The results recorded in the present experiment revealed appreciable and significant variation in different vegetative and physiological growth parameters, yield attributing characters and yield of sunflower due to different treatments of integrated nutrient management in gangetic alluvial soils of West Bengal. The basic objectives of integrated plant nutrition systems (IPNS) are to reduce the inorganic fertilizer requirement, to restore organic matter in soil, to increase nutrient use efficiency and to retain soil quality in terms of physical, chemical and biological properties. Bulky organic manures may not be able to supply adequate amount of nutrients, nevertheless their role becomes important in meeting the above objectives (Subbarao and Sammireddy, 2008)
Sunflower plants exhibited a typical linear pattern of growth in plant height, irrespective of variation in treatments till 60 days after sowing.After 60 days of sowing, the rate of increase in plant height has shown a diminishing rate of increase (Table 1). The increase in height with T10 i.e.
VC @ 2.5 t/ha + PSB + AZ +50% RDF + Foliar spray NPK 19:19:19 may be attributed to rapid mobilization of N, P, K from inorganic fertilizers and steady supply of N and P from VC which might have met N and P requirement in cell elongation and cell division at early growing period and later from foliar application at critical stages of plant growth.This might be due to release of P and N as a result of action of P solubilizing bacteria and azotobacter. The production of auxin and gibberellin type plant growth regulators is known to help in higher plant growth.Azotobacter inoculation showed improved plant growth due to plant growth substances produced and released continuously in the rhizosphere and it increased the ability of absorption of nutrients by the crop resulting in maximum plant height which was significantly superior in T10
. These results showed that AZ and PSB performed better in presence of vermicompost (Raj and Mallick, 2017
and Mukherjee et al., (2019).
Table 1: Effect of treatments on physiological growth parameters, yield attributing character, seed yield of sunflower.
The results obtained are in confirmation with the findings of Raj and Mallick, (2017) Mukherjee et al., (2019) Gayathri et al., (2004)
also reported that combined application of biofertilizers, vermicompost with inorganic fertilizers significantly increased the number of leaves, leaf area and stem girth in limonium.
The increase in dry matter production under high levels of phosphorus and nitrogen may thus be attributable to the efficient physiological and metabolic processes resulting in luxuriant vegetative growth, functional photosynthesis which in turn account for synthesis of protein and carbohydrates (Fujiwara, 1965)
. Increased dry matter in this treatment might be due to positive role of the bio-fertilizer in presence of organic manures. Supply of the required nutrients through organic and inorganic sources and bio-fertilizer facilitated balanced nutrient of the crop, which resulted in enhanced dry matter in sunflower (Jeyabal et al., 2000).
Physiological growth parameters
A perusal of the data (Table 1) relating to effect of treatment on total number of green leaves per plant showed that, T10
exhibited more number of leaves per plant (20.60) followed by T6
(20.03). The minimal total number of leaves was recorded in T1
The dry matter production per plant was increased linearly and reaching maximum during 90 DAS. The maximum dry matter production (77.45 g/plant) was recorded in treatment T10
followed by T6
(77.35 g/plant). Whereas, significantly minimum dry matter production was recorded in T1
In case of crop growth rate (CGR), T10 (VC @ 2.5 t/ha + PSB + AZ + 50% RDF + Foliar spray NPK 19:19:19) had recorded maximum rate of growth (3.216 g/day/plant) followed by T6
(3.210 g/day/plant) which were at par with each other. The minimum crop growth rate was observed in T1
Yield attributing character
The results on yield attributes of sunflower revealed that application of different treatments of INM exerted profound influence on important yield contributing characters like diameter of the head, number of seeds/head and 1000-seed weight (Table 1).
Increase in yield attributes with VC @ 2.5 t/ha + PSB + AZ + 50% RDF + Foliar spray NPK 19:19:19 was attributable to adequate nutrient availability at critical growth stages and thus enhanced photosynthetic efficiency. The results are in line with the findings of Reddy et al. (2005)
. The probable reason of highest yield attributing characters might be due to higher availability of P, N and simultaneously better nutrition since early stage of growth. It means that PSB and AZ played an important role in sunflower generative growth and therefore to make a significant increase in the number of seeds per head and head diameter. Tohidi-Moghaddam et al., (2004)
reported that phosphorus solubilising organisms (PSB) increased the available phosphorus in the soil which could enhance the seed number in plant and also azotobactors fix atmospheric nitrogen and made them available to plant. The improvement of P in soil might be due to solublization of inorganic P through the secretion of soil organic acid by inoculation of phosphate-solubilizinig bacteria (PSB) (Dubey, 1997)
might have influenced favourably yield attributes.
Seed yield of sunflower had been significantly influenced due to different treatments of INM. Combined effect of T10 i.e.
VC @ 2.5 t/ha + PSB + AZ +50% RDF + Foliar spray NPK 19:19:19 was more spectacular on sunflower seed yield (Table 1). The application of 50% RDF in combination with VC, foliar spray and bio-fertilizers (PSB and AZ) produced significantly and appreciably higher seed yield over other nutrient management treatments and control. The beneficial effect of biofertilizer might be ascribed to biological N fixation and solubilization of P by phosphate solubilizing bacteria (Raj and Mallick, 2017; Mukherjee et al., 2019.
Microorganisms with phosphate solubilizing potential increased the availability of soluble phosphate and enhance the plant growth and yield due to better root growth and increase uptake of nutrients (Watson et al., 1965, Kucey et al., 1989; Ponmurugan and Gopi, 2006)
and nitrogen fixing bacteria azotobactor also increased the plant growth and yield due to luxuriant vegetative growth (Fujiwara, 1965)
Thus, it is assumed that the better growth, enhanced yield attributes and final seed yield of sunflower under reduced rate of RDF at 50% in conjunction with organic manure and bio-fertilizers might be due to the increased availability of essential nutrients from integration of chemical fertilizer, organic manure and bio-fertilizer. The findings are in close conformity with the earlier findings of Jeyabal et al., (2000), Raj and Mallick,(2017)
and Mukherjee et al., (2019).
In this experiment, the benefit: cost ratio was also worked out for different levels of NPK fertilizers, organic manures and biofertilizers (Table 2). The cost of cultivation of integrated nutrient management treatments was higher than sole application of 100% RDF resulting in highest benefit: cost ratio was recorded in sole application of recommended dose of chemical fertilizer treatment. Lowest benefit: cost ratio was noticed where only sole farm yard manure or vermicompst was applied (0.72 and 0.77 respectively). But integration of chemical fertilizer, farm yard manure or vermicompost along with biofertilizers (INM treatments) gave intermediate the net monetary returns and benefit: cost ratio. Among the INM treatments, the net monetary returns and benefit: cost ratio was found highest with 50% RDF integrated with VC @ 2.5 t/ha + PSB + AZ + 50% RDF + One Foliar spray of NPK 19:19:19.
Table 2: Effect of different treatments on benefit: cost ratio in sunflower.