IRRIGATION MANAGEMENT IN DRIP IRRIGATED CASTOR (Ricinus communis L.)
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Date
2010
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ACHARYA N.G. RANGA AGRICULTURAL UNIVERSITY RAJENDRANAGAR, HYDERABAD
Abstract
A field experiment was conducted on a sandy clay soil at Water Technology Centre
Unit, College farm, College of Agriculture ,Rajendranagar, Hyderabad during rabi season,
2009–10 to investigate the “ Irrigation Management in Drip Irrigated Castor”.
The treatments consisted of seven irrigation treatments based on surface drip
method of irrigation and irrigation scheduling levels in the form of pan evaporation
replenishment. The evaporation replenishment factor viz., 0.4, 0.6 and 0.8 was either kept
constant throughout the crop life or was combinations of the above at vegetative, flowering
and capsule development stages. Besides seven drip irrigated treatments a surface check
basin system irrigated at an IW/CPE ratio of 0.8 with an irrigation water depth of 50 mm
was included. The experiment was laid out in a randomized block design with three
replications.
Higher castor bean yields were registered when irrigations were scheduled by drip
at 0.6Epan up to flowering and 0.8Epan later on (I6). However it was on par with 0.6Epan
throughout the crop life (I2) and 0.8Epan throughout the crop life (I3) and was significantly
superior over rest of the treatments. Similar trends were observed in growth and yield
attributing characters. Surface check basin irrigation at 0.8 IW/CPE ratio with an IW of 50
mm throughout the crop life was statistically inferior in comparison to drip irrigation
treatments except 0.4Epan throughout the crop life (I1). Drip irrigation treatments
recorded highest water productivity ranging from 0.777 to 1.137 kg m-3 (I1 to I7) in
comparison to conventional check basin irrigated crop (0.571 kg m-3). Maintaining higher
moisture regimes in drip irrigated treatments (I2, I3 and I6) had resulted in higher oil
content and oil yield over rest of the treatments. Lowest oil content and oil yield was
registered in conventionally irrigated surface irrigation treatment (I8).
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The seasonal ETc requirement of castor varied from 239.3 mm to 428.08 mm among
different drip irrigated treatments. It was highest in 0.8Epan throughout the crop life (I3)
followed by 0.6Epan up to flowering and 0.8Epan later on (I6) as compared to other
irrigation treatments. The seasonal ETc under surface check basin irrigated crop was the
highest and amounted to 445.87 mm. The average daily ETc rate varied from 1.58 mm to
2.87 mm under different treatments. It was highest in surface check basin irrigated crop
when compared to rest of the treatments.
The quadratic water production function indicated that the predicted maximum
castor bean yield (Ymax) of 3611 kg ha-1 was obtained at 383 mm of seasonal water (ETc)
requirement. The water production function did not emerge through the origin and the
value of regression constant (a) was negative, indicating that some minimum amount of
irrigation water i.e., crop ETc (182.5 mm) was required to be expended to realize the
economic yield (beans) in castor crop.
The economic analysis (farm income, NPV, net cash flow, BEP for price and water,
and payback period) suggested that the drip irrigation in castor was economically viable
even without a government subsidy.
It was concluded that castor grown in winter (rabi) season under Rajendranagar
conditions irrigated with drip system at 0.6Epan up to flowering and 0.8Epan at later
stages with an optimal seasonal water requirement of 383 mm gave maximum bean yield
(3611 kg ha-1) and was most remunerative under the prevailing prices of output and input.
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Keywords
IRRIGATION, MANAGEMENT, DRIP, IRRIGATED, CASTOR