Biofertilizer
Recommended crop
Fertilizer saving
Azolla pinnata (fresh)
Lowland rice
30 - 50 kg N
Azolla pinnata (dry)
Wheat, potato, tobacco
30 - 50 kg N
Azotobacter chroococcum
Pearlmillet, sorghum, sugarcane, maize, potato, pigeonpea,
onion, cotton
30 - 50 kg N
Azospirillum lipoferum
Pearlmillet, fingermillet, sorghum, paddy, maize, potato, onion, cotton
20 - 40 kg N
Acetobacter diazotrophicus
Sugarcane
100 kg N
Rhizobium spp.
Pigeonpea, chickpea, greengram
30 - 50 kg N
Bacillus circulans
Cowpea
20 - 50 kg P2O5
Bacillus brevis
Sorghum, wheat, pearlmillet
20 - 50 kg P2O5
Bacillus congulans
Sorghum, cowpea, pearlmillet, groundnut
20 - 50 kg P2O5
Table 2. Biofertilizers that are used against various crops and the potential fertilizer savings achieved
(Source: Bhattacharjee & Dey, 2014; Afr J. Micro. Res. 8: 2332-2342).
There is a considerable drive to restore arbuscular mychorrhizal fungi
(AMF) in soils, thought to provide
the ‘glue’ (known as glomalin; a
glycoprotein that acts to bind mineral particles together, improving
soil quality) that keeps things intact
in the underground. The former’s
population numbers have been
decimated by continuous conventional tillage practices. Since some
farmlands have transitioned to implement reduced tillage techniques,
there has been a marked improvement, which has been correlated
with the proliferation and the associated activities of various soil mi-
crobial communities, including that
of AMF.
And so, precision agriculture and
integrated pest management of
this nature proposed may contribute to minimizing adverse environmental impacts of intensive agriculture practices and reduce per unit
production costs. Furthermore, systems ecology as a science is still in
its infancy and is on a steep discovery curve; nevertheless there are
core principles of this science that
can inform an improved design of
agricultural systems. Agricultural
management practices should be
Inrease in yield over yield obtained with
compared to chemical fertilizers (%)
Crop
Wheat
8 - 10
Rice
5
Maize
15 - 20
Sorghum
15 - 20
Potato
13
Carrot
16
Cauliflower
40
Tomato
2 - 24
Cotton
7 - 27
Sugarcane
9 - 24
Table 3. Effect of Azotobacter on crop yields
(Source: Bhattacharjee & Dey, 2014; Afr J. Micro. Res. 8: 2332-2342).
designed to maximize the biological processes that support sustainable agricultural systems. In recent
years it has been proposed that
through the use of “smart field”
generated information, a prescription for timely and low-level production interventions will pave the
way forward to better crop maintenance and soil husbandry. This
should also ensure that superior
crop cultivars will emerge that are
highly responsive to beneficial associative microbes in the soil. In
future, PGP-rhizomicrobes are expected to replace the chemical fertilizers (see Table 2), pesticides and
artificial growth regulators, which
have numerous side-effects to sustainable agriculture. Ongoing research and understanding of
mechanisms of PGPR mediatedphytostimulation would pave the
way to discover more competent
rhizobacterial strains, which may
work under diverse agro-ecological
conditions. Microbial inoculant
technology will be the premise for
integrated solutions to agroenvironmental problems because
they improve soil fertility, promote
plant growth and stress tolerance
of crops, in so doing increasing
crop productivity, without compromising environmental integrity (see
Table 3).