PROJECT, DESIGN AND MANAGEMENT ISSN: 2683-1597

How to cite this article:

Orellana Tobar, S. A. & Anaya Hernández, A. (2021). Effect of Eichhornia crassipes compost on the quality of Theobroma cacao nursery plants. Project, Design and Management, 3(1), 73-88. doi: 10.29314/pdm.v3i1.612

Samuel Alfredo Orellana Tobar
Universidad Internacional Iberoamericana (México)
oretobar2011@hotmail.com

Armando Anaya Hernández
Universidad Internacional Iberoamericana (México)
armando.anaya@unini.edu.mx · https://orcid.org/0000-0003-3229-0930

Receipt date: 03/31/2021 / Revision date: 04/20/2021 / Acceptance date: 06/15/2021

Introduction

Water hyacinth (E. crassipes) is an aquatic plant that grows rapidly in water reservoirs (Alvarado, 2013). It is considered a perennial aquatic weed (Madsen and Robles, n.d.), and ranked among the 100 most harmful invasive alien species in the world (Lowe et al., 2004). According to the Food and Agriculture Organization of the United Nations (FAO, 1996), E. crassipes globally causes more serious and widespread problems than any other floating aquatic weed. Rzedowski and Rzedowski (2005) mention that E. crassipes spreads in such a way that it covers the mirrors of canals and other water reservoirs. Its abundance and volume in these bodies of water makes fishing and navigation impossible. According to Barrett and Forno (1982), the origin of E. crassipes seems to be the Brazilian Amazon with natural spread to other areas of the South American continent and introduced by human action to Central America and the Caribbean. The Aquatic Ecosystem Restoration Foundation (AERF, 2014), indicates that E. crassipes has been widely introduced in all tropical regions of the world, most recently in Lake Victoria, East Africa.

In El Salvador, the Cerrón Grande reservoir (with geographical coordinates 14° 03" N and 89° 04" W), constitutes the largest continental freshwater body (Ministry of Environment and Natural Resources [MARN], 2016), with a covered area of 135 km², built for the Cerrón Grande Hydroelectric Power Plant dam, with a nominal capacity of 135 MW, and an average annual generation of 488 GWh (Hydroelectric Executive Commission of Río Lempa [CEL], n.d.). One of the preponderant problems in the Cerrón Grande reservoir is the presence and expansion of E. crassipes, which affects various economic sectors such as the fishing industry, tourism, and navigation (Alas, R. March 25, 2016). Also, it could affect the turbines for hydroelectric generation of the Cerrón Grande dam ("Endangered natural treasures, Cerrón Grande reservoir", 2016). MARN (2019) calculated a coverage of 3,000 hectares of E. crassipes, which is equivalent to 22.22% of the reservoir.

Sonter et al. (2018) mention that compost has recently gained acceptance for integrated solid waste and aquatic weed management, labeled as an environmentally friendly product and a sustainable solution for urban waste and aquatic weed management. In this regard, Mashavira et al. (2015), evaluated the effect of E. crassipes on tomato (Lycopersicon esculentum), on growth attributes, yield potential, and the accumulation of heavy metal levels of lead (Pb), copper (Cu), nickel (Ni), and zinc (Zn) in tomato fruit; while Enriquez (2013), studied the effect of compost based on Eichhornia crassipes on lettuce "Lactuca sativa," on the variables survival, yield in weight (kg), lettuce head diameter and concentration of the heavy metals, lead (Pb) and arsenic (As). As part of the control of E. crassipes in the Cerrón Grande reservoir, in the period from November 2019 to March 2020, 17.34 hectares were manually and mechanically harvested using E. crassipes harvesting barges (CEL, 2020). The Local Economic Development Agency and the Environmental Investment Fund of El Salvador (ADEL-FIAES, 2014) proposed making compost from E. crassipes plants extracted from the Cerrón Grande reservoir as one of the alternatives for its sustainable use and management.

In this context, this study was developed by preparing compost of E. crassipes from the Cerrón Grande reservoir, and its effect on the quality of cocoa plants (Theobroma cacao) in the nursery stage was evaluated. T. cacao is one of the species with high ecological and economic potential that CEL produces in the forest nurseries of its hydroelectric power plants to reforest the Lempa River basin. According to the Ministry of Agriculture and Livestock (MAG, 2018), due to the socio-environmental importance that this crop represents, in El Salvador, there is a "policy for the development of the cocoa chain." Therefore, the production of quality T. cacao plants in nurseries is essential for the success of the plantation.

According to Arteaga et al. (2003) the type of soil or substrate used in plant production is one of the factors that most influences the quality and cost of plant production in nurseries, so it is necessary to have alternatives to reduce costs, guaranteeing a certain plant quality. Prieto (2004), points out that an appropriate nursery process requires cultural practices related to substrates, containers, fertilizers, mycorrhizae, irrigation, prevention and control of pests and diseases.

Plant quality depends on the genetic characteristics of the germplasm and the techniques used for its reproduction (Prieto et al., 2009). The parameters height and diameter are considered estimators of plant performance after planting (Mexal and Landis, 1990) and can be easily quantified (Birchler et al., 1998). In addition, morphological attributes such as the slenderness index, which relates plant height and diameter, the ratio of the dry weight of the aerial and root parts, and the Dickson quality index, which is calculated by the ratio between the total dry weight of the plant and the sum of the slenderness index and the aerial part-root part ratio (Navarro et al. , 2006, Birchler et al., 1998, Dickson et al., 1960, cited by Mateo-Sánchez et al., 2011), are also used.

The objectives of the research were to determine the effect of compost from E. crassipes plants extracted from the Cerrón Grande reservoir on the quality of T. cacao plants at the nursery stage, through the parameters of plant height, diameter, slenderness index, ratio of the dry weight of the aerial part, and dry weight of the root part (PSa/PSr), as well as the Dickson Quality Index (DQI); in addition, to determine the percentages of E. crassipes compost most appropriate to mix with soil for T. cacao production at the nursery stage and finally, to evaluate the levels of heavy metals such as As, Pb ,and Hg in fresh E. crassipes plants, in the compost obtained, and in the T. cacao plants to analyze the existence of translocation of these metals.

Method

The extraction of E. crassipes plants from the Cerrón Grande reservoir was carried out on December 06 and 07, 2018, in the Santa Teresa canton, municipality of Potonico, department of Chalatenango, at the location coordinates 13°57'48.10" N and 88°54'36.51" W, at a distance of 3.0 km in a northwest direction from the Cerrón Grande Hydroelectric Power Plant. For its extraction, quadrats of 1 m long x 1 m wide (1 m²) were made with PVC pipes of 1" diameter. The number of plants per m² recorded in the quadrats in each extraction was counted, they were left to drain for 3 minutes and then the plant mass of each quadrat was weighed. Next, parts of stems, leaves, and roots were taken from 100 fresh E. crassipes plants obtained from the quadrats by random sampling, for analysis of the heavy metals Pb, As, and Hg, and taken to the laboratory of the Salvadoran Foundation for Social and Economic Development (FUSADES). Pb and As were analyzed using the atomic absorption spectrophotometry method with a graphite furnace, and Hg was analyzed using the atomic absorption spectrophotometry method with a hydride generator. After extraction, the E. crassipes plants were transferred for composting to the site where the experimental design was implemented, located at coordinates 14° 05' 44.28" N and 89° 15' 20.08" W, in the sub-basin of the Jayuca River, in the village of La Cruz, canton Santa Rosa, municipality of Nueva Concepción, department of Chalatenango. Then, at the composting site, the E. crassipes plants were chopped in an agricultural machine used to chop grass. The chopped plant material was placed in the form of a mound 5.70 m long, 1.90 m wide, and 0.90 m high, on a 5 cm thick layer of unchopped E. crassipes plants to avoid contact with the soil, then the mound was covered with a plastic sheet. During the first six weeks, the mound was turned by hand to provide aeration twice a week, and then once a week for the following eleven weeks. During the last two weeks, the composted material was spread in a 30 cm thick layer, leaving it without a cover during the day, and at night it was placed again. At the end of this process, the E. crassipes compost was weighed and stored in sacks for the maturation process for 5 months before being used as a substrate for the production of T. cacao plants in the nursery stage, and a chemical analysis of Pb was performed. During the composting process, the temperature of the material and the relative humidity of the environment were measured daily. The composting period was from December 09, 2018 to April 21, 2019. The cultivation of T. cacao in the nursery stage was implemented from September 29, 2019 to February 23, 2020. Figure 1 shows the extraction of E. crassipes and composting.

Figure 1. A) Extraction of E. crassipes from the Cerrón Grande reservoir. B) Composting.

For the implementation of the study, a completely randomized experimental design was used with five treatments, five replications, and 48 plants per replication. The sample size of T. cacao plants for destructive analysis in the laboratory to determine the dry weight (g) was estimated with the formula:

Where:

n: sample size.     

S²: variance.

t² = Student's t at 95% confidence. 

e²= error (5%). The error value is multiplied by the average, before being squared, thus increasing the number of samples to be processed.

 

The result showed a minimum of 121 plants to be sampled using the height variable; however, a total of 250 plants were sampled (50 for each treatment and 10 plants per replication), thus ensuring a representative sampling. Statistical analyses were performed with Statistix 8.1 software, student version. One-way analysis of variance (ANOVA), with a significance level of 0.05 was used. Significant differences in the means of the treatments were obtained with Tukey's statistical test.

In the test, compost made from E. crassipes from the Cerrón Grande reservoir was used in percentages of 10%, 20%, and 40%, mixed with soil in 90%, 80%, and 60% to complete 100% of the volume of the bags (8"x12") where the T. cacao seeds were planted. The 5 treatments were identified as follows: T₁ (10:90), T₂ (20:80), T₃ (40:60), a relative treatment T₄ (TR, 100% soil, and 3 chemical fertilizations with triple formula fertilizer 15 N-P-K, at 15, 45, and 90 days after germination, using two grams in the first fertilization and five grams in the second and third fertilization) and a control treatment T₅ (TT, 100% soil) without any additive.

Pest and disease control was carried out preventively. For soil insect control, Imidaclopid WG 0.8% was used, applied to the soil 15 days before planting T. cacao seeds. For foliar pest control, the insecticides Abamectin (1.8 EC) and Lambdacyhalothrin (2.5 EC) were used. Prevention of fungal diseases was done with Difenoconazole, Azoxystrobin (32.5 SC) applied every 10 days. The T. cacao plants in the nursery were protected with shade using 73% saran mesh. They were arranged in 4 rows at a width of 0.50 m and 12 plants per row at a length of 1.56 m for each repetition. The width of the rows was 0.60 m x 0.65 m. 

When the T. cacao plants reached 4 months and 15 days after germination, a destructive analysis of the plants, stem, leaves, and roots was carried out to measure the dry weight (g). Following the methodology of Fernandez, et al. (2010), the plants in the center of each replicate were sampled to avoid edge effect. Each plant was measured for diameter at the base of the stem (mm) with a vernier and height (cm) with a tape measure. The soil was separated from the plants using water to leave the root bare. The root was cut and the stems with leaves and roots were placed separately in plastic bags, identified for each treatment and each repetition, obtaining 25 samples of stems with leaves and 25 samples of roots. They were put to dry for 72 hours through the oven method at 50 °C. Once dried, the weight of the stem with leaves, root dry weight, and total dry weight were measured. This test was carried out at the Agricultural Chemistry Laboratory of the National Center for Agricultural and Forestry Technology "Enrique Álvarez Córdova" (CENTA), located in San Andrés, La Libertad, El Salvador. Taking as a reference the methodology of Fonseca et al. (2002), described by Piña and Arboleda (2010), the slenderness index (SI) was estimated with the data obtained from the laboratory, according to equation 1, and the Dickson Quality Index (DQI), with equation 2, as detailed below:

Eq. 1.

Eq. 2.

According to Prieto et al. (2009) the slenderness index is an indicator of the plant's resistance to wind desiccation, its survival and growth in dry sites. Its value should be less than six; higher values indicate that the plant has a thinner stem in relation to its size. The Dickson Quality Index (DQI) groups variables related to plant quality. The higher the index value, the better the plant quality. Biomass correlates with plant survival and growth in the field. The ratio of aerial part to root part was calculated as the quotient between the dry weight of the aerial part in grams and the dry weight of the root in grams (PSa/PSr). Ratios above 2.5 indicate disproportion and the existence of an insufficient root system to provide energy to the aerial part of the plant (Prieto et al., 2009). In addition, T. cacao plants grown at T₃ (T40:60) were sampled to evaluate if there was translocation of Pb from the substrate to the nursery plants.

  Due to the fact that during the cultivation process of T. cacao plants it was observed that in the 5 replicates of T₃ (T40:60) and at a non-significant level in T₂ (T20:80) some T. cacao plants first presented a progressive leaf discoloration turning chlorotic yellow and then showed symptoms of disease in the foliage, it was decided to perform a foliar analysis on plants of the T₃ treatment (T40:60) taken from the 5 replicates. The analysis was carried out at the FUSADES laboratory, San Salvador, El Salvador. On the other hand, in the Plant Parasitology laboratory of CENTA, an analysis of the presence of pathogens in E. crassipes compost was carried out in T₅ (TT) and T₃ (T40:60) in order to determine the pathogens that caused the disease. The Potato Dextrose Agar (PDA) method was used as culture medium, under strict asepsis in a laminar flow chamber with ultraviolet light. Soil and substrate were homogenized and 10g were taken. Dilutions of 1/10,000 and 1/100,000 were prepared and 1 ml of each dilution was taken and placed in glass petri dishes sealed with parafilm tape containing PDA culture medium. The petri dishes were placed in an incubator at 22°C for 5 to 8 days, until fungal and bacterial growth was observed. For the identification of the microorganisms present, a sample of each of the fungi and bacteria grown in the petri dish was taken with a deception needle through a stereoscopic microscope and placed on a slide containing a drop of sterile water, covered with a coverslip and placed in a compound microscope where each of the fungal genera present in the samples was identified (R.F. de Serrano, personal communication, May 24, 2021). 

---

The overall mean of the dry weight (g) aerial part-dry weight (g) root part (PSa/PSr) ratio was 10.11 and a coefficient of variation of 18.37. The treatments with the highest mean were T4, T1, and T5, which recorded a mean of 10.86, 10.26, and 10.10 g, respectively. Treatments T3 and T2 had the lowest means with 9.86 and 9.51 g, each (Table 3). Values above 2.5 indicate disproportion between the aerial part and the root part; therefore, according to these results, there is no balance among the relationship between these two variables. According to the analysis of variance, there is no statistical difference between the means at a significance level of 0.05 (Table 4).

The overall mean of the total dry weight variable was 81.14 g and a coefficient of variation of 16.58. Plant biomass is associated with plant survival and growth in the field. T₁ registered the best mean with 91.20 g. In second order are the treatments T₄, T₃, and T₂ that recorded means of 84.73 g, 83.91 g, and 83.51 g, individually. Lastly, there is T₅ with a mean of 62.36 g (Table 3). According to the analysis of variance, there is a significant statistical difference between the means of the treatments. According to Tukey's test, the means of treatments T₂, T₃, and T₄ are statistically equal, T₁ is statistically different from the other treatments, being the best, and T₅ is the worst with the lowest mean, so that the plants of T₁ with the best mean weight may have a higher percentage of survival in the plantation than those of T₅, which had the lowest mean weight.              

The overall mean of the Dickson Quality Index was 4.22 and the coefficient of variation was 16.40. This index integrates the variables of plant quality, total plant dry weight (g), slenderness index (SI), and the ratio of aerial part dry weight - root dry weight (PSa/PSr); higher values denote better quality plants, which may have more success in surviving in the sites where they are established in the field. T₃ registered the best mean with 4.64 DQI, followed by treatments T₁ with 4.57 DQI, and T₂ with 4.52 DQI. Fourth place was occupied by treatment T₄ with a mean of 4.16. The lowest mean was recorded by T₅ with 3.23 (Table 3). The results of the analysis of variance show that there is a significant statistical difference between the means of the treatments (Table 4). According to Tukey's test, the means of treatments T₂ and T₄ are statistically equal, as well as T₁ and T₃, with the best averages and T₅ with the lowest average.

Regarding the heavy metals evaluated, Pb recorded an average of 3.54 ppm in fresh plants of E. crassipes. Hg and As were not detectable (Figure 3). For this reason, only Pb was analyzed in the E. crassipes compost, but it was no longer detectable (0.00 ppm). In spite of not detecting it in the compost samples analyzed, in order to fulfill the objective related to analyzing whether there is translocation of Pb, an analysis of this element was carried out in the T. cacao plants grown in treatment T₃, with a higher percentage of E. crassipes compost; according to the tests, it was not detectable either.

Due to the problems of progressive leaf discoloration turning chlorotic yellow and then symptoms of disease in T. cacao plants at T₃, a foliar analysis of nutrients was performed on the plants of that treatment. The results were compared with the reference levels used in the Agricultural Chemistry Laboratory of CENTA for the cultivation of T. cacao, based on Methods of Analysis of Soil Plants, Water, and Fertilizers. Fertilizer Development and Organization, 1999 (G. L. Enriquez, personal communication, 24 May 2021). N registered 3.18%, P 0.16%, K 1.32%, Ca 0.55%, Mg 0.20%, and S 0.24%. Fe presented 90.63 ppm, Cu 3.55 ppm, Mn 55.78 ppm, Zn 18.91 ppm, and B registered 67.52 ppm. N presented a higher level than recommended between 2.00% - 2.50%. The nutrients P, Mg, Cu, and Zn presented low levels, being the sufficient level 0.18% for P, 0.45% for Mg, between 8.0 ppm - 12.0 ppm for Cu, and between 20.0 - 100.0 ppm for Zn; while the nutrients K, Fe, Mn, and B presented sufficient levels: 1.30% - 2.2%, 60 - 200 ppm, 50 - 300 ppm, and 25 - 70 ppm, respectively (Table 5).

Figure 3. Results of Pb analysis in fresh E. crassipes plants.

Pathogens in E. crassipes compost at T5 (TT) and T3 (T40:60).

In the E. crassipes compost, four genera of fungi were found: Aspergillus sp, Penicillum sp, Rhizopus sp, Sclerotium sp; and one species of bacteria, which was not identified (Table 6). In T₅, two genera of fungi Aspergillus sp and Fusarium sp; and one bacterial species, which could not be identified, were recorded. On the one hand, in the substrate of T₃ (T40:60), seven genera of fungi Aspergillus sp, Penicillum sp, Fusarium sp, Pythium sp, Cladosporium sp, Rosellinia sp, and Tricoderma sp were found (Table 6). On the other hand, Pythium sp was found in the stem of the plants grown in T₃, and unidentified bacteria were present in the root and leaves. According to the results, the fungi that affected T. cacao plants in T₃ were Fusarium sp, Pythium sp, and Rosellinia sp, the latter being the one with the highest incidence and the one that caused the most damage. In advanced stages, it manifested in the aerial parts causing yellowing, wilting, leaf drop, and dieback. This is consistent with that described by Phillips-Mora and Cerda (2011) and Alarcón et al. (2012), on the symptoms of the fungus Rosellinea pepo on T. cacao plants.  

---

---