فصلنامه تحقیقات مهندسی کشاورزی
سال شانزدهم شماره 2 (تابستان 1394)

The management of surface irrigation systems, specifically furrow irrigation, is costly, time-consuming, and complicated because of spatial and temporal variations of infiltration. The infiltration parameters for inflow discharge, furrow geometry, and soil water content vary for furrow irrigation; consequently, it is difficult to present a general equation for infiltration. Scaling is a suitable method of obtaining a general relationship for infiltration. The present study developed an appropriate equation for scaling of infiltration components using dimensional analysis and irrigation test datasets with 15 replicates for 12 distinctive furrows. Calibration of the proposed equation produced R2 and RMSE values of 0.984 and 0.0199, respectively. The results for validation of the equation demonstrated high R2 values (>0.98) and low RMSE values (<0.01), which reflects the accuracy of this model. A comparison of the proposed model and published equations revealed the superiority of the proposed equation. The advantages include the need for less data (inflow discharge, flow depth in furrow, irrigation time, and advance time) and ease of measurement of the required inputs.

A relatively large number of field measurements are required to accommodate the spatial and temporal variability of the soil infiltration characteristics needed to express field conditions. Scaling is a recently-developed method that reduces the data needed to determine infiltration parameters. The present study evaluated the use of scaling to estimate infiltration parameters for variable alternate furrow irrigation and fixed alternate furrow irrigation methods that uses a single advance time and model infiltration curve to determine infiltration parameters. Field data from seven irrigation events during the maize growing season in clay loam soil in Karaj, Iran was used to evaluate scaling for both irrigation methods. The relative error for estimation of total infiltration was 1.44% to 20.03% for fixed and 0.48% to 13.80% for variable alternate furrow irrigation. No significant difference was observed between the measured and scaled data for infiltration.

Simulation models are important for evaluation of the effects of environmental stress on crop yield. The AquaCrop model is a valuable tool for improving farm-level water management because of its excellent crop yield simulation under full, deficit, and supplemental irrigation. The present study evaluated the AquaCrop model over two years of experimental data for the Zayandehrud rice cultivar on research conducted in the Nekuabad irrigation network, which features clay soil texture and mildly saline water. The irrigation treatments consist of continuous flooding to depths of 22 and 35 mm and alternative wetting-and-drying soil saturation levels from 0 (saturation) to 15 mm in depth. The model was able to accurately simulate rice yield under full irrigation and mild deficit irrigation scenarios. Increasing the water stress decreased the accuracy of model simulation for grain yield and canopy cover. The results of the reliability indices were 1.03 for root mean square error, 0.71 for index of agreement, and 0.6 for coefficient of residual mass. The model provided excellent simulations of grain yield, biomass and canopy cover. The best fitted curve for the crop water production function for the cultivar and region was a second-order function with an acceptable coefficient of determination of R2 = 0.91.

This research investigated the effects of fertigation on the uniformity of distribution of water and nitrogen for furrow irrigation and compared them to the results of field measurements from Abbasi et al. model output. This large-scale experiment was carried out as once-split plots in a randomized complete block design with three replications over 25 ha2 of newly-planted sugarcane planted by Dehkhoda Sugarcane Agro-Industry from February 2012 to October 2013. The main factor was split application of fertilizer (1, 2, or 3 applications during the growing season). The secondary factor was fertilizer application level at 100% (350 kg urea), 80% (280 kg urea), and 60% (210 kg urea) of fertilizer requirements. The coefficients for the Kostiakov infiltration equation were derived using the volumetric balance model. The Abbasi et al. fertigation model was implemented to simulate water flow and nitrate transport in soil. Fertilizer injection time was 30% to 60% of total irrigation time. Proper management of the inlet discharge and appropriate selection of fertilizer application times and frequencies increased distribution uniformity for the water and fertilizer. The E statistical index was greater than 0.990 for all fertigation treatments, indicating good performance of the model for prediction of advance and recession times. Comparison of the means for advance and recession times using the t-test showed that t < 2.447 (critical t) for all treatments, indicating good performance of the model. The t-test for discharge and uniformity coefficients for water and fertilizer showed that t > 2.305 (critical t), which suggests that flow rate had a significant effect on water and fertilizer distribution uniformity. The Abbasi et al. model improved water use efficiency and fertilizer distribution uniformity by optimizing the model inputs for infiltration parameters, inflow rate, and field slope. The results of field measurements and model prediction were more similar to the last fertilizer application times than to other treatments. The discrepancy of infiltrated water depths obtained from both methods was about 2 mm for the 4-application treatment with the 60% fertilizer level during the 11th irrigation and the 3-application treatment with the 100% fertilizer level during the 10th irrigation treatment. For these treatments, distribution uniformity of fertilizer increased more than did water distribution uniformity (> 90%).

This study investigated the influence of type and structure of starch components on the cooking quality of Iranian rice varieties. Six traditional Iranian rice cultivars were harvested, their drying and moisture contents were adjusted, they were milled and their white grains and flour were evaluated in a completely randomized design. The starch properties of amylose content, gelatinization temperature and gel consistency were measured. Characterization of polymeric structure of amylose and amylopectin was evaluated using chromatographic methods. Although there was little difference in amylose content, gelatinization temperature and gel consistency, the results showed significant differences at the 1% level for amylose and amylopectin hot water-soluble components and degree of polymerization. The rice varieties of good quality were Hasansaraee, Tarom and Domsiah; these showed higher hot water-soluble amylose content in results of size exclusion chromatography. The chain length distribution of amylopectin chains and the degree of polymerization were determined by capillary electrophoresis. Selected varieties showed significant differences for A, B1, B2, B3 and longer chains at the 1% level. The results showed that good quality cultivars, such as Domsiah, had more short chains (A) with less polymerization. There was no difference between the B1 and B2 chains by cultivar. The greatest difference was found between short chains (A), B3 and long chains. Differences in the polymeric structure of rice grains also should be considered to obtain more accurate analysis and new insights into quality.

Most cereals, especially wheat, contain nutrient-rich compounds such as minerals, dietary fiber, vitamins and amino acids in the outer layer of the grain (bran). The nutritional benefits of wheat bran, which is rich in dietary fiber, are well-known. The increasing use of pesticides in wheat culture and the consumption of diets high in wheat bread cause concern about pesticide residues in the bran, bread and other cereal products. This study determined the level of pesticide residue in wheat bran and the effects of the processing methods of hot and cold hydration, cooking and hydrothermal processing in acetate buffer solution on pesticide residue. The results indicate that all four treatments decreased the level of pesticide residue for deltamethrin (0.16 ppm), captan (0.315 ppm), bromopropylate (1.16 ppm), fozalon (1.807 ppm) and tetradifon (0.017 ppm) to minimum levels. It also decreased the phytic acid content of wheat bran samples 33%-83%. The decrease in pesticide residue and increased in nutritional quality, especially of vitamins, minerals and dietary fiber, are the main advantages of processing wheat bran using the methods tested in this study.

The tomato is a climacteric vegetable crop with high capacity for production of ethylene. Approximately 30% of the crop is lost in the consumption chain during harvest. In this study, two concentrations of nano-TiO2 in the form of TiO2 slurry were applied to tomato containers to evaluate ethanol, acetaldehyde and off-flavor decomposition in the storage atmosphere of tomatoes. The Halil tomato cultivar was harvested at the red stage of ripening for use in this study. The results showed that the TiO2 in the presence of UV light and proportional to the concentration can remove up to 85% of ethylene gas and 100% of ethanol and acetaldehyde from the tomato storage atmosphere. The extent of ethylene, ethanol and acetaldehyde removal caused by TiO2 photo catalytic reactions depended on the TiO2 concentration. A test panel determined that off-flavors were present in the storage atmosphere of the control treatment at 4 d after storage and was highest at 10 d. Off-flavors were not present in the storage atmosphere treated with 5g/l TiO2 at 8 d. At the end of 12 d of storage, the lowest level for off-flavor was detected in this treatment.

This study designed and built an electronic control system to control the chemical concentration of the spray solution in a crop sprayer. The system consisted of a speed sensor, a chemical metering pump, driver, and rotating speed sensor, mixing unit, and electronic control unit. The sprayer provided site-specific crop management after installation of the system on a field sprayer. The direct injection system changed the volume of the mixed chemicals in the carrier fluid (water) to change the concentration of the spray solution. The effects of spray solution pressure and rotational speed of metering pump on pump discharge were evaluated in laboratory testing. A regression relationship was observed between the dependent variable (metering pump discharge) and independent variables. In farm tests, the prescriptive map for concentration of spraying solution was first developed using ArcGIS software. The effects of travel speed (3, 6, and 9 km/h) and spray pressure (3, 4, and 5 bar) on spray concentration error of the first and last nozzles on the right-hand side of the sprayer boom were evaluated. The results showed no significant effect for pressure of sprayed solution and travel speed of the machine on the error of sprayed solution concentration of the first nozzle. The effect of travel speed of the machine was significant on the error of the sprayed solution concentration of the last nozzle. The mean sprayed solution concentration error of the first nozzle was 2.71% and of the last nozzle was 3.56%.

Nitrogen (N) is an important agricultural input that affects plant growth, yield and quality. Different crop sensors have been developed to detect the nitrogen status non-destructively content crops. The present study compared the performance of the Crop-Circle and Isaria crop sensors to estimate the nitrogen content of winter wheat during the growing season. The sensitivity of sensor measurements to the water content of the crop was also investigated. Field testing was conducted during the 2012 growing season at Marquardt experimental station northwest of Potsdam, Germany. The experiment was designed as a randomized split block design with two replications. Treatments consisted of four N fertilization rates (0, 60, 120 and 240 kg N ha-1) and two water regimes (irrigated and non-irrigated). The results indicated that both Crop-Circle and Isaria crop sensors showed very high performance for detection of the nitrogen content of winter wheat. It was noted that the measurements by Crop-Circle were affected by the water content of the crop, but that Isaria showed low sensitivity to water content.