The release of nutrients from most organic amendments is a slow process, primarily dependent on soil mineralization processes and the uptake of these elements by plants influences a range of physiological processes and morphological characteristics (
Tiemens-Hulscher et al., 2014). When growing crops with a short growing season, this must be taken into account because organic fertilization requires time for decomposition and nutrient release. Therefore, in the initial phases of plant development, an inorganic source is also necessary to meet their needs. The results obtained in this study correspond with these observations and during the first assessment in the Flowering phase, the growth response of leguminous plants to different fertilization methods (organic, mineral, combined) is clearly evident. The data clearly indicates that the plants in T
1 exhibited the least vegetative growth (Table 1). The largest stem diameter was observed in beans subjected to organo-mineral fertilization T
4 (0.75 cm), but all three fertilized treatments fall into the same homogeneous group and the differences between them are not statistically significant. The combined fertilization also resulted in the highest number of inflorescences and nodules in the root system (28.50 and 61.00 per plant, respectively) with significant differences between the treatments. Similar results have been reported by
Santosa et al., (2017), Ahmadi and Arain (2021) and
Qadiri et al., (2023).
For the other indicators (plant height, number of leaves, leaf area (LA) and biomass) the highest values were obtained with mineral fertilization (Table 1). Unlike leaf area, where no significant differences were found depending on the type of fertilization and all treatments fell into the same homogeneous group, the highest values for leaf mass were recorded with mineral and combined fertilization. The differences with the other varians are significant at 95% confidence (LSD≤9.994). The recorded stem masses of the fertilized treatments show differences within the limits of statistical error and only their differences with the control are significant (LSD≤9.243) (Fig 1a).
The trend of better vegetative development in plants fertilized with mineral and combined organo-mineral fertilizers is also observed during the assessment in the fruiting stage (Table 2). The highest number of pods and their mass were obtained from the with entirely organic fertilization (T
2). The number of pods from all tested variants falls into one homogeneous group, with no significant difference between them. However, the differences in pod mass are significant between T
2 and the others treatments (LSD≤34.358). Additionally, the number of nodules in the root system of bean plants under organic fertilization is several times higher than in the other fertilization treatments (122.50 per plant). This clearly indicates that organic fertilization creates better conditions for the development of nitrogen-fixing bacteria, which in turn leads to better nitrogen availability from the soil-this reflects positively on the growth and fruit-bearing of the plants. It is well known that beans absorb nitrogen most intensively during their reproductive phase (from the beginning of flowering to seed maturation) and the higher quantity of nitrogen-fixing bacteria in the roots could be considered the main reason for the higher number of pods and their mass. Nevertheless, the vegetative indicators (Fig 1b, Table 2) suggest that entirely organic fertilization is insufficient to optimally meet the plants’ needs. This observation is confirmed by
Mitchell and Tu (2005) and
Mohanty et al., (2018), who state that neither organic nor mineral fertilizers alone can address the challenges of sustainable agriculture. However, there are proven benefits from combining them to improve plant nutrition and fruit-bearing.
The chlorophyll content in leaves is used as an indicator of photosynthetic activity, the nitrogen status of the plant and the presence of a potential deficiency of nitrogen (
Jongschaap and Booij, 2004;
Costache et al., 2011; Larimi et al., 2014).
The content of plastid pigments in the leaves of beans in the present experiment was determined in both assessment phases (Fig 2). Predictably, the overall pigment content was higher at the first sampling. A trend of the highest values is observed in T
4 (combined fertilization treatment). While the differences with the other variants were not strongly pronounced in the first assessment, they were statistically significant for all examined pigments in the second phase.
The content of N, P and K in plants, recorded during the flowering phase of the leguminous plants, follows the phenological observations and biometric measurements. The highest values were recorded in T
3 (mineral fertilization treatment) (Table 3). In the second assessment, the better conditions for the development of nitrogen-fixing bacteria with the application of an organic nutrient source contributed to nitrogen uptake by the plants, with the highest nitrogen content observed in T
2 (4.59% N), followed by T4 (4.54% N). The content of P and K was highest in the leaves and stems of the plants from the organo-mineral fertilization variant, with 0.48% P and 3.32% K, respectively. These results support
Qadiri et al., (2023), who stated that the integrated application of organic and mineral fertilizers is an effective way to supply plants with phosphorus and potassium in bean production.
A comprehensive measure of the productivity of the agroecosystem is the yield obtained, formed as a result of the impact of all environmental components. One of the frequently used indicators for predicting potential yields is leaf area, which is also an indicator of the use of water and nutrients by plants during their vegetative period.
Gunton and Evenson (1980) reported a strong correlation between leaf area in the early stages of bean development and the yields obtained. In an experiment with 12 different bean varieties,
Bascur et al., (1985) confirmed the critical nature of changes in this indicator. The results obtained in the present study correspond with this finding, as the correlation established between LA and the yields obtained is high (Fig 3).
In many cases, yields are genetically determined and the observed differences are due to fluctuations within the variety’s genetic limits. These variations are typically induced by optimizing the nutritional regime. The total yield of beans obtained at the end of the present experiment supports these statements (Fig 4). The highest yield was recorded in T
3 and T
4 (mineral and combined fertilization treatments), with the data being almost equal and falling into one homogeneous group, with no statistically significant difference between them. According to numerous researchers, beans respond well to the integrated use of mineral fertilizers in combination with organic ones, thus improving soil physical properties and, consequently, the delivery of nutrients. Organic amendments are also a source of key micronutrients in optimal quantities, which further improves the conditions for bean growth and development
(Band et al., 2007; Shwetha et al., 2012; Srinivasan et al., 2015; Kamble et al., 2016; Sachan and Krishna, 2021). The results obtained in the present study correspond with those reported by
(Lima et al., 2009; Dash et al. 2019) and
Barcchiya and Kushwah (2017).
Sustainable resource management in agriculture is a significant challenge today. There is a need to boost yields while also maintaining a positive nutrient balance and preserving soil fertility over time. The obtained results confirm that mineral fertilization is crucial and should not be excluded from sustainable land use strategies. Instead, it should serve as the foundation and be integrated with organic substrates to achieve ecological sustainability goals.
