جستجوی مقالات مرتبط با کلیدواژه « رطوبت نسبی » در نشریات گروه « منابع طبیعی »

In the recent years, agricultural products packaging was faced with some challenges. One of these challenges is measuring the oxygen and carbon dioxide amount during the respiration of stored products. Due to the high cost of the sensors and measuring devices of oxygen and carbon dioxide, the researchers have been looking for alternative methods for those measuring. The major aims of this study is to find a mathematical measurement method based on temperature, humidity ratio, and absolute and differential pressure during the respiration of lettuce storage. The present study was conducted at three temperature levels (5, 15, and 25 °C) and three storage time levels (24, 48 and 72 h). Based on the results of the mathematical model, the accuracy of prediction at the storage temperature of 5, 15, and 25°C for oxygen measurement were 96%, 98% and 97% and for carbon dioxide measurement were 95%, 99% and 98%, respectively. The statistical analysis of the variation parameters of carbon dioxide, humidity ratio and absolute and differential pressure with the variation of temperature and storage time of lettuce was significant at 1% levels.

In this study, the application of a solar system for heating a greenhouse of twin type with arched structure and single layer polyethylene coating was investigated. For this purpose, initially, the heating needs of the greenhouse were determined. Then, according to the obtained results, a flat-panel solar water heater with a collector of 6 square meters and a tank volume of 500 liters was selected and installed next to the greenhouse cucumber production unit to heat the air inside the greenhouse with 4 unit of 10-blade aluminum radiators. Then, using paired t-test, the results obtained in this greenhouse were compared with the conventional type in the area that had a diesel heater. The results showed that in terms of carbon dioxide, average temperature and relative humidity, there was no significant difference between the two greenhouses, but in terms of chlorophyll index and crop yield, there was a significant difference between the two greenhouses, at a probability level of 1 and 5 percent, respectively. Diesel had a higher average in these factors. Also, managing the four factors of minimum temperature, average temperature, chlorophyll content and maximum relative humidity in the greenhouse equipped with solar water heater and controlling the two factors of minimum temperature and chlorophyll content in the greenhouse equipped with diesel heater can improve photosynthesis and increase yield.

In order to evaluate germination characteristics and shelf life of alfalfa seeds stored in different storage conditions, a factorial experiment was conducted in a completely randomized design in a graduate laboratory of Urmia University of Agriculture. The experiments included relative humidity in six levels (50, 60, 70, 80 and 90 %) and control (room humidity) and storage duration (0, 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 months) with three replications. The studied traits included germination indices, seedling growth indices, and seed vigor and storage capability of seeds. The results showed that all germination indices were affected by relative humidity and storage duration. The interaction between moisture and storage duration was significant except for germination uniformity on all indices. The highest germination percentage was obtained in the control conditions (96.9 %), which reached 79.4 after 10 months of storage. Increasing the moisture content of the storage caused a significant decrease in the coefficient and uniformity of germination. The germination rate was the highest in the first month with the average of 0.071 per day, which had the lowest in 90 % relative humidity in the 10 months after storage to the average of 0.018 germs per day.