Vergara - 1976 - Physiological and morphological adaptability of ri

4S0
CLIh-IATE AND RICE
in Japan for 5 years, 1967-197], using rice and several other species. as a part
of the internationally coordinated IBP/PP “Level I Experiment" which was
originally’ proposed by Professor GE. Blaekman, UK.
In the first experiment, on sowing date. seedling plants wiere grown in pots
successively’ from spring to autumn using a sand culture technique and uniform
supply of nutrients. After reaching a definite stage of growth (the S-leaf stage in
rice), the grovith rate of the plants for a week was determined and corresponding
observation of various climatic factors made to analyze their influence
on growth rate so that the variation of climatic conditions might be as wide as
possible. The experiment was repeated for 4 years at five stations lying from
43°35 to 3l°3'N.
The second experiment, on maximal growth rate. was designed to obtain the
highest possible net production with a reasonably high economic yield in the
field at each of se\ren locations lying from 39°4l' to 33°l2' N. Two varieties
were selected at each location and grown under optimum conditions of planting
density, amount and time of fertilizer application. water management, and control
of diseases, pests. and weeds. At 3-week intervals, determinations were
made on dry weight, leaf area, and various growth attributes including the components
of economic yield, to allow computation by the growth analysis method.
Various climatic factors were also observed during the whole growth period. The
experiment ‘was repeated for 5 years.
In this report. total dry weight productivity among different locations, as well
as economic yield is first compared using the data of the IBP field experiment.
The role of climatic factors as the cause for the locational differences is then
analyzed from the following three phases: (l) the development of photosynthetic
organs, i.e. leaves, (2) the efficiency‘ of photosynthetic function, and (3)
the processes of economic yield formation.
Since the two IBP experiments were conducted under natural conditions, it
is impossible in a strict sense to isolate the influence of any one climatic factor.
In the following discussions. therefore. the most probable climatic factors are
first inferred by the correlation method or otherwise; a search is then made for
experimental evidence supporting them. Finally‘, the degree of contribution of
the factors to the difference in growth responses is estimated by multiple rcgression
analysis or other appropriate tneans.
VALUES OF NET PRODUCTION.
MEAN CGR. AND GRAIN YIELD
Table l shows the 5-year average net production. mean crop growth rate (CGR),
and yield of brown rice in the IBP field experiment at seven different locations
in Japan. These values can be considered representative of the highest levels of
rice produetivit_y attainable under the individual environments,