Maize performed very poorly in 2012 and 2011, leaving many growers short of fodder. However, initial indications suggest that the maize area will not collapse and that farmers are planning to drill a similar area to last year (13,400ha in 2012). The general lack of fodder is forcing farmers to re-consider maize and ask how to get the most from the crop.

Economics

Maize is an expensive crop to produce. Input and contractor costs of €1,600 per hectare (including plastic mulch) are common. These costs must be diluted by high yields with high total dry matter (DM) present in the cob.

The economic attractiveness of maize depends on the same criteria as for grass silage: high yields, high nutritional value, and minimal storage and feed-out losses.

Analysis at Grange has quantified the effects of weather related yield fluctuations on the feed cost of maize. This looked at year-to-year weather-related yield fluctuations from the Department of Agriculture (DAFM) variety trials over a 10-year period. Maize silage was cheaper than whole-crop and grass silages on average, but was the most costly and least costly harvested feed crop in low and high yielding years respectively. Dramatic yield variability made maize silage cost (without plastic) three times that of spring barley and twice that of a two-cut grass silage system.

The total feed costs per 1,000 UFL can be directly compared with the /t price of rolled barley, as 1,000 UFL is the net energy present in one tonne of dry barley. The Grange Feed Costs project shows the economic advantage of an integrated grazing/grass silage system over any other harvested feed crop (Table 1). However, there are certain scenarios in which high yielding, high starch maize silage can provide considerable savings:

Where silage area cannot be efficiently grazed, due to fragmentation or access issues.

Where desired animal performance during housing cannot be achieved from grass silage alone.

Where profitable output can be increased, or more costly purchased feeds replaced by growing maize.

Benefits of plastic

Irish research has shown that the use of plastic increases maize DM yield by about 3.0 t/ha (range 1 to 5 t/ha) and will increase starch and ensure the crop reaches maturity. This research was developed into a reliable, usable technology by Samco and is now used widely in Ireland and many other countries. The cost of plastic is about €300+/ha. Maize varieties are very specific and need careful selection and agronomy to get the best response from plastic.

Predicting crop yields

The data in Figure 1 is taken from the Department’s (DAFM) Maize Recommended List Trials 2002-2012 and represents the performance of the control varieties assessed for each year.

Note: While it is not technically correct to compare these plastic and open crops, as each trial was grown and assessed separately, the results give a good indication of the potential performance of the different systems.

Recent research in Northern Ireland by Trevor Gilliland at AFBI found a good relationship between early season temperatures and dry matter yields. Trevor found that open sown maize correlated better with the average of mean monthly temperatures: (May + (twice in June) + July).

In contrast, the faster developing plastic covered maize correlated best with mean June temperature alone. This is not a perfect model and further research is on-going. But it does help assess maize crops and make appropriate fodder decisions.

Figure 2 shows the value of plastic to help reduce maize yield variability (and, consequently, cost variability). The real value of the plastic can be seen in the very poor weather year; where due to yield and maturity gains, maize sown under plastic is 20% cheaper than the non-plastic crop.

Overall, year-to-year cost variability of non-plastic maize was twice that of maize sown under plastic. The data in Figure 2 is based on the average harvested DM yields reported from 10 multi-year Irish studies.

The cost includes a €300/ha land charge. Contractor charges were used for all operations and storage and feed-out losses are included. Mean yields were 15.5 tDM/ha (plastic) and 13 tDM/ha (no plastic). 1,000 UFL is the net energy for milk production in 1t of dry barley.

Crop nutrition

Fertilizer costs for maize are very high (€514/ha — Teagasc figures for 2013), so it is critical that each field should have a recent (less than three years old) soil test before drilling the crop.

Maize is very sensitive to pH and lime makes phosphorous more available to crop roots. The ideal pH for maize is 6.8 to 7.0 but it will grow successfully down to 6.3.

A mistake in crop nutrition is impossible to rectify once the crop is drilled – early season growth is critical. Trace elements, particularly zinc and manganese, can successfully be applied as foliar sprays at the six to eight-leaf stage.

An application of 57,000 litres/ha (5000 gallons/acre) of cattle slurry (covered tank) should deliver all the crop’s P and K requirements (Table 2). But the P in slurry may not be fully available to the growing crop if the soil test reads very low for P (another reason to have a soil test). The nitrogen value in slurry is dependant on the weather post spreading and the time from spreading to ploughing.

All bag fertilizer should be broadcast pre-sowing, with some N and P placed at sowing, e.g. a specific maize starter or 10-10-20. This is most important in open-sown crops as the warmer soil under plastic improves P availability.

Seedbeds and drilling

Drilling can proceed when soil temperatures are above 8ºC (can be 6ºC in plastic crops). Seedbed preparation is vital for an even crop and to good weed control. Recent French research showed that an uneven crop does not yield as well as an even crop due to competition effects between neighbouring plants.

Maize needs a fine, firm seedbed 10cm to 12cm deep, similar to that for beet crops. Residual herbicides (e.g. Stomp, Calaris, etc) work best when applied onto fine, moist seedbeds.

Imagine residual herbicides as being like a plastic sheet covering the ground and preventing weeds from germinating. Clods are like holes in that plastic sheet, allowing weeds to germinate under them. A fine seedbed is also useful to reduce slug attack.

Variety Selection

Maize variety information is available from the DAFM Forage Maize Recommended Lists 2013. This shows yield and feeding quality for each variety, as well as other important characteristics such as standing ability, spring vigour and suitability for growing under plastic.

Growers should give preference to the varieties listed (in the DAFM Maize 2013 list) unless there is compelling evidence that other varieties are more suited to their specific conditions or requirements.

Pests

Use a fertilizer bag/slate/bucket lid with some breakfast muesli to check for slug activity. Caution: the level of slug attack in winter cereals was very high in autumn 2012 (as well as isolated severe leather-jacket attacks) so monitor crops from drilling to the four-leaf stage. Apply slug pellets or chlorpyrifos, as appropriate. Crops under plastic tend not to suffer greatly from slugs/leather-jackets but they can be affected if numbers are high.

Wireworm can only be controlled using Pancho-dressed seed. This must be ordered in advance and costs approximately €20/ha extra. Wireworms are most problematic in the second and third years after ploughing extensively managed leys.

Weed Control

Maize needs 30 to 50 days free of weed competition after sowing to avoid a weed penalty (up to 50% yield loss in Teagasc trials). Maize suffers more than other crops from weed competition and it has been shown that weed roots have a large negative effect on the growth of maize roots, reducing nutrient uptake and crop growth.

Teagasc research showed that weeds should be removed as soon as possible after drilling to maximise crop growth. This is especially important where rapidly growing annual weeds, such as Charlock, Poppy etc, dominate. A delay of two weeks can significantly reduce the crop’s potential. Perennial weeds (docks, scutch, etc.) should be controlled using glyphosate pre-drilling to lower the overall weed burden.

Sowing under plastic

In Teagasc trials, weed control between the rows of plastic was more difficult than beneath the plastic. This is thought to be due to the ridge of soil used to weigh down the plastic sheet being more ‘cloddy’, prone to rapid drying and slumping compared to the fine, moist soil under the plastic. A follow-up spray of an appropriate post-emergence product (Table 4) may be necessary if weeds come through.

The most popular combination under plastic is full rate pendimethalin (various brands) and Calaris (1.5 l/ha) at sowing. Excellent sprayer hygiene is needed to ensure maximum efficiency of these herbicide mixes.

Open Crops

The main choice for use post-emergence (Table 4) will be Calaris (applied at the four to six-leaf stage) at 1.0 - 1.5 l/ha, depending on the weed pressure. Pre-emergence options (as used with crops under plastic) are less popular but these worked very well in Teagasc trials.

Difficult weeds such as thistle, scutch, wild oats and volunteer potatoes will need specialist follow-up herbicides such as Accent, clopyralid, Titus or fluroxypyr for effective control.

KEY POINTS

Yield variability in maize can make it a good or poor value feed, as bad years decrease yield and quality thus increasing the cost per tonne utilised.

Control of yield variability through choice of field, appropriate fertilization, planting under plastic and early weed control are critical to help secure high yield potential in maize.

The yield benefit from sowing under plastic has ranged from zero to 8.5 t/ha in the past decade but the associated improvement in starch content ranged from 1.1% to 10.9%, thus adding to the animal performance.

Weed control needs to be completed early to avoid early competition for the maize plants.