Assessing the influence of planting time and fertilization on growth, flowering, yield and soil properties of chrysanthemum

3.1 Vegetative and flowering characteristics

Data were collected on randomly selected five plants from each replication and different vegetative characters (such as plant height and spread, measured with a metre rod) and flowering attributes (days taken to bud formation and stage of harvesting) were observed from the date of planting. The number of cut stems per plot was counted manually, cut flower stem length using a metre rod, flower diameter using vernier calipers; stem strength as deviation angle when placed horizontally, vase life in distilled water under room temperature and duration of flowering at harvesting of 1st cut stem till the harvesting of last cut stem).

3.2 Chemical properties

Soil samples were taken from the study area at a depth of 0 to 15 cm before laying out the experiment. Soil pH and EC were measured using 1:2 soil water suspension and were found 6.85 and 0.34 dS/m, respectively (Jackson, 1973). Soil organic carbon was determined as per Walkley and Black (1934) which was 0.92 % (rapid titration method). Available nitrogen was found 292.76 kg/ha (Subbiah and Asija, 1956). Available phosphorus was recorded 27.48 kg/ha (Olsen et al., 1954) and available potassium was recorded 315.84 kg/ha (Merwin and Peech, 1951).

3.3 Soil microbial attributes

Microbial quantification was performed using the serial dilution standard spread plate technique on three different media: nutrient agar, potato dextrose agar and Kenknight and Munaier's medium, following the protocol outlined by Subbarao (1995). The microbial population was quantified as colony-forming units per gram of soil. Additionally, microbial biomass-C was assessed using the soil fumigation extraction method given by Vance et al. (1987). $$\text{Microbial biomass}-\text{C}\left(\mathrm{\mu }\text{g}/\text{g soil}\right)=\frac{\text{EC}\left(\text{F}\right)-\text{EC}\left(\text{UF}\right)}{\text{K}}$$ where, K: 0.25 ± 0.05 (a measure of the effectiveness of microbial biomass carbon extraction), EC (F): Amount of extractable carbon in soil samples post-fumigation, EC (UF): Total extractable carbon in un-fumigated soil samples.

The dehydrogenase activity in liquid formulations was calculated using the 2,3,5-triphenyl tetrazolium chloride reduction method (Casida et al., 1964) and phosphatase activity was measured according to the procedure detailed by Tabatabai and Bremner (1969).

3.4 Statistical techniques and analysis

The data collected during the two years of experimentation in 2022 and 2023 were pooled and analyzed using SPSS statistics. Analysis of variance (ANOVA) was performed on the pooled data employing randomized block design (RBD) and the treatments were compared using the critical difference at 5 % level of significance.

4.1 Vegetative and flowering characteristics

Planting time and fertilization regimes had a significant effect on vegetative characteristics of chrysanthemum (Table 1). Among different planting times, highest plant height (71.06 cm) and spread (29.06 cm) were observed in P₁ as compared to other planting dates. FM₂ recorded the higher plant height (53.93 cm) and spread (20.57 cm) over FM₁ which recorded plant height of 47.79 cm and plant spread of 18.46 cm. Under the interaction effect, highest plant height (74.37 cm) and spread (30.56 cm) were recorded under P₁xFM₂.

Data embodied in Table 1 show that the earliest bud formation (32.45 days) and time to reach the harvesting stage (79.58 days) were recorded in P₆. Maximum cut stems/plot (49.00) were recorded under P₅ and P₆. Maximum stem length of cut flower (61.00 cm), flower diameter (11.03 cm), stem strength (10.83°), flowering duration (21.50 days) and vase life (18.92 days) were observed under P₁.

Earlier bud formation (61.85 days), lesser period taken to reach the harvesting stage (110.20 days) and more cut stems/plot (41.18), stem length of cut flower (46.09 cm), flower diameter (9.95 cm), stem strength (13.53°) and flowering duration (19.58 days) were observed in FM₂. FM₁ recorded higher vase life (17.97 days).

The interaction effect of dates of planting and fertilization regimes revealed that the earliest bud formation (31.87 days) was observed in P₆xFM₂. Maximum flower diameter (11.80 cm) was recorded in P₁xFM₂ and vase life (19.70 days) in P₁xFM₁.

4.2 Soil chemical properties

Maximum available N, P and K (318.81, 38.08 and 352.47 kg/ha, respectively) was observed in P₁ in comparison to all other planting times (Fig. 3). FM₂ resulted in maximum available N, P and K (321.71, 38.48 and 353.29 kg/ha, respectively) (Fig. 4). The interaction was found non-significant (Fig. 5).

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Fig. 3

Impact of planting time on soil available NPK.

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Fig. 4

Impact of fertilization regimes on soil available NPK (Pooled Data: 2022 & 2023).

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Fig. 5

Interaction impact of planting time and fertilization regimes on soil available NPK (Pooled Data: 2022 & 2023).

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During both study years, fertilizer regimes and planting days had non-significant effects on soil pH and EC (Figs. 6-8). Among different planting time, maximum OC (1.14 %) was observed in P₁ planting compared with all other planting time (Fig. 6). Organic fertilization recorded maximum OC (1.13 %) (Fig. 7). The interaction effect on OC was found to be non-significant (Fig. 8).

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Fig. 6

Impact of planting time on soil pH, EC and OC (Pooled Data: 2022 & 2023).

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Fig. 7

Impact of fertilization regimes on soil pH, EC and OC (Pooled Data: 2022 & 2023).

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Fig. 8

Interaction impact of planting time and fertilization regimes on soil pH, EC and OC.

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4.3 Soil microbiological properties

Data presented in Table 2 show that planting time had a non-significant effect on all the soil microbiological properties. Among different planting times, maximum dehydrogenase enzyme was recorded in P₁ (3.69 mg TPF/h/g/soil, respectively). Maximum phosphatase enzyme (24.20 mmole PNP/h/g/soil, respectively) was recorded under P₁.

Fertilization had a significant effect on soil microbial properties and data reveal that more bacterial, actinomycetes and fungal counts (133.09, 61.58 and 31.26 cfu/g soil, respectively), microbial biomass (51.85 µg/g soil) and, dehydrogenase and phosphatase enzymes (3.81 mgTPF/h/g soil, 22.52 mmole PNP/h/g soil, respectively) were recorded in FM₁. The interaction effect had no significant effect on all the soil microbiological properties.

5.1 Vegetative and flowering characteristics

Delayed planting in chrysanthemums shortened the bud formation and flowering period, whereas, early planting extended the juvenile phase, delaying flower initiation. Early-planted crop benefited from prolonged optimal long-day conditions, enhancing vegetative growth, compared to those planted later. A study on chrysanthemum cv. Aparajita found that early plantings enhanced vegetative growth (Kishore et al., 2023).

Differences in fertilization effects lead to a rise in rapid nutrient availability in inorganic fertilizers, particularly NPK which are quickly utilized by the plants. In contrast, organic fertilization with Jeevamrit had slower nutrient release, slightly affecting plant growth.

Chrysanthemums planted early had a longer vegetative growth phase, which might have allowed more energy to be stored and directed to the development of the flowers, leading to improved flowering attributes. Strong flower bud differentiation and expansion are encouraged by a prolonged time frame, which results in bigger flowers, longer stems, better vase life, longer flowering time and stronger stems. On the other hand, later plantings perceive a more rapid transition to flowering due to shorter day length which might restrict the amount of time available for optimal development of the stem and flowers, leading to less desirable floral characteristics. The highest stem count was attained despite the late planting (5^th and 6^th), which might be due to the higher plant density. Sharma et al. (2015) have also reported similar outcomes.

NPK fertilizers enhanced flowering in chrysanthemums by promoting essential physiological processes. Nitrogen aids protein and enzyme synthesis, phosphorus supports energy transfer and cell division and potassium regulates water uptake and nutrient transport. These nutrients collectively improve flowering characteristics, as also reported by Yang et al. (2003).

The beneficial microbes and organic substances that improve nutrient uptake, physiological activities and defensive mechanisms in plants treated with Jeevamrit might be responsible for the plants' longer vase life. Comparably, Thakur et al. (2023) reported the application of Jeevamrit extended the vase life in iris.

5.2 Chemical properties of soil

A significant influence of different fertilizers and planting dates on soil chemical properties was observed except for soil pH and EC. Earlier planting extends the vegetative phase, promoting enhanced root development and, thereby, improving nutrient uptake from the soil. As a consequence, this leads to higher levels of available NPK compared to late plantings (Abaza et al., 2023).

Inorganic fertilizers significantly increased soil NPK levels which might be due to their immediate and concentrated nutrient release, providing highly soluble forms of NPK for swift plant uptake which leads to a quick boost in soil nutrient availability. Both fertilization methods improved soil NPK levels, affirming the positive impact on nutrient availability. Similar results were reported with NPK application @ 100:150:100 kg/ha/year in chrysanthemum (Choudhary et al., 2022).

The organic fertilization regime led to a modest increase in OC content. This can be attributed to Jeevamrit, an organic input rich in organic matter, which enhanced soil microbial activity and fostered the accumulation of OC. Yadav et al. (2022) also reported increased OC in soil with the application of Jeevamrit in garden peas.

5.3 Soil micro-biological properties

Micro-biological properties are enhanced by the application of Jeevamrit by acting as a stimulant, promoting robust microbial activity and supporting a significant microbial population that proliferates in the soil. Jeevamrit comprises a variety of beneficial microorganisms, such as fungi, methylotrophs, actinomycetes, Azotobacter, phospho-bacteria, Pseudomonas, lactic acid bacteria etc. An increase in soil microbiological properties by Jeevamrit application has also been reported by Rathore et al. (2023).

5.4 Future prospect

Nano fertilizers enhance nutrient release efficiency, improving plant growth and yield (Singh et al., 2023a). They also mitigate abiotic stresses by activating physiological pathways (Singh et al., 2024). Jeevamrit can complement these advanced technologies. Combining Jeevamrit with nano fertilizers can create a synergistic effect, enhancing soil health and nutrient availability while promoting sustainable agricultural practices. In the context of climate change, nanotechnology combined with Jeevamrit and advanced fertilization strategies is crucial for sustainable crop production (Rajput et al., 2023). Overall, integrating nanotechnological approaches, Jeevamrit and advanced fertilization techniques holds significant potential for enhancing chrysanthemum growth, flowering and yield, while improving soil properties and effectively managing abiotic stresses (Singh et al., 2023b). Continued research and development in this field are essential to fully harness these technologies for sustainable and resilient chrysanthemum production.