ABSTRACT
Productivity of maize (Zea mays L.) and climbing bean (Phaseolus vulgars L.) intercropping system is affected by fertility status of the soil and population density of component crops. A trial was conducted in 2002 and 2003 cropping season to investigate the effects of inorganic and organic fertilisers and population density on productivity of maize-climbing bean intercropping system. The experiment was laid out as 2x2x2x2 factorial arrangement with two sole cropping in Randomized Complete Block Design with three replications. Nitrogen and population density significantly increased grain yield of climbing bean. FYM significantly affected LER of intercropping system. Grain yield of component crops from intercropping were significantly higher than the monocultures. Yield of intercropping were up to 27 and 403% higher for maize and climbing bean than the yield achieved by growing the crops separately. Partial land equivalent ratio of maize and climbing bean ranged between 0.94 to 1.19 and 0.30 to 0.90, respectively. Higher partial LER of maize indicated the superiority of maize on climbing bean in intercropping. Higher land equivalent ratio was recorded from intercropping than sole planting. Intercropping produced 32 to 98% more yield per unit land area than the component monocultures. Intercropping maize-climbing bean is a viable agronomic practice to produce higher yield from a unit of land.
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DOI: 10.3923/ajps.2005.458.465
URL: https://scialert.net/abstract/?doi=ajps.2005.458.465
INTRODUCTION
High population pressure and scarcity of arable land have been compelled planting of two or more crops on the same pieces of land at the same time. Maize and climbing bean have commonly grow in association in western Oromiya and can be the ideal ones for sustainable production and food security to resource poor farmers. Several reports indicated the greater total productivity per unit of land and more efficient utilization natural resources. Habtamu et al.[1] reported that intercropping of maize-climbing bean showed good compatibility since maintaining almost 80-100% of the sole maize yield. Abdissa and Girma[2] intercropping of maize -climbing bean are advisable because the yield of component crops is optimum and achieved higher LER value. Intercropping of haricot bean under row planted maize was economically better than sole cropping[3]. Nigusse[4] maize intercropped with haricot bean give yield advantage and land use efficiency of 99 and 73%, respectively as compared to sole maize. Thus, intercropping has an immense importance for sustainability of farming system, which is especially true for small-scale resource poor farmers experience of food shortage. Although intercropping has significant advantages to small-scale resource poor farmers no finding was available on fertilizer response of intercropping system.
Nevertheless, very little chemical fertilizers are applied to cereal/legume intercropping system and then only to the main crop, the assumption being that the legume component can fulfil its own requirement[5]. Roy and Barun[6] suggested that supplying the recommended dose of fertilizer to both the component crops could increase the yield of an intercropping system. They further stated that the fertilizer needs of a component crop in a cereal-legume intercropping systems are likely to be very different from the requirements of respective sole crop, which seems logical as two crops grown in association may or may not exploit the growth resources fully. However, currently chemical fertilizers are beyond the reach of farmers due to high price and in accessibility. In contrary, the alternative organic fertilizers can not meet crop nutrient demand over large area because of limited availability, low nutrient composition and high labour requirements. Appropriate plant population of climbing bean has a paramount importance on the yield of component crops. Since, it climbs on the associated crops it could cause lodging when the population density is higher than the optimum. The optimum plant density for sole cropped climbing bean was found to be approximately 12 plants per m2 and six to eight plants per m2 in association with maize and indicated that in maize/ climbing bean intercropping, total intercrop densities for maximum production for component crops are at lower population of climbing bean[7]. Moreover, when intercropped with maize, reducing the density of climbing bean could help[8] as a too high density can pull over the stem of the associated crop resulting in lodging of the whole crop[9]. To date little attention has been given on the amount of fertilizer rate[10] and population density of climbing bean in maize-climbing bean intercropping system. Therefore the objectives this study was to determine the effects of N/P, FYM rate and population density of climbing bean and their interaction on grain yield and LER of maize-climbing bean intercropping system.
MATERIALS AND METHODS
Intercropping maize/climbing bean experiment was conducted from 2002 to 2003 cropping seasons for two years at Bako Agricultural Research Center. The altitude of the area is 1650 m.a.s.l. The long-term (1961-2003) mean annual rainfall at BARC is 1239 mm with unimodal distribution[11]. It has a warm humid climate with the mean minimum, mean maximum and average air temperatures of 13.2, 28 and 21°C, respectively. Sixty percent of the soil (1400 ha), of Bako Research Center, is reddish brown in colour clay and loam in texture[12]. Factorial combinations of two levels of N (46 and 69 kg N ha-1), two levels of P (10 and 20 kg P ha-1) and two levels plant density of climbing bean (one side planting (44,444 plant ha-1) and two side planting (88,888 plant ha-1) to maize) in the maize/climbing bean mixture were tested against the recommended fertilizer rate of sole maize 110/20 kg N/P ha-1 and 18/20 kg N/P ha-1 for sole climbing bean, respectively.
The treatment combinations are:
T1: | 46/10 kg N/ P 4 t FYM ha-1 maize with 1/3* climbing bean population |
T2: | 46/10 kg N/ P 4 t FYM ha-1 maize with 2/3* climbing bean population |
T3: | 46/10 kg N/P 8 t FYM ha-1 maize with 1/3 climbing bean population |
T4: | 46/10 kg N/ P 8 t FYM ha-1 maize with climbing bean population |
T5: | 46/20 kg N/ P 4 t FYM ha-1 maize with 1/3 climbing bean population |
T6: | 46/20 kg N/P 4 t FYM ha-1 maize with 2/3 climbing bean population |
T7: | 46/20 kg N/ P 8 t FYM ha-1 maize with 1/3 climbing bean population |
T8: | 46/20 kg N/ P 8 t FYM ha-1 maize with 2/3 climbing bean population |
T9: | 69/10 kg N/ P 4 t FYM ha-1 maize with 1/3 climbing bean population |
T10: | 69/10 kg N/ P 4 t FYM ha-1 maize with 2/3 climbing bean population |
T11: | 69/10 kg N/ P 8 t FYM ha-1 maize with 1/3 climbing bean population |
T12: | 69/10 kg N/ P 8 t FYM ha-1 maize with 2/3 climbing bean population |
T13: | 69/20 kg N/ P 4 t FYM ha-1 maize with 1/3 climbing bean population |
T14: | 69/20 kg N/ P 4 t FYM ha-1 maize with 2/3 climbing bean population |
T15: | 69/20 kg N/ P 8 t FYM ha-1 maize with 1/3 climbing bean population |
T16: | 69/20 kg N/ P 8 t FYM ha-1 maize with 2/3 climbing bean population |
T17: | 110/20 kg N/ P/ 0 t FYM ha-1 sole maize and |
T18: | 18/20 kg N/ P 0 t FYM ha-1 sole climbing bean. |
The design of the experiment was 2x2x2x2 factorial arrangement Randomized Complete Block Design plus two control treatments in three replications. The total gross plot size was 4.5x5.1 m and 3x5.1 m harvestable plots. The spacing was 75x30 cm for sole maize and 75x10 cm for sole climbing bean. For the intercropping the spacing was 75x30 cm for maize and 75x20 cm for climbing bean in one side planting and 75x20 cm and 75x40 cm for climbing bean for both side planting to maize. The maize variety used was BH-540 and 813-BCB-28 cultivar for climbing bean. The seed rate used was 25 kg ha-1 for maize and 75 kg ha-1 for climbing bean. Sowing dates followed recommended date of planting ranged May 1-30. The planting of maize and climbing bean were simultaneously in the same row. Full dose of phosphorus (as DAP) was applied once at planting, while nitrogen (as urea) was applied in spilt doses, half at planting and the remaining half applied 30 to 40 days after planting. The grain yield of climbing bean and maize was harvested and measured at 10 and 12.5% moisture level, respectively. Land Equivalent Ratio (LER) is the ratio of mixed crop yield to sole yield of both crops. LER indicates the productivity of the intercropping system as compared to sole cropping. The data were analyzed using MSTATC[13] and SAS[14] statistical packages. Mean separation was done using LSD at 5% probability level.
Table 1: | Effects of treatment factors on grain yield and LER of maize and climbing bean in intercropping system in 2002,2003 and combined over years |
*= significant at 5% probability level |
Table 2: | Grain yield, partial LER and LER of intercropping maize-climbing bean as affected by N, P, FYM and population density in 2002,2003 and combined over years |
Ns= non significant at 5% probability level, Pd= population density, 1/3 and 2/3= 44,444 and 88,888 plants ha-1 of climbing bean |
Table 3: | Grain yield, Partial LER and LER of intercropping maize-climbing bean as affected by N, P, FYM and Population density in 2002,2003 and combined over years |
Ns= Non significant at 5% probability level |
*1/3 and 2/3=44,444 and 88,888 plants ha-1 of climbing bean in intercropping system.
RESULTS AND DISCUSSION
Cropping season: Maize grain yields were averaged 6271 kg ha-1, but 7196 and 5347 kg ha-1 in 2002 and 2003 cropping season (Table 2 and 3). Combined yield of climbing bean across years were averaged 985 kg ha-1 but were 21% higher in 2002 cropping season than 2003 (Table 2 and 3). Cropping season significantly affected grain yield of maize and climbing bean. Similarly Tenaw[15] grain yield of maize significantly affected by cropping season. These were attributed due to variation of climatic factors across cropping seasons. This further stated that maize and climbing bean producers should consider the role of environmental factors for yield enhancement. YearxNxP interaction significantly (p<0.05) affected mean grain yield of climbing bean (Table 1). This indicates grain yield of climbing responded variable to N and P fertilizers depending on distribution of rainfall which is in consistence with Tenaw[15].
Grain yield
Climbing bean: Grain yield of climbing bean was significantly (p < 0.05) affected by N, FYM and population density in intercropping system (Table 1 and 2). Climbing bean grain yield was increased 36. 69, 19.60 and 28.80% in 2002, 2003 and combined mean as applied N level increased in intercropped system. This indicated that application of N is essential for climbing bean in intercropping with maize. Similarly Edje et al.[16] nitrogen fixation in dry beans is inadequate as they respond to fertiliser nitrogen up to 200 kg ha-1 in sole cropping. Chui[17] found that intercropping beans with maize responded to N application and increased bean yield by 5%. Islam[18] nitrogen application to legumes would increase the yield of legumes in soils where suitable rhizobia are absent or sparse. However, this result was in contrary with Ahmed and Gunasena[19] the yield of legumes intercropped with maize always decreased with increased rates of N due to high competition from maize since N is liable to competition between intercrops due to its high mobility.
Grain yield of climbing was significantly increased with rate of FYM. Grain yield advantage of 21.64, 46.20 and 32.04% in 2002, 2003 and combined mean was obtained as the rate of applied FYM increased. Grain yield of climbing bean was increased with increased population density of climbing bean in intercropping system which agree with Tesfa et al.[20], Demesew[21] and Willey[22] highest grain yield of haricot bean was obtained when the optimum total plant density is higher than that of either sole crop. This implies that increasing plant population also increases the efficiency of resources utilization. Application influence was non-significant on grain yield of climbing bean intercropped with maize system (Table 1 and 2).
Significant (p<0.05) differences were occurred due to N and P, N and population density and P and FYM interactions on grain yield of climbing bean in 2002 and combined over years (Table 1). Similarly combined use of N/P increased the grain yield of climbing bean. Tesfa et al.[20] and Tolessa et al.[23] the highest average intercrop of haricot bean yield was obtained with 92/10 kg N P ha. Similarly, the interaction effects of N and climbing bean population increased the seed yield of climbing bean as the combination of two factors increased. The results suggest that the application of nitrogen is essential for the production of climbing bean intercropped with maize in Alfisols. In addition, increasing plant population density increases the efficient utilization of fertilizers and thus, boosts the seed yield of climbing bean in intercropping with maize. Four way interaction of N, P, FYM and population density significantly (p<0.05) affected grain yield of climbing bean in 2002 and combined over years (Table 1 and 3). This justifies that integration of different sources of fertilizers with population density enhance climbing bean yield in intercropping system. Similarly Rweyemau and Nadunguru[24] reported that increased yields were obtained with 7.5 t ha-1 manure, 25/10 kg N P ha-1 and with increased population density[25]. Therefore, optimum combinations are essential to boost the grain yield of climbing bean in intercropping with maize system.
Climbing bean grain yield was significantly (p<0.05) affected when compared between intercropped and sole cropped climbing bean (Table 2 and 3). Sole cropped climbing bean produced higher grain yield compared to intercropping system. Mean grain yield advantage of 82, 34.49 and 60.31%, respectively in 2002, 2003 and combined mean were obtained from sole cropping compared to intercropping (Table 2). The grain yield of intercropped climbing bean was reduced by 45, 26 and 38% as compared to sole planting (Table 2), which agree with Demesew[21] in bush bean intercropped with maize. Chemeda[26] under intercropping, bean with maize, grain yields were reduced with the average of 67 and 24%, respectively. Pilbeam et al.[27] found 59% yield reduction of bean due to maize-bean intercropping which reflected greater competitive ability of maize in the system.
The mean values of all factors combination in intercropping system gave lower grain yield of climbing bean than sole planted climbing bean. Similarly Tolessa et al.[23] the yield of haricot bean in intercropping system at all levels of nitrogen and phosphorus was lower than in a sole crop. Abdissa and Girma[2] the mean grain yield of sole haricot beans with or without fertilizer was significantly higher at p<0.01 for both treatments compared to the mean grain yield of haricot beans that were intercropped with maize. The grain yield climbing bean was reduced in intercropping system compared to sole cropping. The results are in agreement with Tsubo et al.[28]. This might be due to competition exerted by maize plant[29]. Thus, in intercropping maize/climbing bean, maize is more competitive and/or aggressive than climbing bean that was similar with Aleman[30] and Willey and Osiru[31] indicated that maize has superior competitive ability than bean in a mixture.
Maize: Maize grain yield was non-significant affected among all treatment factors used (Table 1-3). Mean grain yield maize decreased as the level of N and plant population of climbing bean increased. This might be due to an increase in the available soil nitrogen to maize in intercropping system and sparing effects and direct transfer of N from legume. In addition it might have increased efficiency of nitrogen at lower level due to application of phosphorus and farmyard manure. Since the two crops were planted on the same row and their roots were intermingled, therefore there was high possibility of N transfer from legumes to cereals. Increasing the population density of climbing bean had negatively affected the yield of maize in intercropping system, which agree with Demesew[21]. Maize grain yield was decreased as population of climbing bean was increasing, which may due to greater interspecific competition of climbing bean with maize for growth factors as the population density increased from one bean to two bean per one plant of maize in the system.
Grain yield of maize was non-significantly affected when comparing intercropped with sole cropped maize (Table 2). The highest maize grain yield was recorded from sole cropped as compared to intercropped maize. The grain yield of intercropped maize was reduced by 9.72 and 0.18% as compared to sole cropped maize in 2002 cropping season and combined over years, which agree with Tolessa et al.[23], Harwood et al.[32] and Davis and Garcia[33]. Similarly Kimani et al.[34] intercropping maize with bean tended to lower maize grain yield but the effects are not significant. Setegn[35] found that the yield levels of maize were reduced as high as 781 kg ha-1 in mixture with different genotypes of climbing bean, but non-significant difference was observed when sole and intercrops were compared. Francis et al.[9] reported a drastic reduction of 31% in yield of maize when intercropped with climbing bean. In addition, the yield differences in crop mixtures are influenced by not only the presence of other crops, but also by densities and spatial arrangement of crops[36] and levels of resource availability in the two systems. As compared to climbing bean the yield reduction in maize was not significant when grown in a mixture.
Land Equivalent Ratio (LER): Partial LER of climbing bean was significantly (p<0.05) different in 2002 cropping season and combined over years but non-significant in 2003 due to N rates (Table 2). The mean partial LER was increased as the rates of applied N increased. Application FYM significantly (p<0.05) increased partial LER of climbing bean (Table 2). Mean partial LER of climbing bean was significantly (p<0.05) different when sole cropped compared to intercropping in 2002, 2003 cropping season and combined over years (Table 2). Nitrogen and FYM were non-significantly affected partial LER of maize but significant (p<0.05) effect combined over years (Table 2). Partial LER of maize significantly (p<0.05) affected by population density in 2003 cropping season. Partial LER of intercropped maize compared to sole cropping was non-significant.
Application of N significantly (p<0.05) affected LER of maize and climbing bean intercropping system (Table 2). LER was significantly increased as the rate of N increased. The productivity and land use efficiency was increased due to N that is in agreement with the finding of Demesew[21] LER significantly increased with each increment in N rates in maize/bush bean intercropping system. Farmyard manure scientifically (p<0.05) increased LER of maize-bean intercropping system. Grain yield advantage of 8.5, 21 and 15% were obtained as the rate of FYM increased in intercropping system. Population density non-significantly increased LER of intercropping system (Table 2).
The LER of intercropping as compared to sole cropping was significantly (p<0.05) different (Table 2). The LER of intercropping was greater by 0. 46, 0. 98 and 0. 72, respectively than sole cropping in 2002, 2003 and combined over years. This implies that intercropping maize/climbing bean is giving the highest yield advantageous and land use efficiency of 46, 98 and 72% more than the sole planting component crops which was similar with Abdissa and Girma[2] 17% more yield and higher land use efficiency by intercropping of maize with haricot bean compared to monocropping of component crops. Similarly Tsubo et al.[28] on average, the intercropping had an 8% yield advantage over sole cropping system. The overall LER of intercropping was greater than the sole planting of the component crops. The uses of NP and FYM fertilizers with population density of climbing bean were more productive and agronomically feasible for intercropping maize/climbing bean than monocropping the component crops. The lowest mean (32%) and the highest (98%) yield advantage and land use efficiency of intercropping were obtained compared to sole planting component crops. Similarly Chemeda[26] that maximum of 28% relative yield advantage was obtained with intercropping. These results justify that the association between two component crops was mutualistic and complementary. The interaction effects of N and P significantly increased the total productivity of intercropping system (Table 1). The LER of intercropping were indicated that, there were higher yield advantages and land use efficiency of maize/climbing bean intercropping. Similar results are reported by Habtamu et al.[1] and Hegewald[37].
Nitrogen, Farmyard manure and population density significantly affected grain yield of climbing bean indicating the need of different cultural and fertility management factors for climbing bean production in intercropping. Partial LER indicates great yield advantage of maize and moderate yield advantage of climbing bean and the dominance of maize over climbing bean in intercropping system. Total LER indicated higher combined grain yield advantage of intercropping over separate planting of each crop. For increased production per unit area, intercropping is a viable agronomic option for maize-climbing bean. Intercropping of maizeclimbing bean with 69/10 N/P kg ha-1 8 FYM t ha-1 and 44,444 plants ha-1 were recommended for better grain yield of component crops.
ACKNOWLEDGMENTS
The authors thanks the Oromiya Agricultural Research Institute and Agricultural Research Training Program (ARTP), of the Ethiopian Agricultural Research organization who made the study successfully through the fund grants. We are also grateful to Mr. Tesfaye G/girogis, Mr. Amsalu Fekadu, Mr. Hirko Sukari, Mr. Tesfa Borena and Mr. Bekele Wakijira for their assistance in carrying out the experiment and efficiently collecting the data.
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