Elsevier

Scientia Horticulturae

Volume 303, 20 September 2022, 111234
Scientia Horticulturae

Phosphorus and potassium supplementing bio-mineral fertilizer augments soil fertility and improves fruit yield and quality of pomegranate

https://doi.org/10.1016/j.scienta.2022.111234Get rights and content

Highlights

  • A bio-mineral fertilizer (BMF) was developed to replace chemical fertilizer.

  • The BMF was developed from low-grade minerals combined with P and K mobilizer.

  • The BMF was found as effective as P and K chemical fertilizers in pomegranate cultivation.

  • BMF application remarkably improves fruit yield and quality of as well as soil fertility.

Abstract

Large-scale use of chemical fertilizers has brought about environmental pollution and raised food safety issues besides increasing the cost of production. The present study focused on using natural minerals inoculated with nutrient mobilizing microorganism so-called bio-mineral fertilizer to partially substitute chemical fertilizers dose. Two years of field trials and a pot culture experiment were carried out with pomegranate to look into the possibility of bio-mineral fertilizer use in saving phosphorus (P) and potassium (K) chemical fertilizers application and in improving soil fertility, tree nutrition, and fruit quality. Results manifested that application of bio-mineral fertilizer significantly enhanced available nitrogen (N), P, and K content of soil and also improved concentration of P, K, magnesium (Mg) and sulphur (S) in the tree foliage. As a consequence, higher fruit yield with perceptible improvement in quality attributes viz. aril percent, 100 arils test weight, juice acidity, ascorbic acid, total phenolics, anthocyanin concentration was observed in bio-mineral treated trees. The highest yield (73.97% increase over control) was recorded with the application of 150 g tree−1 bio-mineral fertilizer which was equivalent to the yield obtained with the recommended dose of P and K chemical fertilizers. In addition, the application of bio-mineral fertilizer led to improvement in the nutritional quality of fruit and also soil microbial environment as indicated by higher microbial biomass carbon and enzymes activities. So, the results indicate that Penicillium pinophilum based bio-mineral fertilizer may be recommended to supplement P and K requirement of pomegranate tree and get maximum benefits in terms of yield, quality, and production cost savings.

Introduction

Pomegranate is an economically important fruit tree belonging to the family Puniceae. It is appreciated for its delightful fruit affluent in polyphenol, proteins, sugar, polysaccharides, vitamins and minerals (Kandylis and Kokkinomagoulos, 2020). It has been of latest attractiveness for its nutraceuticals and antioxidant properties (Maity et al., 2019). So, the demand of fruit both in the domestic and international market is widening very fast. Because of its wider adaptability and higher net return per rupee investment, the area under this crop is extending rapidly in the arid and semi-arid region of India. Pomegranate growing areas in this region are characterized by nutrient deficient, shallow gravelly soil with high phosphorus (P) and potassium (K) fixing capacity owing to its inherent mineralogical makeup (Challa et al., 2008; Pal et al., 2012; Chatterjee et al., 2014). With the intensification of pomegranate cultivation, deficiency in plant-available P and K has become a major limiting factor to the crop productivity (Bhattacharyya et al., 2015).

P and K are two major essential nutrients for the growth and development of plants. Chemical P and K fertilizers are generally applied to restock removed minerals and to optimize yield. When relatively soluble phosphatic fertilizer is applied to the soil, it easily transformed into insoluble complexes of calcium (Ca), aluminium (Al) and iron (Fe) as well as gets fixed in crystalline and amorphous aluminium silicate (Ribeiro et al., 2020). Similar is the case with potassic fertilizers which also get fixed within the soil having predominant 2:1 type expanding clay minerals into insoluble form after its application (Hamid and Bashir, 2019; Li et al., 2020). Consequently, to achieve optimum crop yield, soluble phosphatic and potassic fertilizers are applied at higher rates. However, the uninterrupted application of chemical fertilizers at a high rate has led to many unforeseen impacts. For example, the productivity cost does not increase by a constant proportion linearly resulting in an enormous waste of mineral resources. Further, millions of tons of chemical fertilizer nutrients that are applied into soil annually are not entirely taken up by plants. As high as about 90% of applied P is documented to get lost through runoff from crop fields and escape into water bodies, thereby resulting in eutrophication in the aquatic system (Ye et al., 2020). Besides, the immoderate use of chemical fertilizers brings about food safety issues.

Some studies have demonstrated that organic farming, which forbids the use of chemical fertilizers, gives an option that has the prospective to keep down adverse impact of excessive use of chemical fertilizer on the environment and at the same time produces obtained from the organic farming system are generally endowed with better nutritional quality (Oliveira et al., 2013; Graham et al., 2017; Negi et al., 2021). Following agroecological approach, undeviating use of rock phosphate (P bearing minerals) and potassium feldspar (K bearing minerals) may be environmentally more benign and agronomically more useful than soluble P and K chemical fertilizers (Basak et al., 2022). P and K containing rock materials are cheaper sources of P and K nutrients, however, nutrients from them are not readily soluble and hence, available to the plant as nutrients are released slowly over a period. Their usage as fertilizer often does not result in a significant increase in yield (Basak et al., 2017; Lompo et al., 2018).

But many soils inhabiting micro-organisms are capable of solubilizing insoluble P and K containing minerals in the soil through producing organic acids. The mechanisms involved are either dissolving rock material directly or chelating Ca and silicon (Si) ions to bring P and K into solution (Adeleke et al., 2017; Maity et al., 2019). The exploitation of such microorganisms including P and K solubilizing microorganisms as bio-fertilizer was found as a promising and sustainable option to ameliorate nutrition, root and plant growth, plant competitiveness, and responses to external stress factors (Maity et al., 2014; Basak et al., 2022). Phosphate solubilizing microbes have been exploited to enhance the usefulness of rock phosphate as they transform insoluble rock P into a soluble form, available for plant growth through acidification, chelation, and exchange reaction (Bhattacharya et al., 2015; Alori et al., 2017). Bacillus megaterium var. phosphaticum is familiar for its ability to solubilize rock P material (Ribeiro et al., 2020). In addition, it can also promote root development and enhances the rate of water and nutrient uptake (Kang et al., 2014; Ribeiro et al., 2020). Microbes such as Bacillus mucilaginosus (Basak et al., 2017), Aspergillus fumigates (Xiao et al., 2012) and A. niger (Wang et al., 2015) can advance mineral weathering and the deliverance of nutrients such as K and Ca from feldspar. It was manifested that potassium-solubilizing microbe such as B. mucilaginosus enhanced K availability in soils and its content in a plant (Basak and Biswas, 2009; Hamid and Bashir, 2019). Liu et al. (2006) explored that the polysaccharides produced from potassium solubilizing microorganisms strongly adsorbed the organic acids and got adhered to the mineral surface, creating an area of high concentration of organic acids close to the mineral surface. This affected the equilibrium between the mineral and liquid phases and led to a forward reaction towards SiO2 and K+ solubilization.

The stimulating effect of rock minerals on solubilization of insoluble K was demonstrated in our earlier study (Maity et al., 2019) where co-inoculation of P. pinophilum based potassium solubilizing bio-formulation with potassium feldspar resulted in higher fruit yield with improvement in fruit quality owing to greater increase in the availability of P and K nutrients in soil than only use of potassium solubilizing bio-formulation. Han and Lee (2005) also showed that inoculation of B. megaterium (PSB) and B. mucilaginosus (KSB) in combination with P and K containing rock material increased the availability of P and K in soil and promoted nitrogen (N), P, and K uptake, and growth of eggplant (Solanum melongena L). So, an integrated application of rock P and K materials with solubilizing microorganisms might give rise to a faster and uninterrupted supply of P and K for better plant growth (Abou-el-Seoud and Abdel-Megeed, 2012). The hypothesis of the study was to develop minerals and solubilizing microbe combination called bio-mineral fertilizer, which may be beneficial for both the plant and the environment and can be also easily acceptable by the farmers. However, such bio-mineral fertilizer comprising of low-grade P and K bearing minerals and P and K solubilizing microorganism Penicillium pinophilum has yet not been developed and studied as plant fertilization. Therefore, the aims of the present research were to investigate (1) whether this bio-mineral fertilizer with only nitrogenous chemical fertilizer would produce fruit yield and quality of pomegranate equivalent to those obtained in full a dose of N, P, and K chemical fertilizers application, (2) how the soil fertility responds to these fertilization regimes.

Section snippets

Collection of minerals and microbial strain

The fungal strain Penicillium pinophilum (NFCCI 2498 later on known as MCC0114) was isolated from the rhizosphere soil of pomegranate orchard in a semi-arid ecosystem. It was characterized earlier at genus and species level based on morphology and molecular studies (Maity et al., 2014). The same fungal strain was used in the present study. Low-grade rock phosphate was collected from Rajasthan State Mines and Minerals Ltd, Udaipur, Rajasthan, India. The powder rock phosphate (100 mesh) contained

Soil available nutrient status

The available nutrients indicate the amount of soil nutrients that can be available to the plant for uptake and utilization throughout its life cycle. Here, soil available nutrient content was assessed at 60 days after flowering (DAF) which reflect the soil nutrient supply during the fruit growth period. The results showed that the application of bio-mineral fertilizer notably enhanced available N, P, and K content in the soil (Table 3). The highest available N content was recorded with the

Discussion

The majority of the phosphorus and potassium in soil exists in the form of insoluble minerals either inherited from rock-forming parent materials or secondary reaction products resulting from fertilizer application. These nutrients become available to the trees upon weathering or solubilization over a period of time. However, this is a very slow process. The process of weathering gets accelerated with the involvement of micro-organisms. In the current study, the P and K solubilizing

Conclusion

It can be inferred from the present study that the application of Penicillium pinophilum MCC0114 enriched bio-mineral fertilizer at the rate of 150 g tree−1 could substantially improve soil fertility (available N, P, and K), rhizospheric microbial environment and trees’ nutritional status (P, K, Mg, and S) and thereby increased fruit yield to considerable extent with perceptible improvement in fruit quality attributes viz. aril percent, 100 arils test weight, juice acidity, ascorbic acid, total

Credit authors statements

AM was involved in planning, actual experimentation and data acquisition, RAM in monitoring experiment and interpretation of results, AS in statistical analysis of data and BBB in manuscript preparation and editing.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

CRediT authorship contribution statement

Ashis Maity: Conceptualization, Investigation, Data curation, Writing – original draft. Rajiv A. Marathe: Project administration, Supervision, Validation. Ananta Sarkar: Formal analysis, Methodology. B.B. Basak: Visualization, Writing – review & editing.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

The corresponding author is thankful to Indian Council of Agricultural Research (ICAR) for providing financial support, and the Director, ICAR-National Research Centre on Pomegranate, Solapur for facilities and encouragement in experimenting.

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