Year:2001 | Volume:6 | Issue:4|Papers Count:9

Soil compaction due to traffic of agricultural machinery and tillage implements that affect soil physical properties and agricultural yeilds is accentuated with increasing mechanization of agriculture using higher power tractors. Compaction of soil under tractor tires has been studied by many researchers, but reports on soil compaction due to tillage implements are few.In this investigation, soil compaction caused by plow bottoms is studied. The effect of parameters such as forward speed, soil moisture contect and texture, and type of tillage implement on soil compaction at bottom of the furrow and the layer 4 cm below it was invesigated.A Complete randomized block design was used and soil bulk density was measured as index of compaction.Results of statistical analysis indicated that bulk density increased significantly with soil moisture content. Both soil and implement types significantly affected soil compaction of the). furrow bottom (and at constant moisture content Mean compaction at the highest moisture level lowest speed for the moldboard plow was 14.18%.Increasing forward speed resulted in decreasing compaction. Soil moisture being constant, compaction for the soil with lighter texture at equal velocity was lower for disk plow than moldboard plow. This compaction at 18.25%moisture content in the silty-Ioam soil was 5.3% . In all treatments no significant compaction was observed in the soil layer below the furrow bottom.Although weight of moldboard plow was lower than that of the disk plow, because of the nature of soil loading by moldboard plow bottoms, they caused more compaction than the disk plow bottoms.

In the first and second national development programs signification attention has been focused on the efficiency of water use. The use of pressurized irrigation system received priority in the agricultural strategy set by the government. However, the development of these systems has faced many problems and uncertainties. Recognizing these problems and unknows will be a helpful guide for agricultural policy makers and will assist them in their practical approach to the problem. Linear programming was used in order to analyze these systems to assess their optimum water allocation and efficeincy. The results of this study showed that in case these systems are disigned and operated properly they can optimize water use by increasing effiency, reducing evaporation, and providing a more suitable cropping pattern.  

In this study, the effect of different temperatures (5, 10, 15, 20, 25, 30, 35°C), and various levels of NaCl (0, 42, 85, 128, 170, 213, 256, 341, 427, 512, .598, mMol) on the germination of seeds of two Atriplex species - A.nitens [Robent] Schkuhr and A.tatarica (L) Aellen - the speed of germination and salinity tolerance of the seeds were investigated.The results clearly show that distilled water - at 20°C - is the optimal medium for seed germination of both species, and that higher temperatures will cause significant decrease in the percentage of germination. At a given temperature - ranging from 0°C to 35°C - the percentage of germination at 20°C in distilled water is higher than that recorded for other media containing various levels of NaCl. At all temperatures, increasing salinity reduces seed germination percentage of both species. Nevertheless, NaCl level of 42 mMol ensures a maximal germination speed at 10°C and 20°C for A.nitens (Robent) Schkuhr and A.tatarica (L.) Aellen, respectively.The increase in salinity will significantly decrease the speed of seed germination. It seems that the seeds of A.nitens are far more sensitive to temperature and salinity variations than those of A.tatarica. Also the increase in temperature decreases salinity tolerance of the seeds of both species. At higher levels of NaCl, the increase in temperature results in abnormal seedling formation in addition to decreasing the germination percentage and speed.

A faunstic survey was carrid out to collect and identify aphids attaking various plants in Torbate Heydarieh (East Iran) was studied during 1992-1994.Seventy two species from 38 genera belonging to 6 families of Aphidoidea were collected and identified. Two genera Staegeriella H.R.L. and Neotrama Baker and four species S.necopinata (Borner), N.caudata (Del Guercio), Pemphigus fuscicornis (Koch) and Anuraphis catonii H.R.L. wet-e recorded from the first time from IRAN.

Millet is an amual crop from gramineae family using as a forage. The agroecological factors affect the quantitative and qualitative of the forage production. The most important factors are available water during the growing season and planting date.In order to investigate the effects of irrigation regimes and planting date on water use efficiency and yield of pearl millet (pennisetum americanum L. (Leek), a split plot on basis of complete block desing with four replications, at the center of agricultural station in yazd, is employed.This experiment, was consisted of, three levels of irrigation according to the coefficients 0.4, 0.6 and 0.8 of evaporation as main plots and planting dates of four levels, April 4, April 19, May 5 and May 20 as sub plots. The results showed that all characters affected by irrigation treatment and planting dates. Treatment of irrigation with evaporation 0.8 and with 6.61 Kglm2 yield over levels of irrigation regimes and treatment of irrigation with evaporation 0.4 with 5.79 Kg/m2 yield were the highest and lowest, respectively. Irrigation regimes affected water use efficiency. By reducing the irrigation water, the yield, plant height and number of tillers decreased but, wue increased. At there was over water use efficiency (1.69 Kg/m3 yield. The level of irrigation with evaporation 0.4 There was a significant difference among the measured characters for the date of planting. The delay of planting date, showed the reduces of yield and other characteristics.The results showed that irrigation with 0.4 evaporation and April 4 planting date are better.

Sugar beet is one of the agricultural products in world and it supplies the large amount of sugar consumed in our country. So one of the major policies of the agriculture is to development the production of this product. As a result different expriments and studies were done to identify the best date of planting and advising the most conveient number as one of the methods of better planting and increasing the rate of production.This study was done in Research Farm" Islamic Azad University of Khoy 1377. The experiment was a Completely-rondomized Split-Plot Design, the main levels were three dates of planting March 31, April 10 and April 20, 1998. The Sub-levels varieties PP22, 41RT, PP36 and monogerme 9597. The findings indicated that the time of planting affects the root and the rate of sugar. So the highest function of root was a bout 53 ton in 11th of farvardin and the rate of sakaroze was about 15/7 percent.Regarding the sugar, the function of root and the supplied sugar there was a major difference. variety 41RT was the highest and monogerme 9597 showed the lowest function of root as 56 and 43 ton/ha. Studing Leaf Area Index found out that Sugar beet in comperision with other plants Keeps more Leaf Area at the end of planting season.The highest amount Leaf Area Index (LAI=3/9) was 41RT in 11th of farvardin. By studying the results and by analyzing the finding of this year, planting variety 41RT in the first half farvardin and consequently in ereasing the yield of sugar and its production was recommended to the farmers of Khoy.

Atmosphere as a gasseous component, has covered earth surroundings and is one of the most important component of life forming processes and its system flow in the biosphere. This component would affect life through its constituents which are known as an atmospheric components, the effects of which are changing according to the time and space. Also, would affect human and its bio activities through climatological characteristics resulting from time and spacec changes. Men has always been influnced by different climates and have acted in harmony with the prevailed conditions imposed upon him.The medical geographya is one of the important branches of applied science and could be regarded within the framework of these situations. Therefore any changes in atmospheric situation and phenomenos, and also in consequent climatic combinations would finally affect human life as well as his metabolic reactions.In this article, it has been tried to describe the environmental peculiarities components constituting the atmosphere and also the bio-role of different climates resulting from time changes. The effects of these changes and subjects on human communuties are discussed and reveald here.