Effect of Compaction on Some Chemical and Biological Properties of Two Fine and Coarse Textured Soils

Effect of compaction on soil chemical and biological properties was studied using a factorial experiment with completely randomized design and three replications. Treatments included soil compaction at three levels (normal bulk density، and 10% and 20 percent higher bulk density by compaction)، two types of soil (light and heavy texture)، and two measuring times (one week after wheat planting and after plant harvest). Chemical properties including pH، total nitrogen، and organic matter، and biological properties of respiratory and urease enzyme activity were measured. Results showed that the amount of respiration and urease enzyme activity in natural densities، with an average of، respectively، 47. 18 µg CO2 and 65. 08 µg NH4 per gram of soil، had the maximum values. Also، normal compaction with a mean of 0. 131 percent nitrogen content had the maximum. The results indicated that by increasing soil compaction، index of soil mechanical resistance would increase and، by changing pH، the soil microbial activity would change in the way that soil respiration and enzyme urease activities would decrease. Consequently، the amount of soil nitrogen will decrease.