Intercropping garlic in strawberry fields improves land equivalent ratio and gross income. Intercropping garlic in strawberry fields improves land equivalent ratio and gross income

: Studies showed that intercropping garlic reduced pests in strawberry field crops. However, influence of intercropping on yield was not tested. The objective of the study was to evaluate the strawberry pseudofruit and garlic bulb productions in monocropping and intercropping systems. Assessments of the yields and calculation of the land equivalent ratio, competition ratio and gross income were performed. The experiments were conducted in three areas (two open field and one greenhouse) in Londrina municipality. Treatments in the field experiments were garlic or strawberry in monocrops (controls), strawberry (S) + one garlic row (GR), S + 2GR or S + 3GR per plot. In the greenhouse experiment, plants were grown in pots with following treatments: garlic or strawberry in monocrops, 2S + 2 garlic plants per plot (GPP), 2S + 4GPP or 2S + 5GPP. Similar yields (garlic bulbs and strawberry pseudofruits) were observed among the treatments. Intercropping garlic among strawberry plants increased the land equivalent ratio. The intercrop land equivalent ratio index ranged from 1.34 to 2.55. An increasing in gross income were observed when increasing garlic plant densities in intercropping with strawberry. Results showed that intercropping garlic with strawberry increases land equivalent ratio and gross income. Production of strawberry pseudofruits and garlic bulbs were not influenced by intercropping systems compared to monocropping.


INTRODUCTION
Monocrops predominate in farming practices due to the simplicity of their management to achieve agricultural yields. However, the concentration of resources under monocropping increases the incidence of diseases and pests, which may reduce crop productivity. In contrast, if intelligently designed, plant diversification schemes may reduce the number of crop pests and increase the number of their natural predators, as shown by a metaanalysis including 552 experiments (LETOURNEAU et al., 2011, GREENOP et al., 2018. In general, these cropping systems are mostly suitable for small farmers whose main income source is the cultivation of vegetables. A wide range of combinations of plants are possible due to the vast number of horticultural crops available. The use of intercropping with vegetable species, such as aromatic or spicy plants, has high potential to improve land equivalent ratio (ANJUM et al., 2015;ISLAM et al., 2016;SCHMITT et al., 2016). These cropping systems collaborated to save production resources such as water and fertilizer, and manpower usage becomes more efficient, which contributed to the development of agroecosystem sustainability. For example, intercropping garlic (Allium sativum L.), onion (Allium cepa L.) or coriander (Coriandrum sativum L.) in mustard (Brassica napus L.) field reduced aphid incidence (NOMAN et al., 2013). Although the mustard seed production was diminished, the income generated by the intercropped plants was very high (three times more than the monocrops) (NOMAN et al., 2013).
The candidates used in intercropping systems must have similar agronomic and climatic requirements. Strawberry (Fragaria × ananassa Duch.) plants are herbaceous and perennial, and their edible part is formed by a fleshy receptacle (pseudofruit) (FILGUEIRA, 2008). The strawberry pseudofruit production is affected by temperature, photoperiod, soil conditions and the phytosanitary conditions (ZEIST and de RESENDE, 2019). Garlic plants have narrow and elongated leaves (FILGUEIRA, 2008). In general, garlic bulbs receive good prices, which suggested that growers could consider them as a suitable candidate to be included in intercropping systems.
Although intercropping garlic in strawberry fields has been successfully used for the management of arthropod pests, twospotted spider mite (TSSM) Tetranychus urticae Koch (Acari: Tetranychidae) (HATA et al., 2016) and Neopamera bilobata Say (Hemiptera: Rhyparochromidae) (HATA et al., 2018), we did not find reports of studies regarding the feasibility of intercropping in terms of the yields of the two crops. Since the maximization of land use efficiency may be achieved by using intercropping (SINGH et al., 2018), we hypothesized that this would be possible for strawberry + garlic designs.
The objective of the study was to evaluate the strawberry pseudofruit and garlic bulb productions in monocropping and intercropping systems. Assessments of garlic and strawberry yields and calculation of the land equivalent ratio (LER), competition ratio (CR) and gross income (GI) indexes were performed.

MATERIALS AND METHODS
The experiments were conducted in three areas. In area I, the experiment was conducted in open field beds in Warta (District of Londrina municipality), Paraná (23°12'40.6"S, 51°12'16.4"W; 580 m.) in the area of Eloi Müller, a traditional strawberry grower in the region. In the area II, the experiment conducted in a greenhouse located at Universidade Estadual de Londrina (UEL) (23°19'44.5"S, 51°12'17.3"W; 585 m.) with the plants grown in plastic pots (7 L, top diameter: 27 cm, bottom diameter: 19 cm and pot height: 22 cm) filled with soil. In area III, the experiment conducted in open field beds at the UEL experimental farm in Londrina municipality (23°20'28.1"S, 51°12'34"W; 547 m.). The climate type was Cfa (Köppen classification), and the soil was classified as red ferralsol (EMBRAPA, 2018), with clay texture in all areas of the study.
The Albion and Camarosa seedlings were purchased from a commercial nursery and transplanted on March 10 and April 7, 2015, for areas I and III, respectively. At the moment of transplanting the stolons were present with abundant rizomes and only the new leaf from crown were kept. A double line spacing of 0.35 x 0.35 m was used. Garlic (BRS Hozan and Cateto cultivars) was planted on April 2 and 28, respectively, for areas I and III (spacing was 0.10 m between plants and 0.35 m between rows). Each plot consisted of eight strawberry plants or eight garlic plants in monocrop or strawberry + garlic intercrops. For areas I and III, the treatments were as follows: monocrop of garlic or strawberry or strawberry (S) + one (S+1GR), two (S+2GR) or three (S+3GR) garlic rows (Figure 1 A, B, C and D).
For area II, Albion seedlings were purchased from a commercial nursery and transplanted on March 10, 2015. Garlic (BRS Hozan) was planted on April 8. At the moment of transplanting the stolons were present with abundant rizomes and only the new leaf from crown were kept. The plot consisted of two strawberry plants per pot. The treatments were as follows: monocrop of garlic (two plants per pot), monocrop of strawberry or strawberry + two (S+2GPP), four (S+4GPP) or five (S+5GPP) garlic plants per plot ( Figure 2). This design was determined to simulate the density of the garlic plants in the one, two or three rows of garlic + strawberry intercropping fields, respectively.
Soil fertilization, fertigation, and pest and disease management were carried out according to the technical recommendations for strawberry crops (RONQUE, 2010). For area I, the grower management was realized. For area II and III, organic farming management was used (Rule 10.831/2003 and inputs allowed by Normative proceeding 46/2011 and Normative proceeding 17/2014).
Strawberry harvesting was performed three times per week to determine the mass of the commercial pseudofruits (perfect or with slight defects) (PBMH & PIMO, 2009). The noncommercial pseudofruits (with serious defects) were discarded. The garlic bulbs were harvested when the leaves showed signs of senescence.
The competition ratio (CR) was calculated using the following formula (2)  (2) Where Pgs = yield of garlic (kg/ha) intercropped with strawberry; Pg = yield of garlic (kg/ha) in monocrop; Psg = yield of strawberry (kg/ ha) intercropped with garlic; Ps = yield of strawberry (kg/ha) in monocrop; Fg = frequency of garlic intercropped with strawberry; and Fs = frequency of strawberry intercropped with garlic.
The financial indicator of gross income (GI) was also calculated using the following formula (3). GI = ∑ (Pi × Qi) (3) Where Pi= price (US$) and Qi= production. Prices were obtained from the Ceagesp distribution center (www.ceagesp.gov.br), the greatest in Brazil. Mean market prices were collected from October 2014 to October 2017. At the moment of the prices survey the conversion of 1 Dollar to Brazilian Real was R$ 3.22. We chose this indicator because only garlic seed bulbs were included as an additional input in the intercropping designs, and growers, in general, produce their own seed bulbs.
A completely randomized block design with five replicates for areas I and II and with four replicates for area III was used. The data were submitted to a homoscedasticity test (Hartley's F test) and normality test (Shapiro-Wilk test). Thereafter, analysis of variance was performed, and the means were compared with Tukey's test (p<0.05). Data was not transformed. Data from CR were compared between garlic and strawberry to know what plant were the most competitive.

Results of greenhouse and open field
studies showed that there were no differences between of strawberry or garlic yields among the treatments in the three growing areas ( Intercrop LER indexes higher than one were observed (Table 2), which means that intercropping production (taking in account bulb production + pseudofruit production) is higher than monocropping (bulb or pseudofruit in sole production, monocrop), in the same area. The values ranged from 1.34 (S+2GPP, area II) to 2.55 (S+3GR, area III). In areas I and III, the LER with the S+3GR treatment was higher than that with the other treatments (F = 14.96 and 24.57, p valor<0.01, for areas I and III, respectively). For area II, higher LER indexes were observed with the S+4GPP or S+5GPP treatments (F = 13.61; p<0.01) than with S+2GPP. The CR showed how much the plant is more competitive than other. Values were similar among treatments (Table 3). In most cases, the CR indexes showed that the strawberry plants had a higher competition potential compared to the garlic plants (F = 9.31, 14.64, 33.58, p valor<0.01, respectively, for S+1, 2 or 3GR, area I); (F = 20.72, p valor<0.05; 18.04, p valor<0.01, respectively for S+4 or 5GPP, area II); (Table 3). The CR indexes for the garlic plants ranged from 0.28 (S + 2GR, area III) to 0.57 (S + 2 or 5GPP, area II). For the strawberry plants, the CR indexes ranged from 1.82 (S+5GPP, area II) to 3.70 (S+2GR, area III).

DISCUSSION
Our results showed that intercropping garlic and strawberry did not reduce both crops yield, therefore, improving land equivalent ratio and gross income to farmers. Previous studies have shown that the average weight of the Hozan garlic variety bulbs in monocrop ranged from 7.60 g (30 Table 1 -Means of garlic bulbs and strawberry pseudofruits yield (g) per plant, on three intercropping designs (densities of garlic intercropped with strawberry) and strawberry or garlic monocrops. Londrina, 2017.   days of vernalization) to 17.88 g (non-vernalized bulbs) (LUCENA et al., 2016). The previously reported average bulb mass for this variety was 25.5 g in southeastern Brazil (BIESDORF et al., 2015). In the present study, the average mass of this variety of garlic bulbs varied from 22.06 to 33.30 g, which was above the averages reported previously. However, the bulbs were weighed immediately after harvest without a curing process, while in previous studies, a curing process of 7 (LUCENA et al., 2016) or 25 days (BIESDORF et al., 2015) was carried out, which may have reduced the mass of the bulbs (3 to 10% reduction in bulb weight) (LIMA & RESENDE, 2007). The yield of the Albion variety of strawberry was similar to that obtained in a previous monocrop study in Dois Vizinhos, PR, County, in which values ranged from 319.50 to 386.50 g per plant (MAZARO et al., 2013) and were inferior compared to that obtained in Guarapuava in first cycle ( Intercropping did not significantly reduce the yields of both crops. Similar results were previously observed for strawberry -lettuce, onion or radish intercrops (KARLIDAG & YILDIRIM, 2009), in which the strawberry plants had similar yields in monocrop (422 and 375 g per plant, for first and second cycle, respectively) and in strawberry-onion intercropping in two production cycles (405 and 386 g per plant, for first and second cycle, respectively). Our results also corroborated with previous studies in which a LER index above 1.90 was reported for the strawberry-onion intercropping (KARLIDAG & YILDIRIM, 2009). In addition, the lettuce-onion intercropping also showed a LER index higher than 1.0, between 1.84 and 1.89, but the head diameter, fresh mass, and number of lettuce leaves were not altered by intercropping (KOEFENDER et al., 2016).
Intercropping with Amaryllidaceae family plants apparently does not reduce the yields of the strawberry crop. Both garlic, as observed in the present study, and onion have agronomic characteristics that may not negatively influence strawberry in intercropping. Leaves of garlic and onion plants are filiform and partially shade the strawberry plants.
Although, in general, both strawberry and garlic crops are described as highly demanding of soil fertility (FILGUEIRA, 2008), the fertilizers provided for the monocrop were also enough for both crops (similar yields to monocrops), which suggested that nutrients were efficiently used.
The higher strawberry CR index was triggered by early planting (22, 28 and 21 days, for areas I, II and III, respectively) in relation to the   planting time of the garlic plants. In a previous study with a garlic-peas intercropping system, the garlic plants also presented lower competitiveness, and the authors also found a comparable CR index (0.36) (ANJUM et al., 2015) to that in the present study. On other study, garlic plants showed a higher CR than eggplant (between 1.02 and 1.82) without causing a decrease in eggplant yield (ISLAM et al., 2016). Apparently, garlic plants initially develop faster than eggplants, which allowed their higher competitiveness. The higher gross income in intercropping designs comes mainly from the higher density of garlic cultivation which provided a higher biomass production on the same area, and; consequently, greater income. For example, in area I the gross income from garlic in S+2GR treatment was higher than monocrop (USD 15,777 and 8,287, respectively, Table 4) even with lower garlic bulb production in S+2GR treatment (31.70 g per plant) versus garlic monocrop (33.30 g per plant) ( Table 1). The same occurred in other production areas.
The garlic yields were not affected by competition and the production of the main crop (strawberry) was not reduced. In addition, a LER index above one was obtained for the intercropping system, which indicated that there is greater efficiency in the use of land than with monocrops. Garlic was initially proposed and succeed as an intercropping plant for pest reduction in strawberry crops (HATA et al., 2016;HATA et al., 2018) and may provide an additional source of income without increased inputs (except garlic bulbs seeds). To produce garlic in a strawberry intercropping system, the same crop management was used. There was also no increase in expenses for soil preparation, control of weeds, etc. As suggested, intercropping schemes may be particularly suitable for organic farmers that have limitations on using pesticides in their crops.
In summary, there were no statistically significant changes in strawberry yields when intercropping garlic in this crop; the garlic yields were not affected by strawberry; the strawberry-garlic intercropping provided higher land equivalent ratio than the monocrops; and the gross income was higher from intercropping than from strawberry monocropping.