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esult of higher dosages, no considerable changes were observed in nitrate content.
However, the nitrate content of treatments 8, 9 and 10 was significantly higher than that
of the control.
We have also measured the readily available phosphorus and potassium content.
The AL-soluble phosphorus content of soils significantly reduced as a result of
bentonite treatments, regardless of dosage. The phosphorus content of composted
treatments, however, increased significantly, and no considerable reduction was found
even in the high dosage treatments (treatments 9 and 10).
The readily available potassium content of soils increased slightly as a result of
bentonite treatments, but the values were not significantly different from those of the
control. However, the composted treatments significantly increased the potassium
content of soils.
Table 1. The effect of treatments on the readily available nutrient content of the soil
(average of 2003-2005)
Sample
Dosage
Treatment
Nitrate-N
(mg - kg -1 )
AL-P2O5
(mg kg -1 )
AL-K2O
(mg k g -1 )
Bentonite
1. - 0 (t/ha) 6.50 148.77 250.97
2. 1.× 5 (t/ha) 6.23 119.43 253.77
3. 2.× 10 (t/ha) 5.93 118.67 248.77
4. 3.× 15 (t/ha) 5.90 141.53 277.50
5. 4.× 20 (t/ha) 5.80 124.57 237.60
Bentonite+manure
6. - 0 6.70 145.90 252.20
7. 1.× 5 (t/ha)+9 (t/ha) 7.17 156.87 301.80
8. 2.× 10 (t/ha)+18 (t/ha) 8.20 153.53 312.93
9. 3.× 15 (t/ha)+27 (t/ha) 8.50 163.87 283.53
10. 4.× 20 (t/ha)+36 (t/ha) 8.40 154.87 307.20
Significant Difference (5%) 0.25 3.65 15.6
The impact of treatments on soil microbial parameters (Table 2) is demonstrated via
specific characteristics of the carbon cycle.
Bentonite treatments increased slightly the total number of bacteria and the
amount of microscopic fungi, the increase of the latter was not significant. Higher
dosages resulted in a decrease in the number of microbes. In both groups of microbes,
the medium dosages had an inducing effect. Composted treatments had a higher
increasing effect on the amount of microbes, though it was not always significant.
The number of cellulose-decomposing bacteria was increased considerably by
treatments of bentonite no. 3 and treatment no. 2 of the combined series. High bentonite
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