The following guide for the purchase and application of fertilizer on crops is supposed to help farmers in growing good crops by using the right amount of fertilizer and by using the right fertilizer application rates.
The Fertilizer Act requires fertilizers be labelled according to their guaranteed analysis as per cent by weight of nitrogen (N), phosphate (P2O5), and potash (K2O). For example, 100 lb of 11-51-0 contains 11 lb of nitrogen (N), 51 lb of phosphate (P2O5), and 0 lb of potash (K2O). Fertilizer should be purchased on the basis of the price per lb or kg of nutrient not price per tonne of material. For example:
1) if urea (46-0-0) costs $265.00/tonne, the cost per kilogram or pound of nitrogen (N) is:
1000 kg x 46 = 460 kg or 1014 lb
$265.00 = $0.58/kg or $0.26/lb of N
(1 tonne = 1000 kg and 1 kg = 2.2 lb)
if ammonium nitrate (34-0-0) costs $220/tonne the cost per kg or lb of nitrogen (N) is:
1000 kg x 34 = 340 kg or 749 lb
$220.00 = $0.65/kg or $0.29/lb of N
In this example, urea cost more per tonne ($265.00) than ammonium nitrate ($220.00) but cost less per unit of N ($0.26/lb vs. $0.29).
Nitrogen fertilizers are very soluble and move readily in moist soil. Placement with or very near the seed is not necessary to ensure effective utilization. Placement options that can be considered include:
side-band or mid-row band at planting, and
seed row placement.
The relative efficiencies of the various methods depends on many factors. Broadcast application may be less effective than banded or seed row application under some conditions (see Table 6). Fertilizer placed in the seed row can delay or severely reduce crop emergence. The maximum rate that can be safely placed in the seed row depends on:
soil type (clay and organic matter content),
type of fertilizer,
row spacing, and
spread of seed and fertilizer (type of opener).
Guidelines for approximate safe rates of seed row nitrogen are shown in Tables 4 and 5. (Note: all rates are in lb/ac of N. To calculate the rate of urea divide by 0.46).
Banding fertilizer (8-15 cm deep) has become a common method of applying nitrogen fertilizers. Under conditions of low rainfall during the early growing season, deeper placement overcomes the problem of nitrogen being stranded in dry surface soil. Under wet soil conditions that can occur in early spring (during and just after spring thaw), fall applied nitrogen fertilizer can be lost by a process called denitrification. Late fall banding of an ammonium form of nitrogen (e.g., 82-0-0 or 46-0-0) will reduce losses.
Time of application
Fall is often an opportune time to apply fertilizers because of the availability of time and price discounts. However, excessively wet conditions in early spring that sometimes occur on fine textured and poorly drained soils in central and northern Alberta can cause significant losses of fall applied nitrogen. Early fall (before mid-October) broadcast applications are most subject to loss. Late fall banded applications of an ammonium form of nitrogen are less subject to loss. Table 6 shows the relative efficiency of fall and spring broadcast and banded applications under various conditions.