Enhancing Sugar Beet (Beta vulgaris L.) Yield and Quality: Evaluating the Efficiency of Chemical and Mechanical Weed Control Strategies

Abstract

Weeds exert a pronounced influence on the sugar beet yield, leading to the potential for substantial reductions in agricultural productivity. In pursuit of addressing this issue, two experiments were conducted at the Faculty of Agriculture in Giza, Egypt, during the winter seasons of 2020/2021 and 2021/2022 to investigate the efficacy of various pre- and post-herbicides applied differently in active ingredient percentages, forms, and on weed target types, and mechanical weed treatments on weed traits and sugar beet crop performance. (1) In this context, five herbicidal treatments, including pre-emergence (S-Metoachlor) and post-emergence applications of Betanal Max Pro (Desmedipham 4.7% + Ethofumesate 7.5% + Lenacil 2.7% + Phenmedipham 6%), Tegrospecial (Desmedipham 20% + Phenmedipham 20%) for total annual weeds, C Factor (Haloxyfop-R-Methyl 7.5% + Fluazifop-p-putyl 15%), and Clictar (Clethodium 24%) for grassy weeds, were assessed alongside mechanical weeding and a weedy check (control). (2) The evaluations encompassed growth parameters, juice quality, and beet yields to comprehensively assess the treatment effects. (3) Notably, weed control measures, especially regarding three total annual weeds herbicides and the cultivation when using both grassy weed herbicides, consistently produced the highest improvements in sugar beet root’s fresh and dry weights, root dimensions, sucrose content, purity, sugar recovery, as well as the root and recoverable sugar yields, across both seasons. (4) However, it is important to note that the application of Clethodium 24% and Haloxyfop-R-Methyl 7.5% + Fluazifop-p-putyl 15% resulted in elevated levels of sodium, potassium, amino nitrogen, impurities, and sucrose loss to molasses. These findings underscore the substantial influence of herbicide use and mechanical weeding on sugar beet’s growth, juice quality, and yield, with S-Metoachlor, Desmedipham 20% + Phenmedipham 20% and Desmedipham 4.7% + Ethofumesate 7.5% + Lenacil 2.7% + Phenmedipham 6%—showing promise as effective weed control options, albeit with certain associated drawbacks.

1. Introduction

Weeds significantly impact sugar beet yields, potentially causing substantial reductions in crop productivity. Without effective weed management, yield losses of up to 100% are possible [1]. Weed competition in sugar beet cultivation can lead to a substantial decrease in root yield, ranging from 26% to 100% [2]. Consequently, effective weed control is essential to optimize sugar beet production.

Globally, sugar beet cultivation faces ecological challenges, particularly due to weed-related issues, as highlighted by El-Mageed et al. [3] and Makhlouf et al. [4]. Weeds pose economic hardships for sugar beet farmers, as discussed by Ghaly and Ibrahim [5]. Approximately 60 weed species are recognized in sugar beet fields, comprising 70% broad-leaved and 30% grassy species. Broad-leaved weeds dominate, casting a shading effect that outcompetes sugar beet plants for resources, limiting light penetration and crop yield potential [6].

To mitigate yield reductions, proactive weed management during the initial stages of sugar beet cultivation is crucial. Maintaining a weed-free environment for approximately 46 to 54 days following sugar beet plant emergence, as suggested by Dogan and Adem [7], is critical to prevent yield losses exceeding 5%. Weeds appearing within the first 8 weeks post-planting or 4 weeks after the plant reaches the two-leaf stage can lead to yield decreases ranging from 26% to 100% [5]. Effective weed management during the early growth stages is vital for optimal sugar beet development and to minimize weed competition [8].

Weeds possess characteristics such as rapid growth and adaptability, enabling them to outcompete crops and reduce yield potential [9]. Cultural, mechanical, biological, and chemical methods are available for weed control during the initial growth stages, but their effectiveness can be limited. This is partly due to the compact size of sugar beet seedlings, their limited resistance to herbicides, and their susceptibility to burial in soil during cultivation.

From an economic standpoint, weed control costs vary significantly. Manual weeding is the most expensive option, costing USD 771 per hectare, followed by flame weeding at USD 173 to USD 222 per hectare. Other methods, including brush weeding (USD 183 per ha), ECO weeding (USD 109 per ha), finger weeding (USD 94 per ha), torsion weeding (USD 54 per ha), and chemical weeding (USD 37 per ha) are more cost-effective [10]. Due to cost considerations, farmers often prefer chemical methods, which can achieve up to 90% weed control.

Mechanical weed control has gained traction in developing countries but requires further advancements to incorporate precision technologies. Consequently, the agricultural sector heavily relies on pesticides. However, the potential hazards associated with chemical substances must be considered [11]. Selecting pesticides must be done meticulously, with chloridazon and trilusulfuron commonly used for broad-leaved weed control [12,13]. In sugar beet cultivation, post-emergence herbicides are frequently applied on multiple occasions [14,15]. Mulching, which falls under the category of mechanical weed control, has proven to be an effective method for mitigating the adverse effects of weeds on sugar beet production. Weeds can significantly impact sugar beet’s quality and yield. Research conducted by Moursy et al. [16] highlights the positive impact of mulching, including the use of black and white polyethylene mulch. This practice not only suppresses weed growth but also enhances sugar beet quality traits. It leads to increased sucrose content, higher purity, improved extractable sugar percentage, enhanced root yield, and a boost in overall sugar yield.

Chemical weed control methods can significantly alter weed flora’s composition and abundance, while manual weeding with long-handled hoes can result in crop damage and leave some weeds unattended [17,18]. Cultivation practices can also disrupt weed growth by burying or uprooting them, severing their root contact with the soil.

A study by Bezhin et al. [19] evaluated two chemical weed management systems within a sugar beet field, consistently revealing higher yields of white sugar in plots treated with chemicals as compared to untreated ones. This underscores the urgency of effective weed management, especially when dealing with competitive weed species like Chenopodium album, Amaranthus retroflexus, and Polygonum convolvulus, which can outcompete sugar beet plants and rapidly reduce yields [20]. Early weed competition, soon after crop emergence, can lead to significant yield reductions. Importantly, the study showed that yields from manually weeded plots were similar to those treated with herbicides.

In a separate investigation by Deveikyte et al. [21], a mixed herbicide combination was evaluated for its impact on broadleaf weed species in sugar beet cultivation. The results indicated that the herbicide combinations were equally effective in suppressing various weed species, including Chenopodium album and Thlaspiarvense. The research also revealed that the weed weight decreased by approximately 20% when herbicides were applied at lower doses, emphasizing the importance of adhering to recommended herbicide doses for effective weed control.

Inadequate weed control measures can lead to yield losses of up to 100% in sugar beet crops [22]. Therefore, the objective of this work is to investigate the impact of weeds on sugar beet and the performance of pre- and post-herbicide applications with different active ingredient percentages and forms and the weed target types on sugar beet and weed traits.

2. Materials and Methods

2.1. Experimental Design

Two field trials were conducted at the experimental station, situated within the Faculty of Agriculture in Giza, Egypt, during the winter periods of 2020/2021 and 2021/2022. The station’s geographical coordinates are precisely 30°01′05.3″ N and 31°12′21.1″ E, at an elevation of 18 m above sea level. The experimental site’s soil type holds an official classification as clay loam. Over the course of these trial seasons, meteorological data revealed a consistent average temperature range spanning from 20 to 28 degrees Celsius. Precipitation was notably scarce, with near-zero levels observed. This comprehensive meteorological dataset was meticulously acquired from the meteorological station maintained by the Agricultural Research Center in Giza, Egypt. The data pertaining to the physical and chemical analyses conducted at the experimental site are provided in

Table 1. Analysis of the chemical and physical properties of the top 40 cm of soil during the seasons of 2020/2021 and 2021/2022.

Analysis	1st Season	2nd Season
Chemical analysis
Available N (%)	0.095	0.095
Available P (%)	0.080	0.089
Available K (%)	0.655	0.680
pH	8.44	8.59
EC (ds/m)	0.53	0.60
Physical analysis
Sand (%)	44.60	44.87
Silt (%)	20.20	20.22
Clay (%)	35.20	34.91
Soil type	Clay loam
Organic matter (%)	0.59	0.63

. The experimental design employed a randomized complete block arrangement with three replicates. The experimental plots had an area of 15 m² each and were comprised of five ridges. Each ridge, measuring 5 m in length, was separated by a distance of 60 cm, with 17.5 cm between individual hills within each ridge.

2.2. Studied Treatments

The experimental design consisted of seven treatments: (1) The control group, where weeds were allowed to grow throughout the season; (2) cultivation as a mechanical weed control method; and (3) five chemical herbicides applied differently in active ingredient percentages and forms, and weed targets types under trade names, including pre-emergence Kanzaclor (S-Metoachlor) and post-emergence applications of Betanal Max Pro (Desmedipham 4.7% + Ethofumesate 7.5% + Lenacil 2.7% + Phenmedipham 6%), Tegrospecial (Desmedipham 20% + Phenmedipham 20%), C Factor (Haloxyfop-R-Methyl 7.5% + Fluazifop-p-putyl 15%), and Clictar (Clethodium 24%). Following all herbicide applications, cultivation was performed 21 days after the herbicide application day, adhering to the recommendations provided by the Egyptian Ministry of Agriculture regarding the herbicide evaluation protocols on sugar beet crops. Herbicides were applied using a Knapsack sprayer at a rate of 480 L per h⁻¹. Detailed information on the applied herbicides, including their trade names, active ingredients, timing of application, and application rates, can be found in

Table 2. Explanation of the herbicidal interventions tested within the herbicide trials.

	Treatment/Trade Names	Active Ingredient	Form	Rate cm3 h−1	a.i. %	Time of Application
1	Betanal Max Pro	Desmedipham 4.7% + Ethofumesate 7.5% + Lenacil 2.7% + Phenmedipham 6%	OD	1560	20.9	Post-emergence
2	Kanzaclor	S-Metoachlor	EC	1680	96	Pre-emergence
3	Tergrospecial	Phenmedipham 20% + Desmedipham 20%	CS	2400	40	Post-emergence
4	Clictar	Clethodium 24%	EC	600	24	Post-emergence
5	C-Factor	Haloxyfop-R-Methyl 7.5% + Fluazifop-p-putyl 15%	EC	600	22.5	Post-emergence
6	Cultivation	Twice after 21 and 35 days after sowing date
7	Control	was an untreated control

.

Planting occurred on 15 September for the 2020/2021 year and 20 September for the 2021/2022 year. Immediate irrigation followed the planting process. Once the seedlings reached the 4–6 leaf stage, which was approximately one month after planting, thinning of the seedlings was performed to ensure that only one plant remained per hill. All other agricultural practices, including soil preparation, maintenance, and fertilization, were carried out following the guidelines provided by the Egyptian Ministry of Agriculture. Harvesting was conducted 180 days after the initial sowing date.

2.3. Studied Traits

2.3.1. Weed Density

Weed density, in terms of both the number of fresh and dry weights and the total number of weeds (grassy and broadleaves), was evaluated after the application of cultivation for all herbicidal treatments. This means that the herbicide treatments were followed by cultivation 21 days after spray. This assessment involved the utilization of a 0.25 m² frame, which was randomly positioned at three locations within each plot. The fresh and dry weights of the weeds were recorded. To determine the weed control efficacy (WCE) of the treatments, calculations were performed for both the overall weed density and the individual weed species using the following Equation (1) [23]:

$$WCE=\frac{WDC-WDT}{WDC}\times 100$$

(1)

where WCE—weed control efficacy (%); WDC—weed density (number·m⁻²) on control treatment; WDT—weed density (number·m⁻²) after treatment. The weed samples were measured at 21 days after cultivation.

2.3.2. Growth of Sugar Beet Traits

At the time of harvest, a representative sample of five plants was selected from each plot to determine the fresh and dry weights of the roots (in grams). The samples were subsequently subjected to oven drying at a constant temperature of 70 °C until a constant dry weight was achieved. Furthermore, the root length and diameter (in centimeters) were measured for each sample.

2.3.3. Quality Traits

• A random sample of ten sugar beet plants was collected from the central area of each plot to determine the juice quality traits. The following analyses were performed:
• Total soluble solids (T.S.S.) %: Measured using a PRI model digital refractometer (ATAGO).
• Sucrose content: Determined using a saccharometer on a lead acetate extract obtained from freshly macerated roots, following the method described by Carruthers and Oldfield [24].
• Purity%: Calculated according to the formula proposed by Carruthers et al. [25]:

$$\mathrm{P}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{t}\mathrm{y}\%=(\mathrm{S}\mathrm{u}\mathrm{c}\mathrm{r}\mathrm{o}\mathrm{s}\mathrm{e}/\mathrm{T}.\mathrm{S}.\mathrm{S}.)\times 100$$

(2)

• Impurity components: Potassium (K), sodium (Na), and amino N (Milleq/100 gm beet) were quantified using the method outlined by the Association of Official Agricultural Chemists (A.O.A.C) [26].
• Impurity percentage: Assessed based on the methodology described by Carruthers and Oldfield [24]. The impurity % was calculated using the formula:

$$\mathrm{I}\mathrm{m}\mathrm{p}\mathrm{u}\mathrm{r}\mathrm{i}\mathrm{t}\mathrm{y}\%=(\mathrm{K}+\mathrm{N}\mathrm{a})\times 0.0343+(\mathrm{A}\mathrm{m}\mathrm{i}\mathrm{n}\mathrm{o}-\mathrm{N}\times 0.094)+0.29$$

(3)

• Sucrose loss to molasses (SLM)%: Calculated based on the equation proposed by Reinefeld et al. [27]:

$$\mathrm{SLM}=\left\{\right(0.343 (\mathrm{Na}+\mathrm{K})+0.094(\mathrm{Amino} - \mathrm{N}) - 0.31\}$$

(4)

2.3.4. Yield

Plants from the three central rows of each plot were carefully uprooted and topped to determine the following parameters: root yield (tons per hectare), sugar recovery percentage (calculated according to the methodology outlined by Reinefeld et al. [27]), and recoverable sugar yield (ton·ha⁻¹).

$$\mathrm{Sugar} \mathrm{recovery}=\mathrm{Sucrose}\%-0.029 - (0.343 (\mathrm{Na}+\mathrm{K})-0.094(\mathrm{Amino}- \mathrm{N})$$

(5)

$$\mathrm{Recoverable} \mathrm{sugar} \mathrm{yield} (\mathrm{ton}·{\mathrm{ha}}^{-1})=\mathrm{Root} \mathrm{yield} (\mathrm{ton}·{\mathrm{ha}}^{-1}) \times \mathrm{Sugar} \mathrm{recovery}\%$$

(6)

2.4. Statistical Analysis

Statistical analyses were performed on the growth, juice quality traits, and beet yields using the methods outlined by Snedecor and Cochran [28]. The analysis of variance technique, as implemented in the computer software package Mstat-c [29], was utilized. For the comparison of treatment means, the least significant differences (L.S.D) test was conducted at a 5% significance level, following the suggestion of Steel and Torrie [30].

3. Results

3.1. Weed Traits

During two consecutive seasons, the dominant weed species observed were primarily broad-leaved weeds, including Beta vulgaris L. (wild beet), Ammimajus L. (Greater Ammi), Melilotusindica L. (common sweet clover), Chenopodiummurale (nettle-leaved goosefoot), Emexspinosa (spiny threecorner-Jack), and Cichoriumpumilum (wild endive). Among the grassy weeds, Avenafatua L. (wild oat), Phalaris minor (greater phalaris), and Loliumtemulentum L. (ryegrass) were prevalent.

The results depicted in

Table 3. The average weed fresh weights, dry weights, and weed density affected by weed control treatments in the 2020/2021 and 2021/2022 seasons.

Weed Control Treatments	Fresh Weight (g)		Dry Weight (g)		Number		Weed Group
	1st Season	2nd Season	1st Season	2nd Season	1st Season	2nd Season
Desmedipham + Ethofumesate Lenacil + Phenmedipham	683.0 d	623.3 bcd	36.4 c	46.1 bc	34 c	40 c	Broad-leaves
S-Metoachlor	416.7 e	414.3 d	28.2 c	32.5 c	27 c	26 c
Phenmedipham + Desmedipham	707.7 cd	503.7 cd	48.2 c	24.9 c	32 c	40 c
Clethodium	888.0 b	988.0 b	79.5 b	89.5 b	57 b	67 b	Grassy-weed
Haloxyfop-R-Methyl + Fluazifop-p-putyl	827.3 bc	995.7 b	84.5 b	92.8 b	66 b	79 b
Culivation	680.3 d	959.7 bc	80.6 b	87.3 b	60 b	70 b
Control	1887.0 a	2087.0 a	254.4 a	322.7 a	108 a	142 a
L.S.D at 5%	135.2	479.8	23.2	47.1	12	14

The letters a–e to show statistically significant differences between variables.

demonstrate significant variations among weed control treatments in terms of their impact on fresh and dry weed weights, weed density per square meter (m²), and weed control efficiency (WCE).

Weed densities, quantified as the number of weeds per square meter, were substantially higher in the weedy treatment plots, with a total density ranging from 108 to 142 weeds·m⁻² across both seasons. In comparison, the lowest densities were observed in the S-Metoachlor, used as the pre-herbicide treatment, with densities ranging from 27 to 26 weeds·m⁻². Phenmedipham + Desmedipham exhibited slightly higher densities, ranging from 32 to 40 weeds·m⁻², while Desmedipham + Ethofumesate Lenacil + Phenmedipham demonstrated densities of 34 to 40 weeds·m⁻². These differences were statistically significant.

The fresh weights of weeds (g·m⁻²) were analyzed, and a statistical ranking was determined based on the extent of the reduction in both fresh and dry weights. The S-Metoachlor pre-emergence herbicide treatment exhibited the highest reduction in fresh and dry weights during the first season. The cultivation method and Desmedipham + Ethofumesate Lenacil + Phenmedipham herbicide followed closely in the first season. Phenmedipham + Desmedipham showed the second-highest reduction in fresh weights during the first season and ranked third in the second season. These results were in direct contrast to the weedy check treatment. Regarding the dry weights of weeds per square meter (m²), the Phenmedipham + Desmedipham and Desmedipham + Ethofumesate Lenacil + Phenmedipham treatments significantly reduced the dry weights compared to the other treatments and the control.

Meanwhile the fresh weights, dry weights of grassy weeds and weed density affected by grassy herbicides treatments in the 2020/2021 and 2021/2022 seasons. The fresh weights of weeds (g·m⁻²) were analyzed Clethodium was the best for reducing fresh and dry weights during both seasons compared to control followed by Haloxyfop herbicides.

Figure 1 shows the WCE for different types of herbicides, the time of application, pre- and post-emergence, and differences in specialists on grassy and broad-leaved weeds that affect weed growth during two seasons; all treatments improved the WCE compared to the control (untreated).

The weed control treatments exhibited significant differences in terms of weed control efficiency (WCE) during both seasons. The application of herbicides resulted in increased WCE percentages. Among the treatments, S-Metoachlor demonstrated the highest WCE values, reaching up to 74% and 81% in the respective seasons. Desmedipham + Ethofumesate Lenacil + Phenmedipham achieved WCE values of 68% and 71%, while Desmedipham + Ethofumesate Lenacil + Phenmedipham showed WCE values of 70% and 71%. In comparison, mechanical cultivation had a WCE of 39% and 44% in the two seasons.

3.2. Sugar Beet Growth

The application of herbicides and cultivation demonstrated a significant influence on various growth parameters of sugar beet, including the fresh and dry root weights, as well as root length and diameter, throughout both growing seasons, as presented in

Table 4. Average of sugar beet root growth traits as affected by weed control treatments in 2020/2021 and 2021/2022 seasons.

Weed Control Treatments	Root Fresh Weight (g)		Root Dry Weight (g)		Root Length (cm)		Root Diameter (cm)
	1st Season	2nd Season	1st Season	2nd Season	1st Season	2nd Season	1st Season	2nd Season
Desmedipham + Ethofumesate Lenacil + Phenmedipham	1020.1 a	892.7 a	351.9 a	309.9 a	30.2 a	31.0 a	10.8 a	9.3 a
S-Metoachlor	745.3 b	461.4 c	236.4 c	180.4 b	29.7 a	26.0 c	8.7 b	6.2 c
Phenmedipham + Desmedipham	988.9 a	597.1 b	319.9 b	185.3 b	29.3 a	27.2 b	10.6 a	6.8 b
Clethodium	510.6 c	412.6 d	178.9 d	176.4 b	25.5 b	22.7 e	6.0 c	4.9 e
Haloxyfop-R-Methyl + Fluazifop-p-putyl	399.8 d	368.6 e	156.4 d	132.2 c	25.4 b	19.6 f	6.4 c	5.4 d
Cultivation	552.1 c	429.2 d	211.5 c	181.6 b	26.8 b	24.5 d	8.5 b	6.9 b
Control	328.0 e	217.8 f	67.9 e	72.6 d	23.0 c	22.5 e	6.4 c	4.3 f
L.S.D.at 5%	51.3	25.7	26.3	10.7	2.1	0.6	0.8	0.4

The letters a–f to show statistically significant differences between variables.

and also illustrated in Figure 2.

Among the herbicides tested, S-Metoachlor exhibited the most pronounced effects on the plant growth traits, followed by Phenmedipham + Desmedipham, Desmedipham + Ethofumesate Lenacil + Phenmedipham, Haloxyfop-R-Methyl + Fluazifop-p-putyl, and Clethodium in descending order. Conversely, the cultivation method employed for weed control resulted in lower values compared to the application of S-Metoachlor, Phenmedipham + Desmedipham, and Desmedipham + Ethofumesate Lenacil + Phenmedipham herbicides, yet it still exhibited a greater impact compared to the Haloxyfop-R-Methyl + Fluazifop-p-putyl and Clethodium applications (Table 4).

Specifically, the S-Metoachlor treatment led to a remarkable increase in the sugar beet fresh weight, showing growth enhancements of 211% and 309% in the first and second seasons, respectively, when compared to the untreated weed management control group. Furthermore, the root diameter saw notable improvements, with a 68.8% increase in the first season and a substantial 116% increase in the second season, once again, when contrasted with the control treatment (Figure 2).

3.3. Juice Quality

The experimental findings clearly demonstrated that effective weed control had a significant influence on the juice quality parameters (Figure 3).

Among the herbicide treatments, S-Metoachlor exhibited the highest sucrose content, with values of 16% and 15% in the first and second seasons, respectively. Desmedipham + Ethofumesate Lenacil + Phenmedipham recorded sucrose values of 12% and 14%, Phenmedipham + Desmedipham exhibited values of 14% and 15%, Haloxyfop-R-Methyl + Fluazifop-p-putyl showed values of 12% and 14%, and Clethodium yielded values of 11% and 13%. Conversely, the cultivation method resulted in sucrose values of 12% and 13%, while the control treatment yielded values of 10% and 13% in the first and second seasons, respectively.

Regarding impurities, the Clethodium application consistently led to the highest levels of sodium (Na), potassium (K), and amino N in both seasons, except for Na in the second season. This was followed by Haloxyfop-R-Methyl + Fluazifop-p-putyl, Phenmedipham + Desmedipham, the control treatment, S-Metoachlor, cultivation, and Desmedipham + Ethofumesate Lenacil + Phenmedipham, in descending order. The percentage of impurities did not exhibit a significant effect on weed management in the first season. The average impurity values were 0.90%, 0.80%, 0.73%, 0.69%, and 0.69% for Clethodium, Haloxyfop-R-Methyl + Fluazifop-p-putyl, Phenmedipham + Desmedipham, S-Metoachlor, cultivation, and Desmedipham + Ethofumesate Lenacil + Phenmedipham pro treatments, respectively. The control treatment recorded impurity levels of 0.76%.

Regarding sucrose loss to molasses (SLM), weed control with the Clethodium herbicide resulted in the highest values of 2.386% and 2.269% in the first and second seasons, respectively. Conversely, the Desmedipham + Ethofumesate Lenacil + Phenmedipham treatment exhibited the lowest values, with sucrose losses of 1.230% and 1.688%.

In the first season, applying S-Metoachlor herbicide resulted in the highest purity percentage of 78%. In the second season, both Phenmedipham + Desmedipham and S-Metoachlor treatments exhibited purity percentages of 70% and 69%, respectively, with no significant difference between them (Figure 4).

Regarding the sugar recovery percentage, the treatments in the first season were ranked as follows: S-Metoachlor, Phenmedipham + Desmedipham, Cultivation, Desmedipham + Ethofumesate Lenacil + Phenmedipham, Haloxyfop-R-Methyl + Fluazifop-p-putyl, and Clethodium, with the S-Metoachlor treatment yielding the highest percentage. Similarly, in the second season, the treatments were ranked as follows: S-Metoachlor, Phenmedipham + Desmedipham, Desmedipham + Ethofumesate Lenacil + Phenmedipham, Haloxyfop-R-Methyl + Fluazifop-p-putyl, cultivation, and Clethodium, with the S-Metoachlor treatment once again displaying the highest sugar recovery percentage.

3.4. Sugar Beet Root Yields

The findings presented in

Table 5. The average sugar beet yields as affected by chemical applications and mechanical weed control in the 2020/2021 and 2021/2022 seasons.

Weed Control Treatments	Root Yield (ton·ha−1)		Recoverable Sugar Yield (ton·ha−1)
	1st Season	2nd Season	1st Season	2nd Season
Desmedipham + Ethofumesate Lenacil + Phenmedipham	70.140 a	68.707 a	10.270 a	9.324 a
S-Metoachlor	61.268 b	59.949 b	6.777 c	7.505 c
Phenmedipham + Desmedipham	69.056 a	66.790 a	8.246 b	8.779 b
Clethodium	40.694 d	40.893 d	4.128 e	5.001 e
Haloxyfop-R-Methyl+ Fluazifop-p-putyl	40.160 d	40.884 d	3.698 f	4.419 f
Cultivation	49.379 c	52.059 c	5.621 d	6.146 d
Control	19.585 e	18.435 e	1.629 g	2.023 g
L.S.D.at 5%	3.051	3.011	0.232	0.328

The letters a–g to show statistically significant differences between variables.

provide evidence that all herbicide applications, along with cultivation treatments, had a significant positive impact on the root and recoverable sugar yields during both seasons in comparison to the control treatment.

In the first season, the root yield exhibited significant increases of 258%, 213%, 253%, 108%, 105%, and 152%, while in the second season, it further demonstrated notable increments of 274%, 225%, 262%, 122%, 122%, and 182%. Likewise, the recoverable sugar yield experienced substantial enhancements of 630%, 316%, 406%, 153%, 127%, and 245% in the first season, and 360%, 271%, 334%, 147%, 118%, and 204% in the second season for the S-Metoachlor, Desmedipham + Ethofumesate Lenacil + Phenmedipham, S-Metoachlor, Haloxyfop-R-Methyl + Fluazifop-p-putyl, Clethodium, and cultivation treatments, respectively, when compared to the control treatment (Table 5).

4. Discussion

Sugar beet exhibits a high susceptibility to weed competition, as supported by Salehi et al. [31]. Weeds pose a significant constraint to sugar beet productivity, consuming substantial amounts of soil water and nutrients. In the context of Egypt, weed densities and management methods, predominantly mechanical and chemical approaches, are employed for effective weed control. A 30-day period of weed competition following emergence can cause a drastic reduction in root yield, up to 45%, as reported by Soroka and Gadzhiev [32]. Assessing the growth traits of sugar beet, including the fresh and dry root weights as well as root diameter, reflects the efficiency of different treatment applications in terms of reducing weed species in the context of number, fresh weight, and dry weight. Significantly noteworthy is the pre-emergence herbicide treatment with S-Metoachlor, which demonstrates remarkable inhibitory impacts on weed growth characteristics. This is succeeded in diminishing order by treatments such as Phenmedipham + Desmedipham, Desmedipham + Ethofumesate Lenacil + Phenmedipham, Cultivation, Haloxyfop-R-Methyl + Fluazifop-p-putyl, and Clethodium. The extent of time during which weeds are kept at bay emerges as a pivotal factor influencing sugar beet’s growth and yield, as emphasized in the study by Jursiket al. [33]. Weeds rapidly outpacing the growth of sugar beet plants curtail their development by hindering the photosynthesis process. This leads to the casting of shadows, causing restricted water and nutrient absorption. Consequently, such competition leads to a reduced accumulation of dry matter and a decline in both the fresh and dry weights of sugar beet roots, aligning with the findings of Salehi et al. [31], which emphasize the importance and effectiveness of early-stage weed control in sugar beet cultivation compared to later stages. It is noteworthy that both chemical and mechanical methods rely on effective detection and recognition, with their success hinging upon the growth stage of both the weeds and the crop, as pointed out by Balas et al. [34].

The implementation of weeding control treatments resulted in significant improvements in the juice quality parameters, including the sucrose content, purity, and sugar recovery percentage. These enhancements can be attributed to the heightened photosynthetic rate and subsequent accumulation of a greater quantity of sugar. However, it is important to note that the use of the Phenmedipham + Desmedipham herbicide led to elevated levels of sodium, potassium, and amino nitrogen compared to the Clictar and C Factor treatments. This rise in impurities, along with the consequent loss of sucrose to molasses (SLM), adversely affected the overall juice quality. In contrast, treatments involving S-Metoachlor, cultivation, and Desmedipham + Ethofumesate Lenacil + Phenmedipham exhibited lower concentrations of sodium, potassium, and amino nitrogen, which positively influenced both the root and recoverable sugar yields. Particularly noteworthy is the superior performance of the S-Metoachlor application across both seasons, followed by Phenmedipham + Desmedipham, which demonstrated a high sugar recovery percentage and substantial root yield, effectively compensating for the relatively higher impurity levels. Additionally, the application of Desmedipham + Ethofumesate Lenacil + Phenmedipham and the cultivation treatment exhibited favorable effects, as cultivation successfully suppressed weed shoots and root growth prior to compromising crop yields. Moreover, cultivation contributed to improved soil structure, enhanced aeration, water penetration, and the availability of essential nutrients for the crop plants [35].

These results coincide with the study carried out by Balas et al. [34], highlighting the notable rise in sugar beet yield due to alternative weed control techniques. Nevertheless, it is crucial to recognize that cultivating the crops still involves a labor-intensive and expensive method, considering the considerable exertion and financial outlay required [35,36]. These outcomes are in agreement with the observations made by Adetola [37], who highlights the efficacy of cultivation in weed suppression, ensuring a loose soil surface, facilitating soil aeration, and enhancing the water retention capacity. On the contrary, manual mechanical methods of weed control have been overshadowed by the increasing prominence of chemical weed control techniques, as highlighted by Bhadra and Paul’s work [38]. In separate investigations, Hussain et al. [39] and Bayat et al. [40] assessed the effectiveness of different mechanical weeding approaches and herbicide applications in managing weeds during sugar beet cultivation. Their findings showcased a noteworthy decrease in both the weed biomass and density using mechanical weeding and herbicidal interventions. Notably, the most substantial reduction in weed biomass and density was achieved by implementing mechanical weed control at the fourth leaf stage of sugar beet growth. Conversely, herbicide treatments proved adept at suppressing weed populations until the harvest phase, thereby minimizing their interference with the crop and subsequent yield loss, as documented by Saudy et al. [41].

As a result, it is clear that sugar beet yields can be significantly harmed by aggressive weed species like Chenopodium album and Amaranthus retroflexus, resulting in losses that surpass 80%, according to Gerhards et al. [42]. A direct relationship exists between the density of weeds and the degree of sugar beet yield decline, as even minor weed densities lead to noteworthy drops in crop output. Particularly noteworthy is the impact of a high Amaranthus retroflexus density, which can cause an astonishing 95% reduction in sugar beet yield; even a mere 10 g·m⁻² of weed biomass is enough to trigger such substantial losses.

5. Conclusions

In conclusion, our research highlights the significant susceptibility of sugar beet (Beta vulgaris) to weed competition, which imposes substantial constraints on its productivity, primarily by competing for soil water and essential nutrients. Effective weed management strategies, encompassing both mechanical and chemical methods, are essential to mitigate yield losses in sugar beet cultivation. Early-stage weed control is particularly crucial, as it significantly impacts sugar beet’s growth and overall yield. Pre-emergence herbicides, especially S-Metachlor, have demonstrated superior inhibitory effects on weed growth, surpassing alternative treatments in descending order of efficacy. The duration of a weed-free period is critical for optimal sugar beet growth and yields.

It is also imperative to recognize that sugar beet’s juice quality, characterized by attributes such as sucrose content, purity, and sugar recovery percentage, is profoundly influenced by the choice of weed control treatments. Effective weed control enhances photosynthesis and sugar accumulation, thereby improving juice quality. However, the selection of herbicides also affects impurity levels, including sodium, potassium, and amino nitrogen. Treatments with lower impurity levels, such as S-Metachlor, cultivation, and Desmedipham + Ethofumesate Lenacil + Phenmedipham, lead to improved root quality and enhanced recoverable sugar yields.

Nonchemical weed control methods show promise in increasing sugar beet yields; however, their labor-intensive and costly nature requires careful consideration. In contrast, chemical weed control methods offer distinct advantages over manual mechanical techniques. Mechanical weeding during the fourth leaf stage of sugar beet, combined with herbicidal interventions, effectively reduces weed biomass and density, with herbicides providing lasting suppression until harvest.

Our findings emphasize the detrimental impact of highly competitive weed species, such as Chenopodium album and Amaranthus retroflexus, on sugar beet yields. Even low weed densities can lead to significant yield reductions, underscoring the crucial importance of implementing effective weed management strategies to minimize losses.

To further advance our understanding of sugar beet cultivation and weed management, future research efforts should focus on the following areas:

• Exploring innovative, sustainable, and cost-effective weed control methods to reduce labor and environmental impact.
• Investigating the long-term effects of different herbicides on soil health, as well as the potential for herbicide resistance in weed populations.
• Studying the impact of climate change on weed dynamics and the adaptation of weed control strategies to changing environmental conditions.
• Assessing the economic implications of various weed management approaches to provide practical guidance for sugar beet growers.

In summary, our research provides valuable insights into the multifaceted challenges posed by weed competition in sugar beet cultivation. It underscores the compelling need for judicious weed control measures to optimize crop productivity and enhance its quality while highlighting avenues for future research to address the evolving challenges in this field.