- Feed Is In Very Short Supply but Finance Is Very Limited or Non-Existent
- Finance Is Very Limited But Feed Supply Is Expected To Be Adequate For Present Stock Numbers
- Shortage Of Feed Is Over-Riding Problem-Some Finance Available For Fertiliser Expenditure
Fertiliser Management in a Drought
Like all farm expenditure, fertiliser use must come under close scrutiny when drought reduces farm income. The following information may be of some help.
First, decide which of the following categories best describes your situation.
Feed Is In Very Short Supply but Finance Is Very Limited or Non-Existent
If you are in this category, you may have little option but to withhold fertiliser completely for one year. Feed should be brought in or stock sold according to the current situation.
What will be the effects of withholding fertiliser?
In a normal situation, withholding fertiliser completely will reduce pasture production under average rainfall by up to 4% in the first year and a further 12% in the second year if the fertiliser programme has been kept up to date in the past.
However, the drop in normal production following a drought will be less than this, simply because the lower pasture production during the drought will not have used all the previous fertiliser application. If present soil phosphate levels are above 15, there will be no significant drop in production in the first year without fertiliser. Even when soil tests are lower than this, pasture production is not likely to be more than 10% down without fertiliser.
It is also worth remembering that any hay and grain used will return nutrients to the soil in excreta. For example, every 100 small bales of good quality hay consumed returns as much available phosphate to the soil as that contained in 200 kg of superphosphate.
Finally, if stock numbers have been reduced during the drought, there will actually be a lower feed requirement in the following period than normal.
So, do not despair if you cannot afford fertiliser this year. Think of it as skipping a meal-it is only when you make a habit of it that you are likely to suffer. When conditions improve and you can afford fertiliser, make sure you apply sulphur as well as phosphate (eg superphosphate or a mixture of DAP and sulphate of ammonia) as most soils are just as dependent on sulphur as phosphate. Use soil tests and your adviser's knowledge in deciding on the correct application.
Finance Is Very Limited But Feed Supply Is Expected To Be Adequate For Present Stock Numbers
Farms in this second category should aim just to maintain present soil fertility levels. Because pasture production during a drought may be down by 50% on light soils and 25% on deeper soils, normal fertiliser applications can be reduced by this amount in the next year. Remember the law of diminishing returns-the biggest response is from the first few kilograms of fertiliser.
Shortage Of Feed Is Over-Riding Problem-Some Finance Available For Fertiliser Expenditure
If you are in this category, try to at least maintain present phosphate and sulphur inputs, and increase them if soil tests are low. Use nitrogen at about 30-60 kg N/ha in the early spring in the form of urea if soil tests are okay, or a Cropmaster fertiliser of phosphate, sulphur and potassium. Generally, you should topdress the best paddocks first, as they will give the best response per kilogram of fertiliser.
John Armitage
Agricultural Consultant
Agriculture New Zealand
Ashburton
Contact for Enquiries
Manager
North Island Regions
Sector Performance Policy
MAF Policy
Hamilton
NEW ZEALAND
Phone: +64 7 957 8313
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