| dc.description.abstract | Alfalfa (Medicago sativa L.) seed production in western
Canada involves establishing the crop during the first year and
harvesting seed during the subsequent years. Therefore, seed
production has been restricted almost exclusively to winterhardy,
fall dormant cultivars. Moderately dormant and non-dormant
cultivars rarely survive the winter in western Canada, therefore
seed production from these cultivars may not be possible under
current management practices. The development of a production
system that allows seed production during the year of
establishment is required if these cultivars are to be grown for
commercial seed production in western Canada. There is a lack of
information on N2-fixation and the agronomic practices for
establishment year seed production. Field experiments were
conducted in 1992 and 1993 to determine how cultivar, seeding
rate and stage of plant development affect seed yield, dry matter
production and N2-fixation. An additional experiment was
designed to determine the effect of cultivar, seeding rate and
clipping management on alfalfa seed yield components when managed
for establishment year seed production.
The first experiment was established in a split plot design
with five alfalfa cultivars: Algonquin, Saranac, Saranac-In,
Nitro and CUF 101 at two seeding rates (3.36 kg ha-1 and 16.8 kg
ha-1
). N2-fixation was determined using the difference method on
intact excavated plants at different stage of plant development.
A wheat crop was seeded over the 1992 experimental plots to
estimate the actual N contribution to subsequent crops. Results
from the first experiment showed that the high seeding rate
showed better agronomic production than the low seeding rate for
most of the traits measured including seed yield. The dormant
cultivar, Algonquin, and the moderately dormant cultivar,
Saranac, had the highest seed yield. The total N yield ranged
from 97 to 139 kg N ha-1 and root plus crown N yield ranged from
42 to 60 kg N ha-1 during the mature seed stage. During both
years all cultivars had an equivalent quantity of N2-fixed.
Furthermore, depending upon stage of growth, N2-fixed comprised
37% to 59% of the total N in the crop, corresponding to 23 kg N
ha-1 to 74 kg N ha-1
• The average biomass in the root plus crown
portion at the mature seed stage ranged from 1,841 to 2,485 kg
ha-1 dry matter, and the root plus crown N yield available for
fall incorporation was 44 to 66 kg N ha-1
• Wheat yield was not
increased by planting it following any of the alfalfa cultivars
at either seeding rate.
The second experiment was established with three cultivars
(CUF 101, Cimarron VR, and Algonquin) at two seeding rates, 1.12
kg ha-1 and 3.36 kg ha-1 and subjected to two clipping treatments
(clipped and unclipped). This experiment showed that flowering
percentage and racemes per metre of row were highest for Cimarron
VR. Furthermore, there was no influence of clipping treatment or
seeding rate on plant height, number of racemes per metre of row
and number of pods per raceme and seed yield. Clipping reduced
lodging, but also delayed flowering. Cultivars produced similar
seed yields, but the overall yield was much lower than long term
averages in Manitoba. Seed yield components are predictors of
the potential seed yield. Measurements of seed yield components
was important in both years of this study because adverse
environmental conditions directly influenced pollination, seed
set, seed development, seed maturation and final seed yield.
In conclusion, the adverse environmental conditions during
1992 and 1993 affected N2-fixation and seed production. N2-
fixation continued during alfalfa seed production and provided
supplemental nitrogen to subsequent crops. Although
establishment year seed production was low in this research,
actual yields were equivalent to the provincial average on
established stands in 1992 and 1993. Therefore, further research
should be conducted to determine if establishment year seed
production is possible in western Canada. | en |
