Interactive effect of organic and mineral phosphorus on volatile compounds, morphology, and physiology of garlic (Allium sativum L.)

1 Introduction

Assumed to be the second most significant crop producing bulbs, after onions, garlic (Allium sativum L.), which is a member of the Lilliaceae family (Tindal 1986, Ledezma and Apitz-Castro 2006), is grown worldwide (Kim et al., 2004, Hamma 2013). In addition to its use as a seasoning in the production of food for humans, it contains extraordinary medical capabilities as well as properties that are particular to the human body's capacity for strength (Etoh and Simon 2002). Garlic production in the world exceeds 22.23 million tons, and among the continents, Asia contributes >80 % towards its total production. China leads in garlic production (18.56 million tons) which is ∼77 % of world garlic production followed by India, Pakistan, South Korea, Egypt, Russia, Myanmar, Ethiopia, the USA, Bangladesh and Ukraine (Khodadadi and Nosrati 2012). A 100 g edible garlic portion contains protein 6.4 g, fat 0.5 g, carbohydrates 33.1 g, calcium 181 g, sodium 17 mg and vitamin C 10. 8 mg (Lorenz and Maynard 1988, Corzo-Martínez et al., 2007). When fried with meat, eggs, and other vegetables, garlic leaves are eaten as a vegetable. In addition to their fresh use, cloves are kept and ground to replace fresh garlic (Amagase 2006). Garlic's sulfur, alliin, and allicin constituents are what give food intended for human consumption its taste. Garlic's alliin content lowers blood sugar and blood pressure, and its special ability to relax vascular smooth muscles prevents hypoxia from increasing under situations of pulmonary pressure (Fallon et al., 1998; Chandrashekara and Venkatesh 2016). Additionally, garlic is a natural remedy for conditions such as diabetes, high blood pressure, cancer, and obesity, and its pungent green tips and bulb are good for flavoring meals (Farooqui et al., 2009).

The soil nutritional balance is essential for successful crop production, and nutritional imbalance may adversely affect crop yields (Frossard et al., 2000). In addition to nitrogen, phosphorus (P) is a nutrient that is necessary for the expansion and development of plants. Additionally, it plays a part in absorbing the energy of the sun and transforming it into molecules that are beneficial to plants (Griffith 2010). The changes of phosphorus and its mobility within the soil–plant system are governed by a confluence of biological, chemical, and physical processes (Frossard et al., 2000, Zaidi et al., 2009). However, overall P-use efficiency of applied P-fertilizers is lower than optimal and only 15–20 % of applied P is recovered by the first crop (Vance 2001). Therefore, addition of sufficient P through organic sources is direly needed. Phosphorus is applied in various forms, including DAP, NP, SSP, rock phosphate and phosphor compost etc. (Memon et al., 2012), while P application through farmyard manure (FYM) is one of the most effective source that helps to improve soil organic matter sustainably (Sharif et al., 2000, Singh and Singh 2005). The fertility of the soil may be maintained for an extended period with the use of organic fertilizers. On the other hand, farmers seldom replace the organic matter that is removed from the soil at a rate that is sufficient to offset the loss. Because of this, it is imperative that research be conducted into the potential applications of the many indigenous sources of plant nourishment that are now under development, such as organic and bio fertilizers.

When it comes to the management of soil and nutrients, the primary goals of organic farming are to conserve and maintain soil fertility via the development of biological activity, nitrogen self-sufficiency, and crop variety, and to limit effects on the ecosystem as a whole (Stockdale et al., 2002). There is a wide variety of organic farming methods, each of which takes a unique philosophical and operational approach to the management of soil, plants, and animals (Stockdale et al., 2002). The use of manures resulted in a 12 % increase in the harvest, with the manure from chicken coops proving to be the most beneficial (Mahavishnan et al., 2006). In a similar vein, the soils have depleted their supply of accessible phosphorus, and if an appropriate supply of phosphorus is not added to the soil, it will not be possible to achieve the levels of garlic production that are required. Therefore, by using organic P, it is possible to increase the yields of garlic. The application of FYM at a rate corresponding to the needed amount of P may, however, result in a sustained yield boost owing to an improvement in soil organic matter. Inadequate quantities of phosphorus cause a decrease in crop yields in bulbous crops. This is due to the fact that higher quantities of phosphorus are required for the development of healthy bulblets and bulbs, as well as the development of root areas and leaf areas, and as a result, desired bulb yields. On sandy loam soil, the application of phosphorus has demonstrated a high reaction, leading to improved bulb yields in garlic. Due to the fact that phosphorus plays a significant part in root expansion, it is constantly moving through the soil, and its absorption is connected with soil diffusion near the roots and concentration gradients (Robertson and McPharlin 1999). Significant changes in the growth characteristics of garlic were seen when organic manures were used in conjunction with lower application rates of inorganic fertilizer.

The sulfides and thiosulfinates found in Allium plants have antibacterial capabilities against different bacteria and fungi. The volatile chemicals found in Allium plants are discovered by GC–MS and HPLC studies (Yolcu 2011). Disulfides were found to be the main sulfur compounds in leaf extracts containing allicin, which highlighted the possibility of using fresh Allium leaves as a condiment and preservative in the food business. The high culinary and medicinal value of plants in Allium genus contain several phytochemicals that signifies its importance in the discovery of new drugs for treatment of cancer (Alizadeh et al., 2013), hepatic disorders, and impotency (Seo et al., 2001). Several organic sulphur compounds in Allium species have preventive roles in development of human cancer, cardiovascular diseases and inflammatory diseases (Chandrashekara and Venkatesh 2016). Allium plant extract improves antioxidant enzyme activity of diabetic patients (Ledezma and Apitz-Castro 2006), reduces area of renal pathogenic damage induced by adenine and decreases serum level creatinine and blood urea nitrogen (Bede and Zaixiang).

This study investigated the interactive effect of organic and mineral P-sources on morphological and physiological variation in garlic. The variation associated with the volatile compounds due to various P-sources was also documented. It was hypothesized that combined application of organic and mineral P would improve the morphological, physiological, and biochemical attributes of garlic compared with sole application of mineral P.

2 Materials and methods

3 Results

3.2

3.2 Physiological indices

Leaf area was significantly affected (P < 0.05) by mP–oP integration, and it was higher (83.83 and 83.33 cm) when applied T₇ and T₄, followed by application of mP 70 kg + oP ≈ 60 kg P and mP 90 kg + oP ≈ 30 kg P ha⁻¹; with 82.10 and 75.50 cm leaf area, respectively. Fresh leaf weight was highest (2.70 g) when treated with mP 50 kg + oP ≈ 90 kg P ha⁻¹; closely followed by 2.52 g and 2.50 g in mP 90 kg + oP ≈ 30 kg P and mP 70 kg + oP ≈ 60 kg P ha⁻¹, respectively. Similarly, leaf dry weight was higher (0.49 g) in mP 70 kg + oP ≈ 60 kg P ha⁻¹, followed by 0.45, 0.45 and 0.43 g in plots given mP 50 kg + oP ≈ 90 kg P, mP 50 kg + oP ≈ 50 kg P and mP 90 kg + oP ≈ 30 kg P ha⁻¹, respectively. Moreover, highest leaf chlorophyll content (11.9 %) was determined in plots given mP 50 kg + oP ≈ 90 kg P ha⁻¹, while 11.60, 11.37 and 10.83 % leaf chlorophyll contents were determined in plants given mP 70 kg + oP ≈ 60 kg P, mP 90 kg + oP ≈ 30 kg P ha⁻¹ and mP 50 kg + oP ≈ 50 kg P ha⁻¹, respectively (Table 3). There was a linear decrease in leaf chlorophyll (10.39, 10.30 and 9.58 %) organic P (oP) was skipped.

Table 3 Leaf area, fresh/dry leaf weight and chlorophyll content of garlic as affected by organic P (oP) and mineral P (mP) integration.

Sr#	Treatments	Leaf area (cm/plant)	Fresh leaf weight (g)	Dry leaf weight (g)
T0	Control (untreated)	50.21e	1.32d	0.23d
T1	P50 kg ha-1as SSP	53.88e	1.59 cd	0.43c
T2	P70 kg ha-1as SSP	61.97d	1.65c	0.33c
T3	P90 kg ha-1as SSP	70.38c	1.86c	0.35c
T4	P50 kg ha−1 as SSP + FYM≈50kgP	83.33a	2.22b	0.45b
T5	P 70 kg ha−1 as SSP + FYM≈60kgP	82.10ab	2.50ab	0.49a
T6	P 90 kg ha−1 as SSP + FYM≈30kgP	75.50bc	2.52a	0.43b
T7	P 50 kg ha−1 as SSP + FYM≈90kgP	83.83a	2.70a	0.45b
	S.E.±	3.3608	0.1356	0.0194
	LSD 0.05	7.2081	0.2909	0.0416

A significant variation (p < 0.05) in VC content was recorded and highest (6.43 %) value was determined in plants fertilized with mP 50 kg + oP ≈ 90 kg P ha⁻¹; while 6.16, 6.07 and 5.72 % VC was determined in treatments mP 70 kg + oP ≈ 60 kg P, mP 50 kg + oP ≈ 50 kg P and mP 50 kg P ha⁻¹, respectively. The leaf extract pH was highest (6.17) in plants treated with mP 50 kg + oP ≈ 90 kg P ha⁻¹; while it decreased to 6.15, 6.15, 6.14, 6.13 and 6.12 in treatments mP 90 kg + oP ≈ 30 kg P, mP 90 kg P, mP 50 kg ha⁻¹, mP 70 kg + oP ≈ 60 kg P ha⁻¹ and mP 50 kg + oP ≈ 50 kg P ha⁻¹, respectively (Table 4).

Table 4 Chlorophyll content, extract pH and vitamin C in garlic as affected by organic P (oP) and mineral P (mP) integration.

Sr#	Treatments	Chlorophyll content (%)	Extract pH	Vit-C content (%)
T0	Control (untreated)	6.29d	5.16b	3.75c
T1	P50 kg ha-1as SSP	9.58c	6.14a	5.72ab
T2	P70 kg ha-1as SSP	10.30bc	6.07a	5.10abc
T3	P90 kg ha-1as SSP	10.39abc	6.15a	4.56bc
T4	P50 kg ha−1 as SSP + FYM≈50kgP	10.83abc	6.12a	6.07ab
T5	P 70 kg ha−1 as SSP + FYM≈60kgP	11.60ab	6.13a	6.16a
T6	P 90 kg ha−1 as SSP + FYM≈30kgP	11.37ab	6.15a	5.36ab
T7	P 50 kg ha−1 as SSP + FYM≈90kgP	11.90a	6.17a	6.43a
	S.E.±	0.7171	0.0800	0.7185
	LSD 0.05	1.5381	0.1717	1.5410

The characterization of sulfur-containing compounds in plants treated P 50 kg ha⁻¹ as SSP + FYM≈90 kg P (T₇) by GC–MS and HPLC analyses detected enormously higher count of constituents in garlic which include Aldehydes(3.254 µg/g), Hydrocarbons (1.245 µg/g), Esters (0.547 µg/g), Acids (1.658 µg/g), Sulfides (4.985 µg/g), Ketones (1.254 µg/g), Ethers (8.888 µg/g), Alkaloids (0.357 µg/g), Heterocyclic polymers (2.684 µg/g), Cyclomethicone (1.854 µg/g), Polyolefins (0.214 µg/g), Furfuryl & furan derivatives (0.987 µg/g), Phenols (0.666 µg/g) and Diterpenes (1.256 µg/g) (Figs. 1-4). The results proved that farmyard manure application improved the soil organic matter; hence the volatile composition increased tremendously.

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Fig. 1

The impact of different forms of phosphorus on aldehydes, hydrocarbons, esters and acids in garlic leaves. Here, T₀ = control, T₁ = 50 kg ha⁻¹ mP, T₂ = 70 kg ha⁻¹ mP, T₃ = 90 kg ha⁻¹ mP, T₄ = 50 kg ha⁻¹ mP + oP ≈ 50 kg ha⁻¹, T₅ = 70 kg ha⁻¹ mP + oP ≈ 60 kg ha⁻¹, T₆ = 90 kg ha⁻¹ mP + oP ≈ 30 kg ha⁻¹, and T₇ = 50 kg ha⁻¹ mP + oP ≈ 90 kg ha⁻¹.

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Fig. 2

The impact of different forms of phosphorus on sulfides, ketones, ethers, and alkaloids in garlic leaves. Here, T₀ = control, T₁ = 50 kg ha⁻¹ mP, T₂ = 70 kg ha⁻¹ mP, T₃ = 90 kg ha⁻¹ mP, T₄ = 50 kg ha⁻¹ mP + oP ≈ 50 kg ha⁻¹, T₅ = 70 kg ha⁻¹ mP + oP ≈ 60 kg ha⁻¹, T₆ = 90 kg ha⁻¹ mP + oP ≈ 30 kg ha⁻¹, and T₇ = 50 kg ha⁻¹ mP + oP ≈ 90 kg ha⁻¹.

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Fig. 3

The impact of different forms of phosphorus on heterocyclic polymers, cyclomethicones, polyolefins, and furfuryl and furan in garlic. Here, T₀ = control, T₁ = 50 kg ha⁻¹ mP, T₂ = 70 kg ha⁻¹ mP, T₃ = 90 kg ha⁻¹ mP, T₄ = 50 kg ha⁻¹ mP + oP ≈ 50 kg ha⁻¹, T₅ = 70 kg ha⁻¹ mP + oP ≈ 60 kg ha⁻¹, T₆ = 90 kg ha⁻¹ mP + oP ≈ 30 kg ha⁻¹, and T₇ = 50 kg ha⁻¹ mP + oP ≈ 90 kg ha⁻¹.

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Fig. 4

The impact of different forms of phosphorus on phenols and diterpenes in garlic. Here, T₀ = control, T₁ = 50 kg ha⁻¹ mP, T₂ = 70 kg ha⁻¹ mP, T₃ = 90 kg ha⁻¹ mP, T₄ = 50 kg ha⁻¹ mP + oP ≈ 50 kg ha⁻¹, T₅ = 70 kg ha⁻¹ mP + oP ≈ 60 kg ha⁻¹, T₆ = 90 kg ha⁻¹ mP + oP ≈ 30 kg ha⁻¹, and T₇ = 50 kg ha⁻¹ mP + oP ≈ 90 kg ha⁻¹.

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4 Discussion

The integrated use of organic P (oP) and mineral P (mP) was more effective than their individual application and remarkable improvement in plant height with was observed. The mP 90 kg + oP ≈ 30 kg P ha⁻¹ proved to be an effective combination to maximize plant height. These findings are consistent with those of Reddy et al. (2000) and Sardi et al. (2005), who found that integrating FYM with mineral fertilizers led to significant increases in garlic plant height. The mineral and organic P combination relatively delayed seedling emergence, and mP without oP regardless of dose resulted in early germination and more leaves plant⁻¹. The combination also resulted in an increase in leaves number suggesting association of improvement with FYM addition. These results are consistent with those of Singh and Singh (2005) and Suthar (2009), who believed that the incorporation of FYM into an NPK fertilizer program resulted in enhanced foliage in garlic. Both of these researchers came to this conclusion after doing research on the subject. According to Chandrashekar et al. (2011), an increase in the combined application of P fertilizers and FYM led to an increase in the number of leaves on garlic plants. Leaves length was significantly higher (42.2 cm) in crop given mP 70 kg + oP ≈ 60 kg P ha⁻¹; this might be associated with improved soil organic matter due to addition of FYM. Akinyele et al. (2012) was of the experience that recommended P in addition to equivalent rate of FYM not only increased the leaves elongation, but the soil organic matter was also improved considerably.

An optimal nutrient balance in the soil is crucial for fruitful crop development, and a deficiency or excess in one area of soil's nutrients may have a negative effect on harvest results (Frossard et al., 2000). Phosphorus (P) is a nutrient that, like nitrogen (N), is important for a plant's growth and development. It also contributes to the process by which the sun's rays are converted into molecules that plants can use (Griffith 2010). A plethora of biological, chemical, and physical mechanisms drive the transformations of phosphorus and its mobility within the soil–plant system (Frossard et al., 2000, Zaidi et al., 2009). Nonetheless, the overall P-use efficiency of P-fertilizers is subpar, and only around 15–20 % of applied P is recovered in the first crop (Vance 2001). Therefore, it is crucial to supplement adequate P from organic sources. Farmyard manure (FYM) is one of the most effective sources that helps to sustainably build soil organic matter, among other P sources including DAP, NP, SSP, rock phosphate, and phosphor compost etc. (Memon et al., 2012; Sharif et al., 2000; Singh and Singh, 2005). By using organic fertilizers, soil fertility may be preserved for longer periods of time. But farmers seldom replenish the organic matter taken from the soil at a pace enough to balance the loss. This is why it is crucial to study the uses of the numerous newly developed organic and bio fertilizers and other indigenous sources of plant sustenance.

The bigger leaf area (83.83 cm), leaf fresh weight (2.70 g), leaf chlorophyll concentration (11.9 %), and vitamin C concentration (6.43 %). a crop treated with mP 50 kg + oP 90 kg P ha-1 was successful. The removal of FYM treatment had a detrimental influence on physiological features, but its reintroduction had a good impact on this trait. The application of phosphorus in mineral form with an equal quantity of FYM resulted in an increase in the leaf area of garlic, and with the addition of FYM, the leaves were broader than when MP was applied alone (Bhandari et al., 2012). Bhandari et al. (2012) discovered that the addition of FYM to the prescribed amount of mineral fertilizers boosted the leaf weight of garlic. Chandrashekar et al. (2011) and Moradi (2015) said that farmyard manures are an effective source of NPK fertilizers that appropriately balance the nutritional requirements of garlic and result in a greener leaf color owing to an increase in chlorophyll content. The results of Abbas et al. (2006) on the vitamin C content of garlic were comparable to those of the current research.

Among yield attributes, maximum bulb diameter (4.50 cm), bulb weight (42.66 g), cloves bulb⁻¹ (8.50) and bulb yields (4382.96 kg ha⁻¹) were achieved in crop fertilized with mP 50 kg + oP ≈ 90 kg P ha⁻¹, so the increase in bulb weight under mP – oP combination regardless of nutrient rate. Akinyele et al. (2012) and Adewale et al. (2011) found that using a mix of mineral fertilizers and manures led to greater improvements in bulb size and weight than using mineral fertilizers alone. Several studies, including those by Zakari et al. (2014), Moradi (2015), Nainwal et al. (2015), and Shafeek et al. (2015), found that combining the use of FYM with mineral P increased both bulb size and output. Bulblets per bulb increased when inorganic fertilizers were combined with farmyard manure at P values determined by Shafeek et al. (2015). The combination of mP and oP found to be the most successful in increasing yields, whereas oP was unnecessary and reduced bulb production even when administered at the recommended amount of mP. This shows that the use of FYM improved soil organic matter and hence improved soil fertility causing higher crop yields. This study's findings on bulb yield are consistent with those of many others (Reddy et al., 2000, Sardi et al., 2005, Singh and Singh 2005, Suthar 2009, Adewale et al., 2011, Akinyele et al., 2012, Bhandari et al., 2012, Zakari et al., 2014, Moradi 2015, Nainwal et al., 2015, Shafeek et al., 2015).

The treatment effect on volatiles detected through GC–MS and HPLC analysis showed that P 50 kg ha⁻¹ as SSP + FYM≈90 kg P resulted in higher volatile compounds in garlic including aldehydes, hydrocarbons, esters, acids, sulfides, ketones, ethers, alkaloids, heterocyclic polymers, cyclomethicone, polyolefins, furfuryl and furan derivatives, phenols and diterpenes. Our results reflected a linear development in the development of the compounds in garlic leaves and this increase in the compounds was proportional to the quantity of the farmyard manure application. The interaction between the effects of mineral and organic had a major impact not only on the morphological and physiological characteristics of the organism, but also on the contents of the volatile sulfur-containing compounds. The best bulb yields were obtained by garlic plants fertilized with T₇. The response of volatile sulfur-containing compounds in garlic leaves suggested that an enormously larger count of components in garlic leaves were determined in T₇. The total volatile contents of garlic leaves ranged from 29.849 g/g (T₇) to 7.306 g/g on average (control).

Inhibitory effects against several bacteria and fungus may be attributed to the sulfides and thiosulfinates present in Allium plants. Exploratory gas chromatography–mass spectrometry–high-performance liquid chromatography analyses of Allium plants reveal their volatile chemical components (Yolcu 2011). Results showed that disulfides were the primary sulfur compounds in allicin-containing leaf extracts, suggesting that fresh Allium leaves might be used as a condiment and preservative in the food industry. Plants of the Allium genus have several phytochemicals, indicating their potential usefulness in the development of novel medications for the treatment of cancer (Alizadeh et al., 2013), hepatic diseases, and impotence due to their great culinary and medical value (Seo et al., 2001). Allium species include a number of organic sulphur compounds that have been linked to a reduced risk of cancer, cardiovascular disease, and inflammation in humans (Chandrashekara and Venkatesh 2016). Improvements in antioxidant enzyme activity, decreased area of renal pathogenic damage generated by adenine, and lower serum levels of creatinine and blood urea nitrogen have been seen in diabetic patients who took allium plant extract (Ledezma and Apitz-Castro, 2006; Bede and Zaixiang).

It is noticeable that in absence of farmyard manure, the highest level of mineral P could not improve the volatile compounds, but higher rate of farmyard manure even under lower portion of mineral P recorded higher concentration of the volatile compounds in garlic leaves. P application through FYM is one of the most effective sources that helps to improve soil organic matter sustainably (Sharif et al., 2000). The soil's fertility may be maintained over the long term by the use of organic fertilizers. It has been stated (Singh and Singh, 2005) that farmers often don't replenish the soil with enough organic matter to compensate for the amount that is taken away. In this situation, it's important to investigate the potential for using the increasing number of indigenous sources of plant nourishment, such as organic and bio fertilizers. It's notable that even the greatest concentration of mineral P had no effect on the volatile compounds in garlic leaves without the addition of farmyard manure, whereas a greater rate of farmyard manure resulted in a larger concentration of volatile compounds despite a smaller percentage of mineral P. For optimal growth and flavor, garlic benefits from a combination of organic and mineral P.

5 Conclusions

The morphological and physiological traits as well as contents of the volatile sulfur containing compounds were significantly affected by the interactive effect of mineral and organic. The garlic plants fertilized with T₇ produced highest bulb yields, The response of volatile sulfur containing compounds in garlic leaves indicated that in T₇ enormously higher count of constituents in garlic leaves were determined. The total volatile contents in garlic leaves were in the range of 29.849 µg/g (T₇) and 7.306 µg/g (control). It is noticeable that in absence of farmyard manure, the highest level of mineral P could not improve the volatile compounds, but higher rate of farmyard manure even under lower portion of mineral P recorded higher concentration of the volatile compounds in garlic leaves. Therefore, combined application of organic and mineral P is recommended for better yield and quality of garlic.