Nativa, Sinop, v. 10, n. 2, p. 184-190, 2022.

Pesquisas Agrárias e Ambientais

DOI: https://doi.org/10.31413/nativa.v10i2.13529 ISSN: 2318-7670

The use of biochar-urea pellet formulations to reduced nitrogen losses

Ciro Augusto de Souza MAGALHÃES1, Bruna Larissa da Silva dos SANTOS2,

Fabiano André PETTER2, Eduardo da Silva MATOS3, Isabela Volpi FURTINI4,

Marina Moura MORALES5

1Brazilian Agricultural Research Corporation (Embrapa Agrosilvopastoral), Sinop, MT, Brazil.

2Institute of Agricultural and Environmental Sciences, Federal University of Mato Grosso, Sinop, MT, Brazil.

3Brazilian Agricultural Research Corporation (Secretariat of Intelligence and Strategic Affairs), Brasília, DF, Brazil.

4Brazilian Agricultural Research Corporation (Embrapa Rice & Beans), Santo Antônio de Goiás, GO, Brazil.

5Brazilian Agricultural Research Corporation (Embrapa Forestry), Colombo, PR, Brazil.

E-mail: ciro.magalhaes@embrapa.br

(ORCID: 0000-0002-7899-8566; 0000-0003-4390-6278; 0000-0002-1470-1671; 0000-0001-9125-7239;

0000-0002-4932-9937; 0000-0001-9125-7239)

Recebido em 08/03/2022; Aceito em 02/05/2022; Publicado em 03/06/2022.

ABSTRACT: This study aimed to evaluate the effects of soil texture, fertilizer formulation and nitrogen dose

on the characteristics of upland rice production, and to compare the Agronomic Efficiency Index (AEI) of

formulations of biochar-urea pellets (BUPs). The treatments comprised four fertilizers (three formulations of

BUP and urea) and five nitrogen doses (0, 75, 150, 300 and 600 mg dm-3), analyzed in two soil (sandy and clay).

For each soil texture, a greenhouse experiment was established as a randomized block design with a 5 x 4

factorial arrangement and four replicates. Chlorophyll index, plant height, number of tillers and panicles, dry

mass of aerial parts and of grains were all affected significantly by soil texture, fertilizer formulation and nitrogen

dose and/or by the interactions between these sources of variation. The results demonstrated that the

performances of BUPs are highly dependent on soil texture. Under sandy soil, application of BUP-based

fertilizers contributed to the increase or maintenance of grain production compared to that of urea alone.

Whereas under clayey soil the performance of BUPs exceeded that of urea only at low nitrogen doses.

Compared to urea, BUPs were more efficient under sandy soil, with potential to increase AEI.

KEYWORDS: organomineral fertilizers; wood sawdust; pyrolysis; N-leaching.

Uso de pellets de biochar-ureia para reduzir as perdas de nitrogênio

RESUMO: Este trabalho objetivou avaliar os efeitos da textura do solo, formulações e doses de nitrogênio em

características do arroz de terras altas, e comparar o Índice de Eficiência Agronômica (AEI) das formulações

de pellets de biochar-ureia (BUP’s). Os tratamentos foram: quatro fertilizantes (três formulações de BUP e

ureia) e cinco doses de nitrogênio (0, 75, 150, 300 and 600 mg dm-3), avaliados em dois solos de textura distinta.

Para cada solo (arenoso e argiloso), foi conduzido um experimento em casa-de-vegetação em blocos

casualizados em um arranjo fatorial 5 (doses) x 4 (fertilizantes), com quatro repetições. O índice de clorofila,

altura de plantas, número de perfilhos, número de panículas, massa seca de parte aérea, massa seca de grãos

tiveram diferenças significativas em função da textura do solo, fertilizantes e doses de N e/ou pelas interações

entre esses fatores. Os resultados demonstraram que o desempenho dos BUP’s foi dependente da textura do

solo, com melhores respostas no solo arenoso em relação à ureia, com potencial de elevar a eficiência

agronômica da adubação nitrogenada.

PALAVRAS-CHAVE: fertilizantes organominerais, pó de serra, pirólise, lixiviação de N.

1. INTRODUCTION

The search for intensive but sustainable production

systems involves the use of practices that contribute to

increase the efficiency of nutrient use while reducing nutrient

pollution. Nitrogen fertilizers are among the most important

inputs for food production but nitrogen efficient use remains

challenging (REETZ, 2017). Nitrogen fertilizers

management is considered complex because a significant

proportion of nitrogen applied to the soil is lost through

leaching, volatilization or denitrification (FAGERIA;

BALIGAR, 2005), and such losses can be as high as 50%

(KLUTHCOUSKI et al., 2006). Depending on the amount

applied and the environmental conditions, nitrogen lost can

contribute to surface or ground water pollution as well as to

increase greenhouse gas emissions (CANTARELLA, 2007).

Nitrogen losses through leaching represents the mainly

pathway of nitrogen losses in tropical soils, especially because

its form that exhibit high mobility in soil water and have less

chance of attaching to charged soil particles. The extent of

leaching is influenced by soil texture and structure,

characteristics of the fertilizer and application management

practices (ERNANI et al., 2002; SANGOI et al., 2003; FEY

et al., 2010). Although urea is one of the most common

agricultural fertilizers (IPNI, 2019), its rapid hydrolysis by

urease to volatile ammonia or its oxidation to nitrate by

microbial nitrifiers may lead to poor crop responses and

greater environmental damage. Thus, considerable research

effort has been expended in recent years with aim of

improving nitrogen use efficiency (NUE), particularly

through the design of enhanced efficiency fertilizers that

Magalhães et al.

Nativa, Sinop, v. 10, n. 2, p. 184-190, 2022.

185

attempt to minimize nutrient losses. Such fertilizers may

incorporate nitrogen stabilizers such as urease and

nitrification inhibitors to delay processes of nitrogen losses

such as the volatilization of NH3, the leaching of nitrate

(NO3−) and the reduction of N2O emissions, but also to

control nitrogen release and meet crop demand. (FRAZÃO

et al., 2014; TIMILSENA et al., 2015; GUELFI, 2017; RECH

et al., 2017). An alternative strategy involves the use of

organomineral fertilizers (OMFs) comprising a synthetic

fertilizer such as urea combined with an organic matrix.

However, this approach has been little explored, likely due to

the challenge of finding stable formulations that inhibit

interactions between the nitrogen source and the organic

matrix from generating even greater nitrogen losses after

mixing. Nevertheless, the adoption of a highly stable organic

source could be essential for creating OMFs that are more

efficient than conventional nitrogen fertilizers.

Biochar is a chemically stable form of charcoal

produced by the pyrolysis of biomass in the presence of little

or no oxygen (LENG; HUANG, 2018). Direct application of

biochar to soil improves the physical, chemical and biological

characteristics of the substrate and has been reported as a

contributor to increase NUE (PETTER et al., 2016). In this

sense, biochar is not only a practical solution for the disposal

of harmful agro-industrial waste (LEHMANN; JOSEPH,

2009) but also has great potential as an organic matrix

(MANIKANDAN; SUBRAMANIAN, 2013; ZHENG et

al., 2013; AGEGNEHU et al., 2016) and as a long-term sink

for atmospheric carbon dioxide (FAWZY et al., 2021).

The aim of the present study was to determine the

viability of using biochar-urea pellets (BUPs) in agricultural

systems in order to reduce nitrogen losses and environmental

nitrogen pollution. For this purpose, we have: (i) evaluated

the effects of soil texture, fertilizer type and nitrogen dose on

the characteristics of upland rice production, and (ii)

compared the Agronomic Efficiency Index values and plant

yields fertilized with different BUPs formulations or with

urea alone.

2. MATERIAL AND METHODS

2.1. Preparation and characterization of fertilizers

Activated biochar was produced from sawmill waste in

slow pyrolysis reactor (horizontal tubular furnace) operating

with water steam injection at 650ºC. The chemical

composition of the activated biochar corresponded to 49%

of phenolics, 21% of lactose and 30% of carboxylic acids

groups. Real density and apparent density corresponded to

1.27 and 0.31 g cm-3, respectively, and 75% of porosity.

Commercial grade urea was ground into fine particles (< 1

mm mesh) using a rotor mill and combined with the organic

matrix to produce biochar-urea mixtures with proportions

2:1, 1:2 and 1:4 (BUP2:1, BUP1:2 and BUP1:4, respectively). The

mixtures were pelletized and the nitrogen contents

determined by automated dry combustion analysis using a

vario MACRO cube (Elementar Analysensysteme,

Langenselbold, Germany) CNHS elemental analyzer. The

total nitrogen contents of BUP2:1, BUP1:2, BUP1:4 and pure

urea were established as 16, 31, 36 and 45%, respectively. The

mechanical hardness of the formulations were evaluated

using a TA.HDplusC texture analyzer (Stable Micro Systems,

Godalming, UK) and the forces required to break the pellets

corresponded to 19, 10 and 2 kgf, respectively, for BUP2:1,

BUP1:2 and BUP1:4.

2.2. Soil preparation and analysis

Sandy and clay textured latosols were collected from the

10-20 cm soil layer under a native forest. Soils were air dried

and sieved through a 2-mm mesh sieve. Table 1 shows the

physicochemical characteristics of the two types of soils used

in the experiments. Prior to the experiment establishment,

soils of each texture were passed through 4 mm mesh sieves

and their acidities corrected with limestone to raise the base

saturation to 50%. Treated soils were transferred to separate

plastic bags, homogenized with an appropriate BUP

formulation or urea, transferred to 5 dm3 plastic pots and

finally allowed to equilibrate for 30 days under greenhouse

conditions with soil moisture maintained at 70% of field

capacity.

Table 1. Physicochemical characteristics of the forest soils used in the determination of the agronomic efficiency of biochar-urea pellets.

Tabela 1. Características físico-químicas dos solos utilizados na determinação da eficiência agronômica dos pellets de biochar-ureia.

Soil

texture pHH2O Pa K Ca Mg Al CECb Organic C Clay Silt Sand

(mg dm-3) (cmolc dm-3) (g kg-1)

Clay

4.8

0.2

0.14

0.06

0.96

7.1

17.6

503

403

Sand

4.8

0.5

0.33

0.13

0.84

7.0

16.7

131

831

a Melich-1; b Cation exchange capacity.

2.3. Experimental design and measurements of

agronomic variables

For each soil texture, completely randomized block

design experiments were established with a 5 x 4 factorial

arrangement comprising five nitrogen doses (0, 75, 150, 300

and 600 mg dm-3) and four types of fertilizer (BUP2:1, BUP1:2,

BUP1:4 and pure urea) with four replicates of each

combination. Each pot received four rice (Oryza sativa L.)

seeds and thinning was performed 20 days after the

emergence of seedlings leaving only two plants per pot. Soil

moisture was maintained at 70% of the field capacity

throughout the crop cycle. On the day before rice sowing,

were applied 80 mg dm-3 of N, 250 mg dm-3 of P, 70 mg dm-

3 of K, 420 mg dm-3 of CaO, 60 mg of dm-3 of S, 3.6 mg dm-

3 Mn, 5.0 mg dm-3 Zn, 1.5 mg dm-3 Cu, 0.15 mg dm-3 Mo and

0.5 mg dm-3 B, diluted in water and inserted equally in each

treatment plot. Falker chlorophyll indices were determined at

the flowering stage using a Falker ClorofiLOG® 1030

(Falker, Porto Alegre, RS, Brazil) portable chlorophyll meter,

and plant height (cm) and numbers of tillers and panicles per

plant were recorded at the end of the culture cycle.

Subsequently, grains were collected and the aerial parts of the

plants were cut at 5 cm from the soil. Harvested plant

material was dried in a forced-air oven at 60°C until constant

weight, and the dry masses of aerial parts (DMA; g pot-1) and

grains (DMG; g pot-1) were determined. To evaluate the

agronomic efficiency of the organomineral fertilizer

formulations, the Agronomic Efficiency Index (AEI) was

calculated for grain dry matter (MSG) production, using the

following:

The use of biochar-urea pellet formulations to reduced nitrogen losses

Nativa, Sinop, v. 10, n. 2, p. 184-190, 2022.

186

AEI (%)= ()

() x 100 (01)

where: DMGi (g pot-1) is the grain production in the experimental

treatment, DMG0 (g pot-1) represents grain production without

application of nitrogen, and DMGu (g pot-1) refers to grain

production with application of urea at the same dose as in DMGi.

2.4. Statistical analyses

Data obtained from sandy and clay soil conditions were

submitted, individually and jointly, to analysis of variance

(ANOVA) in order to analyze the effects of the independent

variables (soil texture, fertilizer type, nitrogen dose) and their

interactions on the dependent variables (chlorophyll index,

tillers plant-1, panicles plant-1, plant height, DMA, DMG and

AEI). When significant differences were found, mean values

were compared using the Tukey test (p < 0.05). The best fit

linear or quadratic regression models for the data sets were

chosen on the basis of the nitrogen doses applied to the soil

(FERREIRA, 2011).

3. RESULTS

The data on the effects of the independent variables

(soil texture, fertilizer type and nitrogen dose) and their

interactions on the characteristics of upland rice production

are presented in Table 2. The chlorophyll index was affected

significantly by nitrogen dose (p < 0.0001) with linear

adjustment for both soil texture and fertilizer types (Fig. 1A).

In contrast, plant height was influenced significantly (p =

0.0017) by soil texture regardless of nitrogen dose or fertilizer

type. Plants grown in clay soil were taller at the end of the

culture cycle than those grown in sandy soil (Fig. 1B).

Nitrogen dose affected significantly the number of

tillers per plant (p < 0.0001) and the number of panicles per

plant (p < 0.0001) The number of panicles per plant was also

impacted significantly (p = 0.0347) by nitrogen doses X

fertilizers interaction (Table 2). In both cases, the relationship

between the independent and dependent variables could be

modeled by quadratic functions. The highest number of

tillers (8.5 per plant) was estimated at a nitrogen dose of 444

mg dm-3 regardless of fertilizer type (Fig. 1C). On the other

hand, the highest number of panicles (7.7 per plant) was

evaluated with a nitrogen dose of 469 mg dm-3 provided by

BUPs, while a maximum of 7.7 panicles per plant were

projected at a nitrogen dose of 358 mg dm-3 when urea was

used as a fertilizer (Figure 1D).

DMA was affected significantly by nitrogen doses (p <

0.0001) and by the interaction soils texture X nitrogen doses

X fertilizers (p = 0.0118; Table 2). In clay soil, only nitrogen

dose impacted DMA values with a maximum production of

43.9 g pot-1 estimated at 527 mg dm-3 of nitrogen (Figure 2A).

In sandy soils, the relationships between DMA and nitrogen

doses for most types of fertilizers could be modeled by

quadratic functions (Figure 2A). The highest levels of DMA

were projected by fertilization with BUP2:1 at a nitrogen dose

of 523 mg dm-3(45.0 g pot-1), with BUP1:4 at 483 mg dm-3

(45.2 g pot-1), or with urea at 392 mg dm-3 (41.3 g pot-1). For

BUP1:2 , the DMA/nitrogen dose response was linear, thus it

was not possible to estimate the maximum production under

these conditions.

DMG was affected significantly by soil texture (p =

0.0013), nitrogen dose (p < 0.0001), and the interaction soils

X fertilizers X nitrogen doses (p = 0.0045) (Table 2). In clay

soil, there were no differences in DMG production between

tested fertilizers, in which the highest level of 47.2 g pot-1 was

evaluated at 594 mg dm-3 of nitrogen (Figure 2B). However,

in sandy soils, the relationships between DMG and nitrogen

doses could be modeled by quadratic functions for most

types of fertilizers (Figure 2B). The highest levels of DMG

were projected by fertilization with BUP1:2 at 495 mg dm-3 of

nitrogen (49.5 g pot-1), with BUP1:4 at 385 mg dm-3(44.8 g pot-

1) or with urea at 541 mg dm-3 (41.4 g pot-1). The

DMG/nitrogen dose response for BUP1:2 was linear, hence

the maximum production under these conditions could not

be estimated.

Table 2. Summary of the joint analysis of variance showing the effects of the three independent variables (soil texture, fertilizers and nitrogen

doses) and their interactions on the characteristics of upland rice production.

Tabela 2. Resumo da análise de variância conjunta mostrando o efeito das variáveis independentes (textura do solo, fertilizantes e doses de

nitrogênio) e suas interações nas características do arroz de terras altas.

Sources of

variation

Degrees of

freedom

Chlorophyll

index

Plant height

(cm)

Tillers

(plant-1)

Panicles

(plant-1)

DMA

(g plant-1)

DMG

(g plant-1)

Replicates

Soil

40.2

211.7

7.0

4.2

107.4

40.8

Soil

13.4

870.9

0.3

2.6

0.4

298.4

Fertilizer

30.2

37.1

1.9

1.8

16.4

19.9

N dose

224.2

49.8

49.2

49.8

1866.8

2400.0

Soil

x Fertilizer

3 28.9ns 194.9ns 0.8ns 1.0ns 19.1ns 86.3*

Soil

x N dose

4 49.2ns 20.5ns 0.7ns 0.4ns 11.5ns 20.5ns

Fertilizer

x N dose

12 14.2ns 42.6ns 15.4ns 1.4* 23.5ns 44.3ns

Soil

x Fertilizer

x N dose

12 79.9ns 148.6ns 1.3ns 0.6ns 53.5* 70.7**

Residue

114

24.7

84.3

0.9

2.8

23.3

27.3

Mean

54.8

123.4

6.8

34.3

35.5

Coefficient of variation (%)

9.1 7.4 14.1 13.1 14.1 14.8

Abbreviations: DMA, dry mass of aerial parts; DMG, dry mass of grains; a - Soil: clay and sandy; b - Fertilizer: BUP2:1, BUP1:2 and BUP1:4 and pure urea;

c - N dose: 0, 75, 150, 300 and 600 mg dm-3 soil; Statistical differences are denoted by * (p < 0.05), ** (p < 0.01) and ns (not significant).

In general, application of BUPs at the lowest nitrogen

doses contributed to high AEI values, particularly BUP2:1 at

150 mg dm-3 of nitrogen in sandy soil (Figure 3A) and BUP1:2

and BUP1:4 at 75 mg dm-3 in clay soil (Figure 3B). Considering

nitrogen doses within the range 150 to 600 mg dm-3, the

mean values of AEI in sandy soil showed a direct relationship

with the proportion of biochar in the formulation (i.e. highest

with BUP2:1 and lowest with BUP1:4). These findings indicate

that biochar improves nitrogen availability and utilization.

However, in clay soil the application of BUPs did not

contribute to increase AEI, which presented rates similar to

those obtained with urea alone.

Magalhães et al.

Nativa, Sinop, v. 10, n. 2, p. 184-190, 2022.

187

Sandy and clay soil; all fertilizers:

y = 0.0105x + 52.491; R2 = 0.879

Sandy and clay soil; all fertilizers:

y = -0.000016x2 + 0.014595x + 5.124712;

R2 = 0.997

Sandy and clay soil:

(•) Urea: y = -0.000026x2 + 0.01853x + 4.3921;

R2 = 0.993

(•) Mean BUPs: y = -0.000015x2 + 0.01435x + 4.70157;

R2 = 0.993

Figure 1. Effects of independent variables (soil texture, nitrogen dose, fertilizer type) on the characteristics of upland rice production: (A)

chlorophyll index; (B) plant height; (C) number of tillers; and (D) number of panicles. Data were obtained for plants grown in sandy and

clay soils. Bars bearing dissimilar lower case letters represent mean values that are significantly different (p = 0.0017). Abbreviation: BUP,

biochar-urea pellets.

Figura 1. Efeito das variáveis independentes (textura do solo, dose de nitrogênio e formulação de fertilizante organomineral) nas

características do arroz de terras altas: (A) índice de clorofila; (B) altura de plantas; (C) número de perfilhos; (D) número de panículas.

Os dados foram obtidos de plantas cultivadas em solo argiloso e arenoso. Letras minúsculas diferentes nas barras indicam diferenças

significativas entre as médias (p = 0.0017). Abreviação: BUP, pellets biochar-ureia.

4. DISCUSSION

The results obtained in the present study showed that

the effects of biochar-urea combinations is depending on the

soil texture. In sandy soil the response of DMG to BUPs at

different doses of nitrogen were similar, except for BUP1:4

which, showed a marked reduction in grain production at the

highest nitrogen dose of BUP, as well as urea. On the other

hand, the effects of BUP1:4 on panicle and DMA production

were equivalent to those of BUP2:1 and BUP1:2. In contrast,

urea alone contribute to reduce panicle and DMA production

at 600 mg dm-3. In clay soil, no differences were detected

between the BUPs regarding production of DMG, DMA,

tillers or panicles. According to Sangoi et al. (2003), clay-rich

soils not only exhibit greater nitrogen retention capacity

compared with sandy soils, but are also more effective in

retaining moisture because of differences in water dynamics.

Hence, leaching losses are lower in clay soils and plants can

better exploit the nitrogen available, contrary to the effects in

sandy soil where nitrogen percolates rapidly through the soil

particles. Jia et al. (2021) state that urea coated with biochar

had controlled nitrogen losses, mainly related to nitrate

leaching, due to the slow release and also by the adsorption

of nitrogen in the pores and functional groups of the surface

of the biochar.

Along the period of the experiments, part of BUPs

remained longer than the urea pellets on the surface of the

soil. The mechanical durability of BUP2:1 and BUP1:2 (≥ 10

kgf) were considerably higher than that of BUP1:4 (1.5 kgf),

and the increased hardness likely contributed to the slow

release of the nitrogen content of the pellets.

Dall’Orsoletta et al. (2017) reported that the loss of

nitrogen through ammonia volatilization from urea ranged

from 10.8 to 13.2% of the total nitrogen applied, regardless

of soil moisture content, and no significant improvement was

obtained when an organomineral fertilizer based on urea

coated with poultry litter was used. Queiroz (2018) compared

NUE values in maize cultivated in a 50% clay soil fertilized

with 13 different OMFs containing biochar as organic matrix

and found no significant differences regarding nitrogen use.

However, the authors reported that, in comparison with

other nitrogen sources, the release of nitrogen from biochar-

urea formulations was slower suggesting that the

organomineral fertilizer had the potential to improve NUE,

especially in sandy soils. Zheng et al. (2013) demonstrated

that, in addition to the physical protection offered by the

biochar-urea pellet, the presence of the organomineral matrix

itself improved NUE in maize by increasing nitrogen

bioavailability in agricultural soils. Such effect is likely due to

The use of biochar-urea pellet formulations to reduced nitrogen losses

Nativa, Sinop, v. 10, n. 2, p. 184-190, 2022.

188

links formed between the nitrogen of the fertilizer source and

the surface of the biochar matrix (Shi et al., 2020).

Considering treatment BUP1:4 with 600 mg dm-3 of

nitrogen, the amount of biochar applied to the soil

corresponded to 667 kg ha-1, while for BUP2:1 the amount

of biochar applied is 8-times greater (5,333 kg ha-1).This

comparison is important because the feasibility of using

biochar must take into account the cost-benefit, since the

BUP production must, at the least, be equivalent to the

financial returns of its use. Despite evidence that biochar

improves AEI, there are little information about the cost of

production of the organomineral fertilizer, thus the

economics concerning its use require careful assessment. In

addition to the direct benefits of BUPs on crop yield, it is

important to emphasize the environmental contribution of

OMFs technology to the mitigation of N2O emissions as well

as the fixation of atmospheric CO2. Further research in this

field should be encouraged with particular emphasis on

reducing the production costs of biochar.

Clay soil:

(•) All fertilizers:

y = -0.00007*x² + 0.0738**x + 24.4

R2 = 0.99

Sandy soil:

(•) BUP2:1: y = -0.00008*x² + 0.0837**x + 23.1

R2 = 0.96

(•) BUP1:2: y = 0.02751**x + 29.6

R2 = 0.95

(•) BUP1:4: y = -0.0001**x² + 0.0966**x + 21.9

R2 = 0.92

(•) Urea: y = -0.00012**x² + 0.094**x + 22.9

R2 = 0.96

Clay soil:

(•) All fertilizers:

y = -0.000058*x² + 0.0689*x + 26.7

R2 = 0.99

Sandy soil:

(•) BUP2:1: y = 0.0437**x + 25.0

R2 = 0.96

(•) BUP1:2: y = -0.00011**x² + 0.109**x + 22.5

R2 = 0.99

(•) BUP1:4: y = -0.00016**x² + 0.1232**x + 21.1

R2 = 0.99

(•) Urea: y = -0.000065*x² + 0.0704**x + 22.3

R2 = 0.89

Figure 2. Effects of independent variables (soil texture, nitrogen dose, fertilizer type) on the characteristics of upland rice production:

(A) dry mass of aerial parts (DMA); (B) dry mass of grains (DMG). Data were obtained for plants grown in sandy and clay soils. Abbreviation:

BUP, biochar-urea pellets; *, p < 0.05; **, p < 0.01.

Figura 2. Efeito das variáveis independentes (textura do solo, dose de nitrogênio, tipo de fertilizante) nas características do arroz de terras

altas: (A) massa seca da parte aérea (DMA); (B) massa seca de grãos (DMG). Os dados foram obtidos de plantas cultivadas em solo argiloso

e arenoso. Abreviação: BUP, pellets de biochar-ureia; *, p < 0.05; **, p < 0.01.

Figure 3. Agronomic efficiency index (AEI) of different formulations of biochar-urea pellets (BUPs) in (A) sandy soil and (B) clay soil. Bar

designations: () BUP2:1; () BUP1:2; () BUP1:4.

Figura 3. Índice de eficiência agronômica (AEI) de diferentes formulações de pellets biochar-ureia (BUPs) em (A) solo arenoso e (B) solo

argiloso. Cores das barras: () BUP2:1; () BUP1:2; () BUP1:4.

Magalhães et al.

Nativa, Sinop, v. 10, n. 2, p. 184-190, 2022.

189

5. CONCLUSIONS

This study study demonstrated that soil texture plays a

key role in the performance of biochar-urea pellets (BUPs).

In sandy soil, the yields of rice obtained with BUPs were

either equivalent to or greater than those obtained with urea

alone. The best performance in sandy soil was observed with

the application of BUP2:1, showing that the biochar-urea ratio

is relevant for improving the Agronomic Efficiency Index.

6. FUNDING

The study was partially funded by Fundação de Amparo

à Pesquisa do Estado de Mato Grosso (FAPEMAT; grant no.

0585720/2016) and Conselho Nacional de Desenvolvimento

Cientifico e Tecnológico (CNPq) third author research

productivity grant PQ1D n.° 304621/2017-0.

7. REFERENCES

AGEGNEHU, G.; NELSON, P. N.; BIRD, M. I. The

effects of biochar, compost and their mixture and

nitrogen fertilizer on yield and nitrogen use efficiency of

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