Planting density management and green manure enhance the agro-bioeconomic performance of vegetable intercropping in semi-arid region

ABSTRACT

In semi-arid regions, where water availability and soil fertility limit agricultural production, intercropping vegetables represent a sustainable strategy, increasing resource use efficiency. However, adopting this system requires understanding its interactions and advantages compared to monoculture. In this sense, this study evaluated the agro-bioeconomic efficiency of intercropping beet and coriander with lettuce in succession, as function of equitable amounts of Merremia aegyptia and Calotropis procera, under different population densities of leafy crops (coriander and lettuce), in semi-arid environment. Two field experiments were conducted (2023 and 2024) at the Rafael Fernandes Experimental Farm, Universidade Federal Rural do Semi-Árido, Lagoinha, Mossoró, RN, Brazil, with four amounts of green manures: 25, 45, 65, and 85 t∙ha^-1 in four planting densities of the leafy vegetables: 40, 60, 80, and 100% of the recommended densities in their monocroppings (RDM). The intercropping system outperformed monocropping when 85 t∙ha^-1 of M. aegyptia and C. procera biomass was applied, combined with 100% of the RDM, achieving a land equivalent ratio of 2.36 and a productive efficiency index of 0.98. Beet was the dominant crop (aggressivity of 0.23). The increasing amounts of green manures and planting densities favored the competitiveness of coriander and lettuce. Agrobiological efficiency resulted in a 10 intercropping advantage, which translated into significant economic gains, with a net income of BRL 168,600.97∙ha^-1 and a profit margin of 80.18%. These results demonstrated that proper management of treatment-factors optimizes the agro-bioeconomic efficiency of beet and coriander intercropping with lettuce in succession, highlighting its potential as a sustainable and diversified model.

Key words
Beta vulgaris ; Coriandrum sativum ; Lactuca sativa ; Merremia aegyptia ; Calotropis procera

INTRODUCTION

In the Brazilian semi-arid region, where water and soil limitations restrict productive potential (Mata et al. 2024), intercropping vegetables constitute a sustainable alternative capable of diversifying and optimizing land use and productive efficiency (Glaze-Corcoran et al. 2020, Guerra et al. 2022). This cropping system is based on the complementarity between species that exploit time, space, and resources in an integrated manner, reducing competition and enhancing the efficiency of the system (Maitra et al. 2021, Anchal and Sharma 2025). However, the efficiency of this system depends on the balance between the factors that regulate competition and facilitation between crops (Guerra et al. 2022).

One of the main challenges of vegetable intercropping is optimizing crop mixtures, especially regarding the adjustment of planting densities to maximize intra- and interspecific interactions between crops (Bezerra Neto et al. 2023, Martinez et al. 2024). Planting density is one of the main determinants of these interactions, as it defines the degree of resource utilization and extent of root and canopy overlap of the component crops (Glaze-Corcoran et al. 2020, Zhang et al. 2020), reflecting the combined competitive effects of the individual components (Wang et al. 2020).

The system’s ability to mitigate competition between crops and optimize resource use is influenced by soil fertility. In this context, the use of spontaneous Caatinga species, such as Merremia aegyptia and Calotropis procera, as green manures has proven to be a sustainable strategy for improving soil fertility and biological dynamics, favoring the physiological performance and yield of crops (Bezerra Neto et al. 2024). The association of the use of these green manures with planting density management has enabled the intercropping of tuberous vegetables with leafy or leguminous vegetables, such as radish and coriander (Silva et al. 2024), radish and lettuce (Lino et al. 2023), beet and lettuce (Guerra et al. 2022), beet and arugula (Lino et al. 2021b), radish and cowpea (Azevedo et al. 2021), and beet and cowpea (Azevedo et al. 2025), increasing the productive and monetary efficiency of these systems.

Despite continuous progress in vegetable intercropping in semi-arid regions, most research has focused on combinations involving only two crops or varieties. Furthermore, few studies evaluate the potential of green manures residues for successive crops. The strategic inclusion of other forms of diversification can strengthen ecological processes and make systems more sustainable (Mbanyele et al. 2024). From this perspective, the intercropping of beet and coriander with lettuce in succession exemplifies an efficient approach to temporal and spatial diversification, and the staggered use of resources by each crop can optimize sustainability and profitability per unit area. However, the adoption of this system requires understanding the competitive and complementary interactions between the intercropped crops, highlighting the biological and economic advantages it offers compared to conventional systems (Cecílio Filho et al. 2022, Li et al. 2023).

To quantify the efficiency and viability of intercropping systems, several agro-bioeconomic index have been used, notably the land equivalent ratio (Willey and Osiru 1972), area time equivalent ratio (Pinto et al. 2011), system productivity index (Charnes et al. 1978), crops aggressivity (Cecílio Filho et al. 2022), intercropping advantage (Gebru 2015), and the monetary advantage (Guerra et al. 2022). Economically, these intercropping systems have been evaluated using indicators such as gross income, net income, rate of return, and profit margin (Guerra et al. 2022). When applied appropriately, these indicators provide support for more efficient management strategies.

The aimed of this study was to evaluate the agro-bioeconomic efficiency of beet and coriander intercropping with lettuce in succession, as a function of equitable amounts of M. aegyptia and C. procera biomass, under different planting densities of the leafy crops, in semi-arid environment.

MATERIAL AND METHODS

The experiments were conducted over two growing periods to ensure consistency of results and to take into account the environmental variability of field cultivation: first from August to December 2023 (Cultivation Period 1, C₁) and the second from July to November 2024 (Cultivation Period 2, C₂), at Rafael Fernandes Experimental Farm, linked to the Universidade Federal Rural do Semi-Árido (UFERSA), located in the Lagoinha district, 20 km from the city of Mossoró, RN, Brazil. The region’s climate, according to Köppen-Geiger’s classification, is of type ‘BShw’, characterized as dry and very hot, with two seasons: a dry season that generally occurs from June to January and a rainy season from February to May (Beck et al. 2018). During the experimental periods, the average temperature, relative humidity, solar radiation, and wind speed were 29.2°C, 54.7%, 19.8 MJ∙m^-2, and 5.9 m∙s^-1, respectively, for C₁, and 28.6°C, 54.1%, 18.7 MJ∙m^-2, and 5.4 m∙s^-1, respectively, for C₂. There was no precipitation in any of the cultivation seasons (LABIMC 2025).

The soil in the experimental areas is classified as a Dystrophic Red-Yellow Latosol with a sandy texture (Santos et al. 2018). Before the experiments were set up, individual samples were collected from the 0–20-cm depth layer and homogenized to obtain a composite sample. Subsequently, they were air-dried and sieved through a 2-mm sieve to determine their chemical attributes. The results of these analyses were: hydrogen ion potential (H₂O) = 5.80 and 6.20; cation exchange capacity (mmol_c∙dm^-3) = 27.9 and 58.10; base saturation (mmol_c∙dm^-3) = 14.4 and 38.40; organic matter (g∙dm^-3) = 13.25 and 14.70; phosphorus (mg∙dm^-3) = 6 and 27; potassium (cmol_c∙dm^-3) = 0.18 and 0.33; calcium (cmol_c∙dm^-3) = 0.84 and 0.19; magnesium (cmol_c∙dm^-3) = 0.27 and 0.14; sodium (cmol_c∙dm^-3) = 0.15 and 0.21; copper (mg∙dm^-3) = 0.20 and 4.09; iron (mg∙dm^-3) = 18.70 and 4.90; manganese (mg∙dm^-3) = 4.90 and 11.31; zinc (mg∙dm^-3) = 0.60 and 5.51, for C₁ and C₂, respectively.

The experimental design used was a randomized block design, in a 4 × 4 factorial scheme, with four replications. The first factor consisted of four equitable biomass mixtures of M. aegyptia and C. procera: 25, 45, 65, and 85 t∙ha^-1 on a dry matter basis. The second factor consisted of four planting densities of the leafy greens: 40, 60, 80, and 100% of the recommended density for monocropping (RDM). Lettuce was cultivated in succession to coriander at the same densities of 40, 60, 80, and 100% of the RDM. The planting density of the beet crop was the same, both in the intercropped system and in the monocropping. The recommended planting densities for monocropping of the beet, coriander, and lettuce in the region are 500,000, 1,000,000, and 250,000 plants∙ha^-1, respectively (Paula et al. 2017, Lino et al. 2021a, Ferreira et al. 2022). For coriander intercropping, two plants per planting hole were used. In each block, sole plots of beet, coriander, and lettuce (in succession) were planted, fertilized with equitable amounts of M. aegyptia and C. procera biomass optimized by the investigations by Lino et al. (2021a) and Ferreira et al. (2022), respectively.

Intercropping was established in alternating strips of the component crops, with 50% of the area occupied by beet and 50% by leafy vegetables. In each plot, the alternating strips consisted of four rows, bordered by two rows of coriander or lettuce on one side and two rows of beet on the other, used as borders. The total area of each plot was 2.88 m² (2.40 × 1.20 m), with a harvest area of 1.60 m² (1.60 × 1.00 m). The harvest area consisted of the two central strips of plants, excluding the first and last plants of each row of the strips used as borders. In the sole crop plots, the total area was 1.44 m² (1.20 × 1.20 m) and the harvest area of 0.80 m² (0.80 × 1.00 m) for beet and coriander each, and 0.60 m² (0.80 × 0.80 m) for lettuce (Figs. 1a-1c). The spacings used in the intercropping and single-crop systems are presented in Table 1.

Figure 1
Details of the experimental plots. (a) Beet-coriander intercropping at coriander population densities of 400, 600, 800, and 1,000 thousand plants∙ha^-1 combined with 500 thousand beetroot plants∙ha^-1. (b) Beet-lettuce intercropping at lettuce population densities of 100, 150, 200, and 250 thousand plants∙ha^-1 combined with 500 thousand beetroot plants∙ha^-1. (c) Sole crops of beet, coriander, and lettuce at population densities of 500, 1,000, and 250 thousand plants∙ha^-1, respectively.

Table 1
Description of the population densities and spacings of beet, coriander, and lettuce used in intercropping and monocropping, with their respective spacings.

Planting densities of crops in intercropping
Population densities (thousand plants∙ha-1)				Hole spacings (m)
Beet	Coriander	Lettuce		Beet	Coriander*	Lettuce
500	400	100		0.20 × 0.05	0.20 × 0.120	0.20 × 0.250
500	600	150		0.20 × 0.05	0.20 × 0.085	0.20 × 0.166
500	800	200		0.20 × 0.05	0.20 × 0.062	0.20 × 0.125
500	1,000	250		0.20 × 0.05	0.20 × 0.050	0.20 × 0.100
Population densities of crops in monocropping
Population densities (thousand plants∙ha -1 )				Spacings (m)
				Beet	Coriander	Lettuce
Beet	500			0.20 × 0.10
Coriander	1,000				0.20 × 0.05
Lettuce	250					0.20 × 0.20

• ^*
  Two plants per hole.

Soil preparation for the experiments included mechanical cleaning of the areas using a plow, followed by harrowing and raising the beds with a rotary harrow. Then, the beds were solarized pre-planting for 30 days with transparent plastic (Vulca Brilho Bril Flex 300 microns) to control phytopathogenic soil microorganisms (Amaral and Araujo 2021). After this period, green manures (M. aegyptia and C. procera) were incorporated into the soil in the 0–20-cm layer using hoes. These manures were collected from rural areas in the municipality of Mossoró and crushed in a conventional forage harvester, obtaining fragmented particles of approximately 2 to 3 cm that were dehydrated in the sun until reaching a moisture content of 10%. Chemical analyses of the biomass of these manures were performed, and the results are presented in Table 2.

Table 2
Chemical analysis of macro and micronutrients in the biomass of Merremia aegyptia and Calotropis procera incorporated into the soil in the intercropping system during the cultivation periods of 2023 (C₁) and 2024 (C₂).

Green manures	N	P	K	Ca	Mg		Fe	Zn	Cu	Mn	B	C:N
	g∙kg-1						mg∙kg-1
Cultivation period of 2023 (C 1 )
M. aegyptia	18.98	3.01	37.40	18.55	4.97		438	27.00	6.00	19.00	44.00	20:1
C. procera	15.91	1.22	32.70	10.64	6.41		87	24.00	10.00	77.00	37.00	16:1
Cultvation period of 2024 (C 2 )
M. aegyptia	20.02	3.70	33.62	13.20	3.65		384	21.02	7.76	23.9	25.66	19:1
C. procera	23.10	2.80	37.62	9.71	7.99		195	21.78	7.58	38.98	34.88	15:1

• N: nitrogen; P: PHOSPHORUS; K: POTASSIUM; Ca: CALCIUM; Mg: MAGNESIUM; Fe: IRON; Zn: ZINC; Cu: COPPER; Mn: MANGANESE; B: BORON, C:N ratio.

Fifteen days after the incorporation of the green manures, the vegetables (beet and coriander) were sown. The beet cultivar ‘Early Wonder’ and the coriander cultivar ‘Verdão’ were sown on September 29, 2023 (C₁) and September 5, 2024 (C₂), in holes of approximately 3-cm deep, with three seeds per hole. Thinning of the beet and coriander was carried out 12 and 19 days after sowing (DAS) in C₁ and 14 and 20 DAS in C₂, respectively, leaving one plant per hole for the beet crop and two plants per hole for the coriander crop. Three days after the coriander harvest, the area occupied by the leafy greens was cleared and the ‘Jade’ lettuce seedlings, produced by HortVida Agrícola ME, were transplanted. Transplanting took place on 9/11/2023 (C₁) and 10/10/2024 (C₂) at 22 DAS, in pits 5-cm deep.

The experiments were irrigated using a micro-sprinkler system, with two irrigation shifts (morning and afternoon), according to the water needs of the main crop, providing a water depth of approximately 8 mm∙day^-1. As crop treatments, hilling was carried out in the beet crop at 35 DAS to protect the roots and prevent cracking. Weed control was carried out by manual weeding whenever necessary. For disease control, the beet crop was treated with Trichodermil Super SC®, registered with the Ministério da Agricultura, Pecuária e Abastecimento (MAPA) for use in organic systems, to combat phytopathogenic fungi of the genus Fusarium spp. and Rhizoctonia spp., identified during tuberous thinning. In the leafy crops, no phytosanitary treatment was necessary.

Beet was harvested at 58 and 60 DAS, coriander at 35 and 28 DAS, and lettuce at 29 and 35 days after transplanting, in the first (C₁) and second (C₂) cultivation periods, respectively. The variables analyzed in the intercropping systems included the commercial yield of beet roots, determined from the fresh mass of classified roots (large roots > 7 cm, extra AA roots ≥ 6 to < 7 cm; extra A roots ≥ 5 to < 6 cm; extra > 4 to < 5 cm), obtained in the harvest area and expressed in t∙ha^-1, according to the methodology adopted by Guerra et al. (2022). For coriander and lettuce, the green mass yield was evaluated, based on the fresh mass of leaves collected in the harvest area, also expressed in t∙ha^-1. From these productivities, the system efficiency was estimated using the following specific indices: land equivalent ratio, area time equivalency ratio, corrected monetary advantage, productive efficiency index, actual yield loss, aggressivity, and intercropping advantage.

The land equivalent ratio (LER) was calculated according to the expression proposed by Willey and Osiru (1972) (Eq. 1):

(1) $\mathrm{LER}={\mathrm{Y}}_{\mathrm{bx}}/{\mathrm{Y}}_{\mathrm{bb}}+{\mathrm{Y}}_{\mathrm{cb}}/{\mathrm{Y}}_{\mathrm{cc}}+{\mathrm{Y}}_{\mathrm{lb}}/{\mathrm{Y}}_{\mathrm{ll}}$

Where: Y_bx: the commercial root productivity of beet intercropped with leafy crops (x); Y_bb: the commercial root productivity of beet in monocropping; Y_cb and Y_lb: the green mass yields of coriander and lettuce intercropped with beet, respectively; Y_cc and Y_ll: the green mass yields of coriander and lettuce in monocropping, respectively.

This agronomic index indicates the fraction of area in monocropping that would be necessary to achieve the yields observed in intercropping. LER value greater than 1 indicates an advantage of intercropping, reflecting greater efficiency in land use and better productive performance of the crops. In contrast, a value less than 1 indicates that the association of crops compromises growth and reduces productivity.

The area time equivalency ratio (ATER) was calculated according to Pinto et al. (2011), using Eq. 2:

(2) $\mathrm{ATER}=\left[\right({\mathrm{LER}}_{\mathrm{b}}\mathrm{x}{\mathrm{T}}_{\mathrm{b}})+({\mathrm{LER}}_{\mathrm{c}}\mathrm{x}{\mathrm{T}}_{\mathrm{c}})+({\mathrm{LER}}_{\mathrm{l}}\mathrm{x}{\mathrm{T}}_{\mathrm{l}}\left)\right]/\mathrm{T}$

Where: LER_b: the land equivalent ratio of beet intercropped with leafy crops; LER_c and LER_l: the land equivalent ratios of coriander and lettuce intercropped with beet, respectively. T_b, T_c, and T_l: the times, in days, from planting to harvesting beet, coriander, and lettuce, respectively.

ATER values > 1 indicate a productive advantage of intercropping; ATER = 1 indicates no advantage equivalent to monocropping; and ATER < 1 demonstrates a productive disadvantage of the intercropping system.

Corrected monetary advantage (CMA) was determined according to Guerra et al. (2022), by Eq. 3:

(3) $\mathrm{CMA}=\mathrm{NI}\times (\mathrm{LER}-1/\mathrm{LER})$

Where: net income (NI): expressed in BRL ha^-1, obtained by subtracting the production costs of each treatment from the respective gross income.

Gross income is calculated by multiplying the productivity per hectare of each component crop by the average price paid to the producer in the region, considered at the time of harvest of each crop, being BRL 2.65 per kg for beet, BRL 11 per kg for coriander and BRL 7.55 per kg for lettuce. The production costs of each treatment were estimated based on the input and service coefficients applied per hectare for the implementation of the intercropping system, including expenses with fixed and working capital (depreciation, maintenance and repairs of machinery, implements and improvements), labor, mechanical operations and inputs, adjusted according to the planting density and the green manures amount used in each treatment (Silva et al. 2023).

The productive efficiency index (PEI) for each treatment was determined using the data envelopment analysis model with constant returns to scale, as described by Charnes et al. (1978), since no evidence of significant variation in scale was found between treatments. The general mathematical formulation of the model is described as Eq. 4:

(4) $Max\mathit{\sum }_{\mathit{j}\mathit{=}\mathit{1}}^{\mathit{r}}{u}_{\mathit{j}}{y}_{\mathit{j}\mathit{o}}$

subject to restrictions:

$\sum _{i=1}^s{v}_i{x}_0=1\sum _{j=1}^r{u}_j{x}_{jk}-\sum _{i=1}^s{v}_i{w}_{ik}\le 0,k=1\dots n{u}_j{v}_i\ge 0,i=1\dots s,j=1\dots r,$

Where: xik: the value of input i (i = 1 ... s) for treatment k (k = 1 ... n); yjk: the value of output j (j = 1 ... r) for treatment k; vi and uj: the weights assigned to the inputs and outputs, respectively, with 0 being the treatment under evaluation.

The 16 treatments (4 densities × 4 quantities of green manures) were considered as evaluation units. The commercial productivity of beet and the green mass yields of leafy crops (coriander and lettuce) were used as outputs, while the profitability index was adopted as input. It was assumed that all units operate with a unitary resource, since variations in use are already reflected in the outputs. The model adopted is equivalent to an additive multicriteria approach, in which the weights of each variable are determined by the units themselves, without external influence (Lima et al. 2014).

The actual yield loss (AYL) was determined following Banik’s method (1996), using the following expression (Eq. 5):

(5) $\begin{array}{l}\mathrm{AYL}={\mathrm{AYL}}_{\mathrm{b}}+{\mathrm{AYL}}_{\mathrm{c}}+{\mathrm{AYL}}_1\\ {\mathrm{AYL}}_{\mathrm{b}}=[\{({\mathrm{Y}}_{\mathrm{bx}}/{\mathrm{Z}}_{\mathrm{bx}})/({\mathrm{Y}}_{\mathrm{bb}}/{\mathrm{Z}}_{\mathrm{bb}}\}-1];{\mathrm{AYL}}_{\mathrm{c}}=[\{({\mathrm{Y}}_{\mathrm{cb}}/{\mathrm{Z}}_{\mathrm{cb}})/({\mathrm{Y}}_{\mathrm{cc}}/{\mathrm{Z}}_{\mathrm{cc}}\}-1];\\ {\mathrm{AYL}}_1=\left[\right\{(\mathrm{Ylb}/\mathrm{Zlb})/(\mathrm{Yll}/\mathrm{Zll})\}-1]\end{array}$

Where: AYL_b, AYL_c, and AYL_l: the actual yield losses of beet, coriander, and lettuce, respectively; Y_bx: the commercial root productivity of beet intercropped with leafy crops; Z_bx: the planting ratio of beet in intercropping with leafy crops; Y_bb: the commercial root productivity of beet in monocropping; Z_bb: the planting ratio of beet in monocropping; Y_cb and Y_ab: the green mass yields of coriander and lettuce intercropped with beet, respectively; Z_cb and Z_ab: the planting ratios of coriander and lettuce intercropped with beet, respectively; Y_cc and Y_aa: the green mass yields of coriander and lettuce in monocropping, respectively; Z_ca and Z_aa: the planting ratios of coriander and lettuce in monocropping, respectively.

AYL values > 0 indicate that intercropping has a productive advantage compared to monocropping, while AYL values < 0 indicate that the intercropping system has a disadvantage.

The aggressivity (A) is an index that quantifies the relative increase in the production of one component crop compared to another in an intercropping, indicating the dominance of one over the other. The calculation of this index was based on the expressions proposed by McGilchrist and Trenbath (1971), with adaptations, considering that throughout the beet cycle, two crops were cultivated: coriander and lettuce. As these leafy crops occupied the same space successively, A was determined from the sum of their productivities (Eqs. 6 and 7):

(Eq. 6) ${\mathrm{A}}_{\mathrm{xb}}=[({\mathrm{Y}}_{\mathrm{xb}}/{\mathrm{Y}}_{\mathrm{xx}}{\mathrm{xZ}}_{\mathrm{xb}})-({\mathrm{Y}}_{\mathrm{bx}}/{\mathrm{Y}}_{\mathrm{bb}}{\mathrm{xZ}}_{\mathrm{bx}})]$

(Eq. 7) ${\mathrm{A}}_{\mathrm{bx}}=[({\mathrm{Y}}_{\mathrm{bf}}/{\mathrm{Y}}_{\mathrm{bb}}{\mathrm{xZ}}_{\mathrm{bb}})-({\mathrm{Y}}_{\mathrm{xb}}/{\mathrm{Y}}_{\mathrm{xx}}{\mathrm{xZ}}_{\mathrm{xx}})]$

Where: Y_xb and Y_bx: the productivities of leafy crops (x) intercropped with beet and of beet intercropped with leafy crops;

Y_xx and Y_bb: the productivities of leafy crops and beet in monocropping, respectively; Z_xb: the planting ratio of leafy crops intercropped with beet; Z_bx: the planting ratio of beet intercropped with leafy crops.

If A equals 0, the component crops of the intercropping system exhibit equivalent competitiveness. When A has a positive sign for a crop, it is considered dominant, while a crop with a negative sign is dominated.

The intercropping advantage (IA) was calculated according to Gebru (2015), using Eq. 8:

(Eq. 8) $\mathrm{IA}={\mathrm{IA}}_{\mathrm{b}}+{\mathrm{IA}}_{\mathrm{c}}+{\mathrm{IA}}_1$

Where: IA_b: the partial advantage of intercropping beet with leafy crops; IA_c and IA_l: the partial advantages of intercropping coriander with beet and lettuce with beet, respectively, being: IA_b = AYL_b × PR_b; IA_c = AYL_c × PR_c and IA_l = AYL_l × PR_l, where, AYL_b, AYL_c and AYL_l correspond to the AYL of the respective crops (beet, coriander and lettuce, respectively), while PR_b, PR_c, and PR_l indicate the prices of beet, coriander and lettuce, respectively, considering the market values mentioned above (BRL∙kg^-1).

The assessed economic indicators were: gross income, expressed in BRL∙ha^-1; net income, also expressed in BRL∙ha^-1 (described previously); rate of return, calculated by the ratio between gross income and production cost of each treatment, indicating how many reals are obtained for each real invested; and profit margin, determined by the relationship between net income and gross income, expressed as a percentage (Guerra et al. 2022).

Univariate analysis of variance, in a randomized block design with a factorial arrangement, was employed to evaluate agronomic index and economic indicators, using SAS software (SAS 2015). A joint analysis was performed between the cultivation periods, due to the homogeneity of variances (mean square quotient < 7), and an average between these periods was calculated for each treatment (Pimentel-Gomes 2023). Next, polynomial regression analysis was performed for each index and indicator, fitting a response surface as a function of the equitable amounts of M. aegyptia and C. procera biomass and coriander or lettuce population densities for each variable, using the Table Curve 3D software (Systat 2021). The regression models were selected considering biological logic of the variable, significance of the regression mean square, high value of the coefficient of determination (R²), significance of the regression equation parameters, and maximization of the variable (Ferreira et al. 2022).

Results and discussion

Agronomic index

Analysis of variance showed a significant interaction (p < 0.01) between the biomass amounts of M. aegyptia and C. procera (A) and the different population densities of leafy crops (D) for the agronomic index: LER, ATER, CMA, and PEI (Table 3).

Table 3
F values for land equivalent ratio (LER), area time equivalency ratio (ATER), corrected monetary advantage (CMA), and productive efficiency index (PEI) of beet intercropping with the leafy crops (coriander and lettuce) as a function of the biomass amounts of Merremia aegyptia and Calotropis procera and population densities of the leafy crops.

Sources of variation	DF	LER	ATER	CMA	PEI
Blocks	3	1.28ns	1.75ns	1.64ns	1.68ns
Amounts of M. aegyptia and C. procera biomass (A)	3	2,216.55*	3,383.68*	2,104.06*	91.32*
Population densities of lettuce (D)	3	637.71*	738.78*	628.05*	253.63*
A × D	9	26.15*	24.74*	80.86*	4.06*
Regression		129.76*	187.96*	40.16*	110.14*
Error		0.0075	0.0025	1.42.104	4.56.10-5
CV (%)		2.21	1.71	6.70	0.81

• DF: degree of freedom; CV: coefficient of variation;
• ^*
  p < 0.01;
• ^ns
  p > 0.05.

Response surface models were fitted (p < 0.01; R² > 0.91) for these agronomic index as a function of the biomass amounts of the green manures and leafy crops population densities, obtaining maximum efficiencies of 2.36; 1.72; BRL 311,178.45∙ha^-1 and 0.98 for LER, ATER, CMA, and PEI, respectively, with the application of 85 t∙ha^-1 of M. aegyptia and C. procera biomass associated with a population density of 100% of that RDM, except for PEI, to which maximum efficiency was achieved with 86.80% of the recommended density (Figs. 2a–2e).

Figure 2
Agronomic index. (a) Land equivalent ratio, (b) area time equivalency ratio, (c) corrected monetary advantage and (d) productive efficiency index of beet intercropping with leafy vegetables (coriander and lettuce) as a function of the biomass amounts of Merremia aegyptia and Calotropis procera and the population densities of the leafy crops.

These results indicated that the greater supply of nutrients, resulting from the higher quantity of the green manures, favored increased productivity and mitigated the effects of competition, ensuring more balanced growth of the intercropped crops. In addition to providing nutrients (N, P, K, Ca, Mg, B, and Fe; Table 2) for photosynthesis and plant metabolism (Taiz et al. 2024), the species used also act on the physical and biological attributes of the soil, improving its structure, water retention capacity, and microbial activity. The addition of organic matter favors the formation and stabilization of aggregates through the action of humic substances and microbial exudates, resulting in better soil structure and greater porosity. This process increases water retention capacity and improves aeration. In addition, the use of organic products acts as a source of carbon and energy for the soil microbiota, stimulating microbial activity and enhancing nutrient cycling processes (Haruna et al. 2025, Xing et al. 2025). This condition ensured the permanence of a greater number of plants (100% of the leafy green manures) in the area and favored more efficient exploitation of space and resources by the leafy vegetables, without intensifying competition between the crops established in the system.

Additionally, the results obtained demonstrated the complementarity between the crops. As highlighted by Githui et al. (2023), complementarity occurs when the intercropped crops exploit resources at different times or spaces, reducing direct competition. This dynamic is determined by the morphological and physiological characteristics of the crops, conditioning the distribution of resources and agricultural yield. Beet has an upright growth habit, a longer cycle, and a deep taproot, exploring the lower layers of the soil. Coriander and lettuce, on the other hand, are short-cycle crops with leaf architecture that occupies the middle canopy of the system, and shallow, branched root systems, mainly occupying the first 0.25 m of soil (Filgueira 2012). These differences reduce overlap in the use of light and nutrients, favoring complementarity between the crops. Furthermore, because they are cultivated in succession, the leafy greens utilize different niches in time and space, allowing the development of two crops throughout the beet cycle. By maximizing resource use and increasing functional diversity, intercropping presents itself as an effective strategy for the sustainable intensification of agricultural production (Li et al. 2023).

This multifaceted functional balance explains the observed LER and ATER values, which were reflected in the increased CMA and PEI. LER and ATER values greater than 1 indicate greater efficiency in land use and cultivation time when compared to monocropping (Anchal and Sharma 2025). Meanwhile, the higher CMA and PEI confirm the productive and economic viability of the intercropping system, demonstrating its capacity to convert the integrated use of land and inputs into greater economic return (Silva et al. 2024). Thus, it can be stated that the established intercropping system is characterized as an efficient and advantageous system compared to monocropping, regarding the exploitation of the area and resources, and its agro-monetary viability.

Similar results were reported by Lino et al. (2021a) under similar experimental conditions. In the intercropping of beet and arugula, the authors obtained a LER of 1.87 and a PEI of 0.98 using 65 t∙ha^-1 of M. aegyptia and C. procera combined with 100% of the arugula population density. In the study by Guerra et al. (2022), the intercropping of beet with lettuce in bicultivation, with 65 t∙ha^-1 of biomass of M. aegyptia and C. procera and a density of 300,000 lettuce plants∙ha^-1, resulted in a LER of 2.59; ATER of 1.39; PEI of 0.97; and CMA of BRL 94,742.89∙ha^-1. This performance was associated with the synchronization between the mineralization of green manure biomass and the nutritional demands of the crops, as well as the complementarity in the use of resources, contributing to greater system efficiency. These results corroborate the present study, in which the highest dose of green manure (85 t∙ha^-1), although higher than previously reported, favored productive efficiency in successive crops, highlighting the potential of these species as strategic sources of organic fertilization in sustainable horticultural systems in the semi-arid region.

Biological index

The results of the analyses of variance of the biological index of the intercropping system are presented in Table 4. Significant interactions (p < 0.01) were observed between the factors’ equitable amounts of M. aegyptia and C. procera biomass and population densities of leafy vegetables (A × D) for A of leafy vegetable over beet (A_xb), A of beet over leafy vegetables (A_bx), AYL and IA.

Table 4
F values for the aggressivity of leafy vegetables over beet (A_xb), aggressivity of beet over leafy vegetables (A_bx), actual yield loss (AYL), and intercropping advantage (IA) of beet with leafy vegetables (coriander and lettuce) as a function of the biomass amounts of Merremia aegyptia and Calotropis procera and the population densities of the leafy crops.

Sources of variation	DF	Axb	Abx	AYL	IA
Blocks	3	0.39ns	0.39ns	1.28ns	0.89ns
Amounts of M. aegyptia and C. procera biomass (A)	3	48.55*	48.55*	2,273.79*	1,140.30*
Population densities of lettuce (D)	3	192.05*	192.05*	653.78*	531.96*
A × D	9	31.04*	31.04*	27.17*	31.21*
Regression		57.02*	57.02*	130.99*	62.75*
Error		0.0001	0.0001	0.0299	3.070
CV (%)		-7.50	7.50	21.14	-153.24

• DF: degree of freedom; CV: coefficient of variation;
• ^*
  p < 0.01;
• ^ns
  p > 0.05.

Response surface models (p < 0.01; R² > 0.94) were fitted to describe the behavior of the variables as a function of the treatment-factors studied. Maximum values of -0.06 were obtained for A_xb, 0.23 for A_bx, 1.72 for AYL, and 10 for IA, in the combinations of equitable amounts of green manures biomass and leafy crops population densities of 85 and 100; 71.09 and 43.77; 85 and 100; 85 t∙ha^-1 and 100% of RDM (Figs. 3a–3d).

Figure 3
Biological index. (a) Aggressivity of the leafy vegetables over beet, (b) aggressivity of beet over leafy vegetables, (c) actual yield loss, and (d) intercropping advantage of beet with leafy crops (coriander and lettuce) as a function of the biomass amounts of Merremia aegyptia and Calotropis procera and the population densities of the leafy crops.

The overcoming index explains the dynamics of competition and complementarity between cultivated species, expressing the intensity of intra- and interspecific relationships in the intercropping (Guerra et al. 2022). Based on the observed A values, beet exerted dominance over the leafy vegetable (coriander and lettuce), reflecting different strategies for utilizing environmental resources, in which the leafy crops showed less competitive capacity. This result aligns with the principle of asymmetric resource partitioning in intercropping (Vandermeer 1989), according to which the species with greater vigor or size, in this case beet, tends to use available resources more intensively, reducing the supply for the associated crop. Furthermore, the interaction between species alters the dynamics of competition within each crop itself (Zhang et al. 2020), increasing competitive effects.

However, increasing the amounts of green manures and the population densities of leafy vegetables favored an increase in A_xb and a reduction in A_bx (Figs. 3a–3b), indicating a competitive balance between the intercropped crops, a behavior similar to that observed by Guerra et al. (2022) in the beet and lettuce intercropping. The reduction of mutual competition favors facilitation, allowing crops to exploit the environment in a complementary and cooperative manner (Vandermeer 1989, Gitari et al. 2020). Silva et al. (2024) report that, regardless of plant density, coriander demonstrates lower interspecific competitiveness than radish. The authors observed that the competitive advantage of radish over coriander increased as the evaluated factors increased, reaching an A of 1.03 in the combination of 100% of the RDM of coriander with 65 t∙ha^-1 of green manures (M. aegyptia and C. procera).

The agrobiological efficiency of the established system (beet and coriander with lettuce in succession) was evidenced by the results of AYL (1.72) and IA (10), indicating superiority in comparison to the monocropping of the system’s crops. AYL values > 0 indicate productive efficiency, suggesting compatibility between intercropped species. Complementarily, the advantage occurs when the combined performance of the crops surpasses what would be obtained by each species in monocropping (Silva et al. 2020). The authors associated this result with intrinsic differences between crops regarding their growth capacity and exploitation of environmental resources, highlighting that the competitive ability of species is determined by the interaction between their morphophysiological characteristics and the conditions imposed by the cultivation system.

Thus, the superiority of the intercropping resulted from the complementarity between beet and leafy vegetables, which exploit the same resources in different ways due to their different ecological niches, favoring beneficial intra- and interspecific interactions and increasing the efficiency of the system (Bezerra Neto et al. 2023). The appropriate arrangement of crops and spacing tends to intensify these facilitating interactions, contributing to increased productivity and stability of the agroecosystem (Yu et al. 2025). Furthermore, the increased productive diversification provided by the successive cultivation of lettuce favored the use of the green manures residues, expanding the overall efficiency of the system.

When investigating the interactions in the radish-lettuce intercropping system, Lino et al. (2023) observed that increasing the amounts of M. aegyptia and C. procera and population densities increased the AYL and IA, reaching maximum values of 2.40 and 8.03, respectively, with 65 t∙ha^-1 of green manures and 300,000 lettuce plants∙ha^-1. Similar results were described by Sá et al. (2021), who obtained a AYL of 1.31 and an intercropping advantage of 5.16 in radish-arugula cultivation, combining 65 t∙ha^-1 of M. aegyptia and C. procera with 100% of the arugula’s RDM. According to the authors, these results stemmed from the interaction between the biomass input from green manures and the increased crop density, which favored the availability and utilization of environmental resources, intensifying functional complementarity and promoting a more efficient partitioning of resources among the species.

The maximum efficiency observed in A, AYL, IA in this study reflects the higher degree of competitiveness and complementarity between the species. The complementary effect of the distinct competitive capacities of the intercropped crops manifested itself in the joint and non-competitive use of available resources both above and below ground, increasing the continuous efficiency of the system (Wang et al. 2020, Anchal and Sharma 2025). This efficiency can also be attributed to the intensification of nutrient absorption with the increase in the amounts of M. aegyptia and C. procera. The improvement in the nutritional and physiological status of the plants allowed for superior productive performance compared to monocropping, highlighting the efficiency of intercropping under conditions of higher green biomass supply. The increased nutrient availability, the synchrony between decomposition, given by the C:N ratio, and the nutritional demand of the crops (Bezerra Neto et al. 2024) probably reduced competition and favored the development of leafy greens, indicating a compensatory effect of green manures on the physiological dynamics of intercropped crops, even under conditions of high population density.

Economic indicators

Table 5 presents the results of the analysis of variance for the economic indicators: gross income, net income, rate of return, and profit margin. There was a significant interaction (p < 0.01) between the biomass amounts of M. aegyptia and C. procera (A) and the different population densities of leafy crops (D) for all indicators evaluated. These results showed that the simultaneous adjustment of these factors is crucial to maximize the profitability of the system.

Table 5
F values for gross income (GI), net income (NI), rate of return (RR) and profit margin (PM) of beet intercropping with leafy vegetables (coriander and lettuce) as a function of the biomass amounts of Merremia aegyptia and Calotropis procera and the population densities of the leafy crops.

Sources of variation	DF	GI	NI	RR	PM
Blocks	3	2.55ns	2.55ns	2.90ns	3.11ns
Amounts of M. aegyptia and C. procera biomass (A)	3	3,966.89*	2,668.10*	157.26*	151.50*
Population densities of lettuce (D)	3	953.70*	868.22*	658.51*	882.75*
A × D	9	46.02*	46.02*	18.75*	13.95*
Regression		139.13*	100.14*	49.70*	68.97*
Error		5911	5901	0.0239	0.4688
CV (%)		1.77	2.26	1.68	0.46

• DF: degree of freedom; CV: coefficient of variation;
• ^*
  p < 0.01;
• ^ns
  p > 0.05.

A response surface was fitted (p < 0.05; R² > 0.93) for all these economic indicators as a function of the treatment-factors. The maximum efficiency achieved was BRL 209,855.64 and BRL 168,600.97∙ha^-1 for gross income and net income, respectively, of BRL 5.06 for each real invested for rate of return and 80.18% for profit margin, respectively, achieved with the application of 85 t∙ha^-1 of M. aegyptia and C. procera biomass combined with 100% of the population RDM (Figs. 4a–4d). The results indicated that the biological and productive efficiency observed in the intercropping system translated into significant economic gains, a consequence of the balance between the factors studied, notably evidenced by the net income value. This indicator is a representative metric of the overall efficiency of the system, as it expresses the real gain obtained after deducting production costs (Bezerra Neto et al. 2019), confirming that the adoption of intercropping beet and coriander with lettuce in succession, in addition to being biologically efficient, is also economically viable and sustainable. Furthermore, the rate of return and the profit margin reinforce the advantage of the intercropping system—these indicators depend on production costs and the seasonality of vegetable market prices.

Figure 4
Economic indicators. (a) Gross income, (b) net income, (c) rate of return, and (d) profit margin of intercropping beet with leafy vegetables (coriander and lettuce) as a function of the biomass amounts of Merremia aegyptia and Calotropis procera and the population densities of the leafy crops.

When evaluating the advantages of intercropping in terms of yield, profit, and environmental impacts, it is essential to also consider the costs involved in its implementation (Weih et al. 2022). Thus, the high values observed in gross income, net income, rate of return, and profit margin demonstrate that the use of green manures with spontaneous species from the Caatinga, available locally, reduces dependence on external inputs and, consequently, production costs, ensuring a financial return compatible with the capital invested. This practice favors insertion into markets that value safe and agrochemical-free products, which present greater added value and economic return to the producer (Silva et al. 2023). Furthermore, the shared use of inputs for different crops reduces costs compared to the isolated production of each crop (Weih et al. 2022). The system implemented with crop succession increases functional diversity, reducing the vulnerability of productivity and income to environmental changes and market fluctuations (Martinez et al. 2024).

Guerra et al. (2022) obtained high economic returns in beet and lettuce intercropping, in which the application of 65 t∙ha^-1 of green manures biomass and 300,000 lettuce plants∙ha^-1 resulted in a gross income and net income of BRL 94,742.89 and BRL 59,121.45∙ha^-1, respectively, and a rate of return of BRL 2.75 for each real invested. Similarly, the intercropping of beet and arugula resulted in BRL 85,827.79 and BRL 65,425.01∙ha^-1; BRL 4.24 for each real invested and 77.02%, respectively, for gross income, net income, rate of return, and profit margin in the amount of 65 t∙ha^-1 of M. aegyptia and C. procera associated with 100% of the arugula RDM (Lino et al. 2021b).

As observed in the present study, these economic results were associated by the authors with the greater productive efficiency of the intercropping systems, resulting from the more efficient use of the area, the complementarity between crops, and the use of green manures as a low-cost source of nutrients, reducing costs and increasing the economic return of the system.

CONCLUSION

The intercropping of beet with coriander and lettuce in succession, fertilized with 85 t∙ha^-1 of biomass of M. aegyptia and C. procera and combined with 100% of the recommended population density for leafy vegetables, showed high biological, productive and economic efficiency, establishing itself as a sustainable agricultural system for the semi-arid region.

ACKNOWLEDGMENTS

The authors thank the Graduate Program in Crop Science at the Universidade Federal Rural do Semi-Árido (UFERSA) for supporting the researchers and the Study and Research Group on Cultural and Post-Harvest Practices for the Semiarid Region of the Universidade Federal Rural do Semi-Árido, which develops technologies for the cultivation of vegetables in family farming.

How to cite:

Silva, J. P. P., Bezerra Neto, F., Lima, J. S. S., Santos, E. C., Ferreira, D. P., Dantas, D. S., Azevedo, M. C., Pessoa, L. N., Coura, L. K. S. and Rodrigues, G. S. O. (2026). Planting density management and green manure enhance the agro-bioeconomic performance of vegetable intercropping in semi-arid region. Bragantia, 85, e20250258. https://doi.org/10.1590/1678-4499.20250258

FUNDING

Conselho Nacional de Desenvolvimento Científico e Tecnológico

Grant No.: 305,597/2023-0

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Grant No.: 88887823845/2023-00

DECLARATION OF USE OF ARTIFICIAL INTELLIGENCE TOOLS

Artificial intelligence tools were used exclusively for language review and grammatical correction; they were not used to generate scientific content, data, results, or conclusions. The authors are responsible for the content of the manuscript.

DATA AVAILABILITY STATEMENT

Additional data generated during the study are available from the corresponding author upon reasonable request.

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*

Corresponding author: [e-mail]

Section Editor:

Gabriel Constantino Blain https://orcid.org/0000-0001-8832-7734

CONFLICT OF INTEREST

Nothing to declare.

Publication Dates

• Publication in this collection
  12 Oct 2026
• Date of issue
  2026

History

• Received
  24 Nov 2025
• Accepted
  10 Aug 2026