Agriculture Reference
In-Depth Information
question of which process or combination of processes is at work here, if
that is possible at all under fi eld conditions [9].
7.4 SUMMARY AND CONCLUSIONS
The study was conducted to evaluate the effect of different biofertilizers
on the grain yield of lowland rice, and investigate possible interaction ef-
fects with different inorganic fertilizer amounts. The results showed sig-
nificant yield increases for all products tested in some seasons but the most
consistent results were achieved by the
Azospirillum
-based biofertilizer. In
most cases, the observed grain yield increases were not huge (0.2 to 0.5
t·ha
−1
) but could provide substantial income gains given the relatively low
costs of all biofertilizers tested. The positive effect of the tested biofertiliz-
ers was not limited to low rates of inorganic fertilizers and some effect was
still observed at grain yields up to 5 t·ha
−1
. However, the trends in our re-
sults seem to indicate that the use of biofertilizers might be most helpful in
low- to medium-input systems. The results achieved can already be used
to develop better advice for farmers on biofertilizer use in lowland rice,
but several important questions remain. In particular, biofertilizers need to
be evaluated under conditions with abiotic stresses typical for most low- to
medium-input systems (e.g., under drought or low soil fertility) and with a
range of germplasm because their effect might depend also on the variety
used. More upstream-oriented research would be needed to better under-
stand the actual mechanisms involved, which in turn could also contribute
to making the best use of biofertilizers in rice-based systems.
REFERENCES
1.
Vessey, J.K. Plant growth promoting rhizobacteria as biofertilizers. Plant Soil 2003,
255, 571-586, doi:10.1023/A:1026037216893.
2.
Davidson, J. Plant beneficial bacteria. Biotechnol. 1988, 6, 282-286, doi:10.1038/
nbt0388-282.
3.
Dela Cruz, R.E. State of the art in biotechnology: Crop production. In Biotechnol-
ogy for Agriculture, Forestry and the Environment; PCARRD: Los Baños, Laguna,
Philippines, 1993.
