Journal of Environmental and Agricultural Sciences (JEAS). Ahmed et al., 2019. Volume 19: 29-36
Open Access – Research Article
Dissolution Kinetics of Phosphorus, Released from Rock Phosphate as Affected by Applied Farm Manure: An Incubation Study
Imtiaz Ahmed1,2,3*, Muhammad Ashraf2,4, Muhammad Sarfraz5, Hira Nawaz1, Adeel Ahmad1,
Imran Shehzad1, Arfa Touqeer5, Muhammad Mazhar Iqbal2,6, Tayyaba Naz1, Muhammad Afzal7,
Ghulam Sarwar2, Ijaz Rasool Noorka8, Mazhar Iqbal Zafar9, Muhammad Imtiaz10, Sabir Hussain11
1Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad, Pakistan
2Department of Soil and Environmental Sciences, University College of Agriculture, University of Sargodha, Sargodha, Pakistan
3Soil Salinity Research Institute, Pindi Bhattian, Pakistan
4Department of Soil Sciences, Bahauddin Zakariya University Multan, Pakistan
5College of Horticulture, Fujian Agriculture and Forestry University, Fuzhou, China
6Soil and Water Testing Laboratory, Chiniot, Department of Agriculture, Government of Punjab, Pakistan
7Department of Agricultural Entomology, University of Sargodha, Sargodha, Pakistan
8Department of Plant Breeding and Genetics, University of Sargodha, Sargodha, Pakistan
9Department of Environmental Sciences, Quaid-i-Azam Univeristy Islamabad, Pakistan
10Environmental Biotechnology Division, National Institute for Biotechnology and Genetic Engineering (NIBGE), Faisalabad, Pakistan
11Department of Environmental Science and Engineering, Government College University. Faisalabad, Pakistan
Abstract: Phosphorus (P) plays very crucial role in many plant physiological processes, including photosynthesis, respiration, energy storage and cell division. In Pakistan about 90% soils are deficient in available P. Application of expensis phosphatic fertilizers forced farmers to search alternate P sources including rock phosphate (RP). Howver, it is crucial to improve the solubility of rock phosphate. In this regard, an incubation experiment was conducted to determine P solubilized from rock phosphate through farm manure (FM) application. The treatments were set in completely randomized design alongwith five replications each. The 10 kg soil per pot was filled. The treatments were: T1 = Control, T2 = RP at 5g kg-1 soil, T3 = RP at 10g kg-1 soil, T4 = RP at 5g kg-1 soil + 5% FM, T5 = RP at 5g kg-1 soil +10% FM, T6 = RP at 5g kg-1 soil + 20% FM, T7 = RP at 10 g kg-1 soil + 5% FM, T8 = RP at 10g kg-1 soil + 10% FM, T9 = RP at 10g kg-1 soil + 20% FM. Water was applied according to need on day to day basis following field capacity. Soil samples were collected after every 15 days interval. Soil pH, ECe, organic matter, available P and potassium (K) were determined. Results showed a gradual increase in available P, K and OM with increasing rate of RP and FM, from T1 (i.e., Control) to T9 (i.e., RP at 10g kg-1 soil + 20% FM). However, soil pH showed non-significant variations. Soil EC was found variable among all the treatments. Overall results indicated that maximum solubilization of P from RP was observed under T9 where RP at 10g kg-1 soil + 20% FM was applied. Present results need further confirmation, especially under field conditions and economic feasibility must be worked out.
Keywords: Phosphorus, rock phosphate, farm manure, solubilization, pH, EC.
*Corresponding author: Imtiaz Ahmed: imtiazahmad235@gmail.com ________________________________________________________________________________________________
Dissolution Kinetics of Phosphorus, Phosphorus solubilization, Rock phosphate fertilizer, effect of farm manure on rock phosphate solubility, improving phosphorus availability in calcareous soils
Cite this article as: Ahmed, I., M. Sarfraz, H. Nawaz, A. Ahmad, I. Shehzad, A. Touqeer, M.M. Iqbal, T. Naz, M. Afzal, I.R. Noorka, M.I. Zafar, M. Imtiaz and S. Hussain. 2019. Dissolution kinetics of phosphorus released from rock phosphate as affected by applied farm manure: An incubation study. Journal of Environmental & Agricultural Sciences. 19: 29-36. [View Full-Text] [Citations] 
Dissolution Kinetics of Phosphorus, Phosphorus solubilization, Rock phosphate fertilizer, effect of farm manure on rock phosphate solubility, improving phosphorus availability in calcareous soils
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Copyright © Ahmed et al., 2019. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium provided the original author and source are appropriately cited and credited.
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Key Findings
- The treatment containing 10 g rock phosphate per kg soil combined with 20% farm manure (T9) produced the greatest reported phosphorus solubilization during the incubation experiment.
- Available phosphorus and potassium increased with increasing rates of rock phosphate and farm manure, with the highest values reported under T9.
- Higher farm manure application rates were associated with increased soil organic matter during the incubation period.
- Soil pH showed no statistically significant treatment differences, whereas electrical conductivity varied across treatments and increased under some manure–rock phosphate combinations.
-
The findings support further investigation of rock phosphate combined with farm manure, but field performance and economic feasibility remain to be established.
Dissolution Kinetics of Phosphorus, Phosphorus solubilization, Rock phosphate fertilizer, effect of farm manure on rock phosphate solubility, improving phosphorus availability in calcareous soils
1. Introduction
Phosphorus is an essential plant nutrient and involved in metabolism. It is vital for transfer of energy from source (photosynthetic sites) and its storage in sink (Jiang et al., 2019; Zhang et al., 2018). Moreover, it is involved in the metabolism of carbohydrates and structural part of the nucleic acids, phosphoproteins, phospholipids and many coenzymes (Amin et al., 2017; Bi et al., 2013; Garba et al., 2017; Lambers and Plaxton, 2018).
Plants utilize phosphorous in three different water soluble forms like H2PO4–, HPO4– and PO4– (Mamathashree et al., 2018). Roots of plants secretes different organic acids like malic and citric acid which solubilize phosphates present in soil (Chen and Liao, 2016; Jones, 1998; Sasse et al., 2018; Wang and Lambers, 2019). Phosphate reaction in soil is very slow that leads to decline in the concentration of phosphate in soil solution. Thus, the retrieval of P manure by plants amount to be only to 10-30 % of that added (Ringeval et al., 2017; Tisdale et al., 1985; Tammimi et al., 1986). Phosphorus usually exists in Pakistani soil as insoluble complexes of calcium like di and tri-calcium phosphates. Breakdown of organic matter increase the carbon dioxide level that rise the carbonic acid which help in solubilize intrinsic P mineral and enhance P mobility in soil (Marschner, 1995; Mengel and Kirkby, 2001).
Soil surveys of Pakistani soils reported alkaline and calcareous nature and nationwide phosphorus deficiency with very low phosphorus availability (Ali and Ali 2011; Memon and Rashid 2001). Clay dominated arid soils can fix P and reduces its availability to plants. Consequently, higher rates of phosphorus fertilizers are required to meet plant phosphorus requirement (Dzotsi et al. 2010). Lower phosphorus recovery (15–25% of the amount of fertilizer applied) in irrigated areas further reduces in arid areas, which requires higher amount of fertilizer application (Chattha et al. 2007; Nasim et al., 2017).
High cost of inorganic fertilizer and environmental concerns forcing farmers to consider alternate sources to maintain fertility of their soils (Mafongoya et al., 2000). Rock phosphate (RP) referred to as sedimentary rock contain about 15-20 % P but not completely accessible to plants (Blatt et al., 1996). The RP symbolize cheap preference as a plant fertilizer, mostly in those areas where raw material is not available for production of phosphate fertilizers (Haynes, 1984). Rock phosphate is mainly tri-calcium phosphate with un-available P to plants and RP is basically major raw material for preparation of phosphate fertilizers by reacting with sulfuric acid (Das, 2005).
Variety of organic materials are incorporated into the soil as a source of nutrient and for improving soil quality such as manure, sewage sludge, crop residues, compost and municipal waste are being (Rasmussen and Collins, 1991; Six et al., 2002). Farm waste is a cheap alternative for soil enrichmenmt and improvement of nutrient availability (Ahmad et al., 2016; Benbi and Yadav, 2015). After decomposition of manure organically–bound nutrients are released (Mafongoya et al., 2000). In addition to nutrient supply, manures add humus into the soil, which enhances the aggregate stability, aeration and water retention of soil (Aarons et al., 2004).
Using RP with organic manures appeared as worthwhile option due to production of various organic acids throughout the process of decomposition by both microbial and chemical reactions (Rashid et al., 2004). Rock phosphate when used along with manure sustain greater amount of P in soil for longer time period in comparison to using fertilizer alone (Sah et al., 1986). Rock phosphate with combination of organic manure fulfills the nutrient demand of plants in a cropping pattern (Khalil et al., 2002).
When high grade phosphate fertilizer applied with FM or other organic manure it behave like a very active phosphate fertilizer. Soil phosphate solubility enhance the organic matter. Decomposition of organic acids release humic acids that facilitate to change unavailable phosphate into available form (Brady, 1984). Composting of organic manure with RP enhances the availability of P from RP and this is accomplished as effective technology to enhance the fertilizers worth of manures (Mishra and Bangar, 1986; Singh and Amberger, 1991; Mahimairaja et al., 1995). The FM application leads to accumulation of P and also speed up dissolving native P by discharge of weak organic acids (Kiss et al., 1994). Along with FM, green and poultry manure also identified to increases P availability in alkaline soil (Singh and Bahl, 1993; Toor and Bahl, 1997). Mixing phosphate minerals with organic manure or compost increase the soil P availability because acids release from breakdown of organic matter will help in dissolution of phosphate minerals (Moore and Miller, 1984). Thus, an experiment was designed to check the solubilization of P from RP using FM with objectives as (1) to check the effect of FM on P release from RP in an incubation study (2) to investigate the combined effect of RP and FM on pH and EC of the soil.
2. Materials and Methods
An incubation study was conducted in the Agricultural Research Farm Area, University of Sargodha, Sargodha, Pakistan, to investigate the solubilization of P from RP from applied FM. An incubation study was conducted following completely randomized design (CRD). A 10 kg soil was filled in each pot. Experiment consisted of nine treatments each with five replications using rock phosphate (RP) and farm manure (FM) as: T1 = Control, T2 = RP at 5 g kg-1 soil, T3 = RP at 10 g kg-1 soil, T4 = RP at 5 g kg-1 soil + 5 % FM, T5 = RP at 5 g kg-1 soil + 10 % FM, T6 = RP at 5 g kg-1 soil + 20 % FM, T7 = RP at 10 g kg-1 soil + 5 % FM, T8 = RP at 10 g kg-1 soil + 10 % FM, T9 = RP at 10 g kg-1 soil + 20 % FM.
Before pot filling the soil was analyzed for different chemical parameters (such as pH, EC, organic matter i.e., OM, available P, available K), following Iqbal et al. (2017), which are presented in Table 1. Then, RP and FM were mixed in the soil according to the treatment plan, leaving one treatment as control pots. Distilled water was applied according to requirement as per field capacity. Soil samples were collected after every 15 days and analyzed for pH, EC, OM, P and K.
Samples were air dried, passed through 2 mm sieve and analyzed for electrical conductivity (EC) by preparing 1:10 soil and water suspension (Soil Salinity Lab Staff 1954), pH (Schofield and Taylor, 1955), organic matter (Walkley and Black, 1934), available phosphorus (Olsen et al., 1954) and extractable potassium (Jackson, 1967).
The present experiment was lasted for 120 days during this period various agronomic practices were accomplished according to the requirement of soil. The collected data was analyzed statistically (Steel et al., 1997) at 5% level of significance by means of “Statistix 8.1” statistical computer-based software package.
3. Results and Discussion
Data regarding EC and pH was presented in Table 2 and 3 respectively. It was observed that addition of RP along with FM improved the P and K concentration in soil as released from RP, resultantly EC of soil also increased. There was no noteworthy consequence of using varying concentrations of RP alone like in first and second treatment but when RP was used in combination with FM, it enhanced the EC and this rise in EC level was maximum when used 20% FM along with 5 and 10 g RP per kg soil. The Table 3 representing the data for pH and no considerable outcome of any treatment on pH; however, the pH had reduced by FM. The pH of present control treatment was 8.5 and this pH level had started to decrease using different treatments but difference between the treatments was not significant.
The present EC and pH results are consistent with the finding of Akram (1978) who investigated that soil pH decreased because of the discharge of H+ ions through mineralization of organic and inorganic compounds. Addition of organic fertilizers released H+ ions from the soil during nitrification process which decreased the soil pH. A few studies reported that applied farm manure not changes the soil EC and pH.
However, EC under rhizosphere soil was very low than bulk soil (Marschner, 1995). Walker et al. (2004) suggested that application of organic manure changed the soil pH due to oxidation of organic matter and process of releasing carbon dioxide from the soil. Nevertheless, this inconsistency might be due to short small duration of present study. Agbede et al. (2008) suggested non- significant effect of manure on soil pH. Appliance of RP along-with organic materials slightly decline the soil pH because of discharge of H+ ions during nitrification of fertilizers (Mbakaya et al., 2006).
Significant variations was observed regarding soil available P and K, which are described in Tables 4 and 5. The present outcome are in consistence with (Laskar et al., 1990) that suggested that addition of RP with or without organic manures appreciably increase the total organic P level in soil. Soil without any treatment have P content 3.6 mg kg-1 but when RP was added along with FM soil P level had raised to higher level and maximum soil available P was measured when added 20 % FM .
Similar trend was noted for soil available K. Soil available P reached to maximum level as each sample is taken after every 15 days and all treatment means differ significantly (p≤0.05). Cavigelli and Thien (2003) also noted the increase in bioavailability of P in soil due to adding of organic manure. There was noteworthy rise in soil available P and K owing to application of organic manure in soil. Sharma and Tripathi (1999) described that efficacy of FM in rising soil available P is linked to its role in chelating phosphate fixing cations and reducing sorption of phosphate with low binding energy and exchange of adsorbed phosphate by organic anions. Use of FM enhances soil water content that are might be possible because of increase in the soil available P or decomposition of organic manures that increases carbonic acid that enhance P bioavailability (Marschner, 1995; Boateng et al., 2006; Mengel and Kirkby, 2001).
Organic matter under different treatment and during variable time period was encountered in Table 6 showing that all treatments varies significantly instead of treatment 5 and 8 during all harvesting period except of 1st and 2nd harvest. Maximum organic matter was observed under higher concentration of FM. Rabindra and Gowda (1986) reported that use of manures in good amalgamation increase the organic matter of soil while Marschner (1995) reported that organic manure increase soil microbial activity which play role to enhance soil organic matter. Furthermore, our results are supported by Tomayo et al. (1997) as they concluded that during the addition of organic manures composted with RP a significant progress was observed in soil organic matter content. However, Iqbal et al. (2016) reported that higher rates of applied FM led to increase OM in different textured both salt-affected Pb-contaminated soils than the initial or lower rates of FM application. Moreover, the decomposition of added FM decreased OM along with ABDTPA extractable Pb, after each incubation time.
4. Conclusion
Rock phosphate is an important locally available source of P but constraint withstand is with its solubility and phyto-availability. However, organic matter applied with rock phosphate can enhance its solubility. The present results proved that applied rock phosphate along with farm manure not only increased the concentration of available phosphorous in the soil but also improved the soil health, as pH of soil was found to be reduced. The combination of rock phosphate and farm manure at its higher applied rate also enhanced the concentration of available potassium, however, the electric conductivity of soil was also increased. Overall the combination was proved beneficial in the present study. However, further study and present results are needed to be checked regarding their effect in a cropped field.
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Dissolution Kinetics of Phosphorus, Phosphorus solubilization, Rock phosphate fertilizer, effect of farm manure on rock phosphate solubility, improving phosphorus availability in calcareous soils
List of Abbreviations: CRD, completely randomized design; EC, electrical conductivity; FM, farm manure; K, potassium; NPK, nitrogen phosphorus, potassium; OM, organic matter; P, Phosphorus; RP, rock phosphate.
Competing Interest Statement: All the authors declare that they have no potential competing interest.
Author’s Contribution: I.A. conducted the whole research and did all the work of research article. M.A. and M.S. commenced the idea of research, intended and described the treatments. H.N. and I.S. assisted in experimentation and analytical work. A.A. and A.T. statistically analyzed the results. M.M.I. and T.N. provided technical inputs for interpretation of discussion. G.S., M.A. and I.R.N. assessed and supervised throughout the research with useful suggestions. M.I.Z., M.I. and S.H. the evaluated the results and revised manuscript. All others approved final draft of the manuscript.
Acknowledgments: The authors acknowledge the support of technical staff at the Soil and Water Testing Laboratory, Chiniot, Pakistan, in conducting different analyses.
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Dissolution Kinetics of Phosphorus, Phosphorus solubilization, Rock phosphate fertilizer, effect of farm manure on rock phosphate solubility, improving phosphorus availability in calcareous soils
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Frequently Asked Questions
What is rock phosphate, and why is it used in agriculture?
Rock phosphate (RP) is a naturally occurring phosphate mineral and an important raw material for manufacturing phosphorus fertilizers. It is also a potentially economical source of phosphorus for agriculture, with phosphorus content varying according to its mineral composition and grade. However, its direct use as a fertilizer is often limited by the low solubility of its phosphorus-bearing minerals, particularly in alkaline and calcareous soils, where phosphorus release may be slow.
The dissolution and agronomic effectiveness of rock phosphate depend on its mineralogical composition, chemical reactivity, soil pH, and other soil properties. Availability of phosphorus from rock phosphate can be enhanced through physical, chemical, or biological treatments and by processes that promote mineral dissolution, such as organic acid production and microbial activity. Organic amendments, including farm manure, may also facilitate phosphorus release during decomposition and improve soil nutrient availability. Therefore, combining rock phosphate with farm manure may offer a promising approach to phosphorus management, although its effectiveness depends on soil conditions and requires appropriate evaluation.
How does farmyard manure affect phosphorus availability in soil?
Farmyard manure supplies organic matter and nutrients. During decomposition, organic compounds and microbial processes can influence phosphorus release, mineral dissolution, and phosphorus retention in soil. The magnitude of the effect depends on manure characteristics and soil conditions.
Can rock phosphate and farmyard manure replace conventional phosphorus fertilizers?
Not necessarily. Their effectiveness depends on soil properties, crop nutrient requirements, rock phosphate reactivity, and the rate of phosphorus release. Field trials and economic comparisons are needed before recommending them as complete replacements for soluble phosphorus fertilizers.
Does increased soil phosphorus availability guarantee higher crop yield?
Perhaps not. Higher measured soil phosphorus availability may not automatically translate into greater crop uptake or yield. Crop response also depends on interactions of plant, soil, and environmental factors, like root activity, soil moisture, other nutrients, crop species, and environmental conditions. Field experiments are needed to establish agronomic benefits.
Dissolution Kinetics of Phosphorus, Phosphorus solubilization, Rock phosphate fertilizer, effect of farm manure on rock phosphate solubility, improving phosphorus availability in calcareous soils