Rules Of Yield Evolution And The Characteristics Of High Yield In Different Types Of Japonica Rice

Field experiment was carried out at a farm in Yangzhou University from 2004 to 2005. The soil at the farm was sandy with preceding vegetation of wheat.104 Japonica rice cultivars prevailed in Jiangsu province were adopted as experimental materials. The experiment was conducted with a split plot design with four N rate (zero (0), low (10kg/666.7m2), medium (15kg/666.7m2), high (20kg/666.7m2) ) as main plot and cultivars as subplots in three replications. Growth duration and yield properties of Japonica rice were studied in order to clarify the yield evolution rules and the characteristics of high yield. And the results were showed as follows.1. With the increase of N level, the growth durations of all the cultivars were prolonged. Compared with the average growth duration of rice cultivars under zero N level, it was increased by 1.6 days under low N level, 3.8 days under medium N level and 6.4 days under high N level. Considering the growth duration structure, proper application of N could accelerate the heading of rice while over use of N could also delay the date of heading. With the increase of N level, days from heading to maturing increased gradually.2. The application of N has an effect on rice yield of different cultivars. And in our research, the average yield of all rice cultivars reached the maximal yield at the medium N level. Significant differences were existed among the average yield at the N level of zero, low and medium while there was no significant difference between the average yield of rice cultivars under the N level of medium and those under the N level of high. And the effect of yield increase decreased with the N application increasing. With the increase of N application, rice yield of several rice types including early-maturing medium Japonica (EMMJ), medium-maturing medium Japonica (MMMJ), late-maturing late Japonica (LMLJ), early-maturing late Japonica (EMLJ) increased while the yield of medium-maturing medium Japonica (MMMJ) rice type reach the highest under the N level of medium and then decreased under the N level of high. Among all rice types, the yield of EMMJ was the lowest and the yield of MMLJ was the highest.3. With increase of N level, the number of panicle per 666.7m2 increased obviously while the variation of different rice cultivars decreased. Meanwhile, the effect of N on the The effect of N-fertilizer application on the number of panicle per mu was gradually decreased with increasing of N level. Among the different growth period types, the order of the number of panicle per mu is medium-maturing medium Japonica≈medium-maturing late Japonica>early-maturing medium Japonica>late-maturing medium Japonica>early-maturing late Japonica. The grain number per ear of Japonica rice shows first increase and then decrease with increasing of N level. but after certain level, The grain number per ear would decreased. Among the different growth period types, the order of the grain number per ear is early-maturing late Japonica>late-maturing medium Japonica>medium-maturing late Japonica>medium-maturing medium Japonica>early-maturing late Japonica. The 1000-grain weights and seed setting rate were decreased with increasing of N level, the order of 1000-grain weights is medium-maturing late Japonica > early-maturing late Japonica > late-maturing medium Japonica>medium-maturing medium Japonica>early-maturing medium Japonica. the order of seed setting rate is late-maturing medium Japonica >early-maturing late Japonica>medium-maturing late Japonica>medium-maturing medium Japonica>early-maturing medium Japonica.4. The growth stage of Japonica rice types and yield present extremely positive correlation, the yield increases with the growth stage's extension, but it has differences with the growth stage's extension to them, the yield of early-maturing medium Japonica has relation to heading stage which was delayed; the yield of medium-maturing medium Japonica, late-maturing medium Japonica early-maturing late Japonica and medium-maturing late Japonica is determining from heading stage to maturing stage.5. The growth duration of Japonica rice types and dry matter accumulation present extremely positive correlation(r=0.7226**), and the order is medium-maturing late Japonica > early-maturing late Japonica > late-maturing medium Japonica >medium-maturing medium Japonica>early-maturing medium Japonica. Dry matter accumulation from seeding to heading increased with delaying of growth type, ratio of dry matter accumulation from seeding to heading to total dry matter accumulation decreased firstly and then increased, presented a tendency of medium-maturing late Japonica>early-maturing medium Japonica > medium-maturing medium Japonica > late-maturing medium Japonica > early-maturing late Japonica; dry matter accumulation from heading to maturing increased except early-maturing late Japonica, ratio of dry matter accumulation from heading to maturing increased firstly and then decreased, presented a tendency of late-maturing medium Japonica > early-maturing late Japonica > medium-maturing medium Japonica > medium-maturing late Japonica > early-maturing medium Japonica.6. N content in plant of Japonica rice types increased with the increase of N level. N content in plant significantly decreased with delaying of growth process. N uptake in plant of Japonica rice types increased with the increase of N level. N uptake in plant increased with delaying of growth process and all of them presented a tendency of jointing stage the number of panicle per 666.7m2 >1000-grain weights > seed setting rate.8. Comparing high yield varieties with non-high yield varieties, there was no significant difference in grain number per ear, 1000-grain weights and seed setting rate while the grain number per ear of high yield varieties was much higher than that of non-high yield varieties which increase by 24% averagely. The growth duration of high yield varieties was longer than that of non-high yield variety.Days from seeding to heading of high yield varieties were higher than that of non-high yield varieties in early-maturing medium Japonica. Days from heading to maturing of high yield varieties were longer than that of non-high yield varieties in medium-maturing medium Japonica, late-maturing medium Japonica, early-maturing late Japonica and medium-maturing late Japonica. Dry matter accumulation of high yield varieties were higher than that of non-high yield varieties in early-maturing medium Japonica , medium-maturing medium Japonica , late-maturing medium Japonica, early-maturing late Japonica and medium-maturing late Japonica. And it increased by 23.4%during the period from heading to maturing. Nitrogen use efficiency of high yield varieties were higher than that of non-high yield varieties which accounting for 6% higher averagely.