How much more crop can you grow if you get your nitrogen strategy right?
This is difficult to answer as nitrogen (N) is only one piece of the picture. Ballance Agri-Nutrients Science Extension Officer Aimee Dawson says final yield will depend on the crop, soil, weather and pressure from pests or disease. “But there are things you can do to help get the best return from your nitrogen investment,” says Aimee.
Soil tests are a good starting point. “To get the most out of any nitrogen application, you need to address other factors that could limit growth,” says Aimee. “This can take time. For example, it takes 12 months or more for lime to change soil pH. You may not be able to counteract some limiting factors before sowing, but knowing what they are will still help with your crop and nutrient management and ultimately your productivity.”
Using a starter fertiliser containing phosphorus and nitrogen will encourage healthy root development and support early growth. “The stronger the start, the better the chances of a good finish,” says Aimee. “Di-ammonium phosphate (DAP) is one option or Cropzeal Boron Boost if you are sowing brassicas or fodder beet and need to guard against brown heart. Applying boron in a granulated compound product like this results in a more even spread than you would get using a mix.”
Good weed control will stop invaders “stealing” applied nitrogen from your crop. Be wary of spray residues if planting fodder beet.
Follow the four Rs for the best return on investment.
Crops only take up nitrogen when they are growing. “You want to get nitrogen on when it will boost canopy growth, which gives plants more power to convert sunlight into energy to improve yield,” says Aimee.
Brassicas usually need nitrogen four to six weeks after emergence and again at around eight to 12 weeks. Fodder beet requires a single application at canopy closure. Apply nitrogen to knee-high maize (technically, the six-true leaf stage).
Targeting application to high-growth periods will also reduce the risk of nitrate poisoning. “If you apply nitrogen too late in the season, close to grazing when growth is slowing, nitrate levels may get too high,” says Aimee.
“Applying excess nitrogen just raises the plant’s protein content, which doesn’t increase yield. When the crop is grazed, nitrogen gets re-deposited in urine patches, creating an environmental risk. In some forage crops, crude protein levels are getting to 20 percent, which is too high. Aim for 15 percent,” says Aimee.
So how do you know when enough is enough? Aimee recommends using Available N tests to see how much nitrogen is already in the soil for the crop. “You may be able to reduce the amount you need from the bag. Be realistic about your expected yield – there’s no point putting on nitrogen for a yield you’re unlikely to achieve.”
Cropping often uses large volumes of nitrogen and the potential for loss is high.. “Volatilisation can exceed 30 percent when urea is used for side-dressing crops. Using SustaiN keeps more nitrogen in the soil to support your growing plants,” says Aimee.
SustaiN gives you flexibility by reducing losses if conditions aren’t ideal for nitrogen application when the crop needs it most.
Herbage testing as you go can help diagnose issues – particularly micronutrient deficiencies – in underperforming crops, allowing you to address them with the appropriate product.
Finally, good fertiliser application practice places nitrogen where it is needed, reducing waste and increasing your return on investment.
For advice on the right nitrogen strategy for your crops, talk to your local Fonterra Farm Source TSR or Ballance Nutrient Specialist.
Article supplied by Ballance Agri-Nutrients