Vergara - 1976 - Physiological and morphological adaptability of ri

62 CLltvlATE AND RICE
DISCUSSION
CHANDLER (Chairman): This paper presents the problems of crop planning in climates with
variable and often insufiicient rainfall. A good account of the literature in this area of study is
included.
It seems to me that an analysis of rainfall data over an extended period (as shown in Tables 2
and 3 for the New Delhi area) is the best way of predicting the hazards involved/cit, to tum it
around—the probabilities for crop production success. This information, along with an understanding
of the nature of the varieties to be grown. should be obtained for the important ricegrowing
areas where monsoonal rains are erratic in quantity and timing.
One must agree with the authors comment that selecting continuous
atmospheric drought is logical. considering the high rates of evaporation and transpiration in
the tropics.
I believe that "water harvesting" as mentioned in this paper from the work of Swaminathan
et a1. 1969, is a field of study that needs much more attention. One is amazed at the amount of
w-ater that passes into the rivers and out to the ocean even in the regions suffering periodically
from a lack of water during the rainy season. By relatively" inexpensive construction works.
considerable quantities of this water can be impounded and used later when needed. I mentioned
this also in my comments on lttr. Alles‘ paper. but I tee] that the importance of such
operations cannot be overemphasized.
GHILDYAL: Our studies show that by using a second-degree multiple regression equation we
can predict rice yieid from the distribution of climatic parameters during the FICE-gffltvtng
season. I want to continent on it.
A second-degree multiple regression equation was employed for quantifying the relationship
between rice yield and climatic variables during the monsoon period of ‘North India (Pantnagar).
Above-average weekly total rainfall is beneficial during the nursery period and has an
adverse effect during the vegetative growth phase. which coincides with the peak monsoon
period. The ripening phase is most susceptible to excess rainfall. while for maximum daily temperature
it is the late vegetative to early‘ reproductive phase. The reproductive and ripening
phases are most susceptible to a change of i liC minimum daily temperature from the average.
By using the regression equation obtained for rainfall on rice yield. rice yield could be predicted
different for years.
HUKE: 1n Fig. l (time of onset and withdrawal of monsoon) June 1U is the date shown for
onset at Bombay. What is the range of variability in this and other dates‘? Does the variability
affect the cropping pattern‘?
SGSIPjJI These figures are based on data for more than 5O years and their variability is about
plus or minus l0 to l5 days. This does not change the general cropping pattern in the area but
greatly influences crop planning and agricultural operations in any particular season.
FISCHERI Why‘ not use soil-water budget models: basically sound, inherently more precise
(and actually so in comparative studies—see Lonas & Levin. Ag. Meteorol. in press). These are
not compuratioritillyi dgfjicult. and summarize a mass of tithcrwise confusing weather data. compared
with multiple regession or more traditional methods of summarizing.
Sasriy: The extent of applicability of soil-water balance models for agro-climatie classification
has been adequately discussed by Dr. Slatyer (1968) and Burgos (1968) referred to in my
paper. Secondly‘. where a number of crops and varieties are involved. we do not yet exactly
know the water availability patterns at different stages of crop growth in relation to the atmospheric
demand.
FISCHER; lfthe lack of soil data limits the use of soil-water budgets. then summaries based on
weather alone are equally limited. In other words, the exercise of trying to do the soil-outer
budget immediately forces you or someone to get the soil data if it is so important.
Snsiijt-‘r Thank you for the suggestion. I am not against the use of soil-water budget models
whenever they are applicable. provided measured rather than estimated values are used.
VELASCO: I appreciate that your paper is concerned with the relationship between rainfall
and yield over a broad area. Hotvever. I am interested in knowing what effect drought has
when it comes at various stages in the development of rice. Can you enlighten me on this.
please‘?
Sasrijv: In my paper I have attempted to describe a single station model for assessing atmospheric
stress at various stages of crop growth using rainfall data. However, for each crop variety