Iranian Journal of Soil and Water Research
Year:2011 | Volume:42 | Issue:1|Papers Count:16

A prediction of maximum monthly rainfall is indispensable for management of agriculture and for management of water resources. Previous studies have demonstrated that see surface temperatures affect rainfall in their surrounding regions. In this study the relationship between sea surface temperatures of Persian Gulf and that of Red sea, and maximum monthly rainfalls recorded at Illam meteorological station and also the possibility of using these temperature data for a prediction of rainfall were investigated. A forty five year data set of monthly temperatures of the above seas surfaces along with monthly rainfall records at Illam Station were employed for the purpose. The index confidences of the relationship between each see surface temperature at Persian Gulf and Red Sea surfaces and maximum monthly rainfall were calculated as more than 60 percent. This indicates the high correlation between these two sets of data. The results finally reveald that, maximum monthly rainfalls can be predicted using the above two sea surface temperatures with an index confidence of 66.8 percent and with one month lag times.

Reference evapotranspiration is an important parameter in irrigation systems' design that is evaluated through either direct (Lysimeter) or calculated method (Empirical equations). When there is a lack of lysimeters' data, Penman Monteith FAO method could be employed as a standard method for evaluating the other empirical methods' results. In this research, 13 year evaporation pan data of Amol Station are multiplied by the calculated pan coefficient from such different equations as Cuenca, Allen Pruitt, Snyder, modified Snyder, Orang and FAO and then the results compared with Penman Monteith FAO Methods' results. The sensitivity of models with variations of ±10, ±20, and ±30 percent in such input parameters as wind velocity and relative humidity is then analyzed. Regression and statistical analysis showed Cuenca, Snyder, Allen Pruitt, Orang methods as recommended for estimation of daily ET0 from pan evaporation data. Cuenca, Snyder, Allen Pruitt methods are suitable for 10 day duration period ET0, while Snyder, Cuenca, Allen Pruitt for monthly ET0. The results of sensitivity analysis show that the sensitivity of the methods Orang, Allen Pruitt and modified Snyder in relation with input parameters is less than that of other methods. Statistical and sensitivity analyses show that Allen Pruitt and modified Snyder methods are the suitable ones for an estimation of pan coefficient in Amol and in areas that are of similar climatic condition.

Drought is among the natural disasters that causes heavy damages to water resources and makes managers face serious challenges. Drought monitoring is one of the important measures to manage droughts. Different indices and methods employing varied indicators, have been developed in this regard. In this paper it is aimed to compare two well-known meteorological indices of SPI and EDI with a hydrological method, based on reservoir level, to monitor drought in the Zayandeh Rud water system. Towards this, the 1998-2001 droughts, as the severest drought spells within the recorded data are applied for the evaluations. The results indicate that each of the methods has its own capability that can be helpful for water managers. Therefore, a simultaneous application of the indices is emphasized. As for the study area, the results suggest that SPI works well for drought onset and early warnings. The hydrological approach is found as more relevant during the drought, when operational measures should be implemented. Finally, it is EDI that responds more slowly to precipitated rainfall and more safely pronounces the drought end.

Proper irrigation scheduling, i.e. timely and adequate irrigation is an important prerequisite to profitable crop production. High temperatures along with soil moisture deficits are some of the main limiting factors for Canola (B. Napus L.) production in dry land cropping systems. These factors negatively affect the formation of pods during the flowering stage, resulting in decrease in seed yield. This experiment was carried out to determine the rate of water consumption, and come up with a proper irrigation scheduling of canola crop in semi-arid conditions of Bushehr province. The experimental design was an RCB one with four irrigation treatments (irrigation after 50, 70, 90 and 110 mm of cumulative evaporation from class A pan ) in three replications from 2001 to 2003 in Agricultural Research Station of Bushehr. The results revealed that by increasing the irrigation interval, seed yield, oil yield and water use efficiency decreased, but no significant difference was observed between 50mm and 70mm treatments. However, treatment 70 mm is recommended because of lower water usage, leading to more feasibility for the growers. In General, the results of the study indicated that for seed yield of 1.2 t/ha, oil yield of 545 Kg/ha and WUE of 2.1 kg/m3, it is required to use 561mm of water (including the effective rainfall) through at least 10 times of irrigation or rainfall events with 50 mm each time during the growing season.

Uncertainty is undoubtedly an inevitable part of programming process. A lot of effective factors in the water resources’ performance are not deterministic while their values are surely needed for the design and implantation of water systems. Since an optimal design of water distribution systems is in demand of a just evaluation of the costs, efficient operation of such systems calls for a proper evaluation of their efficiencies. Hereby, the performance of pipe networks, considering simultaneous uncertainty of nodal demands and pipe roughness is assessed in this research. The flexibility of the designed Two-Loop water distribution network along with simultaneous probabilistic changes of nodal demands as well as pipe roughness coefficients are evaluated, calculating a deterministic efficiency factor in Monte Carlo simulation method. Moreover, the variation of nodal demand and pipe roughness coefficient in the considered network is assessed. The results indicate that in a state of simultaneous changes in demand and in roughness coefficient, the Two-Loop network is able to supply consumers with the desired demand and at the required pressure, only approximately in one third of the cases.

Weather data generators (WGs) have been developed for an extension of time series of such weather variables as rainfall, temperature and relative humidity to provide better understanding of systems affected by climatic factors. Different algorithms have been applied in these generators, broadly divided into parametric & non-parametric ones. In this study, the performance of non-parametric generator of K-nearest neighbor (KNN) with the capability of extrapolating data, has been evaluated in six synoptic stations of Iran namely; Tehran, Qazvin, Mashhad, Bushehr, Tabriz and Rasht for the period of 1961-2005. Besides, some of the obtained results have been compared with parametric generator of LARS-WG to show the priority of this approach to parametric methods. The results revealed that in most cases the KNN approach presents a better performance in simulating the parameters of observed series; however, LARS-WG better performs in simulating length of wet and dry spells but with minor differences.

Because of a lack of means to match the traditional operating rules and regulations with time dependent variant of water needs in the present irrigation networks, a considerable portion of available water is wasted in these systems. This makes research on methods of operation and determination of types of controls as well as optimization approaches, attainable through using hydrodynamic models along with executing control systems, become indispensable. In this study, while criteria for control systems design is introduced, three control algorithms for Aghili irrigation network have been developed. Proposed control algorithms have been: (1) Local Upstream Proportional Integral Feebback Control, (2) Distant Downstream Proportional Integral Feebback Control along with Decouplers, and (3) Distant Downstream Proportional Integral Feebback and Feedforward Control along with Decouplers. The control algorithms programmed in MATLAB m-files in connection with the SOBEK simulation model. In all the controllers, first order low pass filter was applied for decreasing the effect of water resonance throughout the reaches of the canals.

The objective in this study was to assess the performance of the control algorithms and determine the appropriate controller for Aghili Irrigation Network. To evaluate the efficiency of the control algorithms, the performance criteria of the Maximum Absolute Error, Integral Absolute Error and Steady State Error were considered during the simulations of a one month period and with regard to the real offtakes schedule. The results demonstrated that the three proposed control algorithms benefit considerable potentials to closely match the discharge at the cross regulators with those by water users, with their leading to demand oriented water distribution and a better performance of the system. The proposed algoritms were ranked as: Distant Downstream Proportional Integral Feebback and Feedforward Control with Decouplers (algorithm 3), Distant Downstream Proportional Integral Feebback Control with Decouplers (algorithm 2), and Local Upstream Proportional Integral Feebback Control (algorithm 1) in providing a desirable performance; and as: algorithm 1, algorithm 2, and algorithm 3 to render high feasibilities. An integrated control system, controller 3 as the main control system along with controller 1 as the backup system are recommended as the desired control systems in the canals of Aghili Irrigation Network.

The experiment in this study was conducted as a completely randomized block design with ten treatments and four replications. Treatments included: To- control, T1- 50g of Zn per tree as broadcast application, T2-100g Zn per tree, broadcast application, T3- 200g Zn per tree as broadcast application, T4- 50 g Zn per tree as band application, T5- 50g Zn per tree, band application, T6-100g Zn per tree as band application, T7- foliar application with concentration of 2kg ZnSO4 in 1000 lit of water, T8- foliar application with a concentration of 3kg ZnSO4 in 1000 lit. water, T9- foliar application with a concentration of 3kg ZnSO4 in 1000 lit. of water. Results of the experiment with Satsuma mandarins indicated that zinc application increases fruit yield and also leaf zinc concentration significantly with the highest yield and leaf zinc concentration coming from treatment T9. The effect of the rates and methods of application of zinc sulfate on fruit was evaluated and reported.

Soil compaction is considered as a major threat to long-term productivity of agricultural soils. Two important mechanical properties which can be obtained from the log (stress) - strain curves of compression are: pre-compaction stress (?pc) which is assumed as a transition point between soil elastic to plastic behavior, while the other is the slope of Linear Virgin Compression (VCL) curve at higher stress, called compression index (Cc). Pre-compaction stress and compression index of a silty clay loam soil under long-term (seven years) application of organic matters (municipal solid waste compost, fresh air-dried sewage sludge, farmyard manure) at four rates (0, 25, 50 and 100 Mg ha-1) and one inorganic fertilizer combination (250 urea Mg ha-1and 250 ammonium phosphate Mg ha-1). These mechanical properties were determined at two gravimetrical Water Contents (WCs) (17.1 and 20.9% WC) on remolded soil samples. The experimental designs consisted of: 1) factorial design (organic manure type ? organic manure rate) and 2) orthogonal contrasts: i) control with inorganic fertilizer treatment and ii) control and inorganic fertilizer with factorial group in a completely ranomized design of three replications. With an increase in Organic Carbon (OC), the increase in bulk density (BD) after soil compression and at both WCs was lower. The least increase in bulk density was observed in soil amended with 100 SS ha-1 at WC of 17.1%. At the same WC, the apparent ?pc of the soil amended with high rates (50 and 100 Mg ha-1of organic amendments had higher values as compared with control. For high water content (20.9%), a linear and negative relationship was observed between soil OC and Cc, whearas the relationship for 17.1% WC was found as not significant. The decreases in pre-compaction stress and compression index, for the inorganic fertilizer were not significant as compared with control. In general, since with an increase in OC, the stress at compaction threshold is increased and soil susceptibility to compaction decreased at high water contents, therefore, it can be stated that a long-term incorporation of manure into soil at high rates, irrespective of manure type, could be employed as a means to increase soil resistance to compaction in central Iran.

The functions employed in an estimation of costly measured soil properties from either widely available or more easily obtained basic soil properties are referred to as pedotransfer functions. To develop pedotransfer functions, one can use multivariate regression, neural networks and neuro-fuzzy models. To make a comparison among the mentioned models, 153 soil samples were collected from soils in Rasht Province. Clay, sand, silt as well as organic carbon percentage considered as readily obtainable parameters vs. cation exchange capacity as predicted variable were assessed. The data set was broken into two subsets for calibration (80%) and testing (20%) of the models. According to some such evaluation parameters as Root Mean Square, Average Error and Coefficient of Determination, neuro-fuzzy benefited from the most accuracy for a prediction of cation exchange capacity. Also, results indicated that the neuro-fuzzy model increased the accuracy of cation exchange capacity prediction for about 14%. Following neuro-fuzzy model, artificial neural network (Feed forward, General Regression Neural Network, and Cascade Forward) benefited from higher accuracies than Multivariate Regression approach.

Boron toxicity is becoming more extensively widespread in arid and semi-arid regions, due to the application of either saline waters or irrigation waters containing a relatively high B content. Results of research indicate that addition of certain plant nutrients such as N may reduce the harmful effect of high B levels. Therefore, the present experiment was undertaken to evaluate the interactive effect as of N and B on the growth and chemical composition of rice in a calcareous soil. Treatments consisted of six B rates ( 0, 2.5, 5, 10, 20 and 40 mg kg-1 as boric acid) and four levels of N ( 0, 75, 150 and 300 mg kg-1 as urea) arranged in a factorial manner in completely randomized design of three replicates.Application of B decreased shoot dry matter. In treatments with low B concentrations, N application alleviated the toxic effect of B. In the absence of B, application of 300 mgN kg-1 of soil caused an increase in dry matter weight by 55% as compared with control plants. Minimum of dry matter weight was in the absence of N with addition of 40 mg B kg-1 of soil (N0B40). Moreover, it was observed that the addition of B increases B and N concentrations in the aerial parts of the spinach plant. The N concentration increased while B accumulation decreased with increasing N rates. Application of N and B increased proline concentration in fresh leaf. Chlorophyll concentration decreased with increasing B levels. N fertilization increased chlorophyll content and somewhat reduced the adverse effects of high B rates on this plant parameter. There was a general trend of increase in chlorophyll concentration in fresh leaf with increasing chlorophyll meter readings. Application of B decreased mean Ca: B ratio in the spinach shoot, significantly due to B concentration getting increased with increasing B rates. But at all B levels, there was a general trend of increase in this ratio with application of N. The results reported herein show that in soils with high B levels, N application may alleviate the suppressing effects of B toxicity and increase rice growth, possibly due to a diminishing trend in B absorption by the plant.

To determine the coefficients of c1 and c in Mitscherlich-Bray equation, critical level and fertilizer recommendation for potassium (K) as by Mitscherlich-Bray (MB) equation, an experiment in a randomized complete block design of 5 treatments and 3 replications was carried out in 12 irrigated wheat (Triticum aestivum L.) fields in Sarpol-e-Zohab region during the 2007-08 growing season. The treatments included T1 = Farmer's conventional fertilization practice= NP); T2 = control (all the nutrients included except K); T3 = T2 + 100 kg ha-1 muriate of potash (MOP); T4 = T2 + 200 kg ha-1 MOP and T5 = T2 + 300 kg ha-1 MOP in three stages of: preplanting, tillering, and stalk bearing. Following harvest, grain yield was determined, and MB Equation's coefficients for K calculated. The value of c1 coefficient for the 11 wheat fields was found as 0.0020. Potassium critical level was 115 mg kg-1 for 85% of the maximum yield under non-subsidized, i.e., free market fertilizer prices condition. However, under existing subsidized fertilizer prices, potassium critical level achieved for 95% of maximum yield was 180 mg kg-1. Therefore, based on the information obtained, the managers of soil test laboratories will have a suitable tool in predicting the farmers' relative yields and economic return on wheat with each incremental increase in K-fertilizer application just only by analyzing the available K in the soils. There is need for such information also for other regions and for other different field crops.

Soil quality is the most suitable index to an assessment of the stability of terrestrial ecosystems, especially agro-ecosystems. To determine the effects of agricultural practices on soil organic matter, species richness and abundance of soil invertebrates, a study was conducted in three regions of Razavi and Northern Khorasan Provinces, Iran. Soil were taken from in each winter wheat field of the study area, and as well from some samples selected areas of the natural ecosystem. Soil texture, organic matter, diversity in and abundance of soil invertebrates were determined. The results showed that climate affects soil texture as well as organic matter, so that with increase in mean annual precipitation and a decrease in mean annual temperature, soil texture was finer and soil organic matter increased. Organic matter was affected by agricultural practices and followed increasing trend with in agricultural systems going on in each region. Also diversity and abundance of soil invertebrates increased with prevalence of agricultural systems. As a whole, we suggested that soil quality increased in agricultural systems.

A significant portion of manganese (Mn) chemical fertilizers applied to calcareous soils is not absorbed by the first crop and may, therefore, affect the growth as well as chemical composition of the subsequent crops, this being called the residual effect of Mn, Soil tests may be employed to predict such effects. The present experiment was conducted to study the residual effects of manganese sulfate on the subsequent crop of soybean (Glycine max L.). Twenty soils of northern Iran (5-39% calcium carbonate equivalent), previously treated with two levels of Mn (0 and 30 mg Mn kg-1 as MnSO4) and under a single crop of soybean, was used in greenhouse to grow a second subsequent crop of soybean with no additional Mn fertilizer but with a uniform application of nitrogen, phosphorous and potassium. Soils were sampled before the subsequent crop and extracted through Mn extractant DTPA. Dry weight of plant tops as well as Mn concentration and uptake after eight weeks under the greenhouse conditions were used as the plant responses to residual Mn in soil. Statistical analyses showed that manganese sulphate application significantly increased the dry matter from 16.56 to 20.29 g/pot. Manganese application also increased leaves' Mn content as well as Mn uptake from 115 to 120.20 mg/kg vs. from 1.98 to 2.45 mg/ pot., respectively. The overall effects of previously applied Mn on dry matter were not significant, whereas seed yield, as well as Mn uptake were significantly increased. In all the soils, grain yield increased by 7.67% in comparison with control. The residual effects of Mn on dry matter and seed yield of the third crop on these soils were non-significant, but Mn uptake increased by 8.19% in comparison with control. In the fourth crop, the residual effects of Mn on dry matter , seed yield , Mn concentration and Mn uptake were found to be of no significance.

In this research 220 rhizobial bacteria were isolated from two lentil dryland farming flat plains of Moghan and Koohin. They were then tested in vivo as well as in vitro to make assurance of 184 purified strains of rhizobium leguminosarum biovar vicial (lentil). BTB +YMA culture media with different levels of salinity through NaCl (10, 20, 30, 40, 50 dS/m) application were used in salinity tolerance test of lentil rhizobial symbiosis strains. Among the 189 rhizobial strains, 101 were found out to be completely sensitive (EC=10 dS/m), 25 were very tolerant while 10 were classified as super strains, because of their being completely tolerant to salinity. The numbers of Koohin flat plain nurtured rhizobial strains in five salinity levels (in the range of 10 to 50) were respectively 55, 51, 50, 27, 37 while for Moghan flat plain , these numbers were recorded 46,42, 21, 8 and 8, Altogether Koohin flat plain rhizobacteria were more highly salinity tolerant than Moghan flat plain rhizobacteria. Drought tolerance test of rhizobial strains was performed in PEG 6000 +YMA culture media. The drought levels were evaluated as based on optical density of bacterial suspensions prepared for the test. Drought tolerance of rhizobacteria were grouped in 4 levels of completely tolerant, tolerant, sensitive and completely sensitive by as judged through respective optical densities of OD<0.3, OD=0.3-0.4 OD=0.4-0.5, OD>0.5. From among the 10 super strains(completely tolerant) identified, 6 from Moghan flat plain, and 2 super strains from Koohin flat plain were selected. At last it is hoped that the super strains (salinity and drought) identified in this phase of research can be effectively used in later greenhouse studies.