To crop or not to crop?

MEDIA RELEASE
Thursday, 24 September 2009

For immediate release

To crop or not to crop?

Recent modelling work completed under a joint project by DairyNZ and AgResearch suggests that the economics of growing summer crops is highly dependent on yield and the value placed on pasture renewal.

“The break-even yields for maize and turnips at a $5.10 payout are 23tDM/ha and 11tDM/ha respectively,” says DairyNZ Productivity Team Leader Rob Brazendale. “Yields below these break-even points will be uneconomic unless the crop is being grown for reasons other than providing a cost-effective source of additional feed.”

Three years of trial results carried out on the DairyNZ Super Productivity farm yielded an average of 20.5tDM/ha plus 5 tonnes DM/ha from annual ryegrasses. Research findings under the “More Summer Milk Project” in the 1990s also found that the range in turnip yields was 6.5t-11.0M/ha. Hence, the break-even yields above are challenging.

“The reason the break-even yields are so high is that there is an opportunity cost in the form of pasture not grown while the paddock is in crop,” says Rob. “It is the net gain in yield between pasture and crop that has value in the whole farm system. Seasons when you grow great crops also grow more pasture.

“Reasons other than providing additional feed include pasture renewal or re-contouring a paddock. Cropping can be an effective method for establishing new pastures as it provides a weed break and can improve the introduction of novel endophyte. If the crop paddock is due for pasture renewal and this cost will be incurred, regardleῳs of whether it is cropped or not, then the breakeven yields are reduced to 20t/ha for maize and 10t/ha for turnips.

This analysis assumes that maize is grown in effluent paddocks or out of fertile pasture and hence requires no additional fertiliser inputs. It also assumes that there is a genuine feed surplus at the time of spraying out the paddock and hence the integration of a crop does not penalise spring or summer production.

“Successful cropping also requires expertise and good timing,” says Rob. “If you are dependent on contractors good communication is critical. A one day delay is estimated to reduce maize yields by 1 per cent of final yield. Ten days equals a 10 per cent loss of yield, which is often the difference between a profitable or non-profiῴable crop.

To view further detail on yield and break-even points from the joint DairyNZ AgResearch project or DairyNZ Farmfacts on crop growing visit the Tight Management pages of the DairyNZ website: www.dairynz.co.nz/tightmanagement

The Forage Brassica Development Group’s (FBDG) ‘Management practices for forage brassicas’ booklet is complimentary to those who have attended workshops or field days over the past three year of the FBDG project and also paid the $30 fee. Additional copies of the booklet may be purchased via Plant and Food Research for $20 including GST. Farmers can post requests to ῌorraine MῡcKenzie, C/- Plant and Food Research, Priῶate Bag 4704, Christchurch 8140.

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