Organic fertilizers are a significant and necessary supply of the different components that plants need, whether they are major or minor elements and their role in improving soil characteristics [1,2]. The modern trend tends toward organic agriculture, which is called clean agriculture, as it is one of the forms of sustainable agriculture, especially in productive orchards, when organic fertilizers decompose they have an acidic effect, as they work to reduce the soil reaction number (pH) as well as the content of nutrients in the soil [3,4] and increase their concentrations inside the leaves [5]. Among the most important organic fertilizer used is humic acid for orchids and grapes [6]. Humic-acid is the most prevalent kind of carbon in nutrients. Humic acid makes membranes more permeable to absorb nutrients and has the ability to improve the absorption of a nutrient and plant growth. Humic acid is a complex organic type that is water-loving has a dark color and creates the form of a liquid substance. Humate is represented chemically by the formula C75H33O17N3 (COOH) 3 (OH) 6 (CO) 2 and has a molecular weight of 1680. It is composed of carbon, nitrogen, hydrogen and oxygen in varying proportions, forming compounds with varying molecular weights. Humate is the most widespread type of humate and a commercial product made from some stones, Leonardite. Materials that can be found in Leonardite mines contain 60% humic and fulvic-acids and most likely commercial humate is a mixture of humate, fulva and humate. Humic acid enters plants in advanced stages as a complementary source of polyphenols that act as a respiratory chemical medium and this, in turn, leads to an increase in the plant’s vital activity, as the effectiveness of the enzymatic system increases and the production of dry matter increases. Due to the great importance of humic acid, many studies have been based on it [7], including Humic acid is the most important of the main products of humus decomposition, as it has a direct effect on the process of respiration and the process of photosynthesis [8] and its major role in improving soil properties, maintaining the regulatory capacity of the soil, improving the growth strength of plants and increasing the permeability of cellular membranes and absorption of elements. Nutritional value by the plant [9,10]. The nutrients in seaweed fertilizer improve vegetative growth, increase soil acidity and help plants absorb nutrients. In addition, seaweed contains iron, which improves plant growth. On the other hand, the natural plant hormones found in seaweed encourage chlorophyll production and root growth. It also works to increase the thickness of the cell wall to give plants a stronger structural structure and more resistance to pests and harsh environmental conditions. Marine algae extract is considered a natural fertilizer and can be used as a supplement to chemical fertilizers to avoid danger, in addition to being one of the cheapest and most effective organic plant nutrients [11]. Humic acid is a naturally occurring organic acid, a humic compound resulting from the decomposition of organic matter. It is humic acid that is most common type of environmental organic carbon and part of it is a chemical attractant for inorganic components such as metals, oxides and clay minerals to form soluble and insoluble compounds in water that interact with the organic components [12]. Organic products have been used to improve the growth and production of horticultural plants and have received a lot of attention and the new system of agricultural production has recently become dependent on them after it was found that chemical fertilizers have a harmful effect on the environment, humans and health [13] and the waste had to be disposed of. Through it, plants and animals are supplied and various crops are supplied with nutrients such as organic sources [14]. Humic acid increases nutrient absorption and the permeability of cell membranes [15], contributes to the activation of chlorophyll pigment and the assembly of sugars, enzymes and amino acids [16], increases the growth rate, stimulates cell division, develops the shoot and root system and increases dry matter in the plant [17]. Humic acid increases the element's contents of leaves by improving the physical, chemical and biological properties of the soil, such as increasing the activity and effectiveness of microorganisms and bacteria, which increases the absorption of elements by the roots and their transfer to the plant parts [18].

Lecturer Review

The Effect of Humic Acid on Vegetative Growth Characteristics: Muslim [19] observed that spraying seedlings of the Sweet Charli variety with the humic compound, which is considered a source of humic-acid, at two concentrations (1 and 2 g L⁻¹), when sprayed at a concentration of 2 g L⁻¹, produced a significant increase in the number of leaves, the area of one leaf and the dry weight of the strawberry plants. EL-Khawaga [20] noted that the addition of humic acid in amounts of 40, 50, 60, 70, 80 and 90 ml tree⁻¹ to peach trees of the Florida Prince variety with 40-90 gm N tree⁻¹ and 5-25 ml L⁻¹ tree⁻¹ of the biofertilizer, the more the level of humic acid added from 40-80 ml Tree⁻¹, the more chlorophyll the concentration  in  the  leaves  increases,  as  well  as  the area   of   the   leaves.   The   researchers   Al-Dulaimi   and Al-Sunbul [21] found that foliar feeding with humic acid and its effect on some characteristics of vegetative and root growth and yield of two varieties of Shalek, Rubygem and Fern and with four concentrations of humic acid (0, 1, 2, 4 ml L⁻¹). The findings demonstrated that foliar, especially spraying at a concentration of 4 ml L⁻¹ liter of humic acid achieved the best results in the total leaf area of strawberry plants. Judi [22] conducted an experiment on the effect of  humic  acid  on  some  characteristics  of two-year-old seedlings of Japanese pear, the nightshade variety, by  spraying  them  with  two  levels  of  humic  acid (0 and 2 ml L⁻¹). It was found that spraying with humic acid caused a significant increase in the chlorophyll content of the leaves. Al-Alaf [23] noted that adding humic acid at a concentration of 2 ml L⁻¹ to seedlings of figs of Black Diyala and White Adriatic had clear effects in improving most of the vegetative growth characteristics of the seedlings (the number of leaves, the number of new branches, the total chlorophyll content of the leaves, the dry weight of the leaves and the area leaf and leaf area of seedlings) which was significantly superior in these characteristics to the control treatment. Mervat et al. [24] noted that organic fertilizer (humic) was sprayed in two concentrations (6 and 9 liters per acre⁻¹) and uni-sal acid in two concentrations (4 and 6 liters per acre⁻¹) on grape vines of the Thompson Seedless variety, which were sprayed with three Equal sprays, the first at the beginning of growth, the second after growth is complete and the third three weeks after growth is complete, as it led to an increase in the vegetative growth of the vines as well as an increase in the concentration of chlorophyll in the leaves. Farahi et al. [25] observed, through hydroponic cultivation of the Aromas cultivar, using four concentrations   of   humic   acid   sprayed   on   the   shoots (0, 1.5, 3, 4.5 mg L⁻¹) that spraying with humic acid achieved a clear improvement in the quantitative and qualitative characteristics. For shellac yield, especially spraying  at  a  concentration  of  1.5-3 mg L⁻¹  of  humic acid in the chlorophyll content of leaves. Eshghi and Garazhian [26] showed that the use of humic acid improved the absorption of nutrients and increased the root  and  shoot  growth  in  the  Paros  cultivar,  grown  in 3-litre plastic anvils. The researchers used two methods to add humic acid: either spraying on the shoot at four concentrations (300, 600, 900, 1200 mg L⁻¹) or a ground addition  of  humic  acid  at  four  concentrations  as  well (300, 450, 600, 750 mg L⁻¹) and by adding 250 ml to each anvil, as the results showed that spraying at a concentration of 600 mg L⁻¹ gave the highest values for the dry weight of the shoot and root system, while spraying achieved a concentration of 900 mg L⁻¹  the best results in the chlorophyll content in the leaves, while the ground addition of humic acid achieved a concentration of 750 mg L⁻¹ the best space per leaf area. Shalan [27] found in a study on fifteen-year-old Leconte pear trees that adding 100 ml of Humic NPK (humic percentage 10%) led to a significant increase in leaf area. EL-Sehrawy [28] confirmed that adding Humic to the soil at 30 Tree⁻¹ led to a significant increase in the leaf area of apple trees of the Anna variety. Morsey et al. [29] observed in a study on apple trees that adding 30 mL of humic acid to trees⁻¹ led to an increase in the percentage of dry weight of the leaves. El-Boray et al. [30] when they studied apple trees of the Anna variety, that spraying with humic acid at a concentration of 4 ml L⁻¹ led to a significant increase in leaf area. Hussein [31] found in his study the effect of foliar spraying with salicylic and humic acids on the growth and yield of apricot trees (Prunus armeniaca L). The Royal variety recorded the highest percentage of chlorophyll content and humic leaf area when treated with humic acid at a concentration of 6 ml L⁻¹ compared to the control treatment. The highest percentage of total chlorophyll content was recorded in the leaves, which reached 20.50 mg.100 g⁻¹ fresh weight, while the lowest percentage was recorded for this. The trait in the comparison treatment amounted to 13.45 mg.100 gm⁻¹ fresh weight and the treatment with humic acid at a concentration of 3 ml L⁻¹ was significantly superior to the comparison treatment. The highest rate for this trait was recorded, which amounted to 43.45 cm² and the lowest rate obtained in the comparison treatment was 36.33 cm². Hussein [31] found the effect of adding humic acid on some vegetative growth traits of fig seedlings at concentrations (50.25.0) ml liter⁻¹ is significantly superior to 50 ml liter⁻¹ in leaf area. Al-Qadi et al. [32] found in their study on olive seedlings of the Ashiki variety when adding humic acid at concentrations of (100.50.0) mg L⁻¹ the concentration is 100. Significant effect on dry weight of shoots. Lateef et al. [33] found in his study of the effect of humic acids at three concentrations (0, 2, 4) g L⁻¹ on the growth characteristics and yield of strawberry fruits, a significant increase in leaf area, leaf chlorophyll content and dry weight of the shoots when treated with the comparison treatment. Mustafa and Lattif [34] mentioned in their experiment using two types of organic fertilizer, which included adding poultry and sheep fertilizer at five levels and adding humic acid at two levels (0 and 4 ml L⁻¹ on the Rubygem strawberry plant. The results showed that the level was 4 ml L⁻¹ Humic acid resulted in a significant increase in the average number of purlins and the chlorophyll content of leaves. Rashid [35] conducted an experiment on the use of eight types of organic fertilizers on the two varieties of strawberry, Festival and AOG and it was found that adding a mixture of 4 kg/m² of cow manure+4 kg/m² of mustard oilcake fertilizer+4 kg/m² of poultry manure It gave the best results in the number of leaves per plant and the number of purlins compared to the rest of the treatments. Motlagh et al. [36] found in their study on foliar spraying with humic acid for the morphological, flowering and fruit characteristics of the Local and Selva varieties that humic acid has a clear effect in increasing the growth and yield of the Shalek plant, as the researchers used concentrations of (0, 300, 600, 1000 mg L⁻¹) Humic acid was sprayed on the shoots of the shlek plant and they obtained the highest  values  for  the  number  of  leaves of the shlek plant by spraying at a concentration of 300 mg. 1 liter of humic acid. Omar [37] showed that adding the liquid organic fertilizer Neutrgreen at a concentration of (2 and 5 ml L⁻¹) to the Rubygem variety and that the spraying treatment at a concentration of 2 ml L⁻¹ resulted in a significant increase in the average number of leaves and the leaf area of the plant. Muhammad Ali [38] showed that adding humic acid at a concentration of 3 g L⁻¹ to three varieties of strawberry Rubygem, Festival and Kaiser’s Samling, caused a significant increase in the leaf area of the strawberry plant and the percentage of dry matter to the root system. Lateef et al. [39] studied the effect of potassium humate at three concentrations (0, 3, 6 g L⁻¹) on the growth and yield of apricot trees. The properties of vegetative growth, leaf area and leaf chlorophyll content all significantly increased with the usage of humic.

The Effect of Humic Acid on the Qualitative and Quantitative Characteristics of Fruit

Al-Dulaimi and Al-Sunbul [21] discovered that foliar feeding with humic acid had an impact on the yield and several aspects of vegetative and root growth in two strawberry kinds, Rubygem and Fern, at four different humic acid concentrations (0, 1, 2 and 4 ml L⁻¹). The results showed that feeding Foliar, especially spraying at a concentration of 4 ml⁻¹ liter of humic acid achieved the best results in the percentage of set and total plant yield of   strawberry   fruits. In a study by Al-Karawi and Al-Rawi [40] on adding humic acid at three concentrations to the soil (0, 2.5 and 5 ml L⁻¹) for the Albin cultivar, one month after planting the Shalek seedlings, the addition of humic acid resulted in a significant increase in the number of flowers, the percentage of nodes and the number of Fruits, increased fruit weight and yield of the strawberry plant. Lateef et al. [33] found in his study of the effect of humic acids at three concentrations (0, 2, 4 g L⁻¹) on the growth characteristics and yield of strawberry fruits, a significant increase in fruit weight, fruit size, percentage of total dissolved solids and vitamin C content of fruits when treated with comparison treatment. Hussein [31] found in his study the effect of foliar spraying with salicylic and humic acids on the growth and yield of apricot trees (Prunus armeniaca L). The Royal variety recorded the highest rate of average fruit weight, reaching 34.92 and 35.92 gm fruit⁻¹, respectively and the lowest rate for this trait was obtained when treating the comparison, which amounted to 32.61 gm fruit⁻¹. As for the  average  size  of  the  fruit  when  treated  with humic, it  exceeded  significantly,  the  comparison  treatment reached 36.84 cm² and the comparison treatment recorded the lowest rate for this characteristic, amounting to 33.18 cm³. Ullah et al. [41] found that spraying with three concentrations of humic acid, namely (1.5, 3 and 4.5 ml L⁻¹) on the Chandler cultivar after planting seedlings for 30 days, obtained the best results by spraying with a concentration of (3 ml L⁻¹) of Humic acid affected the characteristics of vegetative and fruit growth, especially the number of fruits, while no significant differences were observed in the character of total acidity in fruits. Alkharpotly et al. [42] showed that when they conducted a study on the strawberry plant, the Festival variety, grown in Aswan Governorate, Egypt, for two consecutive seasons, using three levels of seaweed extract and adding three levels of humic acid with irrigation, which is (0, 200, 400 mg L⁻¹), this resulted in The results show a significant superiority of the 400 mg L⁻¹ concentration of humic acid in most of the studied characteristics of total yield, yield per acre, vitamin C percentage, dissolved solids percentage, total acidity and total phenols content. Khafagi et al. [43] showed that adding 1 g L⁻¹ of humic acid to the Festival cultivar strawberry plant caused a significant increase in the rate of early yield of strawberry fruits, total yield, sugars and anthocyanin content and total phenols in the fruits. Motlagh et al. [36] found in their study on foliar spraying with humic acid for the morphological characteristics, flowering and fruiting of the local and Selva varieties that humic acid has a clear effect in increasing the growth and yield of the strawberry plant, as the researchers used concentrations of (0, 300, 600, 1000 mg L⁻¹). Humic acid was sprayed on the shoots of the strawberry plant and they obtained the highest values for the weight and number of fruits and the yield per plant of the strawberry plant by spraying at a concentration of 1000 mg. ¹ liter of humic acid. Lateef et al. [39] studied the effect of potassium humate at three concentrations (0, 3, 6 g L⁻¹) on the growth and yield of apricot trees. The use of humic led to a significant increase in the characteristics of fruit weight, fruit size and yield. Omar [37] used the addition of the liquid organic fertilizer Neutrgreen at a concentration of (2 and 5 ml L⁻¹) to the Rubygem variety. The spraying treatment at a concentration of 2 ml L ml L⁻¹ led to a significant increase in the total yield of fruits per plant. In a study by researcher Gili on the effect of different fertilizers, he used the addition of humic acid at three concentrations, which are (0, 20 and 40 gm tree⁻¹) and spraying with NPK nanocomposite fertilizer at four concentrations, which are (3.5, 2.5, 1.5, 0 gm L⁻¹) in some growth characteristics and yield of young apple trees of the local variety Ibrahimi, as the addition of 40 g tree⁻¹ of humic acid resulted in a significant increase in the weight and size of the fruit and the juice content of total phenols and vitamin C. Mosa et al. [44] showed in their study on Anna apple trees that spraying humic acid at a concentration of 5% resulted in a significant increase in the average weight of the fruit and the percentage of soluble  solids.  Morsey et al. [29]  concluded  that  adding 30 ml of humic acid to the soil. Tree-1 led to a significant effect in Average fruit weight and tree yield. Kazem et al. found in their study on Labib apricot trees that adding humic acid at a concentration of 6 g L⁻¹ led to an increase in the yield of one tree. Al-Araji found, when studying apple trees of the Golden Delicious variety, that fertilizing with  15 Matrix  fertilizer  (15%  humic  acid)  at  levels (20, 10, 0 ml L⁻¹) exceeded 20 ml L⁻¹. In the total sugar content of the fruits, it exceeded 10 ml L⁻¹  in the total tree yield and gave the lowest acidity in the fruits. Zainal found that pomegranate trees of the Slimi variety had a significant response when adding humic acid at a concentration of 1 gm L⁻¹ in the percentage of total dissolved solids. TSS%, Al-Adding humic acid at concentrations  of  (6,  4,  2,  0 gm L⁻¹)  and  concentration (6 gm L⁻¹) increased yield per tree, average fruit weight, percentage of Total Soluble Solids (TSS), percentage of total sugars in fruits, percentage of total acidity in fruits and  fruit  vitamin C  content,  according  to  research  by El-Mohammadi et al. [12] on Ibrahimi variety apple trees.

We conclude from the previous studies mentioned that the use of humic acid has significantly affected growth characteristics and quantitative and qualitative yields and led to good vegetative growth as well as obtaining good yields with good qualitative and quantitative characteristics. Therefore, we recommend its use in fruit orchards as an alternative to chemical fertilizers.

1. Hellman, E. “Wine Grape Fertilization for Oregon.” Paper presented at the Annual Meeting of the Oregon Horticultural Society, Oregon State, 1997.

2. Hao, X.H. et al. “Effect of Long-Term Application of Inorganic Fertilizer and Organic Amendments on Soil Organic Matter and Microbial Biomass in Three Subtropical Paddy Soils.” Nutrient Cycling in Agroecosystems, vol. 81, no. 1, 2008, pp. 17-24.

3. Al-Tawqi, A.A. The Effect of Adding Some Organic Residues on Some Characteristics of Calcareous Soil. M.Sc. thesis, College of Agriculture, University of Baghdad, 1994.

4. Al-Fartousi, B.A.J. The Effect of Extracts of Some Organic Residues on the Growth of Wheat (Triticum aestivum). M.Sc. thesis, College of Agriculture, University of Baghdad, 2003.

5. Al-Obaidi, A.S.J.H. Response of Apricot Trees (Prunus armeniaca L.) Zinni Variety to Organic and Mineral Fertilization. M.Sc. thesis, Faculty of Agriculture, University of Baghdad, 2008.

6. Abu Nukta, F. “Environmental Impact of Fertilizers, Syria.” Proceedings of the Seminar on Production and Use of Chemical Fertilizers and Environment, Cairo, edited by M.M. El-Fouly and F.E. Abdullah, 2010, pp. 35-50.

7. Al-Obaidy, K. et al. “Effect of Foliar Application of Agrihumate and Urea on Some Growth Characteristics of Three Cultivars of Olive (Olea europaea L.).” Kirkuk University Journal for Agricultural Sciences, vol. 6, no. 2, 2015, pp. 13-22.

8. Dantas, B.F. et al. “Effect of Humic Substances and Weather Conditions on Leaf Biochemical Changes of Fertigated Guava Tree during Orchard Establishment.” Revista Brasileira de Fruticultura, vol. 29, no. 3, 2007, pp. 632-638.

9. Eman, A.A. et al. “Minimizing the Quantity of Mineral Nitrogen Fertilizers on Grapevine by Using Humic Acid, Organic and Biofertilizers.” Research Journal of Agriculture and Biological Sciences, vol. 4, no. 1, 2008, pp. 46-50.

10. Chen, Y. et al. “Humic Substances in Soil and Crop Sciences: Selected Readings.” Proceedings of a Symposium Cosponsored by the International Humic Substances Society, Chicago, Illinois, 1990.

11. Jeffries, P. “How to Make and Use Seaweed Fertilizer.” How to Guides, 2013, http://howto.yellow.com.

12. El-Mohamedy, R.S.R. and M.A. Ahmed. “Effect of Biofertilizers and Humic Acid on Control of Dry Root Rot Disease and Improvement of Yield Quality of Mandarin.” Research Journal of Agriculture and Biological Science, vol. 5, no. 2, 2009, pp. 127-137.

13. Don, C.E. and A.E.A. Curry. “Bioregulator Applications in Nursery Fruit Tree Production.” Proceedings of the Thirtieth Annual Meeting, Plant Growth Regulation Society of America, 2003, pp. 203.

14. Kannaiyan, L. “Bio-fertilizers: Key Factor in Organic Farming.” Hindu Survey of Indian Agriculture, 2000, pp. 165-173.

15. Martin, P. et al. “Nitrogen Fixing Bacteria in the Rhizosphere: Quantification and Hormonal Effects on Root Development.” Zeitschrift für Pflanzenernährung und Bodenkunde, vol. 152, no. 2, 1989, pp. 237-245.

16. Dong, S. et al. “Timing of Urea Application Affects Leaf and Root N Uptake in Young Fuji/M.9 Apple Trees.” Journal of Horticultural Science & Biotechnology, vol. 80, no. 1, 2005, pp. 116-120.

17. Van Soest, P.J. “Influence of Foliar Application of Some Nutrients (Fertifol Misr) and Gibberellic Acid on Fruit Set, Yield, Fruit Quality, and Leaf Composition of ‘Anna’ Apple Trees Grown in Sandy Soil.” International Journal of Agriculture and Environment, 2012.

18. El-Shenawey, F.E. and T.A. Fayed. “Evolution of the Conversion to Organic and Biofertilizers on Crimson Seedless Grapevine in Comparison with Chemical Fertilization.” Egyptian Journal of Applied Sciences, vol. 20, no. 1, 2005, pp. 212-225.

19. Muslim, S.M.R. Physiological Studies on the Growth, Yield and Fruit Quality of Some Strawberry Varieties. M.Sc. thesis, Department of Horticulture, Faculty of Agriculture, Benha University, 2010.

20. El-Khawaga, A.S. “Partial Replacement of Mineral N Fertilizer by Using Humic Acid and Spirulina platensis Algae Biofertilizer in Florida Prince Peach Orchards.” Middle East Journal of Applied Sciences, vol. 1, no. 1, 2011, pp. 5-10.

21. Al-Dulaimi, R.M.H. and O.K.I. Al-Sunbul. “The Effect of Foliar Feeding with Humic Acid and Soil Coverage on the Vegetative Growth Characteristics and Yield of Two Cultivars of Fragaria×ananassa Duch.” Al-Anbar Journal of Agricultural Sciences, vol. 10, no. 1, 2012, pp. 82-96.

22. Judi, A.T.The Effect of Humic Acid and Citric Acid on Some Characteristics of Japanese Pear Seedlings. M.Sc. thesis, 2012.

23. Al-Alaf, I.H.I. “Response of Vegetative Growth of Seedlings of Two Fig Varieties to the Addition of Humic Acid, Essential Plus Liquid Fertilizer, and Gibberellic Acid.” Al-Rafidain Agriculture Journal, vol. 41, no. 2, 2013.

24. Mervat, A. et al. “Minimizing Adverse Effects of Salinity in Vineyards.” Journal of Horticultural Science & Ornamental Plants, vol. 5, no. 1, 2013, pp. 12-21.

25. Farahi, H.M. et al. “Foliar Application of Humic Acid on Quantitative Characteristics.” Agricultural Communications, vol. 1, no. 1, 2013, pp. 13-16.

26. Eshghi, S. and M. Garazhian. “Improving Growth, Yield and Fruit Quality of Strawberry by Foliar and Soil Drench Application of Humic Acid.” Iran Agricultural Research, vol. 34, no. 1, 2015, pp. 14-20.

27. Shalan, A.M. “Effect of Biostimulant and Soil Amendment on Vegetative Growth, Yield and Fruit Quality of Pyrus communis lactone Pear Trees.” Journal of Plant Production, Mansoura University, vol. 5, no. 12, 2014, pp. 1973-1987.

28. El-Sehrawy, O.M. “Reducing the Amount of Nitrate in Anna Apple Fruits by Using Inorganic N along with EM, Yeast, and Humic Acid.” Alexandria Science Exchange Journal, vol. 36, no. 2, 2015, pp. 188-196.

29. Morsey, M.M. et al. “Effect of Using Organic and Biofertilizers on Growth, Yield and Fruit Quality of ‘Anna’ Apple Trees.” Journal of Plant Production, Mansoura University, vol. 6, no. 11, 2015, pp. 1789-1801.

30. El-Boray, M.S.S. et al. “Effect of Humic and Folic Acid with Some Nutrients at Different Times of Application on Yield and Fruit Quality of Anna Apple Trees.” Journal of Plant Production, Mansoura University, vol. 6, no. 3, 2015, pp. 307-321.

31. Hussein, S.A. “The Effect of Adding Humic Acid and Urea on Some Growth Traits of Fig Seedlings (Ficus carica L.) White Adriatic Cultivar.” Al-Furat Journal of Agricultural Sciences, vol. 9, no. 3, 2017, pp. 11-23.

32. Al-Qadi, R.A. et al. “The Effect of Organic Fertilization with Humic Acid and the Growth Regulator Naphthalene Acetic Acid (NAA) on Some Growth Characteristics of Olive Seedlings (Olea europaea L.) Cultivar Bashiqi.” Tikrit University Journal of Agricultural Sciences, vol. 18, no. 1, 2018.

33. Lateef, M.A.A. et al. “The Effect of Spraying with Humic and Boron on the Quantitative and Qualitative Characteristics of Two Varieties of Strawberry (Fragaria × ananassa Duch.).” Kirkuk University Journal of Agricultural Sciences, vol. 7, no. 3, 2016, pp. 18-32.

34. Mustafa, A.M.H. and M.F. Lattif. “The Effect of Two Organic Fertilizer Additions on Vegetative Growth and Yield of Strawberry (Fragaria ananassa Duch.) Plant Variety (Rubygem).” Tikrit University Journal for Agricultural Sciences, vol. 18, no. 4, 2018, pp. 83-89.

35. Rashid, M.H.A. “Optimisation of Growth, Yield and Quality of Strawberry Cultivars through Organic Farming.” Journal of Environmental Science and Natural Resources, vol. 11, no. 1-2, 2018, pp. 121-129.

36. Motlagh, M.R.S. et al. “Leaf Application of Humic Acid on Morphologic, Flowering, and Fruit Traits of ‘Local’ and ‘Selva’ Strawberry Cultivars under Different Cultivation Beds.” Journal of Horticultural Science, vol. 35, no. 1, 2021, pp. 135-151.

37. Omar, Z.H.A. The Effect of Foliar Spraying with Salicylic Acids, Gibberellic Acids, and the Liquid Organic Fertilizer Neutrogreen on the Growth and Yield of Schleich (Fragaria × ananassa Duch.) Rubygem Cultivar. M.Sc. thesis, College of Agriculture and Forestry, University of Mosul, 2021.

38. Muhammad, A.I.R. The Effect of Humic Acid and Marine Extract (Phytoalg) on Some Growth and Flowering Traits of Three Varieties of Schleich (Fragaria × ananassa Duch.). Higher Diploma Thesis, College of Agriculture and Forestry, University of Mosul, 2018.

39. Lateef, M.A.A. et al. “Effect of Spraying with Cal-Boron and Potassium Humate and Maturity Stage on Fruit Quantity and Quality Characteristics of Apricot (Prunus armeniaca L.) cv. Royal.” IOP Conference Series: Earth and Environmental Science, vol. 910, no. 1, November 2021, p. 012038.

40. Al-Karawi, H.N.R. and W.A.G.A. Al-Rawi. “The Effect of Spraying with Organic Extract and Adding Humic Acid on the Yield of Strawberry Plants.” Iraqi Journal of Agricultural Sciences, vol. 47, no. 3, 2016, pp. 749-756.

41. Ullah, I. et al. “Influence of Humic Acid on Growth and Yield of Strawberry cv. Chandler.” Pure and Applied Biology, vol. 6, no. 4, 2017, pp. 1171-1176.

42. Alkharpotly, A.A. et al. “Impact of Soil Humic Acid Application and Seaweed Extract Foliar Spray on Growth, Yield, and Fruit Quality of Strawberry Plants Grown under Aswan Conditions.” Journal of Soil Science and Agricultural Engineering, Mansoura University, vol. 8, no. 6, 2017, pp. 307-315.

43. Khafagi, E.Y. et al. “Role of Arbuscular Mycorrhizae Fungi and Humic Acid in Controlling Root and Crown Rot of Strawberry.” Journal of Plant Pathology, 2018, pp. 65-74.

44. Mosa, W.F. et al. “The Effect of Foliar Application of Potassium, Calcium, Boron and Humic Acid on Vegetative Growth, Fruit Set, Leaf Minerals, Yield, and Fruit Quality of ‘Anna’ Apple Trees.” American Journal of Experimental Agriculture, vol. 8, no. 4, 2015, pp. 224-234.