Original Article

Productive yielding in agroecosystems of cassava-beans alternation in “Calixto García” municipality, Holguín province

M.Cs. Sebastián Zayas-Infante^{1  *} 

Dr.C. Pascal Boeckx² 

Dr.C. Heriberto Vargas-Rodriguez³ 

¹Centro Universitario Municipal “Calixto García”. Universidad de Holguín, Cuba

²Laboratorio Isotópico de Biociencias, Universidad de Ghent, Bélgica

³Universidad Agraria de La Habana “Fructuoso Rodríguez Pérez”, carretera a Tapaste y Autopista Nacional. San José de las Lajas. Mayabeque, Cuba

ABSTRACT

ABSTRACT • This work was developed in productive areas of the municipality “Calixto García", county Holguín, a study was carried out to determine the behavior of the yields in systems of cassava-beans alternation, the objective of the work consisted on evaluating the productive behavior in intercropping of both cultivations in the municipality. This investigation was developed in the cultivations cassava clone “Selección Holguín” and bean variety Carita Blanco with a cycle of 270 days for the cassava and 70 days for the bean it has more than enough alkaline soils. The following indicators were evaluated: quantity of tuberous roots for plant, weight average for plant, yield of the cultivation in t ha^-1, presence of nodules in the system radicular of the bean, the Index of Efficiency of the Earth (IET) and the economic evaluation. The reached results showed differentiated answers of the indicators evaluated in each treatment, standing out the treatment II (mixed fertilization starting from the combination of organic matter to reason of 5 t ha^-1 and micro fertilizer dose with the help of it formulates complete to reason of 10 g for plant with bean alternation) with more yields, results economic and bigger presence of nodules on the rest of the treatments.

Key words: yield; alkaline soil; Cowpea; Soil organic matter; Manihot esculenta; Vigna unguiculata

INTRODUCTION

The production of food takes on a decisive importance in the current era in the face of the accelerated increase of the world population, which is why the fight against hunger predominates among the objectives of the millennium. It is estimated that around 600 million people in the world are undernourished ¹.

Cassava (Manihot esculenta Crantz) is a very widespread crop in the world, with a large presence in Africa, America and the Caribbean and it is one of the traditional crops and most widely used in these geographical areas and it is part of the food base of more than 600 million people in the tropical regions of the world ². It is grown in more than 90 nations, being highly valued for its contribution to food security in many tropical countries with a world production of more than two million tons per year ^3-5. On the other hand, the Cowpea bean (Vigna unguiculata L, Walp) is a grain legume widely used in agriculture in Cuba, the economic importance of this crop for the country is given by two fundamental reasons: it is a source of vegetable protein consumption animal and human and their foliage are very often used as green fertilizers ⁶.

Currently the increase in the effects of climate change has contributed to the enhancement of the benefits of both crops, cassava, especially for its resistance to high temperatures, pests and diseases and large periods of drought, as well as high adaptability to a wide range of crops. range of soil conditions ⁷ and in the case of beans, is an option because its rusticity allows it to establish itself relatively easily in adverse environments and with tolerance to drought, high temperatures, heavy metals and salt stress, but also it can contribute an appreciable amount of nitrogen (150 kg N ha^-1) of symbiotic fixation to the ecosystem ⁸.

Cassava, due to its physiological characteristics, at the beginning of its vegetative cycle, does not efficiently use the light, water and nutrients factors, so its intercalation with a short cycle crop is possible. Similarly, in the final phase of development something similar occurs, which also allows the intercalation of crops and with it a more efficient use of physical space ^9,10.

This practice is very common in many tropical and subtropical countries since the presence of different species simultaneously in the same area contributes to maintain the balance of soil nutrients and increases fertility. In this regard, it is argued that the general economy of the agricultural exploitation benefits as a consequence of the diversification of crops and the possibilities of output of different products ^10,11.

In Cuba, production technologies for this crop persist, with which the vital area is not fully exploited. This can be reversed if the technology of associated crops is used in the early stages of their development given their physiological behavior at this stage ¹². In this sense, there are experiences of different associations of crops with cassava, so a study of the behavior of the yield and its components in intercalation with corn and beans was carried out ¹². Similarly, studies were conducted with efficiently mycorrhized legume species associated with cassava in Guantánamo province ^13).

In “Calixto García” municipality, cassava is the second most important crop with productions that reach 4845.6 tons in the non-state sector, surpassed only by plantain ¹⁴. However, it has not been generalized among producers to take advantage of the potential that it offers to intercalate crops in their first stages of their life cycle. On the other hand, recent studies have shown the influence of several soil indicators in the development of this crop from its analysis in four farms, located in the center and south of “Calixto García” municipality (Padierne, Monte Alto, Cruce de Mir and La Mananina).

The results show the low fertility of the soil, the existence of salinity, high pH or alkalinity among other indicators that affect its productivity. Although not all farms are similar manifestations are identified as fundamental causes inadequate soil management given by excess chemical fertilizers, irrigation with saline water, not rotate the soil properly, among other limiting factors. For all the above, the objective of the work focuses on evaluating the productive behavior in cassava-beans intercropping in “Calixto García” municipality.

MATERIALS AND METHODS

Characterization of “Calixto García” municipality

“Calixto García” municipality is located geographically to the west of Holguín province has a surface area of 591.0 km², the total population is 55 701 inhabitants for a population density of 94.2 inhabitants per km². Approximately 80 % of the territorial economy is based on agricultural production, so there is an agricultural culture, the hydrographic network is scarce and its main basin is the Rioja River, which in turn is part of Cauto river basin.

The precipitations oscillate between 800 and 1200 mm/year, with an increase in the duration of the dry periods that extend sometimes up to 210 days; The average annual temperature is 36.7 ˚C. In the municipality there are several types of soils but the Sialitic Brown predominate with the presence of limiting factors such as salinity and alkalinity. In the territory is tradition the cultivation of the typical food and tubers between which stand out the banana and the cassava, statistical data provided by the Delegation of the Agriculture corroborate that the productions of cassva occupy significant place within them and in the case of the bean, despite not constituting a predominant line within the grains, discrete productions are obtained (Figure 1).

Figure 1 Production of cassava and beans obtained in the municipality of “Calixto García” in the 2010-2015 season 

The experience was developed in La Alegría town and began in the month of November 2015 until September 2016, on a Brown Sialitic soil with a high alkalinity (pH 8.2). The selected cassava clone was "Selección Holguín" and the variety of beans "Carita Blanco". Experimental plots of 40 m² were used. The applied fertilization was organic matter at a rate of 5 t ha^-1 and microdoses of complete formula (NPK) at a rate of 10 g per plant. It was applied in a circular way around each plant and covered with soil. In all the cases in which fertilization was applied, it was the cassava crop and it was carried out one month after planting. The treatments used are similar to those used in previous studies developed in intercropping systems with cassava cultivation ¹⁵.

The treatments used are shown in Table 1.

Table 1 Treatments used in the experiment 

Treatment	Spatial arrangement of cassava (m)	Bean population per hectare	Planting distance of the bean
Control Without fertilization	0.90 x 0.70	-	-
Treatment I Organic fertilization (5 tha^-1)	2.0 x 0.50	111111	0.45 x 0.20
Treatment II Organic Fertilization (5 tha^-1) + microdoses de NPK (10 g plant^-1)	2.0 x 0.50	111111	0.45 x 0.20

The variables to be evaluated and the procedure used were:

In the cultivation of cassava:

• • Number of tuberous roots per plant: the counting of the tuberous roots was carried out at the time of harvest.

• • Mass of the tuberous roots per plant in kg: to estimate this indicator, the average mass was calculated by dividing the sum of all the measurements between the numbers of plants in each plot.

• • Yield per treatment: the total weight of the tuberous roots was determined for each experimental plot in kg m^-2 and its conversion was made to t ha^-1.

In the bean:

• • Yield per treatment: when harvested, determined the total mass of the grains for each experimental plot in kg m² and converted it to t ha^-1.

• • Number of nodes per plant: for the counting of the existing nodules, the extraction of each plant to be sampled at the time of flowering was carried out and the nodules existing in each plant were counted.

When harvesting the bean, the harvest remains were deposited in the trunk of the cassava plants in the corresponding plot.

The Equivalent Earth Index (IET): it was determined by the following expression

$\text{IET}=\text{Ix}+\text{Iy}=\frac{\text{Rxa}}{\text{Rxu}}+\frac{\text{Rya}}{\text{Ryu}}$

where: Ix + Iy are the IET Individual crops (x) cassava and (and) legume.

The Rxa and Rya are the yields of the associated crops and the Rxu and Ryu are the historical yields of the non-associated crops, according to the methodology described ¹³. As yield in monoculture of the species the historical yields for the zone were taken, being of 9.1 and 0.7 t ha^-1 for the yucca and the Cawpea respectively, while for the polyculture the yields reached in the investigation were used.

The data of the variables number of roots per plant, mass of the tuberous roots per plant and yield per treatment, were subjected to an analysis of variance. A randomized block experimental design with three treatments and three replicas was used

The means of the variables were compared by the Tukey test (p <0.05), using the statistical program SPSS 13.

RESULTS AND DISCUSSION

Quantity of tuberous roots by plant

In the control, an average of 5.3 roots per plant was reached, while in treatment I an average of 4.7 roots per plant was reached and in treatment II of 4.8 roots per plant respectively (Table 2). This decrease in treatments with bean intercropping is due to the fact that it is possible that interspecific competition has occurred by increasing the interaction that occurred between the species, due to the higher density of plants and therefore the substances that are produced for the formation of the roots will decrease. Although they evaluated different cassava clones; in the south of India, similar results were observed since in evaluating this aspect they found that the monocultures reached the highest values of roots by plants in relation to intercropping ¹⁶. However, recent results did not find significant differences in this indicator when evaluating different plantation settings in cassava cultivation ¹⁷.

Mass of the tuberous roots by plant

As shown in Table 2 in the control, an average mass of 1.93 kg is reached; in the treatment I 2.67 kg and in the treatment II 3.21 kg respectively. This indicator is best observed in systems with bean intercropping and is attributed to the use of larger plantation frames in the cultivation of cassava and the combined action of organic and chemical fertilization. The average mass of roots per plant was favored by intercropping with beans, corresponding to systems where cassava was planted most widely the highest values, while where smaller spatial arrangements were used suffered a reduction. On the other hand, in studies carried out in sub-Saharan Africa, higher values of the average mass of roots per plant were obtained in plots where the combined fertilization of microdoses of complete formula and organic fertilizers was used ^17,18. In studies carried out in the Democratic Republic of the Congo, similar results were achieved in relation to this indicator with the use of intercropping systems of different cassava crops ¹⁸.

Yield

In the cassava crop, the yields behaved as shown in Table 2.

Table 2 Components and yield of cassava "Holguín Selección" in intercropping systems with "Carita blanco" beans 

Treatments	Number of roots/plant	Mass of roots/plant (kg)	Yield (t ha^-1)
Control	5.3ª	1.93ª	7.3ª
Treatment I	4.7b	2.67b	11.2b
Treatment II	4.8b	3.21c	16.7c
Es x	0.75	0.12	1.6
CV %	12.8	16.3	18.6

* Uneven letters in the rows for each column differ for p≤0.05

The results show that there are significant differences between the two treatments and the control in terms of performance. In this way, Treatment II was the one that reached the highest yields with values of 16.7 t ha^-1, followed by treatment I and the control with 11.2 and 7.3 t ha^-1, respectively. This increase in treatment II is attributable to the combined action of organic and chemical fertilization based on the complete formula and to the contribution of nitrogen produced by the decomposition of bean crop residues incorporated into the cassava rows. These results coincide with those achieved by researchers from the National Institute of Agricultural Sciences (INCA) who found it beneficial to include legumes in the intercropping systems in economic crops, since it improves the nutrition of the plants and contributes to increase the nutrients in the soil, fundamentally the nitrogen.

Similar results were obtained in studies carried out in eastern Uganda to obtain increases in the yields of crops associated with velvetbean (Mucuna pruriens) and accumulated up to 50 % of nitrogen taken from the atmosphere and contributed to the soil by means of biological fixation. (BNF), as well as, they report increases in yield in the range of between 3 and 5 t ha^-1 in the cassava crop with the combined use of green manure and manure ¹⁹, these are attributable to the increase in concentration of potassium and the improvement of the physical properties of the soil, which promotes an increase in the storage capacity and therefore in the thickening of the roots.

Likewise, they report increases between 8 and 12 % in cassava yields with the use of bean and maize intercrop ^19,20, while recent studies obtain adequate results with the application of bean harvest remains in the rows of cassava ²⁰.

On the other hand, other investigations report a relation of proportionality between the availability of organic nutrients and the yields of the cassava crop in intercalation systems ^20).

In the case of beans, yields behaved similarly with 0.46 t ha^-1 for treatment I and 0.6 t ha^-1 in treatment II respectively.

Equivalent index of the earth

In systems with cassava intercrop with beans, very advantageous land efficiency indices are achieved. In this sense, for the case of plots with intercalation and organic fertilization (treatment I), 1.88 is obtained; while for the intercropping of cassava and beans with the combined use of organic fertilization plus micro-dose of NPK (treatment II) an index of 2.32 was reached.

This shows that the intercropping of crops allows to obtain increases of this indicator in relation to monoculture ^21). Similarly, in Guantánamo, similar results were obtained by obtaining Land Efficiency Indices (ETI) favorable for cassava-Phaseolus and cassava-Cawpea associations with values of 1.67-2.12; all of which ratifies the efficiency of the design used for the use of polycultures.

Similar results were obtained in cassava intercrop systems with other crops, by observing in general higher rates of equivalence of the land in cassava intercropping with other crops ²¹.

Behavior of the number of nodules in bean cultivation

The evaluation of the nodulation in the bean crop was carried out in the flowering stage, which is where this characteristic manifests with greater intensity in the legumes (Table 3).

Table 3 Behavior of number of nodules per plant 

Treatment	Presence of nodules	Average nodules per plant
Treatment I	Yes	19.2
Treatment II	Yes	31.5

As shown in Table 3 in the treatment where combined fertilization of organic matter and microdose of chemical fertilizer is used, a greater number of nodules per plant is obtained in relation to the treatment with organic fertilization, results that show similarity with those reached during the study of the behavior of biological nitrogen fixation by six bean varieties in Ethiopia ²², who report differences in the number of nodules in each evaluated variety, reaching a greater number of nodules, as well as an increase in the nitrogen concentration of up to 65.3 mg per plant in the treatment where the combination of organic fertilization with chemical was used.

Economic valuation

As can be seen in Table 4, an increase of 18593.94 CUP is achieved as a result of sales of treatment II over the control and, in general, in both treatments a substantial increase in the amount due to sales compared to the control is achieved.

Table 4 Revenues reached for sales in both crops 

Treatments	Yield (t ha^-1)		Sale price in (CUP t^-1)		Total value in the production (CUP ha^-1)		Total amount for sales (CUP ha^-1)
	Cassava	Bean	Cassava	Bean	Cassava	Bean
Control	7.3	-	1217.44	-	8887.31	-	8887.31
Treatment I	11.2	0.46	1217.44	11000.00	13635.33	5060.00	18695.33
Treatment II	16.7	0.65	1217.44	11000.00	20331.25	7150.00	27481.25

In relation to this economic valuation, it is reported during a study conducted in Ethiopia from the evaluation of the total costs and benefits of the net price, an increase in the benefits with the employment of intercalation of these crops of up to 10 % per year for the producers ²². Subsequent studies conducted in the Democratic Republic of the Congo revealed that intercropping systems allow higher net income and are more economically profitable than monoculture ²³.

The intercropping of bean-cassava crops is an agronomic practice that is of great importance since the results achieved in indicators such as the number of tuberous roots per plant and the average mass corroborate an increase in the yields of the main crop, in soils affected by alkalinity; it also allows an increase in the efficiency of land use and the scope of favorable economic results show that it is an alternative to be applied in production systems with similar conditions.

CONCLUSIONS

• The results of this study show that it is possible to take advantage of the potential of cassava cultivation in intercalation systems and that the use of organic matter in combination with mineral fertilizer is an environmentally sustainable and economically viable alternative.

• There is an increase in yields in the cassava crop with the proposed variant, in addition to achieving greater diversification and productive efficiency in the system. In relation to the number of nodules per plant in the bean, it was found that this indicator was higher in the plots where mixed fertilization was used on those that used only organic fertilization.

• With the use of the proposed technological system it is possible to achieve favorable productive results in soils with high alkalinity.

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Received: July 10, 2017; Accepted: January 24, 2019

^*Author for correspondence. [e-mail]