Effects of Nopal and Goat Manure on Soil Fertility and the Growth, Yield and Physical Characteristics of Tomato and Carrot Plants

Abstract

Nopal (Opuntia) is a resource that is discarded after pruning complete cladodes. For this reason, the aim of this study was to investigate the effects of the combined use of organic matter (nopal) and goat manure on changes in soil characteristics and on the growth and yield performance of carrot and tomato plants. Physicochemical analysis of the soil and goat manure was carried out, and germination tests and physical characterization of the plants and the products obtained were performed on tomato and carrot plants after adding the components of the cladodes alone and the cladodes with goat manure. The results showed that the application of the nopal cladode components increased the cation exchange capacity of the soil. The highest germination rate was obtained by the application of liquid nopal, with a 1.7-fold increase in the germination rate of carrot seeds, while that for tomato seeds was only 14%. Similar results were obtained for the germination percentage. An increase in resistance to water stress of approximately 15 days was observed in both tomato and carrot plants. Plant development and production were achieved in tomato, with a 100% increase in carrot plant length and a threefold increase in production. The addition of nopal to the soil improved the soil characteristics and the production yield of carrots and tomatoes.

1. Introduction

Currently, agricultural production is based on a series of practices involving the use of inorganic fertilizers that improve production by controlling pests and weeds. However, these unfavorable processes negatively impact soil ecosystems by contaminating groundwater, impairing soil fertility and leading to eutrophication and nitrate leaching [1]. On the other hand, the use of inorganic fertilizers generates emissions of high concentrations of GHGs such as carbon dioxide (CO₂), methane (CH₄) and dinitrogen monoxide (N₂O) [2]. In addition, agrochemicals also cause health problems in humans and toxicity throughout the food chain [3]. For this reason, the use of organic fertilizers in crop production is one of the most important pillars of sustainable agriculture for smallholder farmers today, along with biological and weed control and crop rotation [4]. However, even though organic farming is a beneficial practice, it is not an immediate solution [5,6]). It must therefore be integrated as part of a technology package, and as Amirahmadi et al. [2] noted, it is important to conduct a long-term follow-up of organic farming and its comparison with traditional crop farming.

One of the most important components in organic farming is the application of biofertilizers through nutrient management and soil remediation, including plant waste and animal manure [7,8]. These biofertilizers have been shown to have less of a negative impact on the environment, cause little or no harm to human health and reduce water consumption, and are also a source of organic matter and growth hormones. On the other hand, the use of biofertilizers has been reported to increase crop yields by up to 40% [9], and biofertilizers can be used as biostimulants for fruit production [10].

Research on the use of organic fertilizers has focused mainly on the addition of organic solid wastes, underutilized plants and plant parts. Two wild legumes, Lupinus exaltatus and Lupinus rotundiflorus, have been used as green manures to increase soil biological activity and plant nitrogen availability. Similar results were observed when corn stover was added as green manure [11]. In addition, rice, corn and soybean residues are considered soil amendments, with the former acting as a cadmium binder, while corn and soybean residues have been reported to affect soil heat capacity and thermal conductivity, although no consistent results have been obtained [12,13].

Plants of the genus Opuntia are added to improve the properties of degraded soils. Cladodes of Opuntia have been mixed with manure, plant waste and microalgae to produce fertilizer [14]. Other reports have suggested that the addition of nopal mucilage to soil alters the enzymatic activity of carbon cycling in different soils [15]. On the other hand, a cladode extract was used as an amendment agent in saline soil, and the results indicated an improvement in the electrical conductivity and physical and chemical properties of the soil [16]. However, only a few studies have investigated the effect of adding Opuntia cladodes as organic matter to the soil and its effect on the characteristics of different plants. For example, Muñoz et al. [17] studied the effect of adding nopal mucilage on the growth of tomato plants. However, when the nopal is pruned, whole cladodes are discarded, which can cause contamination. These cladodes can be used as organic materials to reduce their potential harmful effects on the environment. For this reason, the objective of this research was to study the effects of adding different components of nopal cladodes as organic matter alone or in combination with goat manure on the yield, quality, functional properties and plant growth of carrots and tomatoes and soil fertility status.

2. Materials and Methods

2.1. Characterization of the Vegetal Material

2.1.1. Conditioning of the Plant Material

Cladodes of Opuntia robusta were collected from Tacambaro, Michoacan (Mexico). The cladodes were harvested manually at 17:00 h and subsequently stored in a refrigerator at 4 °C for a maximum of 24 h until use.

The cladodes were prepared as follows, taking into account several steps described by do Nascimiento et al. [18]. For the first sample, the whole cladodes were ground in an industrial blender (International Brand) and collected for further use. For the second and third samples, the ground cladodes were filtered with a cotton cloth, and the solid and nonsolid components obtained were labeled as the second and third samples, respectively.

2.1.2. Physicochemical Analysis of the Nopal Cladode Soil and Goat Manure

The chemical composition of the nopal cladode was assessed with the following AOAC [19] methods: protein content was determined using method 955.04 with N × 6.25 as conversion factor, raw fiber with method 962.09, crude fat using method 920.39, moisture with method 934.01 and ash with method 923.03.

The moisture content, pH and texture of the soil (growing medium) and goat manure were determined according to the methods described by Walkley and Black [20]. Nitrogen was determined using the micro-Kjeldahl method (Digestor Kjeldahl, Luzeren^®, EQ-LUZ-KDN-08C, Hangzhou, China). Phosphorus was determined using the method described by Olsen [21], while potassium, calcium and magnesium were determined using a flame atomic absorption spectrometer (GBC, model SensAA; Dandenong, Australia). Microelements and trace elements were quantified using the DTPA (diethylenetriaminepentaacetic acid) method. For this purpose, 10 g of soil was placed in a 100 mL propylene tube containing 20 mL of extraction solution. The tube was shaken at 180 rpm for two hours and then filtered, after which the elements were quantified.

2.1.3. Germination Test

The influence of the addition of Opuntia robusta on the germination characteristics [germination velocity index (GVI), germination percentage and resistance to hydric stress] of carrots and tomatoes was investigated in a germination trial in trays and on agricultural land for cultivation. The tomato and carrot seeds were obtained from the varieties Saladet and Danvers (Hortaflor^®, Rancho Los Molinos SA de CV, Mexico ), respectively.

The GVI was calculated as proposed by Maguire [22] as follows:

$$\mathrm{G}\mathrm{V}\mathrm{I}=\left(\frac{{\mathrm{G}}_1}{{\mathrm{N}}_1}\right)+\left(\frac{{\mathrm{G}}_2}{{\mathrm{N}}_2}\right)+\cdots +\left(\frac{{\mathrm{G}}_{\mathrm{n}}}{{\mathrm{N}}_{\mathrm{n}}}\right)$$

where G₁, G₂, … G_n are the numbers of seeds that germinated on the first, second and last counts, respectively.

N₁, N₂, … N_n are the number of days at the first, second and last counts from the day of sowing, respectively.

Two germination experiments were carried out (Trial 1: germination tray and Trial 2: soil in field/open conditions).

For Trial 1, seeds were distributed in germination trays of 242 cavities, each cavity was filled with soil and/or a component of the cladodes of the nopal, and irrigation was constant until 100% water availability was reached at a germination temperature of approximately 28 °C; three treatments and a control were established for this trial according to

Table 1. Treatments applied for the germination test in the germination tray (trial 1).

Treatment	Component Incorporated into the Cavity of the Germination Tray (%)
	Soil	Component of the Cladode of Nopal
		Whole	Solids	Liquids
T0	100	0	0	0
T1	50	50	0	0
T2	50	0	50	0
T3	50	0	0	50

.

For Trial 2, a germination trial was conducted in soil under dry conditions in a randomized block design with four replicates. Treatments were established 30 days prior to seed incorporation. The distance between furrows was 0.6 m for both seeds, while the distance between seeds was 0.5 m for tomato plants and 0.25 m for carrot plants. When solid ingredients were used, 13 g was added, and when liquid ingredients were used, 20 mL was added to the soil. For the trials in soil under field conditions, two 86-seed sets were used for the carrots, and three 69-seed sets were used for the tomatoes. The differences in the number of seed sets were determined with regard to an appropriate plant density; seven treatments were carried out for this trial according to

Table 2. Treatments applied in the germination test under soil in field/open conditions (Trial 2).

Treatment	Component Incorporated into the Soil
	Goat Manure (g)	Component of the Cladode of Nopal
		Whole (mL)	Solids (g)	Liquids (mL)
T0	0	0	0	0
T1	0	20	0	0
T2	0	0	13	0
T3	0	0	0	20
T4	13	0	0	0
T5	6.5	10	0	0
T6	6.5	0	6.5	0
T7	6.5	0	0	10

.

2.1.4. Experiment on Plant Growth

The experiment was conducted in an experimental field in Tacambaro, Michoacan State, Mexico (at coordinates 19°13′03″ N and 101°29′12″ W and an altitude of 1534 m above sea level; the predominant soil group in the area is Acrisol). In brief, the plant growth experiment was conducted according to a completely randomized block design. In each block, 4 experimental plots with a size of 3 m × 20 m were established and randomly assigned to the different treatments (T₁, T₂, T₃, T₄, T₅, T₆, T₇ or the control). The nopal components and the goat manure were added 30 days before planting. The plots without nopal components or goat manure (control) were irrigated with the same amount of water as in the same treatments (for tomatoes, 72 mL for soluble solids and whole cladodes and 36 g for goat manure; for carrots, 63 mL for soluble solids and whole cladodes and 31.5 g for goat manure).

The soil for the experiment conducted in the experimental field was collected before the experiment was carried out, and new soil samples were taken after the experiment was completed to assess the changes.

2.2. Characterization of Products Obtained from Plants

2.2.1. Physical Characteristics of Plant Growth

Plant height, stem diameter, the number and size of leaves (length and width) and root length were determined for the two crops (carrot and tomato plants).

2.2.2. Production Characteristics

The number of fruits per plant and the average weight of the fruits were determined to evaluate the changes in the production characteristics of the tomato plants. For both crops (carrot and tomato plants), the total production and the equatorial and polar diameter of the final products were determined.

2.2.3. Statistical Analysis

An analysis of variance (ANOVA) was applied using SAS software (SAS v. 8.0), and the differences between treatments were calculated with Tukey’s test (p < 0.05).

3. Results and Discussion

3.1. Physicochemical Characteristics of Nopal Cladodes, Soil and Goat Manure

The chemical composition of the nopal cladodes (

Table 3. Chemical composition of nopal.

Sample	Moisture	Protein	Lipids	Ash	Crude Fiber	Free-Nitrogen Components
	g/100 g Dry Sample
Nopal cladode	6.26 ± 0.24	12.22 ± 0.02	13.30 ± 1.33	14.94 ± 0.12	8.42 ± 0.27	44.85 ± 1.82

Values are means ± SD, the samples are dry matter.

) shows that the free-nitrogen components are the main constituents, which correspond to a greater extent to the mucilaginous components that absorb and retain a high water content. However, the high content of ash, which, according to Bernardino et al. [23], is mainly present as Ca²⁺ in its free form or as calcium oxalate crystals, is striking. On the other hand, the protein content in nopal cladodes could alter the concentration of components that influence plant development [24,25].

The physicochemical characteristics of the soil and goat manure are shown in

Table 4. General properties of the soil and goat manure.

Substrate Component	Moisture (%)	E.C. (dS/m)	pH	O.M. (%)
Goat manure	34.6	11.12	8.95	100
Soil	30.5	0.86	7.71	2.92

E.C.— electrical conductivity; O.M.— organic matter.

. Higher electrical conductivity was found in the goat manure than in the soil, apparently due to the higher concentrations of macro- and micronutrients.

The pH of goat manure was greater than that of soil, but the determined pH of 8.95 corresponded to the pH values of cattle and sheep manure reported by Acevedo-Alcalá et al. [26], which were 8.54 and 9.09, respectively.

The content of micronutrients in goat manure is important because it provides a balanced supply of nutrients to plants during their development and can generate organic acids through decomposition. On the other hand, recent studies have reported that the use of animal manure increases the accumulation of secondary metabolites in some medicinal plants, such as Passiflora incarnata L. [27], chamomile (Matricaria recutita) [28] and Hyssop (Hyssopus officinalis) [29].

Table 5. Basic soil properties of the soil samples spiked with nopal and/or goat manure.

Soil Property	Treatments
	Initial	T0	T1	T2	T3	T4	T5	T6	T7
Texture	Clay	Clay Loam	Clay Loam	Clay Loam	Clay	Clay Loam	Clay Loam	Clay	Clay Loam
Sand (%)	30	25	29	29	27	29	27	34	34
Clay (%)	40	39	37	37	41	37	37	41	35
Silt particles (%)	30	36	34	34	32	34	36	25	31
Saturation point (%)	54	46	56	46	45	49	51	45	39
Field capacity (%)	40	35	42	35	34	37	38	34	29

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate.

shows that the addition of only a portion of nopal cladodes or goat manure in most treatments increased the silt content of the soil and decreased the clay content. Both the saturation point and field capacity decreased in most treatments. The addition of part of the nopal cladode or of the goat manure slightly altered the content of clay particles, which were the predominant particles; therefore, the soils are classified as clay or clay loam.

The change in particle content indicates that a change in soil structure was achieved, allowing longer periods between irrigations. It has been reported that the addition of manure significantly increases the amount of soil aggregates [30]. For this reason, the addition of nopal cladodes or goat manure seems to have increased silt–clay interactions and changed the soil texture in most treatments.

As shown in

Table 6. Chemical properties of soils after application of treatments.

Chemical Characteristic	Treatments
	Initial	T0	T1	T2	T3	T4	T5	T6	T7
pH	7.71	7.71	7.73	7.51	8.12	7.36	7.80	7.31	7.47
CEC (cmolc/kg)	16.79	19.07	17.88	14.52	17.86	16.44	22.02	20.63	22.46
Salt concentration	3.75	6.61	5.54	6.96	10.19	6.87	4.09	4.65	4.50

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate.

, the application of components of nopal cladodes increased the cation exchange capacity of the soil compared to the initial conditions. On the other hand, the addition of goat manure had a significant effect not only on the cation exchange capacity but also on the regulation of pH and salt concentration.

It has been observed that the addition of manure to clay soils has a positive effect, increasing the CEC [31] and, in some cases, changing the pH. However, the rate of change is determined by the origin of the manure and the concentrations of Ca, Mg and P. On the other hand, the CEC increased in treatments where manure was added, apparently due to the incorporation of N and P provided by the goat manure. Some authors have reported that the addition of N, P, K, Mn, Fe and Zn positively affects the CEC of soils [32]. The changes in soil elements are shown in

Table 7. Composition of elements in soils after application of treatments.

Element Concentration (mg/kg)	Treatments
	Initial	T0	T1	T2	T3	T4	T5	T6	T7
N-Inorg	61.2 e	73.7 b	55.6 h	70.3 c	78.6 a	60.5 f	57.8 g	53.6 i	65.4 d
P-Bray	N.D.b	7.2 a	N.D.b	N.D.b	N.D.b	N.D.b	N.D.b	N.D.b	N.D.b
K	631.9 b	404.5 h	517.5 d	396.8 i	483.4 e	452.5 g	670.4 a	468.4 f	624.4 c
Ca	1653.6 d	1595.8 e	1481.9 g	1150.5 i	1536.8 f	1286.7 h	1782.2 b	1719.9 c	1908.9 a
Mg	835.2 i	1208.1 d	1099.7 e	926.8 h	1068.8 f	1058.6 g	1363.6 a	1299.8 c	1357.6 b
Na	12.1 i	36.3 f	32.3 h	36.1 g	41.2 d	39.1 e	50.2 a	41.9 c	44.6 b
Fe	90.9 a	31.8 b	28.0 f	29.1 c	28.4 e	27.8 g	26.2 i	26.7 h	28.6 d
Zn	13.3 a	2.3 b	1.5 f	1.8 de	2.1 c	1.8 e	1.7 f	1.9 d	1.6 f
Mn	30.5 a	28.1 b	16.8 i	19.8 d	18.3 f	18.9 e	17.8 g	20.2 c	17.4 h
Cu	2.4 b	2.7 a	2.1 c	1.9 e	2.0 d	1.9 e	1.9 e	1.9 e	1.9 e
B	0.1 c	0.6 a	0.0 d	0.0 d	0.0 d	0.6 a	0.5 b	0.0 d	0.6 a
P-Olsen	55.0 a	N.D. e	15.1 d	18.2 bd	15.9 d	23.4 bc	25.5 a	17.1 cd	15.3 d
S	141.5 b	68.7 g	85.2 e	93.8 d	173.1 a	44.4 h	84.6 f	97.9 c	93.8 d

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate). N.D.— none detected under the parameters tested. Means followed by the same superscript letter within a column do not differ significantly (p < 0.05).

. The addition of nopal components alone or in combination with goat manure reduced the concentrations of Fe, Mn, P, K and Ca.

The ratios of Ca/Mg, Mg/K, Ca + Mg/K and Ca/K in the soil were significantly affected by the addition of nopal components alone or in combination with goat manure, as shown in

Table 8. Ca/Mg, Mg/K, Ca + Mg/K and Ca/K ratios in soils after application of treatments.

Variable	Initial	T0	T1	T2	T3	T4	T5	T6	T7
Ca/Mg	1.21	0.81	0.82	0.76	0.88	0.74	0.8	0.81	0.86
Mg/K	4.24	9.57	6.81	7.49	7.09	7.50	6.52	8.89	6.97
Ca + Mg/K	9.35	17.28	12.41	13.15	13.3	13.06	11.72	16.07	12.95
Ca/K	5.12	7.71	5.6	5.67	6.21	5.56	5.20	7.18	5.98

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate.

.

The Ca/Mg, Ca/K and Mg/K ratios in industrial crops such as soybean grain, on average, are 2.26, 9.40 and 4.15, respectively [33], similar to the results of this study. Apparently, the Mg/K ratio is a critical value in some crops where a high level of exchangeable Mg²⁺ is recommended, confirming the results obtained in this study.

3.2. Germination Test

In all treatments carried out in trays, the germination velocity index (GVI) was greater than that in the control sample. As shown in

Table 9. The effects of the presence of nopal components on the velocity index and percentage of germination of carrot and tomato seeds in trays.

Treatment	Germination Velocity Index		Germination Percentage
	Tomato	Carrot	Tomato	Carrot
T0	11.77 ± 0.40 c	14.74 ± 1.61 c	85.51 ± 5.22 b	67.05 ± 3.55 b
T1	17.00 ± 0.45 b	31.50 ± 0.82 a	98.07 ± 2.21 a	95.74 ± 4.08 a
T2	13.86 ± 0.61 c	26.19 ± 2.08 b	84.06 ± 1.45 b	89.15 ± 7.56 a
T3	25.27 ± 1.50 a	31.04 ± 0.34 a	97.58 ± 2.21 a	98.84 ± 1.16 a

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₀—the control substrate. Means followed by the same superscript letter within a column do not differ significantly (p < 0.05).

, the seeds germinated with the addition of nopal (T₃) had the highest GVI, which was 1.1 times greater than that of the control sample (T₀), in both tomato and carrot plants. However, differences in germination percentages were observed at T₃, as the increase in tomato was only 14%, while in carrot, it was 47%. It has been reported that the high water-holding capacity of mucilage allows it to retain water for up to 2 weeks [34]. Therefore, the addition of mucilage in T₃ apparently reduced the effects of stress on the GVI and increased the percentage of germination.

In the soil germination test under dry conditions, only the germination characteristics of the carrot seeds were consistent, showing a significant increase in the two tested parameters, GVI and percentage of germination, with a 1.7-fold increase in T₇ for both parameters, as shown in

Table 10. The effects of the treatments on the velocity index and percentage of germination of carrot and tomato seeds in the soil.

Treatment	Germination Velocity Index		Germination Percentage
	Tomato	Carrot	Tomato	Carrot
T0	3.57 ± 0.40 c	2.14 ± 1.28 h	66.07 ± 14.73 b	28.13 ± 23.11 b
T1	3.60 ± 0.48 b	5.32 ± 1.89 b	64.28 ± 16.50 c	71.88 ± 13.01 ab
T2	2.77 ± 0.35 h	3.17 ± 2.21 e	46.42 ± 12.37 f	59.38 ± 24.21 ab
T3	3.04 ± 0.26 g	2.97 ± 1.87 f	53.57 ± 27.66 e	42.19 ± 14.77 ab
T4	3.13 ± 0.29 f	3.75 ± 1.80 d	64.28 ± 26.08 c	73.44 ± 10.67 a
T5	4.07 ± 0.46 a	4.41 ± 1.78 c	76.78 ± 10.71 a	71.88 ± 23.11 ab
T6	3.34 ± 0.33 d	2.87 ± 1.35 g	64.28 ± 10.71 c	46.88 ± 19.43 ab
T7	3.33 ± 0.17 e	5.76 ± 3.01 a	60.71 ± 14.87 d	76.56 ± 19.35 a

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus manure goat; T₆—solid components of the cladode plus manure goat; T₇—liquid components of the cladode plus manure goat; T₀—the control substrate. Means followed by the same superscript letter within a column do not differ significantly (p < 0.05).

. Apparently, the possible presence of pectin methyl esterase inhibitors (PMEIs) in the treatments in which complete cladodes or liquids of nopal were added had a greater effect on the germination characteristics of tomato seeds, which is why the GVI of tomato increased the germination percentage by only 14% and 16%, respectively.

According to the results, germination in the trays was greater than germination in the soil under dry conditions. This behavior can probably be attributed to the controlled conditions that prevailed for the seeds in the tray germination test. The lack of controlled conditions in the dry-soil germination test affected both the GVI and the germination percentage.

3.3. Resistance to Water Stress

The resistance of tomato and carrot plants to water stress was greater in all treatment groups than in the control group (Figure 1). In tomato plants, 100% cumulative mortality was observed after 55 days of germination with the addition of any component of the nopal and after 50 days in carrot plants, while it was reached after 40 days in the control.

It has been reported that individual species react very differently to water stress. For this reason, a difference of 6 days to reach 100% mortality was observed between tomato plants and carrot plants. However, the tested treatment resulted in decreased mortality in both tomato and carrot plants, apparently due to the mucilaginous components of Opuntia, which improved the water balance by increasing water retention and reducing evapotranspiration [35].

3.4. The Effects of Nopal Addition on the Morphological Traits of the Plants

As shown in

Table 11. The effects of the treatments on the morphological traits of carrot plants.

Treatment	Morphological Traits of Carrot Plants
	Stem Length	Number of Leaves	Leaf Weight	Stem Diameter
T0	21.25 ± 6.25 d	10.13 ± 1.89 a	11.25 ± 3.68 b	11.37 ± 2.53 b
T1	39.76 ± 3.38 ab	12.69 ± 3.40 a	39.06 ± 15.46 a	16.35 ± 1.45 ab
T2	30.61 ± 3.76 bcd	15.13 ± 3.04 a	40.63 ± 22.19 ab	14.21 ± 2.68 ab
T3	39.03 ± 6.77 ab	15.06 ± 2.85 a	38.44 ± 14.63 ab	16.66 ± 3.85 ab
T4	35.65 ± 1.93 abc	11.56 ± 2.39 a	26.25 ± 2.04 ab	13.26 ± 1.63 ab
T5	44.72 ± 3.63 a	14.31 ± 1.78 a	40.63 ± 10.87 ab	16.92 ± 3.84 a
T6	35.32 ± 6.30 abc	13.38 ± 2.59 a	34.06 ± 13.36 ab	15.57 ± 1.74 ab
T7	27.63 ± 1.45 cd	14.25 ± 2.98 a	47.50 ± 16.20 a	20.53 ± 1.77 ab

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate. Means followed by the same superscript within a column do not differ significantly (p < 0.05).

, a significant difference was observed between all treatments for most of the carrot morphological characteristics tested. However, when the nopal component was added to the goat manure, the leaf weight and stem length increased by approximately 3.2 and 1.1 times, respectively, while the number of leaves increased by 48% when only one component of the nopal was added.

Various studies have reported that the addition of organic or biological fertilizers can optimally meet the needs of plants. However, different nutrient sources also affect the release of nutrients and their processing [36]; presumably for this reason, high variability was observed between treatments. On the other hand, the results for most morphological characteristics are in agreement with those of González et al. [37], who indicated that fertilization with goat manure improved the nutritional quality of quinoa grains. The increase in stem length and leaf weight could be due to the effects of the mucilage contained in nopal on nutrient uptake, as it increases the ability of young root segments to capture water and probably helps plants utilize soil resources [38].

As shown in

Table 12. The effects of the treatments on the morphological traits of the tomato plants.

Treatment	Morphological Traits of the Tomato Plants
	Plant Length	Diameter of the Stem	Principal Stems	Radicular Length
T0	WS	WS	WS	WS
T1	68.27 ± 2.89 a	4.17 ± 0.26 a	11.17 ± 1.20 a	24.30 ± 2.44 a
T2	45.73 ± 2.40 b	2.88 ± 0.27 b	8.20 ± 1.13 b	16.52 ± 1.07 b
T3	67.67 ± 6.13 a	4.42 ± 0.11 a	11.78 ±0.69 a	23.90 ± 0.73 a
T4	44.17 ± 1.75 b	2.72 ± 0.05 b	10.33 ± 0.17 b	14.88 ± 0.05 b
T5	65.72 ± 5.72 a	4.51 ± 0.19 a	11.72 ± 0.42 a	24.23 ± 1.54 a
T6	69.47 ± 0.53 a	4.50 ± 0.30 a	11.75 ± 1.04 a	25.94 ± 0.56 a
T7	66.00 ± 3.24 a	3.98 ± 0.08 a	11.83 ± 1.17 a	23.22 ± 0.68 a

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate. WS—without sample. Means followed by the same superscript letter within a column do not differ significantly (p < 0.05).

, compared with the addition of nopal, the addition of goat manure to the substrate did not seem to have any effect on the morphological characteristics of the tomato plants. However, the addition of nopal components and/or goat manure allowed adequate plant development and thus the production of tomatoes, which was not achieved in the control.

The production yield of carrot plants increased 3-fold in response to the addition of the nopal components. However, a synergistic effect was observed in the treatments that also contained goat manure, in which the increase in yield was 3.3-fold for T₅. The higher production yield was the result of individual characteristics, as the nopal-treated carrots had greater individual weight, carrot length and crown length, as shown in

Table 13. The effects of the eight treatments on yield and some agronomic characteristics of carrot plants.

Treatment	Yield (g)	Individual Weight (g)	Carrot Length (cm)	Crown (mm)
T0	275 ± 4.25 g	17.19 ± 4.25 b	5.35 ± 1.21 c	13.76 ± 3.42 b
T1	1000 ± 31.04 c	62.50 ± 31.04 ab	14.39 ± 1.31 ab	18.62 ± 0.80 a
T2	945 ± 25.77 d	59.06 ± 25.77 ab	14.93 ± 3.34 ab	20.67 ± 4.74 a
T3	900 ± 20.64 e	56.25 ± 20.64 ab	14.04 ± 2.14 ab	19.42 ± 2.28 a
T4	709 ± 25.16 f	44.31 ± 25.16 ab	12.31 ± 2.16 b	17.36 ± 3.29 a
T5	1180 ± 11.77 a	73.75 ± 11.77 a	15.19 ± 2.14 ab	23.15 ± 1.39 a
T6	945 ± 27.53 d	59.06 ± 27.53 ab	17.94 ± 2.11 a	22.50 ± 6.33 a
T7	1090 ± 20.14 b	68.13 ± 20.14 ab	13.18 ± 1.99 ab	22.99 ± 6.17 a

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate. Means followed by the same superscript letter within a column do not differ significantly (p < 0.05).

.

With respect to tomato fruit quality, in the control, no tomatoes were produced, as shown in

Table 14. The effects of the eight treatments on yield and some agronomic characteristics of tomatoes.

Treatment	Number of fruits	Yield (g)	Individual Weight (g)	Polar Diameter (cm)	Equatorial Diameter (cm)
T0
T1	8.71 ± 0.30 a	3992 ± 7.97 a	95.63 ± 3.14 a	7.31 ± 0.30 b	12.47 ± 0.88 a
T2	4.08 ± 0.26 c	3992 ± 7.97 a	64.49 ± 8.18 b	7.81 ± 0.13 b	13.77 ± 0.69 a
T3	8.25 ± 0.17 a	3145 ± 5.53 b	44.70 ± 1.04 c	9.56 ± 0.68 a	16.24 ± 0.13 a
T4	6.51 ± 0.50 ab	1486 ± 4.03 d	41.77 ± 1.37 c	7.14 ± 0.44 b	12.91 ± 0.13 a
T5	7.12 ± 0.63 ab	2482 ± 6.32 c	45.47 ± 5.32 c	7.09 ± 0.29 b	12.47 ± 0.53 a
T6	4.17 ± 0.36 c	2412 ± 11.77 c	52.59 ± 3.48 c	7.52 ± 0.22 b	12.51 ± 0.54 a
T7	5.62 ± 0.39 bc	1922 ± 6.97 c	46.37 ± 8.17 c	7.67 ± 0.53 b	12.70 ± 0.89 a

T₁—complete cladode; T₂—solid components of the cladode; T₃—liquid components of the cladode; T₄—only goat manure; T₅—complete cladode plus goat manure; T₆—solid components of the cladode plus goat manure; T₇—liquid components of the cladode plus goat manure; T₀—the control substrate. Means followed by the same superscript letter within a column do not differ significantly (p < 0.05).

. The plants treated only with whole cladodes and solid components produced more fruits; however, when goat manure was added, no significant changes were observed in the combination of whole cladodes and goat manure.

Various biofertilizers, vermicomposts, photosynthesis agents and microorganisms have been tested in the production of tomatoes and carrots, with positive results obtained [10,39]. However, as in this study, internal and external factors can affect the final characteristics of tomatoes and carrots when biomanures are used in addition to biofertilizers [40,41,42]. For this reason, the morphological characteristics of the two studied horticultural crop species, tomato and carrot, vary.

4. Conclusions

One of the most important results of this study was the observation that the components of nopal have no toxic effects on the germination and development of tomato and carrot plants, even if they are not composted. The addition of nopal components increased the resistance of the tomato plants to water stress within 15 days, but for the carrot plants, the increase was only 10 days. The addition of nopal components had a positive effect not only during germination but also during plant development and production, which increased 3.3-fold in carrot plants compared to the control, while in tomato plants, it promoted plant survival and achieved production of up to 3.9 kg per plant. When the nopal component was added to the goat manure, the leaf weight and stem length were approximately 3.2 and 1.1 times greater than those in the control, respectively. However, while an increase in yield was achieved in the carrot plants, the same effect was not observed in the tomato plants. With respect to the yield increase in the carrot plants, the treatments with whole nopal had greater yields (T₁ and T₅), but in the tomato plants, the best treatments for yield increase were those in which only the nopal components were added (T₁, T₂ and T₃).