Journal of Agricultural Science and Technology
Volume:8 Issue: 3, Jul 2006

In order to help in the engineering design of rice harvesting machines, there is a need to have exact information concerning the physical and mechanical properties of rice stems. The cutting force for rice stems, therefore, was measured by designing and fabricating a static and dynamic shear test apparatus. The effects of moisture levels and the crosssectional area of stem as well as the variety, blade bevel angle, blade type and cutting speed on shearing strength have been evaluated. The results indicated that the cutting force increased with an increase in the cross-sectional area and decreased with an increase in moisture content. The static and dynamic shearing strength was different among the varieties. The maximum and minimum shearing strengths were related to the varieties Khazar and Hashemi, with an average of 1629 and 1429 kPa for static test and values of 187.4 and 144 kPa for the dynamic test, respectively. The shearing strength decreased from 234.4 kPa to 137.4 Kpa with an increase in blade cutting speed from 0.6 to 1.5 m/s. Blade bevel angle and blade type had no significant effect on the shearing strength of rice stem.

This study investigated intra-specific variation in the growth parameters and dry matter partitioning of sugar beet cultivars at different levels of salinity (0, 50, 150, 250 and 350 mM NaCI + CaCl2 in 5:1 molar ratio) using foul'' cvs, one British (Madison) and three Iranian cvs (7233-P12'' 7233-P21 and 7233-P29)'' The plants were grown in a controlled greenhouse environment for about 18 weeks. Although growth parameters such as leaf area and dry matter accumulation were stimulated or unaffected at a low level of salinity (50 mM), higher salt concentrations significantly decreased all growth traits. At a high level of salinity, cv P29 showed a significantly higher leaf area and total dry matter than others at 16 weeks of salt treatment, Pre-dawn leaf-water potential (lJld and shoot water content (SWC) were decreased by salinity. Cvs Madison and P12 had significantly lower lJlL(more negative) and shoot watel'' content at high levels of salt treatment (250 and 350 mM), while P29 and P21 showed highel'' lJlL (less negative) and shoot water content at the same salt concentrations. Analysis of ion accumulation revealed that Na+ and cr contents were greatly increased in leaves under saline conditions. However, salt tolerant P29 had lower Na+ and cr concentrations than other cvs at high levels of salinity. The root dry matter of sugar beet cvs at the lowest and the highest salt concentrations reduced by 23.3% and 89.8%, respectively compared to the non-stressed plants, while shoot dry mattei'' decreased by 1.1% and 77% at the same salt concentrations, respectively, after 16 weeks of salt treatment. The pattern of dry matter partitioning to different parts of the plant was changed by salt stress and the dry matter allocated to the storage roots was reduced by 6% and 18% at the lowest and the highest salt concentrations, respectively, at 16 weeks aftel'' salinisation,

The effects of water deficit on grain yield, yield components and the physiological characteristics of barley (Hordeu1Il vulgare L.) varieties were studied in a split plot design during the 1999-2000 growing season in Karaj, Iran. Five irrigation levels [0, 25, 50, 75, and 100% crop water requirements (CWR)] and six barley varieties KaroonxKavir, Reihani(drought tolerant), Torkman, C-74-9 (intermediate), KavirxBadia and Gorgan-4 (2 rowed type, drought sensitive) were arranged in the main plots and sub plots respectively. Results showed that water deficit induced stress and this decreased the grain yield and yield components. Water deficit increased the canopy temperature and those varieties showed a higher canopy temperature undel. non-stress conditions, performed bettel. under drought conditions. Severe stress reduced the chlorophyll content (SPAD values) considerably, but the differences were not significant between the 50, 75 and 100% CWR treatments. In addition, no significant differences were observed in the chlorophyll content of barley varieties under drought conditions. The effect of irrigation on the photochemical efficiency of photosystemll (Fv/Fm)and the other fluorescence parameters for all varieties were significant. Although the FvfFm values were not significant in barley varieties at any level of irrigation, in general Karoon x Kavir and Reihani varieties showed a better performance under water deficit conditions. Proline content was significantly different in various irrigation treatments, but its accumulation at any level of irrigation did not differ significantly in barley varieties. It was concluded that the higher canopy temperature (less negative ~T) under well irrigated conditions and higher grain yield, 1000- grain weight, FvfFmvalues under water stress conditions could possibly be the proper criteria for screening the drought tolerant barley genotypes under field or laboratory conditions.

The mean fiber length of three beech trees (Fagus orientalis L.) at the lower and higher points (1% and 75% tree height) of the stem at an intermediate altitude (500-1000m) in the Caspian forests in Sari region were 1.36 and 1.22mm respectively, close to the values in three trees at high altitude (1000-1500m), that were found to be 1.39 and 1.36 mm. The mean fiber lengths of the whole stem, using stem formula, were considered as 1.31 and 1.38mm at intermediate and high altitudes and so were very close each other. Juvenile wood portions in the stem comprised 17 annual rings, which took up 7.3% of the stem by volume at intermediate altitude. At high altitude, these values were obtained as 18 annual growth rings, and 8.75% juvenile wood in the stem. The reason for gl''eater juvenile wood at high altitude was somehow a wider ring width at higher elevation. The mean ring width of lower and upper points of the stem at intermediate altitude were found to be 1.82 and 2.95mm respectively; meanwhile, at high altitude, the findings were 2.97, 3.37mm. Despite the data obtained, t- test comparison was conducted between mean fibel'' lengths of the two heights of the stems at two altitudes, and no significant differences were found at the 1% level. The exploitation age was strongly dependent on how much juvenile wood there was in the stems, that at high altitude was greater than at intermediate. However, statistical comparison showed no significant differences between that and the 1% level. Therefore, altitude in the range of about 500m showed no impol.tant impact on beech fiber length, exploitation age or juvenile wood border in Caspian forests.

e partial differential equations for water flow and solute transport in a two-dimensional saturated domain are rendered discrete using the finite difference technique; the resulting system of algebraic equations is solved using a dynamic programming (DP) method. The advantage of the DP algorithm is that the problem is converted from solving an algebraic system of order NC(NL-1) NC(NL-1) into one of solving a difference equa-tion of order NCNC over NL-1 steps and involving NL-1 matrix inversions of order NCNC. The accuracy and precision of the solutions are shown by comparing the results with an analytical solution and calculation of mass the balance. In addition, the perform-ance of the DP model was compared with the results of the MOC model developed by US Geological Survey. In all cases, the DP model showed good results with sufficient accu-racy

Trichoder11la harzia1ll111l(T39), T.virellS (DAR74290), T.viride (MO), T. harzia1ll111l(M) and TrichderminB a commercial formulation of T. harzianum(Bi) were evaluated as potential biological agents for the control of charcoal stem rot in melon caused by Macrop/1011Iillaphaseolilla. Cell-free metabolites of T. harziall1111l(M),T. harzia1ll111l(T39) and T. virells (DAR 74290) inhibited growth of M. phaseolilla completely ill vitro and appeared to be fungicidal. T. viride (MO) inhibited fungal growth from 34.9% to 71%. T. harzia1ll111l(T39), T. harzia1ll111l(M), T. virellS (DAR 74290), T. viride(MO) and T. harziall1111l(Hi) were tested for their ability to protect melon plants from disease caused by M. phaseolilla in a glasshouse experiment. The percentage of stand plants with the antagonist alone or in combination with the pathogen was significantly (p<0.05) greater than in plants inoculated with the pathogen alone. The percentages for the stand plants in treatments were as follows: T. harzia1ll111l(T39), T. harzia1ll111l(M), T. virells (DAR 74290), M. phaseolilla, M. phaseolilla + T. virellS (DAR 74290), M. phaseolilla + T. harziall1111l (f39) and M. phaseolilla + T. harziall1111l(M),at 95, 100, 97.5, 15, 64.25, 75.25 and 47.55 percent respectively. The percentage for the stand plant in the commercial Trichodermin B + M. phaseolilla treatment (96.7%) was greater than for M. phaseolilla alone (46.7%) and demonstrated the best result in the control of charcoal stem rot in melon.

Phosphorus (P) sorption in soils is a key process governing its availability to crops. There has been scanty information available on the P sorption characteristics of calcare-ous soils of Western Azarbaijan Province, Iran. In this study, P sorption characteristics and their relationship to soil properties were determined in 36 soil samples belonging to 15 agricultural soil series located in the south of Urmia, Western Azarbaijan Province. Total CaCO3 contents ranged from 10 to 48.5%. Active CaCO3 contents ranged from 1.7 to 20% and were significantly related (r = 0.61, P<0.001) to the total CaCO3 of the soils. NaHCO3-extractable P contents ranged from 4 to 38 mg P/kg soil. The amount of P sorbed by the soils differed among various soil series. The results showed that equilibrium solution P concentration (EPC) was lower (<0.2 mg/L) than the requirement for most crops. The amount of P adsorbed by the soils at 0.2 mg/L EPC ranged from 5 to 114 mg/kg soil. The phosphate adsorption was well described by the Freundlich (r2 = 0.96) and Langmuir (r2 = 0.88) isotherms. The Langmuir maximum adsorption (Xm) and Freundlich coefficient (aF) estimated from Langmuir and Freundlich equations ranged from 127 to 238 mg P /kg soil and from 43 to 211 mg P/kg, respectively. Soil clay content was significantly related to the soil P sorption indices, P0.4 (P sorbed at 0.4 mg P/L, r = 0.40, P<0.01), PBC (P buffering capacity, r = 0.54, P<0.001), aF (r = 0.48, P<0.01), and Xm (r = 0.40, P<0.01). Total CaCO3 and active CaCO3 were found to be less important factors affecting P adsorption.

The 1RS chromosome segment derived from Petkus rye carries genes for resistance to three wheat rust diseases, namely Lr26 for resistance to leaf rust (caused by Puccinia triticina), Yr9 for resistance to stripe rust (P.striiformis f. sp. tritici) and Sr31 for resistance to stem rust (P. graminis f. sp. tritici). Since Sec-1 is tightly linked with the three rust resis-tance genes electrophoresis it is a useful method to identify and confirm the presence of three rust resistance genes in current wheat populations. SDS-PAGE was used to examine eight Iranian wheat cultivars for resistance to three rusts. The eight Iranian wheat culti-vars examined were Alvand, Darab 2, Tajan, Nicknejad, Mahdavi, Zarrin, Alamoot and Atrak. The SDS-PAGE results showed that cultivars Mahdavi and Atrak have Sec-1 bands and are therefore likely to carry the 1BL.1RS translocation and the linked genes Yr9, Lr26 and Sr31.