Abstract
In the study reported herein an attempt was made to analyse the relationship between spacing and grain yield of rice plant by measuring dry matter productivity. The experiment was carried out with rice variety "Shiranui" in 1968. Six plots of spacing, i. e. 2, 10, 30, 50, 100 and 300 hills per squre meter were provided. Nine samplings (including root) were made on successive growing period and the changes of LAI and CGR were studied. The results are summarized as foollows ; 1) The constancy of final yield of dry matter at high densities was not found out. It increased slightly at higher density. 2) The grain yield was nearly constant as 530-560 g per squre meter at four densities, ranging from 10 to 100 hills per squre meter. 3) CGR increased gradually with advancement of growth stage, and reached at the maximum, and decreased gradually. But the density was higher, the maximum stage of CGR was earlier. The maximum value of CGR obtained in the experiment was 22-23 g/m2/day at all densities except the thinned plot, i. e. 2 hills per squre meter. 4) The relative equations between LAI, NAR and CGR were given as follows ; [numerical formula] where a, b, and c are constant. 5) An attempt was made to explain the constitution of grain yield by means of the relationship between LAI at the heading stage and the grain numbers per unit area, and the dry matter increment after heading.
