Microclimate Characteristics In Colony Of Rice And Its Effect On Yield And Quality

The meteorological factors are important environmental factors which affect the yield and quality of rice. In addition, the microclimate condition in paddy field could directly affect the growth and development of rice. To investigate the microclimate features in paddy filed and explore their effects on yield and quality of rice, filed experiments were conducted. Different varieties include erect panicle, semi-erect panicle and curved panicle were used in the experiments. Temperature, relative humidity and dew point temperature at different heights (20cm overhead of canopy,2/3 plant height and 1/3 plant height) were measured using HOBO (HO8-007-02) data collector during the periods of heading, filling and mature, respectively. Illumination in paddy field was measured during the period of filling period. Moreover, the plant type and the components of rice yield were investigated during the period of development and growth. The yield and quality were measured after harvest. Based on the collected and measured data, the distribution differences of temperature, relative humidity and illumination among different rice varieties were analyzed. Additionally, the relations between the microclimate and the plant shape, composition and quality of yield were studied. The results showed that:1. When the solar elevation angle was smaller, the intensity of illumination of the upper part of the colony decreased fast, and that of the lower part decreased slower; when the solar elevation angle was larger, the decrease rates of the upper and lower part of the colony nearly had no differences. The intensity of illumination at 1/3 height of different colonies only had difference at noon. Before 10:00 and after 14:00, there was little difference. Most blending panicle varieties had lower transmittances than the other varieties. The transmittances of erect and semi-erect panicle variety nearly had no difference.2. The diurnal variations of temperature and humidity were similar in different fields, which were dominated by the air temperature and humidity. The differences of temperature and humidity among different rice canopies mainly occurred at sunny days. For the same rice canopy, the diurnal variation of temperature and relative humidity showed opposite tendency. The maximum of temperature and the minimum of relative humidity showed up at 13:00, earlier than the time of air temperature maximum.3. The pulsative changes of humidity of different variety colonies were greater than that of temperature. The pulsative change of dew point temperature was greater than that of humidity. The diurnal variation of dew point temperature was not as significant as that of temperature and relative humidity. The differences of temperature of different colonies were smaller than that of humidity. From the full heading stage to the mature stage, in clear days, the relative humidity and dew point in different variety colonies varied a lot, and the differences were extremely significant. The differences of temperatures were significant since the filling stage in middle August, and were extremely significant in middle September.4. The temperature of the lower part, at 1/3 plant height of the colony was lower than that of the upper active surface. The temperature difference could reach 4℃ or more. The temperature of the active surface was usually lower than that of the air above the canopy. But at noon of the clear days, they were nearly the same. Occasionally, the latter might be higher than the former. The humidity of the lower part (1/3 plant height) of the colony was higher than that of the upper part (2/3 plant height). At noon the relative humidity difference was about 20%. The humidity of the atmosphere was lower than that of the canopy. In the night, the temperature and humidity at different heights of the colonies were nearly the same, respectively, and the relative humidity all got to 100%. Temperature and humidity at different heights reached the same value during the time from 19:00 to 7:00 of the next day; there was some discrepancies when the rice grew to different stages.5. From August to mid-September, the rice was during the filling stage. The temperature of the conventional blending panicle rice colony was lower than that of the erect panicle and semi-erect panicle colonies. And there was little difference between the erect and semi-erect variety. In late September, the rice was nearly mature. Because the senescence processes of different varieties were different, the contrast situations of temperature and humidity of colonies had changed. However, hybrid rice was different from conventional rice, the temperature and humidity distribution of the colonies had no regulations compared to the other varieties.6. The relationship between the intensity of illumination and the characters of the plant is more closely. The effects of the spike neck, the leaf neck and the panicle length on the light intensity were greatest. The temperature and humidity of the group at the filling stage were significantly correlated with the plant height and the panicle traits. The relationship between flag leaf blade temperature and photosynthesis rate, or transpiration rate, could be simulated by parabola function. It indicated the temperature was suitable.7. The number of panicles was negatively related to the mean temperature and humidity during the periods of filling and mature. The number of panicle was positively correlated with the mean humidity. The illumination at 2/3 plant height and number of panicles showed significant negative correlation. Humidity was negatively related to grain-straw ratio and positively related to spike-formed rate. The intensity of illumination and yield had significant relationship. The intensity of illumination at noon had greater influence to the yield than that of the morning and evening; meanwhile, the intensity of illumination at 1/3 height had greater influence than that at 2/3 height. The mean transmittance of colony and the yield showed a parabola relationship. The typical correlation analysis of yield traits and microclimate showed that the microclimate had great effects on the panicle length, spike number. The microclimatic factors had a greater impact on the percentage of ripened grains. Temperature during the grain filling period, relative humidity at heading stage and illumination at 2/3 height had great effects on the yield traits.8. The temperature and humidity had obvious effects on milling quality of rice, especially the temperature at the filling stage. The intensity of illumination had great influence on most of the quality traits, especially on the milled rice rate, rice length and amylase content. Brown rice rate, chalk grain rate and protein content were positively related to transmittance. Milled rice rate, and amylase content were negatively related to transmittance.