Agriculture Reference
In-Depth Information
A review on results from
Azospirillum
inoculation experiments across the
world and covering 20 years was conducted by [11]. They found a success
rate of 60-70% with statistically signifi cant yield increases on the order of
5-30%. However, the vast majority of these trials were on wheat, maize,
sorghum, or millet, and only one of the experiments included in the analy-
sis was on rice. Consequently, results from biofertilizer use in rice are still
rare. Some reports from groups promoting the use of biofertilizers indicat-
ed considerable yield increases upon their use.
Trichoderma harzianum
,
used as a coating agent for rice seed, was reported to result in a 15-20%
yield increase compared with rice plants receiving full inorganic fertil-
izer rates only [22]. As already mentioned above [8], reported enhanced
growth and development of rice and maize after the use of biofertilizer
containing
Azospirillum
spp, and asserted the biofertilizer would provide
30-50% of the crop's N requirement. Similarly, [6] claimed that the in-
oculation of rice seedlings with
Azotobacter
spp. and
Azospirillum
spp.
was able to substitute for the application of inorganic N fertilizer, and that
this technology enabled rice yields of 3.9 to 6.4 t·ha
−1
(yield increases in
comparison with the control were about 2-3 t·ha
−1
). Another study tested
the effect of rice root inoculation with
Azospirillum
spp. under different N
fertility levels, and found a more pronounced yield response at lower lev-
els of inorganic N fertilization [24]. Generally, rice yield increases in this
study were lower, and ranged around 0.5 t·ha
−1
. A yield-increasing effect
on rice by inoculation with
Azospirillum
sp. strain B510 was also shown
by [25] but the experiment was conducted in pots only.
Based on these reports, it can be assumed that biofertilizers could of-
fer an opportunity for rice farmers to increase yields, productivity, and
resource use effi ciency. And, the increasing availability of biofertilizers
in many countries and regions and the sometimes aggressive marketing
brings ever more farmers into contact with this technology. However, rice
farmers get little advice on biofertilizers and their use from research or
extension because so little is known on their usefulness in rice. Necessary
would be recommendations describing under which conditions biofertiliz-
ers are effective, what their effect on the crop is, and how they should best
be used. To start addressing these issues, we conducted this study, testing
different biofertilizers in an irrigated lowland rice system in the Philip-
pines during four seasons. The objectives of the study were (1) to evaluate
