The project was aimed at determining the agronomic and economic benefits of intercropping bean with banana in Puerto Rico. For achieving the first objective, we intercropped two bean cultivars, either once or twice with a banana cultivar, in the first field experiment to determine the best timing and frequency of this intercropping.. The November planting of banana, together with two consecutive cycles of bean intercroppings proved to be the best timing and frequency of the intercropping. Banana yields were not significantly affected by either one cycle or two cycles of bean intercropping. For achieving the second objective, we collected soil and banana leaf tissue samples from the first field experiment and analyzed for nitrogen content under laboratory conditions to determine the contribution of bean plants to nitrogen fertility of the soil and to the intercropped banana plants. Soil analysis data indicated that the contribution of bean plants to total nitrogen, ammonium nitrogen and nitrate nitrogen contents in soil was minimal. Plant tissue analysis data indicated that there was no significant difference in total nitrogen content between the intercropped banana plants and the banana monoculture plants. The contribution of bean plants to weed control was also determined from the same field experiment. The weed count in the bean-intercropped plots was significantly lower in bean-intercropped plots than in non-bean intercropped plots during the November and January plantings, but in March and May plantings there was no such difference. The plant cover factors of bean and banana plants were collected from the first field experiment for calculating the soil loss under bean-intercropped and banana monoculture conditions. There was a greater amount of soil loss detected in the bean-intercropped plots than in the banana monoculture plots. To achieve objective 3 on the economic benefits of adopting bean/banana intercropping practice, we conducted a second field experiment next to the first field experiment. Eonomic analysis data indicated that two cycles of bean intercropping produced a combined net income of $4,319.12/ha. This sum is $3,008.17/ha more than the net income of $ 1,310.95/ha from banana monoculture.
There are three objectives included in this proposed research:
1. Determine the effects of planting time and frequency of bean on yield and quality of banana.
2. Determine additional benefits of intercropping as contribution to nitrogen fertility, weed control, and soil conservation provided by intercropped bean.
3. Determine the economic feasibility of the best planting time and frequency of bean/banana intercropping on a semi-commercial scale.
Intercropping has not been widely practiced in the highly mechanized U.S. agriculture except for certain tree crops, grass-legume pasture system, and nursery crops for establishing seedlings. However, intercropping is a common practice in developing tropical countries. The intercrop- ping of either banana or plantain with bean is being practiced in the Caribbean region, central and south American and African countries (11,13,14). Rao and Edmund (9) found that banana yield was not significantly reduced by intercropping with other crops such as cowpeas, maize, or sweet potatoes. In Puerto Rico, information on agronomic and economic benefits of bean/banana intercropping is lacking. This project is intended to gather information in this regard.
Banana is among the most important farm crops in Puerto Rico. In 1995-96, some 318 million fruits were produced for a gross income of $6.1 million (2). This production was a joint effort of about 1,000 family-oriented farmers. Their livelihood depend chiefly on the planting of this crop. Because banana has a relatively long growing cycle, requiring 12 to 14 months to harvest a crop, this growth period represents a long wait for banana farmers to recover their investment. Any additional income that can be earned during the wait for banana harvest would be financially attractive. Green-shelled beans are a fast-growing speciality crop in Puerto Rico. Its local production amounted to 9,072 kgs. in 1994/1995 with a cash value of $ 34,000. The opportunity to increase production of green-shelled bean exists if bean intercropping technology with banana is developed. In addition, the conservation-oriented saving from increased nitrogen fixation (5), reduced weed competition (7), lessened usage of herbicides and increased soil organic matter associated with bean intercropping can hardly be expressed in term of monetary gains.
In the first field experiment, two bean cultivars (Arroyo Loro and 9443-1) were intercropped either once or twice at four banana planting times (November, January, March and May) with a standard banana cultivar, Grand Nain. The site of this experiment was situated on the sloping farm of Agro. Pedro A. Santo-Grillo at an elevation of 150 m above sea level. The farm is located in the precinct of Caguitas, Aguas Buenas, north central part of Puerto Rico. The soil is Múcara clay, clayey, monmorillonitic, isohyperthermic, shallow Vertic Eutropepts. The land chosen for the experiment has a slope of about 30%. It was originally a grazing pasture field and converted by us into no till banana-bean intercropping practice. The experimental design was a randomized complete block with four replicates. Treatments were as follows: one cycle of bean intercropping at the time of banana planting, two cycles of bean intercroppings at the time of banana planting and immediately after the harvest of first crop of bean, banana monoculture and bean monoculture. Each plot consisted of 6 banana plants planted in two rows with a planting distance of 1.8 m x 2.7 m. Two rows of banana were planted in each plot along the contour line. Four rows of bean were intercropped within the two banana rows and two additional rows of bean were intercropped outside each banana rows. Bean seeds were treated with Nitragin (Rhizobium phaseoli ) before all the plantings. All agronomic and pesticide management features were in accordance with recommended practices (3,6). Each cycle of bean crop was harvested at about nine weeks after planting. One cycle of banana plants was harvested during a time span of 14 to 18 months after planting.
The enhancement of nitrogen fixation by bean plants was determined by sampling soil within the bean rows with a small-stainless-steel core sampler to two depths (0 to 15 cm and 15 to 30 cm). The collected soil samples were analyzed for total nitrogen content at the Central Analytical laboratory of the Agricultural Experiment Station in RíoPiedras. Two grams of soil was weighed in a micro Kjedahl apparatus, and subsequent chemical analysis for total nitrogen content (1,4,12) was performed. Banana leaf tissue samples were also collected after each bean harvest and dried in an oven at 115 oF and ground with a Wiley Mill to determine the nitrogen status within the banana plants. In this case, only 0.5 gm of dried banana leaf tissue was weighed and processed for determining the total nitrogen content The contribution of bean plants to weed control was determined by counting weeds randomly within each plot per unit area after each bean harvest. A steel cuadrant (30.5 x 30.5 cm) was thrown four times in each plot for counting the weeds inside the square.
Soil erosion losses were determined on both banana-bean intercropped plots and banana monoculture plots by using the Revised Universal Soil Losses Equation (RUSLE)(10):
where A is the computed soil loss per unit area; R is rainfall and runoff factor; K is the soil erodibility factor; L is the slope-length factor; S is the slope-steepness factor, C is the cover and management factor, and P is the support practice factor.
Biomass data were collected for banana, bean, and grass vegetation from the experiment during the banana growth cycle. The collected data were used for calculating the C factor (cover and management factor) of the above mentioned equation. All factors other than C factor as described in the equation are the same for all the treatments involved.
A second field experiment was conducted at a site next to the first field experiment using the selected bean cultivar, Arroyo Loro, to intercrop with the same banana cultivar Grand Nain. A randomized complete block design with six replications was used. Two treatments consisted of (1) banana with two cycles of Arroyo Loro intercroppings and (2) banana monoculture for achieving objective 3 on the economic benefits of adopting bean/banana intercropping practice.
Bean and banana yields were recorded to serve as bases for calculating gross income derived from the experiment. All the fixed and variable costs involved in producing and harvesting bean and banana were also recorded for calculating the net incomes for the two treatments. A partial budget analysis (Perrin et al., 1981) was used to perform all economic analyses for adopting the profitable bean/banana intercropping system on a semi-commercial scale.
There was no significant banana yield difference (at P<0.05 level of probability) among any of the four bean-intercropped treatments and the banana monoculture treatment within each of the four planting dates (table 1). This result indicated that banana yield was not significantly affected by bean intercropping provided that all intercropped treatments were planted at the same time with banana monoculture. However, banana yield was signicantly less when planted in January, March and May, irrespective of intercropping or monocropping. A similar trend of yield reduction with the time of planting was also noted for bean plants (table 2). When the yield data of bean were analyzed on the basis of the frequency of intercropping, two cycles of intercroppings produced consistently a higher bean yield than one cycle of intercropping. The combined yield data of banana and bean again showed that November planting produced highest yield for both crops. Of the two bean cultivars, Arroyo Loro yielded a slightly higher than 9443-1 irrespective of different months of planting. Objective 2:
In our earlier analysis for total nitrogen content of collected soil samples, we found that only one of 16 bean-intercropped treatments contained a signficantly higher increase (P< 0.05) in total nitrogen content than banana only treatment at the 0-15-cm soil depth. However. none of the bean-intercropped treatments significantly increased total nitrogen more than bean only treatment at the 15 to 30-cm soil depth (table 3). Since all of our previous soil samplings were done after each harvest of bean, not during their active growing stage, nitrogen fixed by bean plants might have been lost through leaching process during this time lapse. As the nitrogen status in soil is of dynamic nature or in other words, it changes with time, we decided to shorten the sampling interval to a weekly basis to determine whether it is possible to detect any minute change in total nitrogen content of the soil. None of the soil samples from the bean-intercropped treatments showed any significant increase of total nitrogen content over that of the non-bean treatment at the 0-7.6-cm soil depth during the 10 consecutive weeks of soil sampling (Table 4). Only 5% of soil samples from the bean-intercropped treatment showed a significant increase of total nitrogen over that of the non-bean treatment at the fifth week at the 7.6 to15.0-cm soil depth. There was no significant increase in ammonium nitrogen content in soil samples of bean-intercropped treatment over that of the non-bean counterpart at the 0 to7.6-cm depth for first nine consecutive weeks with only one exception, which occurred at the 10 th week (table 5). Neither was there a significant increase in ammonium nitrogen content in soil samples of bean-intercropped treatment over that of the non-bean counterpart at 7.6 to15.0 cm-depth with the only exception which occurred at the seventh week. There was no significant increase in nitrate nitrogen content in soil samples of the bean-intercropped treatment over that of the non-bean counterpart at the 0 to7.6 cm soil depth for 10 consecutive weeks (Table 4). The only significant increase in nitrate nitrogen content of soil samples of the bean-intercropped treatment over that of the non-bean counterpart was at 7.6 to15.0 cm depth which occurred at the fifth week. In view of fact that only 6.7 % of bean-intercropped soil samples showed a significant increase over that of the non-bean counterparts in only one of the aboved mentioned nitrogen forms, we concluded that contribution of bean-intercropped treatment to nitrogen fertility was minimal. At the end of the first field experiment, soil samples were taken to determine their total nitrogen, ammonium nitrogen and nitrate nitrogen status in the soil. No bean-intercropped treatments showed any sigificant increase in total nitrogen content over that of the non-bean treatment (banana monoculture) in 0 to10, 10 to 20, and 20-30 cm soil depths (table 5). Neither was there any significant increase in ammonium nitrogen content for the bean-intercropped treatments over that of the non-bean treatment at all three soil depths. There was no significant increase in nitrate nitrogen for the bean-intercropped treatments over that of the non-bean treatment at first two soil depths (0-10 cm and 10-20 cm). However, at the 20 to30 cm- depth. three bean-intercropped treatments showing a significantly higher nitrate content than the banana monoculture treatment (table 5). Soil samples were also collected at the end of the first field experiment, to determine the effect of intercropping on the chemical and physical properties of the soil. Apparently, the intercropping had no significant effect on any of the soil properties such as pH, conductivity, cation exchange capacity, calcium, potassium, magnesium, phophorus and organic matter contents at 0 to10, 10 to 20 and 20-30cm soil depths (tables 6 and 7). However, the only exception was a significant increase of potassium content of the intercropped bean treatment over that of the non-bean treatment (banana monoculture treatment) at 10 to 20 cm-depth (table 8). In the same experiment, we also analyzed leaf tissue samples of banana for total nitrogen content at the end of each bean harvest from the first field experiment. There was no significant increase in total nitrogen content of the bean intercropped treatment over its non-bean counterpart (table 9). Neither was there any significant increase in phosphorus, potassium, magnesium or calcium contents of the same banana leaf tissue samples between the the bean-intercropped treatments and their non-bean counterparts (Data not shown). The contribution of bean plants to weed control was also determined from the same field experiment by counting weeds present in plots after the bean harvest (Table 10 ). The shading effect of bean leaf canopy significantly reduced the weed population in bean-intercropped plots over non-bean counterparts during the November and January plantings. In the March and May plantings, there was no significant difference in number of weeds between the bean-intercropped plots and non-bean intercropped plots. Table 11 presents the biomass and estimated soil loss data derived from objective 2 studies. The bean intercropped treatments produced slightly greater biomass than that of banana monoculture. However, soil loss was much greater in bean intercropped plots (11.51 and12.24 ton./A/yr.) than banana monoculture plots (0.81 ton./A/yr). This might be attributed to greater grass canopy cover and lesser degree of soil disturbance under banana monoculture conditions. There was not much soil loss difference between the banana plus two cysles of bean intercropping and the banana plus one cycle of bean intercropping. Objective 3:
Table 12 summarizes gross incomes, production costs and net incomes derived from intercropped treatment and its banana monoculture counterpart from the semi-commercial seond field experiment. We found that two intercroppings of the bean cultivar Arroyo Loro with the banana cultivar Grand Nain produced a higher gross income ($20,708/ha) than its banana monoculture counterpart ($11,031.37/ha). Similarly, the two intercroppings of bean with banana produced more combined net income ($4,319.12/ha) than banana monoculture ($1,310.95/ha). A difference of a combined net income of $3,008.17/ha from the two intercroppings of bean over that of the banana monoculture was thus obtained.
Educational & Outreach Activities
L.C. Liu, Economic benefits by intercropping bean with banana, Abstract presented at the Annual Meeting of the Puerto Rican Agricultural Sciences Society. p39 . Lajas, P.R. 1997.
L.C. Liu, Experiencias en el taller del SARE en Memphis, Tennessee, in Agrotemas, a monthly newspaper of Puerto Rican Agriculture. April , 1998. P. 24.
L.C. Liu, R. Montalvo-Zapata, Juan Ortiz-Lopez and J.A. Rodriguez. Intercalado de Guineos con Habichuelas, in Agrotemas, a monthly newspaper of Puerto Rican Agriculture. May , 1998. P. 23.
L.C. Liu, R. Montalvo-Zapata, Juan Ortiz-Lopez and J.A. Rodriguez, Effects of Planting Times and Frequencies of Intercropping on Yield and Incomes of Bean and Banana. Submitted for publication in the Journal Agriculture, University of Puertto Rico.
I visited Mr. Pedro Laverne, Extension Agent of the Cooperative Extension Service in Aguas Buenas area in January 1997 for planning to hold a field day at the Agro. Pedro Santo’s Agua Buenas farm. A field day was held as planned on February 20, 1997. Despite hazardous roads and rainy weather, 11 people attended. These included two agronomists, one chemist, one extension agent, one commodity leader, one economist, and a couples of farmers. The attendees were brought up to date on the results and findings obtained by us during the past year. A seminar sponsored by Agricultural Extension Service was held at the Barranquitas Community Center on August 29, 1997 on bean production and new varieties. I was invited to give a talk on the results of our project concerning bean-banana intercropping practice. The seminar was attended by 40 farmers from Naranjito and Barranquitas municipalities of Puerto Rico.
On January 21 ,1998, I attended a SARE Professional Development Workshop in Memphis, Tennessee,and presented a poster entitled “Intercropping bean with banana.”
On February 12, 1998, at 6:00 to 7:00 am, I was interviewed by Mrs Mildred Cortes of the Agro. y Mar Program WIPR 940 AM program to talk on the progress results and recommendations of intercropping bean with banana.
Mr. Jose Aponte, Conservation Agronomist,of the Natural Resources Conservation Service (NRCS), Caribbean Area Office, USDA is cooperating with us in this research. His work involves: (1) Laying out the contour lines and hillside ditches for our field experiments. (2) Collecting biomass data needed for the Revised Universal Soil Loss Equation (10) for predicting soil losses under bean intercropped and banana monoculture conditions. We have also learned from Mr. Jose Castro of the NRCS on how to calculate C factors which are needed for calculating the soil losses under banana-bean intercrpping situations.
The result of our first banana-bean intercropping experiment indicated that the most productive intercropping treatment was the November planting of banana together with two consecutive intercroppings of bean cultivar Arroyo Loro. By adopting this November planting of banana with two intercroppings of bean, banana farmers living in the mountain region of Puertto Ricco would be earning an additional income of $ 3,008.17/ha as obtained from our second field experiment. In addition, banana yields were not significantly affected by intercropping of bean, irrespective of different dates of their planting. All these favorable results should promote the practice of bean-banana intercropping in Puerto Rico. The inclusion of soil conservation practices (no tillage and contour planting) in our field experiments will serve as a model for banana farmers to achieve sustainable production of this commodity.
Furthermore, during the course of conducting our field experiments, we observed that a number of banana plants with heavy fruit bunches were toppled. In order to prevent the fruit bunches from falling to the soil, we have developed a fruit supporting practice by the use of PVC pipe (1.5 m long x 5.1 cm in diameter) coupled with a piece of y-shaped tree branch. This practice proved to be highly effective and cheap, and should be adopted by the banana farmers in the mountain regions of Puerto Rico. We are disappointed for the finding that a positive contribution of the intercropped bean to nitrogen fertility in soil or to the banana plants did not materialize. The bean seeds we used were treated with nitragin inoculum and developed normal nodulation on roots. However, the probability of reducing the use of chemical fertilizer through the aid of nitrogen fixation of the bean plants did not succeed in the present research.
Areas needing additional study
1. Anderson, J.M. Tropical Soil Biology and Fertility, Methods Handbook, Univ. of Exeter, Exeter, Devon,U.K.
2. Anonymous, 1990. Ingreso Agrícola de 1990-91, Oficinade Estadisticas Agrícolas, Departamento de Agricultura. Estado Libre Asociado de P.R.
3. Beaver, J.S. , R, Echavez-Badel, A. M. Armstrong and E.C. Schroder. 1992. Conjunto tecnológico para la producción de habichuelas. Estación Experimental Agrícola, Recinto de Mayaguez, Univ. de P.R. 34 pp.
4. Chapman, H.D. and P.F. Pratt, 1961. Method of analysis of soils, plants and waters, pp. 102-107.
5. Francis, C., A. Jones, K. Crookston, K. Wittler, and S. Goodman. 1986. Strip cropping corn and grain legumes: A Review. Amer. J. of Alternative Agriculture 1(4): 159-164.
6. Irizarry, H. and R. Montalvo-Zapata. 1995. Conjunto tecnológico para la producción de plátano y guineo. Estación Experimental Agrícola, Recinto Mayaguez, Univ. de P.R. Bulletin No. 97. 46 pp.
7. Moss, P.A.and N.L. Hartwig, 1980. Competitive control of common lambsquarter in
a corn-soybean intercrop. Proc. Northeast Weed Sci. Soc. Meeting. 34:21-28.
8. Perrin, R.K.,D.L. Winkelmann, H.R.Moscardi, and J.R. Anderson. 1981. Formulación de recomendaciónes a patir de datos agronómicos: un manual metodológico de evaluaciónes economica. CIMMYT No. 27.
9. Rao,M.M.,and J.E. Edmunds. 1984. Intercropping of banana with food crops: cowpeas, maize and sweet potatoes. Trop. Agric. 61: 9-11.
10. Renard, K.G., G.R. Foster, G.A. Weesies and J.P. Porter. 1991. Revised Universal Soil Loss Equation. J. of Soil & Water Conservation 46; 30-33.
11. Valencia, M. J.A.,S.C. Belalcázar, M.I. Arcila, H.R. Garcia R.and A. González., 1995. Efecto del intercalamiento simultáneo de frijoles, maiz y yuca sobre el crecimiento y la producción de plátano del clon Dominico Harton, Musa AAB Simmonds. Nueva Tecnológia para la Producción de Plátano 63-70.JCA-CORPOICA AA 1069, Armenia, Quindio, Colombia.
12. Warner,M.H. and J.B. Jones. Technicon Corporation, Determination of Total Nitrogen in Plant Tissue using Technicon Kjeldahl Nitrogen Apparatus Pag. 29-66.
13. Wortmann, C.S., T. Sengooba and S. Kyamanywa.,1992. Banana and Bean Intercropping: Factors affecting bean yield and land use efficiency. Expl. Agric. 28:
14. Wortmann, C.S. and T. Sengoodba., 1993. The banana-bean intercropping system interaction-bean genotype x cropping system interactions. Field Crop Research. 31: 19-25.