Vergara - 1976 - Physiological and morphological adaptability of ri

60 CLIMATE nun RICE
To derive maximum benefit from each of the several varieties of a single crop
species by its introduction into a favorable environment. it is essential that the
crop varietal characteristics and its climatic needs and tolerance be carefully
considered for analysis of the climate in relation to various agricultural operations.
including plant protection measures which have to be critically timed.
Each of the objectives mentioned above, i.e. (a) sunteying an area for assessing
its agricultural possibilities, and (b) introduction ofnew varieties into new
areas. requires a different approach, although one may he dealing with the same
climatic parameters. The choice of criteria such
interval and duration of growing season. and the recognition of drought or
disease resistance of the crop at a particular stage. should thus be related to the
purpose for which the analjvsis is desired. If one merely wishes to know‘ whether
rice can he grotvn in a new area. simple analysis based on long-term mean rainfall
and temperature appears to be sufficient. It is well known that rice requires
about 1,000 mm or more rain during the growing season. and a mean air telnperature
of 20°C. In a preliminary analysis. delineation of areas using these two
criteria would give the anstver so far as climate is concemed. But introduction of
a new variety into new areas requires more specific knowledge about its behavior
with reference to climate. and this is not generally available.
CONCLUSION
It is evident that successful crop planning depends on the extent to which one can
establish quantitative relationships between climate and crop varietal characteristics.
But if the input data are qualitative. consisting of figures based on a
number of simplifying assumptions or smoothed-out averages. one can at most
hope to estimate the general behavior of crop growth under a given general
climate. This gives no explanation for the abnormal behavior of crop growth in
any season and for each variety. xvhich is frequently observed in areas with low
rainfall and high variability. Also. under these circumstances, events which have
practical significance under field conditions may not alu-‘ays be statistically
significant. This is particularly true of crop-weather relationships. since it is
difficult to assess accurately both the response of crops and their internal adjustments
to the different soil and climatic conditions. and the effect of cropmanagement
practices. Let us hope that the more precise information on cropenvironmental
reactions obtained by use of sophisticated equipment such as
phytotrons, when interpreted in the light of simultaneous field experience. will
go a long way toward proisiding the basic quantitative relationships required
for successful crop planning.