African Crop Science Journal African Crop Science Society ISSN: 1021-9730 EISSN: 2072-6589 Vol. 5, Num. 1, 1997, pp. 15-22

Effects of planting pattern, relative planting date and intra-row spacing on a haricot bean/maize intercrop

CHEMEDA FININSA

Department of Plant Sciences, Alemaya University of Agriculture, P.O. Box 138, Dire Dawa, Ethiopia

(Received 17 January, 1996; accepted 12 February, 1997)

Code Number: CS97003
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Performance of five bean (Phaseolus vulgaris L.) genotypes grown in mixed and row intercropping pattern with maize (Zea mays L.) or sole cropping, were evaluated in the Hararghe highlands of Ethiopia. Under intercropping, bean and maize grain yields were reduced on the average by 67% and 24%, respectively. The effects of five relative planting dates of the two crops and three intra-row spacings on bean performance and maize grain yield in mixed intercropping were also evaluated. Delayed maize planting and simultaneous bean and maize planting improved bean seed yield. With simultaneous planting, bean yield was increased by 48.5%. In contrast, delayed bean planting and a 0.10 m bean intra-row spacing increased maize grain yield and reduced bean seed yield. The productivity of the bean/maize intercrop as determined by Land Equivalent Ratio was superior, in all combinations, compared to sole cropping. A maximum of 28% relative yield advantage was obtained with intercropping.

Key Words: Phaseolus vulgaris L., Zea mays, Land Equivalent Ratio

RESUME

La performance de cinq genotypes de haricot eleves en culture mixte et en rangs avec le mais et en monoculture etaient evaluee sur le plateau d' Haraghe en ethiopie. Les recoltes de haricot et du mais variaient significativement selon le systeme de culture. En culture mixte, la recolte de haricot et du mais etait reduite par 67 % et 24 % respectivement. Les effets de cinq dates relatives de semis de deux plantes et trois distances entre les rangs sur la performance de haricot et la recolte du mais en culture mixte etaient aussi evalues. Un semis tardif du mais et un semis des haricots et du mais simultane augmentent la recolte de haricot. En utilisant la plantation simultanee, la recolte augmentait de 48.5 %. Contrairement, un semis tardif de haricot et un espacement au sein des rangs de 0.10 m avec de haricot augmentent la recolte du mais et diminuent la recolte de haricot. La productivite de la culture mixte haricot/mais determinee par le rapport ˆ l'equivalent-terre etait superieure dans toutes les combinaisons. Un avantage en recolte relative de 28 % au maximum etait obtenu avec la culture mixte.

Mots Cles: culture mixte, espacement entre les rangs, rapport equivalent-terre, date de plantation

INTRODUCTION

Intercropping legumes with non-legume is an important feature of many cropping systems in the tropics (Willey, 1979; CIAT, 1986). There are several socioeconomic (Ofori and Stern, 1987), and biological and ecological (Van Rheenen et al., 1981; Aggarwal et al., 1992; Chemeda, 1996) advantages to intercropping relative to sole cropping for small-holders.

Intercropping is a principal means of intensifying crop production both spatially and temporally, and improves returns from limited land holdings in the Hararghe highlands of Ethiopia (Storck et al., 1991). This region is one of the major haricot bean (Phaseolus vulgaris L.) producing centres in East Africa. Bean is the major food legume in this area and is grown primarily as an intercrop (83%) with maize (Zea mays L.) and sorghum (Sorghum bicolor L. Moench). Bean varietal mixtures are sown by broadcasting after the associated crop completes vegetative growth. In this system, bean yields are low, interspecific competition is high, population density is undetermined, and harvesting is complicated by the varying maturities of the intercrops.

Although bean and maize intercropping is a common practice in the Hararghe highlands, quantitative information is lacking on the productivity of the system, its influence on bean yield and yield components, and the performance of bean cultivars under various intercropping patterns. In addition, the effects of management such as relative planting dates of bean and maize and intra-row spacing, on yield has not been determined. This paper presents results of a bean/maize intercropping trial in the Hararghe highlands of Ethiopia conducted under low input conditions over two main cropping seasons.

MATERIALS AND METHODS

Experimental site.

The experiments were conducted during the summer seasons of 1993 and 1994, at the Alemaya University of Agriculture (AUA) experimental field station, East Hararghe (9 degrees 26'N, 42 degrees 3'E, altitude 1980 m), on cultivated alluvial soil. The total rainfall during the experimental period (May-September 1993) was 401.60 mm and mean maximum and minimum temperatures were 24.18 C and 13.24 C, respectively. Weather data for the second growing season were not recorded from the station, but from the nearby meteorological station (25 Km South), 512 mm were received. Rain was relatively uniform except during the second half of June 1994, which was drier.

Associated crops. Five bean genotypes were used; A-176 and GLPX-92 from Centro International De Agricultura Tropical (CIAT), Brown speckled Mexican 142, and Red Wolaita from the Institute of Agricultural Research, Ethiopia. Based on CIAT's classification, the growth habit of the five genotypes is bushy and of type I. Mexican 142 and Red Wolaita are widely grown countrywide in Ethiopia in sole and intercrop systems. An improved and commonly grown maize variety, Alemaya Composite, developed by AUA, was the other component of the intercrop. Alemaya Composite matures in six months, possesses horizontal leaf, and has plant height ranging from 2.5-3.0 m.

Experiment 1. During the summer cropping seasons of 1993 and 1994, three cropping systems were evaluated in a randomised complete block design with three replicates. The systems comprised mixed intercropping with beans sown within maize rows, row intercropping with two bean rows planted between maize rows, and sole cropping. Both maize and beans were hand-sown in rows in plots of 7.6 m x 2.4 m. Maize seeds were sown at the rate of two seeds per hill on 11 May and the seedlings thinned to one plant per hill after two weeks. The bean genotypes were sown one month later than maize at the rate of one seed per hill.

For sole cropping, bean rows and bean plants within a row were 30 cm and 10 cm, respectively. For row intercropping, two rows of maize were sown in rows 75 cm apart with a 30 cm intra-row spacing. Two bean bean rows were sown between consecutive maize rows. The bean rows were sown with a 40 and 10 cm inter-and intra-row spacings, respectively. For mixed intercropping, beans were planted along the maize rows with a spacing of 10 cm between plants within the rows. Mean bean populations ha^-1 for sole cropping, row intercropping, and mixed intercropping were 315,579, 82,379, and 78,947, respectively. For maize, population densities were 43,850, 38,139 and 43,860 ha^-1 for sole cropping, row intercropping and mixed intercropping, respectively. In sole cropping, the crops were planted at their optium plant densities. Recommended hand weeding and harvesting practices were followed, and no fertilizers or pesticides were applied. The whole plot area was harvested.

Experiment 2. In summer cropping season of 1994, five relative planting dates were used. Red Wolaita bean was sown 10 days before maize, simultaneously with maize, and 10, 20 and 30 days after maize. Late April to early May is the recommended optimum planting dates for maize and sole bean cropping in the region. Three bean intra-row spacings: 10, 15 and 20 cm were evaluated in a randomised complete block design with three replicates. Treatments were evaluated in mixed intercropping on plots of 7.6 m x 3.0 m with the total area harvested.

The first planting date was May 10 and the remaining treatments were relative to this date. Inter-row spacing was 75 cm apart; maize intra-row spacings were 30, 45 and 60 cm, corresponding to 10, 15 and 20 cm bean intra-row spacings, respectively. Bean populations ha^-1 corresponding to 10, 15 and 20 cm bean intra-row spacings were 87700, 57890, and 43850, while maize plant densities corresponding to the bean intra-row spacings were 43850, 28945, and 21945, respectively. Bean and maize population densities at 10 cm and 30 cm intra-row spacings, respectively, were at optimum. Similar agronomic practices were followed as in Experiment 1.

Data collection and analyses. Number of pods and of seeds per pod were recorded from 10 randomly selected bean plants in each plot. Bean seed yield at 10% seed moisture content and 100 seeds weight from each plot were recorded.

The yields of beans and maize were used to calculate Land Equivalent Ratios (LER), the relative land area required for sole crop to produce the yields achieved in intercropping in row and mixed intercropping (IRRI, 1974). Partial LER (individual crop's LER) and total LER (sum of individual crop' LER) were used as indices to evaluate the productivity of intercrop systems.

Combined analyses of variance was performed over two seasons for bean seed yield and yield components, maize grain yield, partial and total LER of the first experiment. For the second experiment, ANOVA of one season data was performed. Least Significance Difference test and T-test were used for mean separation wherever appropriate.

RESULTS

Bean yield and yield components. In Experiment 1, bean seed yield and yield components for each cropping system and bean genotypes are given in Table 1. Bean seed yield was significantly different (P<0.05) among the cropping systems. In both mixed and row intercropping, bean seed yield was reduced compared to sole cropping. However, the number of pods per plant and number of seeds per pod were not significantly different among the cropping systems.

In contrast, significant differences were found among bean genotypes for seed yield and 100-seed weights (Table 1). In both seasons, GLPX-92 performed the best in both intercropping and sole cropping compared to other genotypes. Bean genotype by cropping systems interaction for yield and yield components was not significant (P<0.05).

In Experiment 2, yields were highly significant different among the planting dates (P<0.01). The highest yield of 965 kg ha^-1 was obtained when the bean cultivar was planted simultaneouslywith maize, while the lowest of 653 kg ha^-1 was obtained when the cultivar was planted 30 days after maize (Table 2). Number of pods per plant varied significantly among bean intra-row spacings. The highest number of pods per plant (21) and seed yield (801 kg ha^-1), were obtained when the bean was planted in 20 cm intra-row spacing. However, seed yield and number of seeds per pod among intra-row spacings did not differ significantly (P>0.05). Relative planting dates by intra-row spacing interaction for yield and yield components were not significant (P>0.05).

Maize grain yield. Maize grain yield from both mixed and row intercropping differed markedly in terms of intercropping and the associate bean genotypes (Table 1). Maize grain yield was higher in row than in mixed intercropping. The highest grain yield of 4,928 kg ha^-1 was obtained when intercropped with Red Wolaita, while the lowest (3,713 kg ha^-1) was when intercropped with Brown speckled.

Table 1

Table 2

Productivity of intercropping. Productivity of intercropping was evaluated using partial and total LERs as indices. Partial and total LERs for mixed and row intercropping are shown in Table 3. Both LERs for the associate crops under the intercropping varied significantly (P<0.01). Partial LERs for the crops in the intercropping systems are less than one. In row intercropping, the total LER indicates about 30% relative yield advantage.

Table 3

The partial LERs for the crops from the relative planting dates in mixed intercropping varied significantly (P<0.05). The highest partial bean LER (0.36) was obtained when the crops were simultaneously planted while the lowest (0.24) was when bean was planted 30 days after maize. In comparison, the highest (0.93) and the lowest (0.65) partial maize LERs were registered when bean was planted 20 days after maize and 10 days before maize planting, respectively. The total LER of relative planting dates ranged from 0.98-1.18; the highest being when bean was planted 10 or 20 days after maize and the lowest when bean was planted 10 days before maize (Table 4). The partial and total LERs of maize varied significantly among the bean intra-row spacings (P<0.05). The highest maize partial and total LERs were obtained when bean was planted in 10 cm intra-row spacing.

Table 4

Under intercropping, bean seed yield was reduced on average by 67% compared to sole cropping. The yield reduction was related to reduced number of pods and seeds per pod. Similarly, maize grain yield was reduced by 24% in intercropping. Yield reduction of the associate crops in intercropping, although specifically not determined, could be due to interspesific competition for resources such as nutrients, water and root spaces and the reduced density of the associate crops in the system. In mixed intercropping, maize competion is higher and bean population density is lower compared to sole cropping. However, the relative contribution of yield reducing factors in the intercropping systems could not be determined from the experiments. Willey and Osiru (1972) and Dagnew (1981) indicated bean and maize yield reduction when plant population density is lowered in intercropping.

The bean genotypes used differed in yields under the intercropping systems. For example, GLPX-92 yielded better in mixed intercropping than the others whilst Brown speckled yielded better in row intercropping followed by Mexican 142. Low yielding genotypes like Mexican 142 and Red Wolaita in sole cropping, gave similar yield to others in intercropping. Thus, bean genotypes behaved differently among cropping systems, as reported earlier (Willey and Osiru, 1972; Woolley and Rodriquez, 1987). Genotypes may also vary in their ability to compete for resources with maize, in addition to the shading effects. From these results, it appears that research that targets small-scale farms to adopt improved varieties may need to evaluate genotypes under different intercropping systems.

Our results indicate that delayed maize planting and simultaneous planting of bean and maize improves bean yield Table 2). With simultaneous planting, bean yield was increased by 48.5% compared to the traditionally prefered planting date in Hararghe region, of planting beans 30 days after maize. Simultaneous planting helps bean plants withstand maize competition. It is also advantageous in that it permits the establishment of the crops in one operation, and the possibility of double bean cropping per season. Simultaneous planting could also reduce labour and operational costs. In contrast, delayed bean planting favoured maize grain yield. These results are in agreement with those of Francis et al. (1982) and Francis and Stern (1987) with bean/maize and maize/cowpea intercropping systems, respectively.

In Hararghe highlands where there is limited land resources, evaluating productivity of intercropping systems is necessary. The productivity of bean/maize intercropping as determined by total LER, in all combinations, was superior in resource use efficiency compared to sole cropping. However, in mixed intercropping, bean produced only the equivalent of 23% of its sole crop yield while 38% was attained in row intercropping. Similarly, the equivalent of 77% and 92% maize sole crop yield was harvested when grown in mixed and row intercropping, respectively. The bean genotypes yielded the equivalent of 21 to 41% of their sole crop yield in intercropping. The intercropped maize variety yielded 78 to 97% of its sole crop yield. The relative yield advantage of bean intercropped with maize as indicated by total LER is up to 28% higher than could be achieved by growing the associated crops separately.

Bean seed yield in mixed intercropping increased to the equivalent of 36% from 23% of its sole crop yield when simultaneously planted with maize. The relative yield advantage of mixed intercropping also increased to a maximum of 18% when bean was sown 10 days after maize and at 10 cm intra-row spacing. It is apparent, therefore, that the highest relative yield advantage may be obtained if bean is grown in row intercropping, planted simultaneously with maize at 10 cm intra-row spacing.

The bean/maize intercropping systems in a row increased overall total productivity. The yield advantage in mixed intercropping is improved by 13% when bean is sown simultaneously with maize. This cereal/legume intercropping could benefit small-holders through generating sustainable income, minimising risk of crop failure and providing a source of protein diet. Intercropping also reduces incidence and severity of bean common bacterial blight and rust diseases under Hararghe conditions (Chemeda, 1996). The inclusion of a nitrogen fixing legume in the system could improve fertility of the Hararghe highlands' soils which are continuously depleted because of continuous maize and sorghum cultivation. Future studies should investigate the performance of such intercroping systems under different soil and climatic conditions. Moreover, the effects of the intercropping systems on the associate crops pathosystem and insect pests deserve research attention.

ACKNOWLEDGEMENT

The author would like to acknowledge the financial support of the Alemaya University of Agriculture, and Messrs Abeseloum Seyum and Amsalu Nebiyu, Department of Plant Sciences, Alemaya University of Agriculture for their assistance in data collection.

REFERENCES

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