Iran is not rich in forest land and only 7.5 per cent of country is covered by forest. Therefore Iran has to import wood based panel annually. It is estimated that 100.000.000 Date Palms trees covered an area at about 770.000 hectares around world, and Iran has got 220.000 ha. Because of several reasons Date palm trees should be pruned and each tree produce 10-20 kg residues annually. In this study, for making boards Date Palm pruning residues as raw material and employed UF resin as the binder. Steaming time (5 and 8 Min.), steaming temperature (135 and 145oC) and press time (1, 2 and 3 Min.) were used as variable factors and three boards were made in Pilot plant scale for each combination of variables. Samples of all made boards were tested by the methods of EN to obtain mean values of bending strength, and internal bond strength (I.B). In addition samples of each type of board were tested for thickness swelling after soaking in water for 2 hours and 24 hours respectively.The results of this study show clearly that boards have higher mechanical properties than the MDF property requirements which are recommended by EN standard.

Incorporation of plant residues in soils of semiarid to arid regions is a major principle of sustainable agriculture. Soil N dynamics will be influenced differently following incorporation of various plant residues and it will consequently influence the availability of N for succeeding crop. It is of great importance to understand the effect of soil type on N transformations in plant residue-amended soils. The main objective of this study was to investigate the effects of plant residue and soil types on the N mineralization in plant residue-amended soils. For this purpose, two different soils including Shervedan (clay) and Jouzdan (sandy clay loam) soil were selected and alfalfa, wheat and corn residues were incorporated at the rate of 1% plant residue C kg-1 soil. A control treatment (without addition of plant residues was also considered for both soils). The rate of net N mineralization was measured at the end of 8-week incubation period. Results indicated that among the plant residues, alfalfa residues induced the highest quantities of N mineralization whereas, N immobilization occurred in corn residue-amended soils (based on the average replications of the two soils). Wheat residue-amended soils showed N mineralization to a lower extent compared to alfalfa residue – incorporated soils. The soil type had a significant effect on N mineralization however, the differences between soils were not observed similarly in the three plant residues-amended treatments. The differences in N mineralization of the two soils were much more pronounced in alfalfa residue-treated than those of wheat or corn-residue treated soils. The differences in N mineralization as affected by the soil type were also significant in wheat residue-treated soil but no significant difference was observed between the two soils when treated with corn residues. Overall, we conclude that the results support the hypothesis that, the effects of soil type on N mineralization is heavily affected by the plant residues quality.

Co-firing biomass plants are of extensive demand due to utilization of both agricultural residues (main) and natural gas (stand-by). Researchers have shown that one strategic decision in establishment of agricultural residues based plants, is location optimization problem. Moreover, mismatch between agricultural lands and biomass plants can lead to high transportation costs and related carbon dioxide emissions. Standard indicators are considered and used for the stated multi-objective mathematical problem. This article presents a novel approach based on Z-number data envelopment analysis (DEA) model to handle severe uncertainty associated with actual data. The multi-objective mathematical model considers environmental, economic and social aspects of biomass plants. Moreover, fuzzy DEA model is utilized to verify and validate the results of Z-number DEA model through 30 independent experiments. The obtained results indicate that “ accessibility to water” , “ population” , “ cost of land” , and “ unemployment rate” are the most significant factors in location optimization of co-firing power plants. The obtained results also indicate that “ Ilam” , “ Semnan” , “ Kohgiluyeh and Boyer-ahmad” , “ South Khorasan” , and “ Chaharmahal and Bakhttiari” are the optimum locations. This is the first unique approach for location optimization of co-firing plants based on combined agricultural residues and natural gas under uncertainty. Second, a unique fuzzy mathematical optimization approach is presented. Third, it is a practical approach for biomass power plants.

Background and Objectives: The ways of dealing with density include control of soil moisture during tillage, the control of vehicle's traffic on the soil, weight reduction and vehicle's contact pressure with soil and changing of soil structure by adding organic material.Materials and Methods: In order to study the effect of organic materials and zeolite and their mutual effect at different moisture stages on resistance to pentrometer penetration, organic material factor in four levels (0, 0.5, 1 and 1.5 percent), zeolite factor in four levels (0, 8, 16 and 24 tons per hectare), also soil moisture levels which are in two dry and wet stages at five levels (saturation, capillary crack, final crack, return final crack to capillary crack and when the crack have destroyed) were examined in three replicates as the factorial based on complete randomized blocks design in Rice Research Institute.Results: The results showed that adding plant residues has increased resistance to pentrometer penetration in soil to 37 percent, the reason of increased resistance to pentrometer penetration in treatments containing plant residues, is the levels of plant residues which aren' t decomposed. While adding plant residues causes reduced resistance to pentrometer penetration will accelerate in wet process. It was also found that resistance to pentrometer penetration with subsidence of soil, volume shrinkage of soil, bulk density and soil moisture content highly correlated (0.7811-0.9916).Conclusion: Finally it's recommended that in order to reduce of the resistance to pentrometer penetration, plant residues must be added to the soil for long time.

To study the nitrogen effects and plant residues management on the yield of rice ratoon, Tarom Hashemi rice, an experiment was performed in the research farm of Islamic Azad university of Chalus in 2010. The experiment was performed as a split plot design based on completely randomized blocks design with four replications. In this experiment nitrogen fertilizer rate was considered as the main factor in four levels (0,60,120,180 kg N ha-1) and plant residues management was considered as the secondary factor in three levels (standing with 40 cm height, lodging stubble with 40 cm height and ground cutting). Results showed that nitrogen fertilizer rates had significant effects on grain, straw, biologic yield and the number of cluster per square meter, numbers of tiller, numbers of effective tiller, and the stem height. Highest rate of grain yield included 290 g/m2 that were related to the use of 180 kg of nitrogen per hectare. Grain yield had a significant and positive correlation coefficient with the number of tillers in mass and the number of fertilized tillers in mass at the 1% probability level. And grain yield had a significant and positive correlation with the number of cluster per square meter at 5% probability level. Moreover, despite the fact that the rates of fertilizers used are statistically in the same level, but using 60 kg nitrogen per hectare is recommended. Plant residues management method did not have any significant effect on the yield of ratoon grain.

Carbon (C) and organic nitrogen (N) mineralization processes play key roles in supplying nutrient elements essential for plant growth. On the other hand, since the low organic matter content of agricultural soils of arid and semi-arid areas, microbial activities are often limited by carbon in these types of soils. Enhancement of microbial activities and populations could be achieved by returning plant residues to soil. Application of such acid-producing materials as sulfur may eliminate low uptake of some nutrients and slow decomposition of plant residue in calcareous soils, respectively in short and long-term in these soils. Therefore, the purpose of this study was to evaluate the interactive effects of plant residue and sulfur additions on microbial activities including C and N mineralization as well as their mineralization rates in a calcareous soil from Iran. This study was performed using a factorial experiment arranged in a Completely Randomized Design (CRD) with three replications under laboratory incubation conditions. Treatments included were different plant residues (i.e., wheat, alfalfa, corn, rice, almond, walnut as well as grape) and sulfur levels (i.e. 0, 5 and 10 t ha-1). We evaluated effects of plant residue and sulfur applications on C and N mineralization to over 97 days of incubation period. Results show that plant residue application had a positive and significant effect on carbon and nitrogen mineralization and their mineralization rates, and led to C mineralization enhancement up to two fold. The effect of plant residue on N mineralization depends on the chemical quality and C/N ratio of the residue. The effect of sulfur additions on C mineralization and its mineralization rate was highly significant, as it caused an increase in microbial respiration during incubation time but its addition didn’t have significant effect on N mineralization and its mineralization rate. The interactive effects of plant residue and sulfur utilization on C and N mineralization primarily depend on chemical quality of plant residues and the level of applied sulfur. Briefly, the residues with more recalcitrant compounds such as lignin, showed less microbial activities.

An option for improving soil physical, chemical and biological properties and carbon sequestration is by increasing organic carbon (OC) input through recycling of crop residues and organic manures. The objective of this study was to determine the degradation of some plant residues and the influence of application of plant residue on different chemical and biological forms of OC in soil. The was sampledsoil from the top 30-cm layer of an agricultural land treated with mild (d<2 mm)alfalfa, wheat and sawdust residues, at a rate of 20 g kg-1 (dry weight basis) and incubated in field capacity and lab temperature conditions. After 1, 20, 60 and 120days of incubation a portion of each soil were taken for analysis. The experiment was considered a completely randomized design as factorial in three replicates. The factors were residues type and the passing time of incubation. Microbial biomass carbon (MBC) increased in all treatments significantly. It increased to the highest values in soil treated with alfalfa (0.472 g kg-1) and wheat (0.372 g kg-1) straws in20th day of soil incubation. But it increased slowly and continuously in sawdustamended soil during incubation. The application of plant residue especially alfalfa and wheat straws in soil increased cold water (CW) and hot water (HW)extractable OC significantly. They were 1.75 and 7.15 g kg-1 in alfalfa straw treated soils and 1.13 and 4.40 g kg-1 in wheat straw treated soils respectively in 1st day of soil incubation. They were significantly higher than those in sawdust treated soil(1.07 and 2.92 g kg-1 soil). Although fulvic acid fraction increased significantly in soil treated with alfalfa and wheat straws in early stages of incubation, but thead dition of plant residues did not increase soil fulvic acid in late stages of soilincubation. The increase of humic acid was only significant in alfalfa treated soil. Itincreased the highest value in alfalfa treated soil (5.04 g kg-1) in 120th day of soilincubation. The study of changes of different chemical and biological fractions of OC during soil incubation and their correlations revealed that MBC had high dependence and coherence with fulvic acid, CW and HW extractable OC.

Introduction Prediction of mineralization rate of organic carbon and nitrogen amounts of plant residues is important due to plant nutrient management, carbon dioxide production and environmental issues. Plant residues characteristics such as total nitrogen content (N), carbon: nitrogen (C/N), lignin content and particle size, Soil characteristics (texture, structure, pH and the microbial population) and Climate (temperature and moisture) are the most important factors affecting plant residues decomposition. Decomposition process of plant residues is influenced by substrate quality, decomposer community and environmental factors. Within a given climatic region, litter chemistry is the main determinant of litter decomposition. Litter decay and nutrient release are controlled by the litter quality, including the nitrogen (N) concentration of the litter, the carbon to nitrogen (C/N) ratio, as well as other chemical properties. Materials and methods To investigate the effects of size and placement depth of plant residues on organic carbon and nitrogen dynamics, a split – split plot layout based on a randomized complete block design and three replications was conducted using litter bag method. The factors were depths of incubation periods of plant residues (1, 2, 3 and 4 months), placement of plant residues (5, 15, 30 and 45 cm) and sizes of plant residues (0. 2-0. 5, 1-2 and 5-10 cm) which were located in main, sub and sub-sub plots respectively. At the end of the incubation period, the litter bags were pulled out of the pots; after the weights of the remaining plant residues in the bags were measured, the residue organic carbon was measured via the dry combustion method at 450° C for 5 h and the total nitrogen via the kjeldahl method. We analyzed the collected data during desert-lab studies by SAS/STAT software release 9. 1. Statistical differences among size and placement depth of plant residues and time duration were determined using a generalized linear model (Proc GLM), P ≤ 0. 05 and LSMEANS, which allows mean comparisons even when data points are missing. Results and discussion Results of data variance decomposition indicated that size and placement depth of plant residues had a significant effect on carbon and nitrogen loss at the probable level of 1℅ . The highest organic carbon and nitrogen loss were measured after four month of incubation and when the size and the depth of placement of plant residues were 0. 2-0. 5 and 30 cm, respectively. The lowest organic carbon and nitrogen loss were also obtained after the first month of incubation and when the size and the depth of placement of plant residues were 5-10 and 5 cm, respectively. After four months of incubation 49. 73 and 54. 07% of organic carbon and 34. 48 and 39. 78 of organic nitrogen of plant residues mineralized when the depths of placement of plant residues were 5 and 30cm respectively. Aridity, soil hilling and availability to nutrients are determining factors of the carbon cycle in the decomposition process. Conceptually and analytically advanced models from diverse studies suggest three factors affecting decomposition in arid ecosystems: quality and quantity of the organic matter under decomposition, the physical environment (including temperature, precipitation and soil type) and the nature and entity of the decomposing organs in the soil. Conclusion From the results it was concluded that when the soil moisture level is a limiting factor for plant residue mineralization, increasing the depth of placement of plant residues enhances the rate of mineralization of organic carbon by providing sufficient moisture for plant residues decomposition. The results also showed that reducing plant residues particle size with increases the surface area and plant residues contact with the soil, enhances the rate of decomposition of plant residues.