Agronomy Library > Soil Conservation

Seeding Time and Fertilizer Placement
Author: Ron Heller, Reduced Tillage LINKAGES
Date Created: March 07, 2005
Last Reviewed: February 01, 2007

Key things a farmer needs to know about fertilizer placement:
The “Safe” rates of applied fertilizer is not a big issue for seeding systems that adequately separate seed and fertilizer (two-pass; double or multi-shoot).
Seed Bed Utilization (SBU)
 a mathematical calculation of fertilizer spread and concentration for a one pass, single-shoot system, must be interpreted for variations in soil, crop and fertilizer.
Soil moisture, temperature, and placement influence fertilizer efficiency. 

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). 

Guidelines for Seed-placed N
Rates – The chance for 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 (canola may be an exception).
Row Spacing – The wider apart the rows, the greater the risk.
Width of Spread – The narrower the ground opener, the greater the risk.
Crop Type – At a given rate of N, smaller seeds are 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). 

The following links are guidelines to safe rates :
Don't Gamble With Fertilizer Rates!
Alberta Fertilizer Guide

So, the Point is?
H2O and its effect on plant growth, fertilizer efficiency and optimum crop yield is a no-brainer – without it nothing else matters!! Where seedbed moisture is low or weather is conducive to evaporation (hot & windy), a seeding system that saves available soil moisture is a good idea. Direct seeding into standing stubble provides that opportunity. 

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.

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 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 stripswith variable rates and no-fertilizer treatments are a smart way for growers to learn about fertilizer placement and adjust their seeding systems accordingly. 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).