جستجوی مقالات مرتبط با کلیدواژه "irrigated land" در نشریات گروه "آب و خاک"

Considering the limitation of water resources and the need to increase water productivity in the production of agricultural products, the development of new irrigation systems has been one of the most important policies and activities of the agricultural water sector in recent decades. The purpose of this research is to quantitatively investigate the development of pressurized irrigation development in Iran and compare it with other countries and regions of the world using the pressurized irrigation development index, and finally the estimation of the optimal and expected level of its development for the country. According to the results, the PDI index until the end of the sixth development program (2020) is 21.4%, which is low compared to other 23 selected countries. Using the multivariable correlation method between the values of the variables affecting water management such as per capita withdrawal, the share of withdrawal from water resources in the agricultural sector, the area of irrigated lands, and the PDI index of 14 selected countries and applying values like for the Iran country, the desired and expected level of pressurized irrigation in the country was estimated at 49.2%. In other words, in the coming years it is possible to reduce the negative and undesirable effects of the unbalanced development of modern systems on water resources and the environment, and prevent the occurrence of the phenomenon of "rebound effect", in a favorable and potential way, up to half of the irrigated lands in the country should be equipped with pressurized irrigation systems. Meanwhile, according to the latest statistics, until the beginnings of 2023, the PDI has reached to 30% (2.9 million hectares). Therefore, there is still room for further development in terms of the necessary arrangements and under the condition of creating infrastructures, and necessary control rules and regulations by the related organizations.

Soil infiltration rate is the major soil hydraulic property which can be affected by the soil physical characteristics and management practices. The use of land can affect various soil properties such as physical and hydraulic properties. Differences of the hydraulic soil characteristics such as infiltration rate in various land uses can affect their potential to runoff production as well as soil loss in the catchment. The knowledge of the physical and hydraulic characteristics of various land uses can help to better management of soil and water in the catchment. It is very essential in the semi-arid catchments where vegetation cover is generally poor, the soils are often instable against erosive factors especially when the rainfalls are consecutive and intensive. Therefore, this study was conducted to investigate the soil physical and hydraulic characteristics in the TahamChai catchment, in a semi-arid region, NW Zanjan. Various land uses consist of pastures, rainfed and irrigated lands can be observed in the catchment, which cover about 62%, 33%, and 5% of the catchment area, respectively. The pastures have been covered with poor vegetation and are intensively exhausted by over-grazing. Rainfed lands are mostly under winter wheat cultivation. Soil erosion and sedimentation were the major environmental problem in this catchment.
The maps of land use and slope gradient were provided for study area. A total of 20 sites were selected based on the surface area of each land use in the catchment located between 34 46-36 53 N latitudes and 48 17-48 37 E longitudes. The study area consisted of ten sites in the pasture, seven sites in the rainfed and three sites in the irrigated lands. The geographical positions of study sites were determined by a global positing system (GPS). Soil infiltration rates were measured by double rings method at three replications in each site. Variation of soil infiltration rate was determined for each land use. Soil samples were collected at three replications from each site to determine other physicochemical soil properties. Particle size distribution, bulk density, saturation percentage, aggregate mean weight diameter, organic matter, and equivalent calcium carbonate were determined using standard methods in the lab. Mean comparisons of infiltration rate along with other physicochemical soil properties among the land uses were done using the Duncan's parametric method. The Pearson’s correlation coefficients were used to determine the relationships between soil properties and soil infiltration rate.
Based on the results, no significant difference was observed between the land uses in particle size distribution. Soil infiltration rate showed different patterns among the land uses, so that significant difference was observed among them (p Pastures with poor vegetation cover appeared the lowest soil infiltration capacity as compared to other land uses in the catchment. Decreasing soil infiltration rate was associated with increasing bulk density in the area. It seems that overgrazing in the pastures increases soil bulk density and leads to decline the soil organic matter content as well as soil aggregation and aggregate stability. According to the results, pastures have the highest potential to runoff production and soil erosion rather than the other land uses (rainfed lands and irrigated lands). Therefore, maintaining vegetation cover and preventing over-grazing in the catchment is recommended to increase soil organic matter content and decrease soil compaction. These practices improve the hydraulic soil characteristics especially infiltration rate and in consequence decrease the catchment potential to runoff production and soil erosion.