1 1680-7073 Tarbiat Modares University 8985 Using a General Dynamic Econometric Framework to Specify the Appropriate Model in Studying Agricultural Production Structure: A Case Study of Crop Production in Iran Salami H. b Veeman T. S. c b Department of Agricultural Economics, Faculty of Agriculture. University of Tehran, Islamic Republic of Iran. c Department of Rural Economics, University of Alberta, Edmonton, Canada. 1 10 2000 2 4 231 241 15 05 2010 15 05 2010 This paper shows the role of the general dynamic model in empirical research of production technology in agriculture. The model is a first order autoregressive multivariate specification, first developed by Anderson and Blundell. This model is general enough to nest several simpler dynamic as well as static models within it. Therefore, it provides a framework for applying classical testing procedures and identifying the appropriate specification in the empirical econometric model of production. The usefulness of the general dynamic model is shown by estimating the production structure in the Iranian crop sector. The results indicate that the Iranian crop production is best characterized by a long-run static model derived from a non-homothetic translog specification which incorporates non-neutral technological change and allows for structural change after the Islamic Revolution of 1979.
11166 Genesis and Morphological Changes of Soils under Irrigated Date Palm in Southern Iran Baghernejad M. d d Department of Soil Science, Shiraz University, Shiraz, Islamic Republic of Iran. 1 10 2000 2 4 243 256 15 05 2010 15 05 2010 Macro and micromorphological investigations were conducted on selected Xerepts soils from southern Iran to identify changes in soil characteristics with time. Soil samples from similar pedons of four irrigated orchards ranging in age from 20 to 100 years were studied and compared with soil samples of a pedon of non-irrigated land. In addition to routine analyses, undisturbed blocks of soils from each horizon of pedons were prepared and used for micromorphological studies. Field data, micromorphological obsrevations and laboratory data, permitted an overview of changes in soil characteristics and their role in the pedogenesis. Changes observed include the type and distribution pattern of voids, translocation and accumulatin of CaCO3, and the soil fabrics. Calcitic hypocoatings, and compound dense complete calcite infillings in vughs, and large voids were attributed to precipitation as induced by irrigation. There seems to be an increase in organic matter content with time. This needs to be further studid to establish condition for carbon sequestration and increased soil quality in arid regions. 11099 Effects of Scarification and Temperature on Germination of Licorice (Glycyrrhiza glabra L.) Seeds Ghadiri H. e Bagherani Torshiz N. f e Department of Crop Production and Plant Breeding, College of Agriculture, Shiraz University, Shiraz, Islamic Republic of Iran. f Agricultural Research Center, Gorgan, Islamic Republic of Iran. 1 10 2000 2 4 257 262 15 05 2010 15 05 2010 Laboratory experiments were performed to determine the effect of various scarification treatments at four temperature regimes on germination of licorice seeds . A randomized complete block design with four replications was used. Germination counts were made every day for 2 weeks. At 50C, none of the chemically and mechanically scarified and non scarified seeds germinated. At 15, 25, and 350C, mechanical scarification increased seed germination to 94-98%. However, at these temperatures, velocity of germination of mechanically scarified seeds were lowest among all treatments. Chemical scarification also increased germination percentage significantly to 90-95% with 45 min soaking. At 15 and 250C, seed germination percentage and velocity of germination increased as the soaking time in sulfuric acid increased from 5 to 30, 45, or 60 min. However, at 350C, there was no difference in germination percentage between soaking times of 5 and 60 min. It appears that soaking for 45 min provides full germination at 25 and 350C. 12199 Yield and Yield Components of Two Winter Wheat (Triticum aestivum L.) Cultivars in Response to Rate and Time of Foliar Urea Application Emam Y. g Borjian A. R. h g Department of Agronomy, College of Agriculture, Shiraz University, Islamic Republic of Iran. h Agricultural Research Center, Khanssar, Islamic Republic of Iran. 1 10 2000 2 4 263 270 15 05 2010 15 05 2010 Foliar urea application is one of the nitrogen (N) application methods in cereal grain crops. Yield and yield components may be affected by foliar urea application. To investigate the effect of rate and time of such treatment on yield and yield components of two winter wheat cultivars, a field experiment was conducted at Badjgah, Agricultural Research Farm (29° 36 N, 52° 32 E) of Shiraz University, Shiraz, Iran during 1998-99 growing season. The experimental treatments were two winter wheat cultivars (‘Phalat’ and ‘Marvdasht’), five levels of foliar urea application (0, 8, 16, 24 and 32 kg N ha-1) at three times of application (pre-anthesis, anthesis and post-anthesis). The experimental design was a randomized complete block one with treatments arranged as split-plot factorial with three replicates. The results showed that cultivars responded differently to the rate of foliar N feeding so that, over the growth stages, Marvdasht cultivar produced significantly greater grain yield (+19%) by application of 8 kg N ha-1, whereas, the Phalat cultivar had greater grain yield (+27%) when it was supplied by 16 kg N ha-1. Increase in grain yield was mainly due to an increase in number of grains ear-1. The fertile ears m-2 and mean grain weight were not significantly affected by foliar urea feeding, however, the harvest index and biological yield were increased. The pre-anthesis foliar feeding with urea resulted in higher yields as compared with later applications. Also the early foliar urea feeding increased the harvest index from 42.4% to 46.9% at 32 kg N ha-1 in Marvdasht cultivar. The results of the present investigation also suggest that late foliar application could decrease nitrogen use efficiency. 1537 Effects of Stocking Density and Grazing Period on Herbage and Seed Production of Paraggio Medic Chaichi M. R. i Tow G. j i Agronomy Department, College of Agriculture, University of Tehran, Karaj, Islamic Republic of Iran. j Department of Agronomy and Farming Systems, College of Agriculture, University of Adelaide, Adelaide, Australia. 1 10 2000 2 4 271 279 15 05 2010 15 05 2010 Three stocking densities (20, 40, and 60 sheep/ha) were applied in four stocking periods (0, 2, 4, and 6 weeks) on a Medicago truncatula cv. Paraggio pasture. Treatments were arranged in a split plot system and compared through a completely randomised block design with four replications.Grazing period had a significant effect (P<0.001) on availability of both medic and other species separately. Total available forage (medic and other species) was significantly affected by both stocking density (P<0.05) and grazing period (P<0.001) and there was a significant interaction between stocking density and grazing period (P<0.001). Grazing period was the only factor affecting the cumulative forage production of medic and other species. Stocking density and grazing period both had significant effects on total cumulative pasture production. Pod production significantly decreased as grazing period increased. More seeds per pod were observed at low stocking density as compared with other densities. There was a dramatic reduction in seed production as grazing period increased (P<0.05). 1409 Distribution of 32P between Roots and Tops of White Clover: Effect of Mycorrhizal Fungi and Placement Distance from the Roots Mehravaran H. k Mozafar A. l Frossard E. m k College of Agriculture, Urmia University, Urmia, 57135, Islamic Republic of Iran. l Institute of Plant Science, Swiss Federal Institute of Technology (ETH), Eschikon Experiment Station, CH-8315 Lindau, Switzerland. m Institute of Plant Science, Swiss Federal Institute of Technology (ETH), Eschikon Experiment Station, CH-8315 Lindau, Switzerland. 1 10 2000 2 4 281 290 15 05 2010 15 05 2010 In a greenhouse experiment, the effects of Glomus intraradices and indigenous mycorrhizal isolates from soils under plow and no-till treatments on the uptake of 32P placed at 1, 2.5 and 4 cm from the roots of white clover (Trifolium repens) in 23, 37 or 46 days after planting were compared.Spores of the indigenous fungi were mostly a mixture of Glomus mossea, G. clarum, G. caledonium and G. claroideum . The colonization of the roots with regard to hyphae, vesicle or arbuscules was significantly different among fungi. Uptake of 32P from different distances from the roots was strongly dependent on the mycorrhizal isolate used and the plant-symbiont age. Indigenous fungi were more effective in translocating 32P from short distances compared with G. intraradices as measured in the plants. At the age of 46 days, for example, fungi from no-till and plowed plots transported 8-10 times more 32P to the plants as compared with G. intraradices, when32P was placed at 1-cm distance from the roots. These differences, however, disappeared when 32P was placed at 2.5 or 4 cm from the roots. As the plant-symbiont grew older, relatively more 32P was translocated to the tops and the differences between fungi in this respect became more pronounced. In 21-, 37- and 46-day-old plants, for example, and when 32P was placed 1 cm from the root surface, 18, 21 and 56%, respectively, of the absorbed 32P was translocated to the tops in plants inoculated with fungi from plowed fields. Progressively lesser amounts of total absorbed 32P were translocated to the tops as 32P was placed farther away from the roots. For example in 46 days after planting 51, 30 and 11% of total absorbed 32P was translocated to the tops when 32P was placed at 1, 2.5 and 4 cm from the roots, respectively, white clovers being inoculated with fungi from no-till soil. It is concluded that the native mycorrhizal fungi , after a long period of different tillage practices, may have different effects on the partitioning of absorbed phosphorus within white clover. 1552 Relationship between Nuclear Polyhedrosis Virus Susceptibility and Larval Weight in Heliothis armigera Pourmirza A. A. n n Department of Plant Protection, Urmia Universiy, Urmia, Islamic Republic of Iran. 1 10 2000 2 4 291 298 15 05 2010 15 05 2010 The population response of Heliothis armigera larvae to nuclear polyhedrosis virus (NPV) was investigated. The virus was introduced by permitting the larvae to feed on lettuce leaves. Median lethal doses (LD50) were determined. The estimated LD50 values for the first, second, third, early, and late fourth larval instars were 5, 141, 1226, 5168 and 24553 polyhedra per larva respectively. In the fifth larval instar a degree of maturation resistance against virus infection was observed. An inverse relationship between mortality and larval weight was detected. Expressing the results in terms of LD50 / mg of the larval weight eliminated the observed variation in the susceptibility of larvae. The estimated LD50 values for each of the larval instar groups were used to predict the response of the larval population to virus infection. This procedure provided a sound determination of the response pattern, from which 96% of the variation in the larval susceptibility could be described in terms of the log larval weight. 3459 Modeling of Orange Mass Based on Dimensions Tabatabaeefar A. o Vefagh-Nematolahee A. p Rajabipour A. o Department of Agricultural Machinery Engineering, College of Agriculture, University of Tehran, Islamic Republic of Iran. p Department of Agricultural Machinery Engineering, College of Agriculture, University of Tehran, Islamic Republic of Iran. Department of Agricultural Machinery Engineering, College of Agriculture, University of Tehran, Islamic Republic of Iran. 1 10 2000 2 4 299 305 15 05 2010 15 05 2010 There are instances in which it is desirable to determine relationships among fruit physical attributes. For example, fruits are often graded on the basis of size and projected area, but it may be more suitable and/or economical to develop a machine which grades by mass. Therefore, a relationship between mass and dimensions or projected areas and/ or volume of fruits is needed. Various grading systems, size fruits on the basis of specific parameters. Sizing parameter depends on fruit and machine characteristics.Models for predicting mass of orange from its dimensions and projected areas were identified. Models were divided into three classifications: 1- Single and multiple variable regression of orange dimensions (1st classification). 2- Single and multiple variable regression of projected areas (2nd classification). 3- Estimation of orange shape; ellipsoid or spheroid based on volume (3rd classification). Ten Iranian varieties of oranges were selected for the study. 3rd classification models had the highest performance followed by 2nd and 1st classifications respectively, with R2close to unity. The 2nd classification models need electronic systems with cameras for projection whereas, 1st classification models are used in the simple mechanical systems, except multiple variable ones, of and 3rd classification models need more complex mechanical systems. Among the systems that sorted oranges based on one dimension (Model 2), system that applies intermediate diameter suited better with nonlinear relationship as: M = 0.07b2 – 2.95 b + 39.15 with R2= 0.97.