Incidence of rice (Oryza sativa l.) cultivation on soil

hydrophysical properties

Incidencia del cultivo de arroz (Oryza sativa l.) sobre las

propiedades hidrofísicas del suelo

Yoansy Garcia

Daniel Mancero

Daniel Ponce de León

Miguel Guaranda

Abstract: Rice is one of the most important crops in Ecuador and also

one of those that cause the greatest degradation of soil properties. In

this sense, the effect of rice cultivation on soil hydrophysical

properties was evaluated in the Bejuco Prieto area of Samborondón

canton, Guayas province. A completely randomized design with two

treatments and three replicates was used: treatment 1 corresponded to

the use of soil for rice cultivation and treatment 2 was the control

(virgin soil used to compare the degree of degradation). The results

obtained for the first treatment indicate a clayey soil texture, apparent

density of 1.13 Mg m

-3

, real density of 2.61 Mg m

-3

, total porosity of

55.33%, moisture content of 45%, structural index of 6.6%;

suggesting that the soils are at risk of soil degradation. In addition, the

structural factor was 69.9%, organic matter was 3.08%, sodium

content in the soil was 104 ppm and sodium in the water sample was

14.08 ppm. The electrical conductivity in saturated paste was 6.8 dS

-1

and in water it ranged between 0.8 and 1.7 dS m

-1

while pH was

between 6.0 and 7.0. Of the hydrophysical parameters evaluated,

electrical conductivity, sodium content, structural stability and

organic matter loss were found to be the most sensitive to the

deterioration of soil hydrophysical properties. Consequently, it can be

affirmed that rice cultivation accelerates soil degradation, which

reduces production, increases costs and decreases profitability.

Keywords: Stable aggregate, moisture content, real density, soil

structure, hydrophysics.

Published

Instituto Tecnológico Superior Edwards

Deming. Quito – Ecuador

Periodicity

April - June

Dates of receipt

Received: January 01, 2023

Approved: March 23, 2023

http://centrosuragraria.com/index.php/revista

vol. 2. Num. 18. 2023.

pp. 55-67

Correspondence author

dmancero@uagraria.edu.ec

Creative Commons License

Creative Commons License, Attribution-

NonCommercial-ShareAlike 4.0

International.https://creativecommons.org/lice

nses/by-nc-sa/4.0/deed.es

1 Jacobo Bucaram Ortiz, Ph.D, Agrarian University of Ecuador. yogarcia@uagraria.edu.ec, https://orcid.org/0000-0002-2839-3956

2 Msc.

Instituto de Investigación Ing. Jacobo Bucaram Ortiz, Ph.D, Universidad Agraria del Ecuador. dmancero@uagraria.edu.ec,

https://orcid.org/0000-0003-3917-1811

3 Msc. Faculty of Agricultural Sciences, St. Helena Peninsula State University. dponcel@upse.edu.ec, https://orcid.org/ 0000-0002-7798-

1551

4 Student of Agronomy Engineering, Faculty of Agrarian Sciences, Agrarian University of Ecuador. mguaranda@uagraria.edu.ec,

https://orcid.org/0000-0003-1323-5290

Incidence of rice (Oryza sativa l.) cultivation on soil

hydrophysical properties

Resumen: El arroz es uno de los cultivos más importantes del

Ecuador y también, uno de los que provocan mayor degradación de

las propiedades edáficas. En este sentido, se evaluó el efecto del

cultivo de arroz sobre las propiedades hidrofísicas del suelo en el

recinto Bejuco Prieto del cantón Samborondón, provincia del Guayas.

Se empleó un diseño completamente aleatorizado con dos

tratamientos y tres repeticiones: el tratamiento 1 correspondió al uso

de suelo para cultivo de arroz y el tratamiento 2 fue el testigo (suelo

virgen utilizado para comparar el grado de degradación). Los

resultados obtenidos para el primer tratamiento indican una textura

del suelo arcillosa, densidad aparente de 1,13 Mg m

-3

, densidad real

de 2,61 Mg m

-3

, porosidad total de 55,33%, contenido de humedad

del 45%, índice estructural de 6,6%; lo que sugiere que los suelos

están en riesgo de degradación edáfica. Además, el factor estructural

fue del 69,9%, la materia orgánica del 3,08%, contenido de sodio en

el suelo de 104 ppm y el sodio en la muestra de agua es de 14,08 ppm.

La conductividad eléctrica en pasta saturada fue de 6,8 dS m

-1

y en el

agua osciló entre 0,8 y 1,7 dS m

-1

mientras que el pH estuvo entre 6.0

y 7.0. De los parámetros hidrofísicos evaluados, se encontró que la

conductividad eléctrica, el contenido de sodio, la estabilidad

estructural y la pérdida de materia orgánica son los más sensibles al

deterioro de las propiedades hidrofísicas del suelo. En consecuencia,

se puede afirmar que el cultivo del arroz acelera la degradación del

suelo, lo que reduce la producción, aumenta los costos y disminuye la

rentabilidad.

Palabras clave: Agregado estable, contenido de humedad, densidad

real, estructura de suelo, hidrofísicos.

Introduction

Agriculture is a human activity that has evolved over thousands of years

and has become one of the most important sources of food production

for the world's population. However, it is important to note that it can

also have negative effects on the environment, especially in relation to

soil. In particular, agriculture can cause major soil contamination and

degradation, which is largely attributable to inadequate land

management and the use of agrochemicals on crops. In Ecuador, the

expansion of the agricultural sector is constantly growing, and a wide

variety of crops are grown, which has generated a wide range of

negative impacts on the hydrophysical properties of the soil. Such a

variety of crops implies different agricultural practices, and therefore,

diverse forms of soil management and agrochemical use, which

complicates the identification and evaluation of negative impacts on the

soil (Delgado et al., 2020).

July - September vol. 1. Num. 18 - 2023

Land cultivation in Ecuador has increased considerably in recent years,

and this has generated a high susceptibility to soil degradation in

cultivated soils. Consequently, it is essential to deepen studies to

evaluate the influence of agricultural operations on the quality of

agricultural soils, particularly in those cases where there is a higher soil-

water ratio, as in the case of rice cultivation. To address this problem of

soil deterioration, it is essential to recognize the importance of studying

hydrophysical parameters, which are determinant in soil degradation

processes. Therefore, it is crucial to address the investigation of these

parameters in order to advance in the search for solutions to the problem

of soil deterioration in agricultural soils (Cobos Mora et al., 2021)..

In Ecuador, there is growing concern about the deterioration of

agricultural soils, which affects their physical, chemical and biological

properties, leading to a decrease in fertility, productivity and

regenerative capacity of the soil. In particular, the decrease in their

capacity to recover after long periods of cultivation is of concern, which

has become a major challenge for the sustainability of agriculture in the

country (García et al., 2022).

The causes of soil degradation are rooted in socioeconomic factors,

overexploitation of land use capacity, and inadequate soil and

inappropriate water management practices (Baude et al., 2019).

It is well known that rice farming is one of the most aggressive

agricultural activities on the soil environment. According to studies

carried out show that if conservation practices are not carried out on

these soils, in a few years the agro-productive properties - together with

the crops - will not be profitable (Sione et al., 2017).

The type and rate of soil degradation are determined by the use and

management imposed on the soil, so it is important to identify the

hydrophysical properties that are affected and the degrading processes

caused by human action (Díaz et al., 2009). (Díaz et al., 2009)..

It is known that soil compaction increases bulk density (DA), causing

in turn an increase in mechanical resistance, decreasing total porosity,

favoring the risk of soil erosion by runoff. (Lima et al., 2009).

Soil aggregates in turn give rise to pore spaces of different designs and

sizes. The frequency of agricultural activities greatly affects the binding

agents of soil aggregates, among which we can mention: organic debris,

fungal hyphae and rhizospheric organisms. It is in these pore spaces

where air and water are available for the normal development of plants

and their productivity (Qi et al., 20). (Qi et al., 2022).. The effective

depth, texture, structure, total porosity and macroporosity, apparent

density, real density, internal drainage, presence of water table, are

parameters that are related to a greater or lesser degree and affect the

Incidence of rice (Oryza sativa l.) cultivation on soil

hydrophysical properties

hydrophysical properties of the soil (Blanco-Canqui & Ruqui, 2022).

(Blanco-Canqui & Ruis, 2020)..

Agricultural activity has negative effects on the physical, chemical and

biological properties of the soil, where the importance of the first

horizon of the soil and subsoil profile stands out in order to understand

the impact of this phenomenon. Alteration of porosity, compaction and

water retention capacity are changes associated with the first horizons

of degraded soils, which limit the growth and elongation of the crop

root system. These factors, along with other processes, are essential for

the intrinsic capacity of the soil to resist and recover from agricultural

damage (Blum, 1997). (Blum, 1997). In this sense, the objective of this

research was to evaluate the effect of rice cultivation on soil

hydrophysical properties.

Materials and methods

Three sectors of the Bejuco Prieto area in the canton of Samborondón

dedicated to rice cultivation were selected (coordinates 642086m,

9784585m WGS84 UTM 17S). Each site had at least one hectare in

production.

In this study, a completely randomized design was used to compare the

two treatments: Commercial Rice Cultivation (T1) and Undisturbed

Forest (T2). Three replicates of each treatment were carried out and

three composite samples were collected per replicate, each composed

of 10 subsamples. In total, 18 composite samples were obtained,

consisting of 180 subsamples throughout the experiment.

At each research site, sampling locations were established using a

zigzag pattern. A Riverside type auger was used for sampling, the

sampling depth was 20 cm. The samples were then subjected to a

mixing, quartering and labeling process and were sent to the laboratory;

this procedure is recommended by MAGAP (2020).

Table 1. Treatment evaluation variables and methodology

Indicators

Method

Structural Stability

Pieri Index (1995)

Structure factor

Vageler and Alten (1931)

Soil texture

Bouyoucos method (Soil Survey Staff, 2022)

Bulk density

Gravimetric method (Soil Survey Staff, 2022)

July - September vol. 1. Num. 18 - 2023

Table 2 shows the interpretation of Pieri's index to establish the

structural state of the soil.

Table 2. PIERI Structural Index 1995

Structural

condition of

the soil

Value

Detail

Degraded

Soils

< 5

These soils are highly susceptible to

erosion and physical degradation.

Highly

Susceptible

Soils

5 a 7

These soils are at high risk of physical

degradation due to the formation of hard

clay crusts on the surface, compaction

and erosion.

Slightly

Susceptible

Soils

7 a 9

They are soils with slight physical

degradation

Structurally

Stable Floors

> 9

These soils are relatively stable and have

an important organic carbon content.

Organic matter was determined by the Walkley-Black (Wet

Combustion) method, which is the most widely used method. The

determination consists of the oxidation of organic carbon by an

Actual density

Pycnometric method in water (Soil Survey Staff,

2022)

Porosity

Calculation from bulk density and real density

Soil pH

pH in water (1:2.5) (Soil Survey Staff, 2022)

Total organic

carbon

Wet digestion (Walkley & Black, 1934)

Soil electrical

conductivity

Conductometry (Soil Survey Staff, 2022)

Na on the ground

Adapted HACH method for Na

pH of the water

film

HACH potentiometric method

Electrical

conductivity of the

water film

HACH conductimetry method

Na of the sheet of

water

HACH potentiometric method with sodium selective

probe

Incidence of rice (Oryza sativa l.) cultivation on soil

hydrophysical properties

oxidizing mixture of potassium dichromate (K

Cr O

) and

concentrated sulfuric acid (H

). The supernatant is then taken from

the samples and taken to the colorimeter for subsequent reading in

carbon content, which is then converted to organic matter.

For pH, a soil preparation was made and allowed to stand for 2 hours

for subsequent analysis, in the electrical conductivity and sodium

values were measured from the preparation of the soil paste that rested

for 24 hours, then filtered and saturation extract readings were made.

For the water analysis, a direct analysis of the sample was made using

the HACH multiparameter equipment.

It was determined by the gravimetric method, the wet samples were

dried at 105

C to stable weight and the calculation was made using the

following equation

!"#$%&%'()&*+#,-)+.& /'

12 34!

6012 3425

12 342

312

PC: Capsule Weight, SH: Soil Moist, SC: Soil Dry at 105 C

Structure factor

The structural stability of the soil was determined by the method of

Vagaler and Alten, in this procedure the amount of clay that acts as a

cementing agent of the soil structure is determined, using a dispersant

(Sodium hexametaphosphate) and an undispersed soil (only water) are

used and the Bouyoucos technique is followed. If the clays contained

are involved in the formation of the structure, the factor is said to be

100%, and if they are the average, they are characterized with 50%. The

following formula is applied:

7&.-8)' $9-)".-")& / :

;6<'

='>'?@@'

Soils are classified as having a good structure when they contain a

percentage of 80 to 100% (humic and oxisols) and as poor when they

contain 50 to 60% (vertisols and hydromorphic), the higher the value,

the greater the soil's capacity for aggregation.

Statistical analysis

The normality of the data was evaluated using the Shapiro-Wilk test,

and homogeneity of variance was tested using the Levene test.

Comparison of means was performed using Student's t-test. A

significance level of 5% was used for all statistical procedures. All

analyses were performed in the R Studio program (version 2022.07.2)

(RStudio Team, 2022).

July - September vol. 1. Num. 18 - 2023

3. Result

The soil texture for both treatments was clayey. Figure 1 shows the

values obtained for the bulk density and real density properties for the

different soil uses.

Figure. 1 Effect of land uses Rice cultivation and Undisturbed soil on

bulk density and true soil density.

The results show that the average bulk density for treatment T1 was

1.13 Mg m

-3

, while for treatment T2 it was 1.29 Mg m

-3

. However, no

significant statistical difference was found between these two

treatments. The real density had a similar behavior, in T1 it was 2.61 g

-3

and in T2 it was 2.15 g cm

-3

and no significant difference was

found (p<0.05). The apparent and real density determine the degree of

soil compaction, this property is related to many aspects of the

hydrophysical environment (Manrique & Jones, 1991). (Manrique &

Jones, 1991). Both results remained in an acceptable range, and

coincides with that reported by Kalita et al. (2020)who in their research

observed a bulk density of 1.30 Mg m

-3

in the rice crop.

The relationship between bulk density and actual density determines the

total porosity of the soil; therefore, no significant difference (p<0.05)

was found in this variable (Figure 2). Porosity in T1 was 53.33% and in

T2 43.7%; however, field moisture was 45.33% and 19.33% for T1 and

: Different letters indicate significant differences, according to the

Student's t-test (p= 0.05).

Densidad aparente Densidad real

Mg m

-3

Cultivo de arroz (T1)

Suelo sin perturbar (T2)

n.s

Incidence of rice (Oryza sativa l.) cultivation on soil

hydrophysical properties

T2, respectively. This indicates that the soil cultivated with rice had a

high level of water saturation at the time of sampling, in contrast to the

undisturbed soil, which had lower moisture.

Figure 2. Effect of land uses Rice cultivation and Undisturbed soil on

field moisture and total porosity.

Excess moisture in soils is a degrading factor, which causes the

dispersion of clays and, therefore, a detriment to the structure and the

rest of the physical properties (Amezketa et al., 2003). (Amezketa et al.,

2003)..

This is intensified if there are elements that have dispersing power, such

as Na. Table 3 shows the effect of the soil uses studied on the chemical

properties evaluated. The Na content in the rice crop presented very

high values with respect to the undisturbed soil (difference of 89.90%),

which leads to a significant increase in the electrical conductivity of the

soil (difference of 74.33%). In this sense, it can be seen that these two

variables have a significant weight on the degrading processes of the

rice soil; in addition, several authors state that from a conductivity of

3.0 ds m

-1

a significant decrease in yields begins and increases by 12%

: Different letters indicate significant differences, according to the

Student's t-test (p= 0.05).

Humedad campo Porosidad total

Cultivo de arroz (T1)

Suelo sin perturbar (T2)

n.s

July - September vol. 1. Num. 18 - 2023

for each unit of electrical conductivity. Salinity is a component that

must be properly managed since the detrimental effects vary according

to the vegetative stage of the crop, being the most affected the initial

stages, but the damage is maintained until harvest (Zeng & Shannon,

2000). (Zeng & Shannon, 2000). There were no significant differences

in pH among the treatments under study.

Table 3. Effect of land uses Rice cultivation and Undisturbed soil on

Na, electrical conductivity and soil pH.

Land use

Na soil

(ppm)

Diff.

(%)

C.E soil

(dS m )

-1

Diff.

(%)

Soil pH

Diff.

(%)

Rice

cultivation

104.00±8.2

89.9

6.86±0.5

74.3

6.14±0.7

2.44

Undisturbed

soil

10.45±2.15

1.76±0.2

6.29±0.8

Difference

: Different letters indicate significant differences, according to the

Student's t-test (p= 0.05).

The sodium content in the soil can be increased by the use of irrigation

water with high concentrations of this element; and poor management

of the washing fraction of salts. Another factor is the use of fertilizers

with high salt index, Das et al. (2015) state that the problem is

exacerbated after fertilizer application, during droughts or arid

conditions. If the soil is allowed to dry out too much for a few hours, it

can also cause salinity damage. However, the greatest effect of high salt

content in the soil is usually manifested in the roots.

Effect of land uses Rice cultivation and undisturbed soil on soil organic

matter, structural stability and structure factor.

Land

use

MOS* MOS* MOS* MOS*

MOS

E.A*

ff.

. ¥

F.E**

ff.

. ¥

Rice

cultivati

3.08±0.22

6.86

±0.5

69.21

±8.74

Incidence of rice (Oryza sativa l.) cultivation on soil

hydrophysical properties

Undistu

rbed

soil

5.22±0.37

8.53

±0.2

81.30

±11.4

*Soil organic matter, **Aggregate stability, ***Structure factor,

Difference

: Different letters indicate significant differences, according to the

Student's t-test (p= 0.05).

The level of organic matter was lower in the rice crop by 40.99% (Table

4.), which indicates that the humification processes are affected by this

type of soil use. Another relevant aspect is how the structural stability

was affected in this type of crop, a decrease of 19.57% was evidenced

with respect to undisturbed soil, also in Pieri's scale it corresponds to

"Highly Susceptible Soils". This leads to an increase in erosive

processes and severe degradation processes. Consequently, a detriment

of the soil structure develops, which can be corroborated with the

structure factor variable, which had a decrease of 14.87 %. The data

obtained in the research coincide with those reported by Singh et al.

(2023)These authors indicate that salt content significantly affects

structural stability and MOS content in rice soils.

The pH of the irrigation water was 7.26, the electrical conductivity was

1.31 dS m

-1

and Na was 12.65 ppm. This shows that one of the factors

that most affect the salinization of these soils and the deterioration of

their physical properties is the use of hard water with a high saline level.

Therefore, a management system should be considered to improve the

efficiency of the use of water resources and reduce the effect on the

environment - in this case, the soil.

4. Conclusions

Rice cultivation favors soil degradation, as there was evidence of an

increase in electrical conductivity, sodium content and a decrease in

structural stability (stable aggregates) and organic matter content.

Structural stability, salinity and organic matter content are the

hydrophysical properties most sensitive to soil management in this

study, and can be used as an indicator of the quality of the soil

environment.

July - September vol. 1. Num. 18 - 2023

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