Effect of spatial arrangement of faba bean variety intercropping with maize on yield and yield components of the crops

Abstract

Efficient maize-faba bean intercropping system for optimum grain yield and productivity is needed in order to use the limited land and to enhance food security of the smallholder farmers. A field experiment was conducted at Haramaya, eastern Ethiopia during the 2018 and 2019 main cropping seasons to determine the effect of variety and spatial arrangement on a maize-faba bean intercropping system on yield components and yields of the component crops and the productivity of the system. The treatments consisted of the recommended 100% plant populations of maize (Baate) variety intercropped with 50% of the recommended density of four faba bean varieties (Yeferenji Baqela, Yehabesha Baqela, Batte and Gachena). The component crops were sown at three levels of spatial arrangements (1:1 1:2 and 2:2), whereas sole maize and the four faba beans were sole-planted. The treatments were laid out as a randomized complete block design with three replications in factorial approach. The results revealed that cropping season affected all the maize variables-cropped. Sole-cropped maize gave the higher grain yield (5.91 t ha⁻¹) compared to intercropping system. Maize intercropped with 2:2 spatial arrangements gave the highest grain yield (5.37 t ha⁻¹). Sole-cropped faba bean gave higher seed yield (2.04 t ha⁻¹) than intercropped faba bean. The 1:1 spatial arrangement was superior in number of pods per plant (5.27), aboveground dry biomass (3.81 t ha⁻¹), and seed yield (0.86 t ha⁻¹) to the other spatial arrangements. Variety Gachena was superior to the other varieties in number of pods per plant (5.49), above ground dry biomass (3.77 t ha⁻¹), seed yield (0.88 t ha⁻¹). Land equivalent ratio (LER) was unaffected by variety differences; however, a 26.8% yield advantage was achieved at 1:1 spatial arrangement in which the highest LER (1.268) value was obtained. The highest gross monetary value (GMV) (96,308 ETB ha⁻¹), maize equivalent yield (MEY) (6420.53 kg ha⁻¹) and monetary advantage index (MAI) (17,506) was obtained from Gachena variety. A 1:1 spatial arrangement gave the maximum GMV (94,162 ETB ha⁻¹), MEY (6277.49 kg ha⁻¹) and MAI (18,761). Therefore, it is concluded that intercropping of Gachena variety in a 1:1 spatial arrangement with maize resulted in the highest productivity and economic advantage for the farmers of the study area.

1. Introduction

Agriculture in the next decade will have to produce more food from less area of land through more efficient use of natural resources with minimal impact on the environment in order to meet the growing population demands [1]. However, crop production by smallholder farmers in Ethiopia are largely depends on rainfall. Rainfall in most of sub-Saharan Africa is characterized by poor distribution, frequent dry spells, flooding and drought episodes which increase the risk of dry land farming [2]. In addition, poor soil fertility has exacerbated food security in this sector [3]. Some years back farmers were practicing crop rotation, fallowing and other sustainable cropping systems. This effort, which helped farmers to maintain their soil fertility, is currently diminished as a result of the increasing population and the shrinkage of landholding. Nowadays, the most dominant farming system or practice is monocropping system, which in turn contributes to decrease soil fertility. In order to mitigate the risk associated with such constraints and ensure continuous food supply, smallholder farmers could diversify crop production strategies through legume-cereal intercropping [4]. Intercropping increased biodiversity and efficient use of environmental resources [5].

Intercropping is a farming practice involving two or more crop species, or genotypes, growing together and coexisting for a time. Intercropping a legume and cereal are most common among farmers in the semi-arid tropics and is important in many subsistence or low-input/resource-limited agricultural systems compared with corresponding sole crops. Yield advantages have been recorded in many legume-cereal intercropping systems, including soybean-sorghum [6]), cowpea-maize [7], faba bean-wheat [8] and vetch-oat [9]. The reason of yield advantage of intercropping are mainly that environmental resources such as water, light and nutrients can be utilized more efficiently in intercropping than in the respective sole cropping systems [10]. Owing to its numerous uses, great nutritional quality and ability to grow over a broad range of climatic and soil conditions, faba bean is appropriate for sustainable agriculture in many marginal areas [11]. Integrating faba bean in various cropping system such as intercropping or crop rotation improves natural soil fertility and reduce the consumption of commercial N fertilizer. Faba bean in smallholders’ agriculture is an important component of crop production as an alternative source of protein, starch and minerals; cash income and plays a significant role in improving the productivity of the soil in the cereal-based intercropping and rotations where it serves as a break crop [12]. At present time, most faba bean crops in the industrialized countries are sole cropped, but legume and cereal intercrops in spatial arrangement can provide robust and resilient crop stands [13].

Spatial arrangement is one of the methods of intercropping when two or more crops are planted in separate rows or alternating rows on the same piece of land. Spatial arrangement of intercrops is an important crop management practice that can improve radiation interception through more complete ground cover [14]. It offers one of the best ways of increasing production per unit area by growing two crops of dissimilar growth habit in the same field with little intercrop competition. In intercropping systems, competition is an important factor that needs to be considered to determine the compatibility of the component crops. The extent of competition-induced yield loss in intercropping is likely to depend on the spatial arrangement of component crops. The spatial arrangements of component crops are important to determine the degree of inter and intra species competition [15].

An ideal spatial pattern should be used with minimum influence on companion crop yield. Common intercrop spatial patterns used worldwide [16] are intra-row (within the same row), inter-row (alternating rows) and random (mixed). Planting pattern affect interaction between intercrop companion crops, their use of environmental resources and thus influence the outcome of intercrop compared to sole cropping system. Spatial arrangements of component crops improve the amount of light transmitted to the lower legume. Such arrangements can enhance legume yields and efficiency in cereal/legume intercropping [17]. Changing the planting pattern of the main and component crops is important agronomic approach in intercropping systems. Spatial arrangements of plant have important effect of competition between component crops and affect their productivity [18]. Competition for light, water, nutrients, and allelopathic effects may reduce yields in intercropping [19]. However, selection of appropriate crops, planting rates, and changes in the spatial arrangement of the crops can reduce competition [20]. In intensive intercropping systems like additive series, where the base crop population is maintained at 100% and intercrops are introduced through replacement series of crop geometry, there is likelihood of some influence of base crops on the performance of intercrops. This affects the normal growth and physiological processes of the intercrops leading to below par performance [21].

Even though there have long standing traditional knowledge of growing multiple crops in intercropping systems, smallholder farmers do not consider the better compatible varieties of faba bean to be used in maize and their spatial arrangement required in intercropping system. Studying the productivity of intercropped maize-faba bean as component crops and their general performance are imperative using a number of indices such as land equivalent ratio and crop equivalent yield [22,23]. The effects of different spatial arrangements of component crops of an additive population of faba bean in maize as intercrop on the growth and productivity of maize-faba bean intercropping systems has not been studied under the eastern Ethiopian environment conditions. Therefore, the objective of this study was to determine the effect of variety and spatial arrangement of faba bean in intercropping with maize on yield and yields components of the component crops and the productivity of the system.

2. Materials and methods

2.1. Description of the study area

The study was conducted at Haramaya district in East Hararghe Zone, Ethiopia in June–December 2018 and May to December 2019 main cropping seasons. The research site is located at a latitude of 9°24′58″ N, a longitude of 42°02′18″ E and an altitude of 2005 m above sea level. The total rainfall in 2018 and 2019 cropping seasons from the month of May to December was 642.6 mm and 911.91 mm, respectively, with mean temperature of 17.63 °C and 19.11 °C (Fig. 1). The soil of the experimental site is classified as vertisol with sandy clay loam in texture and the site was planted with potato in the previous cropping season. The major crops grown in eastern Hararghe Zone includes sorghum, maize, khat, common bean, faba bean, field pea, sweet potato, potato, cabbage, onion, tomato, mango, banana, and papaya.

Fig. 1.

Monthly total rainfall (mm) and monthly mean average (T_avg) temperatures (^oC) of the study site during the cropping seasons. Source: National Meteorological Agency Jigjiga Branch Office.

2.2. Pre-planting soil data collection and analysis

Soil samples were taken to the depth of 0–30 cm randomly from nine spots in an ‘x' pattern before planting using auger and one composite sample was prepared. The composite samples were air-died, foreign materials were removed, grinded using mortar and plate, sieved through a 2 mm sieve, stored in a clean plastic container and labelled. About 1 kg of the sieved samples were submitted to laboratory to be analyzed for selected chemical and physical soil properties such as soil pH, available P, Total N, OM, and soil texture of the experimental soil. The soil of the experimental site was analyzed as shown in Table 1 below.

Table 1.

Selected soil physical and chemical properties in Haramaya district of eastern Ethiopia at the study site in the 2018 and 2019 growing seasons before planting the crops.

Soil physical and chemical properties	Values		Rating	References
	2018	2019
pH (1:2.5H2O)	8.15	7.96	Moderately alkaline	Murphy [24]
Organic carbon (%)	1.175	1.237	Low	Berhanu [25] cited by Tekalign et al. [26]
Total nitrogen (%)	0.142	0.148	Medium	Berhanu [25] cited by Tekalign et al. [26]
Available phosphorus (mg kg soil−1)	12.68	14.22	Medium	Cottenie [27]
CEC (cmol(+) kg soil−1)	34.42	28.56	High	Landon [28]
Physical properties
Sand (%)	44	51
Silt (%)	21	24
Clay (%)	35	25
Textural class	Sandy clay loam	Sandy clay loam

CEC = cation exchange capacity.

2.3. Experimental varieties

One maize improved variety called Baate with highly performing in the study area's condition and three farmers' faba bean varieties (Yeferenji Baqela, Yehabesha Baqela, and Batte) and improved variety Gachena were used in this experiment. Gachena variety was an improved variety released by Haramaya University in 2008 [29].

2.4. Treatments, experimental design and procedures

The treatments consisted of factorial combinations of four varieties of faba bean (Yeferenji Baqela, Yehabesha Baqela, Batte, and Gachena) and three spatial arrangements (1:1, 1:2 and 2:2 spatial arrangement of maize: faba bean) in the intercropping with maize, and the respective sole faba bean varieties and sole maize. The treatments were laid out in randomized complete block design with three replications in factorial arrangement. The size of individual plot of the experimental area was 3.75 m × 3.0 m = 11.25 m². The intra and inter-row spacing between faba bean sole cropping was 0.1 m × 0.4 m, respectively. Here, the total number of seeds sown for intercropping was at the ratio of 100:50% of the recommended rate of maize to faba bean (i.e. 53,333 plants ha⁻¹: 125,000 plants ha⁻¹) and 100% recommended rate of both maize (53,333 plants ha⁻¹) and faba bean (250,000 plants ha⁻¹) varieties. The maize crop was used as principal crop at each intercropping and spaced at a distance of 0.25 m × 0.75 m for both 1:1 spatial arrangement intercropping and maize sole cropping system. The space between plots and blocks was 1.0 m and 1.0 m, respectively. The total experimental land area lay on 15.25 m × 69.0 m = 1052.25 m². A net plot from which data collection and measuring made for analysis was from 2.625 m × 2.5 m = 6.56 m² for both sole and intercropped treatments.

In 1:1 row arrangement, there was 5 rows of maize with the total plant per plot were 60 plants and four rows of faba bean with the total of 140 plants per plot. One row of faba bean was sown after every one row of maize. In 1:2 row arrangements, there were 5 rows of maize having 12 plants per row and with a total of 60 plants per plot. The faba bean also arranged with 8 rows having 18 plants per row and with a total of 140 plants per plot. Two rows of faba bean were planted in an alternative to one rows of maize with the initial row from the side of the plot starts with maize cropping. In 2:2 row arrangements, there were 6 rows of maize with the total plant per plot was 60 plants and 4 rows of faba bean with the total of 140 plants per plot. Here, two rows of faba bean were sown after every two rows of maize. Phosphorus in the form of TSP at the rate of 46 kg P₂O₅ ha⁻¹ and half of the recommended 87 kg N ha⁻¹ [30] in the form of urea was applied for maize during sowing as basal application 5 cm away from the seeds and the remaining 87 kg N ha⁻¹ was applied when the maize was in the anthesis–silking interval. Phosphorus at the rate of 46 kg P₂O₅ ha⁻¹ and nitrogen at the rate of 18 kg N ha⁻¹ were applied for faba bean as starter during sowing. Sowing of all vaieties was done manually in consortium carried out simultaneously after the seeds were treated for their germination. Weed control was performed manually by hand pulling and the field remained clean of weeds starting from sowing to harvesting. Cypermethrin in 1 ml product to 1 L water ratio was applied directly to the whorl of maize weekly until stalks begin to dry to control American fall armyworm that was occurred when the maize reached nearly knee stage.

2.5. Data collection and measurement

2.5.1. Yield components and yield of maize

Number of ears per plant of maize was recorded from ten randomly selected plants per net plot area at harvest. Number of kernel per ear was recorded from ten randomly taken ears from net plot area. This refers to the number of rows per ear multiplied by number of kernels per row. Thousand kernels weights (g) were counted randomly from bulk of each of the net plot and weigh by using sensitive balance and the weight was adjusted to 12.5% moisture level. All maize stalks from each net plot was harvested near to the ground level and sun dried until constant weight was achieved and the total above ground dry biomass (t ha⁻¹) including the cobs from each net plot area was measured. Grain yield (t ha⁻¹) was recorded as the weight of harvested seed yield from each net plot was recorded and the moisture content of the seed was measured using a moisture meter and the yield was adjusted to 12.5% seed moisture content using the following formula.

$$\mathrm{A}\mathrm{d}\mathrm{j}\mathrm{u}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{d}\mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}=\mathrm{A}\mathrm{c}\mathrm{t}\mathrm{u}\mathrm{a}\mathrm{l}\mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}*\frac{100-\mathrm{M}}{100-\mathrm{D}}$$ (1)

where; M is the measured moisture content in grain and D is the designated moisture content (12.5%).

Harvest index (%) was determined as a ratio of grain yield to above ground dry biomass yield including grain at harvest per net plot area and multiplied by 100.

2.5.2. Yield components and yield of faba bean

The number of total of physiologically mature pods at harvest from five randomly pre tagged plants was counted and the average of these was taken as the total number of pods per plant. Ten randomly selected mature pods of the harvests from the five randomly selected and tagged plants from each net plot was shelled and the seeds was counted and the average of these was taken as the number of seeds per pod. Hundred seeds weight was counted randomly from bulked grain of each net plot having five sets of hundred seeds were weighed and their average was determined as the mean hundred seed weight. The weight was adjusted to 10% moisture level. The above ground dry biomass was measured at physiological maturity stage from ten randomly selected plants from the net plot after sun drying for five days. The weight of harvested seed yield from each net plot was recorded and the moisture content of the seed was measured using a moisture meter AR991 and the yield was adjusted to 10% seed moisture content using the following formula:

$$\mathrm{A}\mathrm{d}\mathrm{j}\mathrm{u}\mathrm{s}\mathrm{t}\mathrm{e}\mathrm{d}\mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}=\mathrm{A}\mathrm{c}\mathrm{t}\mathrm{u}\mathrm{a}\mathrm{l}\mathrm{y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}*\frac{100-\mathrm{M}}{100-\mathrm{D}}$$ (2)

Where; M is the measured moisture content in grain and D is the designated moisture content (10%). Harvest index (%) was calculated as the ratio of grain yield to total above ground dry biomass yield multiplied by 100.

2.5.3. Productivity and competitive indices of intercropping system

Land equivalent ratio (LER): This was calculated to evaluate the productivity of intercropping system. It is defined as the relative land area required as sole crop to produce the same yield as an intercrop system [31].

$$\mathrm{L}\mathrm{E}\mathrm{R}=\frac{\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\mathrm{o}\mathrm{f}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{c}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{p}\mathrm{e}\mathrm{d}\mathrm{m}\mathrm{a}\mathrm{i}\mathrm{z}\mathrm{e}}{\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\mathrm{o}\mathrm{f}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{m}\mathrm{a}\mathrm{i}\mathrm{z}\mathrm{e}}+\frac{\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\mathrm{o}\mathrm{f}\mathrm{i}\mathrm{n}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{c}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{p}\mathrm{e}\mathrm{d}\mathrm{f}\mathrm{a}\mathrm{b}\mathrm{a}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{n}}{\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\mathrm{o}\mathrm{f}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{e}\mathrm{f}\mathrm{a}\mathrm{b}\mathrm{a}\mathrm{b}\mathrm{e}\mathrm{a}\mathrm{n}}$$ (3)

Maize equivalent yield (MEY): Maize equivalent yield is the sum of maize yield in the intercrop system and the converted faba bean yield, and was compared with sole maize crop yield. Maize was the main crop; therefore, yield of the faba bean in the intercrop system was converted to maize yield by multiplying the faba bean yield with faba bean to maize price ratio as:

$${\mathrm{M}}_{\mathrm{E}\mathrm{Y}}={\mathrm{Y}}_{\mathrm{M}\mathrm{F}}+\left(\frac{\mathrm{Y}\mathrm{F}\mathrm{M}\mathrm{x}\mathrm{P}\mathrm{F}}{\mathrm{P}\mathrm{M}}\right)$$ (4)

where; M_EY = Maize equivalent yield; Y_MF = intercrop maize grain yield (kg ha⁻¹); Y_FM = intercrop faba bean seed yield (kg ha⁻¹); P_M = price of maize grain kg⁻¹; P_F = price of faba bean grain kg⁻¹.

Gross monetary value (GMV): It was calculated as the product of yields of the component crops (kg ha⁻¹) multiplied by their respective unit price during harvesting time at the study area. Since there is high local market price fluctuation, the lowest price of Ethiopian Birr (ETB) per kilogram of the component crops was taken. An average current market price of ETB 15.00 kg⁻¹ for maize and ETB 35.00 kg⁻¹ for faba bean grains were taken for the economic analysis. One USD is currently exchanged for 32.2 ETB in the first quarter year of 2020.

Monetary advantage index (MAI): The yields of the component crops in the cropping system were measured in terms of monetary value of return to evaluate its economic benefit. The MAI was calculated as:

$$\mathrm{M}\mathrm{A}\mathrm{I}=\left[\left({\mathrm{P}}_{\mathrm{M}}\times {\mathrm{Y}}_{\mathrm{M}\mathrm{F}}\right)+\left({\mathrm{P}}_{\mathrm{F}}\times {\mathrm{Y}}_{\mathrm{F}\mathrm{M}}\right)\right]\times \frac{\mathrm{L}\mathrm{E}\mathrm{R}-1}{\mathrm{L}\mathrm{E}\mathrm{R}}$$ (5)

Where: P_M = Price of maize; Y_MF = yield of maize in intercropping; P_F = Price of faba bean; Y_FM = yield of faba bean in intercropping; LER = land equivalent ratio.

2.6. Data analysis

Homogeneity tests were made for homogeneity of variances across the years using the F_max test before proceeding to the analysis of variance by the formula:

$${\mathrm{F}}_{\max }=\frac{\mathrm{L}\mathrm{a}\mathrm{r}\mathrm{g}\mathrm{e}\mathrm{r}\mathrm{M}\mathrm{S}\mathrm{e}}{\mathrm{S}\mathrm{m}\mathrm{a}\mathrm{l}\mathrm{l}\mathrm{e}\mathrm{r}\mathrm{M}\mathrm{S}\mathrm{e}}$$ (6)

As the F_max ≤ 3.00, the parameter is considered homogeneous so that combined analysis of variance (ANOVA) for the two year data was performed using SAS (statistical analysis system) version 9.4 program (SAS Institute, 2016). Differences among treatment means were delineated using LSD (least significance difference) at 5% level of significance when the ANOVA showed significant differences. Contrast analysis was also included to estimate the effects of sole versus intercrop crops.

3. Results and discussion

3.1. Maize phenology and growth parameters

3.1.1. Days to 50% tasseling and silking

Both days to 50% tasseling and days to 50% silking were not significantly affected due to faba bean varieties, spatial arrangement of component crops, cropping system and their interaction.

3.1.2. Days to physiological maturity

The duration required for maize to reach physiological maturity was not significantly affected due to spatial arrangement of component crops. Faba bean varieties significantly (p < 0.01) affected days to physiological maturity of maize crop (Table 2). The ANOVA result also revealed that maize crop intercropped with faba bean Gachena variety required the highest number of days to physiological maturity (141.28 days) and it was at par with the duration required for intercropping with Baqela Habasha variety (140.39 days).

Table 2.

Effects of faba bean varieties and spatial arrangement on phenology, plant height and leaf area index of maize planted in sole and intercropped with faba bean varieties at Haramaya.

Factors	DTT	DTS	DPM	PH (cm)	LAI
Faba bean varieties
M + Baqela Habasha	75.61	82.11	140.39ab	201.55	3.85
M + Baqela Faranji	75.06	81.67	139.94bc	203.69	3.92
M + Batte	74.89	81.61	138.72c	202.47	3.91
M + Gachena	75.39	82.11	141.28a	201.71	3.92
F-test	Ns	Ns	**	Ns	Ns
LSD (5%)	0.89	1.06	1.29	5.48	0.23
Spatial arrangement
1 M: 1 F B	75.13	81.67	140.13	200.21	3.94
1 M: 2 F B	75.46	82	140.33	201.84	3.98
2 M: 2 F B	75.13	81.96	139.79	205.01	3.77
F-test	Ns	Ns	Ns	Ns	Ns
LSD (5%)	0.77	0.92	1.12	5.75	0.22
CV (%)	1.70	1.87	1.33	3.91	8.96
Cropping system
Intercropped maize	75.24	81.88	140.08	202.4	3.9
Sole maize	74	80.33	143	200.7	3.71
F-test	Ns	Ns	Ns	Ns	Ns
LSD (5%)	4.18	4.33	5.75	9.93	0.38
CV (%)	6.6	6.3	4.8	5.8	11.4

Means in the same column followed by the same letter(s) are not significantly different at 5% level of significance according to LSD test; M = maize; F = faba bean; DTT = Days to 50% tasseling; DTS = Days to 50% silking; DPM = Days to physiological maturity; PH = Plant height; LAI = Leaf area index; CV = Coefficient of variation; ns = not significant at p < 0.05; *,** and *** indicate significant difference at probability level of 0.05, 0.01 and 0.001, respectively.

3.1.3. Plant height (cm)

The main effects of spatial arrangement, faba bean varieties and cropping system and their interaction did not significantly affect maize plant height.

3.1.4. Leaf area index (LAI)

The analysis of variance results revealed that leaf area index of maize was not significantly affected by the spatial arrangement, faba bean varieties, cropping system, and their interactions.

3.2. Effects on maize yield and yield components

3.2.1. Number of ears per plant

Maize number of ears per plant was not varied due to cropping system and the main effects interactions. However, it was significantly affected by spatial arrangement and faba bean varieties (Table 3). Thus, the number of ears per plant of maize intercropped with Yehabesha Baqela variety was the maximum (1.47); whereas the number of ears per plant of other faba bean varieties used in intercropping with maize remained statistically the same. This may be attributed to the less competition effect of Yehabesha Baqela with maize. Similar result was reported by Thobatsi [32] where significantly maximum number of ears per plant (1.48) of maize intercropped with PAN311 and minimum number of ears per plant (1.01) in maize intercropped with Agrinawa variety of cowpea. The results also revealed that the number of ears per plant of maize plants intercropped in 2 M:2 F B spatial arrangement was maximum (1.48) and the minimum number of ears per plant (1.33) was recorded for 1 M:2 F B spatial arrangement. Maize plants intercropped in 2 M:2 F B spatial arrangement might get better space to grow free from competition.

Table 3.

Main effects of faba bean varieties and spatial arrangement on NEPP, NKPE, TKW, AGDB, GY and HI of maize planted in sole and intercropped with faba bean varieties at Haramaya (combined data over 2018 and 2019 cropping year).

Treatments	NEPP	NKPE	TKW (g)	AGDB (t ha−1)	GY (t ha−1)	HI (%)
Faba bean varieties
M + Yehabesha Baqela	1.47a	548.23	278.05	15.67b	4.83	31.49
M + Yeferenji Baqela	1.37b	542.71	273.43	16.31a	5.06	31.87
M + Batte	1.39b	541.17	272.99	15.18b	4.97	33.44
M + Gachena	1.37b	562.80	272.45	16.58a	5.09	31.9
F-test	*	Ns	Ns	***	Ns	Ns
LSD (5%)	0.07	Ns	Ns	0.59	Ns	Ns
Spatial arrangement
1 M: 1 F B	1.4b	553.18	271.64	15.82b	4.96b	32.67
1 M: 2 F B	1.33c	554.68	271.87	15.00c	4.63c	31.98
2 M: 2 F B	1.48a	538.33	279.19	16.99a	5.37a	36.86
F-test	***	Ns	Ns	***	***	Ns
LSD (5%)	0.06	Ns	Ns	0.51	0.24	Ns
CV (%)	6.93	6.79	5.80	5.47	7.86	9.07
Cropping systems
Intercropped maize	1.40	548.7	274.2	15.93b	4.99b	32.18
Sole maize	1.37	550.8	293.7	19.40a	5.91a	31.47
F-test	Ns	Ns	Ns	***	***	Ns
LSD (5%)	Ns	Ns	53.37	3.26	0.6	Ns
CV (%)	18.5	10.7	22.9	23.7	13.9	15.4

Means in the same column followed by the same letter(s) are not significantly different at 5% level of significance according to LSD test; M = maize; F = faba bean; NEPP = Number of ears per plant; NKPE = Number of kernels per ear; TKW = Thousand kernel weight; AGDB = Above ground dry biomass; GY = Grain yield; HI = Harvest index; CV = coefficient of variation; ns = Not significant at p < 0.05; *, ** and *** indicates significant difference at probability level of 0.05, 0.01 and 0.001, respectively.

3.2.2. Number of kernel per ear

Analysis of variance of the combined data of the two years demonstrated non-significant (p > 0.05) at the expense of variety, spatial arrangement, and cropping system and their interaction.

3.2.3. Thousand kernels weights

Thousand kernels weight was not significantly affected by faba bean variety, spatial arrangement, cropping system, and their interactions (Table 3).

3.2.4. Aboveground dry biomass

The aboveground dry biomass (t ha⁻¹) of maize was significantly (p < 0.001) affected by the variety, spatial arrangement, and cropping system. The result also revealed that intercropping of maize with different faba bean varieties resulted in significant differences in aboveground dry biomass (Table 3). Thus, the maximum aboveground dry biomass was recorded for maize plants intercropped with Gachena variety (16.58 t ha⁻¹) which was in statistical parity with Yeferenji Baqela (16.31 t ha⁻¹). These varieties might contribute good environment for the maize plant rather than competing for growth resources.

On the other hand, maize intercropped in 2 M:2 F B spatial arrangement gave the maximum aboveground dry biomass (16.99 t ha⁻¹) and the minimum aboveground dry biomass of maize was recorded for 1 M:2 F B spatial arrangement that provided aboveground dry biomass of 15.00 t ha⁻¹. The maize crop intercropped with faba bean at 2 M:2 F B spatial arrangement might had comfortable space to grow robust that made the aboveground dry biomass become heaviest. Similar result was reported by Jenani-oskooi et al. [33]; and Oskoii et al. [34] that sole maize and 2:2 planting pattern in maize-faba bean intercropping system gave the highest biological yield compared to intercropped system and different intercropping patterns, respectively. Sole-cropped maize had significantly higher aboveground dry biomass (19.4 t ha⁻¹) than intercropped maize (15.93 t ha⁻¹) due to the no intra-competition of maize from faba bean. In agreement with this result, Oskoii et al. [34] that higher aboveground dry biomass (2.91 kg m⁻²) in sole-cropped maize and lower aboveground dry biomass (1.31 kg m⁻²) of maize intercropped with faba bean.

3.2.5. Grain yield

The combined analysis of variance of the two-year data showed that spatial arrangement and cropping system significantly (p < 0.001) influenced the grain yield of the maize component crop (Table 3). However, maize grain yield was not affected by faba bean variety and the interactions between the main effects. The results revealed that the highest grain yield of maize was recorded for the intercropped in 2 M:2 F B spatial arrangement (5.37 t ha⁻¹) and the lowest grain yield of maize plants (4.63 t ha⁻¹) was obtained from the intercropped maize with faba bean in 1 M:2 F B spatial arrangement. This highest grain yield increment comes as the expense of highest number of ears per plant of the maize component crop. In agreement to this result, Sutharsan and Srikrishnah [35] reported the highest yield of intercropped maize in 2:2 spatial arrangements of maize and groundnut intercropping. Similarly, Oskoii et al. [34] reported the highest grain yield from 2:2 maize to faba bean intercropping patterns (728.8 g m⁻²) and the lowest grain yield (398.1 g m⁻²) from 1:2 strip intercropping pattern. As the expense of cropping systems, maize cropped in sole system gave the higher grain yield (5.91 t ha⁻¹) than the intercropped maize (4.99 t ha⁻¹) with faba bean varieties. It gave 15.6% extra grain yield compared to the intercropped maize. This result was recorded due to the sole-cropped maize had no stiff competition from the neighbours for growth resources. This result is in agreement with Paudel et al. [36] that sole-cropped maize gave the maximum grain yield (5.83 Mg ha⁻¹) compared to the intercropped maize (4.32 Mg ha⁻¹) in maize-soybean intercropping system.

3.2.6. Harvest index

Harvest index (%) was not significantly affected due to cropping system, varieties, spatial arrangement and their interactions.

3.3. Faba bean components

3.3.1. Phenology and growth parameters of faba bean

3.3.1.1. Days to flower initiation

Days to flower initiation of faba bean were not significantly affected by spatial arrangement. However, days to flower initiation was highly significantly (p < 0.001) affected by cropping system as well as significantly (p < 0.05) affected by faba bean varieties. Intercropping different faba bean varieties with maize also resulted in significant differences in days to flower initiation (Table 4). Significantly delayed days to flower initiation (48.39 days) were recorded for the variety Gachena as compared to the other varieties. Varietal difference observed on days to flower initiation could be related to their genotypic difference. Similarly, Debela [37] obtained significant variation among faba bean varieties in which variety Tumsa reached days to 50% flowering after 50.2 days followed by Hachalu (48.8 days). Sole-cropped faba bean reached days to flower initiation more later (50.54 days) than intercropped faba bean (47.53 days). This implies that the presence of competition for growth resources in intercropped faba bean initiated flowering faster than the sole-cropped faba bean.

Table 4.

Effects of faba bean varieties and spatial arrangement on phenology and growth parameters of faba bean planted in sole and intercropped with maize at Haramaya.

Factors	DFI	DPM	PH (cm)	NPB	LA (cm2)	LAI
Faba bean varieties
M + Baqela Habasha	47.22b	135.83c	115.38b	1.17	1238.98c	3.1c
M + Baqela Faranji	47.11b	138.11ab	121.42b	1.15	1282.67bc	3.21bc
M + Batte	47.39b	138.72a	114.90b	1.33	1322.67b	3.31b
M + Gachena	48.39a	136.89bc	136.24a	1.27	1551.1a	3.88a
F-test	*	***	***	Ns	***	***
LSD (5%)	0.93	1.23	7.06	0.19	69.32	0.17
Spatial arrangement
1 M: 1 F B	47.08	136.25b	122.50	1.43a	1390.79a	3.48a
1 M: 2 F B	47.50	137.54a	121.58	1.26b	1345.98ab	3.37ab
2 M: 2 F B	48.00	138.38a	121.87	1.01c	1309.8c	3.28b
F-test	Ns	***	Ns	***	*	*
LSD (5%)	0.97	1.06	6.11	0.14	60.03	0.15
CV (%)	2.84	1.34	8.50	17.07	7.65	7.66
Cropping systems
Intercropped faba bean	47.53b	137.39a	127.6	1.23b	1349	3.37b
Sole faba bean	50.54a	130.04b	134.4	2.79a	1422	3.56a
F-test	***	***	Ns	***	Ns	**
LSD (5%)	2.43	3.38	10.19	0.17	80.1	0.2
CV (%)	10.7	5.3	18.5	22.9	12.5	12.5

Means in the same column followed by the same letter(s) are not significantly different from each other at 5% level of significance according to LSD test; M = maize; F = faba bean; DFI = Days of flower initiation; DPM = Days to physiological maturity; PH = Plant height; NPM = Number of primary branches; LA = leaf area; LAI = Leaf area index; CV = Coefficient of variation; ns = Not significant at p < 0.05; *,** and *** indicates significant difference at probability level of 0.05, 0.01 and 0.001, respectively.

3.3.1.2. Days to physiological maturity

The combined analysis of variance of the days to physiological maturity of faba bean showed significant (p < 0.001) effect due to varieties, spatial arrangement and cropping systems. The results revealed that faba bean variety Batte took the longest duration (138.72 days) to reach physiological maturity while the earliest days to maturity was recorded for variety Baqela Habasha (135.83 days). Similalry, Ashenafi and Mekuria [38] obtained significant differences among faba bean varieties for days to 90% physiological maturity where the maximum days to 90% physiological maturity was recorded from variety Wolki (134.7 days) and Hachalu (134.0) varieties at Sinana district.

All faba bean varieties intercropped with maize in 2 M:2 F B and 1 M:2 F B spatial arrangements required significantly higher number of days to physiological maturity than faba bean varieties intercropped with maize in 1 M:1 F B spatial arrangement (Table 4). This may be due to the fact that faba bean varieties in 1 M:1 F B spatial arrangement were exposed to full sunlight that enhanced growth and development to complete physiological maturity early. Intercropped faba bean varieties required significantly longer duration (137.39 days) of days to physiological maturity than sole-cropped maize (130.04 days). This implies that intercropped faba bean crops complete its physiological maturity later than sole-cropped faba bean attributed to conserve sufficient moisture in soil that helped the faba bean to continue its normal independent growth. Consistent to this result, Thobatsi [32] reported significantly longer duration to physiological maturity for intercropped cowpea (121.33 days) and the shorter days to physiological maturity (114.67 days) for sole-cropped cowpea.

3.3.1.3. Plant height (cm)

Combined analysis of variance of two years faba bean plant height data showed significant difference due to faba bean varieties (Table 4). The results revealed that Gachena variety had the maximum plant height (136.24 cm) and the shortest plants were obtained from the other faba bean varieties all of which were in statistical parity with each other. Gachena variety is an improved variety that it is genetically tall.

3.3.1.4. Number of primary branches

The number of primary branches of the component faba bean varieties were significantly (p < 0.001) affected by spatial arrangement and cropping systems. However, varieties and the interactions did not significantly affect the number of primary branches of faba bean (Table 4). Significantly highest number of primary branches (1.43) of faba bean varieties was recorded in a 1 M:1 F B spatial arrangement while the minimum number of primary branches (1.01) was recorded in a 2 M:2 F B spatial arrangement. The least number of primary branches per plant in a 2 M:2 F B spatial arrangement might be due to shading effect from the maize crop as the faba bean varieties were planted more closer to the maize. In addition, in 2 M:2 F B spatial arrangement, there is inter- and intra species competition whereas there is only inter species competition in 1 M:1 F B spatial arrangement. The maximum number of primary branches (2.79) was recorded in sole-cropped faba bean compared to intercropped faba bean (1.23) (Table 4). The competition imposed from maize on the intercropped faba bean reduced the branching ability of the faba bean crop. In agreement with this result, Abou-Keriasha et al. [39] obtained that number of branches per plant of faba bean was decreased when intercropped with onion and wheat compared with sole faba bean.

3.3.1.5. Leaf area (cm2)

The analysis of variance indicated that leaf area per plant of the component faba bean varieties was significantly (p < 0.001) affected by the effect of spatial arrangement, and varieties. The results revealed that Gachena variety had the highest leaf area (1551.1 cm²) while the lowest leaf area (1238.98 cm²) was obtained from Baqela Habasha (Table 5.4). This implies that faba bean varieties had inherently varied leaf area. A similar result was reported by, Shabbir et al. [40] that cultivar PBA Nanu had significantly the least leaf area, 52% less than the rest of cultivars and the leaf area of PBA Marne was 24% higher than PBA Warda faba bean cultivar. The maximum mean leaf area (1422.37 cm²) was recorded in sole-cropped than intercropped faba bean (1349.13 cm²).

Table 5.

Effects of faba bean varieties and spatial arrangements on yield components and yield of component crops in maize-faba bean intercropping system during main growing seasons of 2018 and 2019 at Haramaya (combined data over 2018 and 2019 cropping year).

Treatments	NPPP	NSPP	HSW (g)	AGDB (t ha−1)	SY (t ha−1)	HI (%)
Faba bean varieties
M + Yehabesha Baqela	4.54b	2.85	57.42c	2.65b	0.61b	25.22
M + Yeferenji Baqela	4.63b	2.86	58.34c	2.88b	0.57b	20.34
M + Batte	4.52b	2.79	67.38a	2.89b	0.63b	22.32
M + Gachena	5.49a	2.89	62.74b	3.77a	0.88a	22.56
F-test	*	Ns	***	***	***	Ns
LSD (5%)	0.69	Ns	3.22	0.45	0.12	Ns
Spatial arrangement
1 M: 1 F B	5.27a	2.91a	62.81	3.81a	0.86a	23.58
1 M: 2 F B	4.98a	2.89a	61.40	3.13b	0.66b	21.46
2 M: 2 F B	4.14b	2.76b	60.20	2.21c	0.49c	22.8
F-test	**	*	Ns	***	***	Ns
LSD (5%)	0.6	0.11	Ns	0.39	0.11	Ns
CV (%)	15.62	6.39	8.15	18.51	21.97	21.26
Cropping systems
Intercropped faba bean	4.80b	2.85b	56.5b	3.05b	0.67b	22.61
Sole faba bean	11.29a	3.08a	61.5a	8.51a	2.04a	24.03
F-test	***	***	***	***	***	Ns
LSD (5%)	0.98	0.14	4.84	0.75	0.19	Ns
CV (%)	32.6	10.4	17.2	36.1	39.1	24.4

Means in the same column followed by the same letter(s) are not significantly different at 5% level of significance according to LSD test; M = maize; F = faba bean; NPPP = Number of pods per plant; NSPP = Number of seeds per plant; HSW = Hundred seed weight; AGDB = Above ground dry biomass; SY = Seed yield; HI = Harvest index; CV = Coefficient of variation; ns = Not significant at P < 0.05; *, ** and *** indicates significant difference at probability level of 0.05, 0.01 and 0.001, respectively.

3.3.1.6. Leaf area index

The faba bean leaf area index was significantly affected by growing season and cropping system (p < 0.01), varieties (p < 0.001) and spatial arrangement (p < 0.05) (Table 4). Gachena variety had the highest leaf area index (3.88) while the lowest leaf area index (3.1) was obtained from Baqela Habasha (3.1). The highest leaf area index for Gachena variety could be due to the highest leaf area it recorded. In line with this result, Mebrahtu et al. [41] reported significant difference between the faba bean varieties in leaf area index where variety Gebelcho had greater leaf area index (5.1) compared to the local variety (4.6). The leaf area index of faba bean varieties intercropped with maize in a 1 M:1 F B spatial arrangement recorded the maximum leaf area index (3.48) and it was at par with the leaf area index obtained from 1 M:2 F B spatial arrangement. The faba bean in 1 M:1 F B spatial arrangement is less prone to competition that helped to have higher leaf area index. Similar trend was reported by Tilahun [42] that significantly higher leaf area index of faba bean was recorded in a1 maize: 2 faba bean row arrangement. The sole-cropped faba bean had higher leaf area index (3.56) compared to intercropped faba bean (3.37). Faba bean varieties produced higher leaf area in sole cropping owing to less competition for growth resources. In accord to this result, Abera et al. [43] reported higher leaf area index (4.25) for sole crop common bean and the lower leaf area index (2.02) in intercropped common bean with maize.

3.3.2. Yield components and yield of faba bean

3.3.2.1. Number of pods per plant

Combined analysis of variance of number of pods per plant showed significant differences due to cropping system, spatial arrangement, and faba bean varieties. Gachena variety in intercropped system produced significantly highest number of pods per plant (5.49) as compared to the other varieties. The variety Gachena was superior in number of pods per plant as it is an improved variety. Similar result was reported by Ashenafi and Mekuria [38] that the maximum pods per plant were recorded from Degaga (20.39) and the lowest number of pods per plant were recorded for varieties Tumsa and Hachalu.

The result also revealed that the number of pods per plant was significantly affected in response to spatial arrangement intercropped with maize. The 1 M:1 F B and 1 M:2 F B spatial arrangements recorded significantly highest number of pods per plant (5.27 and 4.98, respectively) while the lowest number of pods per plant was recorded for 2 M:2 F B spatial arrangement (Table 5). Better sun light and nutrients were expected to be used by the faba bean grown in 1 M:1 F B and 1 M:2 F B spatial arrangements that contributed to higher number of pods per plant. A similar result was reported by Oskoii et al. [34] that the highest number of pods per plant was observed in 1 M:1 F B spatial arrangement (3.87) and the lowest in 1 M:2 F B spatial arrangement (2.57) was achieved in maize and faba bean cropping pattern. On the other hand, sole-cropped faba bean recorded significantly higher number of pods per plant (11.29) than the intercropped faba bean (4.80). Increase in the competition for light and nutrients and consequently enhanced shading in intercropping system led to decrease in photosynthesis and so more leaf abscission might have decreased the number of pods per plant. Similar to this result, Oskoii et al. [34] obtained the maximum number of pod per plant (4.8) in sole cropping system than in intercropping (3.21). Getachew et al. [44] also reported more faba bean pod per plant in sole (10.5) compared to its intercropping system with barley (9.8).

3.3.2.2. Number of seeds per pod

Number of seeds per pod of faba bean component crop was highly significantly affected by the cropping systems and spatial arrangement. However, the main effects of varieties and their interactions did not significantly affect the faba bean number of seeds per plant. The results also revealed that the maximum number of seeds per pod of faba bean varieties intercropped with maize plants was recorded in a 1 M:1 F B (2.91) and 1 M:2 F B (2.89) spatial arrangement both showed statistical parity (Table 5). The faba bean plants grown in 2 M:2 F B spatial arrangement were l under the heavy shade of the two maize rows and stiff competition for growth resources also expected as faba bean rows were much nearer to the maize rows that led to lowest number of seeds per plant (2.76). The maximum mean number of seeds per pod t was recorded in sole-cropped (3.08) compared to intercropped faba bean (2.85). The reduction in the number of seeds per pod in intercropping system might be due to interspecific competition. In contrary to this result, Oskoii et al. [34] obtained no significant differences between the different spatial arrangements and cropping systems for the number of faba bean seed per pod in maize-faba bean intercropping system.

3.3.2.3. Hundred seed weight

The main effects of cropping year, varieties and cropping systems were significant (p < 0.001) on hundred seed weight of faba bean. But, hundred seed weight of faba bean was not significantly affected by the component crops spatial arrangement and interactions of main factors. The faba bean variety Batte had the maximum hundred seed weight (67.38 g) followed by Gachena variety (62.74 g) (Table 5). On the other hand, Yehabesha Baqela and Yeferenji Baqela varieties intercropped with maize recorded the lowest hundred seed weight. This is due to the fact that the varieties do have different seed size and endosperm genetically that affects its seed weight. In line with this result, Bakry et al. [45] reported significant differences among faba bean varieties on hundred seed weight (77–106.7 g) were recorded. Significantly higher hundred seed weight (61.5 g) was obtained for sole-cropped faba bean compared to the intercropped faba bean (56.5 g). The higher hundred seed weight might be due to absence of interspecific competition in sole-cropped faba bean plants that the seeds fully developed in size and endosperm making the seeds heavier in weight. In agreement to this result, Mahmoud et al. [46] reported that weight of hundred seed of faba bean was decreased when intercropped with onion, garlic and fennel compared with sole faba bean.

3.3.2.4. Aboveground dry biomass

Aboveground dry biomass of the combined analysis of variance showed significant (p < 0.001) difference due to the effect of cropping year, varieties, spatial arrangement and cropping systems. The analysis also indicated that Gachena variety produced significantly the highest aboveground dry biomass (3.77 t ha⁻¹) as compared to the other varieties. The Gachena variety is improved variety that had the maximum aboveground dry biomass derived from its genetic variability. In line with this result, Kissi and Tamiru [47] reported significant difference among the varieties for the aboveground biomass yield where Gebelcho variety produced higher biomass yield (17.6%) compared with Shallo.

The results also revealed significantly highest aboveground dry biomass (3.81 t ha⁻¹) of faba bean varieties intercropped with maize plants in 1 M:1 F B spatial arrangement while the lowest aboveground dry biomass (2.21 t ha⁻¹) was observed in 2 M:2 F B spatial arrangement (Table 5). The maximum aboveground dry biomass in 1 M:1 F B spatial arrangement was a function of highest number of primary branches of faba bean. Similarly, Prasad and Brook [48] reported that with increasing maize density, resulted in decreasing transmission of light to the intercropped legumes. Contrast analysis showed that sole-cropped faba bean gave significantly higher aboveground dry biomass (8.51 t ha⁻¹) as compared to the intercropped faba bean (3.05 t ha⁻¹). The high aboveground dry biomass in sole cropping is mainly due to absence of interspecific competition and high stand counts in the net plot of sole-cropped than intercropped faba bean. Getachew et al. [44] also reported that the biological yield of faba bean in intercropping decreased compared to the sole culture treatment as a result of interspecific competition with barley crop.

3.3.2.5. Seed yield

The seed yield of faba bean was significantly (p < 0.001) affected by variety, spatial arrangement and cropping systems. Gachena variety gave significantly highest seed yield (0.88 t ha⁻¹) as compared to the other varieties (Table 5). This indicated that Gachena variety is the high yielding improved variety that it out yielded the other varieties. Similar result was reported by Getnet and Yehizbalem [49] that there was significant difference in seed yield of different faba bean varieties. Ashenafi and Mekuria [38] also reported a significant difference among faba bean varieties (3703.7–4886.8 kg ha⁻¹) on grain yield.

The results also revealed that the 1 M:1 F B spatial arrangement provided the maximum faba bean seed yield (0.86 t ha⁻¹) and the minimum seed yield (0.49 t ha⁻¹) was obtained due to 2 M:2 F B spatial arrangement of component crops. This significant difference might arise from the variation in number of pods per plant, number of seeds per pods and the 100 seed weight. In addition, when the faba bean is planted in 1 M:1 F B spatial arrangement it remained at middle row of two maize rows and the shade effect from the maize stand from both side were remained less. Therefore, the faba bean plants can get relatively wider space between the two rows of maize canopy and enough sunlight that used for photosynthesis. Intercropping of high and low canopy crops helps to improve light interception and hence yields of the shorter crops requires that they be planted between sufficiently wider rows of the taller once [50]. Significantly higher mean seed yield (2.04 t ha⁻¹) was recorded in sole-cropped than the intercropped faba bean (0.67 t ha⁻¹). This resulted mainly due to the higher number of faba bean populations in the net plot with no competition from other species of crop. This result is in agreement with Mahmoud et al. [46] that seed yield of faba bean was decreased when intercropped with onion, garlic and fennel compared with sole faba bean in both seasons.

3.3.2.6. Harvest index

Combined analysis of variance of the faba bean harvest index was not significantly varied due to varieties, spatial arrangement, cropping system, and their interactions.

3.4. Productivity and economic advantage of intercropping

3.4.1. Land equivalent ratio

The land use or intercrop efficiency indicated by land equivalent ratio (LER) was significantly (p < 0.001) affected by the spatial arrangement (Table 6). Even though there were no significant differences among the treatments of faba bean varieties, the land equivalent ratio in all varieties showed above unity ranging from 1.136 for Batte to 1.2 for Yeferenji Baqela varieties provided that 13.6% up to 20% land use efficiency. Accordingly, a 1 M:1 F B spatial arrangement gave significantly the highest land equivalent ratio (1.268) as compared to the other spatial arrangements. The 1 M:2 F B gave the lowest land equivalent ratio. Evaluation of land equivalent ratio showed a significant variation among the spatial arrangements and 1 M:1 F B arrangement gave the highest land use efficiency, i.e. 26.8% more efficient than growing both crops in sole stand. This indicates that 26.8% more area would be required by a sole cropping system to equal the yield of intercropping system. In contrary to this result, Jenani-oskooi et al. [33] reported that strip intercropping with ratio of 2 M:2 F B dedicated highest ratio of LER and the lowest LER was recorded for 1 M:1 F B spatial arrangement.

Table 6.

Main effects of faba bean varieties and their plant population on land equivalent ratio, maize equivalent yield, gross monetary value, and monetary advantage index of maize-faba bean intercropping at Haramaya, east Hararghe, Ethiopia.

Treatments	LER	MEY (kg ha−1)	Monetary value (ETB ha−1)			MAI
			Maize (A)	Faba bean (B)	GMV (A + B)
Faba bean varieties
M + Yehabesha Baqela	1.182	5628.63b	65,195	19234b	84430b	+12042b
M + Yeferenji Baqela	1.2	5746.62b	68,285	17915b	86199b	+14191ab
M + Batte	1.136	5790.00b	67,100	19751b	86850b	+10748b
M + Gachena	1.193	6420.53a	68,653	27655a	96308a	+17056a
F-test	Ns	***	Ns	***	***	*
LSD (5%)	Ns	351.5	Ns	3803.4	5272.4	4822.1
Spatial arrangement
1 M: 1 F B	1.268a	6277.49a	66959b	27203a	94162a	+18761a
1 M: 2 F B	1.11b	5541.25c	62456c	20663b	83119c	+6872.75b
2 M: 2 F B	1.155b	5870.60b	72509a	15551c	88059b	+14894a
F-test	***	***	***	***	***	***
LSD (5%)	0.07	304.4	3192.6	3293.8	4566.1	4176.1
Cropping systems
Intercropped maize	1.178	5896a	67308b	21139b	–	–
Sole maize	1.0	5315b	76720a	64129a	–	–
F-test		*	***	***
LSD (5%)		840.5	8059.3	5831.2

M = Maize; FB = Faba bean; Means in a column for treatments with the same letter are not significantly different at p ≤ 0.05; *, **, *** Significant at p ≤ 0.05, p ≤ 0.01 and p ≤ 0.001, respectively; ns = not significant; LSD = Least significant difference; ETB = Ethiopian Birr = 1 US dollar = 32.2 ETB; LER = land equivalent ratio; GMV = gross monetary value; MAI = monetary advantage index.

3.4.2. Maize equivalent yield

Maize equivalent yield (MEY) was significantly affected by varieties, spatial arrangement, and cropping system (Table 6). Intercropping maize with faba bean variety Gachena variety produced significantly the highest MEY (6420.53 kg ha⁻¹) than the other faba bean varieties. Spatial arrangement of 1 M:1 F B gave significantly the highest MEY (6277.49 kg ha⁻¹) while the least MEY (5541.25 kg ha⁻¹)was obtained from 1 M:2 F B spatial arrangement (Table 4). The additional faba bean yield from the intercropped treatments provided the highest maize equivalent yield for the intercrop treatments compared with sole crop maize. A higher maize equivalent yield was recorded in intercropped (5896 kg ha⁻¹) than the sole-cropped maize (5315 kg ha⁻¹). Similarly, higher maize equivalent yield produced in maize and faba bean combination illustrated that intercropping was more profitable over sole planting of maize. In agreement with the result, Paudel et al. [36] obtained higher MEY (8.19 Mg ha⁻¹) in intercropped maize with soybean than sole cropped maize (5.83 Mg ha⁻¹).

3.4.3. Gross monetary value

Gross monetary value (GMV) was significantly (p < 0.001) affected due to varieties and spatial arrangement (Table 6). Planting of maize-faba bean in 1 M:1 F B spatial arrangement resulted in significantly highest GMV (94,162 ETB ha⁻¹) while planting in 1 M:2 F B spatial arrangement provided the lowest GMV (83,119 ETB ha⁻¹). Generally, extra GMV of 18.5% was obtained due to maize-faba bean intercropping in 1 M:1 F B spatial arrangement than sole maize cropping system (Table 4). The results are in agreement with Molatudi and Mariga [51] who concluded that maize-dry bean intercropping was clearly superior to sole maize in terms of monetary value. Similarly, Wondimu [52] obtained higher monetary returns from maize-faba bean intercropping than sole cropping of either faba bean or maize.

3.4.4. Monetary advantage index

Monetary advantage index (MAI) of the treatments was significantly influenced by spatial arrangements and varieties (Table 6). All the MAI values were positive due to LER values which were greater than one showing a definite yield advantage of maize-faba bean intercropping system. In line with this result, Aasim et al. [53] reported positive monetary advantage index in cotton-cowpea intercropping systems compared to sole cropping. The maximum MAI values were recorded for intercropping with variety Gachena (+17,056). On the other hand, the highest MAI values were obtained in the 1 M:1 F B (+18,761) indicating the suitability for maize-faba bean intercropping system as compared to sole cropping. In agreement to this result, Tenaw et al. [54] reported that 1:1 cropping pattern gave the highest MAI (9056) in faba bean and barley intercropping system.

4. Conclusion

The results of the experiment showed that high yields of the component crops obtained were differed in spatial arrangement. In case of maize, the results indicated that the best grain yield was obtained from a 2 M:2 F B spatial arrangement. In contrast, the best yield and yields components of faba bean was recorded from a spatial arrangement of 1 M:1 F B. The grain yields of maize and faba bean were highest in respective of pure stands, attributable to the absence of inter-specific competition and more stand count per unit area, respectively. Land equivalent ratio values recorded were greater than unity, implying that it will be more productive to intercrop maize and faba bean than growing them in monoculture. In case of faba bean varieties used, Gachena variety provided the best maize equivalent yield and gross monetary value. Furthermore, intercropping of maize with faba bean in 1 M:1 F B spatial arrangement should be adopted by farmers since that treatment recorded the most efficient, recorded the maximum land equivalent ratio, maize equivalent yield, gross monetary value and monetary advantage index. Therefore, ultimate consideration for selection of best intercropping system is the monetary advantages and production efficiency of the system. Thus, based on this experiments results, maize variety Baate intercropped along with faba bean variety Gachena and 1 M:1 F B spatial arrangement gave superior yields and recommended for the farmers of the study areas of eastern Ethiopia.

Author contribution statement

Negera Nurgi: Performed the experiments; Wrote the paper.

Tamado Tana: Conceived and designed the experiments.

Nigussie Dechassa: Bulti Tesso: Analyzed and interpreted the data.

Yibekal Alemayehu: Contributed reagents, materials, analysis tools or data.

Data availability statement

Data will be made available on request.

Additional information

No additional information is available for this paper.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper