Impact of mineral fertilizers on mineral nutrients in the ginger rhizome and on soil enzymes activities and soil properties

Ginger is used as one of the important ingredients in traditional as well as modern medicine besides as a spice. It boosts immunity and is a rich source of many biologically active substances and minerals. Although it is a medicinally important crop, its productivity is, however, affected due to poor nutrient management and therefore it requires an adequate supply of nutrients in the form of inorganic fertilizers or organic manuring, or a mixture of both. In this context, the present study was aimed to investigate the effect of mineral fertilizers on the content of mineral elements in the ginger rhizome, on soil enzyme activity, and soil properties. Lysimeter experiments were conducted at the Institute of Genetics and Plant Experimental Biology, Kibray, Tashkent region, Uzbekistan. The experiment comprised of four treatments T1 – Control, T2 - N75P50K50 kg/ha, T3 - and T4 - N100P75K75 + B3Zn6Fe6 kg/ha. The results showed that the application of N125P100K100 kg/ha increased rhizome K content by 49%, P content by 20%, and Na content by 58% as compared to control without fertilizer. While the application of N100P75K75 + B3Zn6Fe6 kg/ha showed a significant enhancement in rhizome K, Ca, P, Mg, Na, Fe, Mn, Zn, Cu, Cr, Mo, and Si contents over the control. This treatment also improved active P content by 29%, total P content by 80%, total K content 16%, and N content by 33% content, and the activities of urease, invertase, and catalase activities as compared to control of without mineral fertilizer and control respectively. Thus the application of NPK + BZnFe at the rate of 100:75:75:3:6:6 kg/ha helps in improving macroelements and microelements in the ginger rhizome and activities of soil enzymes that helps in mineral nutrition of the rhizome.


Introduction
Medicinal plants are a major source of traditional as well as modern medicine and play a major role in the world (Egamberdieva and Jabborova, 2020;Jabborova et al., 2020a;Mamarasulov et al., 2020Jabborova et al., 2021. Ginger (Zingiber officinale Rosc.) is a spice and medicinal plant belonging to the Zingiberaceae family. Ginger has long been used in folk medicine in India and China. Especially, the wet and dry root of ginger is widely used in the medicine and food industry (Jabborova and Egamberdieva, 2019). It has been used in folk medicine for colds, sore throats, asthma, and joint pain and stimulates appetite . Ginger is also rich in beneficial nutrients for example phosphorus, potassium, and calcium, which play important roles in human physiological processes. These substances play an important role in boosting human immunity and maintaining health Zadeh and Kor, 2014). The dry rhizome of ginger is medicinal contains biologically active compounds. The rhizome contains carbohydrates, fats, proteins, vitamins, minerals, amino acids, monoterpenoids (camphene, sineiol, borneol, citral curcumin, and linalool), gingerol, and sesquiterpenoids.
The spice ginger is one of the most widely used species of the family Zingiberaceae. It is a common condiment for various foods and beverages . Both fresh and dried ginger rhizomes are used worldwide as a spice, and ginger extracts are used extensively in the food, beverage, and confectionery industries (Jabborova and Egamberdieva, 2019;Zingiber officinale, 2010). It is also chiefly used medicinally for indigestion, stomachache, malaria, fevers, common cold, and motion sickness. Besides being a key ingredient in many world cuisines and food processing industry, ginger possesses anti-carcinogenic, antioxidant, and antiinflammatory properties (Zhao et al., 2016;Grzanna et al., 2005).
The production of this spice has been expanding in most parts of the world, as it can be grown under varied climatic conditions (Asfaw and Demissew, 2009). The productivity of ginger is, however, affected due to poor nutrient management Dinesh et al., 2012a), as it is a nutrient-exhaustive crop and therefore requires an adequate supply of nutrients at important stages of its growth (Weiss, 1997). Nutrient management options for this crop include inorganic or organic fertilizers or a mixture of both (Dinesh et al., 2012b). Effective nutrient management can help in reducing the overuse of chemical fertilizers, thereby safeguarding environmental quality. However, there are very few reports on the influence of different nutrient schedules on ginger yield and quality. Plant-derived foods have the potential to serve as dietary sources for all humanessential minerals (Minerals-Learn, 2010;Lokeshwari and Chandrappa, 2006).
The outcome of this study will ultimately help to ensure the dietary safety of society and improving both the quality and quantity of ginger. This study aimed to determine the levels of mineral nutrition in ginger, to assess the level of minerals in soil samples where the ginger was grown, and to correlate the levels of minerals in the ginger with that of soil in which it was cultivated.

Experimental design
Ginger (Zingiber officinale) rhizome was used for lysimeter experiments. A lysimeter experiment was conducted to study the effect of mineral fertilizers on mineral nutrients of ginger and soil properties. The experiment was carried out in randomized block design with three replications a lysimeter experiments at the Institute of Genetics and Plant Experimental Biology, Kibray, Tashkent region, Uzbekistan. Experimental treatments included T1 -Control T2 -N 75 P 50 K 50 kg/ha T3 -N 125 P 100 K 100 kg/ha T4 -N 100 P 75 K 75 + B 3 Zn 6 Fe 6 kg/ha Rhizomes were sown on 14 March for the year 2019. Harvesting was performed after 8 months of sowing.

Measurement of plant nutrients
Ginger rhizomes were harvested after 240 days of cultivation. Ginger rhizomes samples were prepared for analysis and were carried out in a special autoclave under the influence of hydrogen peroxide and nitric acid as disintegrating reagents for 6 h using a special microwave oven until the plant samples were converted into atomic elements. Sample volumes were accurately measured and 2% nitric acid (HNO 3 ) was added. The analysis was carried out on an optical emission spectrometer with an inductively coupled argon plasma (2100DV (USA), (Sarabekov et al., 2021).

Analysis of soil nutrient and soil properties
Soil samples were collected from a lysimeter of the Institute of Genetics and Plant Experimental Biology, Kibray district, Tashkent province. To determination the soil properties before experimenting, soil samples took of soil. The mechanical components of the soil were determined by Kachinsky's method (Tursunov, 2010). Carbon and organic matter contents of soil were determined according to the method of Tyurin modified by CINAO (Soil, 2003). Mobile compounds of phosphorus and potassium were determined by the Machigin method modified by CINAO (Soil, 2005a). The total phosphorus and potassium contents were determined (Soils, 2005b). The total nitrogen content was determined according to the method of Soils (2002). The salinity level of soil was determined by water extraction methods (Pancu and Gautheyrou, 2006). Analysis of soil properties is shown in Tables 1-3.

Analysis of soil enzymes
The urease activity, and invertase, and catalase activity of soil were assayed according to the method of Guo et al. (2012) and Xaziev and Xapbed (2005), respectively. For the estimation of enzyme activities, a 2.5 g soil sample was added with 0.5 mL of toluene and incubated for 15 min. Then mixed and added to 2.5 mL of 10% urea and 5 mL citrate buffer in an incubator at 38°C for 24 h. after incubation, it was filtered, then 4 mL of sodium phenate and 3 mL of sodium hypochlorite were added to 1 mL filtrate and diluted to 50 mL for 20 min. Enzyme activities were measured at 578 nm using a spectrophotometer. Urease activity was defined as the amount of enzyme that liberate NH4 per g of soil per h. Catalase activity was defined as the amount of enzyme that liberate oxygen per g soil while invertase activity was defined as mg of glucose liberated per g soil

Statistical analyses
All the experiments were performed in five replicates and the mean values of five replicates were considered. The data were statistically analyzed by one-way analysis of variance (ANOVA) and multiple comparisons of HSD employing the Tukey test with Stat View Software (SAS Institute, Cary, NC, USA). The significance of the effect of various treatments on plant growth parameters, plant nutrients, crop yield, and soil nutrients was determined by the magnitude of the p-value (p < 0.05 < 0.001).
The ginger rhizome microelements were not significantly increased by control without fertilizer (Table 5). The low rate NPK (75:50:50 kg/ha) gradually increased rhizome Fe, Mn, Zn, Cu, Cr, Mo, and Si contents compared to control. Data regarding rhizome microelements content showed that NPK applications rate (125:100:100 kg/ha) significantly enhanced rhizome Fe, Mn, Zn, Cu, Cr, Mo, and Si contents over to control. The NPK applications rate (125:100:100 kg/ha) a significant rise rhizome Fe content by 26%, Mn content by 51%, Zn content by 41%, Cu content by 31%, and Si content by 71% compared to the control. A maximum number of rhizome micronutrient content was recorded with NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) which resulted in rhizome Fe, Mn, Zn, Cu, Cr, Mo, and Si contents increase over the control and low rate NPK (75:50:50 kg/ha).
Data regarding the ginger rhizome ultramicroelements content showed that all treatments decreased rhizome Li, Be, V. Co, Ni, Ga, Ge, Ag, Cd, Sn, Sb, Cs, and Pb content ( Table 6). The results showed that the ginger rhizome was not In, Ta, Re, Hg, and Tl.

Soil agrochemical and chemical properties
The results of soil mechanical composition are listed in Table 7. The data knotted that the increased fertilizers combinations of T2-N 75 P 50 K 50 kg/ha, T3-N 125 P 100 K 100 kg/ha, and T4 -N 100 P 75 K 75 + B 3 -Zn 6 Fe 6 kg/ ha increased the mechanical composition of the soil (1-0.25 mm, 0.25-0.1 mm, 0.1-0.05). Whereas treatment 4 including macro and micronutrients N 100 P 75 K 75 + B 3 Zn 6 Fe 6 kg/ ha which had the highest amount of fertilizers was significantly increased soil mechanical particles (1-0.25 mm, 0.25-0.1 mm, 0.1-0.05) as compared to control.
The lowest level of total P content, total K content, N content, organic matter, active phosphorus, and potassium was evident in the soil without mineral fertilizer treatment (Table 8). The highest values of total P content, total K content, N content, organic matter, active phosphorus, and potassium were observed in soil with mineral fertilizer treatments NPK applications rate (125:100:100 kg/ ha) and NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha). The NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) enhanced nutrient contents of soil compared to all other treatments. However, NPK + BZnFe (100:75:75:3:6:6 kg/ha) treatment significantly increased active P content by 29%, total P content by 80%, total K content 16%, and N content by 33% compared to the control of without mineral fertilizer.

Table 6
The effect of mineral fertilizers on ultramicroelements content of ginger rhizome. Data are means of three replicates (n = 3), * asterisk differed significantly at P < 0.05.

Impact of mineral fertilizers on rhizome nutrients of ginger
Mineral elements are important for human, animal, and plant nutrition. Several scientists have been studied macro-micro elements in plants (Egamberdieva et al., 2016;Egamberdieva et al., 2017;Sarabekovet al., 2021). N, P, K are an important role play plant growth, development, and yield productivity . The studied ginger rhizomes in this study are a source of macroelements, microelements, and ultramicroelements cultivating in the Tashkent Region, Uzbekistan. For the first time the study of the content of macro-elements and microelements of ginger in the soil climatic conditions of the Tashkent region, Uzbekistan, revealed that N, P, K, Ca, Mg, Na, Mn, Fe, Zn, and Cu are high amount in the rhizome (Tables 4, 5). Many studies have been conducted on analyzing the essential and non-essential metal content of ginger in Nigeria (Obiajunwa et al., 2002;Ogunwandea and Olawore, 2004;Aiwonegbe and Ikhuoria, 2007), India (Devi et al., 2008), Saudi Arabia (Al-Eed et al., 2002;Alwakeel, 2008) and Ethiopia (Wagesho and Chandravanshi, 2015). Olubunmi et al. (2013) reported that nutrient analysis of ginger indicated their richness in calcium, magnesium, sodium, potassium, phosphorous, manganese, iron, zinc, and copper. The literature showed that there are no studies on the determination of mineral nutrients in ginger cultivated in Uzbekistan. N, P, and K fertilizers play an important role in plant growth, plant nutrition, and yield. The study showed that The NPK applications rate (125:100:100 kg/ha) enhanced significantly rhizome K content by 49%, P content by 20%, and Na content by 58% as compared to control. Macro and micronutrient Table 9 The effect of mineral fertilizers on chemical properties of irrigated soil in the Kibray district. Data are means of three replicates (n = 3), * asterisk differed significantly at P < 0.05.
Urease activity (mg NH4/g N/g soil/h) ** *** Treatments Fig. 1. The effect of mineral fertilizers on urease activity of irrigated soil. Data are means of three replicates (n = 3), * asterisk differed significantly at P < 0.05*, P < 0.01**, P < 0.001***. fertilizer NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) showed a significant increase in ginger rhizome K, Ca, P, Mg, Na contents over the control (Table 4). Similar findings corroborating increased ginger nutrients such as N content, P content, and K content by the NPK applications rate (100: 60: 60 kg/h) were reported by Yanthan et al. (2010). A positive effect of mineral fertilizers on the uptake of nutrients by ginger was observed by Thakur and Sharma (1997). Singh and Singh (2007) reported that enhanced uptake of nutrients in ginger by inorganic fertilizers.

Impact of mineral fertilizers on agrochemical and chemical properties of soil
Soil nutrients are an important role play for plant growth and yield. Many authors reported that the nutrient contents in soil were analyzed plant cultivating before and after Jabborova et al., 2020b). In the present study, we used mineral fertilizers application different levels to improve soil agrochemical properties of soil (Table 7). Mineral fertilizer treatments NPK applications rate (125:100:100 kg/ha) and NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) was found to increase the soil agrochemical properties such as total P content, total K content, N content, organic matter, active phosphorus, and active potassium compared to the control treatment (Table 7). The impact of inorganic fertilizers on agrochemical and chemical properties in soil was observed by several researchers (McDowell et al., 2004;Fang et al., 2009;Monaco et al., 2008;Wang et al., 2008). This finding is consistent with the report of Dinesh et al. (2012) who observed chemical nutrient management as a positive enhance total N of soil under rainfed ginger (Zingiber officinale Rosc.).Similar findings confirming increased the N content, P content and K content in soil by the NPK applications rate (100: 60: 60 kg/h) was reported by Yanthan et al. (2010). A recent study from Srinivasan et al. (2019) indicated that high mineral fertilizer decreased the N, P, K, Ca, Mg, and Fe content in the soil.

Impact of mineral fertilizers on soil enzymes
For the first time study of soil enzyme activity in soil cultivation ginger in Uzbekistan. Many studies have been conducted to determine soil enzyme activity in soil under cultivation ginger in India (Yanthan et al., 2010;Dinesh et al., 2012;Srinivasan et al., 2019). The data showed that the NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) significantly increased urase (Fig. 1), invertase (Fig. 2), and catalase activity (Fig. 3) in soil. Similar findings confirming the NPK applications rate (75: 50: 50 kg/h) increased the urease activity by 27.0% in the soil as was reported by Srinivasan et al. (2019). This finding confirms earlier studies by Singh (2015) and Allison et al. (2007) both observed urease enzyme activity in soil by mineral fertilizers application. The NPK application rate (75:50:50 kg/ha) decrease urease activity compared to T-3 and T-4. Dinesh et al. (2012) reported that the NPK application rate (75: 50: 50 kg/h) decreases urease activity. The literature showed that there are no studies on the determination of soil enzyme activity in cultivated ginger in Uzbekistan.

Conclusion
For the first time in Uzbekistan was studied the content of mineral elements of ginger rhizome cultivating in Uzbekistan. The NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) increased significantly rhizome macro and micronutrients N, P, K, Ca, Mg, Na, Mn, Fe, Zn and Cu contents. A higher rate of NPK + BZnFe applications rate (100:75:75:3:6:6 kg/ha) mostly increased soil agrochemical properties total P content, total K content, N content, organic matter, active phosphorus, and active potassium compared to the control and other treatments. The highest activity of urease, invertase, and catalase in soil by the NPK + BZnFe (100:75:75:3:6:6 kg/ha) fertilization rate was observed. The combined application of the NPK + BZnFe (100:75:75:3:6:6 kg/ha) is a better source of nutrient input for obtaining higher ginger yield as well as in sustaining soil fertility under the Uzbekistan soil-climate conditions.

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.