Maize for Silage
Insight 350


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Home grown crops have become an increasingly important part of milk production in New Zealand. Many factors must be considered when determining the best crop option. This Technical Insight compares two crops, maize silage and fodder beet.

Maize Silage

Maize silage is a well-researched, farmer proven feed which over many years has allowed high profit and environmentally sustainable farm systems to become the norm across New Zealand.

Maize silage – strengths and considerations

The following table summarises some of the key strengths and considerations of maize silage.


Maize silage is proven: There has been more worldwide research into growing, harvesting, storing and feeding maize for silage than there has been for any other crop or supplement. In NZ maize has been tested in most environments and been researched in a wide range of farm systems. The industry has learned over decades how to grow, harvest, store and feed maize well.

Maize silage allows farmers to harvest more pasture: Maize silage systems allow farmers to lift stocking rates and maximise pasture harvested. With a stack of maize silage on hand to fill feed deficits, farmers can confidently milk more cows per hectare, increasing grazing pressure and production per cow and per hectare.

High total annual drymatter yields: A replicated, two-year forage production trial conducted in the Waikato showed maize silage followed by a winter crop could produce an annual drymatter yield of over 38 tDM/ha (Densley et al. 2006). Maize yields of 18 – 24 tDM/ha are achievable in most districts with top crops yielding over 30 tDM/ha and a number of trials yielding over 40 tDM/ha.

Environmentally sustainable: Growing maize allows it to capture nutrients that have dropped out of the root zone of shallow rooted pasture species. Feeding maize dilutes dietary protein, and reduces nitrogen excretion by the cow (Grignani 2007).It also allows farmers to stand animals off paddocks when soil conditions could result in pasture damage.

Yield stability: Modern maize hybrids have excellent yield stability, allowing them to produce consistently high yields even under challenging growing conditions.

Feed buffer: Having a stack of maize silage on hand allows dairy farmers to weatherproof their feed supply giving stable production, improved reproduction, and greater peace of mind.

Reduce on-farm nutrient build up: Increased stocking rates and more bought-in supplements contribute to an increase in soil nutrient levels. This has been implicated in a rising incidence of milk fever and grass staggers on some farms. Growing maize reduces soil potassium levels, while feeding maize silage (a low potassium feed) reduces the risk of milk fever caused by cows grazing high potassium pastures.

Safe to feed: Since maize silage contains a mix of carbohydrates and fibre, maize silage is safe to feed. In fact, overseas research has shown that as long as it is introduced slowly, cattle can eat more than 90% of their diet as maize silage (note that feeding rates will be influenced by cow nutritional requirements and the type and amount of other feeds in the ration).

Consistent quality: Maize silage has a consistent high quality when compared to other

New Zealand silages.

Option to double-crop. Careful maize silage hybrid selection allows farmers in most areas to fit maize into a re-grassing programme with perennial ryegrass established after maize silage harvest in March/April. Alternatively a winter crop such as triticale, oats or annual ryegrass can be planted after maize silage giving an additional DM yield of 4-6 t/ha.



Can’t be grown in cold climates: Maize can’t be grown in colder climates where there is a risk of frost late in spring or before harvest time.

Has low crude protein (CP) levels: Maize silage needs to be fed with other feeds higher in CP, e.g. leafy pasture.

May need mineral supplementation: When dairy cows consume maize silage, deficiencies in the macro-minerals Ca, Mg, Na and P become more likely. Supplementation with these minerals is easy and a relatively inexpensive insurance against possible deficiencies.

Need for some capital investment: in order to use maize silage successfully some equipment is needed (e.g. tractor, wagon, storage facilities).


Fodder Beet

Whilst having been grown in New Zealand for many years, fodder beet has recently gained popularity as part of dairy cow winter feeding systems in some areas.

Fodder beet - strengths and considerations

The following table summarises some of the key strengths and considerations of fodder beet.


High drymatter yield: Yields of 18 - 22 tDM/ha are typical for well managed crops although yields of up to 30 tDM/ha are possible under good growing conditions, (DairyNZ farmfacts 1 - 77). Mean yield of 13 fodder beet cultivars at four sites in the South Island was 17.2 tDM/ha (Milne et al 2014, Proc. NZGA).

High feed value: Fodder beet is high in energy (ME 11.8 - 12.5) and sugar (50-70%DM) (DairyNZ farmfacts 1-73).

Can be grown in colder climate: Fodder beet has a wide area of adaptation.

Reduces N excretion: Feeding fodder beet (9 - 14% CP) dilutes dietary protein and reduces nitrogen excretion by the cow.



Yields vary depending on attention to detail, soil type, fertility, weed competition and available moisture, (DairyNZ farmfacts 1 - 77).

Risk of acidosis: To avoid nutritional disorders it is essential to transition cows onto the crop correctly. Slowly introduce the cows to fodder beet by decreasing the proportion of pasture/silage and increasing the amount of fodder beet in the diet over a 14-21 day period, (DairyNZ Trial work has shown that the herd should not be offered more than 70% of their diet as fodder beet. The remainder of the diet should be a long fibre source, such as silage, hay, or straw, and the cows should be fed this before their beet (Caution urged over fodder beet intake, DairyNZ June 2015).

Potential for environmental damage: Care needs to be taken to select paddocks less susceptible to pugging damage and to minimise run-off, (DairyNZ farmfacts 1 - 77). The N leaching risk from grazed winter forage crops can be large, making a disproportionately large contribution to annual N leaching despite representing a relatively small area of the farming system (Shepherd 2017)

Sensitive to moisture deficit: Fodder beet is sensitive to moisture deficit in early stages of establishment, (DairyNZ farmfacts 1 - 77).

Sensitive to residual chemicals: It is important when choosing the paddock to ensure that there has been no recent history of chemical use as fodder beet is very sensitive to residual chemicals. (Agricom fact sheet)

Must never be grown twice in the same paddock as bulb chips from the first crop may regrow and produce seed in the second year’s crop and create a bank of hard seed with sporadic germination for up to 20 years, (DairyNZ farmfacts 1 - 77). Beet can get several root-rot diseases and nematodes that cannot be controlled with chemicals, (DLF Trifolium- Fodder beet use in Europe).



Maize silage

Average maize silage growing and harvesting costs are $3,780/ha in an average fertility paddock and $2,935 in a high fertility paddock*. Assumes 6% storage losses and 10% feed-out losses. The cost per kilogram of drymatter eaten is shown in the following table. 

Maize silage cost (in the stack, available for feeding year round)

Maize silage yield (tDM/ha)









Maize silage high fertility paddock (c/kgDM eaten)









Maize silage low fertility paddock (c/kgDM eaten)









*For full detail growing, harvesting & stacking costs see the Pioneer® brand Maize for Silage Catalogue 2017/2018 or   (High fertility environments include dairy paddocks coming out of long-term ryegrass-clover pasture, as well as paddocks with a history of effluent application. Average fertility environments include run-out pasture paddocks and repeat cropping blocks. Always soil test maize paddocks and apply nutrients according to the results).

Fodder beet

Grazed crops: It is estimated that it costs $2,250/ha to grow a fodder beet crop. An utilisation of 90% is assumed for in situ grazing (DairyNZ farmfacts 1 - 77).

Lifted and stored crops: It is estimated that it costs $2,250/ha to grow a fodder beet crop and $1,300/ha to lift, transport and store fodder beets**; tops (approximately 17% of the DM yield) are left behind**, 5% storage losses and 5% feed-out losses. The cost per kilogram of drymatter eaten is shown in the table below.

Fodder beet cost (grazed in situ or lifted & stored)   

Fodder beet (tDM/ha) 









Fodder beet grazed (c/kgDM eaten)









fodder beet lifted & stored (c/kgDM eaten)









**Matthews 2011, Agronomy New Zealand 41, 2011 p.39 and other industry information

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Revised: August 2017
Expires: August 2018