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T. SWAMI CHAITANYA*, P. MUNIRATHNAM AND M. SRINIVASA REDDY
P.G Scholar, Department of Agronomy, Agricultural College, Mahanandi – 518 502, A.P., India.
Field experiment was conducted at Regional Agricultural Research Station, Nandyal during post rainy season (maghi), 2015-16 to study the response of white sorghum to irrigations and nitrogen levels. The results of the experiment revealed that higher values for growth parameters viz., plant height and number of green leaves per plant were recorded with two irrigations. However, as regards the dry matter production, at 30 DAS, there was no significant difference among irrigation levels but at 60 and 90 DAS significantly higher dry matter was produced with two irrigations than no irrigation. Higher number of grains per panicle, grain weight per panicle, grain and stover yield was recorded higher with two irrigations where as 1000 grain weight was non significant with irrigations. All growth and yield parameters, grain and stover yield was higher with the application of 180 kg N ha-1 and lower values were obtained with the application of 90 kg N ha-1.
Irrigations, Nitrogen levels, Sorghum
Sorghum (Sorghum bicolor (L.) Moench) is the world’s fifth major crop in terms of production and acreage. It is a staple food crop for millions of the poorest and most food insecure people in the semi-arid tropics of Africa, Asia and Central America. Sorghum is a highly reliable crop that grows well in hot and dry environments. It is “climate change-ready” crop and provides food security and income for millions of poor farmers. Rabi sorghum (post rainy season) has multifaced problems. Irrigation is one of the most important factor that play a important role in sorghum production. As the crop is raised mostly under rainfed condition with the help of stored moisture, the moisture deficiency, especially during later stages of crop growth poses a serious threat to the crop, consequently the yield levels of rabi sorghum are very low. In Kurnool district of Andhra Pradesh, sowings are generally taken up during post rainy season called maghi jowar (middle of September to middle of October). Two situations are prevailing in Kurnool district i.e., in some areas sorghum is completely grown under rainfed conditions whereas in canal ayacut areas, one or two irrigations are being given. Further, under KC canal, it would be very difficult to predict the availability of water for irrigation as the stage of irrigation is very important. Therefore, it is very important to find out how many irrigations can be provided under limited irrigated conditions under KC canal ayacut area for enhancing
productivity. Farmers generally go for blanket application of nitrogenous fertilizers without actually knowing the requirement of crop particularly if the crop is irrigated. Irrespective of the situation (whether rainfed or irrigated) farmers indiscriminately use nitrogenous fertilizers for sorghum. Further, newly developed varieties with high yield potential required additional doses of nitrogen fertilizers due to their fertilizer responsive nature. Hence, the present study was conducted to study the effect of irrigations and nitrogen levels on growth and yield of sorghum during post rainy (maghi) season.
Field experiment was conducted during post rainy season (maghi) 2015-16 at RARS, Nandyal. The experimental soil was clay in texture, and it was moderately alkaline in reaction with a pH of 8.6, EC of 0.15 dSm-1, low in organic carbon (0.57%) and low in available nitrogen (146.2 kg ha-1), medium in available phosphorus (33.2 kg ha-1) and high in potassium (395.6 kg ha-1). Variety NJ-2647 was sown with a spacing of 45× 15 cm. The experiment was laid out in split plot design with three replications and treatment combinations of three irrigation levels and four nitrogen levels making twelve treatments.
The three irrigation levels viz., no irrigation (rainfed), one irrigation and two irrigations and four nitrogen levels viz., 90, 120, 150 and 180 kg N ha-1. Recommended dose of phosphorus (40 kg ha-1) and potassium (30 kg ha-1) were applied uniformly to all the treatments. Nitrogen was applied in two equal splits. Half of nitrogen along with full dose of phosphorus and potassium was applied as basal at the time of sowing. The remaining quantity of nitrogen was top dressed at knee-height stage of crop. First irrigation was given at 35 DAS and second irrigation was given at 75 DAS. Total amount of rainfall received during crop growing period was 20.9 mm with three rainy days. Observations were recorded on growth parameters such as plant height, number of green leaves, dry matter production and yield attributes viz., number of grains per panicle, grain weight per panicle, 1000 grain weight, grain yield, stover yield and harvest index.
At 30 DAS, Plant height varied significantly with irrigation levels at different growth stages. Significantly taller plants (71.2 cm) were produced with two irrigations compared to no irrigation (67.9 cm). At 60 and 90 DAS, taller plants (135.8 and 146.1 cm at 60 and 90 DAS, respectively) were produced with two irrigations which was at par with one irrigation (132.1 and 144.4 cm at 60 and 90 DAS, respectively) but these two treatments were significantly superior to no irrigation (106.8 and 120.7 cm at 60 and 90 DAS, respectively). Since water is a constituent of protoplasm which helps in maintaining cell turgor pressure and also by encouraging the cell elongation, increase the stem internodal length and there by produced taller plants (Aulakh et al., 2013).
At 30 DAS, significantly taller plants (71.0 cm) were produced with the application of 180 kg N ha-1 while shorter plants (68.5 cm) were produced with 90 kg N ha-1. Application of nitrogen at 180 kg N ha-1 produced taller plants (130.4 and 140.1 cm at 60 and 90 DAS, respectively) than 150, 120 and 90 kg N ha-1. However, plant height recorded with 180 kg N ha-1 was statistically at par with 150 and 120 kg N ha-1 at 60 and 90 DAS, but significantly superior over 90 kg N ha-1. Increase in plant height might be due to the fact that nitrogen promotes plant growth and increases the number and length of the internodes which results in progressive increase in plant height. These findings are in conformity with Eltelib and Eltom (2006).
Plant height of white sorghum was significantly influenced by interaction effect of irrigations and nitrogen levels at 60 DAS whereas at 30 and 90 DAS it was non significant. Higher plant height was recorded with two irrigations (143.2 cm) at nitrogen level of 180 kg ha-1 which was on par with two irrigations at 120 and 150 kg ha-1 and one irrigation at 120, 150 and 180 kg ha-1. Significantly the lower value of plant height was recorded with no irrigation at 90 DAS which was on par with at same level of irrigation at 120, 150 and 180 kg ha-1.
At 30 DAS, the number of green leaves did not differ with one irrigation (9.3) and no irrigation (9.3) but it was higher with two irrigations (9.5). Being at par with two irrigations, one irrigation produced significantly higher number of green leaves per plant (12.4 at 60 DAS) than no irrigation (12.0 at 60 DAS). However, at 90 DAS, two irrigations produced significantly higher number of green leaves per plant (8.7) than no irrigation (7.2) and one irrigation (7.7). Lower number of leaves per plant might be due to lower leaf water potential at water scarce irrigation regimes leading to more leaf senescence during later growth stages of the crop (Aulakh et al., 2013).
At 30 and 60 DAS, application of 180 kg N ha-1 produced maximum number of green leaves over 90 kg N ha-1 but was noticed to be on par with 120 and 150 kg N ha-1. At 90 DAS, application of 180 kg N ha-1 resulted in significantly higher number of green leaves per plant (8.4) over 90 (7.4), 120 (7.6) and 150 (8.0) kg N ha1. Dixit et al. (2005) also got significant response to nitrogen from 40 to 80 kg N ha-1.
The interaction between irrigations and nitrogen levels was found to be significant for number of green leaves per plant at 60 DAS. Maximum number of green leaves per plant was obtained with two irrigations at 180 kg N ha-1 which was on par with two irrigations at 150 kg
N ha-1 and one irrigation at 150 and 180 kg N ha-1 and no irrigation at 180 kg N ha-1 while minimum number of green leaves per plant was observed with no irrigation at 90 kg N ha-1 and was on par with 120 kg N ha-1 at same level of irrigation.
Dry matter production was not significantly influenced by irrigations at 30 DAS. At 60 DAS, being at par with two irrigations (138.3 g plant-1), one irrigation (132.2 g plant-1) produced significantly higher dry matter compared to no irrigation (120.3 g plant-1). At 90 DAS, significantly higher dry matter production (291.7 g plant-1)
was recorded with two irrigations followed by one irrigation (253.4 g plant-1) and no irrigation (236.5 g plant-1). More nutrient mobility coupled with higher nutrient uptake under higher irrigation regime might have increased the photosynthetic activity and leaf area index which enhanced the dry weight of plants (Aulakh et al., 2013).
At 30 DAS, significantly higher dry matter (29.8 g plant-1) was produced with 180 kg N ha-1 but it was statistically at par with 150 kg N ha-1 (29.4 g plant-1). Significantly higher dry matter was produced with 180 kg N ha-1 (142.9 and 284.7 g plant-1 at 60 and 90 DAS, respectively) which was on par with but significantly superior over 120 and
90 kg N ha-1. The improvement in morphological as well as physiological parameters due to fertilizer application might have resulted into better interception of radiant energy leading to higher photosynthesis there by higher accumulation of dry matter per plant. Similar observation was also made by Patidar and Mali (2004).
Dry matter production of sorghum was significantly influenced by combined effect of irrigations and nitrogen levels at 60 DAS whereas at 30 and 90 DAS it was non significant. Higher dry matter was produced with two irrigations at nitrogen level of 180 kg ha-1 but it was on par with two irrigations at 120 and 150 kg N ha-1 and one irrigation at 150 and 180 kg N ha-1 and no irrigation at 180 kg N ha-1. Lower dry matter was produced by no irrigation at 90 kg N ha-1.
Two irrigations recorded significantly higher number of grains per panicle (1962) than no irrigation (1179), but was comparable with one irrigation (1947). The lowest number of grains per panicle might be due to drought stress that could be related to the decrease of ear length and diameter. Shortage of soil moisture strongly influences the growth and development of reproductive organs and reduces the yield. Similar results were reported by Morad et al. (2004). The highest number of grains per ear panicle was recorded with the application of 180 kg
N ha-1 (1855) but it was comparable with 150 kg N ha-1 (1833) and significantly superior to 120 kg N ha-1 (1610) and 90 kg N ha-1 (1486). Higher number of grain per panicle might be due to increase in the fertility of flowers and increase in leaf area and duration and resulted into increase in supplying assimilates for the sink (Mousavi et al., 2012).
Among irrigation levels, significant variation was observed with regard to grain weight per panicle. Two irrigations recorded significantly higher grain weight per panicle (66.4 g) compared to no irrigation (39.8 g) but it was statistically comparable with one irrigation (64.1 g). Significant increase in grain weight per panicle was observed with increase in levels of nitrogen from 90 to 150 kg N ha-1. The highest grain weight per panicle (62.7 g) was recorded with the application of 180 kg N ha-1 but it was comparable with 150 kg N ha-1 (61.2 g). Significantly lower grain weight per panicle was recorded with 90 and 120 kg N ha-1 which were comparable with each other. Higher grain weight per panicle might be due to enhancement in number of grains per panicle and thousand grain weight. The results are in conformity with Pushpendra Singh et al. (2012) who reported that increase in grain weight per panicle might be due to enhancement in grain number per panicle and weight of individual grain.
Two irrigations produced higher 1000 grain weight (34.3 g) which was significantly superior to no irrigation
(33.9 g) and one irrigation (34.1 g). Water accelerates the process of photosynthesis, ultimately resulting into accumulation of more photosynthates which might have helped in increasing the size and weight of the grains resulting into higher test weight of grains (Kachhadiya et al., 2010). Significantly higher values for 1000 grain weight (35.4 g) was recorded at higher nitrogen level i.e. 180 kg N ha-1 compared to lower levels of 90 and 120 kg
N ha-1 while significantly lower test weight was recorded with the application of 90 kg N ha-1 (32.3 g). The increase in 1000 grain weight at higher level of nitrogen might be due to greater assimilating surface at reproductive development that resulted in better grain formation because adequate production of metabolites and their translocation towards grain which showed improvement in nutrient concentration and up take. This might have resulted in increased weight of individual grain expressed in terms of test weight. Similar observation was reported by Pushpendra Singh et al. (2012).
Irrigation levels significantly influenced the grain yield. Application of two irrigations and one irrigation did not bring any significant difference in grain yield, but produced significantly higher grain yields (6101 and 6092 kg ha-1) respectively over no irrigation (2956 kg ha-1). Adequate supply of water under which plant become physiologically more active and also more nutrient availability might have been increased and ultimately
resulted in improved growth and development of sink. The similar observations were recorded by Bhuva and Sharma (2014).
Significantly, higher grain yield (5486 kg ha-1) was recorded with the application of 180 kg N ha-1 but was comparable with 150 kg N ha-1(5462 kg ha-1). Application of 90 kg N ha-1 produced significantly lower grain yield (4392 kg ha-1). The magnitude of increase with 180 kg N ha-1 was 24.9, 12.9 and 0.4 per cent over 90, 120 and 150 kg N ha-1, respectively. Significant improvement in the grain yield was due to marked improvement in yield attributes like number of grains per panicle, grain weight per panicle, 1000 grain weight and growth parameters like dry matter production and number of green leaves per plant. These results are in corroboration with Dixit et al. (2005).
The interaction effect of irrigation levels and nitrogen levels on grain yield of sorghum was significant. Significantly higher grain yield (6963 kg ha-1) was produced with two irrigations at 180 kg N ha-1 but was on par with two irrigations at 150 kg N ha-1 (6947 kg ha-1). On the other hand, lower grain yield (2663 kg ha-1) was produced with no irrigation at 90 kg N ha-1 which was on par with no irrigation at 120 kg N ha-1 (2943 kg ha-1).
Significantly, higher stover yield (8669 kg ha-1) was recorded with two irrigations which was comparable with one irrigation (8033 kg ha-1). However, both the treatments were significantly superior over no irrigation which produced the lowest stover yield (7665 kg ha-1). The increased stover yield might be due to better vegetative growth and higher dry matter production with frequent irrigations. Similar results were obtained by Niveditha et al. (2015).
Application of nitrogen exerted significant influence on stover yield of sorghum. Significantly higher stover yield (8364 kg ha-1) was recorded with the application of
180 kg N ha-1 which was at par with 150 kg N ha-1 (8259 kg ha-1) but significantly superior over 120 and 90 kg N ha-1 (7989 and 7878 kg ha-1, respectively) and these treatments viz., 120 and 90 kg N ha-1 were on par with each other. The magnitude of increase in stover yield with
180 kg N ha-1 was 6.8 and 11.7 per cent over 120 and 90 kg N ha-1, respectively. Higher stover yield could be attributed to more plant height, higher number of green leaves per plant and higher dry matter production. Madhukumar et al. (2013) and Wani et al. (2004) also made similar observations.
The interaction effect of irrigations and nitrogen levels on stover yield of sorghum was significant. Higher stover yield (8913 kg ha-1) was produced with two irrigations at 180 kg N ha-1 but was on par with two irrigations at 150 kg N ha-1 (8840 kg ha-1) and 120 kg N ha-1(8480 kg ha-1). On the other hand, lower stover yield (7480 kg ha1) was produced with no irrigation at 90 kg N ha1 which was on par with no irrigation at 120,150 and 180 kg N ha1 and also comparable with one irrigation at 90 and 120 kg N ha-1.
One irrigation recorded significantly higher harvest index (43.1) than two irrigations (41.1) and no irrigation (27.8). Harvest index increased with increased levels of nitrogen. Higher harvest index (38.7) was recorded with the application of 150 kg N ha-1 which was significantly superior over 120 kg N ha-1 (37.0) and 90 kg N ha-1 (35.0). Harvest index was significantly influenced by interaction effect of irrigation levels and nitrogen levels. Two irrigations recorded significantly higher harvest index (44.0) at 150 kg N ha-1 which was on par with two irrigations at 180 kg N ha-1 (43.9), one irrigation at 90, 120, 150 and 180 kg N ha-1. The lowest harvest index (26.2) was recorded with no irrigation at 90 kg N ha-1 and was on par with no irrigation at 120 kg N ha-1(27.8).
White sorghum can be grown successfully by giving one irrigation with the application of 150 kg N ha-1 (as it was comparable with 180 kg N ha-1) for realizing higher yields in vertisols of Kurnool district during post rainy season.