الفهرس 
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Abstract
The present work was planned to study the influence of bio- organic
additives, i.e. compost “CM” and farmyard manure “FYM”, as organic
fertilizers, Bacillus megaterium “Bm” and Bacillus polymyxa “Bp”, as
biofertilizers, on phosphate solubilization in sandy and alluvial clayey
soils, in pot experiments along 120 days incubation period, under
greenhouse conditions. Each soil bulk was divided into portions, each
was assigned to one treatment, and each treatment replicated 3 times.
Rock phosphate, as insoluble phosphorus source was added at a rate
of 1000 ppm (mg Kg soil-1). CM or FYM was added, at a rate of 2%
C to each soil. Each amount of soil replicate, weighing 500 g of the
soil mixed with rock phosphate and organic fertilizer, was contained
in a pot. Bm or Bp was added at a level of 1 ml of culture suspension to
each potted soil.
Results showed that, all added amendments increased phosphate
solubilization in both soils with time of incubation. The single
application of each bio-and organic fertilizers showed the following
mean rates of increases above the control: CM (48 & 31%), FYM
(32& 18%), Bm (21 & 8%) and Bp (12 & 4%), for the sandy and
clayey soils, respectively. Incorporation of CM or FYM plus each of the
biofertilizers greatly augmented phosphate solubilization, as compared
with the single additive of each of the bio-organics. The increases
resulted by using CM or FYM each with Bm, reached 105 & 62% and
88 & 51% above the control treatment in the sandy and clay soils,
respectively.
Addition of CM or FYM slightly decreased the pH values of both
soils, at the first period and somewhat had recovered towards the end of among the applied treatments on soil reaction “pH value”, generally
within the succeeding intervals of incubation time. Nevertheless, the
organic fertilizers generally excelled the bio-fertilizers, as well as
combinations of the bio-organic treatments were thus better in such
concern (modifying the soil pH).
All amendments raised the concentration of total soluble salts
“TSS” in the two soils with time of incubation. The following order was
gained for the effect of the bio-organic fertilizers on concentration of
TSS, when each was added singly: CM ( 20 & 28% ), FYM ( 33 & 40% ),
Bm (8 & 11% ), Bp ( 0 & 4% ) for the sandy and clayey soils, in order.
Introduction of CM or FYM, each with Bm increased the concentration of
the TSS by 48 & 59% and 65 & 80% above the control, in the sandy and
clayey soils, respectively. Combination between the CM or FYM with the
Bp resulted in lower increases, i.e. 40 & 52% and 55 & 66%,
correspondingly.
Addition of each of CM or FYM to the sandy soil increased the
soluble calcium content by 87 and 58% above the control, respectively.
The biofertilizers “Bm” and “Bp” slightly improved calcium solubility in
the soil by 20 and 4%, respectively. Dual application of CM with Bm
gave the highest values and followed by CM plus Bp to give 167 and
133% referring to the control, respectively. Corresponding figures of the
clayey soil were 200, 164, 150, 132% above the control treatment, for
CM + Bm, CM + Bp, FYM + Bm and FYM +Bp, in order.
Application of CM or FYM to the sandy soil led to promote the
rate of soil respiration represented by the daily CO2 evolution by 52 and
34 % above the control, orderly. Also, the biofertilizers “Bm” and “Bp”
stimulated soil respiration to acheive 16 and 7%, respectively. The
highest values of sandy soil respiration were obtained by incorporation of the double additives, to reach 104 & 86% with CM + Bm and CM + Bp,
referring to the control, whereas FYM + Bm and FYM +Bp recorded
72 & 58%, respectively. Similar trend was found for the clayey soil,
where the respiration rate raised with the time of incubation, to give the
highest daily values after 120 days of incubation. Increases of CO2
evolution rate occurred in the clay soil were higher than those in the
sandy soil, as they were 114 & 92 % and 76 & 65% for CM+ Bm, CM+
BP, FYM + Bm and FYM + Bp, respectively.