The expected long-term detrimental effects of continuous application of ammonia on soil strength, aggregate stability and dry bulk density*

الملخص

Soil strength has increased due to ammonium hydroxide (NH4OH) treatment as much as 112, and 150% for the 0 to 5 cm depth and 102, and 49% for the 5 to 10 cm depth in the SiL and SiC soil, respectively. The increase at the 0 to 5 cm depth was highly pronounced for the NH4OH + NaOH treatment in the SiC soils but not for the SiL soils (18 and 361% for the 0 to 5 cm depth, and 82, and 112% for the 5 to 10 cm depth in the SiL and SiC soils, respectively) probably due to the high moisture content of the 0 to 5 cm depth of the SiL soils as a result of the water bonding because of low infiltration rate and water penetration caused by the dispersion effect of high sodium. No other explanation can be given at this point. The increase was a lot more for the soil treated with 5% CaCO3, approximately 12 times, and 7 times for the 0 to 5 cm depth, and 8 times, and 3.5 times for the 5 to 10 cm depth in the SiL and SiC soils, respectively. The overall soil strength, however, is higher in the SiC soils than the SiL soils for both depths in all the treatments including the control.

The NH4OH had caused also a reduction in the size of soil aggregates or a break down of the aggregates due to the dispersion effect on both soils. The DBD, however, was not affected by the used treatments.

Inspite of the slight changes in the chemical analysis of the soils after the treatments, I consider no major change has occurred due to NFLOH and that the effect of NH4OH was mainly a physical effect rather than chemical.