Formula for Determining Number of Basic Seedlings at Scattered-Planting with Seedling Dry-Raised on Plastic Trays in Double-Season Rice

The tiller emergence in seedling nursery beds and field, and panicle formation in the field were investigated under scattered-planting with seedling dry-raised on plastic trays in double-season rice. A significant difference was noted in the non-synchronously-emerged tillers （the tillers that formed from latent buds and did not emerge following the normal tillering law on seedling nursery beds and recovered to grow after scattered-planting or transplanting） as well as the percentage of the available synchronously-emerged tillers between seedlings raised on plastic trays under dry-land conditions （DPT） and seedlings raised on nursery beds under wetland conditions （WB）. The seedlings under DPT had some non-synchronously-emerged tillers, but those under WB had not. Therefore, the traditional formula for determining the number of rice seedlings was improved, and the formula for determining the number of basic seedlings under scattered planting with DPT in double-season rice was introduced. For early rice, it was X=Y/{（I＋t1r1）[1＋（N-n-SN）Rr2]＋（SN-3-t1）R2r5}, and for late rice, it was X=Y/{（1＋t1r1）[1＋（N-n-SN）Rr2]＋（N-n-SN-3）Rr2R1r3＋（SN-3-t1）R2r5}. Where, X represents reasonable number of basic seedlings per unit area at scattered-planting; Y, number of fitting panicles per unit area; t1, total number of tillers per plant; r1, percentage of the total available tillers; N, total number of leaves of the main culm; n, total number of elongated internodes in the main culm; SN, seedling leaf ages at scattered-planting; R, percentage of the primary tillers emerged in available node-position; r2, percentage of the available primary tillers; R1, percentage of the secondary tillers in the field （except the secondary tillers of the seedlings）; r3, percentage of the available secondary tillers; R2, percentage of the asynchronously-emerged tillers after scattered-planting; r5, percentage of the available non-synchronously-emerged tillers after scattered-planting.

Effects of test levels on creep and relaxation characteristic parameters of stem for rice seedlings grown in plastic cell tray

Creep and relaxation characteristics of stem for rice seedlings grown in plastic cell tray were studied by static tensile testing,in order to determine the relationship between characteristic parameters(rheological model parameters,stress components and strain components)and test levels(stress levels and strain levels).Rice seedling stem specimen used in the test was 40 mm in length.And the applied test values for the creep and relaxation test ranged from 1.0-3.0 MPa and 1.5%-3.5%,respectively,each for 5 levels.The results indicated that elastic modulus in the creep and relaxation model was not affected by test levels.However,except that viscosity coefficientηkv was a constant andηm1 decreased with the increase of test levels,other viscosity coefficient and rheological time nonlinearly increased as the test levels increased.And strain components in the creep model and stress components in the relaxation model significantly increased as the test levels increased.