JOURNAL OF AGRICULTURAL SCIENCE AND TECHNOLOGY (JAST)
Year:2011 | Volume:13 | Issue:5|Papers Count:16

External fluted feed rolls are commonly used in grain drills. The fluted feed roll meters a volume of seeds and does not singulate the seeds as do the precision planters; therefore, there will be inherent variation in the number of seeds delivered per unit of time. This research was conducted to investigate the effect of seed meter drive shaft and ground speeds and outlet positions in a grain drill on the variation in wheat seeding rate and seed flow evenness from various outlets in short time intervals using the coefficient of variation (CV) and the nonuniformity coefficient (NUC). In this study, a grain drill with straight fluted metering mechanisms was evaluated on a test rig. Two rotational speeds of 16 and 23 rpm and two speeds of 2.5 and 3.6 km h-1 were selected for the seed meter drive shaft and the movement of the test rig, respectively. The results showed that, for a given test rig speed, the seeding rate changed proportional to the seed meter drive shaft speed, whereas for a constant speed of seed meter drive shaft, the seeding rate decreased as the speed of the test rig increased. Also, the seeding rates from all outlets were not the same. Outputs of some of the outlets were autocorrelated, for which selecting 12 or 24 seed samples randomly out of 36 consecutive samples were not essentially non-autocorrelated. Increasing rotational speed of seed meter drive shaft significantly increased the coefficient of uniformity of all outlets. The seed breakage was significantly increased with the speed of seed meter drive shaft. The CV and NUC exhibited similar trends. It can, therefore, be concluded that in grain drill evaluation, either CV or NUC could be used as an index of seed flow non-uniformity.

The objective of this study was to investigate the drying kinetics of oyster mushroom, Pleurotus ostreatus Mushrooms were dried using a cabinet-type convective dryer. Air temperatures of 50, 60 and 70oC were used for the drying experiments. The experimental drying data were fitted to different theoretical models to predict the drying kinetics. Nonlinear regression analysis was performed to relate the parameters of the model with the drying conditions. The performance of these models was evaluated by comparing the correlation coefficient (R2), root mean square error (RMSE) and the chi-square (X2) between the observed and the predicted moisture ratios. Among all the models, the model of Midilli et al. was found to have the best fit in this study. Effective moisture diffusivities (Deff), diffusivity constant (D0) and activation energy (Ea) were calculated. The Deff varied from 9.619x10-10 to 1.556x10-9 m2s-1 over the temperature range studied and Ea was 22.228 kJ mol-1.

Knowledge of resistance to airflow through agricultural products is an important consideration in the design of drying, cooling, or aeration systems and proper fan selection for these systems. Resistance to airflow of bulk chickpea seeds was studied at moisture contents in the range of 9.21 to 21.36 % (wet basis) for airflow rate range from 0.02 to 0.50 m3 s-1 m-2, using an experimental test column. The effects of airflow rate, bed depth (0.25 to 1 m) fill method (loose and dense) and moisture content on airflow resistance of chickpea samples were investigated. Results indicated that the airflow resistance of chickpea seeds increased with increase in airflow rate, bed depth, and decreased moisture content. One percent increase in moisture content decreased the pressure drop about 2.94%. The dense fill method resulted in an increase in resistance to airflow by about 33.17% more than that of the loose fill. Three models (Shedd’s, Hukill and Ives’s, and Ergun’s models) were fitted to the experimental data at each moisture level and were examined with two parameters. Shedd’s model that gave a higher value for the coefficient of determination and a lower value for the mean relative percentage error of pressure drop predication was found to be the best model to describe airflow resistance of chickpea seeds.

Green fig, which is usually consumed as dry fruit, is one of the important non-oil export agricultural commodities of Iran. In this study, some important physical properties of green figs including geometric mean diamter, sphericity, porosity, particle and bulk density and pressure drop across a thin bed were measured at constant moisture content of 6% (dry basis). Air flow ranges used in this study were 0.4-1.0 m3 s-1 m-2 at three temperatures. The fig kernels were put together in thin layers in four different arrangements. The effect of filling methods and air flow rates on pressure drop were highly significant, while the air temperature did not show any appreciable effect on air flow resistance. Three applicable and most versatile models (Shedd, Hukill and Ives, and Ergun) were used to evaluate the pressure drop data. The Ergun model, with higher values of coefficient of determination (R2=0.989) and lower value of root mean square error (RMSE=21.84) and mean relative deviation modulus (P%=6.69), was selected to be the best model for predicting pressure drop across green figs thin layer bed for the conditions studied.

Many Phragmites-dominated wetlands have been markedly salinized and alkalinized in the Songnen Plain, northeastern China. Agricultural wastewater with high nitrogen content has been discharged into these alkalinized-salinized wetlands. To understand the effect of salinity-alkalinity on reed (Phragmites australis) seedlings at various nitrogen levels, we examined photosynthesis rate, chlorophyll fluorescence characteristics, and chlorophyll content of reed seedlings using gas exchange and chlorophyll a fluorescence tests. The greatest decreases (by 82%, 15%, 82% and 98%) of net photosynthesis rate (Pn), maximal efficiency of photosystem II (PSII) photochemistry (FV/FM), comprehensive photosynthesis performance index (PIABS) and plant height growth rate were observed at high salinity-alkalinity (mixed with 150 mM NaCl and 100 mM NaHCO3). Stomatal limitation was the main reason for decreased photosynthesis rate at low salinity-alkalinity (mixed with 50 mM NaCl and 25 mM NaHCO3). The activity of PSII was significantly inhibited at high salinity-alkalinity. Both donor and acceptor sides of PSII are the target sites of high salinity-alkalinity. High N (30 mM) at low salinity-alkalinity and moderate N (15 mM) at high salinity-alkalinity mitigated the toxicity of salinity-alkalinity on reeds and promoted plant height growth, chlorophyll synthesis, and PSII activity. Proper levels of N partly reduced the toxicity of salinity-alkalinity on the donor and acceptor sides of PSII. This suggests that agricultural wastewater containing high level of nitrogen may be helpful in restoration of Phragmites-dominated salinized wetland, though the N level needed for salinity-alkalinity stressed reed varies with the salinity-alkalinity level.

Crossbreeding of four Iranian fat-tailed sheep breeds, namely Kurdi (K), Chaal (C), Afshari (A) and Sanjabi (S) was carried out to determine the ram breed effects on productivity of Kurdi fat-tailed ewes (K) under extensive production system. A total of 475 Kurdi ewes were mated to 24 rams from the above four breeds resulting in 454 lambs. Ram breed had a significant influence on early growth traits of the lambs. Lambs sired by C rams were heavier than the other lambs (P<0.05) at birth and weaning. Body weight at 160 days of age (W160) in crossbred lambs was significantly higher than that of the purebred lambs while crossbred lambs for W160 were similar (P>0.05).Greasy fleece weight of lambs at first shearing (GFW) and fat-tail measurements were significantly affected by ram breed. Number of lambs born and number of lambs weaned per ewe lambed or per ewe joined were similar among the four groups, whereas there was significant effect on productivity. In general, ewes mated to Chaal ram had higher productivity than those mated to other ram breeds.

This study was conducted to determine the nutritive value of fresh and ensiled whole and partly stoned olive cake (OC) with or without molasses i.e., 0 and 50 gkg-1 on fresh basis. Dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (sa), ether extract (EE), water soluble carbohydrates (WSC), and total phenols (TPH) of all treatments were determined by laboratory analysis. Additionally, pH and the concentration of ammonia-N, lactic acid, and volatile fatty acids were measured in the ensiled treatments. An in vitro gas production for 24 h was used to estimate organic matter digestibility (OMD) and metabolizable energy content. Ensiling OC decreased (P<0.05) DM, pH, EE, WSC, TPH and OMD, and increased (P<0.05) NDF, ADF and lignin (sa) contents. Addition of molasses decreased (P<0.05) OM, NDF, ADF, lignin (sa) and pH, but increased (P<0.05) DM, WSC, OMD and lactic acid. In conclusion, based on these results, the potential to use of OC as a feed in diets of ruminants is limited.

Land use optimization is one of the appropriate methods for soil conservation programs that allow watershed managers and decision makers to choose the best land use practices. With the objective of optimizing land use to minimize soil erosion, the present research was conducted in one of the Taleghan sub-basins in Iran, namely, Orazan sub-basin, with an area of 2, 706 ha. To achieve the objective, the area, the erosion rate, and the net income value of each land use was assessed according to the pertinent standards. Then, limitations and objective functions were determined and the optimization problem was solved by using Steuer method (1995) and ADBASE software. The results revealed that optimizing land use while taking into consideration the legal restrictions (Article 56 of The Forest and Rangeland Nationalization Law) leads to a decrease of 10.29 percent in erosion rate (from 18253.39 t y-1 to 16373.51 t y-1) and 17.71 percent lower net income (from 2, 382.12 to 1, 960.28 million Rials). In contrast, optimization without consideration to legal restrictions would result in 22.24 percent increase in the net income and 6.93 percent decrease in erosion rate.

A study was conducted to determine suitable soil properties as soil quality indicators, using factor analysis in order to evaluate the effects of land use change on loessial hillslope soils of the Shastkola District in Golestan Province, northern Iran. To this end, forty surface soil (0-30 cm) samples were collected from four adjacent sites with the following land uses systems: (1) natural forest, (2) cultivated land, (3) land reforested with olive, and (4) land reforested with Cupressus. Fourteen soil chemical, physical, and biological properties were measured. Factor analysis (FA) revealed that mean weight diameter (MWD), water stable aggregates (WSA), soil organic matter (SOM), and total nitrogen (TN) were suitable for assessing the soil quality in the given ecosystem for monitoring the land use change effects. The results of analysis of variance (ANOVA) and mean comparison showed that there were significant (P<0.01) differences among the four treatments with regard to SOM, MWD, and sand content. Clearing of the hardwood forest and tillage practices during 40 years led to a decrease in SOM by 71.5%.Cultivation of the deforested land decreased MWD by 52% and increased sand by 252%.The reforestation of degraded land with olive and Cupressus increased SOM by about 49% and 72%, respectively, compared to the cultivated control soil. Reforestation with olive increased MWD by 81% and reforestation with Cupressus increased MWD by 83.6%. The study showed that forest clearing followed by cultivation of the loessial hilly slopes resulted in the decline of the soil quality attributes, while reforestation improved them in the study area.

Consumption of whole-wheat breads prepared from high extraction flours is recommended because of their high content of fiber, vitamins, and minerals. Despite the beneficial effects of these breads, they contain high amounts of undesirable compounds like Phytic Acid (PA) which is believed to negatively interfere with the absorption of some such nutrients as zinc (Zn). Wheat genotypes are different in their PA and Zn concentrations; therefore, cereal-based foods may be prepared using grains of low PA and high Zn. Fars Province is ranked first in Iran in terms of wheat production. It is, therefore, important to evaluate the PA and Zn status of the wheat cultivars common in the province. Seventeen wheat cultivars obtained from Genotype Improvement Department of Fars Agricultural Research Center, Zarghan, Iran were employed in the study. These cultivars that are commonly used by local farmers were grown in test plots under identical conditions. A wheat grain sample from Parvardeh Wheat Milling Factory and 7 bread flour samples from Shiraz city's bakeries were also included in the study. The PA content and phytase activity of the grains either with or without bran as well as those of the flour samples were determined. Results showed that the method of grain debranning significantly affectted the concentration of PA and phytase activity. The least phytic acid was found in Pavarus and Niknejad cultivars. The PA to Zn molar ratios were highest in Falat, Niknejad and Shiraz cultivars. The highest concentration of Zn was observed in Estar, Falat, and Niknejad, while maximum phytase activity was found in cultivars Estar, S-78-11, S-79-10, and Niknejad.

Erosion is considered as a main problem for the loss of arable land around the world. As the world arable land is reaching its limit, marginal areas, such as those prone to wind erosion, have gained importance for agricultural use. A simple and effective way of restoring wind eroded soils is addition of organic materials. Sewage sludge can be an effective way to solve this problem. The effect of sewage sludge application on some physical and chemical properties of a soil affected by wind erosion was studied during 2004 - 2007 in Igdir plain (Aralik), Turkey. Sewage sludge was applied at the rates of 0, 40, 80 and 120 t ha-1 (dry weight). The experiments were conducted for three years using a complete randomized block design with three replications in 12 plots, where barley (Hordeum vulgare) was sown. Sewage sludge application not only improved the physical and chemical properties of the soil, but also increased barley yield. However, increased yield was not sufficiently high. In order to achieve satisfactory yields, annual application of sewage sludge at the rate of, at least, 40 t ha-1 is required.

A long-term rotation experiment was established in 2001 to compare conservation or reduced tillage systems (shallow rototiller and chisel tillage) with conventional tillage system using mouldboard plough in a semi-arid region with Mediterranean climate. Field experiments were conducted to determine weed density and profitability of cropping systems in a crop rotation of winter wheat (Triticum aestivum L.) -winter vetch (Vicia sativa L.) from 2001 to 2004 and winter wheat-winter vetch/summer maize (Zea mays L.) from 2004 to 2009. Results indicated that, rototiller markedly increased total weed density, as compared with mouldboard plough, by 72% and 58% in maize and vetch, respectively, while total weed density was statistically similar for the three tillage systems in wheat. Maize yield was significantly higher for rototiller and the lowest for chisel compared to mouldboard plough, but, there were no significant differences in wheat yield between the two tillage systems. Chisel and mouldboard plough resulted in a high yield of vetch in the last five years of the vetch growing season, but there were no significant differences in yield between tillage systems in the first three growing seasons of the crop. Based on market returns, gross margin over production costs were significantly higher for rototiller in wheat and maize when compared with mouldboard plough by 20.7% and 15.3%, respectively. Chisel production costs were similar to rototiller and lower than plough; but, chisel had a gross margin similar to mouldboard plough and higher than rototiller, in both vetch growing seasons. Time savings were 43% and 47% for rototiller and chisel, respectively, as compared with plough in wheat. The corresponding values in vetch and maize were, for rototiller, 46% and 50%, and, for chisel, 28% and 32%, respectively.

Field experiments were conducted to evaluate the effect of thiobencarb and oxadiargyl herbicides on rice (Oryza sativa L.) and their possible residual effects on spinach (Spinacea oleracea L.) and lettuce (Lactuca sativa L.) at Dashtnaz and Gharakhil Agricultural Research Stations, Iran. Treatments included thiobencarb at 3.16 and 6.33 kg a.i. ha-1, oxadiargyl at 0.15 and 0.30 kg a.i. ha-1 and a non-treated control. After harvesting rice, trial plots were kept undisturbed until late September when spinach was seeded in half of each plot. In November lettuce was transplanted in another half of the plots. Soil residual oxadiargyl at 0.30 kg a.i. ha-1 stunted rice up to 31%, but this injury was transient and did not reduce yield. The adverse effect of oxadiargyl on rice was lower at Gharakhil possibly due to the greater binding by soil organic matter (OM). At Dashtnaz, spinach fresh yield was significantly affected by soil residues of oxadiargyl. Whereas lettuce fresh yield was significantly reduced in both thiobencarb and oxadiargyl treated plots. At Gharakhil, fresh yield of lettuce was not affected significantly. The experimental results revealed that soil characteristics, in particular OM content, are the main factors controlling the effect of thiobencarb and oxadiargyl residues. Furthermore, it could be concluded that oxadiargyl affected rice and spinach fresh yield greater than thiobencarb. Since no statistically significant differences were found in rice, spinach, and lettuce yield between the two applied doses of thiobencarb, from economical and environmental point of view, the lower thiobencarb dose is recommended to be used in paddy fields of northern Iran.

Inoculation of phosphate-solubilizing microorganisms along with rock phosphate is known to enhance the available P from soil. The success of such solubilization is largely dependent on the ability of the inoculant strain to survive under adverse environmental conditions. In this context, liquid inoculants are gaining importance and are becoming popular with longer shelf-life. In the present investigation, a preliminary study was conducted to determine the survival of Bacillus megaterium in liquid formulations supplemented with osmo/cell-protectants under the influence of high temperature, desiccation stress and their subsequent influence on P-uptake by cowpea plants. Liquid inoculant-2 containing osmoprotectants viz., polyvinyl pyrrolidone (PVP), high quantity of glycerol (12 ml L-1) and glucose supported higher viable population up to a storage period of four weeks at 48oC (log10 10.62 CFU ml-1) and desiccation stress (log10 10.04 CFU ml-1) as compared to liquid inoculant-1 containing osmoprotectants viz., PVP, low quantity of glycerol (1 ml L-1), trehalose, arabinose and FeEDTA; and nutrient glucose broth without any osmoprotectants. Liquid inoculant-2 also enhanced the P-uptake of cowpea plants significantly.