Characterization of Cupuaçu (Theobroma grandiflorum) Waste for Substrate in Seedling Production

Abstract

Cupuaçu (Theobroma grandiflorum (Willd. ex Spreng.) K. Schum.), a fruit native to the Amazon, is widely used in the food industry. However, it generates large amounts of shell and seed residues after processing, which are generally discarded inappropriately. We characterized cupuaçu residues to determine their potential as substrates for seedling production. Shells and fruit seeds were collected from a rural community in the municipality of Belterra, Brazil. The residues were weighed, dried, and crushed for chemical (macro and micronutrients, elemental analysis, and ash content) and physical (density and porosity) analyses. Different proportions of each residue (9:1, 3:1, 2:1, 1:1, and 0:1) were used, and soil alone was used as the control. The chemical analysis of the plant material showed that cupuaçu seed residues had higher concentrations of macro- and micronutrients among the analyzed elements when compared to the fruit shell residues. The macronutrient concentrations (P, K, Ca, and Mg) were, respectively, 5, 1.3, 2.3, and 5.6 times higher than those in the shell residues. Compared with the soil sample, the concentrations of the macronutrients (P, K, Ca, and Mg) in the shell residues were, respectively, 600, 162, 1283, and 12.35 times higher. Analysis of variance and comparison of treatment means were performed using Tukey’s test (p ≤ 0.05). Chemical analysis showed that cupuaçu seed and shell residues had higher concentrations of macro- and micronutrients than soil. All proportions tested with residues had lower densities and greater porosities than soil. The cupuaçu residues showed desirable chemical and physical characteristics for their use as substrate in seedling production.

1. Introduction

The production of seedlings is an activity of great importance, especially when planning reforestation programs and the recovery of degraded areas. However, in addition to propagation material, the choice of substrate is crucial for the production of high-quality seedlings.

An alternative for use as a substrate in seedling production is plant residues, which can help reduce environmental impacts while lowering costs [1]. In the Amazon, the tropical fruit production chain generates a lot of waste, mainly from shells and seeds, and its disposal is almost always neglected, as in the case of cupuaçu (Theobroma grandiflorum (Willd. ex Spreng.) K. Schum.).

Cupuaçu is native to the Amazon and is widely used in the food industry. It is one of the most popular fruits in Northern Brazil and is used to produce juice, sweets, and ice cream. The growing commercial interest in the fruit has led to the development of new industries and research on this food species [2].

In 2017, 21,240 tons of fresh cupuaçu were recorded in Brazil [3]. The physical composition of the fruit, on average, consists of 42% shells, 14% seeds, and 39% pulp [4]. Although the shell represents a considerable portion of the total fruit weight, it is not commercially used and is frequently discarded inappropriately [5], generating a large volume of agro-industrial waste after pulping.

Despite the various potential uses of cupuaçu residues, such as substrates for seedling production, energy generation, gasification technology to replace diesel, and human consumption in the form of flour with excellent nutritional value [6,7,8], these residues have not received the same level of attention from the scientific community as açaí (Euterpe oleracea Mart.) seeds and coconut (Cocos nucifera L.) shells in the Amazon biome [9,10,11].

The use of plant residues as substrates for seedling production requires prior physical and chemical evaluation of the material [12,13], as the quantity and availability of mineral nutrients influence seedling growth. Moreover, identifying critical levels of elements and species requirements can impose limitations on methods used to diagnose nutritional deficiencies [14,15].

Thus, the physical characteristics of materials are essential for evaluating their volumetric density, porosity, and water retention capacity. Based on these properties, it is possible to indicate the quality and suggest the use and limitations of substrates [16]. In this context, we evaluated the potential of cupuaçu fruit shells and seed waste as a substrate for use in seedling production.

2. Materials and Methods

Cupuaçu fruit shells and seeds were collected from a property in the Vila Mensalista community, located in the municipality of Belterra, Pará, in the Brazilian Amazon, between January and April 2023. The plant material was weighed and dried in an oven with forced air circulation for three days at a temperature of 75 °C for the shells and 105 °C for the seeds, due to their resistance to drying, until their weight stabilized. After drying, the shells and seeds were ground in a knife mill, and the seeds were passed through a 2-mm sieve for laboratory analysis.

For chemical characterization, soil samples of Umbric Ferralsols (Latossolo Amarelo com A húmico) under forest vegetation and cupuaçu residues were sent to the Soil Laboratory of the Federal University of Viçosa (UFV). A complete fertility analysis was performed on the soil samples. Soil samples were analyzed for pH (1:2.5 soil:water); organic matter (OM), determined by organic carbon analysis by wet digestion with potassium dichromate and multiplication by the factor 1.724; potassium (K⁺), phosphorus (P), sodium (Na⁺), copper (Cu²⁺), iron (Fe²⁺), manganese (Mn²⁺), aluminum (Al⁺³), and zinc (Zn²⁺) extracted by Mehlich⁻¹ (H₂ SO₄ 0.0125 mol L⁻¹ and HCl 0.05 mol L⁻¹), with K⁺ determined using a flame photometer, P by colorimetry, and cationic micronutrients using an atomic absorption spectrophotometer; calcium (Ca²⁺) and magnesium (Mg²⁺) were extracted with 1 mol L⁻¹ KCl and determined using atomic absorption spectrophotometry; potential acidity (H + Al) was extracted with 0.5 mol L⁻¹ calcium acetate and quantified by titration; sulfur (S) was extracted using barium chloride, with subsequent reading using a spectrophotometer; and boron (B) was determined by hot water [17]. At last, the sum of bases (SB = K⁺ + Ca²⁺ + Mg²⁺), effective cation exchange capacity (ECEC = SB + Al⁺³), total cation exchange capacity (TCEC = SB + H + Al), base saturation (BS = SB/TCEC × 100), and aluminum saturation (AS = (Al⁺³/ECEC × 100) were calculated.

The total levels of macro- and micronutrients in the cupuaçu residue samples were determined. Elemental analysis of carbon (C), nitrogen (N), hydrogen (H), and sulfur (S) was performed at the Laboratory of Wood Technology and Bioproducts of the Federal University of Western Pará (UFOPA) using a Vario Macro Cube elemental analyzer with 99.9% accuracy. Ash content was analyzed according to a methodology adapted from the Manual of Physical–Chemical Methods for Food Analysis [18].

The physical analysis of the soil and cupuaçu residues was performed under nursery conditions. Soil, fruit shell, and seed residues were placed in 400-mL plastic containers in proportions (soil:residues) of 9:1, 3:1, 2:1, 1:1, and 0:1 (

Table 1. Proportion of soil (So) and residues of fruit shells (FS) and seeds (Sd) of cupuaçu in the evaluated treatments.

Treatment	Proportion (Soil:Residues)	Soil (g)	Waste of Cupuaçu (g)
			Fruit Shells (FS)	Seed (Sd)
So + FS	9:1	180	20	0
So + FS	3:1	150	50	0
So + FS	2:1	130	70	0
So + FS	1:1	100	100	0
FS	0:1	0	100	0
So + Sd	9:1	180	0	20
So + Sd	3:1	150	0	50
So + Sd	2:1	130	0	70
So + Sd	1:1	100	0	100
Sd	0:1	0	0	100
So + FS + Sd	18:1:1	180	10	10
So + FS + Sd	6:1:1	150	25	25
So + FS + Sd	4:1:1	130	35	35
So + FS + Sd	2:1:1	100	50	50
FS + Sd	0:1:1	0	100	100
So (control)	1:0:0	200	0	0

). The control treatment consisted of soil without the addition of any cupuaçu residue. The experimental design was completely randomized (CRD) in a factorial scheme (6 × 3), with three replications. The containers with the soil and residues were kept in a greenhouse covered with transparent plastic for 30 days, during which they were maintained at field capacity by adding distilled water daily.

After 30 days, the physical attributes of the total porosity (TP) and substrate density (SD) were evaluated using the methodology recommended by the soil analysis method [17]. The treatment samples were collected using volumetric rings and placed in air forced circulation greenhouse at 105 °C for 24 and 48 h. After these periods, the samples were placed in a desiccator and weighed on an analytical balance. The data obtained were subjected to analysis of variance and Tukey’s test (p ≤ 0.05) to compare the means of the treatments and Dunnett’s test to compare the control and the treatments using R software version 4.1.2 [19].

3. Results and Discussion

The soil had high acidity (pH 4.7), and the fruit and seed shell residues had medium acidity, with pH values of 5.3 and 5.2, respectively (

Table 2. Chemical attributes of soil (So) and residues of cupuaçu shells (FS) and seeds (Se) and optimal substrate levels for seedling production.

Properties	Unit	FS	Se	So	Optimal Levels [21,22]
pH H2O		5.23	5.20	4.67	5.2–6.3
C/N		28.26	26.39	14.27	20–40
P	g.kg−1	0.63	3.26	0.01	0.006–0.01
S		0.86	1.59	N.A.	-
K		6.79	9.07	0.07	>7
Ca		0.45	1.04	0.23	0.15–0.25
Mg		0.68	3.83	0.06	>0.2
N		2.90	23.30	4.45	0.0–0.2
Al3+	cmolc.dm−3	N.A.	N.A	1.79	-
H + Al		N.A.	N.A	15.00	-
O.C.	%	8.16	61.49	6.44	-
O.M.		4.01	2.30	11.07	>80
Ashes		6.60	10.00	N.A.	-
Cu	mg.kg−1	2.91	16.91	N.A.	0.001–0.5
Fe		N.A.	3.35	N.A.	>70
Zn		6.77	43.14	N.A.	0.3–3.0
Mn		7.36	8.54	N.A.	0.3–3.0
B		2.78	11.23	N.A.	0.005–0.5

O.C.: organic carbon; O.M.: organic matter; N.A. = not available.

). Acidic soils are common in Amazonian ecosystems [20], and soils can be considered good for agricultural crops when their pH is between 5.5 and 6.0 [21]. The pH of organic substrates should be in the range of 5.2–5.5 [20]. The residues evaluated in this study were within the recommended pH levels for the use of organic substrates.

The soil sample had high exchangeable acidity, with an exchangeable aluminum (Al³⁺) content of 1.79 cmol_c.dm⁻³ and low base sum (Table 2). High exchangeable acidity can limit root growth, affect the availability of other nutrients, and impair the mineralization of organic matter [21], thereby impairing plant growth in nurseries. The potential acidity (H + Al) of the soil sample was 15 cmol_c.dm⁻³, which is classified as very high, which is considered beneficial for soil fertility purposes. However, because the base saturation (BS = 7.7%) was remarkably low and aluminum saturation was high (AS = 58.7%) (Table 2), the soil sample was characterized as having low fertility. Considering the evaluated acidities (active, exchangeable, and potential acidity), it is evident that the residues present better physicochemical conditions for the production of seedlings, mainly in the development of the root system.

The chemical analysis of the plant material showed that cupuaçu seed residues had higher concentrations of macro- and micronutrients among the elements analyzed compared to the fruit shell residues (Table 2). The macronutrient concentrations (P, K, Ca, and Mg) in the seeds were 5.0, 1.3, 2.3, and 5.6 times higher, respectively, than those in the shell residues. Compared with the soil sample, the mineral richness of the shell residues in terms of macronutrients was 600, 162, 1283, and 12.35, respectively. Plants require the presence of calcium, magnesium, phosphorus, potassium, and other elements in considerable quantities, as they perform vital functions throughout their life cycle [23]. The cupuaçu shell and seed residues contained high concentrations of nutrients, indicating their potential for use in agriculture as organic substrates that can provide essential elements to plants.

The greatest differences in carbon, nitrogen, and phosphorus concentrations between cupuaçu seed and shell residues were observed, with levels 7.5, 8.0, and 5.5 times higher, respectively, in seeds than in fruit shell residues. The P concentration in the shell was 0.63 g.kg⁻¹ (Table 2), which is above the recommended level for substrates for seedling production, which is typically between 0.006 and 0.01 g.kg⁻¹ [22]. The P concentration of the Brazilian nutshell residue was 18.3 g.kg⁻¹ [24], which was much higher than that found in our research.

The highest P content was observed in seed residues (3.26 g.kg⁻¹), a value well above that of soil (0.012 g.kg⁻¹) (Table 2). These results were higher than the optimal levels (0.006–0.01 g.kg⁻¹) recommended by Lopes et al. [22]. The presence of adequate concentrations of phosphorus is essential in the initial stages of plant growth, since its deficiency results in stunted growth in the juvenile phase of the plant [25]. Phosphorus (P) is a key element in photosynthesis, and the availability of this element in cupuaçu residue can favor better seedling growth, both in terms of speed (reduction in time) and quality.

The K levels found in the residues of cupuaçu seeds and fruit shells and in soil were 9.07 g.kg⁻¹, 6.79 g.kg⁻¹, and 0.07 g.kg⁻¹, respectively (Table 2), and were considered adequate only in seed residues, according to the recommendations of Ribeiro et al. [21] in their studies with soils in the state of Minas Gerais, Brazil. Potassium plays several vital roles in plants and is mainly important for activating various enzyme systems, many of which are involved in the processes of photosynthesis and respiration [26].

The Mg content in the residues was 0.68 g.kg⁻¹ for the shells and 3.83 g.kg⁻¹ for the seeds (Table 2), which was above the optimum level recommended by Lopes et al. [22]. The soil had a Mg content (0.06 g.kg⁻¹) below the recommended optimum level. These results demonstrate the mineral richness and nutritional potential of cupuaçu residues as a substrate for seedling production when compared to the soil usually used for this purpose.

The greater concentration of essential elements (calcium, magnesium, and potassium) in the residues, when compared to the soil, demonstrates that the use of cupuaçu residues can reduce the use of mineral fertilizers, shorten production time, and obtain more vigorous seedlings.

The soil presented a higher organic matter (OM) content compared to the cupuaçu shell and seed residues, with values of 11.07%, 4.01%, and 2.3%, respectively (Table 2). The ideal OM content in substrates for plant seedlings may vary depending on the species and cultivation conditions. However, the substrate for seedlings should have an OM content >80% to promote healthy plant development [22]. In addition to contributing to the supply of nutrients, OM has a significant influence on the physical properties of growing media.

Elemental analysis indicated that fruit and seed shell residues have C/N ratios of 26 and 28, respectively. These values are in accordance with the ideal standards for substrates used in plant cultivation (Table 2), which range from 20 to 40 [22,24]. The results obtained for the residues contrast those of the soil sample with a C/N ratio of 14.27. The C/N ratio of cupuaçu residues shows that, during its decomposition, mineralization will predominate, favoring the release of essential elements for plant seedlings. This fact corroborates the tendency of cupuaçu residues to reduce the use of mineral fertilizers and produce healthier seedlings in a shorter time.

The cupuaçu seed residues had an ash content of 10%, which was higher than that of the shell residues (6.6%), indicating that the seeds had higher levels of inorganic and organic material than the shells. The ash contents obtained for the seeds are compatible with the greater mineral richness observed in these residues (Table 2), being higher than those observed in cupuaçu seed powder, which presented an ash content of 2.12% [27], and in the nibs of cupuaçu almond (2.18%) when evaluating the physical and chemical changes of the seeds during the fermentation process [28]. The ash content of the cupuaçu shell observed in this study was higher than that found in shell residues (1.99%) of this fruit, which were evaluated for flour production [29].

Cupuaçu shells and seed residues are rich in nutrients (mineral and organic) and moderately acidic compared to soil. Therefore, they can be an alternative substrate for seedling production, replacing the conventional substrate (anthropogenic horizon A), which is generally used in this process. The use of these residues for seedling production, in addition to the high levels of essential nutrients for plants, will play a relevant environmental and economic role in agriculture. In particular, agroecological and organic production systems have gained prominence as a sustainable alternative to conventional cultivation methods, as they are based on principles and dynamics that seek to reduce dependence on chemical fertilizers [30,31].

In the evaluation of total porosity (TP) and substrates density (SD), a significant difference was found between the treatments (p ≤ 0.01). All proportions of the treatments containing cupuaçu residues had lower SD and higher TP values than the control treatment (

Table 3. Substrate density (SD) and total porosity (TP) of the soil substrate (So) and the residues of shells (FS) and seeds (Sd) of cupuaçu fruits used in different proportions.

Treatments	Proportion (Soil:Residues)	SD (kg.dm−3)	TP (m3.m−3)
So + FS	9:1	0.57 **	0.78 **
So + FS	3:1	0.44 **	0.83 **
So + FS	2:1	0.43 **	0.83 **
So + FS	1:1	0.38 **	0.85 **
FS	0:1	0.26 **	0.90 **
So + Sd	9:1	0.49 **	0.81 **
So + Sd	3:1	0.41 **	0.84 **
So + Sd	2:1	0.37 **	0.85 **
So + Sd	1:1	0.32 **	0.87 **
Sd	0:1	0.22 **	0.91 **
So + FS + Sd	18:1:1	0.51 **	0.80 **
So + FS + Sd	6:1:1	0.48 **	0.81 **
So + FS + Sd	4:1:1	0.48 **	0.81 **
So + FS + Sd	2:1:1	0.44 **	0.83 **
FS + Sd	0:1:1	0.36 **	0.86 **
So (control)	1:0:0	0.73 **	0.72 **
CV (%)		7.54	1.48

** Significant by Dunnett’s test (p < 0.01). CV: coefficient of variation.

). These results demonstrate that cupuaçu residues improve the physical properties of soil substrates.

The substrates density (SD) of the residues ranged from 0.26 to 0.57 kg.dm⁻³ for the shells, from 0.22 to 0.49 kg.dm⁻³ for the seeds, and from 0.36 to 0.51 kg.dm⁻³ for the shells + seeds combination, values much lower than those observed for the soil (0.73 kg.dm⁻³) (Table 3). The results indicate that cupuaçu residues improve the density of the substrates, which favors gas exchange, rooting, infiltration, and the availability of water and nutrients for plants. The optimum level of density for plant cultivation substrates can range from 0.45 to 0.55 kg cm⁻³ [22], and the values observed for cupuaçu residues in our research are within the recommended levels, indicating that they can be used as a plant substrate, regarding this physical attribute.

The low values found for substrate density in the proportion of 100% of the residues of shells (0.26 kg.dm⁻³), seeds (0.22 kg.dm⁻³), and for the combination of shells + seeds (0.36 kg.dm⁻³) (Table 3) indicate that these residues present optimal levels for this variable, better than those considered by Lopes et al. [22]. The substrate composed of Brazil nut shell + acerola seed has a low density (0.29 kg.dm⁻³), being recommended for the production of single açaí (Euterpe precatoria Mart.) seedlings, because it promotes greater growth and dry biomass, resulting in better quality seedlings [32].

The total porosity (TP) of the residues ranged from 0.78 to 0.90 m³.m⁻³ for the shell, from 0.81 to 0.91 m³.m⁻³ for the seeds, and from 0.80 to 0.86 m³.m⁻³ for the shell + seed combination (Table 3), values within the optimum level recommended for substrates used in seedling production, which is above 0.85 m³.m⁻³ [22]. TP is closely linked to the space available for plant development, which varies according to how the particles are arranged [33].

The TP values found in the proportion of 10% of the residues were 0.78 m³.m⁻³ for the shells, 0.81 m³.m⁻³ for seeds, and 0.80 m³.m⁻³ for shell + seeds (Table 3), which are lower than the optimum level recommended by Lopes et al. [22]. However, the use of this proportion of residues can still be recommended, because even below the level considered optimum, they present higher TP than agricultural soils, which vary between 20% and 40%.

Substrates of processed coconut fiber (coconut powder) and composted pine bark, used alone and in combination, aiming to promote the growth of umbu seedlings (Spondias tuberosa Arruda), presented a porosity of 83.5% (0.835 m³.m⁻³) in the proportion of 75% coconut powder + 25% composted pine bark, which is below the recommended level; however, its use was still indicated, as it provides the formation of seedlings with greater vegetative quality [34].

The higher the proportion of cupuaçu fruit shells, seeds, and their mixtures in the substrate, the lower the density value and the higher the TP value (Table 3). This can be explained by the fact that the porosity is inversely proportional to the density of the substrate [35]. These results show the potential of cupuaçu residues as substrates for plants, which can replace the use of soil due to their greater nutritional richness (chemical properties) and desirable physical characteristics (SD and TP), in addition to bringing environmental benefits by reducing the inappropriate disposal of these residues into the environment and enabling economic gains for the producer by reducing the costs of purchasing substrates.

These aspects are in line with what is based on agroecological and organic production, which encourages the use of plant residues to produce organic compounds to improve soil fertility, promote biodiversity enrichment, provide suitable habitats for beneficial organisms, and seek to maximize resource efficiency and minimize waste within agricultural systems by transforming plant residues into fertilizer, which can contribute to the circular economy. In addition, the presence of residues can help create an environment less conducive to pests [30,36,37].

The interaction of factors (residue versus concentration) demonstrated that the mixture of shell + seed residues, in the proportion of 100%, resulted in the best results for SD and TP (

Table 4. Total density of soil (So) and residues of shells (FS) and seeds (Sd) of cupuaçu fruits.

Residues	Total Density (kg.dm−3)
	Proportion (Soil:Residues)
	9:1	3:1	2:1	1:1	0:1
FS	0.57 (±0.02) bB	0.44 (±0.04) bC	0.43 (±0.04) bC	0.38 (±0.04) bcC	0.26 (±0.04) bcD
Sd	0.51 (±0.01) bB	0.48 (±0.05) bBC	0.48 (±0.03) bC	0.44 (±0.02) bCD	0.36 (±0.02) bD
FS + Sd	0.49 (±0.01) bB	0.41 (±0.02) bB	0.37 (±0.03) bB	0.32 (±0.02) cBC	0.22 (±0.01) cC
So (control)	0.74 (±0.07) aA	0.74 (±0.07) aA	0.74 (±0.07) aA	0.74 (±0.07) aA	0.74 (±0.07) aA
CV (%) = 9.11

Means followed by the same lowercase letters in the columns and the same uppercase letters in the rows do not differ from each other by Tukey’s test (p < 0.05). Values in parentheses represent the standard deviation. CV = coefficient of variation.

and

Table 5. Total porosity of soil (So) and residues of shells (FS) and seeds (Sd) of cupuaçu fruits.

Residues	Total Porosity (kg.dm−3)
	Proportion (Soil:Residues)
	9:1	3:1	2:1	1:1	0:1
FS	0.78 (±0.01) aC	0.83 (±0.02) aB	0.83 (±0.02) aB	0.85 (±0.01) abB	0.90 (±0.01) abA
Sd	0.80 (±0.01) aB	0.82 (±0.02) aB	0.82 (±0.01) aB	0.83 (±0.01) bAB	0.86 (±0.01) bA
FS + Sd	0.81 (±0.00) aC	0.84 (±0.01) aBC	0.85 (±0.01) aB	0.87 (±0.01) aAB	0.91 (±0.00) aA
So (control)	0.72 (±0.03) bA	0.72 (±0.03) bA	0.72 (±0.03) bA	0.72 (±0.03) cA	0.72 (±0.03) cA
CV (%) = 3.21

Means followed by the same lowercase letters in the columns and the same uppercase letters in the rows do not differ from each other by Tukey’s test (p < 0.05). Values in parentheses represent the standard deviation. CV = coefficient of variation.

), with a lower density value (0.22 kg.dm⁻³) and greater total porosity (0.91 m³.m⁻³). Although the highest concentrations of cupuaçu residues provided the best physical attributes, treatments with lower proportions of cupuaçu residues also increased in SD and TP compared to 100% soil. The results show that small amounts of cupuaçu residues are sufficient to promote improvements in the density and porosity of the substrate.

The characteristics of the evaluated cupuaçu residues are promising for use as substrates in seedling production. The suitability of recycled residues as raw materials for substrate production is assessed based on their nutrient content, water retention capacity, pH, salinity, porosity, and stability. Therefore, understanding the specific attributes of these waste materials is essential to explore their potential applications and broader implications in the production of recycled waste substrates (RWS) [38].

4. Conclusions

The residues from cupuaçu fruits demonstrated desirable chemical and physical characteristics for their use as substrates in seedling production, as they are rich in macro- and micronutrients essential for plant growth and development, in addition to having low density and high porosity, which make them favorable for rooting and plant support.

The proportion of 100% residues (shell + seed) achieved the highest density and porosity. However, regardless of the proportion used, cupuaçu residues promoted improvements in these characteristics, making their use viable in small quantities or in situations of low availability of residues.

The results obtained in this study are very promising and of great importance, as they indicate the use of cupuaçu shells and seeds as substrate for seedling production, in addition to showing a possible destination for the large amount of residue generated during fruit processing, thus avoiding improper disposal and accumulation in the environment. They also show that cupuaçu fruit residues can be a valuable tool for agroecological and organic agriculture, as they contribute to the sustainability of agricultural systems.

Future research can investigate the costs and economic gains that the use of residues from this species can provide when incorporated into forest or agricultural seedling production programs. There is a need to further research the release of nutrients from cupuaçu residues to plants, as well as to evaluate the growth and development of seedlings using these residues as substrates.