جستجوی مقالات مرتبط با کلیدواژه « رطوبت خاک » در نشریات گروه « زراعت »

Spreading hedgeparsley is a weed of wheat fields which thier seed bank is increasing in Kermanshah province. The aim of this study was to investigate the effect of time, burial depth, and seed shape in the field. This study was conducted as a factorial experiment in a completely randomized design with 3 replications. Both hairy and non-hairy forms of spreading hedgeparsley seeds were placed in different depths of storage (control), zero (soil surface), 5, 10, 20, and 40 cm of soil, and then seeds digged out from soil at 3, 6, 9, and 12 months burial time. The results showed that the effect of time, burial depth, and seed shape treatments on germination was significant in the field. The highest percentage of spreading hedgeparsley seed germination was observed in the first 3 months after burial. In general, the percentage of seed germination decreased by time. At a depth of 5 cm in the soil due to the favorable environmental conditions such as temperature, light and oxygen, the highest germination percentage was observed. Seed germination percentage decreased with increasing depth. The percentage of germination of spreading hedgeparsley seeds was higher than that of spinyseeds due to the level of contact of seeds with light, temperature and humidity.

As one of the most important crops in Khuzestan, Iran, forage maize production faces limitations such as deficincy of water resources in summer, low soil organic matter content, heavy soil texture and soil salinity, which can be resolved by appropriated nutrition management and planting method to reduce some of these problems. To improve soil fertility, integrated application of chemical and organic fertilizers is eco-friendly and economically sustainable. The integarated application of organic and biological fertilizers in combiation with chemical fertilizers is an important integrated plant nutrition management strategy for sustainable productivity and production in cropping systems.

To evaluate the physiological traits and yield of silage maize with with integrated application of nitrogen fertilizer and sugarcane residue compost and seed sowing method under drought stress conditions, a field experiment was carried out in split split plot layout in randomized complete block design with three replications in 2021 summer in Ramhormoz, Khuzestan province, Iran. Treatments included irrigation after 30% (non-stress), 50% (moderate stress) and 70% (severe stress) deplation of available soil water (main plots), fertilizer treatments included 100% of nitrogen fertilizer requirement; 75% nitrogen + 25% compost, 50% nitrogen + 50% compost, 25% nitrogen + 75% compost and 100% compost (sub plots) and sowing methods, top of beds and in furrows (sub-sub plots). Samples of fresh forage were used to determine the relative water content (RWC), dry matter content and the dry forage yield. The leaf greenness index (SPAD) was measured using a portable chlorophyll meter at the 50% flowering stage on the fully developed leaf. Forage quality traits were measured using near infrared spectroscopy (NIR).

The results showed that the highest values of SPAD, chlorophyll a, chlorophyll b, RWC and cell membrane stability were obtained in 100% chemical fertilizer treatment under well irrigated condition. However, under modeate and severe drought stress conditions, combination of chemical and organic treatments with the 50% nitrogen and 50% compost of sugarcane residues had higher values. The maximum dry forage yield was obtained under well irrigated treatment, 100% chemical fertilizer and in furrow seed sowing. However, under moderate and severe stress conditions, the highest dry matter yield were obtained in integrated fertilizer application treatments and in furrow sowing. The lowest dry forage yiled was obtained in 100% organic fertilizer treatment and sowing on top of the bed. Under mild and even severe stress conditions, in furrow sowing method in comparison with the top of the bed, the effect of drought stress was mitigated, mainly due to better and longer condition for uptake of moisture and nutrients available for maize plants.

According to the results, it can be concluded that in furrow sowing method, better moisture could be preserved for longer time and optimal application of sugarcane compost as an organic input can improve the physical, chemical and biological properties of the soil, thus providing nutrients, especially nitrogen, and their slow release during the plant growth period which in turn may reduce the negative effect of drought stress and improve growth and yield of forage maize under the conditions of Khuzestan province.

In order to investigate the effect of different methods, levels and salinity of irrigation water ‎on cotton, a two-year experiment was carried out‏ ‏at the Hashemabad Cotton Research Station ‎in Gorgan city.‎‏ ‏The experiment was performed in a randomized complete block design with ‎three replications. So, four salinity levels of irrigation water (1, 4, 8, 12 dS/m) as main factors, ‎four different levels of irrigation water‏ ‏‎(33, 66, 100 and 133% of water requirements) was ‎considered as the first factor and two irrigation methods (complete irrigation and Partial Root ‎Dry irrigation/PRD) were considered as the second factor. The results showed that compared ‎to control, cotton yield decreased by 41%, 22% and 19%, in 12, 8 and 4 dS/m salinity, ‎respectively. The water use efficiency was reduced at rate of 30, 18 and 16 percent. As the ‎salinity of irrigation water increased, the average weight of the boll, fiber index, earliness and ‎the fibers decreased significantly. As the moisture level increased, the yield of cotton, average ‎boll weight, the number of seed in a boll and the number of bolls increased significantly. In ‎additional the water use efficiency of the 133, 100 and 66% treatments compared to 33 ‎percent decreased by 32, 16 and 10 percent,‎‏ ‏respectively. The cotton yield under133, 100 and ‎‎66% treatments decreased by 32%, 16% and 10%, respectively, compared to the 33% of the ‎water requirement. Although PRD reduced crop yields by 15 percent compared to full ‎irrigation treatment, but the water use efficiency increased by 36%.‎‎‎‎‎‎

In this study, the Aquacrop model was evaluated to predict the crop yield and the water use efficiency of tomato in climatic conditions Kahriz region, and use mulch cover was modeling. The research was carried out at split plot factorial experiment based on randomized design. The factors of between-row spacing (100 and 120cm), in-row spacing (30 and 40cm) and black plastic were studied. The treatment of black plastic were: full ridge and half furrow were covered by mulch; full furrow and half ridge were covered by mulch and control (no mulch). Every plot was irrigated separately. The model was calibrated by the use of first year’s data, and as a result on the base of R2 (0.99) and NRMSE (0.19). Efficiency parameters, it is obvious that Aquacrop appropriately simulates the crop yield, WUE and soil water content of the root zone for tomato under different planting densities and three types of mulch.

Soil is one of the most important components of production, food security, self-sufficiency and national economy. Soil of semi-arid regions, which most of Iran's agricultural lands are located in these areas, are poor in terms of organic matter. The soil tillage operations are carried out by means of moldboard plow and removal of plant residue in most of the agricultural systems. This operation, called conventional tillage, requires not only high energy but also damages to soil physical properties and erosion in the long-term. Conventional tillage does not provide good environmental conditions to maintain moisture in the soil due to the impossibility of managing plant residue in the soil surface. In addition this tillage increases the evaporation and losses of soil water content and reduces the soil organic carbon as a result conventional tillage reduces the physical, chemical and biological characteristics of the soil. The objective of this study was investigation of effect of conventional and reduced tillage systems and management of tomato residue on soil water content, yield and yield components of wheat.

The experiment was conducted as split plot based on randomized complete block design with three replications at the Agricultural Research Station, Ferdowsi University of Mashhad, during growth season 2017-18. Tillage system (in two levels i.e. conventional and minimum tillage) and tomato residue retention (0, 30 and 60%) were in main plots and sub plots, respectively. The sowing date was 11th November in 2017.Sampling was done at harvest time and included plant height, spike number.m-2, spike length, grain number per spike, 1000 grain weight, grain yield, biological yield and harvest index. During the growing season, soil water content in 0-20 and 20-40 cm depth was measured by the soil moisture meter (PMS-714 model) two days after irrigation. Data were analyzed with R software; obtained averages compared with Duncan’s multiple range test at the 5% probability level.

The results showed that the effect of tillage system was significant on soil water content in 0-20 cm depth two days after forth irrigation, soil water content in 20-40 cm two days after fifth, sixth and seventh irrigation, spike number.m-2, grain number per spike, grain and biological yield. Maximum of this traits were obtained in reduced tillage due to increased soil nutrition, improved physical condition of the soil and soil water status. However, the effect of management of tomato residue on any of the studied traits was not significant. This could be due to reducing microbial activity, in complete decomposition of plant residues and reducing available nitrogen.
The interaction effect between tillage system and tomato residue was significant on soil water content in 0-20 and 20-40 cm depth two days after forth and third irrigation, respectively, grain number per spike, 1000 grain weight and grain yield. Reduced tillage and 60% of tomato residue showed that maximum of soil water content and 1000 grain weight (38.4 g).Maximum of grain number per spike (61.9) and grain yield (7120. 7 kg.ha-1) were obtained in treatment of reduced tillage and 30% of tomato residue.
Conclusions  
The results of this study indicate that in order to achieve maximum grain yield and less damage to the physical and chemical properties of soil, the implementation of reduced tillage and maintenance of 30% of tomato residue is recommended in the studied area. In general, due to climate change and water resource constraints in the country, conservation tillage and residue management practices are a good way to maintain resources and sustainability.

Potassium fertilizers may increase soybean yield and potassium concentration in leaves. Surfactants are surface-active agents, with simultaneous hydro and lipophilic molecular structures and specific physical and chemical attributes such as surface tension. Surfactants may enhance potassium exchange between soil colloids and the solution through enhanced dispersion of water, which increases available potassium for plant use and yield specially in soils with high specific surface area and limited potassium exchange. The objective in this research was evaluating the effect of a surfactant and potassium fertilizer on soybean yield components with water tension.

This study were carried out in Gorgan University of Agricultural Sciences and Natural Resources estate using split plot in completely randomized block design in four replications. Treatments were two levels of potassium fertilizer (108.3 kg ha-1K equivalent to 208 kg ha-1 potassium chloride) and no fertilizer use as main plots and four levels of 2-1 propandiol surfactant (0, 2, 4 and 8 l ha-1) as subplots. Soil water contents at 0-8 and 8-16 cm depths measured at four occasions during growing season (namely 143, 173 and 201 days after planting). Mechanical resistance at 0-5 cm depth was also measured in six occasions (namely 49, 69, 89, 109, 129 and 151 days after planting) using a pocket penetrometer. Yield components obtained at harvest.

Maximum soil water content obtained by four liter per hectare surfactant and soil water content diminished as the rate of application decreased. Higher rates of applications lowered mechanical resistance at all stages of applications, which could be due to higher water content in fine pores. Potassium application increased final soybean yield and yield components significantly but surfactant affected biological yield only (at 5% significance level). Surfactant application without potassium fertilizer was ineffective on yield production, but increased yield in combination with potassium fertilizer. Surfactant reduces surface tension, which allows free dispersion of water and potassium in fine pores, which enter soil solution where roots thrive. More soil water with surfactant reduces soil mechanical resistance and increases root growth and potassium uptake by fertilizer application. In the Study of interactions between the surfactants and potassium fertilizer, the potassium fertilizer in combination with 4 liter per hectare surfactant produced maximum soybean yield, hundred seeds weight, seed number per shell, branch number, harvest index, seed number per unit surface, biological yield and plant number per unit surface. Potassium fertilizer in combination with 8 liter per hectare surfactant produced maximum plant height, node number in main stem and number of shells per branch.

By decreasing surface tension, surfactant improves dispersion of water within soil pores, which results in more surface-soil water retention and content. More soil water content diminishes mechanical resistance against root growth and increases soybean yield. Potassium fertilizer application in combination with 4 liter per hectare surfactant increased soybean yield significantly due possibly to more plant potassium uptake.

Environmental conditions such as soil moisture have a significant effect on herbicides efficacy. In order to evaluate the effect of Othello herbicide in different soil moisture conditions on wild mustard and wheat, a greenhouse experiment was conducted as split plot based on randomized complete block design with three replications. Three levels of soil moisture including field capacity, 75% field capacity and 50% field capacity, and 0, 33, 66, 99, 132 and 165 grams of active ingredient of Mesosulfuron + Iodosulfuron + Diflufenican per hectare were the experimental treatments. Results showed that the concentration required to reduce the dry matter content of wild mustard by 50% in the field capacity was 71. 57 g. a. i /ha of herbicide, while in 75% and 50% of the field capacity, it was increased to 88. 69 and 112. 11 g of active ingredient per hectare, respectively. The required concentration to reduce 50% of dry weight of wheat in the field capacity was 86. 85 g. a. i / ha, while it reached to 102. 5 and 73. 95 g. a. i /ha at75% and 50% moisture content, , respectively. The results of the data showed that at 50% moisture content of the field capacity, lower concentrations of this herbicide would also have adverse effects on wheat.

Effect of conservation agriculture on soil properties and sesame yield in the sesame-wheat rotation

Conservation tillage methods offer considerable advantages compared to the conventional tillage; therefore, these tillage methods are widely disseminated throughout the world. Conservation tillage affects soil properties, environment, and crop yield. Results of research studies show that conservation tillage saves water in wheat production compared to the conventional tillage (Erenstein & Laxmi, 2008). Conservation tillage also increases soil organic carbon (Madejon et al., 2009) and sesame yield (Uzun et al., 2012) as compared to the conventional tillage. This study was performed to evaluate the effects of conservation tillage practices on soil properties and sesame yield in sesame-wheat crop rotation under hot climatic condition of Fars province.

This study was conducted using a randomized complete block experimental design with five treatments and four replications in Fars province from 2010 to 2013. Treatments included; 1) reduced tillage (T1), 2) wheat and sesame direct seeding (T2), 3) sesame direct seeding for four years, wheat direct seeding for the first two years and the fourth year, and conventional planting in the third year (T3), 4) wheat direct seeding for four years, sesame direct seeding for the first two years and the fourth year, and conventional planting in the third year (T4), and 5) conventional tillage (T5). Soil bulk density was measured at two soil depths including 0 to 10 and 10 to 20 cm using core samplers. Soil moisture content was measured using TDR at the soil depth of 0 to 20 cm. Soil water cumulative infiltration and infiltration rate were determined using double ring method. Soil organic carbon was measured by analyzing mixed soil samples in laboratory, and carbon dioxide emission from the soil was determined in the field using Anderson method. Sesame yield was calculated by harvesting 10 m2 area of each experimental plot. Collected data were analyzed using SAS software and Duncan's multiple range tests was used to compare the treatments means.

Results of this research indicated that tillage methods had significant effect on soil moisture content so that the maximum soil moisture content was obtained from the no-till method and the conventional tillage gave the lowest soil moisture content. Tillage methods had no significant effect on soil bulk density; therefore, conservation tillage methods did not considerably increase soil compaction. Results also showed that soil cumulative infiltration and infiltration rate were affected by tillage methods in such a way that conservation tillage practices decreased soil infiltration rate compared to the conventional tillage. Conservation tillage methods also increased soil organic carbon and decreased carbon dioxide emission from the soil as compared to the conventional tillage. Meanwhile, conservation tillage methods did not significantly decrease sesame yield relative to the conventional tillage.

Results showed that conservation tillage methods increased soil moisture retention (at most 50%) and soil organic carbon (138%) relative to the conventional tillage. Soil bulk density was not affected by tillage methods, while conservation tillage methods reduced soil water cumulative infiltration and infiltration rate compared to the conventional tillage (33%). Conservation tillage methods reduced carbon dioxide emission from the soil by 19%. Meanwhile, conservation tillage methods did not reduce sesame yield compared to conventional methods.
Acknowledgments: The authors would like to acknowledge the financial support extended by the Agriculture Organization of Fars province and Agricultural Engineering Research Institute

To study the effects of wheat and canola residue management and tillage methods on maize yield and some soil properties, two separate experiments were carried out over three years (2009-2011) in Experimental Research Station of Orzoiyeh in Kerman, Iran. In each experiment randomized complete block design arranged in a split plot was used with four replications. Tillage methods (conventional and minimum tillage) were compared in the main plots and crop residue (residue rentention, residue removal and residue burning) were compared in the sub plots. In maize planted under canola bed, in conventional tillage, grain yield (14.4%) and plant height (7%) was more than minimum tillage. In maize planted under wheat bed, grain yield of maize was higher in conventinal tillage in the first and second years, but there was not any significant difference between two tillage methods in the third year. In comparison between wheat residue treatments, residues retention had the highest maize grain yield. The moisture content stored in the soil was highest in treatment of minimum tillage along with residue retention of wheat. In both experiments, residue rentention increased significantly soil organic matter and residue burning increased soil phosphorus and potassium. Grain protein of maize was higher in minimum tillage than conventional tillage, but crop residue management has not significant effect on grain protein content. Based on the results of this study, residue retention in soil can be recommended, but to determine minimum tillage positive effects in soil, long term experiments should carried out.

Shortage of water in arid and semiarid regions of the world can reduce growth and production of medicinal and aromatic plants, especially Mentha species. In order to evaluate response of mint species to water deficit stress, an experiment was carried out using a completely factorial-randomized design with five replications at College of Agriculturae, Ferdowsi University of Mashhad, Iran. The factors studied included three mint species (peppermint ‘Mentha×piperita’, wildmint ‘Mentha longifolia’, spearmint ‘Mentha spicata’) that were exposed to four levels of irrigation treatments (control (100%), 80%, 60% and 40% of field capacity (FC)). in this study in 100% of FC spearmint’ green area was 50% more than 80% of FC, while in wildmint and peppermint mentioned parameter in control treatment were 2.5 and 2 times more than 80% of FC, respectively. However no difference observed between 100 and 80% of FC on aboveground to underground dry matter ratio in spearmint, but this parameter in control treatment of wildmint and peppermint were 50% more than 80% of FC. Results showed that growth of all three species were significantly decreased when soil moisture reduced to lower than 100 of FC, but peppermint and wildmint were more sensitive than spearmint to depletion of soil water during growing season.

In this experiment the requisiteness of mulch application on increment of yield and photosynthesis nitrogen and water use efficiency of almond were investigated. Experiment was conducted with five treatment in a Randomized Complete Block Design (RCBD) with three replication and four trees per each plot in Dezhcord County in Eghlid region in two years. Experimental treatments consist of - Without mulch (ctrl.) - Inorganic Pamis with 2 cm thickness - Organic almond shredded wood mulch - Glycyrrhiza root waste mulch - Wheat straw mulch, each of them on tree overcast (under tree cover) with 10 cm thickness. The experiment was carried out on 60 uniform fifteen years almond trees. Results showed that the application of different kind of mulch caused an improvement in growth, photosynthesis nitrogen and water use efficiency in almond in rain fed condition. The highest amount of yield belonged to wheat straw mulch. Mulch application caused an increment in stomata conduction, transpiration and photosynthesis water use efficiency. Organic mulch had the best significantly increased the photosynthesis water use efficiency in almond. The highest pure economical profitability belong to wheat straw mulch, almond shredded wood, Glycyrrhiza root waste and inorganic Pamis mulch under tree canopy, respectively.

In order to study the effect of zeolite super absorbent and manganese, on morpho-physiological traits of rapeseed cultivars in different irrigation treatment, an experiment was performed during two years of 2012-13 and 2013-14, as factorial split plot design on the base of completely randomized block design with three replicates in research farm of Shahryar. Irrigation factor was included three levels, irrigation on the base of 40, 60 and 80 % discharge of irrigation, zeolite factor was included two levels of zero and 15 (ton/ha), manganese factor (manganese sulfate) was included two levels of 0 and 3(g/1000), as factorial were set in the main plots and cultivar factor in four levels including SLM046, Talayeh, Modena and Opera were set in subsidiary plots. Results indicated that applying zeolite in the soil and foliar manganese and increasing the irrigation of the soil, lead to increase the grain yield (6324 kg.ha-1) and seed oil contect (46.5 %). Maximum amount of seed yield in normal irrigation was achieved by application of zeolite in the soil and foliar manganese. Applying manganese and zeolite decreases the amount of seed glucosinolate in different irrigation treatments. Maximum amount of the seed glucosinolate was achieved in normal irrigation condition (16.5 mg/g) by Opera cultivar. With the respect to the low yield in arid and semiarid areas , it is recommended that due to increasing the yield, mineral zeolite in the soil and foliar manganese in different cultivars be used in order to increasing efficiency of the irrigation and yield.

Evapotranspiration is one of the most important elements of hydrological cycle which is required for water resource management and design of irrigation systems. Crop evapotranspiration (ETc) can be measured by the Lysimeter using water balance equation. It also can be estimated by multiplying reference evapotranspiration (ETo) and crop coefficient (Kc). Considering the importance of this parameter, numerous studies have been performed to determine the Kc of major crops in each region. Lentil is one of the legumes which is cultivated mainly in Lorestan province. Although this crop is the second in terms of the area under cultivation among the legumes in the country, the water requirement and crop coefficients of this crop is not determined in Lorestan province yet. The main purpose of the current study is to determinate lentil water requirement and its Kc in Khorram Abad.
A lysimetric experiment was conducted during the lentil growth season in 2013 at the research farm of agricultural faculty, Khorram Abad, Lorestan University. The farm is located in a cold semi-arid climate. Physical and chemical properties of the soil in the lysimeters were determined in the laboratory. The average of soil moisture content in the lysimeter at the field capacity and permanent wilting point was determined as 34.4 and 24.8 volumetric percentage respectively. In this study, lentil (Gachsaran cultivar) and grass were cultivated each on four micro drainable lysimeter with the diameter of 48 cm and height of 80 cm. Maximum allowable depletion (MAD) of soil moisture was considered as 30% to ensure that crops are not faced with water stress. Length of the crop growth stages (initial, development, mid-season and late-season) was determined by daily observation of the field and measuring crop canopy. Lentil and grass evapotranspiration was determined using water balance method. The evapotranspiration from grass was considered as reference evapotranspiration (ETo). The measured values of ETo and lentil evapotranspiration was compared with the calculated values by CROPWAT, REF-ET and AGWAT (Basis of national document of water) packages. Crop coefficient (Kc) was calculated as the ratio of lentil evapotranspiration over ETo. Average of Kc for each stage was also calculated and compared with literature.
The average of reference crop evapotranspiration (ETo) was increasing thorough the growth period of lentil from 3.7 to 8.6 mm.day-1. This was due to increasing of sunshine hours and air temperature during that period. Total amount of lentil and grass evapotranspiration during the growing period of lentil was determined as 476 and 568 mm respectively. Total amount of calculated ETo in this period by CROPWAT, REF-ET and AGWAT packages was 551, 566 and 340 mm respectively. Results indicated that calculated values of ETo by CROPWAT and REF-ET is almost equals to measured ETo. However, AGWAT also uses Penman-Monteith equation but its results were far from the measured values of ETo because of differences in weather data. Results also indicated that lentil evapotranspiration was low at the initial stage, increased during the development stage and decreased during the late season. The maximum crop evapotranspiration of 88.46 mm per decade was measured at the period of 16-25 May 2013. Measured lentil evapotranspiration in the current study was higher than values calculated by AGWAT software package for this region. Lengths of initial, development, mid-season and late-season stages were determined as 19, 20, 33 and 24 days respectively. The average of lentil crop coefficient for initial, development, mid-season and late-season stages was calculated as 0.45, 0.89, 1.19 and 0.56 respectively. Calculated Kc values in this study were compared with the values of Kc in FAO 56 report and AGWAT. Calculated Kc at initial and mid stages (0.45 and 1.19 respectively) were close to values reported in FAO 56 (0.4 and 1.1 respectively) but far from AGWAT (0.15 and 1.05 respectively). In general, calculated crop coefficients in the current study were higher than the values presented in FAO 56 and AGWAT package software. Measured values of lentil evapotranspiration were higher than values reported in AGWAT. The reason was underestimation of ETO by AGWAT and lower values of Kc for lentil.
As there was no measurement of lentil evapotranspiration and crop coefficient, the results of current study can be used as a base for further studies about this issue in the region. Comparison of measured values of ETo and lentil crop evapotranspiration with the values calculated by AGWAT package indicated the under estimation of both parameters by AGWAT. However, it is recommended to do more studies on this subject but the results of current study can be used to determine lentil evapotranspiration instead of values reported in AGWAT and national documents of water for Lorestan province.

In order to study the effect of conservation tillage on optimum usage of fuel and precipitation, this research was conducted in wheat-sunflower rotation in shahrood for 4 years. The experimental design was RCBD with 5 replications and 4 treatments (direct seeding (NT), reduced tillage (RT), conventional sowing with and without residue gathering (CT1 and CT2)). Results showed, Soil inversion difference was significant among the treatments (p<0.01). Maximum and minimum of Soil inversion related to CT and NT, respectively. In first year, Soil moisture content difference in various depths wasn’t significant among the treatments. Wheat yield difference was significant among the treatments (p<0.05). Maximum and minimum of wheat yield related to CT and NT, respectively. In 4th year, Soil moisture content difference in 5-20 cm was significant among the treatments (p<0.05). Maximum and minimum of Soil moisture related to NT and CT, respectively. Although wheat yield difference wasn’t significant among the treatments, but Maximum and minimum of yield difference related to RT and CT, respectively. Maximum and minimum of fuel consumption and operation time, related to CT and NT, respectively. Maximum and minimum of fuel consumption productivity, related to NT and CT, respectively. Regard to crop yield and fuel consumption productivity, In order to Soil moisture maintain and optimum usage of fuel in rain-fed conditions, it may be recommended that moldboard plough can be replaced by conservation tillage methods (reduced tillage & direct seeding).

In this study, the effects of four types of mulch including wood chips, municipal compost, sawdust and gravel in three different thicknesses on temperature soil, moisture and growth characteristics of two cultivars of Tagetes (Tagetes patella var Durango Bee and Tagetes erecta var Antigua) were examined in Mashhad area with semi-arid climate. The research was conducted as a split plot based on a completely random block design with four replications. Treatments included control (no mulching) and four types of mulch including wood chips, municipal compost, sawdust and gravel in three thickness levels (4, 8 and 12 cm). During the study, soil moisture and temperature, total flower number, fresh and dry weight of plant, plant height and fresh weight of root were measured. Sawdust mulch with 12 cm thickness had the highest soil moisture (23.62%) and lowest soil temperature (25.01ºC), and led to greater increases in growth characteristics of the two cultivars. In both cultivars, increasing of mulch thickness led to the increased rate of growth. The Antigua cultivar showed a better vegetative growth, smaller flower number, and larger flowers in comparison with Durango Bee cultivar. All mulch types were significantly different from control. Overall, in both cultivars the highest and smallest growth taits were detected in sawdust and control, respectively. It seems that sawdust by preserving soil moisture and reducing drought stress out performs the other mulches in dry and semi-arid areas.

To study the effect of soil moisture variation on growth and steviol glycosides contents in Stevia (Stevia rebaudiana B)، a potexperiment based on a randomized complete design with four treatments and three replications were conducted in a greenhouse of Agricultural Biotechnology Research Institute of Iran (central region، Isfahan)، in 2012. Experimental treatments applied as a combination of visual symptom appearance in plant (normal to severe wilting) and soil moisture. So، treatments irrigated in 19. 1، 15. 1، 11. 9 and 9. 1% of soil moisture content (w/w) that are created in greenhouse situation with irrigation of 3، 6، 9 and 12 days interval، respectively. Results showed that soil moisture reduction up to 9 days irrigation interval had no effect on plant height and leaf dry weight، but plant growth significantly reduced in 12 days irrigation period. Maximum of harvest index obtained in 6 days irrigation period (51. 36%). Soil moisture reduction caused significant increment in stevioside and dulcoside A، but not affected the rebaudioside types (A، F and C). Total steviol glycosides increased with the soil moisture reduction and plant grown with 3 days irrigation interval had minimum steviol glycosides. Stevioside was highest in steviol glycosides in all treatments. Plants grown under 6 days irrigation interval had the maximum of steviol sugar yield. Totally، the results of this experiment showed that leaf dry weight decreased with decline of soil moisture content (below 11. 9 w/w)، but steviol glycosides content had significant increment. The highest of harvest index and steviol sugar yield were obtained in the 6 days irrigation interval. Although، steviol glycosides content increased with the soil moisture reduction، it means that intensify of drought stress more than 6 days irrigation interval (reduction of soil moisture content below the 15. 1 w/w) caused downfall of Stevia yield due to significant reduction of leaf yield and steviol sugar yield in severity of drought stress.

Using mulch to decrease and optimize water use, increase yield and fruit quality is known as a practical method. For this purpose, a split-factorial experiment based on complete block design with three replications on two melon cultivars was conducted in Torbat-e-Jam, Iran. Interval irrigation treatments in three levels (six, eight and 10 days) were considered as main plot and mulch (rice straw and paddy, plastic and no mulch) and cultivar (Khatooni and Ghasri) were considered as sub plots in a factorial design. Results showed that there was a significant difference between plastic mulch and the control and also between interval irrigation treatments for yield, sugar percentage, resistance to damping off and spider mite, leaf area and soil moisture. The largest leaf area and soil moisture was observed with plastic mulch. The largest contamination to spider mite and damping off were occurred using straw plus paddy rice mulch. Plastic mulch increased the sugar percentage of both cultivars as well. Plastic mulch for six day interval irrigation increased yield and fruit quality through increased yield and fruit quality to increase for more than eight day interval irrigation. Regarding the advantages of plastic mulch for reduction of water use and improvement of yield and fruit quality, using plastic mulches is recommended for dry lands.

In order to study the effects of soil solarization on weed control, an experiment with factorial arrangement in a randomized complete block design with four replications was conducted in a fallow farm in Daregaz in 2008. Factors included solarization duration (0, 2, 4 and 6 weeks) and soil moisture content (dry and moist). Soil seed bank was sampled (in two depth, 0-10 and 10-20 cm) prior to the experiment and immediately after applying treatments, and germination percentage of weed species were determined. Results of this study showed that seed germination percentage in 10 cm soil depth was influenced by soil moisture and solarization and their interactions, while in 20 cm soil depth only solarization period affected the weed seed germination. Germination percentage in moist soil was less than that in dry soil. Seed germination percentage declined more by increasing solarization duration, so that the greatest decline was obtained after 6 weeks solarization. Solarization decreased germination percentage in moist soil more than that in dry soil. Overall, the results of this experiment indicated that solarization of moist soil for 6 weeks was the most effective treatment in controlling common lambsquatres (Chenopodium album), common purslane (Portulaca oleracea), redroot pigweed (Amaranthus retroflexus), and wild mustard (Sinapis arvensis), while solarization of dry soil for 2 weeks was the least effective treatment for weed control.

In order to evaluate the effects of conventional, mechanized planting and direct drilling on soil moisture and grain yield of chickpea, this experiment was carried out in RCBD with 4 treatments and 4 replications at Maragheh Dryland Agricultural Research Institute. Field studies were conducted on a clay loam (fine mixed, mesic, veritc calcixerepts) soil on wheat stubble for 3 years (1995-1998). Results showed that there was significant difference in soil moisture content of treatments after planting and before harvesting times. Soil moisture content in direct drilling, after planting and before harvest were 34.75% and 16.25%, respectively. Direct drilling stored soil moisture better than other treatments. The results of combine analysis showed that there was a significant difference in yield in different treatments. Direct drilling and mechanized planting methods produced higher crop seed yield by 891 and 811 kgha-1 respectively. Conventional planting methods (broad casting and covering by diskharrow, broad casting and covering by mould board plow) had the lowest yields (627 and 555 kgha-1).