The winter feed dilemma

Crop or grass?

By Mark Everest, Farm Management Consultant at Macfarlane Rural Business Ltd (MRB)

Winter forage crops are becoming increasing popular for wintering livestock, being cost effective, secure from weather adversity and for restricting pasture damage from grazing over the wetter months. But are they better than grass? Typically of biological systems, the answer depends on various factors – however, my modelling suggests that fodder crops are more secure and consistent and possibly more environmentally favourable.

Soil structure

Winter forage crop impacts on soil and environment have been well researched, with common conclusions: it degrades soil structure and organic matter, reduces porosity and increases the risk of nutrient leaching or runoff after grazing. It is also well established that many of these risks and impacts can be mitigated or remediated through careful planning, species selection and precise management.

Less discussed is that all-grass wintering causes the same damage to pasture paddocks, requiring remediating or re-sowing in spring. The total feed offered per hectare on an all-grass wintering system is approximately 12tDM/ha, feed offered per hectare for wintering is approximately 16tDM/ha, and fodder beet approximately 33tDM/ha.

Modelling the comparison

Using FARMAX and OverseerFM, we compared the Economic Farm Surplus (EFS), biological feasibility, and likely environmental impacts of all-grass or fodder crop based dairy support programmes for an 850 cow dairy farm wintering 875 cows and R2 heifers and grazing 200 R1 and R2 replacements.

The fodder crop based farm rotated fodder beet, kale, silage oats (as a catch crop) and barley for grain. No supplement was bought in. It used a total synthetic nitrogen of 103kg/ha. The all-grass farm assumed that 30–70% of the farm would be damaged in winter and need annual re-grassing. This farm couldn’t grow enough feed so imported 296–356tDM of silage and straw and used a total synthetic nitrogen of 122–127kg/ha.

Profitability

Both model farms carried the same number of animals for the same time, but the costs of baling, wrapping and feeding conserved pasture and straw were much higher for the grass-based system.

The fodder crop farm’s EFS of $1452/ha was far higher than the grass-based equivalent’s $218/ha, caused directly by the grass-based farm bringing in feed. Grazing stock off farm is only marginally more economical as the winter diet proportion of baleage and straw – expensive feeds – is so large.

Environment

Before electing to all-grass winter, remember that leaching from livestock is largely caused by urine deposition, which is worse on ground where no forage is growing. So if stock destroy all or almost all growing grass while grazing, the risk of leaching is more comparable to a fodder crop paddock than a pasture paddock due to the lack of a growing plant to utilise the nitrogen from urine deposition.

Despite both farms being modelled as best practice, the grass-based farm indicates a simple N surplus of 146kgN/ha/year, a risk of leaching 34kgN/ha/year and emission of 9.47t/ha/year CO2-e. In comparison, the fodder crop based farm’s simple N surplus was 81kgN/ha/year, risk of leaching 33kgN/ha/year and emission 8.55t/ha/year CO2-e. The higher N surplus of the grass-based farm is mostly because a large amount of feed is bought in, with no grain sold off.

Nitrogen concentration in water has received heightened attention recently, and while the forage crop farm models indicated higher concentrations of nitrate in drainage from the forages, the farm averages calculated to be 13.1ppm and 13.0ppm nitrate nitrogen in drainage for the forage crop and grass-based farms respectively.

How to decide

In deciding which wintering system to implement, consider all direct and potential impacts, including consenting. While grass-based wintering does not trigger the need for an intensive winter grazing consent, feeding large amounts of supplement to livestock in a way that prevents pasture from persisting is likely to trigger the need for a feed pad consent.

Also consider future asset value. As investors gravitate towards buying land based on its earnings potential, and with limited ability to change land use, choose the right system for your block of land and farm business.

Through integrated evaluation of major farm system change, we are able to consider possible unintended consequences and the longer term impacts of your decision.

In conclusion

Many of the potential environmental risks associated with either option can now be mitigated or managed. So I see little reason to consider all-grass wintering as a viable alternative, given the additional climate-feed risks, greater greenhouse gas obligations and reduced economic viability. When managed properly, forage crops bring many benefits to a production system and the environment.

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