Page 2 Plant-Bacteria Interactions Edited by Iqbal Ahmad, John ...

Table 9.2 Grain yields of wheat in the best experimental
treatments versus grain yields in adjacent farmers’ fields at
different locations in Kafr El-Sheikh, Nile delta, Egypt, 2002–2003.
Farm location Wheat variety
9.6 Importance of Endophytic Rhizobia–Rice Association in Agroecosystemsj179
Best experimental
treatment:
inoculated
strain þ kg N
fertilizer
Yield of
the best
experimental
treatment
(kg ha 1 )
Yield in the rest
of the same
farmer's field
(no researcher
supervision)
(kg ha 1 ) a
Increase over
farmer’s yield
1 Sakha 93 EW 54 þ 180 N 7112 6120 16.2%
2 Sakha 61 EW 72 þ 120 N 7382 5712 29.2%
3 Sakha 61 EW 72 þ 180 N 8247 6936 18.9%
4 Sakha 61 EW 72 þ 60 N 5802 4896 18.5%
Source: Dazzo and Yanni [59].
EW: rhizobial wheat-root endocolonizer used at the rate of 720 g peat-based inoculum
(10 9 CFU g 1 ) for inoculation of 144 kg wheat seeds for cultivation of one hectare. The method of
inoculation involved mixing the seeds with the inoculum in the presence of a suitable quantity of
a solution with an adhesive material such as pure Arabic gum, gelatin or sucrose. The mixed
seeds were left for some time in the shade and then planted as fast as possible during sunset
followed by irrigation of the field area. Nitrogen, kg N ha 1 , was applied as urea (46% N) in two
equal doses just before sowing and 75 days later.
a Recommended rate of nitrogen fertilizer for the tested wheat varieties when used without
inoculation with biofertilizers was 180 kg N ha 1 . This rate was used by the farmer in the part of
the field that was not supervised by the research personnel.
increases in grain yield resulting from inoculation with those selected strains of
our cereal-adapted rhizobia have occurred in 16 of 18 field tests for rice (89%) and in 18
of 19 field tests for wheat (95%) [1,7] (Yanni and Dazzo, unpublished data). Tables 9.1
and 9.2 summarize the data on grain yield from the recent scaled-up experiments on
farmers fields. They illustrate the best performance obtained with field inoculation
treatments using our cereal-adapted strains on the scaled-up experimental plots versus
yields of the same variety obtained simultaneously by traditional agricultural practices
on adjacent fields without inoculation or supervision by research personnel.
Increases in grain yields of rice and wheat ranged between 3.5 and 30.3% and
from 16.2 to 29.2%, respectively, using the researchers package of agronomic
treatments rather than farmers practices (Tables 9.1 and 9.2). The best inoculation
responses for rice occurred with an inoculum combining two strains of rice-adapted
rhizobia (rather than one). The wheat and rice varieties tested in most of these
experiments displayed an increase in agronomic nitrogen fertilizer use efficiency
(kg grain yield/kg fertilizer-N applied) indicating that those rhizobial strains can
help these crops utilize the nitrogen taken up more efficiently to produce grain with
less dependence on nitrogen fertilizer inputs. The results, with a few exceptions, also
suggest that even after the nitrogen requirements have been satisfied, our microbial
inoculants facilitate the acquisition of other nutrients, which then become the next
limiting factor(s) for rice and wheat productivity in these fields. The exceptions of no
inoculation response were most likely a result of the natural widespread abundance
of the same inoculant strain(s) in the same field, thus needing no inoculation. This is
being examined further by studies of autecological biogeography [50].