عنوان مقاله [English]
Introduction: Soil compaction has become a widespread problem in the world and it is considered as one of the main factors affecting land degradation in arid and semi-arid agricultural land. Compaction in arable soils is a gradual phenomenon that appearing over time and most important factors that influence it include: soil properties, high clay content, low organic matter, and frequency of wet-dry in the soil, impervious layer of soil, load heavy agricultural implements and soil and water mismanagement. Compaction induced soil degradation affects about 68 million hectares of land globally. The vast majority of compaction in modern agriculture is caused by vehicular traffic. Carbon sequestration by long-term management operation of the plant and soil, not only increase the soil carbon storage but also lead to reduce the carbon exchange and greenhouse gases emissions like CO2 from the soil profile. The aim of this study was evaluating the effect of soil compaction on carbon and nitrogen sequestration of wheat and soil and some soil physical properties such as: aggregate stability, saturated soil moisture content, bulk density and soil porosity.
Materials and Methods: This experiment was accomplished in which is located near Aq Qala in a randomized completely block design (with 4 treatments and 3 replications). Soil compaction was artificially created by using a 5/7 ton heavy tractor. The treatments arrangements were: 1) T1: control, 2) T2: twice passing of tractor, 3) T3: four time of passing tractor, and 4) T4: six time of passing heavy tractor. Utilize of all agricultural inputs (fertilizers, herbicides, etc.) has been identical for all treatments. Since rain-fed farming is the common method to cultivation of cereals in the study area, so no complementary irrigation was carried out in this period. In this study, after the measurement of the parameters, the data were analyzed by using SPSS 16.0 Software. LSD test was used for comparison of means.
Results and Discussion: The results showed that the different levels of soil compaction significantly increased soil bulk density. All the soil compaction treatments have caused a significant reduction on carbon and nitrogen sequestration in soil and wheat, soil aggregates stability and saturated soil moisture values. In the other hand the amount of soil pH and EC has increased significantly by increasing soil compaction levels that Indicates the negative effect of compaction on salinization of arable land.
Conclusion: The results of this study showed that the negative effects of soil compaction on soil physiochemical attributes are dependent on escalation of compaction. In total, even low levels of soil compaction (the treatment of two passes of a heavy tractor) is able to remarkably alter soil physiochemical attributes and thus carbon and nitrogen sequestration in soil and wheat. Induced changes in nitrogen and carbon sequestration levels are important for who concerned of global warming and climate change. Regarding the inability of deactivating soil compaction adverse effects in the deep soil layers of agricultural fields is the best way of handling and preventing soil compaction. Using these sluggish renewable resources should be consistence with land capability and its physical nature. This type of land use will result in sustainable development. From the remarks given here, it might be concluded that revising agricultural regimes and production methods is inevitable. On this ground, revisiting current agricultural systems should be considered and an urgent demand for state-of-the-art methods consistent with environmental objectives is being felt. To prevent soil compaction as much as possible, tractors and machinery traffic must be avoided to an acceptable level and this is of high priority during the time which soil is wet. It is more preferable to perform the operations with lighter machineries. As much as possible in a sophisticated agricultural plan these recommendations must be considered:
Increasing soil organic matter, leaving crop residue from the previous crop at the soil surface, using crops with deep-and-vertical-penetrating roots during crop rotation, tillage depth variation in different years, using super absorbent for better ventilation and reduces soil compaction, implementing no-tillage system to reduce traffic of farming machineries, maintaining plant residues at the soil surface, applying lacking nutrients to the soil, and subsoil operations to reduce the detrimental effects. As a field-based study, the results could be transferred to the local farmers. Authorities have to remove the obstacles to deliver the message to the farmers in order to enhance production and reach nation self-sufficiency.