حمیدرضا صادق نژاد

This research was conducted in order to introduce a conservation tillage method suitable for dry seeded rice in Golestan province for one year and in the form of a completely randomized block design in three replications in the residues of the previous crop (wheat). The independent variable of the experiment included 5 treatments, which include no-tillage with a direct seeding machine, minimum tillage with a combination tillage machine at a depth of 15 cm + leveler + planting rice seeds with a seed drill, minimum tillage with a chisel packer at a depth of 15 cm + leveler + planting rice seeds with seed drill, minimum tillage with disc at a depth of 10 cm + leveler + planting rice seeds with seed drill and conventional tillage at a depth of 25 cm + transplanting (control). The parameters that were measured and calculated in this research were: the time required for tillage and planting operations, the field capacity of tillage and planting machines, the number of established plants, yield, yield components (number of clusters per square meter, plant height, spike length, number of healthy seeds in a spike, number of effective and ineffective tillers), dry biomass, dry harvest index and 1000 seed weight. The results showed that the minimum time required for tillage and planting operations is 1.4 hours per hectare and the highest field capacity belongs to no-tillage treatment with 3.7 hectares per hour. The maximum time required for tillage and planting operations in the conventional treatment is 456.7 hours due to considering the time of preparation of rice seedlings as well as manual planting of seedlings. Although the effect of tillage in the preparation of the seedbed to obtain the yield is significant, but among the conservation tillage methods, apart from no-tillage, due to the non-significance of the results of the yield components, the yield is also was not significant and its values ​​were lower than the grain yield in the conventional treatment. Therefore, among the treatments, the highest average grain yield and harvest index were obtained in the conventional treatment, equal to 5238 kg/ha and 51.4%, respectively.

In no-tillage, the coulters are the best way to cross the plant residues, which, along with the furrow openers, prepare the soil for seed placement. So four available tiller models in front of a mechanical row crop planter were installed and a two factor randomized complete block design using strip plots with four coulters (sweep, nail, narrow chisel and T inverted) as factor A and the three factors related to the speed of tractor (4.8, 7.2 and 9.4 km.h-1) as factor B were performed. The planter units were adjusted on 50 cm distance between rows. The sweep model with 24.4 and 7.3 cm had the highest width and depth of disturbed soil. T inverted tiller at the specified depth with the least amount of standard deviation got the highest uniformity of seed distribution on the row that was 80.4% and did not change depth of seeding by speed increasing but increased the distance between two seeds. Also, the highest quality of feed index (42.7%) and the lowest multiple index (46.8%) were related to this treatment and its miss index (10.5%) has been around other tillers. Although T inverted tiller in the forward speed of 4.8 km h-1 has better performance in terms of planting indices, but the nail tiller is more suitable because of simplicity and performance as well as its low cost compared to other tested tillers and it passes through plant residues more easily.

Currently, the area of agricultural land under  conservation practices in the world exceeds 180 million hectares, one of the main advantages of which is improvement in crop water productivity (CWP). An investigation in soybean cultivation  in a farm with different level of management of residues was carried out in a randomized complete block design with split plot design in 2010 and 2011 at Gorgan Agriculture Research Station. Main treatment was residue management at three levels: R1: burning of residue , R2: retaining 50% of residues, and R3: maintaining 100% of residues; the secondry treatment was tillage practises at three levels: T1: conventional tillage (plowing + disk + row crop planter), T2: minimum tillage (stubble cultivator + row crop planter) and T3: no tillage (sowing with no till planter). The best results obtained from R2 and T3: 42.7% and 17.4% increase in yield respectively, comparing R1 and T1. The highest and lowest of water consumption level were found  3950 m3 ha-1 and 2690 m3 ha-1 in  R1 and R3 respectively. The maximum and minimum CWP were found in R2 and R1 treatments with 1.13 kg m-3and 0.55 kg m-3 respectively. Sowing with no tillage system in irrigated conditions improved CWP by 15.3% compared to the conventional method.

Nowadays, agricultural systems are seeking economic, ecological and bioenvironmental goals for production of agricultural crops with protection and sustainability of the environment. Therefore, there is need to extend sustainable agricultural systems such as conservation agriculture. One of the principles of conservation agriculture is conservation tillage. Conservation tillage is a kind of tillage that retains crop residues on the soil surface or mixes it with soil using related machines. It could also affect on machine performance parameters. Energy consumption for producing one kilogram crop could be studied for conservation tillage. Several researchers have conducted studies on this issue for production of different crops including wheat, sunflower and forage crops. This study conducted to assess machine performance parameters and energy indices of conservation tillage systems for soybean cultivation in Golestan province.
This study was conducted to investigate the effects of conservation tillage systems on machine performance and energy indices in soybean production at the Gorgan research station of Golestan Agricultural and Natural Resource Research Center in 2012. The precipitation was 450 mm. Soil texture was silty clay loam. Treatments were four tillage methods, including no-till using row crop direct planter, no-till using grain direct drill, conventional tillage usin a disk harrow with working depth of 10-15 cm and minimum tillage using chisel packer with a working depth of 20 cm. Machine performance parameters and energy indices studied in a farm covered by wheat residues in a randomized complete block design (RCBD) with four treatments and four replications. Machine performance parameters consisted of field efficiency, field capacity, total field capacity and planting uniformity index were measured. Energy indices such as energy ratio, energy productivity, energy intensity and net energy gain were also calculated.
The results showed that no-tillage methods by grain drill and row crop planter had the lowest field efficiency (56% and 58.9%, respectively), but had the highest field capacity (0.76 and 0.71 ha h-1, respectively), as the passage of implements in the field was less than that of conventional tillage. Peruzi et al., (1996) also reported that required time for minimum tillage and no-till was 80% less than conventional tillage. No-till using grain drill with the total field capacity of 0.76 ha h-1 and conventional tillage with 0.33 ha h-1 had the highest and lowest field capacity among the treatments, respectively. Minimum tillage had the best horizontal distribution uniformity for seed placement on the row. No-till using seed drill had the highest energy ratio of 4.5 and yield of 3612 kg ha-1, which were higher than the other treatments. No-till also produced 0.19 kg crop per each MJ energy consumption. It consumed the lowest amount of energy with 5.3 MJ for production of 1 kg soybean and had the highest net energy gain among treatments. Minimum tillage had the lowest consumption of energy with 2030.2 MJ ha-1 among the treatments. It had the lowest amount of net energy gain because of having lowest yield (2794 kg ha-1). Zentner et al., (2004) and Razzaghi et al., (2012) also concluded that conservation tillage systems had the lowest amount of energy consumption compared to the conventional tillage.
The study of energy indices is important for producing agricultural crops to decrease energy consumption. Among the tillage methods, no-till method had the best indices about reducing energy consumption. Although the size of no-till grain drill will increase the weight and energy consumption of machine, but it well penetrates on the soil. Results showed that minimum tillage and no-till methods are proper alternatives for replacement of conventional method for producing soybean, according to the precise of planting and improvement of energy indices. However, the existing planters can be modified for row crops and increasing of planting accuracy indices with correct management of no-till methods at crop protection stages. It can also help to localize conservation tillage implements and speeding up new methods for reaching to sustainable energy and production resources.

The most common morphology of mandibular molars is two roots and three root canals; nonetheless, unusual anatomic variations may exist.
Case reports: This study reports two cases of mandibular first molars with a mid-mesial root canal that underwent treatment and follow-up in the Endodontics Department of Isfahan School of Dentistry. During the initial treatment, the mid-mesial root canal had not been detected in both cases due to the failure to prepare a convenient access cavity.
Preparation of convenient access cavity, knowledge of canal anatomy and presence of uncommon variations should be more appropriately taken into account during the general training and systematic re-training programs of general dental practitioners.

After cleaning and shaping of the root canal, to prevent recontamination and to ensure the success of root canal therapy, it is necessary to fill root canal space. Studies, so far, have not been able to identify a specific method as the best method of obturation. The present study was an attempt to introduce and compare different root canal obturation techniques. In this review, using specific key words such as root canal obturation, root canal filling materials and gutta-percha, search was run in Pubmed, Cochrane and ISI Web of Science databases for high-quality articles published from 1960 to 2013. There are several methods to obturate the root canal system, designed based on the use of plastic materials, injectable materials, single cones, or compaction of gutta-percha. A brief review of each technique and its advantages and disadvantages were discussed. The reasons for choosing the cold lateral compaction technique as a frequently used and the selected technique by many dentists as well as academic centers were explained. Considering the advantages and disadvantages and long-term outcomes of root canal obturation techniques, it seems cold lateral compaction is the selected root canal filling technique in the majority of cases.

The conservation system is one of the proper methods avoiding the loss of nutrients, soil erosion, and reduce production costs. This research was examined for studying the influences of tillage systems on the three cotton cultivars at Karkandeh and Hashm-Abad stations in Gorgan. The experiments were conducted in a randomized completely block design as split plot with three replications with five tillage systems (Mould board plough, Chisel, Disc, Strip and no tillage) as main plot and three cultivars (Siokra324, Zodrac-Motagenez and Cindoz 80) as sup-plot. The results showed that effects of tillage system was significant on yield. Yield was more in chisel and disk (Conservation tillage) by having more monopodial branch length, number of monopodial and sympodial branch, plant height and boll in plant than Mould board plough (conventional tillage) and no-tillage system in all cultivars. The Siokra324 cultivar had more yield due to having more boll in plant than two other cultivars. Yield in no-tillage system was lower than conservation and conventional tillage but the grown plants in this system were smaller and had lower branching. Thus population density can be increased for gaining higher yield from this system, and it is recommended to do complete experiments for studying the effects of various population densities in no tillage system and conservation tillage with the conclusive studies are replaced conventional tillage.