EFFECT OF SOWING TIMES AND IRRIGATION REGIMES ON PHOTOSYNTHETIC RATE AND CO 2 CONCENTRATION AND YIELD OF SUMMER PEARL MILLET IN WESTERN MAHARASHTRA

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1 EFFECT OF SOWING TIMES AND IRRIGATION REGIMES ON PHOTOSYNTHETIC RATE AND CO 2 CONCENTRATION AND YIELD OF SUMMER PEARL MILLET IN WESTERN MAHARASHTRA Pawar, P. B., Bodake, P. S., Jadhav, J. D., Surve, U. S. and Shinde, V.A. Zonal Agricultural Research Station, Solapur, Maharashtra Received: 22/11/2017 Edited: 28/11/2017 Accepted: 06/12/2017 Abstract: One field experiment was conducted for two years (2010 and 2011) at Water Management Farm, Mahatma Phule Krishi Vidyapeeth, Rahuri to optimize crop, photosynthetic rate and CO 2 concentration of summer pearl millet (PennisetumglaucumL.), under different sowing times and irrigation regimes. There were 12 treatment combinations for experiment having four sowing times, viz., D 1-6 th MW (5-11 February), D 2-8 th MW (19-25 February), D 3-10 th MW (5-11 March) and D 4-12 th MW (19-25 March) and three irrigation regimes, viz., I mm CPE, I mm CPE and I mm CPE. A strip plot design was employed with three replications. In western Maharashtra summer pearl millet is a widely adopted crop because of its drought resisting nature and irrigation is required to obtain a higher crop. In this, experiment conducted in 2010 and 2011, we studied the effects of sowing times and irrigation regimes.climatic data were obtained from Water Management Project Farm meteorological substation. The results showed that sowing of summer pearl millet in 8 th MW (19-25 th Feb) generally produced higher values for photosynthetic rate, CO 2 concentration and final grain than those of late sowings (10 th MW and 12 th MW) while As drought progressed, the net photosynthetic rate was significantly inhibited in the late sown summer pearl millet as compared with early sown crop. However, significant differences were noted regarding these parameters due to irrigation regimes as irrigating summer pearl millet with 100 mm CPE irrigation gives higher photosynthetic rate, CO 2 concentration and final grain as compared to 150 mm CPE irrigation regime. Late sown summer pearl millet may subject to heat stress, and hence poor grain s are obtained. This study concludes that summer pearl millet should be irrigated in earlier stages to achieve reasonable grain and monetary benefits. Key Words: sowing times, irrigation regimes, photosynthetic rate, CO 2 concentration and. Introduction Pearl millet is a major cereal crop in northwestern and western India. The crop is grown in very harsh, arid, dry climatic areas having high temperature and low and erratic rainfall. In the last decade, pearl millet was also grown under irrigation in the summer months. With the adoption of improved cultivars and low-cost improved technology, s can be increased by 20-30% from the existing levels. Pearl millet is a potentially productive, high-quality grain or silage crop that appears superior to sorghum concerning establishment and production under limited soil moisture (Serraj and Sinclair, 2002; Purcell et al., 2002; Dakheel et al., 2009).There is a need to explore opportunities to expand the area under summer pearl millet particularly in areas where irrigation is available and the fields are vacant during the summer season. The ability of the crop to grow in dry environments is due to a number of physiological and morphological characteristics like rapid and deep root penetration (root depths of 3.6 m have been recorded), fast growth and development and high tillering capacity. The area under summer pearl millet is still low when compared to kharif pearl millet but it is expanding in Rajasthan, Gujarat and Maharashtra state. In India, area under pearl millet is 8.68 Mha with production of 8.61 MT and productivity of 991 kg ha -1. The area under pearl millet in Maharashtra is Mha with the production of 1.06 MT having productivity of 729 kg ha -1, (Anonymous, 2010). UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor:

2 A plant with adequate soil moisture transpires water profusely, keeping its leaves cooler than the surrounding air. When soil moisture is insufficient, plant is experiencing moisture stress, the leaves transpire less and become warmer. The plant leaves must remain turgid for leaf expansion, to keep stomata open for higher photosynthetic rate. In plant, leaves functions as an optical organs and spectral radiation properties are attuned to environment in which they live. The amount of distribution of incoming radiation sets the limits for dry matter production. The efficiency of absorption of PAR partly determines the efficiency of photosynthesis of plant. The PAR is absorbed more efficiently and centering around nm, determines the plant development. Due to climate change of kharif crop is adversely affected that s why area under summer pearl millet is increasing. The meteorological study on this aspect is very meager for kharif as well as summer pearl millet. The objective of this study is to investigate the effect of different sowing times and irrigation regimes in western Maharashtra region on growth, development, meteorological, physiological parameters and of summer pearl millet. Evapotranspiration from vegetative surface is influenced by many meteorological factors like temperature, radiation, humidity and physiological factor such as photosynthetic rate, leaf water potential and stomatal conductance of the plant with this back ground in view, the present investigation was undertaken to know the photosynthesis rate and CO 2 concentration as influenced by sowing times and irrigation regimes in summer pearl millet. Experimental Methodology Two planting cycles were investigated under the current study. The first planting cycle was conducted during the period from February 2010 and 2011 to the end of June, 2010 and 2011, respectively as a normal practice in the western part of Maharashtra, since it considers a relatively high heat unit requirement crop. The field experiment was conducted on medium black sandy clay loam soil at Water Management Project Farm, Mahatma Phule Krishi Vidyapeeth, Rahuri located near Rahuri Tehsil, 35 Km away from Ahmednagar district of Maharashtra. The climate of the area is semi-arid, with high temperatures during summer season. The experiment was conducted in strip plot design with three replications. There were four sowing times viz., 6 th, 8 th, 10 th and 12 th MW and three irrigation regimes viz., 100 mm, 125 mm and 150 mm CPE under study. Recommended dose of NPK (80:40:40 kg/ha) was applied. The net plot size was 5.10 m x 3.60 m and planting distance was 45 cm x 15 cm. Due to the combine effect of sowing time and irrigation regime treatments the crops were mature at different days. IRGA instrument (LI-6400XT) was used for estimation different physiological parameters (photosynthetic rate, CO2 concentration, stomatal conductance and stomatal resistance) of the crop within the height of 2 meter. The physiological observations were recorded at 28 and at 14 days interval. Experimental findings and discussion The results obtained from present investigation are presented in Table 1, 2 and 3 Effect of sowing times and irrigation regimes onphotosynthetic rate The effects of investigated sowing times and irrigation regimes on photosynthetic rate is presented in Table 1. The photosynthetic rate was increased with advancement of crop age upto 56 and decline thereafter, during both the years of experimentation due to crop senescence. The photosynthetic rate was significantly the highest when crop was sown in 8 th MW and it was significantly the lowest when crop was sown delayed in 12 th MW at all the days of observations during both the years of experimentation owing to significant improvement in absorbed photosynthetically active radiation (APAR), light use efficiency (LUE), stomatal conductance, CO 2 concentration and leaf area and lower stomatal resistance under 8 th MW and significant decrease in these components when crop was delayed sown in 12 th MW. These findings are with Rajavelet al. (2010) who found maximum photosynthetic rate with early UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor:

3 sowing times.the photosynthetic rate was significantly more when crop was sown in 6 th MW than sowing of crop in 10 th MW at all the days of observations during both the years owing to favourable microclimate under former sowing time and adverse situation under later sowing time. The crop irrigated with 100 mm CPE significantly increased photosynthetic rate as compared to crop irrigated with 125 and 150 mm CPE irrigation because of favourable microclimateviz., absorbed photosynthetically active radiation (APAR), light use efficiency (LUE), stomatal conductance, CO 2 concentration, production of more leaf area, lower stomatal resistance and due to adequate moisture availability results in higher and consequently photosynthetic efficiency. These results corroborate the findings of Rajavelet al. (2010)who reported the higher photosynthetic efficiency with more moisture availability. It was noticed that crop irrigated with 125 mm CPE also significantly improved photosynthetic rate than crop irrigated with 150 mm CPE at all the days of observations duringboth the years of experimentation owing to favourable situation of microclimate, whereas, adverse microclimatic situation under 150 mm CPE due to stress condition decreased photosynthetic rate. The interaction effects between sowing times and irrigation regimes were non-significant at all the days of observations during both the years except on 28 and 84 during both the years (Table 3). Photosynthetic rate was significantly higher when crop was sown in sown in 8 th MW than other sowing times at all the irrigation regimes except early sowing in 6 th MW with 100 mm CPE on 28 and 84 during both the years (Table 10) owing to favourable microclimatic conditions and significant improvement in leaf area and leaf area index (LAI). Further, it was observed that, the photosynthetic rate was significantly the lowest when crop was sown delayed in 12 th MW followed by sowing in 10 th MW at all the irrigation regimes on 28 and 84 during both the years.the photosynthetic rate was significantly the highest under irrigation regime of 100 mm CPE and significantly the lowest under 150 mm CPE at all the sowing times on both the days of 28 and 84 during both the years owing to adequate moisture availability under former irrigation regime and stressed condition under later irrigation regime. Effect of sowing times and irrigation regimes onco 2 concentration The data (Table 3) indicated that the CO 2 concentration was significantly influenced by different sowing times and irrigation regimes. CO 2 concentration showed increasing trend upto 56 during first year except on 28 and upto 70 during second year, thereafter, it showed decreasing trend due to crop senescence. CO 2 concentration was significantly more when crop was sown in 8 th MW than other sowing times upto 56 during both the years owing to favourable microclimatic conditions and significant improvement in leaf area and leaf area index (LAI). It was significantly the lowest when crop was sown in 6 th MW on 28 and delayed sown crop in 12 th MW from 42 onwards which faces increasing temperature and decreasing relative humidity increased evaporation demand while increasing wind speed drastically reduce photosynthetic rate and CO 2 concentration of crop during both the years owing to stress conditions creating unfavourable microclimatic conditions for growth and development. The early sowing in 6 th and 8 th MW though found at par with each other but significantly accumulated more CO 2 concentration than crop sown in 10 th MW from 70 onwards during the first year of experimentation and at harvest during the second year of experimentation. The CO 2 concentration showed significantly decreasing trend with each delay in sowing times on 70 during the year The CO 2 concentration was significantly the highest in early sown crop in 6 th MW on 84 during the second year of experimentation. Similar findings were reported by Jarvis (1976) and Rajavelet al. (2010). The CO 2 concentration was significantly the highest when crop was irrigated with 100 mm CPE UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor:

4 and significantly the lowest when it was irrigated with 150 mm CPE at all the days of observations during both the years. This was attributed to adequate moisture availability under former irrigation regime which created favourable microclimatic conditions and significant improvement in leaf area and leaf area index whereas adverse conditions were noticed under later irrigation regime owing to moisture stress conditions. Increasing temperature and decreasing relative humidity increased evaporation demand while increasing wind speed drastically reduce photosynthetic rate and CO 2 concentration. All these parameter together reduced soil moisture and consequently increased soil water tension and sometimes happened in 150 mm CPE irrigation regime due to high surface evaporation. The highest water tension was found in 150 mm CPE irrigation regime. This is expected because it is the highest water stress treatment.jarvis (1976), Rosenberg (1981) and Rajavelet al. (2010) reported similar findings that favorable soil moisture conditions improves CO 2 concentration which ultimately increases photosynthetic rate of crop. The interaction effects between sowing times and irrigation regimes were non-significant at all the days of observations during both the years except on 28 during first year and 42 during both the years (Table 4).The CO 2 concentration was significantly more when crop was sown in 8 th MW than other sowing times at all the irrigation regimes on 28 during first year and 42 during both the years. Further, it was noticed that CO 2 concentration was significantly increased under early sown crop in 6 th MW as compared to delayed sown crop in 10 th and 12 th MW at all the irrigation regimes on 42 during both the years except 10 th MW under irrigation regime of 150 mm CPE. The CO 2 concentration was significantly the highest under irrigation regime of 100 mm CPE and significantly the lowest under 150 mm CPE at all the sowing times on 28 during first year and 42 during both the years owing to adequate moisture availability under former irrigation regime and stressed condition under later irrigation regime. The day-length in May is longer than that in February. Extended day-length resulted in great increase in vegetative dry weight. Increasing photosynthetic rate and CO 2 concentration in the first planting cycle might be due to the day-length. Planting millet in March increase photosynthetic rate and CO 2 concentration because temperature and daylength reach appropriate levels but crop duration is reduced which results in less biomass production. The metrological data collected from weathering station of the experimental site presented in Table 4 supported the results of this study. These metrological data showed large differences between the two growing cycles in minimum and maximum temperature as well as sun shining hours. Early in the plant growth, the rate of development of green leaf area plant -1 was the samefor the day-length, but the rate of leave appearance decreased by increasing daylength. This implied an increase in leaf size with extended day-length. Extended day-length resulted in increased leaf areas plant -1 and increase final leave numbers, consequentially, fresh and dry increased (Carberry and Campbell, 2006). Conclusions The findings of this study are very important for decision makers and growers of arid and semiarid regions. Early sowing time of 8 th MW and adequate moisture supply of 100 mm CPE irrigation regime gave the highest photosynthetic rate and CO 2 utilization, and monetary benefits followed by 6 th MW and 125 mm CPE irrigation regime compared to other treatments. The sowing of summer pearl millet 8 th MW (19 th -25 th February) and irrigated with 100 mm CPE irrigation regime with an average irrigation interval of 12 days was found more remunerative for higher crop productivity and monetary returns. UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor:

5 References Anonymous Agriculture statistics at a glance, 2010, Directorate of Economics and Statistics Ministry of Agriculture, Govt. of India. (Website : http// Carberry, P.S. and Campbell, L.C The growth and development of pearl millet as affected by photoperiod. Department of Agronomy and Horticultural science. University of Sydney. N.S.W. Org.au/au/asa/1985/concurrent crop production /p-18htm?print=1. Dakheel AJ, Shabbir G, Al-Gailani AQ (2009). Yield stability of pearl millet genotypes under irrigation with different salinity levels. Europ. J. Sci. Res., 37: Jarvis, P.G The interpretation of the variations in leaf water potential and stomatal conductance found in canopies in the field. Phil. Trans. Roy. Soc. Lond. B. 273, Purcell LC, Keisling TC, Sneller CH (2002). Soybean and water extraction in response to deep tillage and high soil aluminum. Commun. Soil Sci. Plant Anal., 33: Rajavel, M., Samui, R.P., Rathore, L.S., Balasubramanian, R., Ghosh, K. and Chattopadhyay, N Effect of diurnal variation of atmospheric and elevated levels of carbon-dioxide and photosynthetically active radiation on intercellular concentration and rate of photosynthesis in maize and safflower. J. of Agromet., 12 (1): Rosenberg N. J The increasing CO 2 concentration in the atmosphere and its implication on agricultural productivity. Climatic Change, 3 (3) : Serraj R, Sinclair TR (2002). Osmolyte accumulation: Can it really help increase crop under drought conditions?. Plant Cell Environ., 25: Table 1: Photosynthetic rate as influenced periodically by different treatments Treatments Photosynthetic rate (µ mole co 2 m -2 s -1 ) At harvest At harvest Sowing times 6 th MW th MW th MW th MW SEm± CD at 5% mm CPE mm CPE mm CPE SEm± CD at 5% Interaction SEm± CD at 5% 2.05 NS NS NS 2.05 NS 1.90 NS NS NS 1.94 NS General mean UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor:

6 Table 2: Interaction effect of sowing times and irrigation regimes on photosynthetic rate at 28 and 84 Photosynthetic rate (µ mole co 2 m -2 s -1 ) 2010 Photosynthetic rate (µ mole co 2 m -2 s -1 ) Sowing times (CPE) (CPE) (CPE) (CPE) th MW th MW th MW th MW SEm± CD at 5% Table 3: CO 2 concentration as influenced periodically by different treatments Treatments Table 4: Interaction effect of sowing times and irrigation regimes on CO 2 concentration at 28 and 42 in 2010 and 42 in 2011 Sowing times CO 2 concentration (µ mole CO 2 m -2 s -1 ) 2010 CO 2 concentration (µ mole CO 2 m -2 s -1 ) (CPE) (CPE) (CPE) th MW th MW th MW th MW SEm± CD at 5% CO 2 concentration (µ mole CO 2 m -2 s -1 ) At harvest At harvest Sowing times 6 th MW th MW th MW th MW SEm± CD at 5% mm CPE 125 mm CPE mm CPE SEm± CD at 5% Interaction SEm± CD at 5% NS NS NS NS NS 1.36 NS NS NS NS General mean UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor:

7 Table 5: Metrological data recorded from Water Management Project Farm, MPKV, Rahuri weathering station during the time of experiment Planting cycle Month Max. Temp ( C) The first growing cycle Min. Temp ( C) RH I RH II Wind Speed (kmph) Rainfal l (mm) BSS (hr) Evaporati on (mm) February March April May June The second growing cycle February March April May June Table 6: Grain, stover and biological s and harvest index as influenced by different treatments Treatments Grain Stover Biological Grain Stover Harvest index Biological Harvest index Sowing times 6 th MW th MW th MW th MW SEm± CD at 5% mm CPE mm CPE mm CPE SEm± CD at 5% Interaction SEm± CD at 5% NS NS NS NS NS NS NS NS General mean UGC Approved Journal (Sr. No Journal No ) / NAAS Score 2017: 3.23, GIFactor: