Using nitrogen to best effect in spring-sown crops

Using nitrogen to best effect in spring-sown crops

1 October 2016

If you’re growing crops for late summer feed, include nitrogen (N) on your fertiliser order and follow these four tips to get the best return from your investment.

  1. Do your groundwork
  2. Testing your soil beforehand is important, says Ballance Science Extension Officer, Aimee Robinson.

    “Ensuring your soil pH is right and other nutrients are at optimum levels will stop these factors from limiting the potential of any nitrogen you apply,” says Aimee. Use soil test information to prepare the field for your chosen crop. Remember it takes six months to a year to adjust pH, so if yours isn’t in the ideal range you’ll need to take this into account when calculating potential yield.

    Pay attention to available N test results. “This tells you how much nitrogen your soil will supply during the crop’s life, so you’ll know how much to top-up from the bag,” explains Aimee. “If you’re cropping former pasture land, it’s possible quite a bit of organic N will be present and unlocked from the soil when it’s cultivated. Alternatively, if the land has been cropped over a number of seasons its organic N reserves may be low.”

    A starter fertiliser that includes nitrogen and phosphorus, like Diammonium Phosphate (DAP), will set up your crops well. “Germinating seeds need a readily accessible phosphorus supply to develop healthy root systems and the nitrogen will support early growth. The stronger the start, the better the chances of a good finish,” says Aimee.

    It also pays to be aware of micro-nutrient levels, particularly with brassicas and fodder beet, which may need boron to avoid brown heart and improve yield.

  3. Be realistic about yield
  4. “There’s not much point putting on enough nitrogen for a ten tonne crop if your soil and climate won’t support that level of yield,” says Aimee. “Well-informed yield estimates can help minimise waste and maximise the return on your nitrogen investment.”

    Tools such as the AmaizeN calculator (for maize) can help refine your predictions.

  5. Protect your N investment
  6. Keeping nitrogen where it’s needed is the next step. “Product choice is vital in cropping because using large volumes of N means the potential for loss is high,” says Aimee.

    Try to look beyond the up-front price tag. “Volatilisation can exceed 30 percent when urea is used for side-dressing crops. This means nearly a third of your valuable N is being lost as a gas. Using SustaiN keeps more of that N in the soil to support your developing plants,” says Aimee.

    Weed control will help stop invaders “stealing” applied nitrogen from your crop.

  7. Get the timing right
  8. “Plants only take up nitrogen when they are growing,” continues Aimee. “More specifically, you want to make it available when it will boost canopy growth, giving plants more power to convert sunlight into energy to improve yield.”

    Targeting application to high growth periods will also reduce the risk of nitrate poisoning. “If you apply N too late in the season, close to grazing when growth is slowing, the crop’s nitrate levels may get too high, resulting in stock losses or reduced performance.”

    Brassicas need nitrogen four to six weeks after emergence (around gumboot height) and again around eight to 12 weeks. Fodder beet requires a single application at canopy closure and N should be applied to maize once it reaches knee-height (technically, the six-true leaf stage).

    “SustaiN can help here, too,” adds Aimee.

    “It gives you more flexibility, reducing volatilisation losses if conditions aren’t ideal for N application when the crop needs it.”

Your local Fonterra Farm Source TSR or Ballance Nutrient Specialist can help you determine the right approach for your farm.

Article supplied by Ballance Agri-Nutrients