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Case Studies - Cropping

Why lime is important for fodder and maize crops

Product Sector: Agriculture - Cropping

Product: AgLime

Source: Paddy Shannon, M.Ag.Sc.(Hons). 

Low pH = low yield. Correcting low pH conditions can lead to large yield increases – often in the order of 20 to 50%. Preparing for this summers’ maize and fodder crops means starting to plan now.

Preparation

  • An important part of the process is to make sure that the soil in the cropping paddocks is set up to give you the best possible yield that the climate will allow.
  • Good preparation can help to offset the effects of cooler or drier than optimum conditions.
  • A vital and often overlooked part of your preparation is to make sure that soil pH levels are where they ought to be.
  • If you are taking the worst performing paddock and using the cropping process to prepare it to support high-yielding pasture after the crop, then you should realise the crop needs good soil conditions as well.
  • Plan to have the soil in good order before you sow the crop. This way you can “write off” the costs of soil improvement for the new pasture against the cropping process - $500/ha spent on fertiliser and additional lime against a 20-tonne maize crop represents 2.5c/kg DM.


What you should be looking for?

Maize Crops

  • Maize has to have a soil pH over 5.5 (using a 15cm deep sample).
  • Many guides suggest a pH of 6.0 should be used because the crop will tend to acidify the soil when it takes up nutrients as it grows.
  • Most maize is not fed out on the paddock it is grown in, so the acidity will remain. If pH levels are low, liming to above the minimum level can give yield increases of over 15%.
  • Also, if you get pH above 6.0, you will only need to apply maintenance lime to your pastures.

Summer Brassicas

  • For summer brassica crops such as turnips (leaf or bulb), rape and kale, the target pH is 6.0.
  • With proper soil fertility management (including nitrogen use) these summer crops can easily yield over 10 tonnes of DM/ha, so an expenditure of $500/ha on soil fertility comes to only 5c/kg DM.
  • If you leave out liming and only spend $450/ha but lose 30% of the yield, the soil fertility cost rises to 6.4cents/kg DM.

What should you be doing now?

  • Identify the areas you are going to put into crop.
  • Soil test them all – even areas doing a second round, because high yielding crops can make big demands on soil resources and pH can change even after one such crop – using a 15cm probe.
  • Once you have the results, work with your contractor and consultant to identify the soil fertility needs.
  • If lime is required, make sure that it goes on early in the crop preparation process so that by the time your new crops are getting established, they are in soil that is in the best possible condition to give you the optimum yield.