Vergara - 1976 - Physiological and morphological adaptability of ri

cnor PLANNING AND RAisFaLi. 55
the distribution of low rainfall areas revealed that the Telangana area could be
demarcated broadly into the four regions shown in Fig. 2.
Soil and cropping conditions
Red and black soils predominate in this region. In red soils crops are affected by
low‘ moisture retention and in the black soil areas crops suffer more due to
compaction, resulting in poor growth and root penetration. The most ividely’
grown traditional crops are varieties of joii-"ar, maize. eastor. and red gram. some
ofwhich take as long as 200 to 240 days to mature.
In areas where supplemental irrigation is available, rice and tobacco are
cultivated. However. tanks and reservoirs get filled only by rains, and the fate of
the rice crop is eloeely linked to the rainfall pattern. Discussing “rater-harvesting
techniques. Sivaminathan el a1. (1969) have pointed out that if enough water
could be stored from rains occurring early in the season to provide one or two
irrigations during the drought period, a single. long-duration erop could be
replaced by two short-duration crops. The development of photo-insensitive,
sham-duration varieties of rice. eastor, jowar, and other crops has made double
cropping possible in these areas. As an example, the typical cropping pattern
suggested for Region II. with an average seasonal rainfall of 80-85 em and
random dry spells, is shoyvn in Table I.
SEQUENTIAL OCCURRENCE OF PIlENOh/UENA
AND THEIR ANALYSIS
Such demarcation of an area gives a broad indication of agricultural potentialities
of the different regions. Planning of agricultural operations. hOWCVCf.
requires an understanding of the rainfall characteristics at each rainfall station
in greater detail. Frequency distributions of daily; weekly, and monthly rainfall
of specified amounts, and evaluation of their probabilities of occurrence. are
prerequisites for adequately understanding the rainfall pattern 0f a particular
station (Slatyer. 1960).
Rainfall reliability in relation to crop growth
Many criteria have been suggested in the literature for the study of rainfall
reliability in relation to atmospheric and agricultural drought, and their effect
on crop growth and yticld. Blumcnstoek (1942) used the theory of probability to
Table 1. Crop rotations for Telengana. Region ll: Average
rainfall: 80-85-em (random dry spells).
SI No. First crop Second crop
1. Caslor-(Aruna) mixed with
horse gram
2. Groundnut Castor (Arunal
3 Groundnut Early red gram
4. Hybrid JowartCSl-l. 1) Soybean (in relay with Jowar]
5. Mung (H. B. 45] Baira (HB. 3)
(After Swaminathan et al, 1969)