INTERCROPPING COLOCASIA TARO WITH BLACK PEPPER (PIPER NIGRUM)ON POHNPEI

S. SILBANUS AND B. RAYNORl

Pohnpei Research Assistant, Sustainable Agriculture Research and EducationP. O. Box 216, Pohnpei, FSM 96941

Abstract

Black pepper (Piper nigrum) is an important cash cropon Pohnpei. Due to its perennial nature and slow growth,black pepper should lend itself to intercropping withannual crops, especially in the first few years ofestablishment, both in terms of ecology and cash income.There has been some concern that intercropping mayincrease disease in young pepper plantings. This paperreports on a six-month, on-farm trial of intercropping ofblack pepper with Colocasia taro.

Introduction

Black pepper (Piper nigrum) is one of the mostimportant cash crops on Pohnpei Island. However, byvirtue of its perennial nature, the initial establishment ofpepper gardens presents many problems to farmers.Newly planted gardens are subject to erosion, and weedgrowth is heavy and takes much labor to control. Hightemperatures in new farms also leads to high mortality ofyoung pepper vines. Also, since pepper takes nearly threeyears before it bears fruit, fmancial return to farmers isdelayed, to the point that many farmers abandon theirfarms in early stages. Intercropping newly establishedpepper farms with Colocasia taro (Colocasia esculenta (L.)Schott) could have many positive effects. The shade of thetaro plants could reduce weed growth and cool the soil,and the relatively fast maturity (8-9 months) could providethe pepper farmer with food and cash income in the firstcouple years before the pepper vines bear fruit. Althoughintercropping of new pepper farms has been considered asa possible strategy, and many farmers practice it, there issome concern that taro intercropping can lead to increaseddisease in young pepper plantations (Gnanaratnam,personal communication), especially foliar and root fungusdiseases. This research experiment was carried out toobserve the effect of intercropping Colocasia taro on blackpepper on Pohnpei Island.

Methods

In January, 1992, with the cooperation of the BlackPepper Section staff of the Pohnpei State Division ofAgriculture, four possible black pepper farmer/cooperators were identified in Madolenihmw Municipality.The study was limited to Madolenihmw because of lack oftransportation for the research assistants. These farmerswere selected based on their farms being one to two yearsold and on their willingness to adopt intercropping. Aftervisiting the farms and meeting with the farmers, HirokiTihpen's one-acre pepper farm in Wapar, Madolenihmwwas selected as the research site. Unfortunately,interplanting of taro on the farm was delayed by a five­month drought. In May, when the rains started again, fourplots of 25 pepper posts each were randomly selected anddelineated on the Tihpen farm. Two plots were plantedwith taro in single rows running between the rows ofpepper posts, with 1-m spacing between plants. The othertwo plots were left as a non-intercropped control. Thetaro cultivar planted was "Sawa Toantoal," the mostcommon and popular cultivar on Pohnpei (Raynor 1989).The farmer was allowed to maintain all plots based on hisregular practices, and all inputs (labor and amount) wererecorded during the study. Two research assistants visitedthe farm every two weeks. During the visits, survival,height, and diameter of pepper plants and height andnumber of leaves on taro plants were recorded. Weedpressure was also recorded during the visit by percentcover and height of various species. Data collection werecarried out for seven visits from May 21 to August 28,1992.

Results

In order to determine the effects of taro intercroppingon black pepper growth, the average pepper vine height inthe taro intercropped plots versus the non-intercroppedplots was multiplied by the average pepper vine diameterfor each data period to give an average vine volume. Theresults are presented in Fig. 1.

55

Discussion

24..-----------------, The decline in the non-intercropped pepper plot vinevolume in July was caused by the dieback of one vine toPhytophthora foot rot. The foot rot also led to a declinein diameter on some plants due to loss of leaves. Foot rot,a common disease in pepper farms on Pohnpei thateventually leads to vine death, was noticeably more evidentin the non-intercropped plots. It usually occurs in periodsof wetter weather and is more common in flat and poorlydrained areas of the pepper fields. Since our experimentwas limited to a small sample size and data was taken foronly three months, the lower incidence of foot rot in thetaro intercropped plots probably cannot be attributed tothe taro itself, but the results are encouraging for futurestudies.

Regarding the incidence of Paspa/um conjugatum in thepepper plots, there seems to be little difference betweenthe tarointercropped and non-intercropped plots (Fig. 2)in terms of weed pressure. The length of data collectionwas actually too short to notice any beneficial shadingeffects of the taro plants, because when data collectionwas suspended in late August, the taro plants had not yetformed a closed canopy. If the experiment had beencarried out longer, there might have been some beneficialeffects on weed pressure. The temporary decline ofPaspa/um in data period 7-1 is attributable to the cleanweeding of one of the taro intercropped plots by thefarmer's family. While this is not directly caused by thetaro itself, it does suggest that farmers might be moremotivated to weed their pepper farms if there is also taroor another crop in between the pepper posts. This extraweeding proves beneficial to both the intercrop and thepepper vines.

Conclusions

The initial conclusion based on this experiment,although too short and too limited to offer conclusiveproof, is that C%casia taro intercropping appears to bebeneficial to black pepper growth in new farms in termsof both decreased incidence of Phytophthora foot rot anddecreased weed pressure. Further field trials are neededto verify this conclusion.

Acknowledgements

The researchers would like to thank the staff of thePohnpei Division of Agriculture and local pepper growerHiroki Tihpen for their generous cooperation withoutwhich we could not have carried out this project. Wewould also like to thank the USDA LISA Project forfmancial assistance.

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10 5-2 6-1 6-2 7-1 7-2 8-1 8-2 9-1Data Period

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Fig. 1. Black pepper (Piper nigrum) growth on Tihpenfarm.

To determine the effects of weed pressure, the heightand percent cover of the most common weed in theTihpen pepper farm, the grass Paspa/um conjugatum, wasmultiplied together for each data period. The results arepresented in Fig. 2.

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Black pepper growth appears to be slightly favorablyinfluenced by the intercropping of C%casia taro (Fig. 1).

Fig.2. Weed pressure on Tihpen farm (weed volume ofPaspa/um conjugatum).

56

References Cited

Gnanaratnam, J. 1992. Pepper Technical Consultant,Pohnpei State Division of Agriculture.

Raynor, B. 1990. Taro (Colocasia esculenta (L.) Schott)Agriculture on Pohnpei Island: Pest and DiseaseOccurrence and Control. Paper presented at the ADAPCrop Protection Conference held in Guam on May 28­30, 1990. 10 pp.

1 USA PI - PohnpeijField Representative, The Nature ConselV8nc:y, P.O. Box 216, Pohnpei, FSM 96941.

57

The Editor

L. Ferentinos is the Project Coordinator of the Taro Production Systems Projec~ at the University ofHawai '-i at Manoa. ' ,

Jane C. Muench, an independent editor with J"C.M. Office Se~ces, provided technical support

Publication 'was supported in part by a grant from the USPA/CSRA Sustainable Agriculture Research andEducation Program (formerly called LJ.SA.). Additional support was provided by American SamoaCommunity College, College of Micronesia, Northern Marianas College, University ,of Guam~ Yap Instituteof Natural Science, and the University of Hawai' i under the Agricultural Development in the AmericanPacific (ADAP) Project. ~

All' reported opinions, conclusions, ,'and recommendations are those' of the authors (contractors) and notthose of the 'funding agency or the U-Ilited States government.

The Library of Congress has catalogued this serial publicationas follows:

85-645281AACR 2 MARC-S

[8500]Library of Congress

Research extension series / Hawaii Institute of Tropical Agri...culture and Human Resources.-O01-[Honolulu, Hawaii]:

The Institute, [1980-- v. : ill. ; 22 em.

Irregular.Title from cover.Separately catalogued and classified in LC before and

including no. 044.ISSN 0271-9916 = Research extension series .. Hawaii

Institute of Tropical Agriculture and Human Resources.1. Agriculture--Hawaii-Collected works. 2. Agricul",

ture--Research-Hawaii-:-Collected works. 1. HawaiiInstitute of Tropical Agriculture and Human Resources.II. Title: Research extension series .. Hawaii Institute ofTropical Agriculture and Human Resources.S52.5R47 630'.5"':"'dc19