Yield components
Number of cluster per plant, number of flower per cluster, and fruit set percentage
Data on the numbers of flower clusters per plant, the number of flowers per cluster, and the percentage of fruit set are shown in Table 3, and it is evident from these tables that nitrogen and Azzola had a significant (p < 0.001) effect on the aforementioned parameters. The combined application of 1.5 g nitrogen and 75 g Azzola increased the number of flower clusters per plant, flowers per cluster, and the percentage of fruit set by 744%, 111.86%, and 195.77%, respectively, compared to the control (Table 2). The rise in cluster size could be attributed to the tomato plants' healthy overall growth and development receiving an adequate supply of nutrients.
Table 3
Interaction effect of nitrogen and azzola bio-fertilizer on number of clusters per plant, number of flowers per cluster, and fruit set percentage
Nitrogen | Azzola | Number of cluster/plant | Number of flower/cluster | Fruit set percentage (%) |
0 | 0 | 2.33o | 2.53l | 27.63n |
| 25 | 3.00no | 2.69kl | 29.84mn |
| 50 | 3.67mn | 2.81jk | 31.93m |
| 75 | 7.01j | 3.10gh | 49.26i |
0.5 | 0 | 4.33lm | 2.89ij | 36.96l |
| 25 | 4.67l | 2.97hij | 40.74k |
| 50 | 9.33h | 3.41f | 58.56g |
| 75 | 11.67f | 3.63e | 65.59e |
1 | 0 | 5.67k | 3.03ghi | 45.44j |
| 25 | 10.33j | 3.51ef | 61.57f |
| 50 | 14.33d | 4.03d | 71.63c |
| 75 | 15.67c | 4.30c | 77.43b |
1.5 | 0 | 8.33i | 3.20g | 53.56h |
| 25 | 12.67e | 3.90d | 69.01d |
| 50 | 18.00b | 4.62b | 79.48b |
| 75 | 19.67a | 5.33a | 81.72a |
LSD (0.05) | | 0.50 | 0.10 | 0.90 |
CV (%) | | 6.32 | 3.35 | 1.97 |
The mean values followed by the same letter (s) in the same column are not significantly different at the 5% level of significance.
Number of fruit per cluster
The interaction between nitrogen and azzola had a significant (p < 0.05) effect on the number of fruits per cluster. The application of 1.5 g of nitrogen along with 75 g of azzola was shown to be the most efficient in increasing the quantity of fruits per cluster when compared to applying azzola or nitrogen alone (Fig. 1). This combination produced the largest number of fruits per cluster. The current findings agree with those in tomatoes by Kumar et al. (2017). Similar to this, Arya et al. (1999) found that as the nitrogen content increased, so did the quantity of fruits produced per plant.
Fruit diameter
Nitrogen and Azzola had a significant (p < 0.001) effect on fruit diameter. The widest fruit diameter was recorded at 1 to 1.5 g of nitrogen, and the lowest was recorded from the control plot (Table 4). Application of 1.5 g of nitrogen increased fruit diameter by 17.39% compared to the control plot. The reason for the larger fruit diameter from the highest amount of nitrogen might be due to enhanced cell division and enlargement by supplying a high amount of nutrients like nitrogen fertilizer. Mishra and Singh (2006) also reported that as the level of nitrogen increased, the fruit size increased. The findings are in agreement with the findings of Biswas et al. (2015). The application of 50 and 75 g of azzola produced the maximum fruit diameter, whereas the control plot produced the lowest (Table 4). Fruit diameter rose by 16.13% on plants given 75 g of Azzola compared to the control. This may be due to the fact that organic fertilizer could progressively release macro- and micronutrients into the soil solution and maintain nutritional balance for the healthy development of agricultural plants from the vegetative stage through the reproductive stage.
Table 4
Main effect of nitrogen and azzola bio-fertilizer on fruit diameter of tomato fruit.
Nitrogen (g) | Fruit diameter (mm) |
0 | 41.35c |
0.5 | 44.38b |
1 | 46.70a |
1.5 | 48.54a |
LSD (0.05) | 2.16 |
Azzola (g) | |
0 | 41.24c |
25 | 44.78b |
50 | 47.04a |
75 | 47.89a |
LSD (0.05) | 2.16 |
CV (%) | 5.73 |
The mean values followed by the same letter (s) in the same column are not significantly different at the 5% level of significance.
Marketable fruit yield per plant
The interaction effect of nitrogen and azzola bio-fertilizer had a significant (p < 0.01) effect on marketable fruit yield. The application of 1.5 g nitrogen and 75 g Azzola produced the highest marketable (1126.6 g) yield of tomato fruits, and it was lowest at the control treatment (Table 5). The possible reason for the increase in yield as an increase in organic and inorganic nitrogen might be due to better development of the root system and the possible synthesis of plant growth hormones. Mallika et al. (2022) also agreed with the present findings. Combination of azolla and urease inhibitors to reduce ammonia volatilization and increase nitrogen use efficiency and rice grain yield Yang et al. (2020). Bipradas et al. (2016) found that the combination application of 50% organic fertilizer and inorganic fertilizer resulted in maximum tomato production. Saha et al. (2017) observed a maximum yield of tomato when applying a combined dose of organic and 50% of the recommended dose of inorganic fertilizer compared to a single dose of organic or inorganic fertilizer. On the other hand, several authors had reported that tomato plants fertilized with inorganic fertilizers produced higher fruit yields because those fertilizers contained soluble inorganic nitrogen and other nutrients helped to produce higher yields (Chassy et al., 2006; Riahi et al., 2009).
Warner et al. (2004) reported that fruit yield increased with N up to 250 kg N ha− 1. Fiseha (2014) also reported that the average fruit weight significantly increased as the rate of N increased from nil to higher rates of N nutrient application to tomato plants. Ren et al. (2010) reported that the application of N fertilizer up to 645 kg ha− 1 increased the marketable fruit yield of tomatoes. Bipradas et al. (2016) found that the combination application of 50% organic fertilizer and inorganic fertilizer resulted in maximum tomato production. Saha et al. (2017) observed maximum tomato yield when applying a combined dose of compost and 50% of the recommended dose of inorganic fertilizer compared to a single dose of organic or inorganic fertilizer. Fertilizer application resulted in higher yields than organic and inorganic fertilizers alone in cabbage (Golam, 2015) and eggplant (UIIah et al., 2008). Azolla could be used to enhance yield and nutrient concentrations in radish and spinach. As a green manure, azzola can improve soil properties and increase the microbial population in the soil, thereby increasing soil fertility and rice yield (Kollah et al., 2016). Azzola released nitrogen, and plants absorb a sufficient amount of available N, which promotes the accumulation of dry matter and increases grain yield (Guo et al., 2019). Azzola can increase soil nutrient content, improve soil properties, and increase the soil microbial population (Zhang et al., 2020). Nitrogen accelerates the development of growth and reproductive phases and protein synthesis, thus promoting fruit weight. The findings are in agreement with the findings of Reddy et al. (2002).
Table 5
Interaction effect of nitrogen and azzola bio-fertilizer on marketable and total fruit yield per tomato
Level of fertilizer (g) | |
Nitrogen | Azzola | Marketable fruit (g/plant) |
0 | 0 | 130.1k |
| 25 | 163.6k |
| 50 | 289.4j |
| 75 | 484.0gh |
0.5 | 0 | 323.1j |
| 25 | 359.1ij |
| 50 | 650.3f |
| 75 | 799.4de |
1 | 0 | 439.2hi |
| 25 | 731.4ef |
| 50 | 925.1c |
| 75 | 938.2bc |
1.5 | 0 | 562.3g |
| 25 | 876.9cd |
| 50 | 1016.0b |
| 75 | 1126.6a |
LSD (0.05) | | 37.79 |
CV (%) | | 7.39 |
The mean values followed by the same letter (s) in the same column are not significantly different at the 5% level of significance.
Fruit quality parameters
Fruit length, width, shape index and pericarp thickness
The physical quality characteristics of tomato fruit (fruit length, width, and pericarp thickness) were significantly influenced by nitrogen and azzola (p < 0.05). The highest levels of nitrogen fertilizer produced tomato fruit with the best physical quality characteristics, whereas the control produced the lowest value (Table 6). An increasing supply of important plant nutrients may be to blame for this. The development of the growth and reproductive phases, as well as protein synthesis, are all enhanced by nitrogen, which lengthens the fruit. According to Akanbi et al. (2007), the amount of N-element available to plants during fertilization, cell mitotic activity, and enlargement are positively connected with fruit size.
Table 6
Effect of nitrogen and azzola bio-fertilizer on fruit length, width, pericarp thickness, and shape index.
Nitrogen (g) | Fruit length (cm) | Fruit width (cm) | Fruit shape index | Pericarp thickness (mm) |
0 | 5.08b | 3.92c | 1.03c | 6.22c |
0.5 | 5.25b | 4.12bc | 1.32b | 6.96bc |
1 | 5.36b | 4.32ab | 1.71a | 7.95ab |
1.5 | 5.99a | 4.51a | 1.74a | 8.79a |
LSD (0.05) | 0.31 | 0.25 | 0.28 | 1.31 |
Azzola (g/pot) | | | | |
0 | 5.12c | 4.09b | 1.26b | 5.62c |
25 | 5.29bc | 4.07b | 1.27b | 6.78bc |
50 | 5.46b | 4.26ab | 1.59a | 8.02b |
75 | 5.80a | 4.45a | 1.67a | 9.50a |
LSD (0.05) | 0.31 | 0.25 | 0.28 | 1.31 |
CV (%) | 6.76 | 7.2 | 22.9 | 20.98 |
The mean values followed by the same letter (s) in the same column are not significantly different at the 5% level of significance.
Total soluble solids (TSS)
A small increase in total soluble solids content is of considerable economic importance for the tomato processing industry because even a small increase in its value can significantly increase the product yield and decrease the cost of dehydration of puree into sauce and paste (Young et al., 1993). The analysis of variance revealed that total soluble solids were actually affected by the main effects of nitrogen and azzola fertilization. The highest values were found in tomatoes treated with 1 and 1.5 g of nitrogen fertilizer (Table 7). Etissa et al. (2014) found that with the increase in nitrogen fertilization rate, the total soluble solids value increased and peaked at a rate of around 100 kg, and beyond this value, the TSS value tended to decrease. The result is contrary to the findings of other researchers reported decreasing trends in TSS value due to a decrease in nitrogen fertilizer (Kuscu et al., 2014; Simonne et al., 2007).
With regard to the azzola, the highest values of TSS were recorded from 75 g of azzola treatment. Application of azzola also affects the TSS value of tomato fruit. The highest number of total soluble solids was obtained from the tomato juice, which received 75 g of azzola, while the smallest number of total soluble solids was obtained from the tomato fruit juice, which did not receive any fertilizer or from the control (Table 7). Application of 75 g of azzola fertilizer increased total soluble solids by 10.20% compared to the control. The present study showed that the tomato plant treated with Azzola had a larger TSS value than the plant treated with nitrogen fertilizer. These results are in full accordance with other studies reporting that tomatoes grown under organic production systems contain higher total soluble solids (Chassy et al., 2006; Barrett et al., 2007; Rickman Pieper and Barrett, 2008).
Titratable acidity (TA)
Titratable acidity is an important quality attribute of processing tomatoes since it contributes to the flavour of tomato products. The data pertaining to titratable acidity are given in Table 7, from which it is evident that TSS was significantly (p < 0.05) influenced by nitrogen fertilizer. The TSS of tomatoes in the present study ranged from 4.13 to 4.55 0Brix (Table 6). The highest value of TSS was recorded from 1 and 1.5 g of nitrogen, and the lowest was obtained from the control, and it was statistically at par with 0.5 g of nitrogen. The tomato fruits treated with 1.5 g nitrogen fertilizer increased titratable acidity by 22.6% compared to the control (Table 7). Azzola had a significant effect on titratable acidity. The highest values of TA were obtained from 25 to 75 g of azzola and the lowest was recorded from the control. Titratable acidity is also influenced by different amounts of azzola biofertilizer. The plant treated with 75 g/pot of azzola increased the titratable acidity by 24.6% compared to the control.
From the data obtained above, titratable acidity was influenced by both nitrogen and Azzola independently. In accordance with the present result, Wang et al. (2007) and Kuscu et al. (2014) also reported an increase in the value of titratable acidity with an increasing nitrogen dose. This is consistent with the conclusion of Toor et al. (2006), who found that tomatoes grown in nitrate-dominant fertilizer solutions had significantly lower titratable acid values than tomatoes grown in chicken manure, grass/clover mulch, and mineral solutions with a lower nitrate/ammonium ratio.
Sugar-to-acid ratio (SAR)
The analyzed results revealed that the sugar-to-acid ratio was significantly (p < 0.001) affected by the main factors nitrogen and azzola but not the interaction effect of nitrogen and azzola. Different amounts of nitrogen fertilizer also affect the sugar-acid ratio of tomatoes. Using 1.5 g/pot of nitrogen fertilizer increases the sugar/acid ratio by 23.19% compared to unfertilized tomatoes (Table 7). Azzola fertilizer increased the SAR by 40.60% compared to the control (Table 7). Higher salt/acid levels or TSS/TA ratios in organic treatments may be related to the increased vegetative growth of conventional tomato plants. Increased leaf carbon distribution or increased fruit shading due to excess foliage can reduce total soluble solids and titratable acidity (Rickman Pieper and Barrett, 2008).
Table 7
Effect of nitrogen and azzola bio-fertilizer on TSS, TA and SAR
Nitrogen (g) | TSS (0Brix) | TA (%) | SAR |
0 | 4.19b | 0.62b | 6.90bc |
0.5 | 4.28b | 0.68b | 6.04c |
1 | 4.37ab | 0.68ab | 7.25b |
1.5 | 4.54a | 0.76ab | 8.50a |
LSD (0.05) | 0.2 | 0.08 | 0.91 |
Azzola (g) | | | |
0 | 4.13c | 0.61b | 6.28c |
25 | 4.26bc | 0.69a | 6.25c |
50 | 4.43ab | 0.69a | 7.33b |
75 | 4.55a | 0.76a | 8.83a |
LSD (0.05) | 0.20 | 0.08 | 0.91 |
CV (%) | 5.65 | 13.52 | 15.18 |
The mean values followed by the same letter (s) in the same column are not significantly different at the 5% level of significance.