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Rainfed lowland rice, growing with an average yield of only 1.5 t ha –1 on some 4.5million ha of coarse-textured and low-fertility soils in northeastern Thailand, maysuffer from water stress as soon as rains are interrupted for about 1 wk (Sharma 1992).Percolation rate can be as high as a few centimeters d –1 . Puddling is not fully effectivedue to high sand content. Efficient management of rainwater and nutrients is a keyfactor in improving the productivity and stability of rice. On-station experiments,carried out at the Ubon Ratchathani Rice Research Center on a soil in the Ubon serieswith a clay content of 12% in the subsoil (30–60 cm), showed that water- and nutrient-useefficiency may be improved by reducing percolation through the creation of asubsurface barrier (Garrity et al 1992). Subsequent field-oriented research to identifypractical and cost-effective techniques for decreasing subsoil permeability showedthat multiple passes of a 12-t conventional road roller with vibration action (DynapacCA25) that compacts the subsoil to 75-cm depth was most effective (Sharma et al1995a,b, Trébuil et al 1998). As subsoil compaction was observed to concentrate riceroots in the plow layer above the compacted zone, a deeper (15–20 cm) tillage depththan the one currently achieved in farmers’ fields (7–10 cm) was found to be desirable.All previous studies were carried out at the experiment station of the Ubon RiceResearch Center. The effects of subsoil compaction across a range of subsoil claycontents have not been investigated, and the combined effects of soil compaction andgreen manuring have not been investigated either.The objectives of the on-farm study were1. To quantify the effects of subsoil compaction and tillage depth on changes insandy soil physical and hydrological properties across a range of subsoilclay contents.2. To quantify the interactions between subsoil compaction and green manurefertilization and their effects on the productivity of rainfed lowland rice.3. To define soil suitability for subsoil compaction by using geographic informationsystems (GIS) techniques applied to the Ubon Ratchathani Land ReformArea.Materials and methodsExperimental siteTwo-factor on-farm field experiments were conducted in the 1993 and 1994 wet seasonsin Ban Klang and Ban Mak Mai villages of Klang subdistrict of Det UdomDistrict, Ubon Ratchathani Province, lower northeast Thailand. The experimental sandysoils (Table 1) belonged to the Nam Phong series and were acidic, low in organicmatter content and available N, P, and K, and with a high concentration of ferrousiron in some fields.Experimental treatmentsWe selected seven farmers’ fields for this study. The elementary experimental plotsize varied from 100 to 200 m 2 . Each plot was surrounded by a single levee, approximately20 cm high and 40 cm wide.98 Harnpichitvitaya et al
Table 1. Properties of the experimental soils belonging to the NamPhong series in Det Udom District, Ubon Ratchathani Province, 1993wet season.Soil parameter Range MeanParticle size distribution: 0–30 cm (%)Sand 88.2–94.6 90.9Silt 3.6– 9.4 6.5Clay 1.7– 3.6 2.6Particle size distribution: 30–60/70 cm (%)Sand 88.0–95.4 91.2Silt 3.1–10.3 6.7Clay 1.4– 4.5 2.1Chemical parameters: 0–30 cmpH (1:1) 3.9– 5.2 4.2Organic matter content (%) 0.39–1.79 0.85Total N (%) 0.02–0.08 0.04Extractable P (Bray II, ppm) 6.1–19.0 9.8Extractable K (ammoniumacetate, pH 7, ppm) 5.0–12.6 8.6CEC (meq 100 g –1 ) 0.32–1.28 0.83In the 1993 wet season (WS), the following three subsoil compaction and tillagetreatments were imposed in each of the selected fields (but without replications ineach field):●●C0 = uncompacted dry tillage; soil was disc-plowed dry to 7–10-cm depth.C1 = subsoil compacted by 10 passes of a 12-t Dynapac vibrating road rolleron 19 or 23 May 1993 (with soil moisture brought close to field capacity byusing a watering truck), followed by dry tillage to 7–10-cm depth.● C2 = subsoil compacted as above but with dry tillage to 15–20-cm depth.In the 1994 WS, we selected the C0 and C1 plots of six farmers’ fields, allhaving been included in the previous year’s on-farm experiment. C2 plots were notincluded because the tillage treatment did not show any effects on the monitoredparameters in 1993. Each plot was further divided into two to accommodate a splitplotdesign, with the main and subplot treatments as follows:●●Main plots:C0 = uncompacted with shallow (7–10 cm) dry tillage.C1 = compacted with shallow dry tillage (plots were not compacted again in1994).Subplots:F0 = no green manure before rice (control treatment).F1 = with green manure before rice.Cultural practicesThe experimental cultivars were the similar and widely grown photoperiod-sensitive,medium-tall KDML105 and RD6 during the 1993 and 1994 wet seasons, respec-Identifying soil suitability for subsoil compaction . . . 99
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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
Page 48 and 49: ferred it for wide adoption by farm
Page 50 and 51: ing, remote sensing, and computing
Page 52 and 53: ice environments will be needed to
Page 54 and 55: Insects and diseasesInsects and dis
Page 56 and 57: The completeness of characterizatio
Page 58 and 59: Table 7. Levels and scales for agro
Page 60 and 61: Jamin JY, Andriesse W. 1993. Discus
Page 62 and 63: Tools and methodologiesfor biophysi
Page 64 and 65: Effect of climate, agrohydrology,an
Page 66 and 67: to water deficit because the crop
Page 68 and 69: for different periods of the year:
Page 70 and 71: depth scenarios (shallow, medium, a
Page 72 and 73: Water table depth (cm)500Shallow wa
Page 74 and 75: Simulated yield (kg ha -1 )6,0005,0
Page 76 and 77: Perception, understanding,and mappi
Page 78 and 79: and rice yield at regional or more
Page 80 and 81: SubareaSampling sites:GridTransectR
Page 82 and 83: was approximately 2,000 m with a to
Page 84 and 85: kg -1 in 50% of the topsoil and sub
Page 86 and 87: Table 3. Class medians were calcula
Page 88 and 89: Hard point dataClay, silt, sandHard
Page 90 and 91: A. Silt (%) B. 0.5 ccdfC. 0.2 ccdf
Page 92 and 93: In summary, the chosen geostatistic
Page 94 and 95: elated over slightly longer distanc
Page 96 and 97: Miura K. 1990. Genetic features of
Page 100 and 101: tively. In 1993, following dry till
Page 102 and 103: Rainfall (mm)Water table depth (cm)
Page 104 and 105: Saturated hydraulic conductivity (c
Page 106 and 107: in the uncompacted C0 plots (6.7 wk
Page 108 and 109: Clay classified≤ 2% 50 ha (2% but
Page 110 and 111: NotesAuthors’ addresses: D. Harnp
Page 112 and 113: target area of a breeding program.
Page 114 and 115: which is calculated from the estima
Page 116 and 117: hence grain yield. The three major
Page 118 and 119: ainfall data for each location. Mea
Page 120 and 121: such as 1980 and 1996, yield was hi
Page 122 and 123: Table 1 shows the results of the se
Page 124 and 125: Grain yield (t ha -1 )3UBN 19942103
Page 126 and 127: decreased with the use of old seedl
Page 128 and 129: The use of five genotypes with diff
Page 130 and 131: Mackill DJ, Coffman WR, Garrity DP.
Page 132 and 133: In rainfed agriculture, crop perfor
Page 134 and 135: GrainSite Year Code Group yield San
Page 136 and 137: Criteria considered for selecting r
Page 138 and 139: Table 1. Characteristics of the ref
Page 140 and 141: equired as the quality of the repro
Page 142 and 143: Cooper M, Rajatasereekul S, Immark
Page 144 and 145: 144 Amien and Las
Page 146 and 147: 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
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ReferencesIRRI (International Rice
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network (Sastry 1976). Temperature
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Temperature (°C) and solar radiati
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Table 1. Characterization of rainfa
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in eastern Uttar Pradesh under norm
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fluctuations/variations in rainfall
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the desirable rainfall period at 50
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The radiation values range from les
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not affect the growth and developme
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Agrohydrologic and drought riskanal
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Analytical procedureThe nature and
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late because of low rainfall at the
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Probability (%)10080604020Vegetativ
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15 August), which may happen twice
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texture), then once in two years (5
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Characterizing biotic stresses
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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
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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
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Wade L. 1998. Nutrient research on
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