Agronomic Comparison of Nitrogen Fertilizer Practices in Saskatchewan
Thavarajah, D.. 2001. M.Sc. Thesis. Dept. Soil Science, University of Saskatchewan, Saskatoon, SK
Abstract
The widespread adoption of direct seeding-fertilizing in western Canada in recent
years has led to the development of new fertilizer placement techniques such as side-row
and mid-row banding. The objective of this study was to examine how nitrogen (N)
fertilizer rate, form [urea versus anhydrous ammonia (AA)] and placement (side versus
mid-row banding) affected yield, protein and crop N recovery in a direct seeding system
for three crops (wheat, canola and flax) at four locations in Saskatchewan.
Field experiments were conducted at four sites in four Saskatchewan soil-climatic
zones: Star City (Moist Black), Indian Head (Black), Scott (Moist Dark Brown) and
Swift Current (Brown). Each study site had 14 treatments with four replicates and three
different crops. Grain yield, protein content, apparent N use efficiency (NUE), total N
uptake and fall soil available N concentrations after harvest were measured. Additionally,
a study was conducted at the Star City site in which ion exchange resin membrane probes
(PRS™) were used to measure N and P supply rates from fertilizer bands to the seed row
from seeding until canola plants emerged.
Generally, the rate of N fertilizer had a greater agronomic impact than different N
placement methods and forms for all three crops. Maximum yield was generally achieved
at the high rate (120 kg N ha
-1
) for wheat and at the medium rate (80 kg N ha-1
) for canola
and at the low rate (40 kg N ha-1
) for flax. The different N forms and placement methods
had relatively small and inconsistent effects on all three crops under better soil moisture
conditions as observed at the Star City and Indian Head sites. Under dry spring soil
conditions and where soil available N was low, as at the Scott site, side-row band
placement was a better method and urea was a better form than anhydrous in terms of
yield response and crop N recovery. Under fallow conditions, N placement or form was
less important, likely as a result of the high available N in the soil after the fallow period.
Among the crops, flax tended to be less responsive to N fertilizer management as
compared to wheat and canola. The Indian Head and Star City soils had lower responses
to added N fertilizer than the Scott soils, which may reflect greater contribution of
available N by mineralization over the growing season. Overall, relative performance of
different N forms and placement methods appears to be related to spring soil moisture
conditions, as these conditions influenced N fertilizer losses by volatilization and N
fertilizer mobility in the soil.
In the N supply rate process study, side-row banded urea at the medium N rate (80
kg N ha-1) showed significantly higher available N supply rates to the seed-row than mid-row band placement. Side-row banding may be of benefit when conditions such as low
soil moisture restrict root growth and N movement as observed at the Scott site. At high
N rates with sensitive crops such as canola, the high supplies could also cause seedling
damage. However, as shown in the yield and NUE data, the position of the fertilizer N
band in relation to the seed row had relatively less impact on agronomic characteristics
than the rate of added N. The largest influence of N fertilizer form and band placement
strategy might be anticipated under dry conditions, where lack of moisture may restrict
mobility of the N and also enhance losses of N by volatilization.
