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level. Again, we augment our database through separate field collections. For example,rat damage is easily recognized, but only by trapping specimens have we beenable to determine which rat species are attacking RLR in Cambodia (Jahn et al 1999).Fourth, the quality of the data must also be considered. It is often difficult to distinguishdifferent types of pest damage. All of the cooperators joining us in data collectionhave undergone extensive training in identifying, quantifying, and recording pests/injuries of RLR. Still, there are bound to be mistakes when dealing with such a largedatabase. All the findings and predictions must be considered hypotheses that aresubject to more rigorous testing.ConclusionsNonparametric statistical techniques (Savary et al 1996) can be valuable tools forgenerating testable hypotheses (but not conclusions) on how cropping practices arerelated to pest levels, and how those pest levels are related to yield constraints. Nonparametricanalysis not only reveals associations and correlations but also helps ruleout factors as major constraints to rice production over a large area. For example,leaf-feeding insects did not constrain yields under any combination of cropping practicesif less than 33% of the leaves were damaged at the booting stage.The results of such analysis, however, are only a partial contribution to understandingbiotic yield constraints. Relations among pests and cropping practices cannotbe adequately described or even quantified simply based on statistical techniquesthat do not reveal causality. Nor can these nonparametric statistical techniques determinethe impact of pests on yields at the field or farm level, where research resultsmust ultimately be applied. Statistical descriptions of pest constraints should be interpretedin the context of the biology and ecology of the pest, the physical environment(e.g., soil type), economic and social conditions, the experience of rice farmers, andthe manner in which farmers react to perceived pest problems. The value of generatingtestable hypotheses by statistical techniques must be evaluated by the cost ofgathering such data, the reliability of such data, and the ultimate application of theanalysis.ReferencesCIAP (Cambodia-IRRI-Australia Project). 1996. Annual research report 1995. Phnom Penh(Cambodia): CIAP. 185 p.CIAP (Cambodia-IRRI-Australia Project). 1997. Annual research report 1996. Phnom Penh(Cambodia): CIAP. 177 p.CIAP (Cambodia-IRRI-Australia Project). 1998. Annual research report 1997. Phnom Penh(Cambodia): CIAP. 181 p.CIAP (Cambodia-IRRI-Australia Project). 1999. Annual research report 1998. Phnom Penh(Cambodia): CIAP. 205 p.Characterizing biotic constraints to production . . . 265
Cohen MB, Savary S, Huang N, Azzam O, Datta SK. 1998. Importance of rice pests and challengesto their management. In: Dowling NG, Greenfield SM, Fischer KS, editors.Sustainability of rice in the global food system. Davis, Calif. (USA): Pacific Basin StudyCenter, and Manila (Philippines): International Rice Research Institute. p 145-164.Cu RM, Mew TW, Cassman KG, Teng PS. 1996. Effect of sheath blight on yield in tropical,intensive rice production system. Plant Dis. 80(10):1103-1108.Jahn GC. 1992. Effect of neem oil, monocrotophos, and carbosulfan on green leafhoppers,Nephotettix virescens (Distant) (Homoptera: Cicadellidae) and rice yields in Thailand.Proc. Hawaiian Entomol. Soc. 31:125-131.Jahn GC, Cox P, Mak Solieng, Chhorn Nel, Tuy Samram. 1999. Rat management in Cambodia.In: Singleton G, Hinds L, Leirs H, Zhibin Zhang, editors. Ecologically-based rodentmanagement. Canberra (Australia): Australian Centre for International Agricultural Research.Jahn GC, Pheng S, Khiev B, Pol C. 1997. Pest management practices of lowland rice farmersin Cambodia. In: Heong KL, Escalada MM, editors. Pest management practices of ricefarmers in Asia. Manila (Philippines): International Rice Research Institute. p 35-51.Jahn GC, Pheng S, Khiev B, Pol C. 1998. Pest potential of the golden apple snail in Cambodia.Cambodian J. Agric. 1:34-35.Javier E. 1997. Rice ecosystems and varieties. In: Nesbitt HJ, editor. Rice production in Cambodia.Manila (Philippines): International Rice Research Institute. p 39-81.Khiev B, Jahn GC, Pol C, Chhorn N. 1999. Simulating rice pest damage to determine effectson yield. Cambodian J. Agric. 2(1):29-32.Kirk GJD, Dobermann A, Ladha JK, Olk DC, Roetter R, Tuong TP, Wade L. 1998. Research onnatural resources management: strategic research issues and IRRI’s approach to addressingthem. IRRI Discussion Paper Series No. 27. Manila (Philippines): International RiceResearch Institute. 28 p.Pheng S, Adkins S, Olofsdotter M, Jahn GC. 1999. Allelopathic effects of rice (Oryza sativaL.) on the growth of awnless barnyard grass [Echinochloa colona (L.) Link]: a new formfor weed management. Cambodian J. Agric. 2(1):42-49.Satake T, Yoshida S. 1978. High temperature induced sterility in indica rice at flowering. Jpn.J. Crop Sci. 47:6-17.Savary S, Madden LV, Zadoks JC, Klein-Gebbinck HW. 1995. Use of categorical informationand correspondence analysis in plant disease epidemiology. In: Advances in botanicalresearch. Vol. 21. London: Academic Press Limited. p 213-240.Savary S, Elazegui FA, Teng PS. 1996. A survey portfolio for the characterization of rice pestconstraints. IRRI Discussion Paper Series No. 18. Manila (Philippines): InternationalRice Research Institute. 32 p.Sheehy JE, Mitchell PE, Beerling DJ, Tsukaguchi T, Woodward FI. 1998. Temperature of ricespikelets: thermal damage and the concept of a thermal burden. Agronomie 18:449-460.Teng PS, Bissonnette HL. 1985. Developing equations to estimate potato yield loss caused byearly blight in Minnesota. Am. Potato J. 62:607-618.266 Jahn et al
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The International Rice Research Ins
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Monitoring rainfed and irrigated ri
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ForewordRainfed rice areas are asso
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AcknowledgmentsIRRI is most gratefu
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2 Singh et al
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development, for example, provision
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subecosystems were recognized withi
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Table 3. Methods commonly used in e
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Table 4 continued.Scale of analysis
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Table 4 continued.Scale of analysis
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This included standard countrywide
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deepwater rice ecosystems. The rese
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Table 5 continued.Main MethodologyC
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Table 5 continued.Main MethodologyC
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Table 5 continued.Main Scale presen
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levels of involvement. For example,
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●●●ecosystem classifications
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Conclusionsclearly that they are di
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IRRI (International Rice Research I
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Widawsky DA, O’Toole JC. 1990. Pr
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Rice is the staple food crop for mo
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first working group to identify the
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TropicsSubtropicsTemperateSummer/wi
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ferred it for wide adoption by farm
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ing, remote sensing, and computing
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ice environments will be needed to
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Insects and diseasesInsects and dis
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The completeness of characterizatio
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Table 7. Levels and scales for agro
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Jamin JY, Andriesse W. 1993. Discus
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Tools and methodologiesfor biophysi
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Effect of climate, agrohydrology,an
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to water deficit because the crop
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for different periods of the year:
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depth scenarios (shallow, medium, a
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Water table depth (cm)500Shallow wa
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Simulated yield (kg ha -1 )6,0005,0
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Perception, understanding,and mappi
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and rice yield at regional or more
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SubareaSampling sites:GridTransectR
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was approximately 2,000 m with a to
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kg -1 in 50% of the topsoil and sub
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Table 3. Class medians were calcula
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Hard point dataClay, silt, sandHard
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A. Silt (%) B. 0.5 ccdfC. 0.2 ccdf
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In summary, the chosen geostatistic
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elated over slightly longer distanc
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Miura K. 1990. Genetic features of
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Rainfed lowland rice, growing with
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tively. In 1993, following dry till
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Rainfall (mm)Water table depth (cm)
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Saturated hydraulic conductivity (c
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in the uncompacted C0 plots (6.7 wk
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Clay classified≤ 2% 50 ha (2% but
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NotesAuthors’ addresses: D. Harnp
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target area of a breeding program.
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which is calculated from the estima
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hence grain yield. The three major
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ainfall data for each location. Mea
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such as 1980 and 1996, yield was hi
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Table 1 shows the results of the se
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Grain yield (t ha -1 )3UBN 19942103
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decreased with the use of old seedl
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The use of five genotypes with diff
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Mackill DJ, Coffman WR, Garrity DP.
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In rainfed agriculture, crop perfor
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GrainSite Year Code Group yield San
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Criteria considered for selecting r
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Table 1. Characteristics of the ref
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equired as the quality of the repro
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Cooper M, Rajatasereekul S, Immark
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144 Amien and Las
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As Indonesia’s staple food, rice
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Soil and climate of rainfed lowland
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isky when the crop is planted late.
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The decrease in harvested area only
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than in tidal swamp rice, for which
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Monitoring rainfed and irrigated ri
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and, indirectly, methane emission f
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Radar backscatter (dB)-7ERS windsca
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ERS SAR imageseries2. RSpreprocessi
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Fig. 6. Supervised classification o
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ConclusionsMonitoring of rice crops
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Characterizing soil phosphorusand p
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Table 1. Area and distribution of s
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Table 2. Lowland area (ha) classifi
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Fig. 1. Extractable soil P map (25%
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Characterizing soil phosphorus and
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Table 4. Recommendations for P appl
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Fig. 4. Extractable soil K map of t
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Fig. 5. Extractable soil K map of t
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● acidic pH (< 6)● low organic
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trials, K recommendations for uplan
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O’Brien DT, Blair G, Lefroy R. 19
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Planning and managing rice farmingt
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lowlands is submergence-prone. Ther
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situations and the allocation of re
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estimation of drought were determin
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Table 2. Effect of date of sowing,
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from October to February and a summ
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Table 3. Promising areas for ground
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1. There are possibilities of growi
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mmmm450350250150ASoil moisture useS
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Table 9. Yield a of preflood ahu (a
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Grain yield (t ha -1 )6Farmers’ l
Page 212 and 213: ReferencesIRRI (International Rice
Page 214 and 215: network (Sastry 1976). Temperature
Page 216 and 217: Temperature (°C) and solar radiati
Page 218 and 219: Table 1. Characterization of rainfa
Page 220 and 221: in eastern Uttar Pradesh under norm
Page 222 and 223: fluctuations/variations in rainfall
Page 224 and 225: the desirable rainfall period at 50
Page 226 and 227: The radiation values range from les
Page 228 and 229: not affect the growth and developme
Page 230 and 231: Agrohydrologic and drought riskanal
Page 232 and 233: Analytical procedureThe nature and
Page 234 and 235: late because of low rainfall at the
Page 236 and 237: Probability (%)10080604020Vegetativ
Page 238 and 239: 15 August), which may happen twice
Page 240 and 241: texture), then once in two years (5
Page 242 and 243: Characterizing biotic stresses
Page 244 and 245: Characterizing biotic constraintsto
Page 246 and 247: included in these studies. Later st
Page 248 and 249: Average number of insects per sweep
Page 250 and 251: Table 2. Categorization of weed and
Page 252 and 253: Table 5. Properties of individual c
Page 254 and 255: ResultsRelations among pests and cr
Page 256 and 257: Start hereInterview farmers todocum
Page 258 and 259: Table 10. Information used to prior
Page 260 and 261: Interpreting the results of indepen
Page 264 and 265: NotesAuthors’ address: Cambodia-I
Page 266 and 267: in soil nutritional status, especia
Page 268 and 269: flora. The range in elevation acros
Page 270 and 271: Table 1. Soil characteristics of th
Page 272 and 273: Table 3. Weed species recorded and
Page 274 and 275: Proportional abundance (log scale)%
Page 276 and 277: 1.0Echi_colCype_iriMoll_penLind_spp
Page 278 and 279: +3.0Echi_cruMars_creEcli_albLept_ch
Page 280 and 281: indicates the need to deploy broad-
Page 282 and 283: ReferencesBangun P, Pane H, Jatmiko
Page 284 and 285: Socioeconomic characterization
Page 286 and 287: The role of characterizationin ex a
Page 288 and 289: ApproachThe following steps were ta
Page 290 and 291: PriceDS 0S 1P 0P 1dS 0S 1acbD0 Q 0Q
Page 292 and 293: Table 1. Ex ante assessment of rese
Page 294 and 295: Table 2 continued.Ranked byResearch
Page 296 and 297: Table 3. Research resource allocati
Page 298 and 299: NotesAuthors’ address: National C
Page 300 and 301: In addition to the unavailability o
Page 302 and 303: Socioeconomic constraintsFarm sizeF
Page 304 and 305: found that a higher rural labor sup
Page 306 and 307: Table 3. Rice area under HYVs from
Page 308 and 309: Rice varieties in farmers’ fields
Page 310 and 311: Table 9. Constraints for low adopti
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vehicle for realizing the untapped
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Parthasarathy G, Prasad DS. 1978. R
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Appendix. Agroclimatic zones of Bih
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such that losses are reduced during
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P = 0.5 R [a 2 C r2+ 2 a (1 - a) g
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and Itgaon, however, the plot-level
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espectively, to farmers’ income.
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Factors determining the adoption of
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mining whether or not modern variet
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irrigation schemes in the study are
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Using gender analysis in characteri
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lytical tool used to identify or di
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However, household members have cer
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Table 1. Village characteristics of
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taking care of dairy cattle. On the
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The biophysical environmentThe perf
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Table 3. Seasonal calendar and gend
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Table 4. Crops grown during the kha
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Table 7. Labor input (person-days h
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Table 8. Labor input (person-days h
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Table 10. Cost and returns of rice
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Gender roles in animal husbandryWhe
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farm activities, 25% in nonfarm act
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for rice but also for cash crops su
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Table 15. Access to agricultural in
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Hossain M. 1995. Recent development
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Agricultural commercializationand l
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Conceptual frameworkPopulation pres
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tional average of 18% 1 , and most
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The Dzao live in medium-altitude ar
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Table 1. Selected districts and com
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Table 2. General characteristics of
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markets for their food needs. With
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ther “extensification” in the u
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the productivity of lowland rice ca
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Boserup E. 1981. Population and tec
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Economics of intensive rainfed lowl
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Area (ha)50,00040,000Irrigated30,00
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The economic characterization and i
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Table 1. Rice varieties planted (19
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Table 4. Yield and input use of maj
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TFP, output and input indices200160
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Lynam JK, Herdt RW. 1989. Sense and
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406 Garcia et al
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Increased rice production had alway
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Table 1. Total rice area, average y
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use of water by avoiding seedbed pr
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water often brought with it a varie
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Table 4. Distribution of farm house
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Soil types found in the villages we
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Table 10. Ownership of agricultural
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in a group) at the rate of $60 per
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Table 13. Pattern of loan use (% of
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Labor and employmentTable 16 presen
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Table 17. Incidence of child labor
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Cumulative proportion of income1.04
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Table 21. Cost and return analysis
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Table 22. Estimated rice yield and
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were often burned for disease contr
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landless population reaching 50-60%
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Integration of biophysical andsocio
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opinion regarding what socioeconomi
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1995-96 Rice production (t)TvRd6Rd1
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Farm-gate price of agricultural goo
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ming the distance of all line segme
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Description of the study areaWe com
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Table 1 continued.Variable Unit1994
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CambodiaFig. 4. Main transport rout
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Table 2. Accessibility indicators f
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ice and the model is applied to exp
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Table 3. Summary of estimates of la
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estimation of a system of multinomi
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The availability of low-saline irri
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Table 5. Simulation of effects of i
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NotesAuthors’ address: Social Sci
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that they synthesize fragmented agr
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Framework for exploratory and predi
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and quantify the spatial distributi
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Seventeen different agricultural pr
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self-sufficiency in rice production
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al warming since maintaining or cre
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eturns to purchased inputs due to u
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Francisco SR, Navarrete Jr. RL, Dim
Page 478:
Wade L. 1998. Nutrient research on
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