Iran Agricultural Research
Volume:39 Issue: 1, Winter and Spring 2020

In the present study, some nutritional imbalances, specific ion toxicity and yield-ion concentration relationships in maize under water, nitrogen (N) and salinity stresses were assessed. Effect of different levels of irrigation water (I1=1.0ETc+0.25ETc as leaching, I2 =0.75I1 and I3 =0.5I1) as main plot, salinity of irrigation water (S1=0.6, S2= 2.0 and S3=4.0 dS m-1) as sub-plot and N fertilizer rates (N1=0, N2=150 and N3=300 kg N ha-1) as sub-sub-plot on maize (cv SC 704) were investigated in a split-split-plot design with three replications during 2009 and 2010. Results showed that salts accumulated in soil were 28.4% higher in I2 compared with other irrigation treatments. Soil nitrate concentration was statistically higher under I3 and S1 treatments (83% and 10%, respectively) compared with other irrigation and salinity levels. There was no K+ deficiency caused by salinity; however, salinity resulted in statistically lower K+/Na+ compared with no saline conditions. Plants took up 25% higher N in I2 compared with other irrigation levels. Furthermore, N uptake by plants decreased by an average of 18% under salinity condition indicating that higher N application rate above the required level under saline water application put the environment at the risk of groundwater N contamination. Results of this study confirmed the fact that Na+ accumulation in soil was more detrimental than Cl- accumulation for maize irrigated with saline water. Besides, according to threshold values for soil ions, the optimum levels of irrigation and N fertilizer for maize might be lower under saline water application. Furthermore, based on the grain yield reduction coefficient, maize required a higher level of K+ and K+/Na+ under deficit saline water irrigation for avoiding yield losses.

Crop production process utilizes input energy and produces some biomass energy as output.  During this process, greenhouse gases (GHGs) are also emitted which can make environmental risks. In this study, input and output energies, energy indices, and GHG emissions arising from inputs were estimated for wheat-cotton rotation under different tillage practices in Fars province. The study was conducted as a randomized complete plot experimental design with three tillage treatments and four replicates. Tillage methods included conventional tillage (CT), reduced tillage (RT), and no tillage (NT). Results showed that NT and RT decreased energy consumption in wheat and cotton production by 1.53 and 1.19%, respectively as compared to the CT due to less fuel and machinery utilization. More than 72% of energy requirement for wheat and cotton production was consumed by irrigation water and electricity for pumping irrigation water in all tillage methods. Conventional tillage resulted in the highest output energy, energy ratio, and energy productivity in wheat-cotton rotation compared to RT and NT. Total GHG emissions for wheat and cotton production were estimated to be 51829, 51608, and 51529 kg CO2e ha-1 in CT, RT, and NT, respectively indicating that NT and RT slightly reduced GHG emission compared to CT (0.6 and 0.4%, respectively). Results of this study indicated that irrigation showed the highest share in total energy requirement and GHG emission of wheat and cotton production in semi-arid climate condition of Fars province; therefore, total input energy and GHG emissions could be markedly reduced by using more efficient irrigation systems.

To evaluate the effect of residue of sulfonylurea herbicides and  wheat residues on the growth and yield of sunflower, a split factorial experiment was conducted based on a randomized complete block design (RCBD) with four replications at the College of Agriculture, Shiraz University, Shiraz, Iran. The treatments included with and without wheat residues from the tested farm as the main plots, and a combination of three herbicides (Total, Apirus and Atlantis) and their concentrations (recommended and 30% overdose) which were considered as subplots. No herbicide treatment was used as control. The results showed that application of all herbicides reduced sunflower height, seed number and seed weight as well as seed yield of sunflower. The highest reduction in seed yield was recorded when Total  followed by Apirus residues were applied, which caused 95% and 80.6% yield reductions, respectively. Also, the minimum reduction of seed yield (32.7%) observed in Atlantis treatment. Moreover, 30% increase in herbicides dose caused increasing adverse effects and decreasing grain and biological yield compared to the recommended dose. Wheat residues incorporated to the soil increased damage of Atlantis by maintaining it in the soil (reduced seed yield from 3932.3 to 3556.9 kg/ha) and reduced damage of Total and Apirus by further degradation of these herbicides (increased seed yield from 235.4 to 311.6 kg/ha in Total treatment, and from 996.6 to 1161.3 kg/ha in Apirus treatment). But overall, wheat residues increased seed yield (2.1%) in comparison to the removal of plant residue. Therefore, addition of wheat residues as organic matter in the soil can affect the biological changes of herbicides.

This paper presents stress and strain analysis of outer shaft shoulder (OSS) and inner shaft shoulder (ISS) of a new paddy harvesting head (PHH) using finite element method (FEM). Snapping grain unit is a part of this head, with OSS and ISS as its members. The analysis was performed using the ABAQUS software with Dynamics Explicit Solution Method. Eight-node block and four-node tetrahedral elements were used to mesh the parts of the head. After the analyses, the stress and strain curves, and their maximum values were estimated for various parts. Analytical method was used to verify the FEM results and to calculate the factor of safety (FS) of the OSS and ISS components and also to estimate the number of cycles to failure of each component. The maximum amount of force applied to each tooth of shoulder was 4.29 Nmm-1. The maximum stress in both shoulders was obtained as 44.43 MPa. Other results showed, fatigue factors of safety for all components were less than their relevant yield factor of safety. Therefore, the fatigue in components would occur first. The study showed the predicted life for OSS and ISS components is more than 106 cycles, thus the components have an infinite-life. A fitted regression line to the data showed that the calculated stresses from analytical method lie within bounds of 7.89 % of the predicted values with a coefficient of determination of 0.98. Hence, it could be concluded that there is a good agreement between the analytical and FEM results.

Quality of glazed (G) and non-glazed air-blast frozen rainbow trout (Oncorhynchus mykiss) was evaluated after applying different modern (M: microwave oven; U: ultrasonic; HVEFT: high voltage electrical field; O: ohmic heating) and conventional (S: steam cooking; W: water; R: refrigeration) thawing methods. Glazed frozen samples thawed by modern and conventional methods showed an increase in protein and pH contents (except for M/MG). The glazing process negatively affected the TVB-N (total volatile basic nitrogen) and % FFA (free fatty acid) levels and these compound increased after glazing in all thawed samples except for SG and S from  conventional and M, MG, U and UG from modern thawing methods, respectively. The TOTOX value of HVEF, HVEFG and OG was not significantly changed after thawing process compared with the fresh fish sample. Glazing could reduce the drip loss and increase the WHC (water holding capacity) in different thawing methods except for MG. MG and HVEFG/RG/WG had the lowest and highest hardness, respectively. The L* values of HVEF/HVEFG and U were higher than those of fresh and other thawing methods.

Salinity is a major abiotic stress for crop production in many parts of the world. To evaluate the effects of irrigation with saline water on growth parameters and forage quality of globe artichoke (Cynara cardunculus var. scolymus), a field experiment was conducted using a randomized complete block design with three replications at Isfahan Agricultural and Natural Resources Research and Education Center, Iran during 2013-2015. The treatments were four irrigation levels with saline water (4, 8, 12 and 16 dS.m-1). Plant fresh weight (FW), plant dry weight (DW), crude protein (CP), water-soluble carbohydrates (WSC), neutral detergent fiber (NDF), acid detergent fiber (ADF), dry matter digestibility (DMD), total tannins (TT) and ash content were measured in the second year of growth season. The results showed that the maximum fresh weight (51551 kg ha-1) and dry weight (9000 kg ha-1) were obtained at EC=4 dS.m−1. Increasing salinity levels caused a significant reduction in NDF and ADF contents, while ash, CP, DMD and TT contents were increased. The treatments of EC=12 and EC=16 dS.m−1 produced the highest amount of CP (178.3, 185.1 g/kg DM), DMD (613.2, 636.2g/kg DM) and the lowest content of NDF (598, 585.1g/kg DM) and ADF (393, 3778g/kg DM), respectively. The lowest tannin content (28.2g/kg DM) was observed in EC=4 dS.m−1 and there was no significant difference between the treatments of EC=8 and EC=12 dS.m−1. Generally, results showed that although increasing salinity decreased plant yield, it could increase forage quality characteristics.

Nowadays, applying soil amendments is one of the most important ways to cope with water shortages and improve soil physical properties. In this regard, a greenhouse experiment was conducted to study the effect of different levels of irrigation water and wheat straw biochar on physical and chemical properties of a sandy loam soil, after harvesting faba bean. The experiment was performed with 5 biochar levels (0, 8, 16, 24 and 32 g kg-1) and 3 irrigation levels (100%, 75% and 50% of crop water requirement) using completely randomized design in three replications. Lowering the irrigation level to 50% did not influence soil physical and chemical properties except for saturated hydraulic conductivity (Ks), as Ks was significantly declined under 50% irrigation water levels as compared with full irrigation. Soil bulk density and particle density of 32 g kg-1 biochar treatment (B32) was reduced by 47% and 27%, respectively, while soil porosity and Ks increased as compared to no biochar application (B0). Under B32 treatment, the saturated electrical conductivity increased 5.6 times, and the cation exchange capacity and sodium adsorption ratio (SAR) was increased by 40.3% and 53.6% in comparison with B0, respectively. This made the soil saline (ECe>4 dS/m) but not sodic (SAR-1)1/2). It can be concluded that although, biochar level of 24 g kg-1 did not considerably increase soil water holding capacity compared to B0, it significantly improved the other soil physical and chemical properties, therefore, it can be used as soil amendment.

Use of new techniques to evaluate irrigation areas can enhance water use efficiency in agriculture. In this study, the fuzzy analytic hierarchy Process (FAHP) was used to qualitative land suitability for sprinkler irrigation and was compared with the parametric method. Evaluation based on parametric method showed that an area of about 1597.83 hectares (31%) of the lands was highly suitable (S1) and an area of about 787.3 hectares (15%) was “moderately suitable” (S2). About 2242.9 hectares (43%) were marginally suitable (S3). Permanently inappropriate suitability included about 546.91 hectares (11%). Inappropriate in present condition suitability matched no land in the study zone. Based on the Fuzzy Analytic Hierarchical Process, there was not highly suitable (S1) area in the plain. The parts with S2 suitability also included an area of about 432.96 hectares (8.3%). Moreover, areas of about 3100.98 hectares (59.9%) were marginally suitable (S3). Some southwest and eastern parts of the plain were not currently suitable (N1) that included an area of about 1277.68 hectares (24.6%). N2 suitability was also observed in some southern in two parts including an area of about 363.38 hectares (7%). Since about 31% of the lands were included as "highly suitable" areas based on the parametric method, and in contrast, there was no "highly suitable" areas in FAHP method, so considering the area of "highly suitable" shown that there was a significant difference between the two methods in terms of "highly suitable" land evaluation. Considering the gradual changes in soil properties, FAHP evaluation has higher accuracy than the ordinary parametric method in evaluating land suitability.

Drought stress is considered as the most important limiting factor for growing of crops such as maize. Under low irrigation conditions, proper nutrition of plants can improve the effects of drought stress. This experiment was carried out in order to investigate the effect of nutrition management along with application of zeolite on agronomic traits of two hybrids of maize under deficit irrigation conditions in a field research in Soil and Water Research Institute in Karaj, Iran in 2015 and 2016 via a factorial split-plot plan based on a randomized complete block design with three replications. Experimental treatments included two levels of irrigation; full irrigation (I1) and deficit irrigation (70% of full irrigation) (I2) as the main factor and  factorial combination of fertilizer application at five levels; application of fertilizer in the conventional method (F1), fertilization application in conventional method + 10 tons of zeolite.ha-1 (F2), fertilizer application based on local recommendation (F3), fertilizer application based on local recommendation + 10 tons of zeolite.ha-1 (F4) and control (without fertilizer) (F5). Besides, maize hybrids including a late hybrid (SC704) (H1) and an early maturity hybrid (260 = Fajr) (H2) were considered as sub-factors. The results of analysis of variance showed that deficit irrigation had a significant effect on grain yield, number of grain.ear-1, ear weight, number of ear.m-2, and fertility of florets, while under deficit irrigation condition the values of these traits decreased. Under deficit irrigation treatment, the highest grain yield of maize hybrids (7934.3 and 7793.8 kg.ha-1 for 704 and 260 hybrids, respectively) was obtained from recommended fertilizer application + zeolite, which were 7% and 15% less than grain yield of corresponding maize hybrids (8180 and 9170.29 kg.ha-1 for 704 and 260 hybrids, respectively) where recommended application of fertilizer + zeolite were used under full irrigation condition. In general, the appropriate fertilizer management with the application of 10 tons of zeolite.ha-1 led to a higher grain yield of both late and early hybrids of maize and saving 30% water consumption (up to 2100 m3.ha-1).

In order to evaluate canopy and organs temperature depression (TD) under heat stress conditions and the effects of plant morphology on organs temperature depression and their association with grain yield, two field experiments were conducted using six wheat cultivars (Behrang, Chamran, Kauz, Koohdasht, Karim and Montana) planted on three dates (early, optimum, late) in 2014-2015 and 2015 -2016 cropping seasons in Dashtestan, Bushehr, Iran. In addition, three concentrations of salicylic acid (0, 0.5 and 1 mM) were applied to alleviate the effects of heat stress.  Canopy and organs (flag leaf, peduncle and spike) temperature were measured by a hand-held infra-red thermometer (IRT). Also, some morphological traits in addition to yield components were measured. Results showed that the effects of cultivars and heat conditions were significant for most of the studied traits but salicylic acid application showed no significant effects. Under late sowing date, canopy and organs temperature depression were significantly higher than those at early and optimum sowing dates. No significant differences were found between early and optimum sowing dates for all temperature depressions. Among cultivars, Behrang had higher canopy temperature reduction (CTD), flag leaf temperature depression (FLTD) and peduncle temperature depression (PTD). Spike temperature depression (STD) was higher in Chamran and Kauz cultivars. Among plant organs, peduncle had higher temperature depression followed by flag leaf and spike. Canopy and organs temperature depression had positive correlation with stomatal conductance and grain yield. This research suggests that temperature depression can be used as an important criterion for the selection of stable genotypes under late sowing conditions. This is very helpful to improve wheat productivity under terminal heat stress resulting from late sowing conditions.

Operators of agricultural machinery are exposed to an extensive range of indirect vibrations through the seats, which gradually causes chronic damages. One of the ways to reduce the vibrations imposed on the operators is to use appropriate materials in tractor seat cushion. The present study was carried out in order to select appropriate foam or sponge and investigate different factors in reducing vibrations imposed on operator’s body so as to promote drivers health and enhance their working efficiency. Vibration experiments were performed at different accelerations on foam and sponge materials at different thicknesses and densities for different occupant masses, and the input and output acceleration signals were recorded and analyzed. Using the analysis of variance, analysis of the mean squares of the input and output acceleration, the type of material used in the seat cushion and the effect of different factors on them were investigated. The results showed that in reducing vibrations, sponge for mass of 90 kg and more and foam for mass of 75 kg and less were more efficient. The sponge was also suitable for acceleration of excitation above 6 ms-2and foam for acceleration of excitation above 3 ms-2 and below. Therefore, according to the working conditions of agricultural machines and anthropometric characteristics of Iranian drivers and the appropriate suitable thickness of the seat cushion (6-8 cm), it is recommended that their seat cushion be made of a combination of foam and sponge with high density and thickness of 8 cm.

The pasture and forest land use change to agricultural use can effect on many properties of the soil and its productivity. The present research aims to investigate various forms of K (soluble, exchangeable, non-exchangeable, and structural forms) and some soil properties in different land use of three areas including Choram, Kakan and Bahmaei in Kohgiluyeh and Buyer-Ahmad Province. Four profiles were excavated in different land use of each area (In total, 12). All profiles were described and classified based on the Keys to Soil Taxonomy. The results showed that there is not any significant positive correlation between the clay and silt contents in different land use, while the lowest content of clay was observed in agricultural land use. The percentage of organic carbon was in its highest level in pasture land use (1.01%), and in its lowest level in agricultural (0.7%) and (0.4%) wheat cultivation. The highest and lowest pH levels were obtained in paddy soil (8.11) and garden (6.8), respectively. The average level of soluble, exchangeable, non-exchangeable, structural and total forms of K in the studied area were 0.5- 6.1, 45-262, 86-366, 835-5197 and 967-5555 mg/kg of the soil, respectively. The studied soils of Kakan and Choram areas had the lowest and highest levels of non-exchangeable, structural, and total forms of K, respectively. In addition, the highest levels of soluble and exchangeable forms of K were observed in Bahmaei and Kakan areas, respectively. The soluble and exchangeable forms of K had significant changes in different land use,