Key things a farmer needs to know about fertilizer placement:
- “Safe” rates for fertilizer placement is not a big issue in seeding systems that adequately separate seed and fertilizer (multi-pass or double-shoot).
- Seed Bed Utilization (SBU) is a mathematical calculation of fertilizer spread and concentration for a one pass, single-shoot system that MUST be interpreted for variations in soil texture, crop-type and fertilizer choice.
- Soil moisture, temperature, and rates influence fertilizer efficiency and are all factors for potential crop injury due to seed-placed fertilizer.
Seed-placed N can be a complex issue!
- Crop emergence does not always relate to crop yield. Unusual growing conditions can affect seed-placed N results year to year.
- Rainfall soon after seeding can improve germination and emergence, thus reducing the possible impact of fertilizer injury to seedlings.
- Seedling stress can be intensified by other basic agronomic mistakes (poor-quality seed, deep seeding, soil clods and crusting, herbicide residue, worn-out openers, etc.). Whenever possible, a double-shoot direct seeding system should be used for seed and fertilizer placement to avoid germination and emergence problems.
Guidelines for Seed-placed N
Rates – The risk of crop seedling injury increases with higher target N rates.
Soil Texture – The sandier the soil, the bigger the risk for emergence damage and yield loss.
Seedbed Moisture – The lower the soil moisture, the higher the risk for placing nitrogen in the vicinity of the seed.
Row Spacing – The wider a part the seedrows, the greater the risk due to increased fertilizer concentrations.
Width of Spread – The narrower the seed opener, the greater the risk.
Crop Type – At a given rate of N, smaller seeds are generally more subject to injury. Peas and lentils are very sensitive to seed-placed N.
Organic Matter – Higher levels of organic matter in the soil lessen risk. (ie: eroded knolls may show greater damage from seed-placed fertilizer).
So, the Point is?
H2O and its effect on plant growth, fertilizer efficiency and optimum crop yield is ESSENTIAL – without it nothing else will matter! Where seedbed moisture is low or weather is conducive to evaporation (hot & windy), a seeding system that conserves soil moisture is a good idea. Retaining a mulch of protective crop residue by minimizing tillage before and after seeding helps achieve that goal. Direct seeding into standing stubble provides the opportunity. RTL promotes one-pass disturbance direct seeding (less than 40% SBU) to maximize the benefits of reducing tillage.
However....
Seedbed moisture can rapidly decline after seeding depending on the equipment used, field conditions (including crop residue cover), and the weather. One-pass seeding when it is dry may require high soil disturbance in a single-shoot system to achieve safe and adequate distribution of the seed and fertilizer, which may cause further moisture loss. Fertilizer rates might also need to be reduced.
Since the fate of nutrients in the soil cannot be generalized, it is important to understand how soil texture, moisture and organic matter interact with fertilizer rates. Research under direct seeding systems appears to indicate that positive changes occur in nutrient cycling as soil is left undisturbed and crop rotations are diversified. But there is no better teacher than experience - Field check strips with variable rates and no-fertilizer treatments are a smart way for growers to learn about fertilizer placement and adjust their seeding systems accordingly. Sometimes a simple test can be done by a flip of the switch on the fertilizer clutch! Plan ahead, so when it's seeding time you are ready to find out what you want to know about fertilizer placement! (it likely won't happen all in one spring).
Contact an
RTL agronomist if you have questions about fertilizer placement for direct seeding.
