Rice Cultivation Period Research Articles

酒造原料米の醸造適性と気象条件の関係

Relationship between properties of rice (harvested in 1976-1987) and meteorological conditions during cultivation was studied by statistical analysis. The digestibilitiy and other properties of rice were affected by meteorological conditions in cultivation period of rice as follows. The digestibity of rice was decreased with increasing temperature in cultivation period of rice. And the properties of rice for sake making could be explained by meteorological conditions in cultivation period by using multiple regression analysis. These results suggested the posibility of predicting the properties of rice for sake making from meteorological data.

Estimation of production and respiration rates by the ciliated protozoa community in an experimental ricefield

Estimates of production and respiration rates by a field community of ciliates were made in an experimental ricefield located in the province of Reggio Emilia (Northern Italy) from June to September 13, 1983. Particular attention was given to ciliate communities inhabiting both the water column and the sediment. Production in the sediment was higher than in the water column during the first period of rice cultivation (June–July); in the second period (August–September) production was higher in the water column. A similar trend was recorded for respiration rates. During the entire period, production was estimated at 471 KJ m-2, while energy losses due to respiration accounted for 178 KJ m-2. The net production efficiency (K2) of the total ciliate community was 72.5%. Results obtained are discussed and compared with published data on ciliated Protozoa in other ecosystems.

Chamber Method for Measuring CO2 Flux from Soil Surface

To establish a method for measuring CO2 flux from soil surface, the relation between CO2 flux and the ventilation rate of a chamber was studied for the four different soils such as Andosol, Brown Lowland soil, Gray Lowland soil and Sand. The CO2 concentration in the air at the inlet and the outlet of the chamber was determined with an infrared gas analyzer (see Fig. 1). CO2 flux from soil surface was calculated from the CO2 difference between the inlet and outlet of the chamber and the air flow rate.1. It was found that the CO2 flux for the soils increases gradually with increasing the ventilation rate, approximating to respective constant levels at the higher ventilation rate. The critical ventilation rates at which the respective CO2 flux are assumed to approach to constant levels were about 13 times/hr for the Andosol and about 9-13 times/hr for the other tested soils.2. One dimensional CO2 balance equations for soil layer and a chamber were solved to derive the relationship between CO2 flux and the ventilation rate, and to obtain CO2 profile in the soil layer. The derived relationship indicates that CO2 flux is affected with effective CO2 gas diffusivity in a soil layer and ventilation rate (see Fig. 4). The theoretical results agreed well with the experimental results presented in Figs. 2 and 3.3. The experimental results obtained using the CO2 chamber system and Eqs. (5) and (6) were used to calculate the average effective CO2 gas diffusivity over the soil layer with 15cm depth and the CO2 concentration at the bottom of soil layer and results obtained are shown in Table 1. Under flooded conditions, the effective CO2 gas diffusivity for the tested soils was over a range from 0.035 to 0.042cm2s-1. These values were lower than molecular diffusivity of CO2 in the air.4. The chamber method was applied to measurements of the CO2 flux at the soil surface of three rice plant fields. CO2 flux measurement was made together with measurements of microclimatic elements during the period of rice cultivation in 1984 and 1985. The results are shown in Fig. 5. The daily CO2 flux was higher for a rice field with the application of organic manure than without that. It was found that CO2 flux at the rice field decreases gradually with lowering of soil temperature.

Oligotrophic bacteria on organic debris and plant roots in a paddy field soil

The distribution of heterotrophic bacteria on organic debris and roots of rice plants in a paddy field were studied. The heterotrophic bacteria consisted of two main groups: those which grew on full-strength nutrient broth (NB) and those which did not grow on NB but on a 100-fold dilution of NB (DNB). The latter group was called ‘DNB organisms’ and were considered to be oligotrophic. In both manured and unmanured soils, DNB organisms were predominant in the bacterial communities on organic debris and the rice roots throughout most of the entire period of rice cultivation, although a transient decrease in the proportion of DNB organisms was observed immediately after an application of manure. Morphological and physiological characteristics of DNB isolates from organic debris and rice roots were studied: five types of cell shape were observed, (1) regular rods, (2) filament-forming rods, (3) irregular rods, (4) prosthecate organisms and (5) large oval cells. Regular rods (42% of the total DNB isolates) and irregular rods (46%) were abundant. The ecological roles of DNB organisms in paddy soil are discussed in relation to their physiological characteristics.

A New Method for Estimating the Safe Heading Period of Rice Plant in the Cooler Region

In the Tohoku district, the cooler region in Japan, the cultivatable period of rice plants is shorter, and moreover, the extremely cool weathers have often occured during the important growth periods. Therefore, these periods are necessary to fit climatically in safe time. Such agro-climatological studies for estimating the rice cultivation period have recently developed in Japan and the methods which set the heading to a center of the plan have been established. In earlier studies the earliest and the latest dates of the safe cultivation period were established on the basis of seasonal variation curve of air temperature or of accumulated air temperature usually by the critical temperature free from cool damage, but they have not discussed the products from the quantitative point of view. Therefore, it was difficult to estimate physiologically of economically the most suitable cultivation period considering the management of a farm. For the purpose of settling this difficulties, it is necessary to elucidate the relationships between the changes of climatic conditions and of yield, corresponding to the movement of the important growth periods.The Authors have found the method for estimating the course of yield index corresponding to the heading by the application of such assumptive decreasing scales of rice yield based on low air temperature at the important periods as Fig. 1. These scales were proposed by Abe et al. (1964) in connection with the study (1960-1961) for estimating the damage by cool weather conditions on rice production.If the decreasing rates of yields by low temperature at three important periods of rice plants such as the reduction division period, the heading and ripening periods in case of heading on the date i in the year j, are designated by (R1)ij, (R2)ij and (R3)ij respectively, the yield index Yij will be as follows.Yij=100(1-(R1)ij)(1-(R2)ij)(1-(R3)ij)(1)The mean yield index for n years on a specific date i, Yi will be writtenYi=∑nj=1Yij/n (2)From Eqs. (1) and (2), yield index in case of heading on a spontaneous date can be calculated and consequently, the course of yield indexes is drawn in Fig. 2. For instance, the yield indexes and their course calculated from daily air temperature from 1937 to 1963 at the Fujisaka Farm are shown in Fig. 2 and Table 1.Taking the scale of a farm and working efficiency into consideration, if Yp is the planned level of yield index per unit area, the heading period obtaining products more than Yp is the term between Hc and Hl, the crossings of the curve of yield index to Yp-line, as shown in Fig. 3. But the heading time is apt to delay by the low temperature before them. Therefore, when the number of days of probable lateness, Ll is calculated by the other method, the date Hp, Ll days before Hl is obtained as the planning latest heading date, and the period from Hc to Hp, Lp is obtained as the planning safe heading period.