Late Transplanting Research Articles

Analysis of the mechanism of low-yielding of rice caused by late-transplanting : (III) Yielding responses of seedlings grown at different densities in the nursery

1. In the previous experiment, it was shown that late transplanting results in remarkable decrease of yields. With the aim to analyze th mechanism of such a reduction of yield, the authors compared the growth and yield of rice plants under six different treatments. The seeds were sown at six different densities on nurseries similarly as described in the previous report (2), i. e. the amount of Seeds was 541 cc, 180 cc, 54 cc, 18 cc, 5.4 cc and 2.8 cc per 3.3 m2, asrd the seedlings were transplanted individually into six hills per 3.3 m2 (90;9×60.6 cm) in g paddy field giving the individual plant a sufficient space for uninterfered growth. 2. The crop from the plant soon densely in the nursery were smaller when transplanted late. On the contrary, the plant sown sparsely seemed to be able to produce higher yield, even by late transplanting. 3. The actual yields of crops given by the seedlings transplanted 30 days later than the standard time were as follows ; (i) Seedlings sown densely gave extremely, low yields. (ii) Seedlings sown 180cc per 3.3 m2 gave about an half of th yield by the standard culture. (iii) Sparsely sown plots gave nearly the same or even larger yields compared the standard culture. The reasons for these responses had been discussed in the previous report (1), by the same author. Table : The yielding responses of the rice seedlings grown at different density of stand in the nursery. Seedlings were all transplanted at 30 days later than usual (Variety, Ou-No. 195)

Analysisi fo the mechanism of low-yielding of rice caused by late transplanting : (2) Growth of interference of the plant in the nursery

1. When transplanting of rice seedlings is, delayed because of prolonged harvest of winter crops (such as barley, wheat, potato and rape, etc.), the seedlings are grown in the nursery for an improperly long period causing a shortage of space for individnal growth. Consequently the yield of the crop decreases remarkably owing to shortening of growing period after transplanting and besides to the mutual growth interference of the seedlings in the nursery. 2. The authors investigated. the growth (height of plants, increase of tillers and weight of plants) of rice seedlings under different experimental conditions ; i. e. the seeds were sown at each of five different densities (amount of seeds ; 541 cc, 180 cc, 54 cc, 18 cc, and 5.4 cc per 3.3 m2). Two varieties, Sekiyama a variety of heavy-panicle type and, , Ou-No. 195, a mediate-type were used. 3. The seedlings grown in sparsely sown plot produced tillers regularly and had mote than 18 tillers at the time of transplanting. Interference of growth occured late, because each seedlings had good enough space to grow. But the seedlings in densely sown plot suffered interference of growth at early stage of growth and had no tillers at the time of transplanting. 4. The numder of days after sowing to the time when tillering ceased is shown in the following table. The time of the initiation of the interference of mediate type was earlier than that, of heavy-panicle type. 5. When rice plants are to be transplanted lately than usual, it is necessary to take into consideration the relation between the sowing density and the initiation of the growth interference of plants in nursery.

Analysis of Mechanisms of the Decrease of Yields of Rice Plants Cultured under Late-Transplanting Conditions : (I) On the Yielding Efficiency of Seedlings Sowed Sparsely and Densely to Seed-Bed

In the previous experiment, it was shown that the late transplanting resulted in the remarkable decrease of yields.. with the aim to analyze the reduction of yield caused by the late transplanting, we have compared the growth and yield of rice crop under two different treatment; one sown densely (18 × 18cm) and other sown sparsely (24.2 × 24.2cm) on the seed bed, both transplanted later than usual. The seedlings in sparsely sown plot produced their tillers regularly; they have more than thirty tillers already at the time of transplanting, and howed high yield. But in the other plot the tillering is inhibited; no one tiller at the time of transplanting, and showed low yield, about half of that in the usual cultme. After the seedling were transplanted, the tillering has continued to some extent in former plot, but the many new tillers appeared at the higher nodes of the stem in letter plot. The high yield obtained in the sparsely sown plot may be explained by the following five reasons: (1) Seedlings were grown for longer time under favourable condition because the seed bed was more fertile than the paddy field and also it was rsurrounded by shelter-hedge. (2) As rice plants had good enough space to grow until the time of transplanting (5thof July) they could produce many healthy tillers from the lower nodes of their stem; 30 or more tillers were growing at the time of transplanting. (3) consequently the larger number of tillers and ears were produced. (4) As tillers from the lower part of the stem appeared early, the date of heading was also early, resulting heavy grain weight. (5) As far as the result of this experiment was concerned, the rice crop sown sparsely seemed to be able to produce higher yield, even when it transplanted later than usual culture method. But this trend might not be always observed because the different result would be obtained under different weather. The low yield of densely sown plot may be explained by the following fact; (1) tillering was inhibited seriously because of the narrow space given, and after they were transplanted. Appeared the tillers from the upper part of the stem as well as the tillers of higher order. (2) The number of tillers and stems were fewer than those of other plots.(3) As the tillering was delayed, date of heading was also delayed, and the light grains were produced.

Varietal Differences in Panicle Development of Rice with Reference to Early or Late Transplanting

In Japan late setting have hrretofore been occasionally used to the problem of crop rotation and irrigation facilities. The authors have carried on an investigation on the behavior of late setting in the diffrent varieties of rice. In the case when the duration of growth in seed-bed is the same, the period from time of the setting of rice seedlings to heading deer as a generally as transplanting becomes later. The number of days thus decreased varies. in different varieties, being less in early varieties than in intermediate or late varieties, as shown by our experiments (Fig. 1). We may consider that there are two different stages in the course of heading, namely, the period previous to the beginning of panicle differentiation, and the subsequent development of differentiating panicle towrds the heading, and these stages are affected by the influence of environmental factors respectively. In order to ascertain which stage will be seriously affected by late setting upon heading, the present experiments were carried out, and the results are summarized as follows: (1) The material used in this study consisted of 9 varieties with different growing periods under natural conditions. 30 days seedlings were transplanted in the paddy field on June 15th, 30th, and July 15th. In the cultivation of these varieties, the authors tried with utmost care to make all the cultivating conditions as nearly uniform as possible, so that quite uniform plants were sampled out from time to time for observation. As to the differentiation of panicle, a part of main stem inclusive of the growing point was fixed by Carnoy's fluid, cut in longitudinal section in 13μ thickness, and stained with Delafield's henmatoxylin. The differentiation of the first bract (Plate 1, (II) could be esily observed by determining the number of leaves on the main stem which were marked with enamel. The authors considered the stage in question as the beginning of panicle formation. (2) The stage of panicle differentiation may be divided into 12 principal phases as shown by the photomicrographs (Plate 1, (I)-(XII)). These 12 phases were used as basis for determining the grade of differentiation of panicles sampled at each date of observation (Table 1). After the growth of panicle were visible, their lengths were measured, and the results are shown in percentage in comparison to adult panicles (Table 2, Fig. 2, Plate 2). (3) The period previous to the beginning of panicle formation (=the number of days required from setting to differentiation of the first bract) was found to vary considerably according to different varieties and date of transplanting. This period was short for early varieties but long for late ones, and the later the transplanting, the shorter the period. The effect of late setting upon the number of days mentioned was less in early maturing varieties than in others (Table 3 Fig. 3). (4) The period subsequent to the beginning of panicle formation (=the number of days extending from differentiation of the first bract to heading) was seemed to be a little shorter in early varieties than in other ones. Notwithstanding the fact that the period in question was almost equal in early varieties both in early or late setting, it was observed to be somewhat shorter after late setting in intermediate and late varieties (Table 3, Fig 3). (5) As mentioned above, the effet of late transplanting upon the period (number of days) from setting to heading was found to be less intense in early varieties than in intermediate or late ones. This is chiefly due to the fact that the late transplanting exerts less intense influence on early varieties than on late ones concerning both perirods, viz. previous and subsequent to the beginning of panicle formation, and this effect exerts a decided influence in the formeer stage.

Deviation of Heading Time in Rice Plant Induced by Late Seeding and Transplanting(Preliminary)

Deviation of Heading Time in Rice Plant Induced by Late Seeding and Transplanting(Preliminary)