جستجوی مقالات مرتبط با کلیدواژه "soil moisture" در نشریات گروه "اکولوژی"

Agriculture plays an essential role in providing food, and in order to achieve sustainability in the agricultural sector, resources must be used in the best possible way. In order to achieve the maximum possible yield, it is necessary for the crop plant to use the environmental factors, water, nutrients, light, and carbon dioxide, with the maximum possible efficiency. The maximum use of the required factors for growth is achieved only when the plant community exerts maximum pressure on these factors. In general, intercropping is one of the ways to achieve sustainable agriculture, with higher yields without increasing agricultural inputs, absorption, and environmental factors productivity. Researchers for the intercropping of corn and mung bean have reported that the mixed cultivation systems used environmental resources more effectively compared to the sole cropping of corn and mung bean. For this reason, nowadays, many plants, especially legumes, are cultivated in an intercropping form due to their ability to fix nitrogen. Due to the lack of resources regarding the effect of planting direction on plant yield, this study was conducted in order to evaluate resources and soil nutrients by changing the planting direction and replacing the intercropping system of the sunflower with cowpea.

This research was conducted in the field of the Agricultural Research Station of Zabol University during 2015-2016. The experiment was performed as a split-plot based on a randomized complete block design with three replications at the Research Farm of the Agricultural Research Institute of Zabol University.  The main factor was two levels of planting direction (North-South and East-West), and the secondary factor was intercropping system in five levels, including (100% pure sunflower), (100% pure cowpea ), (50% sunflower + 50% cowpea ) (25% cowpea  + 75% sunflower) and (75 % cowpea  + 25%sunflower) were considered. Data for studied traits were measured as follows: radiation, temperature, volumetric humidity, calcium, phosphorus, magnesium, potassium, and the land equality ratio.  Statistical analysis including, analysis of variance and mean comparisons (least significant difference (LSD) test at the 5% level), were applied to evaluated traits.

The maximum absorption of photosynthetically active radiation (PAR) was in the east-west cultivation direction (77.90%) compared to the north-south treatment, which was 24.6% more than the north-south direction. The analysis of variance indicated that the cultivation direction and intercropping systems on the amount of phosphorus in the soil after harvest were significant at 1% probability level. The comparison of means treatments showed that the amount of phosphorus in the soil in the direction of east-west cultivation was 15% higher compared to the direction of north-south cultivation.The highest amount of soil potassium was obtained in the east-west treatment and the intercropping system of 50% sunflower plus 50% cowpea (24.7 ppm). The lowest amount of soil potassium (16.15 ppm) was obtained in the treatment of east-west cultivation and the intercropping system of 75% sunflower plus 25% cowpea. The relative advantage of intercropping is expressed by the land equivalent ratio. The increase in the ratio of equal land per unit shows the relative usefulness of intercropping compared to sole cropping of each of the mixed components. The comparison of means of the intercropping system showed that among the treatments, the mixture of 75% sunflower plus 25% cowpea had the highest land equivalent ratio (2.54).

It seems that in order to maintain humidity make maximum use of limited water resources, and obtain high yield, the intercropping system of 75% sunflower plus 25% cowpea and planting direction the prevailing wind of the region (east-west) should be suitable for this region and regions with similar climate and windy conditions.

In order to investigate the effect of different mulches on weed biomass weight, yield and some physiological characteristics of onions, an experiment was conducted in a randomized complete block design with three replications at sample field in Jiroft area at 2019-2020 growing season. Experimental treatments included levels five inorganic mulch of black plastic, white plastic, organic mulch of wheat straw, weeding and control treatment. Traits such as plant height, bulb height, bulb diameter, neck diameter, bulb yield, TSS, bulb sulfur content, percentage of acid, soil temperature, soil moisture content and weed biomass weight were evaluated in three stages. The results showed that all the studied traits except TSS were significantly affected by different mulches. The highest bulb height (73.1 mm), bulb diameter (69 mm), neck diameter (13.3 mm), bulb yield (55707 kg/ha), The highest amount of sulfur was observed in the straw and stubble treatment, There was no significant difference with black mulch treatment. Three types of dominant weeds such as wild mustard (Sinapis arvensis L.), malva (Malva neglecta L.) and leek (Chenopodium album L.) were observed in the studied onion field. The highest and lowest weed biomass of weeds were obtained in the first and third stages of sampling in control and black mulch. The use of appropriate mulch was effective in reducing the number and biomass of weeds and producing optimal yield of onion. According to the research results, black mulch treatment is the best treatment to control weeds and produce optimal yield.

Considering the extensive cultivation of wheat in the drylands of Kermanshah province and the lack of proper management of plant residues by farmers, it is necessary to think of a solution for the proper management of residues and wheat cultivation. For this purpose, an experiment was conducted with the aim of investigating the effect of different tillage systems on soil physical characteristics and quantitative traits of different wheat cultivars in the drylands of Dalahoo region. A split-plot experiment was conducted in the form of a randomized complete block design with 3 replications. Tillage systems (conventional tillage, no-tillage, reduced tillage) were investigated as main plots and 26 wheat genotypes as secondary plots. Soil physical characteristics and wheat yield and yield components were investigated. The results showed the physical characteristics of the soil, the change of soil organic matter, and the yield and yield components of wheat significantly. They were affected by tillage systems, genotype, and interaction effect of tillage in genotype. The results showed that with increasing depth, soil temperature decreased and soil moisture increased. In no-till cultivation, the change of soil organic matter was less than other tillage systems. The highest amount of wheat grain yield (6658 kg/ha) was under the interaction effect of Mirzabey (Durum) genotype (genotype 24) in no-tillage system. Conservation tillage proves the importance of residues on the soil surface in maintaining moisture in drylands, and probably in Dalahoo areas, conservation tillage methods are better for improving yield.

Climatic variation particularly for participation is a constraint for the crops to reach their potential productivity under rainfed conditions. Therefore soil moisture preservation by means of tillage practices and improvement of soil physical criteria, particularly through enhancement of organic matter content is crucial. For this reason soil tillage must be managed in a proper way in order to fulfill this objective. Use of the right implements for this purpose under rainfed conditions together with retention of crop residue are practices most suitable for low rainfall environments. Tillage operation has a great impact on soil properties such as soil particle stability, soil aggregate and also soil water holding capacity. There are good evidences regarding yield improvement under rainfed conditions when implements such as chisel plow and sweep plow is used. Reduced tillage has been referred to as a proper practice under such conditions and degrees of no to minimum tillage have been proposed. These types of tillage combined with retention of crop residue which is referred to as conservation agriculture is being received more attention for the sake of soil conservation and moisture preservation. The purpose of the present study was to investigate these type of management for a rainfed wheat-fallow rotation.

In order to study the effect of different tillage practices in fallow-wheat rotation and retention of crop residue on soil properties such as bulk density, soil aggregate, porosity, particle stability and moisture holding capacity and also crop criteria including yield, above ground biomass of wheat and weed under rainfed conditions, an experiment was conducted for two years (2013-2014 and 2014-2015 growing seasons) in Shirvan region, Northeast of Iran. The layout of experiment was strip plots based on a randomized complete block design and three replications. Tillage systems and retention of crop residue were the experimental factors with four levels of tillage (chisel, sweep, moldboard and no tillage) and three levels of crop residue retention (7, 3.5 t.ha-1 and zero residue). Tisdal and Oades method used to determine the soil aggregates size distribution in dry and wet sieving conditions. To determine the soil bulk density, undisturbed samples were picked up from a depth of 0-10, and 10-20 cm and soil bulk density were determined after drying of soil in Oven for 48 hours at a temperature of 105°c. In order to evaluate the soil moisture at the end of the fallow year, sampling was done from each treatment in the depth of 0-20cm. During growth and after harvesting, the plant height, ear length, seed number per ear, thousand kernel weight, seed yield, and biological yield were determined.

Results showed that in general soil bulk density was higher at the depth of 0 to 10 cm compared with that at the depth of 0 to 10 cm for the experimental soil. Soil porosity followed a reserve trend of that of bulk density. Retention of crop residue caused a slower bulk density and a higher soil moisture content. Tillage with moldboard at different levels of crop residue retention caused lower weed biomass compared with other tillage operation. Soil practices size higher than 0.5 mm were respectively higher and lower with moldboard plow. Seed yield and also above ground biomass were higher with moldboard plow compared with the conservation tillage practices. Despite lots of reports about the prominence of conservation tillage systems in comparison with moldboard tillage, the reason for the prominence of moldboard plow in comparison with conservation tillage in this experiment can be attributed to better seedbed preparation in moldboard tillage. The other reason for seed yield increment in the treatment of moldboard tillage in comparison with other treatments can be the effective control of weed plants, especially Russian Knapweed.

Despite contradictory reports about the effect of moldboard tillage on wheat yield in comparison with conservation tillage, the results of this experiment showed the prominence of moldboard tillage in contrast with the sweep, chisel, and no-tillage for wheat production. Under rainfer conditions retention of crop residue together with minimum level of soil disturbance seems to be a proper practice. This has been evidenced elsewhere and is confirmed somehow in our experiment too. This is mostly related to enhancement of water holding capacity of the soil.

Water infiltration models are very helpful in predicting runoff in the slopes. The accuracy of the models depends on soil types and initial moisture conditions. This study was conducted to three soil textures (loam, sandy loam and sandy clay loam) with four initial soil moisture levels as a completely randomized design. The infiltration rate models consist of the Kostiakov, Kostiakov-Lewis, Horton, Soil Conservation Service of America, Green-Ampt and Philip were fitted to data and their accuracy were assessed using some statistical parameters. Results showed that soil infiltration rate is affected strongly by initial water content in the soils. The highest variation of infiltration rate was found in sandy loam especially in initial times of infiltration. There were obvious variations in final infiltration rate under different initial water content in the soils and the lowest and the highest variation was observed in sandy clay loam and loam , respectively. The Horton’s model was the best equation describing temporal variation of water infiltration in the sols under different initial water contents, so that itappeared the highest determination coefficient and the lowest values of the root mean squares error and the Akaike index. The Green- Ampt’s model appeared the most sensitivity to initial water content and was weakly fitted with observed data. Therefore, the Horton’s model can be used for predicting infiltration rate under different initial water contents in the soils.

Carbon sequestration is defined as the permanent gain of carbon by soil, plant or water. Soil as the largest terrestrial carbon pool plays an important role in the global carbon cycle. Due to the role of agricultural systems in CO2 emission, attention to the carbon cycle in agricultural systems is of prime importance. So, the interest in agricultural soils and plant biomass as a carbon sink and an operational mechanism for reducing the atmospheric CO2 level, is increasing. It is estimated that world’s crop-based agriculture occupies 1.7 billion hectares, which can store up to 170 Pg carbon. Thus, the aims of this study were to simulate the relationship between crop residue decomposition rate with carbon to nitrogen ration (C:N) (an index of residue quality) as well as soil moisture regimes (the most important factors in residue decomposition) and also estimation of the attainable carbon sequestration in irrigated systems of five major crops in Iran based on the simulated model. Residue decomposition rate of wheat, maize, rapeseed, cotton and soybean (with C:N ratios of 131, 69.7, 87.1, 57.8 and 95.9 , respectively)  in different soil moisture regimes (100, 60 and 30 percentage of field capacity) was studied in a 390-day incubation experiment. Study data was used for simulation of residue decomposition and relative decomposition rate was defined as a function of moisture (fm), C:N (fC:N) and temperature (ftemp). The simulated model was used to evaluate attainable carbon sequestration of the studied crops in five years from 2002-2003 to 2006-2007 based on yield, harvest index and shoot to root ratio in three scenarios of residue retention (100, 50 and 0 percentage of total residue produced) as well as three scenarios of soil moisture regimes of 100, 60 and 30 percentage of field capacity for different provinces of Iran. In this step, residue decomposition during one year after harvest was calculated using fm, fC:N and ft. The difference between proportions of the residue returned to the soil and decomposed residues were considered as un-decomposed residue which was multiplied by 0.45 to gain attainable carbon sequestration. Data of attainable carbon sequestration was analyzed as factorial experiment based on completely randomized design. Results indicated that higher C:N and therefore lower residue quality caused lower residue decomposition rate. This parameter was also decreased in soils with lower moisture. Effects of soil moisture on reside decomposition was more pronounced than residue quality. comparison of attainable carbon sequestration in Iran’s provinces revealed that in wheat cropping systems: Kermanshah and Sistan and Balouchestan, in maize: Qazvin and Southern Khorasan, in rapeseed: Isfahan and Boushehr, in cotton: Eastern Azarbaijan and Hormozgan and in soybean cropping system: Ardebil and Eastern Azarbaijan provinces had the highest and lowest attainable carbon sequestration, respectively. Attainable carbon sequestration in all crops was decreased with increasing soil moisture from 30 to 60 and 100% of FC and decreasing residue retention from 100 to 50 and 0 % of total crop residue production. Maize and soybean showed the highest and lowest capability of carbon sequestration, respectively. Results of the present study highlight the effects of environmental factors such as soil moisture as well as inherent properties of plant residues on residue decomposition. Climate and residue quality are the main determining factors of soil microorganisms activity and residue decomposition and therefore soil attainable carbon sequestration. Better soil moisture condition and temperature, also higher residue quality increases microorganisms activity resulting in more residue decomposition. Furthermore, plant biomass and residue management affects attainable carbon sequestration. Resultant of the mentioned factors determines attainable carbon sequestration in soils of agroecosystems. Regarding to the total carbon sequestration of afore-mentioned crops, Ardebil and Sistan and Balouchestan provinces showed the highest and lowest carbon sequestration, respectively.

Skid trails are the main routes for wood extraction and also the main source of runoff and sediment production in Forests. This research was conducted in Kuhmiyan forest of Golestan Province to determine infiltration, compaction, strength (resistance to penetration) and moisture content in three treatment including control (in the forest), wheel ruts and middle of skid trail were measured in three replications and three soil depth. The results showed  that total infiltration rate and infiltration at different time intervals, were significantly the highest. Compaction, strength and moisture content were also significantly different and the maximum values belonged to wheel ruts. Correlation results showed a negative linear relation with 90% R2  adjusted between infiltration- compaction and infiltration-strengths ,these two indexes could well be indicative of permeability changes. Some of Conservation strategies are: adding slash on skid trails to reduce compaction, limiting skidding operations to dry seasons, designing dips to reduce runoff on skid trails.

The current investigation was carried out in order to compare the different ratio combinations of intercropping vetch, barley regarding forage quantitative yield and soil physical properties. The study was conducted in Gachsaran dryland research station from 2010 for 3 growing seasons based on a randomized complete block design with three replications. The treatments included different intercropping combinations of vetch and barley: 75% + 25%, 50% + 50%, 25% + 75% and sole culture of each plant species. The results showed that the highest forage fresh yield, forage dry yield and grain yield were obtained from barley monoculture (17.2, 5.9 and 3.5 t.ha-1 , respectively) and 25% vetch + 75% barley (15.5, 4.9 and 2.5 t.ha-1, respectively). Maximum land equivalent ratio (LER) was achieved from 25% vetch + 75% barley intercropping treatment with 1.03 which exhibits a slight improvement in forage production compared with monoculture system. Intercropping ratios didn’t affect soil moisture content within soil 0-30 cm depth. Intercropping of barley and vetch improved soil bulk density within three depths of sampling (0-10, 10-20 and 20-30 cm) as soil bulk density after study decreased compared with before the start of experiment. The 10-20 cm layer of soil had the highest bulk density and intercropping treatments particularly with 75% barley + 25% vetch caused significant decline in bulk density in this layer compared with mono-culture (either barley or vetch) treatments. In general, intercropping barley and vetch with combination of 75%:25% is recommended for Gachsaran region due to the positive effect on soil bulk density in long term, producing a yield similar to barley monoculture and increasing variety in agricultural productions. .

The purpose of this research is to analyze the decrease of surface moisture and source of dusts in Hamoon-Hirmand Basin of Sistan and Baluchestan province. In order to achieve the objectives of this paper, WEAP software was used to simulate subsurface flow drops and then, by applying water resource management scenarios, the subsurface flow loss rate was simulated by 2031. Using the hierarchical analysis method, the best option among the scenarios was selected and the area under study under this scenario at the end of the year is 29 cm below the subsurface flow rate and the total unsecured amount for various criteria such as drinking, agriculture And the environment is equal to 804.183 million cubic meters. The wind speed in the study area is greater than the velocity threshold of the particles (more than 400 cm / s), so the area is capable of producing dust. The HYDRYS-1D model has been used to analyze the soil moisture content reduction in this paper. The obtained results indicate a decrease in soil moisture content in each year. It was concluded that the reduction of soil moisture content is closely related to the subsurface flow rate and the potential for dust

Drought is one of the main factors of ecological potential stress due to the wide extension of the time scale and impact space. The performance of regional drought monitoring using the meteorological indicators is a challenge due to spatial distribution constraints. In present study, 168 time series images including NDVI and LST indices were used. Integrating these two indices, VSWI was used to assess near-real-time and spatial-temporal spatial drought monitoring in Gavkhoni basin during 2003 to 2014. The SPI was assigned as the basis and the feedback of satellite and meteorological indices was assessed using Pearson correlation test. The results of the study of the relationships between the mean annual values of the VSWI and SPI indices during the same period showed a value of 0.578. In order to study the significance of the indices correlation, a nonparametric Spearman correlation test was added to the study. In addition, the results of the spatio-temporal pattern of the annual VSWI, indicating a severe long-term drought in the southeastern parts of the Zayandehrud dam and the entire Gavkhoni wetland area. The adaptation of this map to the meteorological drought map indicates the efficiency of integrating NDVI and LST satellite indices in drought monitoring.

Large areas in Iran which located in arid and semi-arid region are faced with serious water shortage. Because in these regions, from one side the precipitation and access to water resources are limited and from the other side atmospheric factors are intensively influence evaporation. In addition, evaporation from soil surface not only wastes water resources, but also may cause soil salinity (Homaee et al., 2002; Hillel, 1998). The objective of this study was to estimate evaporation from bare soil at presence of different water table levels. The rate of evaporation loss was also estimated, using the parametric model proposed by Zarei and Homaee based on Brooks and Corey’s retention curve.
For this purpose, the cumulative and instantaneous evaporation in a sandy loam soil was measured by weighting method three times a day. The proposed model of Zarei and Homaee was further tested against the collected experimental data. This retention-based model has been proposed to estimate evaporation from water falling table.
Results indicated that the maximum and minimum efficiency of model, obtained under 150 and 75 centimeters of water table depth, were 98 and 81 percent, respectively. The results showed that at water table depths less than one meter, the evaporation rate is increased. The results also indicated a reasonable agreement between the measured data and model outputs. The small difference between the measured and predicted values may be attributed to the moisture movement as vapor, soil shrinkage and errors in digital scale measurements. The predicted instantaneous evaporation rates provided better agreement with the experimental data as water table depths increased.
The parametric model of Zarei et al. (2010) provided a reasonable agreement with the experimentally measured evaporation data. Consequently, this model can be used to estimate the evaporation under similar climatic conditions.

Monitoring and evolution of drought is the first step in any drought management system. In this study, evaluation of a new indexa new method is provided to monitor the severity of drought with Remote Sensing Combined Drought Index (RCDI). The index is based on the fact that drought is a natural phenomenon caused by a combination of various factors such as a shortage in the amount of precipitation, less than the average long-term rainfall, temperature higher than normal and the properties of the soil moisture. The new index is a statistical index comparing the present hydrometeorological conditions with the long-term average characteristics in the same interest period within the year. Three data sources used in the RCDI index includes rainfall, temperature and vegetation data. In the present study, remote sensing data of TRMM and MODIS are used to provide the required data of RCDI index in central Iran for mapping the spatial distribution of drought over the period 2001-2004. Accuracy of the RCDI index based on satellite data carried out using the evaluation criteria of R and RMSE compared with soil moisture values based on monthly data of 50 synoptic stations in 95% confidence levels. The results of the evaluation criteria showed that drought severity index calculated by the RCDI index in accordance with soil moisture values had the significant correlation (0.61) and the lowest estimation error (1.98). Thus, a RCDI index could well use in drought early warning systems.

This study carried out in RCBD with 6 treatments and 3 replication in dry land agricultural research institute during 4 years (2003-2007). In automn tillage treatments and in spring sowing of seeds were completed. Treatments were: T1= Sweep in fall + planting by seed drill in spring, T2= Removing stubble in fall + direct planting by seed drill in spring, T3= Semi-moldboard plow in fall + disk harrow and planting by seed drill in spring, T4= Chisel plow in fall + disk harrow and planting by seed drill in spring, T5= Fertilizer and seed broadcasting by hand and moldboard plow in spring, T6= Chisel plow in fall + fertilizer and seed broadcasting by hand and disk harrow in spring. The results showed that wet and dry forage yields were different among treatments, T4 with 5393 and 3190 kg/ha had the highest forage yield and T5 with 4643 and 2646 kg/ha had the lowest forage yield. This trend was abserved in stubble and grain yield T4 with 3245 and 1121 kg/ha had highest yield and T5 with 2749 and 707 kg/ha had lowest yield. The effect of year on wet and dry forage and grain yields was significantly different (1%) but the intraction of year on treatments was not significant. soil moisture was differ among treatments. moistuer comparison in 3 soil depths showed that T4 treatment was better than other treatments and had 24. 90, 26. 67 and 28. 04 درصد soil moisture and T6 treatment had 18. 92, 19. 18 and 20. 87% soil moisture.