The high price of fertilizer is boosting interest in efficient
nutrient use.
Every farm and field is different. It is important to select the best management practices suited to field conditions.
Efficiency has many facets. Nutrient management is more than applying the minimum to get an average crop. It needs to consider how the productivity of a cropping system is going to be maintained over the long term.
Following are tips for achieving revenue-generating yields while keeping fertilizer bills reasonable:
Soils can contain rich reserves of nutrients. Test once every two to three years for stable nutrients like phosphorus and potassium.
For mobile nutrients like nitrogen, test for each crop, but at the right time.
For corn, the soil nitrate test is effective only if the sample is taken before sidedressing, when the corn is 15-30 centimetres tall.
For cereals and oilseeds, late fall or early spring samples effectively estimate nitrogen supply.
Be sure you know whether the
soil test lab is including any nitrogen credits from previous legume
crops.
- Consider crop removal
Do you know how much phosphorus and potassium the last crop took out of the soil? You can estimate it if you know yield levels. Unless soils contain so much that you don’t worry about depleting fertility, what was removed should likely be replaced.
- Set realistic goals
Being sure that nutrients are applied to meet the target crop yield is critical to fertilizer efficiency. Too much or too little fertilizer will result in reduced nutrient use efficiency or lost yield or crop quality. Be sure yield goals reflect past production history, appropriate for each field.
- Use all nutrient sources
It can be a challenge to ensure that manure is applied to minimize nutrient losses. Storage should protect against those losses.
Manure application shouldn’t get in the way of timely planting. Manure and other organic materials should be directed to the soils that need the organic matter most. Analyzing the material helps predict its nutrient credits to ensure that fertilizers appropriately supplement what is applied.
- Keep the proper balance
When fertilizer prices rise, it is common to see growers reduce the application of all nutrients except nitrogen. For a soil with adequate supplies of phosphorus, potassium and sulfur, this can work in your favour.
However, if soil is low in any of these nutrients, it may be better to lower the rates of all those required to optimize crop yield and quality.
Remember, low levels of other nutrients will prevent the full yield expression of applied nitrogen.
* Manage soil acidity
- Manage soil acidity
Liming acid soils produces many benefits. Among these are more effective nitrogen fixation in legumes and better availability and more efficient use of phosphorus and potassium. Soils with a pH of less than five to six are candidates for lime, depending on the crop grown.
* Manage for economic yield
- Manage for economic yield
Anything that limits yield usually limits nutrient use efficiency. Choose the right genetics and plant spacing, seed at the right time and manage soils for optimum structure. Ensuring that all field operations get done on time requires attention to logistics, but pays off with a better ratio of nutrients harvested versus applied.
- Time applications
Especially for nitrogen, the closer before plant uptake, the better. Nitrogen applied in the fall should be in the ammonium form – urea or anhydrous ammonia – and banded below the surface only after the soil has cooled to -10 C. Applying all the crop nitrogen requirements before or at planting is effective in Western Canada.
- Control release
You may not always be able to apply just before plant uptake. Just after is too late. Many useful products that delay conversion of nitrogen sources to nitrate have entered the market.
These include inhibitors of urease or nitrification or coatings that slow the release of urea into solution.
The key is to find a product that releases nitrogen in the root zone just before the plant needs it.
* Band in the right place
- Band in the right place
Phosphorus is particularly effective at invigorating young seedlings when it is placed in a band close to the seed. The starter band should include nitrogen and potassium as well if they are required. Higher rates need to be moved farther from the seed to avoid damage.
* Test on-farm
- Test on-farm
Recommendations are only as good as the research relating to crop response. For important nutrient questions that the lab can’t answer, replicated strip trials on the farm may be the only solution.
* Consult a credible adviser
- Consult a credible adviser
Managing nutrients is complex and site-specific. Certified crop advisers should be able to balance not only the nutrients needed for a crop, but all the many pieces of advice that farmers encounter as well.
