ORIGINAL ARTICLE

Comparison of Three Variants of Substrate Preparation Used in the Propagation of Cocoa Standards

Ing. Diana Aracelly-López^{1  *} 

Ing. Luis Fernando Plaza-Avellán¹ 

Ing. Betty Janeth Rivadeneira-Moreira¹ 

Ing. Flor María Párraga-Palacios¹ 

Dr.C. Miguel Herrera-Suárez¹ 

¹Universidad Técnica de Manabí (UTM), Instituto de Postgrado, Portoviejo, Manabí, Ecuador.

ABSTRACT

This research was conducted to compare three variants of substrate preparation used in mass propagation of cocoa (Theobroma cacao L.) in nursery conditions. Three treatments were studied: T1-manual mixing with shovel, T2-mechanized mixing with motorized cultivator and T3-mechanized with mixer. Evaluations were made of the physical-chemical characteristics of the substrate, compaction, cotyledon height, number of leaves per plant, stem diameter, plant height at 20, 40 and 60 days, fresh weight of the plant and root and root length. The results showed that there are no statistically significant differences between the treatments, i.e. the method of preparation of the substrate does not have a direct incidence on the agronomic response of the plant, in the conditions and period investigated. The physical-chemical analysis of the mixed substrates showed, in all three cases, a sandy loam texture with an apparent density ranging from 1,17 to 1,19 g/cm³, as well as an organic matter content ranging from 1,9 to 3,2 %. The average pH was 5.9. No statistically significant differences were found between the treatments in terms of effects on the vegetative development of the plant throughout the development cycle evaluated. The economic analysis showed that it is more profitable to use mechanized technology if it is used in mass propagation centers, since the productivity of the machines is three (T2) and four times (T3) more than the manual variant.

Keywords: substrate; cocoa seedlings; substrate mix

INTRODUCTION

Theobroma cacao L. is a species native to the South American Amazon, whose geographical origin is located within a vast region shared by what is currently Ecuador, Colombia and Peru. Despite its South American origin, it was in Central America that European colonizers discovered the uses of the fruit and its subsequent use as a consumer drink.

At present, 68% of world cocoa production is produced in Africa, with Côte d'Ivoire as the leading country, followed by Ghana, Nigeria and Cameroon. Central and South American countries account for 15% of world cocoa production, with Brazil and Ecuador as the main suppliers. The rest is grown in Asia and Oceania, where Indonesia and Malaysia are the leading producers in this region. This concentration of production corresponds to a narrow strip on the equator, considering the climate and physical requirements of the cocoa tree (^{Quinteros & Díaz, 2004}).

For its part, the Republic of Ecuador has gone from producing around 119,000 MT in 2007 to producing 374,000 MT by the end of 2017 (^{MAG, 2017}). Of this total production, 75% is so far classified as fine aroma cocoa and represents more than 50% of the fine aroma cocoa traded worldwide annually.

The quality that distinguishes Ecuador's fine aroma cacao is due to a unique sensory richness produced by a variety known as Nacional and according to which work is generated for around 100,000 Ecuadorian families dedicated to its cultivation, 95% corresponding to plantations of less than 10 hectares.

In Ecuador, the planting material recommended for mass propagation is propagated by cloning, using the grafting method. The procedure established for the grafting contemplates on the one hand the selection and use of a plant called "Pattern" and on the other hand the "Clone" itself, this last one recognized as a "Vareta Porta Yemas" which comes from clonal gardens specifically destined for the effect of propagation.

Considering the growth rate of cocoa area in the Republic of Ecuador, the need for clonal plants currently exceeds millions. To cover this growing demand, there are many nurseries in different parts of the Ecuadorian territory dedicated to the propagation and sale of plants, but the great majority of them are not registered or endorsed by the control body "AGROCALIDAD" and do not meet the minimum quality standards required for this purpose.

Experience indicates that among the most important cares to be considered in the establishment of a cocoa nursery is the type of substrate to be used, which is the main factor in the success or failure of plant production.

The substrate is produced from the mixture of soil, sand and organic matter that is used to fill the covers (bags) and it is the medium where it is sown the seed that will become the cocoa pattern as an essential part of the grafting process. That substrate is the physical support of the plant and protects the roots during the first months of development and during transport to the planting place.

A good substrate is one whose composition consists of 50% soil, 25% organic matter (preferably worm compost) and 25% sand.

Despite the above, in Ecuador people dedicated to the multiplication of plants generally use only soil, since this element is obtained from their own land or is acquired at a relatively low cost. In a few cases, mixing with sand is known; both the soil and the sand are mixed manually using the shovel as a tool. Such mixtures are made on a trial basis only.

One of the main problems detected during the elaboration of substrates is the homogenization of the mixed elements and the laboriousness of the process when it is done manually. In conditions of massive production as in the big nurseries, mechanized alternatives are needed for the preparation of the referred substrate with the mixture quality required and the shortening of the preparation times.

Taking these aspects into account, the aim of this work is to compare three variants of substrate preparation used in mass propagation of cocoa in nursery conditions.

METHODS

Location of the investigation. The present research was developed in its field phase, between May and August 2018, in the areas of the nursery of Pichilingue Tropical Experimental Station of the National Institute of Agricultural Research (INIAP), located at km 5.5 of Quevedo-El Empalme road, Los Rios Province, between the geographical coordinates 01º 06' south latitude and 79º 28' west longitude, at an altitude of 75 m.a.s.l.

Experimental design and statistical analysis. The research was conducted using a completely randomized design with three treatments and five replicates. One hundred cocoa plants under greenhouse conditions are considered as an experimental unit.

Three treatments were evaluated that consist of different substrate preparation technologies for planting cocoa rootstocks. The treatments studied were: T1-manual mixing with shovel, T2-mechanized mixing with motorized cultivator, and T3-mechanized with mixer.

The design specifications of experiments are shown in Table 1.

TABLE 1 Design specifications 

Number of treatments:	3
Number of repetitions:	5
Number of experimental units:	15
Number of plants per experimental unit:	100
Number of plants per treatment:	300
Number of plans per repeat:	500
Plants evaluated per experimental unit:	25
Total plants evaluated per treatment:	125
Total number of plants evaluated per repeat:	75
Total number of plants assessed in the trial:	375
Total number of plants in the trial:	1500

The mixing of the materials that make up the substrate in each of the treatments involved mixing in 3:1:1 ratio of soil, sand and balsa wood sawdust, respectively.

For each treatment, 500 bags were filled, which were organized in 5 rows and 20 bags per column, thus forming blocks of 100 bags each row. The bags were watered for 30 minutes and then the National type cocoa seeds were planted with the materials recommended for rootstocks (EET 399, EET400, POUND 12, IMC 67 among others), which will become rootstocks.

T1-Manual mixing. The shovel was used as a tool to turn and mix the materials homogeneously (Figure 1a).

T2-Mixed Mechanized with Motorized Cultivator. For the homogenization of the substrate, three passes were made with a self-propelled, single-axle, 8.3 HP Grillo brand cultivator (Figure 1b). The working device is an adjustable cutter with 4 blades.

T3-Mechanized with mixer. The mixing work was carried out for 10 min with a conventional concrete mixer with a capacity of 9 m³ and a power demand of 13 HP, (Figure 1c).

FIGURE 1 Substrate preparation variants. a) T1 - manual mixing with shovel, b) T2 - mechanized mixing with motorized cultivator, c) T3 - mechanized with mixer. 

Physical-chemical characterization of the substrates. Samples of the substrates mixed in each treatment were taken and transferred to the soil and water analysis laboratory at INIAP's Pichilingue Experimental Station. The textural classification, bulk density, organic matter, pH, electrical conductivity, macro and micro essential elements were determined.

Height of the cotyledon. Measurements were taken with a measuring tape (flexometer) on 25 plants at random for each experimental unit, considering the distance from the root collar to the appearance of the cotyledon on each plant, at 20, 40 and 60 days after planting.

Number of leaves per plant. Leaves were counted on 25 plants taken at random in each experimental unit. This procedure was performed at 20, 40 and 60 days after sowing.

Stem diameter. This variable was measured with a caliper at half the distance from the root collar to the appearance of the cotyledon, on 25 plants at random in each experimental unit. This process was repeated 20, 40 and 60 days after sowing.

Height of plants. It was measured with the measuring tape or flexometer in each of the 25 plants taken at random by each experimental unit, at 20, 40 and 60 days after sowing.

Fresh plant dough. It was evaluated 60 days after planting. To do this, the 125 plants were separated from each treatment, they were individually removed from their sheaths and then the soil was washed away from the roots, avoiding their destruction. Finally, a cutting tool is used to make a cut at the height of the neck of the root and a precision scale is used to determine the mass of the aerial part of the plant.

Fresh root weight. For the evaluation of this variable the same plants utilized for the previous variable were used, i.e. on the same day, the mass of the cut root part was determined.

Length of the root. For each of the roots that were freshly weighed, the main root was measured using the measuring tape.

Economic analysis. For each treatment under study, an economic analysis was made considering the respective production costs of each technology used for the mixing of substrates. It assumed a production of 1000 plants and a sales price of $ 0.35 per plant. The following economic indicators were calculated:

• Gross income = plants produced * sales price

• Net income = gross income - cost of production

• B/C= Gross income/Total cost of production

• Profitability (%) = net income/cost of production*100

RESULTS AND DISCUSSION

Physical-chemical characterization of the substrates. The results of the physical analyses of the substrates show (Table 2) that all treatments present a sandy loam textural class, with a content ranging from 56 to 66% sand, 30 to 34% silt, and 4 to 10% clay.

These results show that the physical and chemical characteristics of the prepared substrates do not depend on the technology used in their preparation, but on the mixing ratios and the materials used in the mixtures. In this respect, previous research has shown that the physical composition of the substrates varies according to the materials used and the proportions of the mixtures to be made (^{Baudoin et al., 2002}).

TABLE 2 Physical properties of the substrate 

Treatments	Texture (%)			Textural Class	Apparent density g/cm3
	Sand	Silt	Clay
T1	66	30	4	Sandy loam	1,17
T2	56	34	10	Sandy loam	1,18
T3	64	30	6	Sandy loam	1,19

Similarly, no statistically significant differences were found between the densities of the substrate reached in each of the treatments, although the highest values were reached in the substrates prepared with mechanized variants (Table 2).

^{Bunt (2012)}, pointed out that the quality of the seedlings depends on the type of substrate where they grow, particularly, on their physical-chemical characteristics because the development and functioning of the roots are directly linked to the conditions of aeration, water content, in addition to having a direct influence on the availability of nutrients.

^{González et al. (2000)}, point out that knowledge of the substrate is necessary to optimize the production of plants in nurseries, as well as to reduce and avoid the depletion of non-renewable resources such as the soil, which has been the main substrate in many nursery practices.

The determination of chemical composition of the substrates showed (Table 3), that the pH is similar in all treatments in study, with a value of 5.9, considered moderately acidic.

TABLE 3 Results of chemical analysis of the substrate 

Treatments	pH	E.C. (dS/m)	M.O. (%)	ppm		meq/100ml			ppm
				NH4	P	K	Ca	Mg	S	Zn	Cu	Fe	Mn	B
Shovel	5.9 MeAc	36 DK	1,9 B	12 B	48 A	0,71 A	12 A	1,2 M	7 B	2,6 M	5,3 A	189 A	9,1 M	1,01 A
Motorized plough	5.9 MeAc	32 DK	3,2 M	11 B	51 A	0,78 A	12 A	1,2 M	9 B	2,9 M	6,1 A	205 A	10 M	0,72 M
Mixer	5.9 MeAc	36 DK	3,2 M	11 B	48 A	0,75 A	12 A	1,2 M	7 B	2,7 M	5,8 A	195 A	9,3 M	0,35 B

MeAc = Medium Acid; NS = Non-Saline; A = High; M = Medium; B = Low.

Regarding electrical conductivity, the treatment (T2) of the motorized cultivator presented the lowest value with 32 dS/m, while the shovel and mixer treatments presented the highest value (36 dS/m), although these are within the range of non-saline substrate.

These results coincide with those reported by ^{Landis et al. (2000)}, ^{Abad et al. (2001)}, ^{Baudoin et al. (2002)} and ^{Landis & Morgan (2009)}, who indicate that the pH of the substrate should be slightly acidic (5.5-6.3), so that the nutrients are available, and the electrical conductivity low, so that there are no toxicity problems and that the producer can manage the concentrations of mineral nutrients.

In this regard, several authors ^{Handreck et al. (2002)} and ^{Landis & Morgan (2009)}, state that among the main chemical properties responsible for the quality of the substrate are pH and electrical conductivity.

When comparing the organic matter content of the power tiller (T2) and mixer (T3) treatments, it is evident that these were superior (Mo=3.2 %) compared to the shovel treatment which presented a low content (Mo=1.9 %).

For ^{Villegas et al. (2017)}, organic matter is an active component and its incorporation with inorganic substrates improves the pore space, increases moisture retention and cation exchange capacity. Therefore, based on the results of this experimental phase, a direct benefit of the mechanized mixing process at the nursery level can be stated.

With regard to the content of essential elements for the plant, the treatments under study presented similar results for the vast majority of elements, for example: high content of phosphorus (P), potassium (K), calcium (Ca), iron (Fe) and copper (Cu), an average content of magnesium (Mg), zinc (Zn) and manganese (Mn), low content of nitrogen and Sulphur (S), while the only exception is Boron (B) whose content was different in each of the treatments (shovel = high, power tiller = medium and mixer = low). These Boron variation results are most probably directly correlated to the organic matter used in the mixture (sawdust) for the preparation of the substrate, whose results were also variable depending on the treatment used.

In this regard, ^{Abad et al. (2001)} and ^{Varela & Martínez (2013)} state that the use of organic components in the preparation of substrate has advantages as a storehouse of nutrients, especially nitrogen, phosphorus, potassium, sulfur and micronutrients and slowly releases them, resulting in a more sustainable and economic agriculture in terms of work, fertilizer input and soil degradation.

Compaction of the substrate. In Table 4, the averages corresponding to the compaction of the substrates are shown, whose respective analysis of variance did not reflect statistical significance, highlighting that the treatment with shovel generated a greater compaction with 1.54±0.83 kg/cm², while the mechanized variants mixer and motorized cultivator registered values of 1.15±1.20 and 1.06±0.60 kg/cm².

In this regard, ^{Osorio et al. (2017)} found that when resistance to soil penetration is greater than 0.7 kg/cm², longitudinal growth of the taproot stops and affects the accumulation of aerial biomass, decreasing the vigor of the seedlings. ^{Bengough et al. (2011)}, on the other hand, point out that resistance to penetration greater than 20.4 kg/cm² and porosity less than 10% are considered critical limits for root elongation.

TABLE 4 Compaction of the substrate inside the bag 

Treatments	Soil compaction (kg/cm^2) *
T1: Shovel	1,54±0,83 a
T2: Motorized cultivator	1,06±0,60 a
T3: Mixer	1,15±1,20 a
Average	1,25
Variance	0,71
error	0,83
CV (%)	72,89

*Averages with the same letter do not differ statistically according to Tukey's test (p>0.05)

Cotyledon height. As shown in Table 5, the mean cotyledon height at 20, 40 and 60 days, according to the analysis of variance in this variable, did not show significant statistical differences (p<0.05) among the treatments studied at 20, 40 and 60 days, with a coefficient of variation of 6.6%, 7.04% and 6.33%, respectively.

The highest cotyledon height at 20, 40 and 60 days was recorded by the mixer treatment with averages of 5.37±0.25, 6.12±0.47 and 6.71±0.41, however, these values did not differ significantly from the other treatments and substrate preparation. These results show that the substrate produced by the different technologies does not influence the development of the cotyledon.

TABLE 5 Cotyledon height in cocoa substrate patterns with different preparation variants 

Treatments	Height of cotyledon (cm)
	20 days	40 days	60 days
T1: Shovel	5,21±0,15 a	6,10±0,23 a	6,56±0,27 a
T2: Motorized cultivator	5,11±0,52 a	5,90±0,52 a	6,48±0,53 a
T3: Mixer	5,37±0,25 a	6,12±0,47 a	6,71±0,41 a
Average	5,23	6,04	6,58
Variance	0,11	0,16	0,15
error	0,12	0,18	0,17
CV (%)	6,60	7,04	6,33

*Averages with the same letter in each data set do not differ statistically according to Tukey's test (p>0.05)

Number of sheets. In Table 6, the averages corresponding to the number of leaves per plant are presented. According to the analysis of variance, the treatments studied did not reach significant differences at 20, 40 and 60 days, with coefficients of variation of 5.71, 8.15 and 5.65%, respectively. The highest average at 20 days was presented in the shovel treatment with 4.06±0.22 leaves, which varied at 40 and 60 days, since it was the power tiller treatment that presented the highest number of leaves with 5.61±0.35 and 6.91±0.43, respectively.

These results are consistent with those reported by ^{INIFAP (2011)} which states that a cocoa plantlet should have, approximately, 5 to 10 turgid and well-developed leaves. ^{Loor et al. (2016)} state that cocoa plants in nursery conditions should have between 7 and 11 leaves, formed and of an intense green color. Under this last technical consideration, the mechanized treatments would be contributing in a direct way for an improvement of the quality of the standard in appropriate age to be used in the grafting processes.

TABLE 6 Number of leaves per plant 

Treatments	Number of leaves per plant
	20 days	40 days	60 days
T1: Shovel	4,03±0,12 a	5,53±0,41 a	7,1±0,4 a
T2: Motorized cultivator	4,05±0,31 a	5,61±0,35 a	7,48±0,39 a
T3: Mixer	4,06±0,22 a	5,36±0,56 a	6,91±0,43 a
Average	4,05	5,50	7,16
Variance	0,04	0,17	0,19
error	0,05	0,20	0,16
CV (%)	5,71	8,15	5,65

*Averages with the same letter in each data set do not differ statistically according to Tukey's test (p>0.05)

Stem diameter. Table 7 shows the averages for stem diameter at 20, 40 and 60 days after sowing. According to the analysis of variance, none of the treatments reached statistical significance, being 4.09, 3.35 and 4.35%, the respective coefficients of variation.

TABLE 7 Stem diameter in cocoa substrate patterns with different preparation variants 

Treatments	Stem diameter (mm)*
	20 days	40 days	60 days
T1: Shovel	3,14±0,07 a	3,64±0,04 a	4,37±0,05 a
T2: Motorized cultivator	3,24±0,14 a	3,72±0,15 a	4,54±0,23 a
T3: Mixer	3,19±0,16 a	3,69±0,14 a	4,44±0,24 a
Average	3,19	3,68	4,45
Variance	0,02	0,01	0,03
error	0,02	0,02	0,04
CV (%)	4,09	3,35	4,35

*Averages with the same letter in each data set do not differ statistically according to Tukey's test (p>0.05)

The preparation with a motorized cultivator allowed obtaining flatter stems with greater diameters after 20 days (3.24±0.14 mm), without differing statistically from the other treatments, in such a way that with the mixer an average diameter of 3.19±0.16 mm was registered and with the shovel, a diameter of 3.14±0.07 mm. Similar behavior was observed at 40 and 60 days, with the power tiller producing plants with thicker stems, with averages of 3.72±0.15 and 4.54±0.23 cm, respectively.

Indications from ^{INIFAP (2011)} show that the stem thickness of cocoa seedlings in the nursery should be greater than 1 cm.

Height of plants. The averages of plant height at 20, 40 and 60 days are presented in Table 8. According to the results of the statistical analysis, no statistically significant differences (p<0.05) were found between the treatments under study at 20, 40 and 60 days, the coefficient of variation was 5.28%, 5.13% and 5.42%, respectively.

TABLE 8 Height of plants in patterns 

Treatments	Height of plants (cm)*
	20 days	40 days	60 days
T1: Shovel	10,89±0,64 a	19,40±0,46 a	22,94±0,36 a
T2: Motorized cultivator	10,71±0,49 a	18,97±1,03 a	22,99±1,58 a
T3: Mixer	11,26±0,60 a	19,07±1,27 a	22,58±1,40 a
Average	10,95	19,15	22,84
Variance	0,32	0,81	1,26
error	0,34	0,97	1,53
CV (%)	5,28	5,13	5,42

*Averages with the same letter in each data set do not differ statistically according to Tukey's test (p>0.05)

Days after sowing the seeds, the tallest plants were observed in the treatment with mixer (11.26±0.60 cm), value that did not differ significantly from the two remaining treatments, while, at 40 days, the treatment corresponding to the manual mixing (T1) registered greater height of plants (19.40±0.46), finding that there were no statistically significant differences with the rest of the treatments. Finally, after 60 days, the treatment with motorized cultivator (T2), was the one that registered the highest plants with 22.99±1.58 cm.

These results coincide with those reported by ^{INIFAP (2011)} in similar studies where it was determined that the height of cocoa plants in the nursery can range from 20 to 35 cm, in plants of more than 50 days. In this regard, ^{FHIA (2017)}, indicates that plants intended as patterns in cocoa should reach an average height of 50 cm.

Fresh biomass. In Table 9, the values of fresh plant weight and fresh root weight are presented in response to the substrate mixing technologies.

TABLE 9 Fresh biomass from cocoa patterns 

Treatments	Fresh biomass (g)*
	Fresh plant weight	Fresh root weight
T1: Shovel	8,64±0,89 a	2,21±0,37 a
T2: Motorized cultivator	8,32±0,80 a	1,97±0,43 a
T3: Mixer	7,76±1,09 a	2,08±0,44 a
Average	8,24	2,09
Variance	0,83	0,15
error	0,87	0,17
CV (%)	11,34	19,97

*Averages with the same letter in each data set do not differ statistically according to Tukey's test (p>0.05)

The results of the analysis of variance do not show significant statistical differences (p<0.05) among the treatments under study for the variables fresh plant weight and fresh root weight and the coefficient of variation was 11.34% and 19.97%, respectively.

The mixer treatment presented the highest average fresh plant weight with 8.64±0.89 g, as well as higher fresh root weight (2.21±0.37 g), values that did not present significant differences with respect to the two other treatments.

In this regard, ^{Mokany et al. (2006)}, found that the relationship between root and aerial biomass is significantly affected by climate and soil factors.

Root length. The roots of cocoa reached an average length of 16.73±0.95 cm (Table 10). The statistical analysis showed that there were no statistically significant differences between the sizes of the roots in each treatment, although the longest roots (16.73±1.30 cm) were recorded in the treatment (T3), where the substrate was mixed with the help of the mixer. This is because the substrate of this treatment presents a medium compaction, higher organic matter content, and a better clay content.

In this regard, ^{Alvarenga & Cruz (2003)}, indicate that the ability of plants to explore the soil depends largely on the distribution of roots in the profile and the characteristics of the soil (^{Ramírez, 2016}).

According to ^{Freddi et al. (2006)}, root growth is inversely related to resistance to soil penetration, an aspect that is consistent with that reported by ^{Osorio et al. (2017)}, in substrates used for cocoa planting.

TABLE 10 Root length of cocoa patterns 

Treatments	Root length (cm)*
T1: Shovel	16,73±1,30 16,73±1,30 a
T2: Motorized cultivator	16,32±1,14 a
T3: Mixer	15,91±0,39 a
Average	16,32
Variance	0,95
error	1,05
CV (%)	6,27

*Averages with the same letter do not differ statistically according to Tukey's test (p>0.05)

Economic analysis. In Table 11, the economic analysis of the treatments studied is presented, considering a production volume of 1000 plants, at a selling price of $ 0.35 each plant, which generates a gross income of $ 350.00. The greatest economic benefit was seen in preparing the substrate with a shovel, which reflected a net income of $139.38 with a B/C ratio of 1.66, indicating that for every dollar invested a profit of $0.66 is obtained, i.e. a 66% return. It is worth mentioning that the motor cultivator and the mixer registered a profitability of 63 and 62%, respectively.

TABLE 11 Economic analysis of results 

Economic variables	Treatments
	T1: Shovel	T2: Motor cultivator	T3: Mixer
Number of plants produced	1000	1000	1000
Cost of sale ($)	0,35	0,35	0,35
Gross income ($)	350,00	350,00	350,00
Cost of production ($)	210,62	214,42	216,31
Unit cost of production ($)	0,21	0,21	0,22
Net income ($)	139,38	135,58	133,69
Net unit income ($)	0,14	0,14	0,13
B/C	1,66	1,63	1,62
Profitability (%)	66	63	62

The results of the economic analysis show that given the low cost of labor in the case of manual mixing and the need to make an investment for mechanized mixing, traditional mixing, i.e. manual mixing with the aid of a shovel, becomes more profitable. However, this variant is only sustainable for small-scale pattern production. In the case of intensive production or large nurseries, where it is necessary to ensure the filling of a large number of bags in a short period of time, it becomes more feasible to use mechanized technologies, due to the increase in productivity.

CONCLUSIONS

• The results of the experimental investigations demonstrated that there were no statistically significant differences among the treatments investigated in terms of the method of preparation of the substrate, since these did not have a direct incidence on the agronomic response of the plant, during the period of time of development of the patterns, in the conditions investigated.

• The physical-chemical analysis of the substrates obtained during the mixing process showed great uniformity for the three treatments investigated, showing a substrate with a sandy loam texture and apparent density of 1.17 to 1.19 g/cm³, an organic matter content of 1.9 to 3.2 % and pH 5.9, values that are estimated to be adequate for the development of cocoa standards.

• No statistically significant differences were found between the treatments, in terms of effects on the vegetative development of the plant throughout the development cycle evaluated.

• The economic analysis showed that over time, it becomes more profitable to use mechanized technologies as long as they are being used in mass or commercial propagation centers because the productivity of the machines is much higher than the manual mixing technology (shovel).

• The mechanized technologies were three to four times more efficient than the manual one, being the mixer variant (T3) the most productive one, allowing to mix, in the same unit of time, four times more amount of substrate.

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⁷The mention of trademarks of specific equipment, instruments or materials is for identification purposes, there being no promotional commitment in relation to them, neither by the authors nor by the publisher.

Received: November 13, 2019; Accepted: June 14, 2020

^*Author for correspondence: Diana Aracelly-López, e-mail: [e-mail]

Diana Aracelly-López, Mg. Ingeniería Agrícola, Estudiante Programa de Maestría en Ingeniería Agrícola, Instituto de Postgrado. Universidad Técnica de Manabí. Analista en Producción de semilla, Departamento de Producción, Instituto Nacional de Investigaciones Agropecuarias. e-mail: [e-mail]

Luis Fernando Plaza-Avellán, Mg. Ingeniería Agrícola, Estudiante Programa de Maestría en Ingeniería Agrícola, Instituto de Postgrado. Universidad Técnica de Manabí. Investigador Agregado 1, Programa Nacional de Cacao y Café, Instituto Nacional de Investigaciones Agropecuarias. e-mail: [e-mail]

Betty Janeth Rivadeneira-Moreira, Mg. Ingeniería Agrícola, Estudiante Programa de Maestría en Ingeniería Agrícola, Instituto de Postgrado. Universidad Técnica de Manabí. Investigador Agropecuario 1, Departamento de Suelos y Aguas, Instituto Nacional de Investigaciones Agropecuarias. e-mail: [e-mail]

Flor María Párraga-Palacios, Mg. Ingeniería Agrícola, Estudiante Programa de Maestría en Ingeniería Agrícola, Instituto de postgrado. Universidad Técnica de Manabí, e-mail: [e-mail]

Miguel Herrera-Suárez, Profesor Titular, Departamento de Mecánica, Facultad de Ciencias Matemáticas, Físicas, y Químicas. Universidad Técnica de Manabí. Coordinador de Maestrías, Instituto de Postgrado Universidad Técnica de Manabí. e-mail: [e-mail]

The authors of this work declare no conflict of interests.