Conceivably no major food crop other than wheat can compete with rice in the range of climatic and hydrologic conditions under which, it is grown. Rice is produced in every continent except antarctica and thrives in an area ranging in latitude from 55o to 40o. It grows as a dryland crop much like wheat or maize, as a rainfed crop under alternately submerge and dry conditions, and as a continuously flooded crop. Farmers grow rice on alluvial plains, flooded valleys, and terraced hillsides. Even though it has less drought tolerance than other cereals, rice grows well in arid areas under irrigation such as in Asia and north Africa. Likewise, despite rice's sensitivity to low temperature, yields are high in northern Japan and China and at elevations of more than 3,000 meters above sea level in the tropics and subtropics. Most paddy soils are located at lower positions in landscapes to permit water easy access from higher irrigation or natural surface runoff sources. These wetland rice areas may be flat-bottomed valleys or terraced and bounded hillsides of otherwise upland areas. But more often, they are found in alluvial flood plains, deltaic plains, coastal plains, tidal flats, marshes, and major river valleys. Such areas are generally characterized by a natural or induced "aquic" moisture regime that implies high moisture and low oxygen conditions. As a consequence of this high moisture-low oxygen requirement, the soil characteristics for paddy rice culture may vary less than those for upland or dryland rice.

Background and objectives: Rice is a very popular cereal in world and very important from economic point of viwe. The problems of drying paddy rice is lack of drying uniformity in the paddy rice that creates stress temperature and moisture and thus will cause losses in the later stages. The purpose of this research was to develop a high performance system for processing the paddy to healthy white rice in the shortest drying time. Materials and methods: In this study, to reduce losses and increase the drying rate, an innovative laboratory rotary dryer machine was used. The response surface methodology (RSM) with central composite design was used for modeling and determinimg the optimum processing conditions for paddy drying. Independent variables for this process were temperature (40 to 80° C), cylinder rotation speed (2 to 10 rpm) and the cylinder fullness (25 to 66%). The percentage of breakage, percentage of crack and drying time were used as response parameters to develop predictive models and optimize the drying process. Results: The results showed that the temperature, cylinder rotation speed and cylinder fullness had significant effect (P<0. 01) on the percentage of breakage, percentage of crack and drying time, as temperature was the most effective parameter. According to optimization process, the minimum losses (percentage of breakage and percentage of crack) and drying time were found with the inlet air temperature 56. 53 ° C, cylinder rotation speed of 10 rpm and the cylinder fullness of 54. 20%. Conclusion: Conditions and parameters of drying process had important rule in the final quality properties and losses of paddy rice. Our results revealed that RSM could be used to develop adequate prediction models for describing quality changes in paddy rice during drying. The changes in the quality parameters were adequately described by quadratic model. Also, the result showed that inlet temperature was more important than cylinder rotation speed and cylinder fullness on losses of paddy rice.

The intermittent drying characteristics of an Iranian popular paddy rice variety were experimentally investigated to determine the drying kinetics and obtain the effective moisture diffusivity. A lab-scale fluidized bed dryer was designed and constructed to enable obtaining the required results while controlling critical drying parameters. The effects of drying temperature and tempering period on drying kinetics and moisture diffusivity were studied. The results showed a significant effect on drying performance and effective moisture diffusivity by adding tempering stage. Drying rate improved sharply by implementing the tempering stage, increase of drying air temperature as well as the tempering duration. Several thin layer drying models were fitted separately to experimental data of each drying stages namely pre-tempering and post-tempering and suitability of these models were examined using the statistical analysis. The Midilli and Tow-Term model were found to be the most appropriate one for the first and second drying stages, respectively.

Rice is a major staple food consumed worldwide, but its processing has significant environmental impacts due to water and energy consumption and greenhouse gas emissions. As a result, rice producers are adopting sustainable processing techniques to reduce negative environmental impacts and increase profitability. This study analyzed the sustainability of modern and traditional paddy rice processing techniques among smallholder rice farmers in Southeast Nigeria. The data was collected from 240 rice producers using statistical approaches such as descriptive statistics, sustainability indicator (Weight Assessment Ratio Analysis), and multinomial regression analysis. The results showed that 34.7% of rice farmers used modern processing techniques while 65.3% used traditional methods. Traditional milling produced substantial carbon emissions, according to 77% of small-scale farmers, while 68% rated noise pollution as high. 80-100% of small-scale farmers using modern techniques cared about the environment and wanted to reduce their gas emissions, solid waste, energy use, and water use. The sustainability index for farmers using traditional and modern processing techniques was affected by gender experience, labor size, investment, income, cost of production, understanding of climate change, and environmental sustainability. The study recommends using renewable energy sources to increase productivity and reduce environmental effects.

Organic farming is more knowledge-intensive than input, and requires improving the knowledge of farmers. Langrud is considered as one of the important counties with a share of about 27% of rice production and one of the areas in demand for organic rice cultivation in Guilan. The purpose of this study was to investigate the awareness of paddy rice farmers in Langrud regarding organic farming. The statistical population was paddy rice farmers in three districts with 500 people in 2018. The sample size was 211 according to the minimum sample size of Bartlett et al. A simple random sampling method was used to select this sample size. Data were collected by questionnaire. Its face and content validity was based on a survey of opinion leaders and experts. The reliability of the measurement tool was performed by a completing a questionnaire from a sample of 30 people outside the original and calculating the Cronbach's alpha coefficients (0/7). To analyze the data, descriptive statistics, correlation tests and multiple regression were used and analyzed by SPSS22. The results showed that the level of knowledge of 84. 8% of the respondents was at a moderate and good level, which indicates the positive tendency of the statistical community to obtain the needed information.

The increasing of paddy production has environmental impact because paddy cultivation contributes to 46. 2% of the total greenhouse gas emissions from agriculture. The paddy cultivation emission amounted to 76% of methane. Meanwhile, the grain produced by paddy consists of 16. 3% to 28% husk with 18 to 22. 3% silica. Silica contained in the soil can increase the oxidation power of paddy root, thus it will reduce methane emissions. The objective of this research was to evaluate the reduction of methane emission from paddy field by using silica from rice husk. This research used an experiment with randomized block design based on eight treatments with three repetitions. The dose of biosilica was equal to 200 kg ha of ameliorant in the form of ash, biochar, and compost. The methane analysis was carried out in 1, 5, 8, 12, and 15 weeks after planting. The methane was analized by GC with FID. Results showed that the ash produced from rice husk was the best single source of biosilica in paddy soil that can reduce methane emissions by 80. 75%. The composition of ash, biochar, and compost (1: 1: 1) could increase the paddy growth and paddy production and reduce methane emissions effectively. The methane emission was reduced by adding silica to the soil through the dissolved silica mechanism. The dissolved silica increased pH and the root oxidation power of paddy.

IntroductionOn the field and in the paddy milling factory dryer losses have always been challenging issues in the rice industry. Different forms of losses in brown rice may occur depending on the field and factory conditions. To reduce the losses, proper management during pre-harvest, harvesting, and post-harvest operations is essential. In this study, different on-field drying and tempering methods were investigated to detect different forms of brown rice losses.Materials and MethodsThe present study was conducted on the most common Hashemi paddy variety during the 2019-2020 season in Talesh, Rezvanshahr, and Masal cities in the Guilan province, Iran with 0.2 hectares and 5 paddy milling factory dryers. On the fields, the method and date of tillage, irrigation, and transplanting used in all experimental units were the same. Moreover, the same amount of fertilizer and similar spraying methods were used across all experiments. For the pre-drying process on the fields, the following three pre-drying methods were applied on the harvest day: A1) The paddies were spread on the cut stems for insolating, A2) The paddies were stacked and stored after being placed on the cut stems for 5h, and A3) The paddies were covered with plastic wrap and stored after 5h of insolating. The first method (A1) is the most common in the area and was chosen as the control treatment. For the second step of the process, the time interval between the on-field pre-drying and threshing was considered: B1) 14 to 19h post-harvest; B2) 20 to 24h post-harvest, and B3) 25 to 29h post-harvest. Afterward, methods A1 to A3 were combined with methods B1 to B3 and feed into an axial flow-thresher at 10 kg min-1, 550 rpm PTO, and two levels of moisture content at 19 and 26 percent (% w.b). The third process was two-stage or three-stage tempering for 10 or 15 hours resulting in four levels (C1 to C4) and was done in the conventional batch type dryer under temperatures of 40 and 50 ˚C and airspeeds of 0.5 and 0.8 m s-1 in paddy milling factories. At the end of each process, a 100g sample was oven-dried for 48h and a microscope achromatic objective 40x was used to detect incomplete horizontal or vertical cracks, tortoise pattern cracks, and immature and chalky grains. The equilibrium moisture content was determined to be 7.3 percent. Losses properties were analyzed using a completely randomized factorial design with a randomized block followed by Tukey's HSD test at the 5% probability and comparisons among the three replications were made.Results and DiscussionResults demonstrated that the stack and plastic drying methods significantly increased the percentage of losses. In the plastic drying method, the percentage of chalky grains and tortoise pattern cracks was higher than other forms of loss. In the first process, irrespective of the pre-drying method, the losses were reduced at a lower level of moisture content. At the end of the first stage, losses in the spreading method were significantly lower at 19% moisture content. Threshing the plastic-wrapped paddies after 14 to 19 hours at 19% moisture content resulted in the maximum threshing loss of 8.446% and over half of the grains were chalky or had tortoise pattern cracks. The threshing loss was halved (4.443%) for paddies threshed 25 to 29h after spreading at a moisture content of 26%. The mean of losses in the second step of the process were 7.229, 5.585, and 5.156% for the time interval between the on-field pre-drying and threshing of 14 to 19h, 20 to 24h, and 25 to 29h, respectively. In the last step of the process in paddy milling factory dryers, there was no significant difference in the minimum percent of losses between 10 and 15 hours of three-stage tempering at 40 °C and with 0.5 m s-1 airspeed. Furthermore, maximum total losses with the most incomplete horizontal and vertical cracks occurred in the two-stage 10h tempering at 50 °C and with 0.5 and 0.8 m s-1 airspeed.ConclusionFood security has always been a critical matter in developing countries. Furthermore, identifying the source of losses in the fields and the factories is one way to reduce losses and achieve food security. Stacking or wrapping the paddies in plastic after pre-drying on the fields for 5h is not recommended in terms of its effect on increasing the percentage of brown rice losses. Additionally, due to the importance of factory dryer scheduling in the management of the losses, it is recommended to use a three-stage 10h tempering at 40 °C and with 0.5 m s-1 airspeed.

Water management in cracked paddy soils is an important issue in rice cultivation. In order to investigate the effect of rice straw and zeolite and their interaction effect on the physical condition of soils of paddy fields and prevention of crack, rice straw factor at four levels (0, 0.5, 1 and 1.5 percent) zeolite factor at four levels (0, 8, 16 and 24 tons per hectare) and also moisture stages of soil which are wet and dry stages at 5 levels which have been studied in three replication as factorial based on the complete randomized block design in Rice Research Institute of Iran. Soil distance from the wall of the container, the width of cracks, a few days to reach the crack with a certain width, bulk density and surface cracks were measured. Results showed that adding high levels of residue to delay the occurrence of cracks. However, the addition of zeolite has no significant effect in delaying the cracks. The relationship between bulk density and surface cracks that follow the linear equation, With increasing cracks surface, bulk density is increased. Finally, Can be concluded that the addition of plant residues, causing disappearance of existing cracks and returned to the soil to be the initial state.

Subsurface drainage is a prerequisite to growing winter crops and improving water management in rice season in the consolidated paddy fields in Northern Iran. Based on different cultivation condition, to decrease nutrient loss from subsurface drainage in these fields, adopting suitable strategies will decrease the pollution of water resources. A research was conducted in pilot farm of Sari Agricultural Sciences and Natural Resources University from May 2015 to April 2016 (during two successive rice-canola growing seasons) to evaluate the effect of subsurface drainage systems on nitrate loss and nitrate concentration in different soil depths. The subsurface drainage treatments were three existing subsurface drainage systems with mineral envelopes, including systems with 30-m spacing and 0.9 m depth, a drainage system with 30-m spacing and 0.65 m depth, a drainage system with 15-m spacing and 0.65 m depth, and a bi-level subsurface drainage system with drain spacing of 15 m and drain depths of 0.65 and 0.9 m as alternate depths (bi-level). The nitrate concentration was monitored in drainage water and at depths of 0.4, 0.9, 2 and 5 m during the study period. The results showed that the nitrate concentration and the total nitrate loss during rice growing season was 33-80% and 91-99 %, respectively, less than that in canola growing season. Also, the nitrate concentration in drainage water for drains with 0.9 m depth was more than that in drains with 0.65 m depth. On the other hand, nitrate concentration in surface depth was higher than lower depths in all treatments. Overall, in both seasons, drainage system with wider spacing and shallower depth drained out less nitrate than the other systems.