Inorganic fertilizers abundant used cause hazardous environmental effects and unsafe food. Contrarily, organic fertilizers are usually utilized as soil amendments and they boost crop yield quantity and quality. A field experiment was carried out to study the effect of some phosphorus (P) sources, such as rock phosphate (RP), superphosphate (SP), and sheep manure (SM), on some soil chemical properties, growth and yield in sugar beet plants. The field experiment was arranged in a completely randomized block design with three replicates for two growing seasons (2020/21and 2021/22). Results showed significant increases in yield and physiological parameters in all treatments. Co-applying of RP with SP caused a significant increase in the SOM, N, P, and K by 70.45, 31.52, 128.35, and 24.85% respectively compared to T1. All applications to the soil significantly increased the fresh weights of sugar beet roots were significantly increased by 24.71, 17.92 and 25.72% for T2, T3, and T4 respectively over the control. Also co-application of SM and SP (T3) lead to the highest sucrose content which increased by 5.09% than the control. Therefore, we concluded that integrated fertilizer management improves soil properties and yield so these results can be used to employ to reduce the detrimental consequences of using chemical fertilizers.
Introduction
Agricultural systems are currently aiming to maximize and maintain agricultural production the nutrient shortage is one of the key challenges in the development of economically effective agriculture. So using adequate rates and sources of natural organic fertilizers is very important not only to increase yield but also to reduce the production cost and environmental pollution (Ali et al. 2021; EL-Sharnoby 2021).
Phosphorus is an essential macronutrient required for the growth of plants alongside nitrogen and the addition of phosphate fertilizers is also important in ensuring the world’s food production (Torri et al. 2017). The productivity of crops is impacted by the deficiency of phosphorus, which affects more than 40% of the world’s arable land (Zhu et al. 2018; Victor Roch et al. 2019). In recent years, to ensure high crop yields, phosphorus-containing fertilizers have been widely used to counteract soil deficiency (Teng et al. 2020). This deficiency is a significant contributing factor to the poor fertile soil.
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On the other hand, phosphorus also shows an essential biochemical task in cell division, energy storage, respiration, photosynthesis, transfer, growth and many other processes in plants. It can help plant to live winter rigidities and contributes to disease resistance (Yadav and Pandey 2018; Khan et al. 2019).
Sheep manure (SM) is a nutrient rich organic carbon that can be used as a soil amendment to serve as a partial replacement for chemical fertilizers in agricultural production. Moreover, the addition of organic manure to soil can prominently improves physical and chemical properties, nutrient availability, microbial activity, increase yield, and enhance growth parameters (Paramesh et al. 2022). Moreover, organic fertilizers have fragmentize pattern with too much porosity, which helps great aeration and water retention capacity, and contain great nutrient amounts in available form for plant adsorption nitrogen, phosphorus, potassium, calcium, and magnesium etc (Chew et al. 2019; Ali et al. 2021; Al-Sayed et al. 2022; Güneş et al. 2023). Additionally, soil organic matter enhances the hold of nutrients, like N, P and S into its structure that mostly included C (55%), N (5–6%), P (1%) and S (1%) and these nutrients are released slowly and mostly taken up by plants (Al-Sayed et al. 2019; Ali et al. 2021). Farmyard manure (FYM) application caused significant yield increments during the 2016 to 2018 growth season. The average sugar beet yield was 52.9 tons ha−1 without FYM application and 61.2 tons ha−1 with FYM application.
For decades, chemical fertilizers have been utilized to enhance crop productivity (Hafez et al. 2021). Also, with the huge costs of chemical fertilizers, environmental pollution, and soil degradation, presently agriculture tends to reduce the use of these fertilizers (Al-Sayed et al. 2019 and Ali et al. 2022). Moreover, adding alone fertilizers containing phosphorus will deplete micro and secondary nutrients such as Zn, B, and S (Elias et al. 2019). To reduce the use of chemical inputs and maintain or increase soil fertility and plant nutrition, the use of organic fertilizers in modern agriculture is an option that is safe. Uprising prices of mineral fertilizers and the urge need of organic farming for sugar beet production attract the attention of organic market to add manures to sugar beet crop (Hlisnikovský et al. 2021). Moreover, the proportion of chemical fertilizer substitution should be carefully studied.
Rock phosphate (RP) is a natural mineral that contains high quantities of phosphate-bearing minerals and is classified as a non-renewable resource (Moussa et al. 2016). Also, RP is the basic raw material for makings soluble phosphate fertilizers (Saied et al. 2022). Agricultural intensification in developing countries with high reserves of rock phosphate can contribute as a source of phosphorus in the right way (El-Kherbawy et al. 2014). The production of 97% of the world’s phosphate ore is concentrated in 16 countries, with each country generating millions of tons annually (Abdelgalil et al. 2022). Moreover, adding organic matter to soil can increases available phosphorus, which supplies available P in rock phosphatefor plants. Rock phosphate solubilization might enhance the nutritional value of the plants (Maharana et al. 2021). The most important parameters which point to the overall changes in the soil chemical characteristics are soil reaction (pH). Soil reaction helps in preserving soil fertility and to keep equilibrium among soil nutrients (El-Sayed 2021).
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Co-application of alternative sources for P and inorganic fertilizers is a promising way to stabilize crop yields, increase nutrients in the soil, and alleviate environmental degradation to get healthy food.
Sugar beet (Beta vulgaris L.) is the main crop for sugar production in many countries. It ranks as the second most remarkable crop in the world after sugarcane for sucrose production. The cultivated area of sugar beet crop in Egypt through the 2018/19 season was ≈255,725.6 ha (increased by 23.5% over the 2017/18 season), that produce ≈12,247,170 tons of sugar (62.2% of national sugar production), with an average root yield of 47.89 ton ha‑1 (Ministry of Agriculture and Land Reclamation 2019). Nowadays, sugar production from sugar beet has reached 1.27 million tons which is about 58% of the total sugar production. The regional sugar industry relies on sugar beet since it occupies ≈14,700 hectares, 0.7% of the total cultivated area, (Rehab et al. 2019; Sugar Crops Council 2020). Nutrient management is essential for early sugar beet production. Insufficient nutrient and late fertilizer applications might cause irreversible root and sucrose yield reductions. Moreover, used fertilizer application is negatively correlated with sugar beet quality especially nitrogen (Hergert 2011; Van Eerd et al. 2012). The objectives of this study were to: (1) investigate the effects of different combinations of P fertilizer and rates on soil properties, growth plant, and yield of sugar beet. (2) Determine a better P management strategy for winter sugar beet yield, partial substitution of chemical fertilizer by the organic alone or with natural fertilizers phosphates. We hypothesized that co-application of RP fertilizer and SP under sheep manure maybe improve crop productivity and reduce the amount of inorganic P fertilizer.
Materials and Methods
Site Experiment and Design
A field trail was carried out during 2020/21 and 2021/22 growing seasons at the Agriculture Research Center Farm, Faculty of Agricultural, Al-Azhar University, Assiut Governorate, Egypt (27° 12′16.67″ N latitude and 31° 09′ 36.86″ E longitude). The experimental site’s climate was brought from Assiut Agrometeorological station, Assiut, Egypt, and is depicted in Table 1. Some physiochemical properties of the experimental site are listed in Table 2, while Table 3 show some chemical properties of tested materials.
Table 1
Basic climatic data of the experimental site during the period of the study (August to March 2020/21 and 2021/22). Based on Assiut agro meteorological station, Assiut, Egypt
Tmax (°C)
Tmin (°C)
R H (%)
W S (Kmh-1)
Sunshine
1st season
2nd season
1st season
2nd season
1st season
2nd season
1st season
2nd season
1st season
2nd season
August
38.4
39.10
24
24.20
38.5
28.10
17.1
14.50
11.9
11.90
September
37.8
35.20
23.2
21.40
41.1
39.50
17.8
18.10
10.8
10.80
October
34.6
32.40
20.5
17.60
47.8
44.20
17.1
14.90
10
10.00
November
25.3
28.60
12.7
13.40
55
50.70
14.9
9.90
9.4
9.40
December
23.60
20.30
9.40
7.70
53.60
54.70
14.30
10.70
9.00
9.00
January
21.4
16.88
7.1
4.47
58.9
35.90
13.5
17.10
8.9
8.87
February
21.6
21.22
7.3
8.07
57.4
51.18
15.9
15.17
9.7
9.70
March
27.1
22.25
11.3
8.03
43.4
41.65
18.6
17.33
9.9
9.87
Tmax maximum temperature (°C), Tmin minimum temperature (°C), RH relative humidity (%), W.S wind speed (km/h)
Table 2
Some physiochemical properties of the experimental site
Property
First season
Second season
pH (1:2.5 soil: water suspension)
8.22
8.24
ECe (dS m−1)
1.28
1.25
Organic matter (g kg−1)
10.00
10.50
Sand (g kg−1)
254
252
Silt (g kg−1)
392
393
Clay (g kg−1)
354
355
Texture
Clay loam
Clay loam
CaCO3 (%)
3.60
3.91
Available N (mg kg−1)
27.00
30.00
Available Olsen P (mg kg−1)
5.32
5.89
Available K (mg kg−1)
192
212
Table 3
Some chemical properties of tested materials
Characteristic
Sheep manure
Rock phosphate
Total‑N (g kg−1)
8.40
–
Total‑P (g kg−1)
12.00
170.00
Total‑K (g kg−1)
32.40
–
OM (g kg−1)
395.00
–
pH (1:5)
8.41
7.69
EC (1:5) dsm−1
5.16
4.09
The Agricultural Research Centre, Giza, Egypt was the source of sugar beet seeds (BTS 645. cv), and they were sown in the field at 22nd of August in each season. The experimental treatments were arranged in a completely randomized block design with three replicates with a total number of 12 plots, in each replicated three rows 70 cm apart with three hills. Sugar beet seeds were hand planted on hills in 5–10 cm depth with 25 cm apart (plants density 64260 ha−1). The unit of experiment was 3 m width × 3.5 m length (10.5 m2). The seedlings were thinned to one plant per hole after 20 days of sowing (DAS). According to the Egyptian Ministry of Agriculture and Land Reclamation, 71.40 kg P ha−1 from either rock phosphate (17% P2O5) or super-phosphate (15.5% P2O5) were applied to each plot alone or from both sources during soil preparation. Total 190.40 kg N ha−1 comes from two sources; 95.20 kg N ha−1 from sheep manure (0.8% N) as organic source was added through soil preparation and the other 95.20 kg N ha−1 from urea fertilizer (46% N) as chemical source was split into two uniform doses which applied at 30 and 90 days after sowing. Total 57.12 kg K ha−1 in form of potassium sulfate (K2O5) was divided into two equal doses; the 1st was added through soil preparation and the 2nd dose was added at 30 DAS. The tested treatments were as follows:
1.
The suggested amount of chemical fertilizers (N, P and K), as control treatment (T1).
2.
71.40 kg P ha−1 from rock phosphate (RP) (T2).
3.
71.40 kg P ha−1 from superphosphate (SP) (T3).
4.
35.70 kg P ha−1 from superphosphate (SP) + 35.70 kg P ha−1 from rock phosphate (RP) (T4).
At harvest, sugar beet roots and plant samples were gathered on 9th and 3rd of March 2021 and 2022, (after 199 and 195 days from sowing) respectively. Five randomly selected plants’ roots were taken at mid plot were collected to record the fresh weight, to estimate yield components and some quality traits (TSS% and Sucrose %). The fresh roots were washed with tap and distilled water, air dried, and oven dried at 70 °C until constant weight then dry yield was recorded, and picked random roots to be ground and stored for chemical analysis (N, P and K uptake).
Plant and Soil and Analysis
Soil texture was measured using pipette method and soil reaction (pH) was determined as described by (Page et al. 1982). Soil salinity and calcium carbonate were determined according to Burt (2004). Available P was extracted with 0.5 N NaHCO3 and measured spectrophotometery at 660 nm wavelength (Olsen et al. 1954). Available K was measured by the flame photometer (Jackson 1973). Available N was extracted by 1% K2SO4 at a ratio of 1:5. Then, 20 ml of the extract were distilled with the addition of 1 g Devarda’s alloy using a micro Kjeldahl’s (Jackson 1973). Soil organic matter (SOM) content was determined by oxidization with K2Cr2O7 and H2SO4 (Jackson 1973). The total N, P and K concentrations were measured in the digest extract. To measure the concentrations of these nutrients in beet roots, a mixture of 7:3 ratio of sulfuric to perchloric acids was used to digest the dried ground plant material (0.2 g). Total N, P and K were determined according to Burt (2004). Chlorophyll contents from fully developed leaves were measured by spectrophotometer at 663 and 644 nm for Chl‑A and Chl‑B, respectively; the blank was 95% ethyl alcohol that measured by the modified protocol of (Lichtenthaler 1987) using the following formulas:
Analysis of Variance and Duncan multiple range tests at 5% level of probability were used to examine significant differences among the treatments at seasons of 2020/21 and 2021/22. Data statistical analyses were performed using Costat software (Steel and Torrie 1986).
Results
Some Soil Chemical Characteristics
Application of sheep manure (SM) combined with rock phosphate (RP) and or super phosphate (SP) during both seasons realized positive and significant effects on decreased soil reaction (pH). The soil pH was moderately alkaline through all treatments and both seasons. Compared to control treatment, the added materials resulted in a significant rise in soil organic matter content (SOM) in both seasons. In contrast, the added materials adversely affected soil salinity (EC) compared to the untreated soil (Table 4). It was noticed that combined both P sources positively increased SOM and decreased soil pH while negatively increased soil salinity compared to other treatments. As average values of both seasons, the increases in soil salinity values were 8.33, 5.30 and 39.39% for T2, T3 and T4, respectively compared to T1 (control). Also the increases of SOM values were 47.26, 64.81 and 70.45% for T2, T3 and T4, respectively compared to T1.
Table 4
Influence of adding sheep manure and phosphorus sources on some soil chemical properties
Treatment
pH (1:2.5)
EC (1:1dSm−1)
OM (g kg−1)
1st
2nd
1st
2nd
1st
2nd
T1
8.24a
8.23a
1.30b
1.34b
12.60b
12.23c
T2
8.16b
8.15b
1.48b
1.38b
18.54a
18.04b
T3
8.14c
8.13c
1.44b
1.34b
19.46a
21.47a
T4
8.12d
8.11d
1.89a
1.79a
21.58a
20.75a
Means denoted by the same letter indicate insignificant difference according to Duncan’s test at p < 0.05
Nutrients Availability
Sheep manure applications combined with RP and SP throughout both seasons significantly (P < 0.05) increased N, P, and K availability (Table 5). In seasons, combined SM, RP, and SP (T4) significantly enhanced P availability compared to the other treatments. As average values of both seasons, available N increased by 37.12, 50.93 and 31.52% for T2, T3 and T4, respectively compared to control treatment (T1). Also, available P increased by 42.49, 75.82 and 128.35%, where available K increased by 24.83, 42.40 and 24.85% for T2, T3 and T4, respectively compared to T1.
Table 5
The effect of adding sheep manure and phosphorus sources on nutrients availability during both seasons
Treatment
N (mg kg−1)
P (mg kg−1)
K (mg kg−1)
1st
2nd
1st
2nd
1st
2nd
T1
51.44c
70.00c
6.98c
7.49c
226.60d
224.71b
T2
73.09a
92.29ab
9.73c
10.91b
259.94c
303.23a
T3
79.67a
102.67a
13.24b
12.14b
317.44b
325.17a
T4
70.00ab
88.67b
16.45a
16.57a
341.97a
321.15a
Means denoted by the same letter indicate insignificant difference according to Duncan’s test at p < 0.05
Macronutrients Uptake by Sugar Beet Roots
Adding SM mixture with RP or SP considerably impacted NPK uptake by sugar beet roots in both seasons (Fig. 1). Applying SM with RP (T2) achieved the highest N and P uptake by sugar beet roots since they increased by 78.44 and 46.60%, respectively, while (T4) achieved the highest K uptake since it increased by 65.03% over the control treatment. While the lowest nutrients uptake was observed at T4 (50/50 of both P sources mixed with sheep manure). During both growing seasons, the N and P uptake by sugar beet roots followed the order of T2>T3>T4>T1 (Fig. 1).
Fig. 1
Effect of adding sheep manure and varies phosphorus sources on nutrients uptake during both seasons. Means denoted by the same letter indicate no significant difference according to Duncan tests at p < 0.05
×
Sugar Beet Yield
Fresh and dry weight of sugar beet yield as affected by adding sheep manure with various phosphorus sources are shown in Table 6. Adding sheep manure mixed with rock phosphate (RP), superphosphate (SP), or both had a significant (p < 0.05) influence on total fresh and dry root yield weight in both seasons (2021–2022) compared to chemical fertilizers (T1). It was noticed that sugar beet yields are higher in the 2nd season than those of the 1st season. As average values of both seasons, the fresh weights of sugar beet roots were 64.92, 80.97, 76.56 and 81.64 ton ha−1 for T1, T2, T3, and T4, respectively. So, the relative increased of fresh weights of sugar beet roots were 24.71, 17.92 and 25.72% for T2, T3 and T4, respectively compared to control treatment (T1). The dry weights of sugar beet roots were 16.41, 19.04, 18.51 and 19.29 ton ha−1 for T1, T2, T3, and T4, respectively. The dry weights of sugar beet roots increased by 15.99, 12.83 and 17.55% for T2, T3 and T4, respectively compared to T1.
Table 6
Effect of adding sheep manure and phosphorus sources on fresh and dry weight of sugar beet roots
Treatment
Fresh weight
(t ha−1)
Dry weight
(t ha−1)
1st
2nd
1st
2nd
T1
64.05b
65.79c
16.27b
16.54b
T2
79.43a
82.50ab
18.62a
19.45a
T3
75.16a
77.95b
18.42a
18.60a
T4
78.17a
85.11a
19.26a
19.31a
Means denoted by the same letter indicate insignificant difference according to Duncan’s test at p < 0.05
Leaf Total Chlorophyll
At mid-season of sugar beet plants, the levels of chlorophyll (a) and (b) in leaves were higher in the 2nd season than those in the 1st season (Fig. 2). During both seasons, the highest chlorophyll (a) and (b) values were obtained When SM was combined with SP (T3) and RP + SP (T4), which increased chlorophyll (a) and (b) by 12.72 and 32.68%, respectively (T3), while, the treatment (RP + SP (T4) increased chlorophyll (a) and (b) by 16.81 and 40.68%, respectively. The levels of chlorophyll (a) and (b) of sugar beet leaves could be arranged in descending order of T4 > T3 > T2 > T1.
Fig. 2
Effect of adding sheep manure and varies phosphorus sources on some photosynthesis pigments. Means denoted by the same letter indicate no significant difference according to Duncan tests at p < 0.05
×
Sugar Beet Quality
The impact of applying sheep manure and various phosphorus sources on the sucrose content, total soluble solid (TSS), and purity percentage of sugar beet roots are shown in (Fig. 3). All treatments led to an increase in total soluble solid (TSS) compared to the control treatment (T1) with insignificant differences. However, Applying SM mixed with SP (T3) achieved the highest sucrose content by 5.09%, followed by SM combined with RP (T2) by 2.37%, SM mixed with SP + RP (T4) by 1.18%, and the latest one was the control treatment (T1). There were insignificant changes in purity percent between applying sheep manure combined with various phosphorus sources and the control treatment. On the other hand, the purity percent followed the descending order of T4 > T3 > T2 > T1.
Fig. 3
Effect of adding sheep manure and varies phosphorus sources on some sugar beet quality parameters. Means denoted by the same letter indicate no significant difference according to Duncan tests at p < 0.05
×
Relationship Between Soil Properties and Sugar Beet Yield
The impact of applying sheep manure combined with various phosphorus sources on soil properties, nutrient availability and sugar beet yield were evaluated by principal component analysis, PCA, (Table 7 and Fig. 4). The first four axes are significant for both seasons, with component weights of 91.03 and 90.39%, respectively, of the total variance. In the first season, with a 50% variance, the PC1 explained the variation in N, P, and K uptake (0.716, 0.891, and 0.819, respectively), yield (0.808), and dry weight (0.717), demonstrating the significant contribution of the application of sheep manure combined with various phosphorus sources to sugar beet productivity. The 2nd PC (68.02% CV) showed that OM (0.731), Av. P (0.918), Chl. B (0.974), and Chl. A (0.634) had substantial positive loading strength, revealing a strong connection between Av. P, OM, Chl. B, and Chl. A. It is also apparent that OM and Av. P play the most important roles in sugar beet productivity. The 3rd PC (80.73% CV) described available N and K (0.694 and 0.823), sucrose content (0.918) and total soluble solid (0.772), indicating the importance of sheep manure application in increasing available N and K. The PC4 (91.03% CV) revealed that there is a negative relation between purity (0.988) and TSS (−0.587). However, in the second season, PC1 explained 56.25% of the variance in OM (0.754), Av. P (0.919), Chl. A (0.775), Chl. B (0.913), and yield (0.609). The second PC (70.91% CV) revealed N, P, and K uptake (0.873, 0.915, and 0.802, respectively), as well as Av. K (0.620), yield (0.648), and dry weight (0.643). The 3rd PC (80.73% CV) described available N (0.548), sucrose content (0.792) and total soluble solid (0.912). According to the PC4 (90.39% CV), there is a weak positive relationship between purity (0.966) and sucrose content (0.532).
Table 7
Principal components and their loading in soil treated with sheep manure combined with various phosphorus sources, affect nutrient availability and sugar beet productivity through both seasons
Parameters
First season
Second season
1
2
3
4
1
2
3
4
OM
0.534
0.731
0.190
0.114
0.754
0.481
0.379
0.027
Av. N
0.535
0.445
0.694
−0.005
0.517
0.536
0.548
−0.104
Av. P
0.184
0.918
0.101
0.113
0.919
0.257
−0.148
0.111
Av. K
0.189
0.246
0.823
−0.015
0.613
0.620
0.264
0.105
Up. N
0.716
−0.342
0.546
−0.018
−0.100
0.873
0.345
0.022
Up. P
0.891
−0.072
0.428
0.074
0.313
0.915
−0.001
0.066
Up. K
0.819
0.518
0.024
0.026
0.576
0.802
0.115
0.054
Chl. A
0.406
0.634
0.467
−0.236
0.775
0.379
−0.140
−0.292
Chl. B
−0.014
0.974
0.178
−0.026
0.913
−0.043
0.270
0.028
TSS
0.033
0.042
0.772
−0.587
0.058
0.161
0.912
−0.316
Sucrose
0.068
0.117
0.918
0.212
0.053
0.268
0.792
0.532
Purity
0.021
0.081
0.081
0.988
−0.005
0.114
−0.114
0.966
Yield
0.808
0.413
0.126
−0.266
0.609
0.648
0.135
0.150
Dry weight
0.717
0.503
−0.098
0.176
0.368
0.643
0.316
0.306
Eigenvalue
6.99
2.53
1.78
1.44
7.88
2.05
1.59
1.14
Variance %
49.96
18.06
12.71
10.30
56.25
14.65
11.35
8.13
CV %
49.96
68.02
80.73
91.03
56.25
70.91
82.26
90.39
OM Organic matter, Av.N available nitrogen, Av.P available phosphorus, Av.K available potassium, Up.N, P, K Uptake nitrogen, phosphorus and potassium, Chl. A, B = Chlorophyll A, B, TSS Total soluble solids
Fig. 4
PCA of investigating soil and sugar beet parameters: projection of active variables on a PCA factor plane for two seasons: a first and b second
×
Discussions
Applying sheep manure to soil is known to increase SOM content due to sheep manure is easily degradable and stabilized organic matter. Nevertheless, application of SP and RP alone or combined with sheep manure increased organic matter due to the input of OM and nutrients from the organic amendments (Awad et al. 2021, 2022). Similarly, Janati et al. (2022) found that an increase in a compost based on waste plant, sheep manure, and rock phosphate application rate from 10 to 25 t ha−1 and from 25 to 40 t ha−1 increased SOM content by 13% and 69%, respectively.
Our results showed a decrease pH in all treatments. The hydrolysis of SM may also result in the release of organic acids, which could lower the soil pH. A slight change in soil pH has a considerable impact on the available phosphorus in the soil. Moreover, phosphorous is released in the system by the chemical reaction as a result of lowering pH by partial acidulation in the soil so it can be taken by plants or tends to alteration (Saied et al. 2022). The reduction in soil reaction (pH) may be more obvious with time due to soil microbial activity. This result is in convention with that observed by El-Tayeh et al. (2019) and Ali et al. (2021). Application of RP and/or SP increased soil salinity, which may be attributed to the high content of salts and alkaline substances. This effect was more pronounced when combined both RP and SP. This result agreed with that obtained by El-Tayeh et al. (2019) whom found that EC values regularly increased by adding organic materials (filter mud cake) at 10, 30, and 50% rates where the EC values of the tested soil were 0.55, 1.64, and 2.73 dS/m, respectively. Also, Khan et al. (2019), Youssef and Eissa (2017) and Ali et al. (2021) stated that adding manure caused a significant increase in salt and organic matter in soil especially sheep manure.
Adding various P sources with sheep manure fertilization increased available N, P, and K. The increase in the content of available NPK under combined application of sheep manure and sources of P fertilizers could be ascribed to the direct addition of RP, SP of SM added to the soil, and its decomposition as well as the raise the nutrient availability specially N caused by the decomposition of microorganisms to the soil native nutrients as indirect effect. This observation may indicate that using organic fertilizers have the ability to supply the growing plants by dissolved nutrients as a result of the acids they secrete which reduce the soil reaction increase macronutrient uptake process in plant tissues. After mineralization, SM supplies the soil with organic acids that dissolve soil nutrients and make them available for the plants (Bertand and Cleyetmarel 2008; Mondal et al. 2015; Awad et al. 2022).
Application of organic manure combined with sources of phosphorous fertilizers increased the content of available phosphorus. The application of rock phosphate and superphosphate together increased the availability of soil Olsen P by 59.67% compared to the sole application of rock phosphate, and by 30.10% compared to the sole application of superphosphate.
The sole application of rock phosphate or superphosphate to the soil was less effective than the combined application of the two amendments in increasing the availability and the uptake of nutrients by the sugar beet plants; this may be due to the great increase in the availability of P occurring in the soil when the two amendments were applied together (Eissa 2016). Plant-available K contents were higher in rock phosphate alone and a combination of super with rock phosphate in the first and second seasons respectively. This result is related to the ongoing release of available K from sheep manure during the two seasons.
In general, the combined application of P fertilizers enhanced sugar beet growth and development, and there was an increase in chlorophyll content as a result of increased soil P availability. Addition of P fertilizers combined with organic amendments is considered a successful management tool, improving the availability of soil macronutrients, especially under arid and semi-arid. However, application of organic amendments combined with P fertilizers also increased chlorophyll content (Karanatsidis and Berova 2014). Organic amendments can physiologically influence plant growth by releasing plant growth-regulating substances. This increase may be due to using P fertilizer or organic fertilizers that have the ability to supply the growing plants with dissolved nutrients as a result of the acids they secrete which reduce the soil reaction and ease the macronutrient uptake process in plant tissues (Li et al. 2021 and Eissa et al. 2013).
In the current study, an increase in chlorophyll a and b by 16.81 and 40.68% respectively at co-application rock phosphate with superphosphate. Chlorophyll a is responsible for the absorption of photons and plays a critical role in photosynthesis, whereas chlorophyll b also contributes to the transfer of light radioactive energy (Porcar-Castell et al. 2014; Siedliska et al. 2021).
All of this plays an important role in increasing vegetative growth and then photosynthesis pigments. This result was consistent with Abo Elazm (2008) and Youssef (2011) on marjoram plants. Bokhtiar and Sakurai (2005) reported that the chlorophyll content of leaf tissues was slightly increased by addition organic wastes (press mud, farmyard manure and sheep manure) and green manure.
Our study clearly indicated that the rock and superphosphate addition under the addition of sheep manure had a positive role in increasing the essential plant nutrients uptake. The increases in nutrient uptake, due to sheep manure addition, may be due to the improvement of soil quality. Organic matter addition may lead to an improvement in aeration and consequently an optimal root growth, thereby an increase in nutrient uptake and growth (Geng et al. 2019; Yang et al. 2021; Al-Sayed et al. 2023).
Co-application of organic fertilizers with RP and SP caused a visible enrichment in nutrient uptake by sugar beet plant, contributing to increase total yield. The uptake of phosphorus by beet roots was high compared to the control. Similar results were observed by (Zafar-ul-Hye et al. 2019) pointed that using manure alone or in combination with other biochar increases plant photosynthesis and nutrients uptake, which improves root/plant growth and increase the yield. The interaction of RP-blended SP mineral fertilizers, and SM also significantly increased the sugar beet yield by 25.72% over the control. This could be due to the root yield of sugar beet responded to combined RP and blended SP along with organic fertilizers as a result of increased soil organic matter, improved soil chemical properties, and increased nutrient availability, which helps to maintain soil nutrient status (Beura et al. 2019; Izhar Shafi et al. 2020; Shiberu et al. 2023). A combination of SP and RP was found to give higher sugar beet yields than fertilizer only, attributed to the increased agronomic efficiency due to the combined application. The result thus shows a significant increase in sugar beet yield due to either superphosphate or rock phosphate can be explained as a result of the reaction between water-soluble P with apatite P‑produced materials act as slow-release P fertilizer for sustainable agriculture. Our results are in agreement with (Saied et al. 2022).
The level of root yield obtained was relatively high and significantly exceeded, which reflects the effect of treatments on the fertility of the study site (Górski et al. 2022). This assumption is consistent with the findings of Maharjan and Hergert (2019), who found that using organic fertilizer (FYM) increased sugar beet yield. This indicated that the synergetic roles of mineral and organic fertilizers enhanced the productivity of the crop as observed in this study.
However, sugar beet quality obtained was suitability significantly, which reflects the effect of treatments on the soil fertility of the study site. The increment in sucrose % may be due to the role of phosphorus in improving growth and dry matter accumulation by increasing the uptake and availability of most nutrients, consequently enhancement sucrose contentin roots, also such might be due effect of organic fertilization, which important role in improving soil nutrients release as a result of the acids they secrete which reduce the soil reaction increase macronutrient uptake process in plant tissues. These findings are in line with Mahmoud et al. (2012); Abdou et al. (2014); El-Mansoub et al. (2014); Ghaly et al. (2019).
Conclusion
Combined application of different natural materials even organic or raw rock as fertilizers recognized positive impacts on the growth, quality, and sugar beet yield and improves soil properties. Combined rock phosphate and superphosphate with sheep manure significantly boost vegetative growth, yield, and sugar beet plants quality. This improvement would highly help in development of organic farming techniques and considerably reduce production cost and environmental hazards. Although the application of sheep manure (SM) combined with superphosphate and rock phosphate with mixing ratio of 50:50 (T4) give the appropriate fresh weight of sugar beet roots, but the addition of SM with recommended dose of superphosphate (T3) give the highest sucrose percentage.
Conflict of interest
A.M. Ali, A.Y. Mahdy, H.M. Al-Sayed and K.M. Bayomi declare that they have no competing interests.
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