There are many different aspects that must be considered in crop production and these should realistically change over time to help meet the evolving requirements of soils and farmers. In this regard it is always interesting to see what is happening in other countries and in this article Elin Arnaudin from New Zealand writes about forage crop production in that country.

In comparison with Ireland, New Zealand farming systems tend to be highly diversified and integrated. For example, a predominantly arable farm might also carry sheep or beef cattle, or a dairy farm might own a support block where fodder crops are grown. Many farms grow pasture and crops in rotation, utilising the benefits of both.

Annual crops are also used as part of a pasture renewal programme to help break pest and disease cycles and to produce a high value/high dry matter (DM) yielding crop with little or no fertiliser inputs required.

In trials conducted by the Foundation for Arable Research (FAR), forage maize following long-term pasture yielded 25t DM/ha with no added fertiliser (maize yields are generally 18-26t DM/ha in NZ). In this same trial there were no yield benefits in plots which received fertiliser application.

Short-season forage crops are also utilised on arable farms. This is most common when following an early harvested crop, such as cereal silage or winter barley. The forage crop helps to avoid winter fallow and it also provides feed when pasture production is insufficient. Forage crops on arable farms are either utilised by owned stock or stock is brought in by another farmer who pays the arable farmer on a $/head/week or $/kg DM basis.

Summer-sown crops in the rotation

At this time in the season, a forage brassica, forage cereal or annual ryegrass would be common options for a fast-growing crop with good yield potential. Individual crop options range in their suitability for multiple grazing, their ideal grazing date and site suitability (Table 1). Because they are so diverse in terms of when they can be sown and harvested, they offer flexibility in a rotation. Local seed providers are the best source of information about cultivars, as there is a wide range in maturity, yield potential, and site suitability within each species.

Grazed crops

Some crops offer the potential to be grazed in summer/autumn and followed by a late autumn-sown crop or pasture re-establishment. In New Zealand, low summer rainfall often creates a feed shortage in late summer/early autumn, so having a crop for grazing at this time can be an affordable alternative to feeding supplements and allows pasture to recover.

These crops can be grown as a single crop or in mixtures. As a mix, a brassica sown with another species (ie annual ryegrass or a cereal) can be grazed hard in summer/autumn and still provide regrowth from the ryegrass/cereal to be grazed again in the spring. Winter grazing of crops is very common in New Zealand but wet soil conditions in many regions of Ireland could prevent this from being a viable option.

Conserved forage and green manures

Where a forage crop is not grazed before winter, annual ryegrass or cereals can be utilised in spring and followed with a spring crop like maize or fodder beet, or pasture can be re-established. Oats are the most commonly grown forage cereal for this purpose, but triticale or rye will give comparable yields.

In New Zealand, oats and annual ryegrass provide a good option for green-chop silage rather than grazing, though early spring grazing is also a possibility. If there is no rush to sow a spring crop, cereals can be grazed in early spring and then regrown for a whole-crop silage or grain harvest. Alternatively, farmers may grow oats through the winter and plough them in as a green manure before spring sowing.

Summer-sown crop management

Well-drained paddocks should be selected if sowing forage brassicas, but oats and annual ryegrass are more tolerant to wet soil conditions. Soil conditions at the intended grazing or silage harvest should also be considered, as wet soils are easily damaged. Any of the options mentioned above can be direct-drilled after spraying off permanent pasture, or sown into a prepared seed bed.

Soil testing, including a mineral-N test, will help determine fertiliser requirements. However, on well managed land in New Zealand soil nutrient levels following permanent pasture are likely to be adequate to supply the crop.

Treated seed will help control insect pests and diseases during establishment, but further insect control may be required in the brassicas. Fungicide sprays are not generally applied to these crops in New Zealand because there is little or no yield benefit over the short crop duration. There are also limitations due to individual withholding period requirements for individual chemicals on fodder crops.

Weed control, both pre- and post-emergence, is essential to ensure good establishment in New Zealand, while post-emergence-only is common in Ireland. If grazed, utilisation is best if strip grazing is used with cattle, though sheep can achieve good utilisation with set stocking. Where multiple grazings are targeted, ensure that there is adequate foliage left for regrowth, which may be best achieved with the use of back fencing.

Value of summer-sown crops

The short season crops above are inexpensive to grow in New Zealand, with few input costs used. It is important to consider the overall crop rotation being used and the total package of services that a crop can offer to the farm, rather than just its gross margin. This might include utilising nutrients from grazing or effluent, and breaking pest and disease cycles.

Relatively high production over a short time also adds value to the crop, especially if looking at total production and profitability per hectare over a 12- to 18-month period.

* Elin Arnaudin is research manager for the annual forage crops research programme (cereal silage, fodder beet, forage brassicas, occasionally beans/peas/annual legumes) in the Foundation for Arable Research (FAR), which is based in Christchurch, New Zealand. She conducts trials on the husbandry of forage crops to see how management impacts on yield and feed quality. She also works on rotations with forage crops to maximise production and profitability, as well as work to help mitigate nutrient losses. Elin is currently in Ireland as a visiting researcher with Teagasc.

FAR is a levy-funded organisation for the arable sector with obligatory funds collected from all combinable crop and maize/cereal silage producers.