Agricultural Sciences and Technology
Year:2007 | Volume:21 | Issue:2 (SPECIAL ISSUE IN SOIL, WATER AND AIR)|Papers Count:19

Incorporation of plant residues in soils is an important agricultural practice for maintaining soil fertility under organic management systems. Plant residues quality, soil physical and chemical properties, and the microbial population diversity of soils are the most important factors influencing the decomposition of added organic matter to soils. Decomposition rate of wheat, alfalfa and tomato residues was studied in two different soil samples with contrasting texture under laboratory condition.Soil moisture was adjusted at 50% water holding capacity and soil samples were incubated at 25 oC. The CO2 production was used as an index for decomposition rate of plant residues. Result showed that decomposition rate of alfalfa residue was higher than those of tomato and wheat residues.The CO2 evolution data and the rate of plant residual decomposition fallowed y = a0 + a1 x e(x/a2) , and V= - A.e(-kt) equations respectively. The results also showed that there was a good correlation between decomposition rate and K. The K value for wheat, alfalfa and tomato residues was 0.02, 0.075 and 0.061, respectively.

Sulfur oxidation in soil, reduces soil pH, increase nutrients solubility and provide sulfate for plant growth. Among sulfur oxidizing microorganisms Thiobacillus spp and heterotrophs could have the potential to sulfur oxidizing in arable soils (four groups acidophilic and neutrophilic heterotrophic and acidophilic and neutrophilic autotrophic).Two soil samples containing all four groups of sulfur oxidizing microorganisms were selected. The factorial experiment in complete randomize design established with four factors, which consisted of sulfur rates (2 levels), time (5 stages), soils (2 samples) and organic matter (2 levels), which have been done in three replications.At 5 time stages population of four groups sulfur oxidizing microorganisms, pH and value of sulfate productions were measured. Results indicated that after application of 0.2% sulfur, population of all four groups of sulfur oxidizing microorganisms was significant (p<0.01) increased, Also after application of 1.5% organic matter population of heterotrophs sulfur oxidizing microorganisms was increased and population of autotrophs sulfur oxidizing microorganisms was decreased.Results showed that after 20 and 80 days population of total heterotrophs and total autotrophs reached to maximum level. Study of microorganisms change trend and sulfate production trend in soil showed that efficiency of autotrophs microorganisms to sulfur oxidation and produce of sulfate is higher than the heterotrophs, also significant correlation (p<0.01) between soil sulfate concentration and population of autotrophic microorganisms specially neutrophilic autotrophs was observed.

Rainfall is considered one of the most important climatic parameter. Forecasting and prediction of this parameter for a region or watershed is of prime importance in optimal consumption of water resources. It may play a marked role in micro- or macro-programming. Simulation of rainfall behavior, especially in recent years, is treated more scientifically. Seasonal multiplicative of Box-Jenkins algorithm is one of the accepted theories for monthly rainfall modeling. In such modeling, monthly rainfall is considered as a function of (a) previous months rainfall amounts (b) present, past and future months rainfall amounts for last year, and (c) a random noise. In this research long period (1951-2000) time series of monthly rainfall of Mashhad synoptic station was considered. Sample autocorrelation (SAC) and sample partial autocorrelation (PSAC) functions were analyzed. All possible algorithms were tested for normality, randomness of residuals, correlations of model parameters, and Port-Monteu test. Finally, SARIMA (1, 0, 0) (0, 1, 4) 12 was determined as the optimum algorithm.Based on this model, monthly rainfall amonts were predicted for the period of 2001-2003 with acceptable precisions. The results showed that the model did not change under three different 50, 40, and 30 record lengths. Yet there were some differences between actual and predicted rainfalls corresponding to low record length periods.

The application of organic residues, LECA (light expanded clay aggregates) and zeolite as mulches or incorporated in the top soil influences the soil water behaviour, temperature regime and mechanical resistance. A field experiment (2002 - 2003) was carried out in order to investigat the physical aspects of compost, LECA and zeolite incorporation and the compost as a mulch. Soil water content and soil temperature were determined during these experiments. It was concluded that compost as a mulch effectively conserved water and reduced soil temperature.

In addition to various mechanisms through which Plant growth promoting rhizobacteria (PGPR) stimulate plant growth, they can also do this job through producing the enzyme of 1- aminocyclopropane-1-carboxylic acid (ACC) deaminase. ACC deaminase containing rhizobacteria by utilizing ACC which is the immediate precursor of ethylene biosynthesis in higher plants and exudated from roots and seeds, can modulate ethylene levels which is increased in respond to environmental stresses and called stress ethylene. Some strains of rhizobia are also able to produce ACC deaminase. This project was done in order to study the ability of ACC deaminase production in some strains of rhizobia, indigenous to some soils of Iran and finding super strains among them.In this research, 100 isolates of rhizobia were cultured on Rhizobial Minimal Medium (RMM) with two different sources of nitrogen (ACC and ammonium chloride) and a control with no nitrogen at all. Results showed that 65% of strains could produce ACC deaminase and were divided into three groups of strong, mild and weak due to their colony diameter. All strong strains and most of mild ones belonged to Sinorhizobium meliloti. Other strains mostly belonged to weak division. S. meliloti had a good ability to produce ACC deaminase among all tested strains.

The present study has been conducted to investigate the spatial and temporal variation of fitted distributions to the erosivity index. In order to detelmine the Erosivity Index proposed by Wischmeier and Smith, kinetic energy was firstly calculated for the study storms and then interacted with the maximum 30 minutes intensity. To achieve the study purposes, six meteorological stations viz.Kassilian, Babolsar, Kashan, Bostan, Booshehr and Gachsaran were selected for a common period of 19 years. The Erosivity Index was then calculated in monthly, seasonal and annual time scales.The different statistical distributions were fitted to the calculated values using SMADA software.The goodness of fit of study distributions was assessed based on RSS in different time scales. The final evaluation was then made with the help of factor scoring and classification of RSS. The results of the study revealed that the best fitted distribution for erosivity index in monthly, seasonal and annual time scales were Log Normal and Gumbel, 3 Parameter Log Normal, Pearson and Gumbel, and Log Pearson, Gumbel and Pearson, respectivly. The results of the study also showed that the spatial distribution of erosivity data significantly affected the type of the distribution fitted to the data calculated for each particular meteorological study station.

Remote sensing is an efficient tools for monitoring and estimating of agriculture planted areas.Vegetation reflection properties and some indices are used for this. This study reports the results of estimating winter wheat planted area by using MODIS (one of the TERRA sensors) images, which are prepared for 16 days periods in three different spatial resolutions, 1000, 500 and 250 meters. The images have been used for winter wheat areas of Khorasan Razavi province (North East of IRAN) during agricultural season of 2004-05. Four different areas were selected for this study. These areas are wheat farm, mountain, dense vegetation cover and desert. Then some image processing techniques and statistical analysis were used to analysis this area. Afterward we produced the wheat planted map and calculating area of wheat. Our results showed that MODIS images (which are easily available) are an appropriate data for estimation and monitoring wheat-cultivated areas.

This paper presents the results of a comparative investigation of the abrasive wear of four common disk type tillage tools in Iran, at different soil texture, moisture content, and the speed of The tools.The samples were collected from Iranian market - two Iranian brands recognized as Araki and Shirazi - and two imported foreign brands known as Brazilian and Italian. To create a controlled workplace, a small scale soil bin (120 (100 (70cm) was constructed and used. The samples were fixed on a rotating shaft and driven by a tractor? s PTO through a drive train. This arrangement resembled the geometry and the movement of the samples in the soil. The experiments were conducted in three different soil textures (sand, loam and clay), three soil moisture levels and three rotating speeds of the shaft. Each experiment lasted for 48 hours. The least wear (2%) was observed for dry soils while the maximum wear (40%) was obtained for a wet sandy soil. While in the lower range of speed, in all soils, wear increased with increasing the speed, the higher speed reduced the rate of wear especially in less cohesive soils such as loam and sand, due to the scattering action of the tools at a very high speed. It was also observed that, in general, the wear resistance of the tools was proportional to their surface hardness. The highest wear resistance was measured for Brazilian and Italian samples respectively with no significant difference between them. Although the Araki had a lower wear resistance than the two foreign samples this difference was not significant. The least wear resistance was found for Shirazi samples. On the whole, from wear resistance and economical points of view the Italian and Araki samples were recommended for use.

In the last decades, replacement of resins with microbial biomass and exoceIIular polysaccharides for adjustment or removal of heavy metals from aquatic environment has been studied by many researches. For this reason, the most attentions were directed to the bacteria which produce more polysaccharides. In this investigation, the potential of adsorption lead (Pb), nickel (Ni), and zinc (Zn) by dried cell and exopolysaccharide of sinorhizobium bacteria which nodulate alfalfa was studied. The results showed that dried cells had less absorbing tendency compared to exopolysaccharide. Sinorhizobium exopolysaccharide adsorbed 89, 85 and 66 percent of Pb, Ni, and Zn from 150 mg L-l, solution of those elements, respectively. Maximum adsorption of Pb, Ni, and Zn sinorhizobium exopolysaccharide (MS-125 isolate) were 110, 54 and 94 mg L-l respectively which were extimated by using Langmuir model.

In order to examine the possibility of statistical models for seasonal rainfall forecasting based on synoptical pattern, the Khorassan provinces were selected as a studied area. To achieve this goal, data of 37 rainfall stations were used and the RUN TEST was performed to find out if the rainfall data were randomly collected. In the second stage, mean local time series of rainfall was calculated in Arc GIS software. These data were used to model the relation rainfall and sea level pressure gradient (SLP). Results showed that statistical models can predict the amount of rainfall of next season. Among the output of different models, the results of stepwise and backward models were much better than others.

This study was conducted to evaluate the effect of changes in irrigation water quality and quantity which applied for cotton in the Rudasht irrigation system in Esfahan. This was performed by using a physically based, well-tested SWAP simulation model for crop growth, water and salt transport at field scale. Results indicated that the current practice of 900 mm annual irrigation application rates for colton, with salinity level of 4 dS m-1. Different scenarios are studied based on changes in water quantity and quality and their effect on the water and salt balance and crop yields. The first scenario is the baseline scenario which describes the current situation and will function as a reference for the other scenarios. According to the results, an almost linear relationship exists between the amount of water applied by irrigation and the amount of percolation. Soil evaporation was also linearly related to the irrigation supply. Crop transpiration and relative yields reached their maximum level at an irrigation input of about 1000 mm. Increase in appled irrigation water to more than 1100 mm caused soil salinity levels decrease slightly, but deeper collation, water logging, and soil salinity increased.At the current practices, cotton yield in average was about 66% of the potential yield (5000 kg ha-1). An incease in irrigation water salinity to 6 dS m-1 caused cotton yield decreased to 51% of potential level.

in this study the impact of land cover change and flood spreading on runoff coefficient of variation and river flows of the Madian rud for four periods (1349-58, 1358-73, 1373-83 and 1375-83) are investigated.The results indicate that runoff coefficient of variation in periods (1349-58 and 1375-83) decrase and increase for two and tree prid (the annual average of 2.16 increases on run of coefficient of variation the mor others) Such that 2.37% to 10.04% increase and 15.3% to 2.8% decrease. saturation situation AMC(III) incondition on run off coefficat to 136% increase. The result indicate scs model increase twice as much runoff duto land cover change in priod (1373-83) Comparision of four scenarios the mor critical situation in scenario tree for the basin.

Penmam-Montheith (PM) model presented by Food and Agricultural Organization (FAO) internationally, estimate the reference evapotranspiration (ETo) based on climate data from metrological stations. Appling of the PM model requires converting input climate and site data into a number of parameters, and FAO-56 recommends exact procedures for estimating these parameters.The parameters are included wind speed at 2 meter height (U2) saturated vapor pressure (eS), actual vapor pressure (ea), net radiation at crop surface (Rn), slop of vapor pressure verses temperature curve at temperature T (D), psychometric constant (g). However, a plethora of alternative procedures for estimating parameters exist in literature. As a consequence, it is likely that ambiguous results maybe obtained from the FAO-56 PM model because of the adoption of such alternative supporting equations. The purpose of the present study is to evaluate differences that could arise in FAO-56 PM ETo estimates if non-recommended equations are used to compute the parameters. Using historical climate records from 1986-2005 of two stations located in the hot-dry and cold sub-dry regions of Ahvaz and Tabriz monthly ETo estimates computed by FAO-56 PM were statistically compared statistically with those obtained by introducing alternative procedures from parameters.Statistical procedures were included mean absolute relative difference (AMEAN) and maximum absolute relative difference (MAXE). Nine alternative algorithms for ETo estimation were formulated, involving modified procedures for parameters associated with Rn, ea, es, D, g, and saturated vapor pressure at air temperature (eo).According to the results, four of these algorithms yielded ETo estimates that were in close correspondence with FAO-56 estimates. Two of the algorithms showed different estimates for selected climates. The remaining three algorithms, involving nonrecommended procedure for the vapor pressure deficit and net radiation parameters, yielded considerably different ETo estimates, giving rise to AMEAN and MAXE values higher that 2% for the estimates. The results also highlighted the acceptable procedure for estimation of eo and y, and need for strict adherence to recommended procedures, especially for estimating vapor pressure deficit and net radiation parameters.

Liming is an effective agricultural practice for correcting soil acidity. By-products of steelmaking industry such as slag and converter sludge that have alkaline pH, could be used as cheaper liming material for increasing pH and amendment of these lands. So, for determination of these substances effects on soil chemical properties, a field experiment was established. This design was performed in 18 plots with 40m2 area, 6 treatments (0.5% and 1% slag, 0.5% and 1% converter sludge, 0.5% slag+0.5% converter sludge at dry soil weight unit and control treatment) with 3 replicates on tea rows using a completely randomized design (CRD). Treatments were mixed in 15 cm depth of soil in spring. After 2 months from mixing, soil sampling from 0-15 cm depths was done at 5 stages, every 45 days and. Application of slag and converter sludge treatments could act as liming material and increased soil pH significantly. Slag treatments caused more pH increase than converter sludge treatments and soil pH increased linearly with increasing rate of slag and converter sludge. All treatments significantly decreased available Al in soil. Soil Al decreased linearly with increasing rate of slag and converter sludge. All treatments significantly increased available Ca of soil. One percent slag treatment, showed the highest Ca concentrations. Soil Fe in all treatments, except 1% converter sludge treatment, showed significant decrease compared with control. In all treatments, DTPA-extractable Mn decreased significantly compared to control.

Using sprinkler irrigation is one of the effective ways of water resources management. If these systems properly design, perform and manage, they lead to decrease of water usage and increase of system's distribution uniformity.This investigation is performed to assess sprinkler irrigation uniformity coefficient at 3 pressure system (300, 350 and 400 KPa) and at 3 nozzle size (9/64"*3/ 32", 11/64"*3/32" and 13/64"*3/32") in various climatic conditions, on VYR 35 dual nozzle sprinkler in Mashhad. Also uniformity coefficient of 8 spacing (9x9, 9x 12, 9x 15, 12x 12, 12x 15, 12x 18, 15x15, and 15x18) and 4 settings (square, equal triangular, triangular and rectangular) were determined with simulating distribution pattern of a single sprinkler. Results show that pressure, nozzle size and wind speed has significant effect on uniformity coefficient. Uniformity increases with increasing of pressure, nozzle size and decrease of wind speed. Square and equal triangular have maximum and triangular and rectangular show minimum uniformity. Decrease of sprinkler spacing lead to increase of uniformity because of better water overlapping, but sprinkler spacing must be chosen upon economic analysis.

Saffron is the world's highest priced spice. High value and no need for summer irrigation are two main reasons that farmers include this spice in their cultivation pattern. However, some experts have indicated that summer irrigation may be useful for saffron. In an experiment, the effect of summer irrigation on yield of saffron was investigated. Experiment was conducted in lysimeter in Mashhad and followed by on-farm investigation in Torbat-e-Hydarieh. Four irrigation treatments were: (1) one irrigation in Tir, (2) one irrigation in Mordad, (3) two irrigation in Tir and Mordad, (4) no summer irrigation. The results of lysimeters showed that Mordad irrigation increased yield of saffron. Tir irrigation had no effect and two irrigation in Tir and Mordad decreased the yield. Onfarm research showed that summer irrigations with similar treatments had no effect on saffron yield. However, summer irrigations resulted sooner emergence of flowers after first Basar-Ab irrigation.

Evapotranspiration is a key parameter in water balance equations of hydrologic cycle. This parameter is used as potential (or reference crop) evapotranspiration. Different methods have been proposed to calculate reference crop evapotranspiration, which are almost different with each other with respect to data needs. In 1998, FAO proposed Penman-Monteith method as a standard method to estimate reference crop evapotranspiration. One of the important parameters in this method is net radiation, which should be calculated precisely. Since measuring devices for solar radiation are not installed in all meteorological stations, the net radiation is calculated from sunshine hours and extraterrestrial radiation. In the present research, the necessary coefficients (as and bs) were calculated for Isfahan region from long-term data. The results showed that as and bs were 0.267 and 0.488, respectively. The minimum and maximum difference between monthly evapotranspiration obtained from the newly coefficients and the ones suggested by FAO (i.e., 0.25 and 0.5) was 0.6 and 0.1 percent. So, the recommended coefficients by FAO could be used in Isfahan region.