Iran Agricultural Research
Volume:38 Issue: 2, Summer and Autumn 2019

Harvest index (HI), ratio of seed yield to aboveground dry matter, is a very important parameter for estimating seed yield in several crop models. In this study, the importance, definition, variability and estimation methods of HI in crop models were discussed. HI estimation methods are categorized into two groups including: (i) complex methods that estimate HI from the beginning of seed growth to crop maturity, dynamically and (ii) simple methods that estimate the final HI at crop maturity. HI is a trait that is affected by many environmental parameters and the genotype of a crop. Soil water content or soil water suction during growing season, soil nutrient, groundwater depth, high air temperature, plant population and irrigation water salinity are some environmental factors affecting the HI. Therefore, in all models that used HI to estimate crop yield, either complex (e.g., AquaCrop model) or simple method, the harvest index estimating equations should be calibrated by changing the genotypes or cultivars, environmental and non-environmental parameters.

The Standardized Precipitation Index (SPI) is a widely used drought index to provide good estimations of the intensity, magnitude and spatial extent of droughts. The objective of this study was to analyze the spatial pattern of drought by SPI index. In this paper, patterns of drought hazard in Khuzestan are evaluated according to the data of 17 weather stations during data recording. The influenced zone of each station was specified by the Thiessen method. Then, it was attempted to make a new model of drought hazard using GIS. Three criteria for drought were studied and considered to define areas of vulnerability. Drought hazard criteria used in the present model included: maximum severity of drought in the period, trend of drought, and the maximum number of sequential arid years. Each of the vulnerability indicators was mapped. These maps along with a final hazard map were classified into 5 hazard classes of drought included none, slight, moderate, severe and very severe classes. The final drought vulnerability map was prepared by overlaying three criteria maps in GIS, and the final hazard classes were defined on the basis of hazard scores, which were determined according to the means of the main indicators. The final vulnerability map showed that severe hazard areas (29% of the province) which were observed in the northern and central parts of study area are much more widespread than areas under the slight hazard class. Nevertheless, approximately more than half (64%) of the province area was determined to be moderate hazard class for drought.

Agricultural extension, as an informal educational system, is one of agricultural development tools that lean on human capitals. Inefficiency of public bureaucracy on the one hand, and managerial problems on the other hand, as well as neglecting real needs of beneficiaries in planning, have determined responsible to transfer administrative tasks to the private sector and reduce government''s tenure. This survey was conducted in Kerman as the first ranked province of pistachio production in Iran to investigate attitudes about extension private services among pistachio farmers. A questionnaire was used as the research tool for data collection. Face validity of the questionnaire was verified by extension experts and Cronbach''s alpha computation showed that reliability of the questionnaire was between 0.8 and 0.89. The study ran among pistachio farmers of five counties (Rafsanjan, Sirjan, Zarand, Kerman and Ravar). Random cluster sampling method, with a sample size of 382 respondents was applied. Finally, the collected data were analyzed using SPSS software. Results revealed that several factors such as education level, participating in extension activities, innovation acceptance, membership in associations, cosmopolitan, positive attitude toward knowledge and information, applying numerous information resources, pistachio yield per hectare, area of the pistachio garden and satisfaction of the private consultants had relation with attitude toward privatization of extension. Also, the level of participation in extension activities and attitude toward the public extension could explain 24.8 percent of changes in attitude toward private extension.

Infiltration rate is one of the most important parameters used in irrigation water management. Direct measurement of infiltration process is laborious, time consuming and expensive. Therefore, in this study application of some indirect methods such as artificial neural networks (ANNs) for prediction of this phenomenon was investigated. Different ANNs structures including two training algorithms (TrainLM and TrainBR), two transfer functions (Tansig and Logsig), and different combinations of the input variables such as sand, silt, and clay fractions, bulk density (BD), soil organic matter (SOM), cumulative infiltration (CI) and elapsed time were used to predict sorption coefficient (S) and hydraulic conductivity (A) in Philip equation (I=S*t0.5+A*t), which corresponded to 30 soil samples from study areas located in the Agricultural College, Shiraz University, (Bajgah). A two-hidden layer ANNs with two and three neurons in the hidden layers, respectively and TrainLM algorithm performed the best in predicting S when Logsig and Tansig were used. Silt+ clay+ sand+ time+ CI combination was the most basic influential variables for the S prediction. Furthermore, a two-hidden layer ANNs with two and three neurons in the hidden layers, respectively and TrainBR algorithm performed the best in predicting A when Tansig and Tansig were used. Silt +clay +sand +BD + OM+ time+ CI combination was the most basic influential variables for A prediction. Results showed that increasing the hidden layers and input variables significantly improved the ANNs performance. The coefficient of determination (R2) confirmed that the ANNs predictions for A (84.6 %) fit data better than S (77.5 %).

Direct use of poultry manure (PM) as an organic fertilizer in agriculture may cause environmental concerns; therefore, application of its biochar might be an effective solution. A greenhouse experiment was conducted to investigate the influence of PM and its biochar (PMB) (control, 1% and 2% PM (w/w), 1% and 2% (W/W) PMB) on the growth and micronutrients concentration of corn under salinity stress (0.5, 3.6, 7.9 and 12.4 dS m-1) in the presence or absence of arbuscular mycorrhizal fungus (AMF) (Funneliformis mosseae). Results indicated that application of PM and PMB significantly increased corn shoot dry weight (SDW) compared to that of control in non-AMF plants. However, SDW was higher in PMB application compared to that of PM by 15% and 8% for 1% and 2% (w/w) application rates, respectively. In AMF-plants, addition of 2% PMB had no significant effect on SDW compared to that of control. Hence, co-application of PMB (2%), and AMF did not increase SDW due to the fact that AMF was ineffective to enhance corn yield (at high phosphorous (P) concentration in 2% PMB rate). Salinity stress, at low levels (3.6 and 7.9 dS m-1), increased SDW of corn but at a higher level (12.4 dS m-1), decreased it significantly, in both non-AMF and AMF plants. In general, shoot micronutrients concentration (except for Cu) significantly increased along with increasing soil ECe levels in AMF and AMF plants. In non-AMF plants, only addition of 2% PMB increased shoot Mn concentration by 20% compared to that of control. However, in AMF plants, application of PM (2%) and PMB (1% and 2%) decreased Mn concentration by 27%, 16%, and 9% compared to those of control treatment, respectively. Poultry manure biochar increased corn shoot Zn, Cu and Fe concentrations compared to those of control due to the higher concentration of these nutrients in biochar compared to PM. In conclusion, pyrolysis of PM almost eliminated foul odor of PM and increased dry matter yield of corn.

Sugarcane (Saccharum officinarum L.) is a multi-purpose crop, mainly planted in South-western (SW) parts of Iran. However, the capability of sugarcane farms to sequestrate carbon into soil and plant is not well documented. In this research, the carbon sequestration in sugarcane plant and soil in a ratooning traditional cultivation system at the Amirkabir Sugarcane Agro-Industry Complex in Khuzestan Province was evaluated during 2013-2014. The soil samples were randomly collected at 0-30 cm top layer and soil organic carbon (SOC) was analysed in laboratory. Simultaneously, both aboveground and underground parts of sugarcane plants were sampled and the carbon content of each part was measured separately. The carbon stored in the aboveground parts (leaves and shoots) was significantly (p≤0.01) higher (1292 kg ha-1) than that (655 kg ha-1) of underground organs (roots). The total SOC (1987.3 kg ha-1) was not considerably higher than the sequestrated carbon (1947 kg ha-1) in plant parts. Furthermore, a positive and significant correlation was found between SOC and soil clay content. Overall, 3934.5 kg ha-1 sequestrated carbon equal to 14439.6 kg ha-1 atmospheric CO2 was estimated to be in sugarcane farms. In conclusion, the results showed that the Ratoon I has the highest potential of carbon sequestration than other treatments. Current sugarcane farming practices in Khuzestan could act as an important pool for carbon sequestration and consequently enhancing the mitigation of climate change impacts. It seems that changing the current sugarcane traditional harvesting system which is predominantly based on burning the residues towards the suitable management could enhance the capability of carbon sequestration even more.

Adoption of conservative agriculture at farm level is associated with reducing the production costs and leads to crop yield stability. The aim of this study was to prioritize experimental treatments based on different criteria by applying "technique for order preference by similarity to ideal solution" (TOPSIS).A filed experiment was carried out at Zarghan research station, Fars province, Iran, during 2014-2016 growing seasons. Experimental treatments were three tillage practices including conventional tillage (CT), reduced tillage (RT) and no tillage (NT) that were assigned to main plots and four spring wheat genotypes (Chamran, Sirvan, Picaflor#1 and M-89-10)were randomized in subplots using split-plot arrangements in randomized complete block design with three replications. Selected criteria including two groups of economic- i.e. water cost, weed control cost, production cost and gross margin- and agronomic –i.e. grain yield and soil bulk density criteria used to prioritize the treatments. The weights of bulk density (0.040), grain yield (0.180), gross margin (0.280), water cost (0.0270), weed control cost (0.150), and production cost (0.080) was calculated. Results showed, considering all criteria to prioritize wheat genotypes under different tillage practices, that Sirvan and Picaflor#1 genotypes under RT practice could be the first treatments in 2014-15 and 2015-16 growing seasons, respectively. Therefore, the multiple criteriamethodshould be used for selection of the best tillage practices and wheat genotypes under tillage practices rather than a criterion such as grain yield or production cost.

Mealiness degrades the quality of apples and plays an important role in fruit market. Therefore, the use of reliable and rapid sensing techniques for nondestructive measurement and sorting of fruits is necessary. In this study, the potential of acoustic signals of rolling apples on an inclined plate as a new technique for nondestructive detection of Red Delicious apple mealiness was investigated. According to destructive confined compression tests, the mealiness of apples was evaluated by the hardness and juiciness measurements. In addition, support vector machine (SVM) models were developed to classify apples. The radial basis function (RBF) as the kernel was used in SVM models. According to exhaustive search method, the model with nine features combination was found to be the best model. Results indicated overall accuracy of 85.5 % to classify apples in mealy and healthy groups. The results indicated that this method is potentially useful for apple mealiness detection.

Determination and recognition of relative distribution of chemical forms of each element and their relationship with physical, chemical and soil clay minerals can help researchers to manage soil fertility better. This research attempted to recognize chemical fractions of zinc (Zn) and copper (Cu) in some surface and subsurface soil samples of Kohgiluyeh and Boyer-Ahmad province and their relation with physico-chemical properties and clay minerals. In order to carry out this research, surface and subsurface soil samples were collected in different physiographic units of the province and chemical fractions of Zn and Cu were measured by sequential extraction method and ultimately their relationship with different soil characteristics was investigated. Results showed that exchangeable and sorbed chemical fractions of Cu and Zn in all soil samples were lower than the detection limit of atomic absorption spectroscopy. Distribution of chemical fractions of both Zn and Cu followed the order: residual> carbonate> organic fractions. The low and medium mobility factor of Zn and Cu, respectively, in the studied soils indicated the different behavior of these elements in calcareous soils. Among all soil physico-chemical characteristics, organic carbon showed more obvious effects on controlling the chemical fractions of Zn. On the other hand, chemical fractions of Cu showed significant correlations with clay and silt content, as well as cation exchange capacity. The correlation between the clay minerals content with chemical forms of these elements showed that the amount of different forms of Zn and Cu is directly related with 2:1 clay minerals (especially vermiculite).

Wood vinegar is a substance, derived from cooling black carbon fire, which could be used instead of chemical materials in the agriculture industry as an organic compound. In order to study the effectiveness of pine wood vinegar on physiological and photosynthesis traits of cucumber, two experiments were conducted based on a completely randomized design with six treatments including 0, 1250, 2000, 2500, 3333 and 5000 mgL-1 of wood vinegar with four replications. The first experiment was designed in the laboratory in order to study the effect of pine wood vinegar priming on cucumber seeds and the second one was conducted in a greenhouse condition to investigate the effect of wood vinegar on seedlings of cucumber in Isfahan University of Technology. The highest flower number and yield in cucumber was observed in 2500 mgL-1 pine wood vinegar trearment. Photosynthesis in cucumber increased in 2000 mgL-1 pine wood vinegar trearment. The lowest transpiration in cucumber was 1.54 mmolm–2s–1 in 2000 mgL-1 pine wood vinegar treatment. 1250 mgL-1 wood vinegar treatment increased germination percentage and speeded up the germination process compare to control. The highest root length, volume and surface were observed at 1250 mgL-1 treatment. The concentration of nitrogen (5.5% DW) in the treatment of 3333 mgL-1 Pine wood vinegar, the potassium concentration in the treatment of 5000 mgL-1 and calcium and iron concentrattions in the treatment of 1250 mgL-1 were at the highest levels compared to other treatments. The highest amount of chlorophyll and photosynthesis was observed at 2000 mgL-1 treatment. The wood vinegar with 2500 mgL-1 pine wood vinegar concentration showed the highest flower and fruit yield in cucumber, but the best quality of fruit was produced by 2000 mgL-1 treatment.

Weeds are a serious problem of chickpea cultivation in rain-fed areas of Iran and economic feasibility of crop production is mostly challenged by the method of control. In this study, two types of weed control strategies which are common in the country, including hand removing and hand removing + mechanical application, were compared with application of general herbicide (Glyphosite) using a specific spray machine under a minimum tillage system. The trial was carried out in the farms of five ha each, along with a two-ha weedy control at Dry land Agricultural Research Institute (DARI), Maragheh, Iran during cropping season 2018-2019. Chickpea cultivar “Adel” was sown under no - tillage system in planting arrangements of 17.5 × 52.5 cm using a direct drill machine followed by routine operations such as pesticide or fertilizer applications during the growth season. Three patches of 10 m2 of each treatment were randomly chosen as blocks and measurements were conducted on four randomly chosen 1 m2 samples as replications inside them. Data arranged as completely randomized blocks design were analyzed. Results showed that although higher yield indices belonged to hand removing or hand removing + mechanical applications, a powerful economic feasibility could be obtained by application of Glyphosate using the spray machine. It may be inferred from this study that in the absence or under situations where application of selective herbicides is non-economic, farmers can apply relatively in-expensive general herbicides to control weeds using this machine and gain acceptable income.

Cynara cardunculus var. scolymus L. is a herbaceous perennial plant that could be drought tolerant once established after the first year. To evaluate the effects of water stress on growth parametersand forage quality of this plant, a field experiment was conducted using a randomized complete block design with three replications in Isfahan, Iran during 2013-2015. Treatments were irrigation at 20 % (non-stress), 50 % (moderate stress) and 80 % (severe stress) depletion of the soil available water. Plant fresh weight (FW), plant dry weight (DW) and some forage quality characteristics such as crude protein (CP), crude fat (CF), water-soluble carbohydrates (WSC), neutral detergent fiber (NDF), acid detergent fiber (ADF), dry matter digestibility (DMD), total tannins (TT) and ash content were determined at the heading stage. Results indicated that growth and forage quality were significantly affected by water stress. The highest rates of FW, DW, NDF, ADF, CF and ash contents were recorded at non-stress conditions which were decreased over increasing stress severity by 40.67, 51.71, 6.54, 18.23, 8.83 and 21.81 %, respectively, while the highest rates of CP, DMD, WSC, and TT contents were observed at the severe water stress conditions. Generally, although water stress decreased forage yield, it had a positive role in qualitative characteristics of Cynara forage due to the increase in CP, DMD and WSC along with the decrease in NDF, ADF and ash content.

Seaweeds are rich sources of bioactive natural products, which have been considered as potential biotic agents. Ulva flexuosa Wulfen is a species of seaweed which is endemic to the Persian Gulf. In this study, the effect of different concentrations of U. flexuosa extract on  the  antioxidant activity of Washington Navel orange (Citrus sinensis L. cv. Washington Navel) fruits (measured as free radical scavenging activity; FRSA) and postharvest quality of the fruits were evaluated under cold storage (5±1°C) conditions and 85-90% relative humidity up to 60 days. Results indicated that prolonging the storage time increased fruit weight loss, fruit decay and total soluble solids (TSS) contents of the fruits, while prolonging the storage time reduced the percentage of juice and ascorbic acid contents of the fruits. Postharvest quality and antioxidant activity of Washington Navel orange fruit improved significantly when they were immersed in seaweed extracts. The most effective treatment was 3.76 g L-1 concentration of Ulva flexuosa extract, which maximized the improvement of antioxidant capacity, ascorbic acid content and TSS during days of storage (DS). The results of this study indicated that the seaweed extract could be used as a new bioactive agent for maintaining the postharvest quality of orange fruit through enhancing the antioxidant activity.