Iran Agricultural Research
Volume:26 Issue: 1, Winter and Spring 2007

The objective of this work was to study the effects of tillage and liquid manure applications on some physical and chemical properties as well as on the carbon and nitrogen mineralization potential of a meadow soil. Our results indicated that tillage and manure applications had no effect on the concentration of Cu, Mn, total N and organic C in 0-15 cm layer of soil after 15 years of treatment. However soil P, Ca, Mg and Zn contents significantly increased with manure applications. Soil organic matter and total N significantly decreased in a 15-30 cm depth. No significant change was detected in soil structural stability in any of the layers. Moreover, tillage affected soil soluble C and the C/N ratio significantly. Application of 100 t ha-1 manure significantly increased soil soluble C. The results of this study suggest that tillage increased the soil N mineralization rate significantly. The potentially mineralizable nitrogen (N0) was higher in tilled than in no-tilled soil and was at its maximum in the 0-15 cm layer. Furthermore, a significant positive interaction was observed between tillage and manure application on mineralized N after 1.4 wk (Ne). No significant change was detected in C mineralization rate (Cm) and potentially mineralizable C (C0). The total amounts of mineralizable carbon (Cm) and nitrogen (Nm) significantly decreased in 15-30 cm depth and were very closely correlated with the total amounts of C or N and mineralization rate constants (K).

This paper explores the effects of general and agricultural trade openness on economic freedom and alongside with the quality of institutions, on income and poverty. Recent cross-country data for over 200 nations in global regions were used to estimate equations for income, poverty and economic freedom. Economic freedom appears to have positive impacts on income levels, which together with good institutions reduce poverty. It is also concluded that poverty is determined both directly and indirectly by institutions. A typical finding of this paper is that, in general, economic freedom is associated with trade openness and with agriculture trade liberalization.

Side weirs are flow diversion devices that are widely used in irrigation, drainage and urban sewage systems. The present study focuses on the investigation of the effect of oblique side weirs on the discharge coefficient of a side weir under subcritical flow condition in rectangular channels. In this study 106 laboratory tests were conducted and the results were analyzed to find out the influence of non-dimensional parameters on the discharge coefficient of the weirs. The angles of side weirs varied from 0 to 17.5 degrees in six steps, three heights (5, 10 and 15 centimeters) and three lengths (100, 80 and 40 centimeters). Two descriptions of the discharge coefficient (traditional side weir coefficients, Cd, and De-Marchi, CM), along with different discharges and related parameters were used. According to the results, Cd is more sensitive to b1/b2 (ratio of channel bottom widths), whereby CM is sensitive to L/b1 (ratio of side weir length to bottom width). The correction formula for estimating the oblique side weir discharge coefficient with a traditional shape shows that a 17.5 degree angle with side wall causes 40 percent change in the discharge coefficient.

To use soil hydrology processe (SHP) models, which have increasingly extended during the last years, comprehensive knowledge about these models and their modeling approaches seems to be necessary. The modeling approaches can be categorized as either classical or non-classical. Classical approaches mainly model the SHP through solving the general unsaturated flow (Richards) equation, numerically or analytically. Due to a number of shortcomings of classical approaches, a trend toward the application of non-classical models has been initiated in recent years. Artificial neural networks and fuzzy logic systems are two main kinds of non-classical approaches. In this study, existing modeling approaches of SHP with an emphasis on recent trends were reviewed and compared. Also, modeling approaches of soil hydraulic functions are reviewed briefly as a main part of SHP models. Finally, classifications for SHP models from different viewpoints are presented.

The majority of hydraulic processes under a natural condition in a field are carried out under unsaturated flow conditions. The soil moisture retention curve (SMRC) is the most important hydraulic characteristic of an unsaturated soil whose knowledge is of prime importance in soil-water studies such as soil conservation, soil erosion, land evaluation, soil reclamation, and water resources management. SMRC can be determined by two different direct and indirect methods. While there are noticeable developments on direct methods, they are still time- and labor-consuming. As a result, researchers are focusing more on indirect methods. The present research has evaluated some common PTFs for predicting the SMRC for a number of soils in Iran. Fifty soils, the majority of which were loam and clay loam, were taken from Karaj, Amol, and Babol in the north of Iran. Soil water contents corresponding to matric potentials of 0, -5, -33, -100, -500, and -1500 kPa were determined by a pressure plate apparatus. Four common PTFs of Rawls and Brakensiek (RB), Vereeken et al. (VMFD), Wosten (W), and Wosten et al. (WLNL) were used in this study. To evaluate these PTFs, the GMER (Geometric mean error ratio), GSDER (Geometric standard deviation of error ratio), and RMSE (Root mean square error) indices were considered. The results showed that these PTFs functioned better for loam-textured soils. VMFD and WLNL PTFs performed better, while VMFD was better than the others for clay loam soils. In general, better fit was found as the matric potential increased.

Pedogenesis and clay mineralogy of soils and rock samples were studied in a transect of calcareous, gypsiferous, saline soils and sediments of Bakhtegan lake bank in southern Iran. The main objectives of study were to determine the occurrence of clay minerals and factors controlling their distribution pattern and relative abundance in soils and parent materials. The soil parent material is highly calcareous in all regions. However, gypsiferous and saline soils mainly occur near the Bakhtegan Lake with much evaporitic sediments (gypsum and halite) and where there is a saline and alkaline ground water table. XRD, TEM, SEM and EDX analyses indicated that chlorite, illite, palygorskite, smectite and interstratified minerals are the dominant clay minerals in both soil and rock samples. The presence of illite, chlorite abundance could be attributed to the parent rock samples and inherited origin. Interstratified minerals of chlorite-smectite or illite-smectite are observed in clay fraction of soils situated in plains and down slope due to further weathering and transportation from upslope to down slope. Studies indicated the presence of neoformed, transformed and inherited forms of palygorskite in all soils. Studies have showed that arid soils in southern Iran were affected by post-Tethyan sediments and some minerals have evolved from the weathering of these sediments.

There are many reports on the application of different hydrocolloids in the production of leavened breads; most of which show positive effects on bread quality. However, there is little information to prove such effect on flat breads. The main aim of this study was to improve the quality of Barbari dough and bread (Iranian flat bread) in terms of texture, taste and general acceptability of fresh bread. This was achieved by using two types of hydrocolloids; microcrystalline cellulose and hydroxypropylmethyl cellulose at 0.5% wheat flour basis. The results indicated that addition of either of the two cited hydrocolloids could improve dough and bread quality. However the latter had more positive effects on dough and bread properties mainly due to its more hydrophilic molecular property. Higher water absorption, improved dough stability time, softer bread texture and higher volume, as well as greater acceptability were all observed when hydroxypropylmethyl cellulose was added in bread recipe.

Production of lysine by Corynebacterium glutamicum (PTCC 1532) from different agricultural by-products (molasses and pulpy waste date) was compared to glucose as raw materials. For this purpose, ammonium sulphate was selected as a constant nitrogen source. The effect of different nitrogen sources was also investigated with glucose as a constant carbon source. The production of L-lysine was examined qualitatively and quantitatively using thin layer chromatography (TLC). Results of fermentation experiments showed that the maximum yield corresponded to molasses (48 g L-1) for the fermentation period of 96 hours. For other substrates the yield was lower and the period of fermentation exceeded that for molasses.

Cellulase production by the fungus Trichoderma reesei was studied using sugar beet pulp (SBP) as a substrate. The subculture medium was a salt solution consisting of KH2PO4, CaCl2, etc. Fungal cells were sub-cultured in an orbital shaker (180 rpm) at 30°C for 1-2 generations (two days for each generation) and were then used as an inoculum. Exponential cells were inoculated into a medium containing SBP. Data showed that cellulose in SBP has a potential to be used as a substrate to produce cellulase. The effect of cellulose concentration on cellulase production was investigated. Using the medium composition (the mixture of chemical salts and SBP substrate) and a fermentation time of 4-6 days, a maximum cellulase activity of 0.46 IU/ml of filter paper activity was obtained.

Some physical properties and chemical compositions of two cultivars (Semsouri and Shahabadi) of cantaloupe studied during four different stages of maturity from fruit set to completely ripe. The physical properties investigated were the geometric mean diameter (GMD), specific gravity (SG), mean firmness (MF), rind, seed (%) and flesh (%). The chemical compositions were Brix, Titrable Acidity (TA), moisture content, pH, and ash. The results showed that the GMD, flesh (%), Brix, and pH values of both cultivars increased in the full-ripe stage of maturity whereas there was concurrent decrease in SG, rind (%), seed (%), moisture content, TA, and ash values obtained in the same period. There were also significant differences (using GLM-multivariate analysis) in all measured variables apart from ash, seed (%), rind (%), and flesh (%) between the two cultivars. Overall, the linear relationships were obtained between sugar content and GMD, SG, and MF respectively, correlation coefficients being higher than 0.87.