稻田施氮水平对两种水稻热值变化特征影响

The Quantitative Analysis of the Caloric Value Dynamics of Two Rice Varieties Under Different Nitrogen Application Levels

对两种水稻类型 (早稻、晚稻 )在不同氮素水平下植株的热值动态进行了分析。结果表明 ,水稻植株的热值不仅因品种、器官而存在着差异 ,而且随着水稻生长发育的进程不同也存在着差异。两种水稻的热值最低值出现在小花分化期 ,最大值出现在分蘖期或开花灌浆时期。不同氮素水平对水稻热值的影响规律为 ,随着氮素水平的增加 ,水稻各组织器官的热值也增加 ,同一器官下 ,高氮素水平下的水稻组织热值高于低氮下组织的热值 ,不同器官热值 (根、茎、叶、穗 )之间在相同及不同氮素水平下存在显著差异。通过分析表明 ,没有氮素投入下的两种水稻基础热值为 1 6 979J/g,早稻每增加 1 kg/hm2 N,可以提高植株热值 1 .72 J/g;晚稻每增加 1 kg/hm2 N,可以提高植株热值 1 .2 4 J/g,这说明 ,氮素使用对早稻的热值效应影响要大于晚稻。因此 ,在运用热值指标进行能量分析时 ,必须考虑氮素使用水平对热值的影响。

This paper presents an analysis of the quantitative caloric energy characteristics and the dynamic variation of two rice varieties under different N levels in paddy fields in Hangzhou, Zhejiang Province, China. Field experiments were conducted at the Experimental Farm of Zhejiang University, Hua-Jia-Chi Campus, Hangzhou (latitude 30.2° N, longitude 120° E), China at 43.2m above sea level. The experimental site had an area of 1085.5 m 2. The early crop rice, Jiayu 948, was sown on 1 st April, and transplanted on 2 nd May 1999 while the late crop rice, Jiayu 93390, was sown on 24 th June, and transplanted on 26 th July 1999. The experiment plot was 8m×4m with complete random design and 4 replications. The planting hill density was 20cm×15cm with 5～6 seedlings for each hill. Nitrogen treatments with Urea fertilizers were at five levels: 0 (T0), 80 (T1), 120 (T2), 160 (T3), 200(T4) kg/hm 2. The application was done 3 times during the growth duration, 55% of the total N was applied before transplanting of seedlings, 35% in the tillering stage and 15% in panicle initiation stage. Adequate ecological and agronomic measures (e.g. pest and disease management) were undertaken to ensure optimal plant growth conditions. Water supply to the fields was appropriately regulated. During the experiment, 10 hills of the plants were sampled at 10 and 7 days interval for vegetative and reproductive stages respectively. Each sample was separated into respective organs: root, stem, leaf, ear, grain and husk for measurement of each organs' dry matter weight and then ground into powder samples. Caloric values of the rice were measured by sampling 1～2g of organs' mixed dry matter and put them into the oven to dry for 2～3h, then the rice sample was placed into an Oxygen Bomber and pure oxygen (99.5%) with air pressure maintained at 30 kg/cm 2 was added. Using Caloric Measurer device GR-3500, which was produced by Changsa Instrument Cooperation Company, the caloric values of the organs were derived according to instructions in the instrument manual. The final value of each rice sample at different growth stages was determined by means of two parallel measurements of the values' difference not exceeding the 80 J/g as actual value. If the two parallel measurement values exceeded the standard difference, then a new sample was taken and tested again. Nitrogen contents of organs were determined using the Kjeldahl digestion method followed by colorimetric determination at an optical density of 490 nm. This was done in accordance with the procedure outlined by Yoshida %et al%. (1976). The results of caloric energy of rice were statistically analyzed using the random model aided by the data processing system (DPS) computer software (Tang & Feng, 1997). The results indicated that the difference in caloric values of rice existed not only between varieties and rice organs, but also during the different development stages of the two rice cultivars. The lowest caloric value was recorded at the panicle initiation stage of both varieties, the highest was at the maximum tillering for Jiayu 948, flowering or grain-filling stage for Jiayu 93390. Roots had the lowest values and the highest was in grain and ear organs of rice under different nitrogen regimes. There existed a significant difference of caloric values among the different organs (see table 5). The characteristics of N effects on the caloric values of the two rice crops showed that the caloric values increased with the increase of N application amount. Higher N levels produced higher caloric value as compared to lower N levels, but there were no significant differences in the same organs for the two varieties. The results indicated that the caloric value in the stems of early crop rice, Jiayu 948 under low nitrogen level had no significant difference with the root's caloric value under the higher nitrogen application. In the late crop rice, this trend was not evident as there were bigger differences between different organs under whatever N regimes were at higher or lower levels