Evaluation of surface irrigation system performance using System Dynamics (SD) approach

Various methods and criteria have been proposed and utilized for the evaluation of irrigation systems performance, which can be used for comparison of design conditions and irrigation systems performance. Surface irrigation systems should be paid more attention among all other irrigation systems due to their operation simplicity and high losses. In the present study, while describing main relationships of irrigation evaluation criteria of application efficiency, water requirement efficiency, Deep Percolation Ratio and Tail Water Ratio, a method based on SD will be introduced. Modeling of this approach has been done using VENSIM-DSS software. Model has been tested in a case study that included the modeling of a furrow in four irrigation status: current situation, full irrigation, deficit irrigation and finally deficit irrigation with optimized irrigation cutoff time and inflow into furrow. The results reveal the high capabilities of SD approach in modeling water resources and irrigation systems. Its user friendly and ability in transferring data to the data bank can introduce this approach and software as an applicable decision support system.     

Evaluation of furrow fertigation and model validation on maize field

In new agricultural practices, joint application of water and fertilizer has been become common. Uniform distribution of fertilizer in soil and in plant growth duration is possible by this procedure. The main objective of this study was to investigate furrow fertigation management effects on distribution uniformity and runoff losses of nitrate in a cornfield, and validate a numerical fertigation model. A field experiment was carried out with seed corn at 12 experiments with a complete randomized block design during 2 years. Nitrogen requirement was determined by soil analysis and accomplished in four stages of the growth: before cultivation, in seven leaves, shooting and earring stages which first section (before cultivation) was applied by manual distribution and others by fertigation. Potash and super phosphate fertilizers (based on soil analysis) were sprayed on soil before planting. Water requirement was estimated by using class a evaporation pan multiplied by plant (Kc) and pan coefficients. Nitrogen fertilizer was solved in irrigation water and injected at the last minutes of irrigation. The results showed that fertilizer distribution uniformity of the low quarter (DU_LQ) ranged from 85.7% to 91.5% in first year, and 69.9% to 95.5% in second year. While water DU_LQ ranged from 74.1 to 98.2% in 2 years. Nitrate losses of surface runoff have ranged between 5.7 and 42.0% in first year according to the application time and the outflow flux. In second year, the nitrate losses decreased by adopting appropriate management based on the experiences of first year. The fertigation model was subsequently applied to the experimental data and results showed good agreement with field data.     

GROWTH AND IRON-MANGANESE RELATIONSHIPS IN DRY BEAN AS AFFECTED BY FOLIAR AND SOIL APPLICATIONS OF IRON AND MANGANESE IN A CALCAREOUS SOIL

Manganese (Mn) deficiency may be induced by adding large quantities of iron (Fe), provided that soil manganese is marginally deficient. Results of a greenhouse study showed that iron soil application did not influence shoot dry matter yield of dry bean due to the fact that the iron:manganese ratio in aerial parts of dry bean was higher than 0.4. A foliar spray of 2% iron sulfate significantly reduced it probably due to the high level of shoot iron and iron:manganese ratio greater than 4. Iron application decreased concentration/uptake of shoot manganese due to the iron-manganese antagonistic relationships. Mangenese soil application is not an effective method in correction of manganese deficiency induced by iron fertilizers. Iron did not affect root manganese uptake, indicating that manganese absorption was not affected by iron application. Both manganese/iron soil tests are recommended in calcareous soils with manganese soil test in marginal range.     

Effects of emulsified versus saline administration of GnRHa on induction of ovulation in rainbow trout, Oncorhynchus mykiss

The effects of saline-dissolved or Freund's incomplete adjuvant (FIA)-emulsified GnRHa treatment on the induction of ovulation in rainbow trout, Oncorhynchus mykiss, were examined. The FIA-emulsified GnRHa was first diluted in 0.25 ml physiological saline and then mixed with an equal volume of FIA. Fish were selected in the beginning of the spawning season and were allocated into four groups and were treated intraperitoneally with (a) 0.5 ml of emulsified GnRHa (GnRHa–FIA), (b) 0.5 ml saline-dissolved GnRHa in a single injection (GnRHa-1), (c) 0.5 ml saline-dissolved GnRHa in two injections spaced 1 d apart (GnRHa-2) and (d) 0.5 ml of saline (Control). The GnRHa dose in all hormone treatments was 25 µg kg^− 1. All fish in the FIA–GnRHa and GnRHa-2 groups ovulated within 10 and 11 d after treatment, respectively. In contrast, only 75% in the Control fish and 60% of the fish in the GnRHa-1 group ovulated within 36 d after treatment. None of the treatments caused any pre- or post-spawning mortality in the broodstock. Fertilization, eyeing and hatching percentages of the produced progeny were normal in all the treatment groups and did not differ significantly among them. In conclusion, FIA-emulsified GnRHa can be effective in advancing the onset of and synchronizing the ovulation of rainbow trout within a two-week period, thus shortening the egg collection period, without affecting broodstock survival and egg quality.     

Herbicide risk assessment during the Wheat Self-sufficiency Project in Iran

BACKGROUND: The present study describes the quantitative changes in herbicide use during the specific observation periods in the Wheat Self-sufficiency Project in Iran from 1994 to 2004 and the associated changes in herbicide risk, area and yield in this context. A risk index, the environmental impact quotient (EIQ), was used to estimate the environmental impacts (EIs) of herbicides applied to wheat agroecosystems. RESULTS: The results suggest that, during this period, the overall risk posed by the herbicides applied to wheat agroecosystems increased substantially, as evidenced by a 71% increase in herbicide usage (weight of pesticide applied) and a 62.2% increase in EI rating, in spite of an 8.2% decrease in overall EIQ rating and an 89.2% decrease in mean application rate. Furthermore, a 0.57% increase in the area and a 23.6% and 22.7% increase in irrigated and rainfed yields, respectively, were observed. The results also indicate that the EIQ(FUR) of two herbicides, dichlorprop-P/mecoprop-P/MCPA and difenzoquat, is much higher than that of other herbicides, and they could be qualified as high-risk herbicides. CONCLUSION: As a whole, an increase in herbicide usage (weight of pesticide applied) was an important factor on herbicide environmental impact boost. However, this increase has not led to a similar increase in wheat yield, which could be attributed in part to the negative impact of high herbicide consumption in wheat fields and subsequent threat to the long-term sustainability of these agroecosystems.     

Field Evaluations of Yield,Iron-Manganese Relationship,and Chlorophyll Meter Readings in Soybean Genotypes as Affected by Iron-Ethylenediamine Di-o-hydroxyphenylacetic Acid in a Calcareous Soil

Iron (Fe)-deficiency chlorosis is a common constraint when soybean (Glycine max L.) is grown on calcareous soils. Considerable differences exist among soybean genotypes for susceptibility to Fe chlorosis. In order to evaluate the effectiveness of iron-ethylenediamine di-o-hydroxyphenylacetic acid (Fe-EDDHA) for three soybean genotypes (A3237, Black hack, and Wells), field studies were conducted for the years 2001 and 2002 in a calcareous soil. Although, available Fe of the studied soils was either lower than critical level or in marginal range, application of Fe-EDDHA did not result in a significant increase in soybean yield probably, due to the antagonistic relationships between Fe and manganese (Mn). It appears that Fe soil test as the only criterion for Fe fertilizers recommendation is not appropriate and soil test for Mn is also recommended. Significant quadratic equations were obtained between chlorophyll meter readings (CMR) in growth stage 3 (GS3) with seed yield (SY) of A3237 and Black hack. However, SY of Wells showed close relationships with CMR in growth stage 4 (GS4). A tentative conclusion is that the chlorophyll meter is a reliable and non-destructive tool for the prediction of SY for the studied soybean genotypes in GS3 or GS4.

Due to the fact that use of Fe fertilizer might cause nutritional disorder, use of Fe-efficient genotypes remains as an effective and economic sound practice. However, positive responses to Fe-chelate treatments are expected for genotypes with shoot Fe: Mn ratio less than 0.4 when both nutrients are in the sufficiency range. Obviously, such a requirement limits the utilization of Fe-chelate to post-emergence fertilization.     

Effect of cadmium toxicity on micronutrient concentration,uptake and partitioning in seven rice cultivars

Heavy metal uptake, translocation and partitioning differ greatly among plant cultivars and plant parts. A pot experiment was conducted to determine the effect of cadmium (Cd) levels (0, 45 and 90 mg kg^?1 soil) on dry matter yield, and concentration, uptake and translocation of Cd, Fe, Zn, Mn and Cu in seven rice cultivars. Application of 45 mg Cd kg^?1 soil decreased root and shoot dry weight. On average, shoot and root Cd concentrations and uptake increased in all cultivars, but micronutrients uptake decreased following the application of 45 mg Cd kg^?1. No significant differences were observed between 45 and 90 mg kg^?1 Cd levels. On average, Cd treatments resulted in a decrease in Zn, Fe and Mn concentrations in shoots and Zn, Cu and Mn concentrations in roots. Differences were observed in Cd and micronutrient concentrations and uptake among rice cultivars. Translocation factor, defined as the shoot/root concentration ratio indicated that Cu and Fe contents in roots were higher than in shoots. The Mn concentration was much higher in shoots. Zinc concentrations were almost similar in the two organs of rice at 0 and 45 mg Cd kg^?1. A higher Cd level, however, led to a decrease in the Zn concentration in shoots.     

Zinc sorption–desorption by sand,silt and clay fractions in calcareous soils of Iran

Zinc sorption–desorption by sand, silt and clay fractions of six representative calcareous soils of Iran were measured. Sand, silt and clay particles were fractionated after dispersion of soils with an ultrasonic probe. Zinc sorption analysis was performed by adding eight rates of Zn from 6 to 120 μmol g^?1. For the desorption experiment, samples retained after the measurement of Zn sorption were resuspended sequentially in 0.01 M NaNO₃ solution and shaken for 24 h. Results indicated that Zn sorption by soil fractions increased in the order clay > silt > sand, and correlated negatively with CaCO₃ content and positively with cation exchange capacity (CEC) and smectite content. Results indicated that for all fractions, the Langmuir equation described the sorption rates fairly well. In contrast to sorption, Zn desorption from soil fractions increased in the order sand > silt > clay, and correlated positively with CaCO₃ content, CEC and smectite content. Results showed that parabolic diffusion and two constant equations adequately described the reaction rates of Zn desorption. In general, for all soils studied, the coarser the particle size, the less Zn sorption and more Zn desorption, and this reflects much higher risk of Zn leaching into groundwater or plant uptake in contaminated soils.     

Performance of an automatically deployable ROPS on ASAE tests

In the U.S., approximately 132 agricultural tractor overturn fatalities occur per year. The use of rollover protective structures (ROPS), along with seat belts, is the best-known method for preventing these fatalities. However, one impediment to ROPS use is low-clearance situations, such as orchards and animal confinement buildings. To address the need for ROPS that are easily adapted to low-clearance situations, the Division of Safety Research, National Institute for Occupational Safety and Health, developed a prototype automatically deploying, telescoping ROPS (AutoROPS). The NIOSH AutoROPS consists of two subsystems. The first is a retractable ROPS that is normally latched in its lowered position for day-to-day use. The second subsystem is a sensor that monitors the operating angle of the tractor. If an overturn condition is detected by the sensor, the retracted ROPS will deploy and lock in the full upright position before ground contact. Static load testing and field upset tests of the NIOSH AutoROPS have been conducted in accordance with SAE standard J2194. Additionally, timed trials of the AutoROPS deployment mechanism were completed. The results of these tests show that the NIOSH AutoROPS has significant potential to overcome the limitations of current ROPS designs for use in low clearance as well as unrestricted clearance operations.     

Stabilization of lead as affected by various amendments and incubation time in a calcareous soil

The effect of different kinds of amendments including coal fly ash (CFA), municipal solid waste compost (MSWC), rice husk biochars prepared at 300°C (B300) and 600°C (B600), zero valent iron (Fe°) and zero valent manganese (Mn°) were evaluated to determine their ability to stabilize lead (Pb) in Pb-spiked soil. The Pb-spiked soils were separately incubated with amendments at the rates of 2 and 5% (W/W) for 45 and 90 days at 25°C. The efficacy of amendments treatment was evaluated by desorption kinetic experiment and sequential extraction producer. According to the results, with increasing time, considerable changes in distribution of chemical forms of Pb occurred and carbonate-bound fraction significantly decreased, while amorphous Fe-bound fraction significantly increased. The applied treatments efficiently decreased the mobility factor of Pb compared to control treatment. Application of Mn°, Fe°, CFA, MSWC, and B600 in soils significantly decreased Pb desorption rate with respect to control treatment. Biphasic pattern of Pb desorption kinetic was fitted well by the model of two ?rst-order reactions. In general, present study showed that from the practical point of view, all applied amendments (except for B300) were effective in Pb immobilization; however, application of Mn° at 5% (W/W) rate was the best treatment to immobilize Pb, so it can be recommended for the immobilization of Pb in calcareous polluted soil.