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Results and
Discussion
During 1982-83 the specified values of morning LWP (SD) at
irrigation (Table
2) approached in
T2, T3 and T4 (Fig.1a)
near CRI and therefore received one irrigation alongwith T1.
Following criteria, no irrigation was warned at LT and LJ stages.
After CRI stage, the irrigation initiation value of LWP was observed
near flowering and milkstages in T2 and near flowering in T3. During
this period LWP in T4 (irrigated at CRI) was similar to those in T5
and T6. On 96th day after sowing (10 days after F stage), T4 was
irrigated accidently when LWP was -9.0 bar. Similarly at milk stage
T5 received irrigation alongwith T1 although it did not show the
specified value of LWP. Grain yields (Table
3) were
significantly higher in T3 receiving two irrigations near CRI and
flowering stages. Thus, T3 performed best in terms of yield and water
use efficiency. Yield reduction in T1 and T2 were due to severe
lodging following the irrigation near milk stage. In fact high speed
winds prevailed after this irrigation during this year and coused
severe lodging in light textured soils.
As per 1983-84 schedule, T3 (SD1 = 6 bar) approached the
specified values of morning LWP on 27 and 93 days after sowing and
therefore received two irrigations near CRI and F stages
(Fig.1b).
T1 and T2 were irrigated at their respective growth stages. Grain
yield in T3 (Table
3) found
statistically at par to those in T1 and T2. Results reveal that more
than two irrigations (near CRI and F stages) did not show any
beneficial effect on grain yield. Thus the results of 1983-84 confirm
the irrigation schedule (SD1= 6bar) found optimum in
1982-83.
Above results reveal that for deciding SD at irrigation time
SD1 should be 6 bar for wheat crop grown in soil with
water table similar to Haldi series if morning LWP is the indicator
of stress day factor. It may be concluded that stress day index
concept using morning leaf water potential can be used to warn the
irrigation timings in wheat.
References
Cary JW and Wright JL (1971) Responses of plant water potential
to the irrigated environment of Southern Idaho. Agron J 63:
691-695.
Clark RN and Hiler EA (1973) Plant measurements as indicators of crop
water deficit. Crop Sci 13: 466-469.
Hiler EA and Clark RN (1971) Stress day index to characterize effects
of water stress on crop yields. Trans ASAE 14: 757-761.
Hiler EA, Howell TA, Lewis RB and Boos RP (1974) Irrigation timing by
the stress day index method. Trans ASAE 17: 393-398.
Kramer PJ (1969) Plant and soil water relationships. Mc-Grow-Hill
Book Co., New York.
Scholander PF, Hammel HT, Bradstreet ED and Hemmingsen EA (1965) Sap
pressure in vascular plants. Science 148: 339-346.
Teare ID, Kanemasu ET, Powers WL and Stone RL (1974) Physiological
indicators of water stress. Evaporation Laboratory, Kansas Agri
Experiment Statin, Manhattan. 24P.
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