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Evaluation of two micro irrigation systems for growth and yield in aerobic rice Article · August 2012

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Fifth International Groundwater Conference (IGWC-2012) on the Assessment and Management of Groundwater resources in hard rock systems with special reference to Basaltic terrain Editors: P.S.Kulkarni, C.Mayilswami, M.Thangarajan & V.P. Singh

Evaluation of two micro irrigation systems for growth and yield in aerobic rice T. Parthasarathi*, S. Mohandass*, S. Chellamuthu* and Eli Vered** *Ph.D. Scholar, Professor (Crop Physiology), Director (WTC), Water Technology Centre (WTC), Tamil Nadu Agricultural University, Coimbatore 641003, Tamil Nadu, India ** Irrigation, Senior R & D Agronomist for Field Crops, M/s , Netafim, D.N. Hefer 38845, Israel. Abstract The micro irrigation studies were conducted in aerobic rice during Dry Season (DS), 2011 in Coimbatore, Tamil Nadu, India. Micro irrigation treatments were three levels of lateral distance (0.6m, 0.8m or 1.0 m lateral distance) with the two discharge rates (0.6 or 1.0 lph emitters). Among the lateral distances, 0.8 m lateral distance registered as optimum spacing for its better performance in growth, physiological and yield attributes than rest of the lateral distances. Between two-discharge rates, 1.0 lph drippers out performed 0.6 lph drippers in terms of water productivity and grain yield. Interactively, laterals spaced at 0.8m with 1.0 lph drippers exhibited better performance in terms of growth parameters (such as plant height, tiller density, root biomass, total dry matter accumulation), physiological attributes (such as RWC, CSI, soluble protein, NRase activity, proline content), yield and its components (such as productive tillers, spikelet numbers, filled grain percentage, harvest index) along with water productivity. Therefore, it is suggested that the lateral spacing of 0.8m with 1.0 lph drippers when the plants spaced at 20x10 cm is adjudged as the best treatment for aerobic rice cultivation in enhancing the values for grain yield and water productivity in the areas of limited water availability. Key words: Aerobic rice, discharge rates, Lateral distance, lph (Litre per hour), Micro irrigation Introduction Increasing scarcity and rising cost of water threatens the sustainability of irrigated lowland rice. The wasteful and harmful system of flood irrigation practiced widely in South Asia must be replaced with furrow, drip or sub-irrigation systems (Aujla et al. 2007). It is expected that by 2025 AD, more than 17 million ha of Asia’s irrigated rice would experience “physical water scarcity” and about 22 million ha might experience “economic water scarcity” (Tuong and Bouman, 2003) and therefore, a newer method to combat water scarcity situation is warranted. Aerobic rice is an opt agricultural production system utilizing less water than conventional flooded rice. In the current scenario, drip irrigation offers a viable and alternate water-saving system for aerobic rice. Pressurized irrigation systems have potential to increase water productivity by providing water to match crop requirements, reducing runoff, deep drainage losses, generally keeping soil drier reducing soil evaporation and increasing the capacity to capture rainfall (Camp, 1998). Rice

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plants under aerobic systems undergo several cycles of wetting and drying conditions (Matsuo and Mochizuki, 2009). Such a mild plant water stress at vegetative growth stage decreased tiller number (Cruz et al., 1986). Lafitte and Courtois (2002) opined that Relative Water Content (RWC) of rice crop showed relatively higher values at vegetative stage stress under drip irrigation. Jha and Singh (1997) indicated that soluble protein content was more affected under water deficit condition. Kondo et al. (2003) found significant differences in rooting characteristics, especially deep rooting depth and root biomass, among various (aerobic and upland) rice varieties. There are only few attempts to address the physiological responses of rice and critical analysis of various yield components to aerobic conditions (Bouman et al., 2005). The application efficiency of different surface and pressurized irrigation methods varies and depends on design, management and operation (Holzapfel and Arumí, 2006). Karlberg et al. (2007) reported that two low-cost drip irrigation systems with different emitter discharge rates were used to irrigate tomatoes (Lycopersicon esculentum) and concluded that combination of drip systems with plastic mulch increased the yield. Xue et al. (2007) reported an average yield of aerobic rice was 4.1 t ha-1 with 688 mm of total water input in 2003 and 6.0 t ha-1 with 705 mm of water input. Ibragimov et al. (2007) compared drip and furrow irrigation and inferred that 18-42% of the irrigation water could be saved with drip systems with IWUE increased by 35103% compared to furrow irrigation in cotton. Considering the above, objectives of this study were set out to study the performance of aerobic rice, optimize the lateral distance and discharge rate for better grain yield, compare water requirements, water productivity, growth, physiological and yield responses in varied MicroIrrigation treatments consisting of three lateral spacings with two levels of emitter discharge rate. Materials and Methods The experiment was conducted during Dry Season (DS) of 2011 in the wetlands of Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India situated at 110 N latitude, 770 E longitude and at an altitude of 426.72 m above Mean Sea Level. Field experiment design of RBD (Randomized Block Design) was adopted with three replications using ADT(R) 45 as the test variety. The irrigation was given through PVC pipe (50 mm OD) after filtering through the screen filter by 7.5 HP motor from the bore well. The pressure maintained in the system was 1.2 Kg cm2 . From the sub-main, in-line laterals were laid at a spacing of 0.6, 0.8 or 1.0 m with 0.6 or 1.0 lph discharge rate emitters positioned at a distance of 30 cm. Irrigation was given based on the Open Pan Evaporation (PE) values (125% PE) from USWB Open Pan Evaporimeter (OPE) installed at Agromet Observatory in Tamil Nadu Agricultural University, Coimbatore, India. Treatment details There were eleven treatments employing three lateral spacings and two discharge rates of emitters. The treatments were: distance between laterals 0.6m with the spacing of 20 cm between rows of plants and spacing of 10 cm between plants (T1), distance between laterals 0.6m, spacing between rows of plants from lateral (20x10x10x20) (instead of three rows of 20 cm each) (T2), lateral distance of 0.8m, spacing of 20 cm between rows of plants and spacing of 10 cm between plants (T3), laterals distance of 0.8m, spacing between rows of plants from lateral (5x20x30x20x5) (instead of four rows of 20 cm each) (T4), lateral distance of 1.0m, spacing of 20 cm between rows of plants and spacing of 10 cm between plants (T5), laterals distance of 1.0m, spacing between rows of plants from lateral (7.5x15x15xempty bed (25cm)

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x15x15x7.5) (instead of five rows of 20 cm each) (T6), laterals distance of 0.8m, spacing of 20 cm between rows and spacing of 10 cm between plants + 30 percent more water (T7), lateral distance of 1.0m, spacing of 20 cm between rows of plants and spacing of 10 cm between plants + 30 percent more water (T8), lateral distance of 0.8m, spacing between rows of plants from lateral (5x20x30x20x5) (instead of four rows of 20 cm each) with 0.6 lph drippers (T9), lateral distance of 1.0m, spacing between rows of plants from lateral (7.5x15x15xempty bed (25cm) x15x15x7.5) (instead of five rows of 20 cm each) with 0.6 lph drippers (T10) and conventional irrigation at IW/CPE ratio of 1.25 at 30 mm depth of irrigation (conventional irrigation) (T11). Figure 1. Weather data prevailed during cropping season (DS, 2011) in Coimbatore, India.

The weather parameters prevailed during cropping season were observed in Agromet Observatory in Tamil Nadu Agricultural University, Coimbatore, Tamil Nadu, India (Fig. 1). The average values for maximum temperature were 30.7 ºC, minimum temperature 22.7 ºC, sunshine hours of 5.7 hrs day-1. The total evaporation recorded was 628.3 mm with the total precipitation of 533.0 mm. The effective rainfall was taken into account while scheduling irrigation under drip and surface methods. The effective rainfall was calculated using water balance sheet method (Dastane, 1974). Measurements of growth parameters were observed at the harvest stage of the crop. Plant height of each plant was measured from the base of the shoot to the longest leaf and the values expressed in cm. Number of tillers in selected plants in each treatment was counted. Then, the average number of tillers was worked out and based on that tiller density per m2 was derived. The total dry matter accumulation was arrived by summing up the dry weights of leaf, culm, root, panicles and TDMA, root biomass values expressed as g m-2. The following physiological parameters were measured at flowering stage of the crop. Relative Water Content of the leaf was estimated by adopting the method of Weatherly (1950)

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and the values expressed in percentage; Chlorophyll Stability Index (CSI) by Murty and Majumdar (1962) and expressed in percentage; Soluble protein content by Lowry et al. (1951) and expressed as mg g-1 fresh weight; nitrate reductase (NRase) activity of leaves by Nicholas et al. (1976) and enzyme activity was expressed as µg of NO2 g-1 hr-1; proline content by Bates et al. (1973) and expressed as μmoles g-1 of fresh weight. The yield and its components were recorded at the time of harvest. The number of panicles, number of spikelets, filled grain percentage, 1000 grain weight (Test weight), Harvest Index (HI) were recorded based on the method of Yoshida et al. (1971). Harvesting of crop (grain) from each treatment and replication was made from the net plot. After thrashing the grains, weight of the grain was taken. Grain yield per hectare was calculated from the mean plot yield and expressed in kg ha-1 at 14 % moisture content. Water productivity was calculated as the weight of grains produced per unit of water input (irrigation and rainfall) as per the formula of Yang et al. (2005) and expressed as g grain kg-1 of water. The recorded data were subjected to statistical analysis in Randomized Block Design (RBD) using ANOVA Package (AGRES version 7.01) following the method of Gomez and Gomez (1984). Result and Discussion The effects of micro irrigation treatment on growth parameters showed that a significant relation among the treatments. Increased plant height was recorded in T3 (78.4 cm) treatment followed by T1 (77.5 cm), T2 (77.0 cm), T4 (76.8 cm) and least in T11 (60.5) (Table 1). The micro irrigation treatments on aerobic rice showed a moderate plant height response. The moderate plant height has diverting assimilates for growth with comparatively lesser share of assimilates available for shoot growth even under moisture limitation (Sangsu et al., 1999). The tiller density of the crop showed a significant difference in micro irrigation treatment. High tiller production was observed in T3 (443), followed by T1 (427), T2 (411) and very less tillers in T10 (358) (Table 1). The less tiller density in drip irrigated aerobic rice is due to mild plant water stress at vegetative growth stage reducing the tiller number. Present results followed the study of Cruz et al. (1986). The root biomass of T3 treatment showed significant difference among the micro irrigation treatments. Higher root biomass was noticed in T3 (209.17 g m-2), followed by T1 (199.03 g m-2), T2 (178.43 g m-2), T4 (173.55 g m-2) and very less root biomass recorded in T10 (124.45 g m-2) (Table 1). By comparing the T1, T3 and T5 treatments, increase in lateral distance caused reduction in water availability to the root zone of crop. Therefore, root biomass is reduced in aerobic culture primarily on account of fewer adventitious roots (Kato and Okami, 2010). The Total Dry Matter Accumulation (TDMA) of aerobic rice showed a significant difference with other treatments by the various micro irrigation treatments. Significantly superior dry matter was produced in treatment T3 (1926.3 g m-2) and least by T10 (1469.9 g m-2). Comparing the two discharge rates of micro irrigation the 1.0 lph discharge emitters recorded 31.0 % increase in TDMA over the 0.6 lph discharge emitter treatment. The TDMA could be beneficial to grain filling at later stage and finally improved the grain yield (Wen-Ge et al., 2008).

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Table 1. Effect of various micro irrigation treatments on growth parameters in aerobic rice, DS (2011)

Treatments

PH

TD

RB

TDMA

T1 - Lateral distance 0.6m, row spacing 20 cm and plant spacing 10 cm

77.5

427

199.0

1893.5

T2 - Lateral distance 0.6m, row spacing from lateral (20x10x10x20)

77.0

411

178.4

1798.2


78.4

443

209.2

1926.3

T4 - Lateral distance 0.8m, row spacing from lateral (5x20x30x20x5)

76.8

410

173.6

1743.5


72.1

399

158.0

1721.3

T6 - Lateral distance 1.0m, row spacing from lateral (7.5x15x15xemptybed(25cm)x15x15x7.5)

70.9

370

154.7

1659.5

T7 - Lateral distance 0.8m, row spacing 20 cm and plant spacing 10 cm + 30% more water

77.7

424

184.4

1831.8

T8 - Lateral distance 1.0m, row spacing 20 cm and plant spacing 10 cm + 30% more water

74.3

410

174.8

1762.5

T9 - Lateral distance 0.8m, row spacing from lateral (5x20x30x20x5) with 0.6 lph drippers

69.9

363

153.7

1577.2

T10-Lateral distance 1.0m, row spacing from lateral (7.5x15x15xemptybed(25cm)x15x15x7.5) with 0.6 lph drippers

69.4

358

124.5

1469.9

T11 - IW/CPE ratio of 1.25 at 30 mm depth of irrigation

60.5

360

173.9

1536.3

73.1

398

171.28

1720.0

1.62

13.6

7.181

48.63

Mean SEd CD (P