize profitably are exactly the same for organic dairy systems as they are for non-organic dairy systems. Creating feed deficits by increasing stocking rate or by altering calving and drying off dates and then filling the feed deficit with a low cost, high value supplement like maize silage is highly profitable.

1. Increase pasture harvest

New Zealand dairying is based on turning grass into milk. Supplements are most profitably used when they enable the farmer to increase pasture harvest.  Maize silage enables the farmer to confidently carry enough cows to maximize pasture harvest. 

When maize silage is combined with a stand-off pad with feeding facilities, the system becomes even more robust.  Stand-off pads drastically reduce wastage of feed, reduce pugging (and therefore increase pasture grown) by enabling cows to be kept off pasture when the soil is wet, and give the farmer control of how the animals are fed during their non-milking period.  

2. More days in milk

Turning a non-milking day into a milking day has always been a profitable use of feed.  In an all-grass system, farmers are totally reliant on what the weather brings as far as rainfall and sunshine and therefore feed is concerned.  Having a stack of maize silage on hand provides an important buffer in an organic system and means that instead of drying cows off, cows are able to be fed and milked. A milking cow is a lot more efficient and therefore more profitable than a non-milking cow. 

3. Maize silage is a great cow conditioner

Maize silage is the most efficient home grown feed available to organic dairy farmers for putting on cow condition.  This means farmers can milk for longer at the end of lactation with maize silage than on an all-grass system as they will need less time to get cows back into condition score 5.0 at calving.

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Revised: June 2015
Expires: June 2018