Iran Agricultural Research
Volume:34 Issue: 2, Summer and Autumn 2015

In this study, effect of deficit irrigation with different salinity levels and planting methods (in-furrow and on-ridge) on nutrient and toxic ions uptake by rapeseed was investigated in a two-year experiment. The experiment was conducted at Research Station, located in the College of Agriculture, Shiraz University, I.R. of Iran. Results indicated that an increase in water stress level decreased uptake of potassium (K), calcium (Ca), sodium (Na) and chloride (Cl) by plant and with exception of K, those uptakes were enhanced by an increase in salinity of water and soil. Furthermore, a decrease in applied water decreased the threshold of Na in soil for seed yield reduction. Deficit irrigation had a significant effect on slope of the fitted line between Cl in plant (Clp) and Cl in soil. The Clp threshold for seed yield reduction was significantly different for two planting methods in full irrigation regime so that seed yield reduction occurred in higher Clp in in-furrow planting method. Also, a decrease in applied water decreased Clp threshold for seed yield reduction.

The species Frankliniella occidentalis (Pergande),western flower thrips, is a highly polyphagous pest and an important vector of tospoviruses on several crops and ornamental plants. Western flower thrips has been introduced throughout the world and has been subject to many biological studies including mass rearing. In this survey, seven common mass rearing methods of F. occidentalis were described in detail and compared with each other. As a result, using Persian cucumber in plastic boxes by producing 6.15±0.4122 generations was selected as the best method. This method enables rearing multiple thrips generations on Persian cucumbers by using minimal supplies.

Inadequate water supply is the major problem for agriculture in arid and semi-arid regions. Thus, effective management should be considered for water resources planning. In this research, a model was provided which is able to estimate optimal land and water allocation in the Doroodzan irrigation network. Optimal water management model was used at farm level to evaluate different deficit irrigation (DI) strategies at various periods of crop growth. Genetic algorithm toolbox by MATLAB (Mathworks, 2009) software was used for benefit optimization considering practical constraints. Results showed that deficit irrigation technique significantly reduced water allocation and increased the crops cultivation area in the region. In addition, increase in water price and the occurrence of drought resulted in cropping pattern change and led to including crops with high economic values. Application of this model ensures the optimal use of available water resources in all conditions, especially under drought condition. The proposed model is capable of defining water management plan with regard to the amount of available water and price of water and product, for simultaneous optimal land and water allocation.

This study aims to model optimal cultivation pattern based on the maximization of importing virtual water and social net income of major crops in Marvdasht, Iran. For this purpose, a linear programming model was developed considering constraints of virtual water and land limitations followed by other models to include employment restrictions. Based on the findings, wheat and tomato were recognized as optimal products for the region. Regarding the virtual water imports, wheat has an advantage over tomato while the production of tomato needs a relatively considerable number of workers which leads to the improvement of employment in the studied areas.

The effects of iron (Fe) and zinc (Zn) treatments on the growth and nutrient composition of chickpea were studied in a greenhouse experiment arranged in a completely randomized design. While the application of Fe decreased mean shoot dry weight of chickpea, that of Zn had no significant effect on chickpea shoot dry weight. Increasing Fe levels drastically decreased Mn concentration and uptake in chickpea shoot. Addition of Zn, however, had no significant effect on Mn concentration and uptake in chickpea shoot. Although the addition of 10 mg Fe kg-1 significantly increased mean Fe concentration in chickpea shoot, the effect of Fe application on mean Fe uptake was negligible. Although the application of Zn had no significant effect on mean Fe concentration or uptake, it increased mean Zn uptake in chickpea shoot. While the application of Fe increased mean Zn concentration, application of 5 mg Fe kg-1 had no significant effects on mean Cu concentration or uptake in chickpea tissues although 10 mg Fe kg-1 increased mean Cu concentration and uptake in chickpea tissues. Addition of Zn, however, had no significant effect on Cu uptake. A significant negative correlation was observed between Mn uptake and Fe rates demonstrating a reduction in shoot Mn uptake following Fe application. Although shoot dry weight of chickpea was negatively correlated with Fe rates, it showed significant positive correlations with the uptakes of Zn and Mn indicating that the patterns of changes in dry matter was in coordination with changes in Zn and Mn uptakes. Since Fe chelate addition may cause nutrient imbalance and growth reduction in chickpea, it appears that the use of Fe and Zn efficient genotypes should be considered as an appropriate practice for chickpea grown on calcareous soils low in available Fe and Zn.

Greenhouse experiment was conducted in factorial experiment arranged as a completely randomized design (CRD) to evaluate the effect of Glomus intraradices, Pseudomonas fluorescence and soil drying on different forms of potassium (K) and the changes of clay minerals in a calcareous soil after maize planting. Treatments consisted of arbuscular mycorrhizal (AM) fungus at two levels: G0 (not inoculated with fungus) and G1 (inoculated with Glomus intraradices), bacteria at two levels B0 (not inoculated with bacterium) and B1 (inoculated with Pseudomonas fluorescence) and soil drying levels or four irrigation intervals of 2 (S0), 4(S1), 6(S2) and 8(S3) days. As soil drying increased, all forms of K increased and root colonization decreased. Inoculation of plants with microbial inoculants increased root colonization percentage and all forms of K in soil as compared to non microbial treatments. However, the effect of single inoculation with bacterium was less pronounced. Co-inoculation treatments of plants with fungus and bacterium resulted in the maximum amounts of root colonization and K forms as compared to single inoculation of plants with each inoculum. The amount of illite-chlorite minerals increased as soil dryinglevels increased. In non mycorrhizal treatments, there were no smectite minerals, while in mycorrhizal treatments, the quantity of smectite minerals increased as the levels of soil dryingincreased. It might be concluded that biofertilizers and soil drying are effective in minerals weathering and dissolution and K releasing.

The crop water stress index (CWSI) is the most common index to monitor and assess crop water stress, based on canopy temperature. To calculate CWSI, upper and lower baselines adaptable to different environments are needed. In this study, empirical and theoretical limiting baseline equations were developed to determine eggplant CWSI values at different levels of water deficit and salinity stress. The limiting baseline and CWSI values of eggplant were obtained under different watering intervals (daily, weekly and every two weeks) and different irrigation water salinity levels (i.e. 0.8, 2.5, 5 and 7 dsm-1) for greenhouse and outdoor conditions. The impact of various levels of water deficit and salinity on total evapotranspiration, yield and CWSI was also studied. With the increase of water salinity, a decrease in the slope of lower baseline was met (from 0.195 to 0.146 in the greenhouse and from 0.134 to 0.098 in the outdoor conditions) along with a rise in the upper baseline. Increase in the levels of water deficit led to greater fluctuations in CWSI variations during the growing season. According to the Duncan's test results, CWSI values were significantly affected by water deficit and salinity in both environments

Olive (Olea europaea L.) is one of the most valuable and widespread fruit trees in Iran. Salt stress-induced changes in membrane stability, photosynthesis and antioxidant enzyme activity were examined on four olive cultivars (Dakal, Shiraz, Zard and Amigdalifolia) by emphasizing the correlation between measured parameters and ion (K+, Na+) accumulation. Plants were subjected to four salt treatments (0, 100, 150 or 200 mM NaCl) under greenhouse conditions. The exposure of the olive plants to increased salinity resulted in a decline in relative leaf chlorophyll content (RLCC), photosynthesis rate (Pn), transpiration rate (E) and leaf and root K+ content. NaCl increased superoxide dismutase (SOD) and peroxidase (POX) activity of olive leaves. Increasing the concentrations of NaCl in soil increased the concentration of Na+ in the leaves and roots. Differences in the effectiveness of Na+ exclusion mechanism among cultivars at high salinity reflected differences in salt tolerance. ‘Zard’, the better-adapted cultivar, displayed tolerance to high internal salt concentrations without apparent cell damage. Relationships between parameters involved in salinity response are discussed in relation to ion accumulation in leaves and roots of olive cultivars.

Over the past 50 years, oil mulching has been a common technique for sand dune stabilization in the southwest of Iran (Khuzestan province). However, concerns over the release of heavy metals from oil mulching have led to the search for alternative mulches that are capable of stabilizing sand dunes without environmental hazards. This study investigates the feasibility of using sugarcane residues for producing environment-friendly mulches. Dunder, Press Mud, and clay soil from the surrounding area near the sand dunes were used to make sugarcane mulches for comparison with the traditional oil mulch. A sand dune was selected as a sample bed for applying the mulch. To select the proper ingredients and treatments, Dunder, Press Mud, and clay soil were mixed with water by a trial-and-error method. The selected batch mix was then used to make the desired mulch and sprayed on a sand dune bed. Shear strength of surface soil (SSS), penetration resistance (PR), soil surface shear resistance (SSR), and erodibility of selected treatments were measured by the shear torvane, hand penetrometer, Zhang’s surface shear device, and the wind tunnel. The treatments were arranged in a factorial experiment within a completely random design with the factors including mulch type (seven sugarcane mulches and one traditional oil mulch), thickness (1 or 2 layers), and rainfall (rain and no rain). The results indicate that SSS and PR increased with mulch thickness; the average values of SSS and PR obtained with the two-layer treatments were 1.27‒1.33 and 1.13‒1.15 times as great as the single-layer treatments. Increasing fraction of sugarcane residues significantly increased the SSS and PR. Higher concentrations of organic matter, CaCO3, and electrolyte in the sugarcane mulches may have helped the bonding of soil particles and increased the SSS and PR. However, the oil mulch had the lowest SSS but the highest PR. This might be due to the lower viscosity of oil mulch that allows it to penetrate sand dunes more easily than sugarcane mulches do.

To investigate the effect of draught stress on water relations, stomatal density, chlorophyll content and yield of rapeseed, an experiment was done with four levels of drought stress including L1 (Field Capacity, FC), L2 (70% Available Water Content, AWC), L3 (50% AWC), and L4 (30% AWC), within three growth stages- including stem elongation (T1), onset of flowering (T2) and silique formation period (T3) at the University of Maragheh in 2013. The results showed that the lowest relative water content and leaf water potential were obtained at 30% AWC and silique development stage. Meanwhile, the highest water use efficiency (WUE) was observed during flower bud and silique development stages and 70% AWC. Furthermore, the results demonstrated that stomatal was only influenced by the levels of applied stresses and the highest stomatal density was recorded in 30% AWC. Implementation of 30% AWC in silique development stage diminished chlorophylls a, b, and total chlorophyll content to their lowest points so that compared to field capacity (L1), they decreased about 59, 67 and 62 percent, respectively. Likewise, the least grain yield belonged to stress application at flower bud development stage and 30% AWC stress level. Also, the grain yield loss in L4×T3 (30%AWC in silique formation period) treatment in comparison with the L1 (Field Capacity, FC) was 46.2 percent. Seed protein content was adversely affected by stress level and any decrease in AWC led to a concomitant decrease in protein content. At the same time, seeds oil content was influenced by stress application times. Water deficit stress during flower bud formation had the greatest adverse effect on seeds oil content. Overall, it was concluded that severe water deficit (30% AWC) led to the decrease of chlorophylls a, b, total chlorophyll, seed protein, oil content and yield.

Different evapotranspiration (ET) estimation equations having different accuracy with different conditions have been developed for ET estimation. This study will firstly focus on the estimation of 13 climatic equations of daily garlic ET estimation whose ET is measured by lysimeter to provide information which can be helpful in selecting an appropriate ET equation. The paper aims at showing the potential for combining the result of the best equation to improve the overall accuracy. The findings showed that the five equations of FAO 56 Penman–Monteith, ASCE Penman–Monteith, Kimberly Penman, Penman, and FAO-24 Blaney-Criddle were the most accurateequations for estimating garlic ET. The results of these five equations were combined using the three combination methods of Simple Average Method (C-SAM), multiple linear regression (C-MLR) and Adaptive Neuro-Fuzzy Interface System (C-ANFIS).The comparison of combination methods at the test stage showed that although C-SAM used simpler equations than C-MLR but its results were more reasonable than C-MLR. Overall, the results of these two combination methods did not significantly surpass those of the best ET estimation equations (FAO 56 PM); however,C-ANFIS combination method estimated ET better than the other techniques. Based on the results of this study, the C-ANFIS combination method is recommended for estimating garlic ET.

Due to the important role productivity plays in future decision making and programming, the productivity indexes should have accurate quantities. In this study, Auto-Regressive Distributed Lag (ARDL) and Genetic Algorithm (GA) methods are applied to time series of 1978-2008 to accurately measure total factor productivity (TFP) in the agricultural sector of Iran. The comparison of these two methods shows that GA method is more efficient than ARDL model. Also, the growth of TFP in the agricultural sector of Iran has had high fluctuations and annual average of productivity growth in this sector has been -0.16 during the period of the study. Therefore, it is necessary to emphasize the optimum use of available inputs, their appropriate combinations and increasing productivity in the agricultural sector of Iran.

As the world's population has grown and become more urban and affluent, waste production has raised drastically. Wastewater reuse has been identified as a way to alleviate water scarcity and improve crop productivity and environmental sustainability. To address the issue, a soil column experiment was carried out in a 3 × 3 factorial randomized block design including three treatments of adsorbents (non-pretreated leachate (L1), rice husk filtered leachate (L2), activated carbon filtered leachate (L3)) and three levels of zeolite (0, 5 and 10% by soil weight).A decrease in drainage water volume through the experiment period was observed. Application of zeolite at 5% level could improve soil removal efficiency and had a positive impact on the quality of the wastewater, as indicated by changes in EC, Na+, Ca2++Mg2+, Cl- (decreased by 22%, 15%, 24%, 15% respectively) and total P (increased by 12%) for treatment of leachate. However, adding 10% zeolite did not make a significant difference (p<0.05). Adsorbents used in the experiment had a significant effect (p<0.05) on the parameters such as N-NH4+, SAR, total P and Na+ content. Changes in most parameters for the L3 treatment were statistically significant (p<0.05) compared to other leachates (less N-NH4+ (40%), total P (33%) and more Ca2++Mg2+ (14.3%), Na+ (14%)) indicating an increase in adsorbent efficiency due to rice husk activation. Therefore, it can be concluded that application of zeolite can improve soil removal efficiency for treatment of leachate, but the rates of application can be case sensitive depending on the soil and the type of zeolite.