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سال:1381 | دوره:7 | شماره:2 |تعداد مقالات:13

In order to evaluate the effects of drought stress and defoliation on sunflower, a study was conducted under controlled conditions. Treatments were a combination of three levels of drought (100, 60 and 30 percent of Field Capacity (FC)) and three levels of defoliation (control, removal of either 4 or 6 leaves from lower part of the plant) laid out, in a Completely Randomized Design with four replications. Drought stress was applied from 4-leaf- stage up to the end of plant growth period while leaf removal was conducted at the heading stage. Results indicated that drought stress affected most of the measured parameters. Plant height, plant dry matter, stem diameter, head size, seed number/head, 100-seed weight and seed weight! Head declined upon drought stress as compared to control. SPAD readings increased as drought stress increased. Defoliation caused an increase in SPAD and a decrease in seed number/head. Leaf number was not affected by either drought or defoliation.

To find out how maize and potato can grow and develop in an intercropping system rather than each grown alone in a sole cropping system the following factorial experiment was performed in the frame work of a randomized complete block three replications in the experimental farm of the faculty of agriculture, Zanjan University in year 2004. Different potato to maize ratios of (1:0), i.e. sole potato; (3: 1) meaning 75% potato plus 25% maize; (1:1), that is half and half of each crop; 25 percent potato together with maize of 75% (1:3); and finally sole cropping of maize (0:1) were employed. Two plant population treatments of 3.8 and 5.3 plants/m2 were assigned to each crop. There was an increase observed in the radiation absorption and in Leaf Area Index (LAI) with an increase in plant density from 3.8 to 5.3 plants per square meter. Maximum potato yield (20390 kg/ha) was obtained from 3: 1 crop ratio and maximum yield of maize (8898 kg/ha) from the 1:1 ratio of intercropping system. In the case of potato the new cropping system (intercropping) there were significant (a= 0.05) observed in yield, mean number of branches per plant, as well as in mean weight of potato tubers. In maize, the cropping system revealed a significant effect on yield, mean number of ears per plant as well as on mean number of seeds per year. Land Equivalent Ratio (LER) was shown to be more than one for all the treatments indicating more profitability and superiority of intercropping to sole cropping system. The highest LER for either one of the crops in intercropping system was 1.58. This was obtained for potato in the 3:1 ratio treatment while for maize it was obtained for the treatment of 1:1 ratio.

Spacing between check dams depends on the stream bed slope, effective height of check dams and slope of deposited sediments behind the check dams. The slope of deposited sediments is more important than the other two factors because of complications in the way of its occurrence and its measurement after several years of dam construction. This research presents the effective factors affecting the slope of deposited sediments behind 60 selected check dams among 2000 evaluated ones in the watershed of Doroudzan Dam. Such factors as stream bed slope, slope of deposited sediments behind dams, height of check dams, width of stream on the dam site, sand, silt, clay, granule, pebble, cobble and D50 of sediments were assessed. Based upon the collected data three models: linear-logarithmic, modified linear -logarithmic and simplified linear-logarithmic, for determining the slope of the deposited sediments as well as the space between check dams were developed and compared The results showed the factors significantly affecting the slope of deposited sediments are: stream bed slope, height of check dams, stream width, sand, granule and D50 of sediments.

This research was conducted in Toroq Experimental field station, Mashhad, Iran, for two successive cropping seasons (2000-2002), using split plot experimental design based on complete randomized blocks with three replications. Moisture stress treatments (at seven levels) were assigned to main plots, including: D1 ( full irrigation), D2 (no irrigation from one leaf to double ridge) stage, and in other treatments, no irrigation and preventing rainfall as: D3 (from one-leaf to floral initiation stage), D4 (from floral initiation to the commencement of stem elongation or Terminal spikelet), D5 ( from commencement of stem elongation to flag leaf emergence), D6 (from flag leaf emergence to anthesis) and D7 (from anthesis to the soft dough), and four wheat cultivars, namely: Roshan, Qods, Marvdasht and Chamran, were sown in sub plots. The results of combined analysis of variance showed that the effect of moisture stress was significant. Applying D5, D6 and D7 treatments reduced the grain yield in comparison with control (D1) by 36.7, 22.8 and 45.6, respectively. Severe moisture stress treatments (D5 and D7) caused a reduction in water use efficiency (WUE) and radiation use efficiency (RUE), due mainly to reduction of dry matter. Based on these results, grains filling (D7) and fast growing (Ds) stages of wheat were more sensitive to moisture stress. Genotypic differences were also observed with respect to concerned characteristics. Chamran had a higher moisture tolerance, therefore, greater grain yield as compared with the other cultivars.

Decadal changes in land use/land cover for Balachaur watershed in Nawanshahar district, Punjab, India were studied using black and white aerial photographs for March 1984 on approximately 1:20,000 scale and multidate geocoded false colour composites (FCC) of IRS-1D LISS-III on 1:50,000 scale for March 2002, September 2002, and May 2003 and interpreted visually to prepare land use/land cover maps for the year 1984 and 2003. The results revealed that the area under crop land, moderately dense forest, degraded forest, degraded land in hills and piedmont plains, barren land along choes (seasonal streams) has decreased; whereas, the area under settlements, dense forest, plantations, industrial use, ponds, choes and brick kilns has increased over a span of 20 years. By virtue of afforestation and forest conservation, the density of vegetation in Siwalik hills and piedmont areas has increased. The area under moderately dense forest (1956.7 ha) and degraded forest (755.5 ha) got upgraded to dense forest while 755.5 ha of degraded forest changed to moderately dense forest. The impact of land use/land cover alterations on climatic variability at micro-level revealed that the linear trends computed for the 5-yearly moving average of maximum temperature showed an increasing trend from 1984 to 2003, whereas the minimum temperature, rainfall, and potential evapotranspiration showed a decreasing trend. Inspite of increasing forest cover in the study area, these trends in different meteorological parameters did not corroborate the findings of some earlier reports. Thus land use/ land cover changes over time may not be the only factor which causes variation in meteorological parameters. It implies that there might also be other factors such as CO2 concentration and its effect on green house gases, atmospheric pollution and spectral distribution of the incoming solar radiation, which affect climatic variability in a region.

Most aquifers of semi-arid regions in Iran suffer from over-exploitation of groundwater for irrigation purposes. It is therefore important to augment the groundwater resource by artificial recharge, using floodwaters. Generally, the recharge schemes consist of diverting part of the flood discharges of ephemeral rivers in small to medium-size catchments into infiltration basins. Apart from recharging groundwater, and supporting food production and drinking water supplies, the schemes have other benefits, such as the mitigation of flood damage. The complexity of flood water spreading schemes using flash floods of ephemeral rivers in semi-arid regions became evident during the task of selecting, defining and structuring criteria for the selection of suitable areas and sites for a scheme. Complexity is due to a large number of factors that play a role in the selection of the most suitable sites for deciding on investment in a scheme These factors pertain to earth science (geology, geomorphology, soils), to hydrology (runoff and sediment yield, infiltration and groundwater conditions) and to socio-economic aspects (irrigated agriculture, flood damage mitigation, environment and so on). This paper deals with developing a DSS to assist decisions as to where suitable catchments and associated infiltration areas are located. The DSS developed relies on the combined use of remotely sensed information and GIS techniques. For implementation of the related phase of the DSS, a region (Bandar Abbas) was selected as the case study for suitable zone(s) selection. The DSS shows the great ability for selection of potential zones for floodwater spreading. It can be concluded that the interpretation results could be regarded as being more than the sum of separate 'interpretation' layers: i.e. geology, geomorphology and land use. The interpreter has to have a firm footing in earth science.

Three new indices namely: abiotic-stress tolerance index (ATI) (Abiotic-stress Tolerance Index), stress susceptibility percentage index (SSPI) (Stress Susceptibility Percentage Index) and stress non-stress production index (SNPI) were introduced to identify relatively tolerant (through ATI and SSPI) and resistant (through SNPI) genotypes under nonirrigated and irrigated conditions. Sixteen bread wheat genotypes (in 2004, under a moderate stress with SI = 0.31) and twenty durum wheat genotypes (2004 and 2005 under a severe stress with SI = 0.57) were studied in field experiments under non-irrigated and irrigated conditions. Yield changes in non-irrigated and irrigated conditions for different genotypes, the primary selection of genotypes for relative drought tolerance or resistance and a comparison between new indices and previous ones were studied. In this paper, «relative tolerance and resistance" phrases are used instead of ''tolerance and resistance" because we believe that, generally, there are no complete tolerance and resistance to abioticstress. ATI and SSPI exhibited a positive significant simple correlation with TaL, Yp and SSI, but their correlations with RDI were significantly negative. ATI and SSPI differentiated between relative tolerant and intolerant genotypes better than TaI and SSI in some cases and were considered as a favorite index for the selection of relatively tolerant genotypes. AT! and SSPI are powerful to select extreme tolerant genotypes with yield stability and may be can use of them as parents in conformation to a QTL population for yield stability in two irrigated and non-irrigated conditions, because, both of them are related to relatively yield stability and may be state that a genotype with suitable yield stability carries drought tolerance or other related trait genes. SNPI had a positive correlation with yield changes in both non-irrigated and irrigated conditions and negative correlation with SSI and TOL, therefore, to select a genotype with appropriate, high and stable yield in both stress and non-stress conditions for commercial aims, it is suggested to use SNPI as a desirable index because this index supports stable and high yield in both conditions (especially in non-irrigated condition) simultaneously.

Seed germination is an important phase of plant development during which soil water availability is crucial. Salinity can affect seed germination in two ways: 1) Change of osmotic potential of available water, 2) toxicity effects. In this experiment, interactive effects of salinity and water deficit on germination criteria of two species of A, littoralis and A. logopoides were studied in a factorial design with completely randomized arrangement and four replications. Treatments were combinations of four levels of water deficit (-0.3, -5, -10 and -15 bar), four electrical conductivity levels (0, 20, 25 and 30 dSm-1) and two species of Aeluropus. Water deficit and salinity were induced through PEG-6000 and sodium chloride respectively. After three weeks rate, as well as percentage of germination were determined. Results showed that by increasing salinity and water deficit both criteria of percent germination and germination rate were reduced and there was an interactive effect of these stresses on germination. In general effects of salinity were more pronounced than water shortage. These results were somehow similar for either one of the species.

This research investigates the effect of drought on ground water table of Neishabour plain. The precipitation data of Nishabour synoptic station during 1990-2001, the Bar climatology station during 1964-2001 and the data of hydro metricmstations of Kherv and Bar in 1996-2001 have been used as the base of analysis. The method of Herbest et all has been used to analyze the drought. Using the effective precipitation and effective flow, the date of start and end of drought for the study region has been specified and then the time and intensity of drought have been calculated. The analysis shows that the main reason for the fall of the underground waters table level is the irregular use for agricultural consumptions. The climatic drought has had a direct effect on running water and it has also had direct effect on underground water of the region with a time lag. It was appeared that alluvial fan areas of Neishabour plain have a less decrease compared with the central and southern areas in spite of much consumption of water by deep wells.