Irrigation scheduling and water stress mitigation strategies in upland rice (Oryza sativa L.)

Abstract

The study entitled “Irrigation scheduling and water stress mitigation strategies in upland rice (Oryza sativa L.)” was carried out as two field experiments at the Instructional Farm, College of Agriculture, Vellayani from 2017 to 2020 to identify a suitable variety and irrigation method for upland rice, to standardize irrigation scheduling and to assess the effect of moisture stress mitigation strategies on the growth, yield and economics of upland rice. Experiment I entitled “Identification of suitable variety and standardization of irrigation method” was conducted from January 2019 to May 2019. The experiment was laid out in split plot design with five main plot treatments and two sub plot treatments, in four replications. The treatments included sprinkler irrigation at 100% PE, sprinkler irrigation at 75% PE, drip irrigation at 100% PE, drip irrigation at 75% PE and hose irrigation (farmer’s practice-irrigation given thrice in a week) as main plot treatments and rice varieties Uma and Prathyasa as sub-plot treatments. The height of the plant, number of tillers m -2 , leaf area index and dry matter production were observed to be significantly the highest for the variety Prathyasa irrigated using sprinkler irrigation at 100% PE and hose irrigation was significantly inferior to all other methods of irrigation. The variety Prathyasa irrigated using sprinkler irrigation at 100% PE also recorded the highest number of panicles m -2 (226.00), number of grains per panicle (159.75) and grain yield (4.37 Mg ha -1 ). The highest RLWC and consumptive use (434.25 mm) by the crop was observed in the variety Uma irrigated using sprinkler at 100% PE, followed by drip irrigated plots at 100% PE. The highest crop water use efficiency (1.53 kg m -3 ) was observed in the variety Prathyasa irrigated using hose method and the highest field water use efficiency (0.95 kg m -3 ) was observed in the variety Prathyasa irrigated using sprinkler at 100% PE. 282The economics of cultivation in terms of net returns ( ₹ 1,32,465.50 ha -1 ) and B:C ratio (2.67) were observed to be the highest in the variety Prathyasa irrigated using sprinkler irrigation plots at 100% PE, followed by the variety Prathyasa irrigated using drip irrigation at 100% PE. Field experiment II entitled “Standardization of irrigation scheduling and moisture stress mitigation strategies for upland rice” was conducted during January 2020 to April 2020. The experiment was laid out in split plot design with four main plot treatments and five sub plot treatments in five replications (the best treatment from the experiment I - sprinkler method of irrigation at 100% PE and the variety Prathyasa were used for the experiment II). The main plot treatments included approaches of scheduling irrigation: IW/CPE of 0.8, critical growth stage approach, irrigation to maintain soil moisture at 100% FC and irrigation to maintain soil moisture at 75% FC. The sub-plot treatments included field application of hydrogel polymer (20 kg ha -1 ), seed treatment with hydrogel polymer (10 g kg -1 ), hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @10g kg -1 ), foliar application of PPFM (1%) and absolute control. The plant height, number of tillers m -2 , leaf area index and dry matter production were observed to be significantly higher in the plots irrigated at 100% FC, treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @10 g kg -1 ), which was followed by the plots irrigated to maintain 2 cm depth of water at critical stages of crop growth. The number of days for 50% flowering, the number of panicles m -2 (233.20), length of panicle (20.36 cm), weight of panicle (3.07 g), number of grains panicle -1 (169.20), grain yield (5.00 Mg ha -1 ) and straw yield (8.07 Mg ha -1 ) were the highest in the plots irrigated at 100% FC and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @10g kg -1 . . The consumptive use by the crop was significantly the highest in the plots irrigated at 100% FC (1265.60 mm) and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 ).The crop water use efficiency recorded the highest value (0.69 kg m -3 ) in the plots irrigated at IW/CPE 283of 0.8 and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 ) and a significantly higher field water use efficiency (0.58) was recorded in the plots irrigated at IW/CPE of 0.8 and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 ) The highest B: C ratio (2.92) and net returns ( ₹ 1,58,000.00 ha -1 ) were obtained from the plots irrigated at 100% FC and treated with hydrogel polymer (field application @ 2.5 kg ha -1 + seed treatment @ 10g kg -1 . The results of the study revealed suitability of the variety Prathyasa, irrigated using sprinkler irrigation at 100% PE for higher yield and monetary returns under upland conditions. It also reflected the suitability of irrigating upland rice at 100 % FC as an effective approach of scheduling irrigation, along with the application of hydrogel polymer (field application @ 2.5kg ha -1 + seed treatment @ 10 g kg -1 ) as the most suitable moisture stress mitigation strategy for upland rice cultivation for enhanced yield and economic returns under water stress conditions.