Increasing Productivity with Intercropping Systems in Cabbage Production

Journal of Sustainable Agriculture

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Ismail Guvenc & Ertan Yildirim

To cite this article: Ismail Guvenc & Ertan Yildirim (2006) Increasing Productivity with Intercropping Systems in Cabbage Production, Journal of Sustainable Agriculture, 28:4, 29-44, DOI: 10.1300/J064v28n04_04

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Download by: [University of California, Berkeley] Date: 06 November 2015, At: 13:02 Increasing Productivity with Intercropping Systems in Cabbage Production

Ismail Guvenc Ertan Yildirim

ABSTRACT. This study was carried out to determine the effect of different intercropping systems on growth, mineral contents and yield of cabbage (Brassica oleracea L. var. capitata) under field conditions in 2000, 2001 and 2002. LER (Land Equivalent Ratio) and economic net income of different cropping systems based on cabbage as an index of intercropping efficiency were also evaluated. In the study, cabbage was used as a main crop, and cos lettuce (Lactuca sativa L. var. longifoila), leaf lettuce (Lactuca sativa L. var. crispa), radish (Raphanus sativus L.), onion (Allium cepa L.) and snap bean (Phaseolus vulgarism L. var. nanus) were used as intercrops. Each of the intercrops was planted in between cabbage rows in separate plots. Cabbage and all intercrops were also grown as sole crops. There was no significant effect of different intercropping systems on growth characteristics and yield of cabbage compared with sole cabbage cropping except for radish as an intercrop, which affected adversely the yield and some growth characteristics of cabbage. Net income was increased significantly when cabbage was intercropped with cos lettuce, bean, leaf lettuce or onion. The values of

Ismail Guvenc is affiliated with Department of Horticulture, Faculty of Agriculture, Atatürk University, Erzurum, Turkey (E-mail: [email protected]). Ertan Yildirim is affiliated with Ispir Hamza Polat Vocational Training School, Atatürk University, 25900, Ispir, Erzurum, Turkey (E-mail: [email protected]). Address correspondence to: Ertan Yildirim at the above address. The authors wish to thank Prof. Fahri Yavuz, Agricultural Economics Department, Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Atatürk University, for his assistance in the economic analysis of the study and to the anonymous reviewer(s) for valuable comments on the paper. The authors are very grateful to The Atatürk University, Scientific Research Projects Foundation, for their generous financial support (Project Number 2000/88). Journal of Sustainable Agriculture, Vol. 28(4) 2006 Available online at http://jsa.haworthpress.com © 2006 by The Haworth Press, Inc. All rights reserved. doi:10.1300/J064v28n04_04 29 30 JOURNAL OF SUSTAINABLE AGRICULTURE

LER appeared to be greater than 1 under intercropping systems. Cropping systems did not significantly affect nitrogen, phosphorus, potassium, calcium, magnesium and iron content of cabbage. The results obtained in this study pointed out that intercropping systems based on cabbage might increase total yield, productivity and profitability. doi:10.1300/ J064v28n04_04 [Article copies available for a fee from The Haworth Document Delivery Service: 1-800- HAWORTH. E-mail address: Website: © 2006 by The Haworth Press, Inc. All rights reserved.]

KEYWORDS. Cabbage, income, intercropping, land equivalent ratio (LER), yield

INTRODUCTION

Sustaining yield and income is a more important objective for farmers with limited resources than maximizing either yield or income. Addition- ally, the family objectives include maintaining food supply and income through the year, minimizing risk of failure in every season, keeping cash costs at a minimum, and meeting other social obligations in the com- munity (Fukai and Midmore, 1993). The improvement of agricultural sustainability favors the maintenance of the intercropping systems. In- tercropping is an efficient soil conservation practice due to the increased ground cover that it provides, as well as the exploitation of different soil layers due to the different depth of the root systems of the two species (Zimmermann, 1996; Jarenyama et al., 2000). Intercropping, through more effective use of water, nutrients and solar energy, can significantly enhance crop productivity compared with the growth of sole crops (Midmore, 1993). Many studies have indicated that intercropping with different vegetables was more productive and profitable than sole cropping because of the complementary effects of intercrops (Brown et al., 1985; Olasantan, 1991; Costa and Perera, 1998; Varghese, 2000; Baumann et al.,

Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 2001; Yildirim and Guvenc, 2005). The majority of farmers in developing countries practice intercropping. In developed countries, mechanization made intercropping inconve- nient, leading to its abandonment. However, recent studies indicate that intercropping may be compatible with mechanized agriculture and could provide an alternative to monocropping, especially for small, resource- poor farms (Itulya et al., 1997). Guvenc and Yildirim (1999) reported that intercropping is a safer and more stable system of agricultural pro- Research, Reviews, Practices, Policy and Technology 31

duction than sole cropping for small farms, where capital is limited and labor is available. Furthermore, intercropping has a great potential for pest and disease reduction (Theunissen, 1994, 1997; Theunissen and Schelling, 1996; Baumann et al., 2000). Studies have affirmed the util- ity of intercropping as one of the crop contingency strategies against any monocultured crop failure. Intercropping has been acclaimed inter- nationally as the most reliable approach to safeguard the sustainability of vegetable production (Coolman and Hoyt, 1993). Cabbage is grown widely in Turkey with a total annual production of 610,000 tons in 32,000 ha of area (Anonymous, 2003). According to a rat- ing system considering total yield per unit area, price per unit weight harvested and the time required between seeding and harvest, cabbage is not a space-efficient crop and usually may not return a higher monetary value for the space occupied as compared with some vegetable crops (Splittstoesser, 1990). Cabbage is a relatively long-season crop and long-season crops in the first growth stage can be slow to grow and establish a full canopy, opening an opportunity for a short-season crop to be grown between rows (Fukai and Trenbath, 1993). Solar radiation, water and some nutrients that would be otherwise wasted during early growth stages of long-term crops can be utilized by an associated crop growing between the rows (Midmore, 1993). Although advantages of intercropping systems such as cabbage: bean (Gliessman and Altieri, 1982; Poniedzialek et al., 1989; Poniedzialek and Kunicki, 1995) and cabbage:broad bean (Vicia faba) (Sharma et al., 1988) have been demonstrated in earlier studies, there is no information on cabbage intercropping with cos lettuce, leaf lettuce and onion. To maintain yield and quality in intercropping systems, complementarities in patterns of resource use must be taken into account. Cultivars suitable for intercropping should enhance the complementary effects between species (Baumann et al., 2001). According to the latest available statistics, the vegetable production area in Turkey is 800,000 ha with a total production of 22 million tons with an average of 27 tons/ha approximately. In Northeast Turkey, suitable areas for crop production are limited, and average productivity of

Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 vegetables is approximately 14-15 tons/ha, which is lower than the national average productivity of vegetable (Anonymous, 2003). The improvement of vegetable production through suitable intercrop combinations has not yet been exploited to its full potential in Turkey. This study was aimed at optimizing cabbage production in mixture by choosing suitable intercrops and evaluating the sustainability of cabbage intercropping systems on the basis of yield, LER and economic net income. 32 JOURNAL OF SUSTAINABLE AGRICULTURE

MATERIALS AND METHODS

This study was conducted under field conditions at Atatürk Univer- sity, Hamza Polat Vocational School, in Upper Coruh Valley (Ispir) in Turkey in 2000, 2001 and 2002. Ispir is located at 40° 29Ј N latitude 41° 01ЈE longitude, 1200 m above sea level. It had 136, 280 and 306 mm of a total rainfall and had 19.1°C, 19.3°C and 17.6°C of average air temper- ature in 2000, 2001 and 2002, respectively (April to September). Some soil physical and chemical properties of the experimental area are presented in Table 1. Manure (30 t/ha) was applied to plots in previous Oc- tober for each experiment year. The manure used contained 1.1% N, Ϫ1 1.2% K2O, 1.6 P2O5, and EC of 6.2 dS m . Chemical fertilizer was used at the rate of 180 kg/ha N (as ammonium nitrate) and 100 kg/ha P2O5 (as triple super phosphate) and broadcast uniformly on the soil surface prior to planting and incorporated. Cabbage “Zohrap” as main crop was intercropped with cos lettuce “Yedikule 44”, leaf lettuce “Iri Kivircik”, radish “Cherry Belle”, onion “Corum” and snap bean “Gina”. A randomized complete block design was employed as the experimental design with three replications. Treat- ments consisted of cabbage alone, cabbage:bean, cabbage:cos lettuce, cabbage:leaf lettuce, cabbage:radish, cabbage:onion, and all intercrops as sole crops. Plot size was 4.5 m ϫ 3.75 m. Cabbage spacing was 75 cm ϫ 75 cm (Padem, 1986) in both sole cropping and intercropping. In intercropping treatments, one row of cos and leaf lettuce (within-row plant spacing 30 cm), radish (within-row plant spacing 5 cm), onion (within- row plant spacing 5 cm) or bean (within-row plant spacing 20 cm) was TABLE 1. Experimental area soil physical and chemical properties.

Parameters Year

2000 2001 2002 Texture Sandy loam Sandy loam Sandy loam Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Sand (%) 68.4 64.9 65.3 Silt (%) 19.9 28.0 21.6 Clay (%) 11.7 7.1 13.1 pH 6.7 6.7 7.1 Organic matter (%) 1.4 1.9 1.6

Available P2O5 (kg/ha) 13.0 35.0 21.0 Exchangeable K (meq/100 g) 2.3 3.5 2.0 Research, Reviews, Practices, Policy and Technology 33

planted in between cabbage rows. Seedlings for cabbage, cos lettuce and leaf lettuce were transplanted. Seeds for bean and radish were sown, and sets (approximately 1-1.5 cm diameter) for onion were planted. Main crop and intercrops were planted simultaneously on May 15 in 2000, on May 18 in 2001 and on May 15 in 2002. Sprinkler irrigation was used. A total of 25-30 irrigations were applied during the entire growth period to replace water lost through evapotranspiration, at intervals of 5-7 days. Weeds were controlled manually. Insecticide was applied to avoid crop damage by cabbage worms (Pieris rapea L.). The crops tested were harvested when they reached marketable size and quality. Non-wrapped leaf number and weight per plant, head diameter, head height, head weight and yield for cabbage were determined after harvest. Furthermore, some growth parameters (data not shown) and yield for cos lettuce, leaf lettuce, onion, bean and radish were determined. All observations were made from centre rows after border rows were discarded to avoid edge effects. The harvest dates of crops are presented in Table 2. Chemical analyses were performed after harvest. Samples were taken from leaves of five cabbage plants from the centre of each plot. The plant materials consisted of leaves 7, 8, 9 and 10 from outer to inner. Leaves weredriedinanovenat70°C until a constant mass was reached and then they were ground for chemical analysis (Dean and Herron, 1981; Berard, 1990). Total nitrogen was determined using the micro-Kjeldahl method (Kacar, 1972). After plant samples were wet-fired with nitric-perchloric acid, P was determined spectrophotometrically. K, Ca, Mg and Fe contents

TABLE 2. The harvest dates of cabbage, cos lettuce, leaf lettuce, radish, onion and bean in 2000, 2001 and 2002.

Crops Harvest dates

2000 2001 2002 Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Cabbage September 20 September 30 September 27 Cos lettuce July 09 July 13 July 15 Leaf lettuce June 21 June 23 June 23 Radish June 20 June 23 June 25 Onion June 20 June 28 June 25 Bean June 28-August 24 June 27-August 25 June 25-August 22 34 JOURNAL OF SUSTAINABLE AGRICULTURE

were determined using an atomic adsorption spectrophotometer (Kacar, 1972; Frank, 1975). The efficiency of intercropping was evaluated by the land equivalent ratio (LER) and economic net income. LER has often been considered to be an index of intercropping advantage. The LER is defined as fol- lows: LER ϭ LAϩLB = AI/AS ϩ BI/BS, where LA and LB are the individual LERs of two crops A and B. LA is obtained by dividing the yield of crop A in intercropping (AI) by the yield of the same crop in sole cropping (AS). LB is calculated in the same way (Vander- meer, 1989). Economic net income analysis was undertaken to assess economic feasibility of different intercropping systems. Cost of land, buildings and equipment was not included, as it was assumed to be the same for all systems. Materials included fertilizer, seeds, plant trays, crates, etc. La- bor included family and unskilled hired labor. Machine operating costs were also considered (Brown et al., 1985). Crop prices were obtained from State Institute of Statistics Prime Ministry Republic of Turkey (Anonymous, 2001, 2002, 2003). Data obtained in this study were subjected to analysis of variance (ANOVA) and the differences between means were tested according to Duncan’s Multiple Range Test.

RESULTS AND DISCUSSION

Growth

Different intercropping systems did not affect the non- wrapped leaf number and weight per plant of cabbage compared with sole cabbage cropping (Table 3). Cabbage head diameter, height and weight were each significantly lower in cabbage:radish plots as compared with cabbage alone in two out of three years. Only in 2002 were all three parameters significantly affected (Table 3). These results supported those of

Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Sharma et al. (1988) and Varghese (2000) who reported that some growth characteristics of cabbage were affected adversely when it was intercropped with radish. There were no statistical differences between cropping systems in terms of head diameter, head height and head weight when cabbage was intercropped with cos lettuce, leaf lettuce, onion and bean. Our findings were concordant with those of Sharaiha and Haddad (1985) in cabbage:bean, Sharma et al. (1988) in cabbage:broad bean and Varghese Research, Reviews, Practices, Policy and Technology 35

TABLE 3. Effect of different intercropping systems on cabbage growth characteristics.

Cropping System Leafy Number Leaf y Head Diameter Head Height Head (per Plant) Weight (cm) (cm) Weight (kg/Plant) (kg/plant)

2000 Cabbage:cos lettuce 16.2 NS 2.7 NS 29.3 az 23.4 NS 6.8 abz Cabbage:leaf lettuce 16.1 2.8 29.7 a 23.9 7.1 a Cabbage:onion 16.1 2.8 29.3 a 23.7 6.9 a Cabbage:radish 15.7 2.7 26.6 b 23.0 6.4 b Cabbage:bean 16.8 2.8 29.7 a 23.1 7.0 a Cabbage sole 16.4 2.8 31.1 a 24.1 7.0 a 2001 Cabbage:cos lettuce 16.4 NS 2.8 NS 28.7 NS 26.4 abz 7.0 NS Cabbage:leaf lettuce 15.8 2.9 29.6 26.9 a 7.1 Cabbage:onion 16.8 2.8 29.4 28.0 a 7.1 Cabbage:radish 15.5 2.7 28.5 24.7 b 6.8 Cabbage:bean 17.0 2.8 29.3 26.7 a 7.1 Cabbage sole 16.6 2.8 29.9 26.6 ab 7.1 2002 Cabbage:cos lettuce 16.6 NS 2.6 NS 27.6 abz 26.2 az 6.9 az Cabbage:leaf lettuce 16.5 2.6 28.7 a 26.5 a 7.2 a Cabbage:onion 16.2 2.6 27.9 ab 25.6 a 7.1 a Cabbage:radish 16.3 2.6 25.7 b 22.1 b 6.3 b Cabbage:bean 16.5 2.7 28.5 a 26.4 a 7.0 a Cabbage sole 16.8 2.7 28.9 a 26.5 a 7.2 a

yLeaves were non-wrapped. zNumbers with the same letters are not statistically different according to Duncan’s Multiple Range Test (p Ͻ 0.05). NS: Non-Significant. Downloaded by [University of California, Berkeley] at 13:02 06 November 2015

(2000) in cabbage:sorrel. All these studies found that intercropping with some vegetables had no adverse effects on some growth characteristics of cabbage. These findings might be attributed to early-maturing crops not interfering with the growth of the late-maturing ones in intercropping systems (Splitstoesser, 1990). 36 JOURNAL OF SUSTAINABLE AGRICULTURE

Nutrient Concentration

Concentrations of N, P, K, Ca, Mg and Fe in leaves of intercropped cabbage compared with the sole cabbage cropping were not significantly different in 2000, 2001 and 2002 (Table 4). Varghese (2000) in cabbage, Santos et al. (2002) in broccoli and Yildirim and Guvenc (2005) in cauliflower found that the nutrient concentrations of leaves of crops grown in intercropping systems were similar to the sole cropping ones, explaining this phenomenon by the efficient use of available resources per unit area for different crops. Intercropping systems have been determined to have higher nutrient uptake per area than sole cropping because the root growth of component species with different root

TABLE 4. Effect of different intercropping systems on cabbage nutrient contents.

Cropping System N (%) P (%) K (%) Ca (%) Mg (%) Fe (ppm) 2000 Cabbage:cos lettuce 3.38 NS 0.31 NS 2.80 NS 0.67 NS 0.26 NS 65 NS Cabbage:leaf lettuce 3.50 0.32 2.71 0.70 0.27 73 Cabbage:onion 3.47 0.31 3.05 0.71 0.24 67 Cabbage:radish 3.62 0.37 2.73 0.68 0.25 71 Cabbage:bean 3.71 0.30 2.95 0.67 0.27 75 Cabbage sole 3.56 0.37 2.90 0.75 0.28 74 2001 Cabbage:cos lettuce 3.87 NS 0.34 NS 2.75 NS 0.50 NS 0.17 NS 64 NS Cabbage:leaf lettuce 4.14 0.34 2.72 0.54 0.23 62 Cabbage:onion 4.10 0.33 2.62 0.56 0.20 62 Cabbage:radish 4.21 0.34 2.84 0.51 0.16 67 Cabbage:bean 4.18 0.33 2.74 0.50 0.18 65 Cabbage sole 4.15 0.38 2.84 0.55 0.24 62 2002 Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Cabbage:cos lettuce 3.71 NS 0.28 NS 3.05 NS 0.59 NS 0.20 NS 78 NS Cabbage:leaf lettuce 3.81 0.28 3.00 0.60 0.21 72 Cabbage:onion 3.81 0.27 3.16 0.53 0.20 80 Cabbage:radish 3.75 0.27 3.01 0.59 0.18 75 Cabbage:bean 3.82 0.32 3.19 0.54 0.22 77 Cabbage sole 3.90 0.29 3.13 0.57 0.19 77

NS: Non-Significant. Research, Reviews, Practices, Policy and Technology 37

properties explores a larger soil mass (Francis, 1989; Woolley and Davis, 1991; Morris and Garrity, 1993). Furthermore, intercropping systems may have higher nutrient use efficiency, due to potential differences in time of peak demand for different nutrient elements by compo- nents in the mixture (Francis, 1989; Midmore, 1993). In this study, intercropping systems with different root properties of the component crops could have increased nutrient use efficiency and exploited more nutrients.

Yield

In 2000 and 2002, the yield of cabbage intercropped with radish compared with sole cabbage cropping decreased significantly (Table 5). Earlier studies have showed that radish with allelopathic root exudates had the greatest effect in reducing the yield of cabbage (Sharma et al., 1988; Varghese et al., 1990; Varghese, 2000), who investigated cabbage: radish intercropping system. Radish plants may release into the rhizosphere some allelopathic chemicals such as glucosinolate, thio- cyanate in sufficient quantities from their roots to effect neighbouring plants. The decay process of the waste of radish plants can also release toxic chemicals, which inhibit the growth of component or future crops (Omar et al., 1989; Silva, 1997; Kocacaliskan, 2001). There were no significant differences between the cropping systems in terms of yields of cabbage intercropped with cos lettuce, leaf lettuce, onion and bean in all the years (Table 3). Similar findings were obtained for tomato: cabbage (Brown et al., 1985), chilli:onion (Natarjan, 1992), broccoli: lettuce (Gliessman, 1998) and cabbage:sorrel (Varghese, 2000) intercropping systems. The data obtained in this study also concurred with those of Poniedzialek et al. (1989), Sharma et al. (1988), Poniedzialek and Kunicki (1995) for cabbage:bean; Subhan (1991) for tomato:bean and of Itulya et al. (1997) for collard:cowpea intercropping systems. Woolley and Davis (1991) reported that legumes such as bean were weaker competitors for growth resources than some other vegetables.

Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Furthermore, intercropping with a legume can improve N-use (Zhou et al., 2000) and the legume can release biologically fixed N to the non-legume (Singh et al., 1986; Ofori and Stern, 1987; van Kessel and Hartley, 2000). The yields are presented for each intercrop in both monocropping and intercropping in Table 6. The yield response of intercrops to intercropping was significant; intercropping with cabbage significantly decreased the yield of intercrops all three years. The depression in the 38 JOURNAL OF SUSTAINABLE AGRICULTURE

TABLE 5. Yield of cabbage in response to various intercropping systems.

Cropping System Total Yield (kg/m2)

2000 2001 2002 Cabbage:cos lettuce 12.1 abz 12.5 NS 12.2 az Cabbage:leaf lettuce 12.6 a 12.6 12.8 a Cabbage:onion 12.3 a 12.6 12.6 a Cabbage:radish 11.4 b 12.1 11.2 b Cabbage:bean 12.5 a 12.6 12.4 a Cabbage sole 12.5 a 12.6 12.8 a

zNumbers with the same letters are not statistically different according to Duncan’s Multiple Range Test (p Ͻ 0.05). NS: Non-Significant.

yields of the intercrops per unit area was especially caused by fewer plant numbers of intercrops in intercropping than monocropping of intercrops. These results were confirmed by Yildirim and Guvenc (2005) who showed that intercropping with cauliflower decreased the yield of cos lettuce, leaf lettuce, radish, onion and bean. Splittstoesser (1990) pointed out that short-season vegetables such as lettuce planted between full season vegetables for complementary depth and spread of root systems preclude serious competition for light, water and nutrients. It was also reported that long-season crops such as cabbage, might take full advantage of all available resources to complete their growth after intercrops have been harvested. Also, the long-season crop can grow slowly in the first half of the growing season and establishes a full canopy only after several weeks, opening an opportunity for a short-term crop to be grown between rows (Fukai and Trenbath, 1993). In our study, the establishment period of cabbage was much longer than that of cos lettuce, leaf lettuce, radish, onion and bean; therefore, our results support the previous reports. Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Land Equivalent Ratio and Economic Net Income as Intercropping Efficiency

LER values in this study were always greater than 1 in the intercropping systems (Table 7), which indicates productivity gains and the efficiency of land and resource use of these systems over the sole cropping system (Fukai, 1993). The highest LER values in all years were Research, Reviews, Practices, Policy and Technology 39

TABLE 6. Effect of intercropping with cabbage on yield of bean, cos lettuce, leaf lettuce, onion and radish (kg/m2)

Cropping System Bean Cos Lettuce Leaf Lettuce Onion Radish 2000 Sole 2.48 az 7.14 az 1.20 az 3.62 az 2.77 az With cabbage 0.69 b 1.82 b 0.40 b 0.63 b 0.43 b 2001 Sole 2.74 az 7.27 az 1.25 az 3.94 az 3.11 az With cabbage 0.77 b 2.03 b 0.43 b 0.78 b 0.50 b 2002 Sole 2.65 az 7.41 az 1.22 az 3.75 az 3.14 az With cabbage 0.77 b 2.07 b 0.41 b 0.71 b 0.56 b

zMean separation within columns by Duncan’s Multiple Range Test (p Ͻ 0.05).

obtained in cabbage:leaf lettuce intercropping system (1.34), whereas the lowest values occurred in cabbage:radish intercropping system (1.06, 1.13 and 1.06 in 2000, 2001 and 2002, respectively). LER values were affected by crop combinations and these effects were consistent all three years. These findings support those of Olasantan (1991), Sharaiha and Gliessman (1992), Sharaiha and Hattar (1993), Muoneke and Asiegbu (1997), Varghese (2000), Baumann et al. (2001) and Santos et al. (2002), who investigated the efficiency of intercropping over sole cropping in different vegetable combinations. This efficiency might be attributed to the more efficient use of available resources per unit area particularly when manure and water were provided in adequate quantities (Sharaiha and Hattar, 1993). Moreover, it was reported that LER values in intercropping systems are likely to be >1 especially when their component crops differ greatly in growth duration so that their maxi- mum requirements for growth resources occur at different times (Fukai and Trenbath, 1993). In this study, the differences of growth rhythm, time of maturity, morphological characteristics or resource use of main Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 and intercrops might have reduced or postponed competition between component crops because of complementary effects of intercrops. Economic analyses were performed on the basis of prices and vari- able costs, which included labor but not cost of land. The most economi- cal and satisfactory intercropping system was obtained with cabbage: cos lettuce in all years in this study (Table 7). All intercropping systems used in the study gave a better economic net income than sole cabbage 40 JOURNAL OF SUSTAINABLE AGRICULTURE

cropping system except for cabbage:radish intercropping system in 2000. Willey (1979) reported that the practical significance of LER could only be fully assessed when related to the actual economic yield. Muoneke and Asiegbu (1997) concluded that the highest LER values did not always reflect highest monetary return to the farmer. The sustainability of any production system is influenced by the economic returns, which determine the commercial feasibility of different intercropping systems. It has been pointed out by Prabhakar and Shukla (1990), Fukai (1993), Varghese (2000), Santos et al. (2002) and Yildirim and Guvenc (2005) that intercropping could result in an increase in the productivity of vegetables per unit area, and increase in profitability.

TABLE 7. Land Equivalent Ratios (LERs) and net income of different cropping systems based on cabbage.

Cropping System Land Equivalent Ratio Net Income (E/ha)z 2000 Cabbage sole 1.00 10628 d Cabbage:bean 1.28 12135 b Cabbage:cos lettuce 1.22 14406 a Cabbage:leaf lettuce 1.34 11625 d Cabbage:onion 1.15 11406 d Cabbage:radish 1.06 10017 e 2001 Cabbage sole 1.00 5121 d Cabbage:bean 1.28 5672 c Cabbage:cos lettuce 1.27 6885 a Cabbage:leaf lettuce 1.34 5617 c Cabbage:onion 1.20 5927 b Cabbage:radish 1.13 5541 c 2002 Cabbage sole 1.00 6966 e

Downloaded by [University of California, Berkeley] at 13:02 06 November 2015 Cabbage:bean 1.26 8230 c Cabbage:cos lettuce 1.23 9990 a Cabbage:leaf lettuce 1.34 8150 c Cabbage:onion 1.17 8600 b Cabbage:radish 1.06 7537 d

zNumbers with the same letters are not statistically different according to Duncan’s Multiple Range Test (p Ͻ 0.05) Research, Reviews, Practices, Policy and Technology 41

The results obtained in this study in terms of economic income were in agreement with the previous studies.

CONCLUSION

The present study showed that intercropping systems based on cabbage were more productive and profitable and had the higher use efficiency of land and resource than sole cabbage cropping. The study showed that intercropping did not adversely affect the yield of cabbage but, on the contrary, produced additional yield from intercrops such as bean, cos lettuce, onion and leaf lettuce. However, radish as an intercrop affected adversely the growth and yield of cabbage. The highest LER value was realized from cabbage:leaf lettuce, but the greatest economic net income was realized from the cabbage:cos lettuce intercropping system. Furthermore, bean, onion and leaf lettuce as an intercrop when grown with cabbage increased the economic net income compared with sole cabbage cropping in all years of the experiment. Data may suggest that small farmers with limited resources could employ these intercropping systems, especially cabbage:cos lettuce, to obtain greater yield efficiency and higher net income and to use their labor and inputs more efficiently.

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