MATERIALS AND METHODS
Combined effects of phosphorus fertilizer, phosphate-solubilising
bacteria and mycorrhizal fungus were determined on reducing
drought stress damages of grain corn (KSC704 commercial hybrid)
under field conditions in experimental farm College of Abouraihan,
University of Tehran (35°28’N, 42.51°17’E, altitude 1024 m). The
experiment was planted in 2009 as a randomized complete block
design with split-plot arrangement and three replications. The soil
texture was clay loam and the result of soil analysis presented in
Table 1.
Treatment consisted of three levels of drought stress: without
stress (irrigation after 50 mm evaporation from pan class A), low
drought stress (irrigation after 100 mm evaporation from pan class
A) and severe drought stress (irrigation after 150 mm evaporation
from pan class A). In sub-plots five compound fertilizer such as:
(b1) phosphate-solubilising bacteria with Mycorrhiza fungies, (b2)
phosphate-solubilising bacteria and Mycorrhiza fungi with 50%
super phosphate triple, (b3) phosphate-solubilising bacteria with
50% super phosphate triple, (b4) Mycorrhiza fungi with 50% super
phosphate triple and (b5) phosphate chemical fertilizer (100% super
phosphate triple) were used.
Phosphate solubilising microorganisms used in this experiment
were included Mycorrhiza fungi (Glomus mosseae) (with 65-70%
colonization rate). Also biofertilizer phosphate-solubilising bacteria
(biophosphor ®) was included Bacillus and Pseudomonas with
CFU=107.
Plants were grown in five-row plots with 5 m length and 0.75 cm
spacing between rows. The plant density was 66000 plant/ha.
Fertilizer was used based on soil test. Irrigation was performed on
class A evaporation pan for each treatment. Data was recorded on
10 competitive plants of each plot and grain yield (kg ha-1) was
calculated for the entire plot. Each plot was harvested at maturity
for yield and yield components and leaf area index and dry matter
were measured each 15 days to calculate Crop Growth Rate
(CGR), Net Assimilation Rate (NAR) and Leaf Area Index (LAI)
according to below equations:(1)LAI= LA/ SA
(2) CGR= (W2-W1) / SA(t2-t1) g.m-2.day-1
(3) NAR= (W2-W1) / (t2-t1) * (lnLA2-lnLA1) / (LA2-LA1) mg.mm-2.day-1
In above abbreviations: LA = Leaf Area, SA = Ground area that
occupied a plant. W = Dry matter, t = Day after planting.
Data was subjected to Analysis Of Variance (ANOVA) and the
treatment means was compared using Duncan’s multiple range test
(alpha = 5%). The analysis was done by MSTATC and SAS (Ver.
9.1) software. Microsoft office Excel was used for figures drawing
and indices calculation.
RESULTS