IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Title Evaluation of elite commercial soybean varieties for N2 fixation and grain yield in South
Africa
Author Nyamande Mapope 1 and Felix D Dakora 2
Poster Board Number 27
1 Department of Crop Science, Tshwane University of Technology
2 Department Chemistry, Faculty of Science, Tshwane University of Technology
South Africa is currently a net importer of soybean which is much needed for poultry production and the livestock
industry. There is therefore an urgency to increase local production of soybean through breeding of improved
varieties, their evaluation for adaptability, and selection for high grain yield and symbiotic performance. This
study assessed plant growth, N2 fixation, and grain yield in thirteen commercially-bred, elite soybean genotypes
under field conditions in the three soybean-producing provinces of South Africa. The varieties used originated
from Pioneer, Pannar and Linkseed in South Africa. The experiments were laid out in a randomized block design
with four replications. At pod filling (R6) stage, 10 soybean plants were randomly sampled from each plot, and
oven-dried (60oC) separately, weighed and ground into fine powder (0.85mm) for 15N isotope analysis. The data
obtained revealed marked differences in dry matter yield, N concentration, N content, δ15N, %Ndfa and actual
amounts of N fixed among the thirteen soybean genotypes at each of the three sites. Dry matter yield ranged
from 26 g.plant-1 for PAN1454 to 50 g.plant-1 for PAN737 at Balfour in Mpumalanga, and 33 to 73 g.plant-1 at
Herman in the North West Province. The N concentrations of shoots also differed between and among
genotypes at each site, and ranged from 2.2 % for 95Y20 to 3.5 % for PAN1666 at Balfour in Mpumalanga. The
δ15N values ranged from -0.73 ‰ for PAN1454 to 2.33 ‰ for PAN1666 at Balfour in Mpumalanga. Cross site
analysis also revealed significant interaction between site and varieties. PAN1666 showed the lowest %Ndfa
(64%) and 95Y40 the highest %Ndfa (85%) across all sites. The actual amounts of N-fixed ranged from 114
kg.ha-1 for 95Y20 to 215 kg.ha-1 for PAN1666 across the sites. Soil N uptake was generally low across the
sites, indicating greater dependence of these elite varieties on N2 fixed for their N nutrition. PAN1666 for
accumulated greater dry matter and amount of N-fixed across all sites and was therefore the best variety for use
by farmers.
142
2011