Agriculture Reference
In-Depth Information
The grain yield increase due to biofertilizer only (0% RR inorganic fer-
tilizer treatment) usually ranged from 200 to 300 kg grain ha
−1
for the best
biofertilizers with the exception of the 2010 WS, when the BN treatment
had an almost 800 kg·ha
−1
better grain yield than the Control. In relative
terms (Table 5), the seasonal yield increase across fertilizer treatments was
between 5% and 18% for the BN biofertilizer (up to 24% for individual
treatment combinations), between 3% and 13% for the BS biofertilizer (up
to 24% for individual treatment combinations), and between 1% and 9%
for the BG biofertilizer (up to 28% for individual treatment combinations).
For the calculation of the relative yield increase, only average values could
be compared and no statistical analysis could be conducted.
The effect of biofertilizer on the agronomic effi ciency of N fertilizer
(AEN) is shown in Table 6. For these calculations, the yield of each treat-
ment was compared with the grain yield baseline (the Control treatment in
which no biofertilizer and no inorganic fertilizer were used) and the yield
increase was divided by the N rate applied. Again, only average values
could be compared and no statistical analysis was possible. The results
(Table 6) indicate considerably higher overall AEN values in the 2010 WS
and the 2010/11 DS. Also, the AEN values are generally higher at low N
rates and decrease with higher N application rates. The biggest AEN in-
crease caused by biofertilizer occurred at the lowest N fertilizer rate (25%
RR treatment), and, among the different biofertilizers tested, the BN bio-
fertilizer resulted in the highest and most consistent AENs.
In our experiments, the selected biofertilizers were used as recom-
mended by the producers but we could not check the viability or the con-
tents of the products. Thus, we did not verify whether the biofertilizers
contained the declared organisms (Table 6; the contents of BG remained
unidentifi ed) or the required number of living cells in the inoculate. The
importance of quality control and regulation for biofertilizer production
was emphasized by [31], who also pointed out that the frequent absence of
such mechanisms can cause non-functional products. Maintenance of high
standards for
Azospirillum
inoculants with proven effi cient strains and cell
numbers on the order of 1 × 10
9
to 1 × 10
10
colony-forming units (cfu) g
−1
or mL
−1
was also requested by [11]. But, the fact that the products in our
study caused a signifi cant effect on grain yield in three out of four sea-
sons (only two out of four seasons for BG) indicated that the biofertilizers
