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estimation of drought were determined from the daily rainfall data from these 75years.The detailed analysis of drought was done for a 25-y period by following theUniversal Hydrologic Equation to arrive at the weekly water balance (rainfall-potentialevapotranspiration). Because of the lack of data, however, the analysis did nottake into account the field-stored moisture. The drought analysis was done for theperiod between the 22nd and 43rd wk of the year (28 May to 28 Oct, 154 d duration),as upland rice crop cultivation and the monsoon in this region are confined to thisperiod. During the rice cultivation period, the duration and probability of droughtoccurrence were analyzed separately for three groups of 7 wk each: 22nd-28th wk,29th-35th wk, and 36th-42nd wk, termed as initial, intermediate, and terminal stagesof rice growth. Based on drought occurrence and severity analysis, on-station and onfarmexperiments were conducted on adjusting seeding dates to avoid drought in thelatter part of the growing season, selection of short-duration rice cultivars (similar totraditional ones) suitable for drought situations, and weed management and sowingmethods.Table 1 presents the results of the analyses, which indicate a higher probabilityof drought occurrence at the initial and terminal stages than at the intermediate stageof the crop. Drought affecting the crop at the initial and terminal stages of growth,Table 1. Selected monsoon and drought characteristics at Hazaribagh,Bihar, India.Monsoon characteristics aAmount or timeNormal annual rainfall (mm) 1,299Normal seasonal rainfall (mm) 1,169Probable annual rainfall (mm)At 99% probability 759At 20% probability 1,385Probable seasonal rainfall (mm)At 99% probability 666At 20% probability 1,385Monsoon onset (date)18 June (earliest 2 June,latest 6 July)Monsoon termination (date) 11 Oct (earliest 9 Sept,latest 28 Oct)Monsoon duration (d) 117 (shortest 77, longest 137)Seasonal drought duration b (wk)Initial stage (28 May to 3.7515 July)Intermediate stage (16 July 2.00to 17 Sept)Terminal stage (18 Sept 4.55to 28 Oct)a Period of analysis from 1913 to 1987 using rainfall data. b Period of analysisfrom 1972 to 1991 using rainfall and evapotranspiration data.Planning and managing rice farming through environmental analysis 197
however, depended on sowing time and the duration of the varieties used. Almost allfarms in the region experienced drought at the intermediate stage.Farmers in this region normally do final land preparation and sow rice in the3rd week of June after the onset of effective monsoon. This results in an avoidableloss of initial monsoon moisture to some extent and in delayed sowing in years ofcontinuous rains because of poor workability of the soil. In such cases, crops aremore likely to suffer from drought at the terminal stages of growth. Advance sowingbefore the onset of monsoon was therefore considered as one of the strategies foravoiding or minimizing the effects of terminal drought, which is of longer durationand has a higher probability of occurrence (Table 1). The other strategy in this respectwas to use the selected rice cultivars of short maturity duration (90–100 d) that hadshown consistently better performance in previous on-station and on-farm experiments.The results of advance sowing, done on around 7 June before the onset ofrains, indicated significantly higher grain yield, number of panicles m –2 , number offertile spikelets panicle –1 , and taller plants in all the genotypes tested than sowingdone around 22 June after the onset of rain (normal practice) (Table 2). Among thegenotypes, Brown Gora and Kalinga III were inferior to RR167-982 (Vandana) andRR165-1160 in all respects including panicle weight and panicle length (Table 2).The early sown plots, however, had a higher weed infestation at the early stagesof plant growth owing to the simultaneous emergence of weeds with rice upon thefirst rain showers. In normal sown plots, the weeds had germinated before rice seedingand were destroyed with the additional harrowing. Therefore, weed managementwas followed along with advance sowing in successive experiments that also includedseeding method and rice plant population studies.With advance sowing, grasses dominated the weed flora in the initial stages ofcrop growth followed by dicotyledons in the latter stages. The bulk of the weed floraconstituted Cyperus rotundus, Cyperus iria, Echinochloa colona, Cynodon dactylon,Setaria glauca, Commelina benghalensis, Aeschynomene indica, and Brachiariaramosa, which competed with rice during all its growth stages. The population ofAgeratum conyzoides was severe at the reproductive stage only. Losses in rice grainyield (difference between a weed-free and weedy plot) were as high as 77%, and werehigher in drilled than broadcast-seeded crops. However, when manually weeded at 20and 40 days after sowing, the drilled crop produced significantly higher yield (2.4 tha –1 ) than the manually weeded broadcast crop (2.0 t ha –1 ). Application of butachlorwith one handweeding was as effective as two handweedings in both systems.The initial 4-wk period of crop growth was crucial for weeding in the case ofearly maturing tall genotypes, such as Kalinga III, having poor early vigor in contrastwith the semitall genotypes, such as RR167-982 (Vandana) and Brown Gora, thathave higher early vigor and a suppressive effect on weeds.Plant population, attained using a seeding rate of 500 seeds m –2 or 112.5 kgha –1 , and closer row spacing (20 cm) also had a suppressive effect on weeds, as reflectedby lower weight of total weed dry matter. Rice grain and straw yields werehigher under these practices than using a higher or lower seeding rate (400 or 600seeds m –2 ) and sowing by broadcast or with wider row spacing (30 cm).198 Borkakati 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
Page 146 and 147: As Indonesia’s staple food, rice
Page 148 and 149: Soil and climate of rainfed lowland
Page 150 and 151: isky when the crop is planted late.
Page 152 and 153: The decrease in harvested area only
Page 154 and 155: than in tidal swamp rice, for which
Page 156 and 157: Monitoring rainfed and irrigated ri
Page 158 and 159: and, indirectly, methane emission f
Page 160 and 161: Radar backscatter (dB)-7ERS windsca
Page 162 and 163: ERS SAR imageseries2. RSpreprocessi
Page 164 and 165: Fig. 6. Supervised classification o
Page 166 and 167: ConclusionsMonitoring of rice crops
Page 168 and 169: Characterizing soil phosphorusand p
Page 170 and 171: Table 1. Area and distribution of s
Page 172 and 173: Table 2. Lowland area (ha) classifi
Page 174 and 175: Fig. 1. Extractable soil P map (25%
Page 176 and 177: Characterizing soil phosphorus and
Page 178 and 179: Table 4. Recommendations for P appl
Page 180 and 181: Fig. 4. Extractable soil K map of t
Page 182 and 183: Fig. 5. Extractable soil K map of t
Page 184 and 185: ● acidic pH (< 6)● low organic
Page 186 and 187: trials, K recommendations for uplan
Page 188 and 189: O’Brien DT, Blair G, Lefroy R. 19
Page 190 and 191: Planning and managing rice farmingt
Page 192 and 193: lowlands is submergence-prone. Ther
Page 194 and 195: situations and the allocation of re
Page 198 and 199: Table 2. Effect of date of sowing,
Page 200 and 201: from October to February and a summ
Page 202 and 203: Table 3. Promising areas for ground
Page 204 and 205: 1. There are possibilities of growi
Page 206 and 207: mmmm450350250150ASoil moisture useS
Page 208 and 209: Table 9. Yield a of preflood ahu (a
Page 210 and 211: 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
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included in these studies. Later st
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Average number of insects per sweep
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Table 2. Categorization of weed and
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Table 5. Properties of individual c
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ResultsRelations among pests and cr
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Start hereInterview farmers todocum
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Table 10. Information used to prior
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Interpreting the results of indepen
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level. Again, we augment our databa
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NotesAuthors’ address: Cambodia-I
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in soil nutritional status, especia
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flora. The range in elevation acros
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Table 1. Soil characteristics of th
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Table 3. Weed species recorded and
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Proportional abundance (log scale)%
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1.0Echi_colCype_iriMoll_penLind_spp
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+3.0Echi_cruMars_creEcli_albLept_ch
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indicates the need to deploy broad-
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ReferencesBangun P, Pane H, Jatmiko
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Socioeconomic characterization
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The role of characterizationin ex a
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ApproachThe following steps were ta
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PriceDS 0S 1P 0P 1dS 0S 1acbD0 Q 0Q
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Table 1. Ex ante assessment of rese
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Table 2 continued.Ranked byResearch
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Table 3. Research resource allocati
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NotesAuthors’ address: National C
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In addition to the unavailability o
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Socioeconomic constraintsFarm sizeF
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found that a higher rural labor sup
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Table 3. Rice area under HYVs from
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Rice varieties in farmers’ fields
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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
Page 464 and 465:
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
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Wade L. 1998. Nutrient research on
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