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Percolation losses of water in relation to puddling intensity and depth in a sandy loam rice (Oryza sativa) field
Agricultural Water Management 57 (2002) 49–59
Percolation losses of water in relation to puddling intensity and depth in a sandy loam rice (Oryza sativa) field S.S. Kukal*, G.C. Aggarwal Department of Soils, Punjab Agricultural University, Ludhiana, Punjab 141004, India Accepted 19 March 2002
Abstract Percolation loss of water in rice fields is a major factor of low water use efficiency of irrigated rice thus threatening its sustainability. The process of water percolation was studied in a puddled sandy loam rice field with three puddling intensities—no puddling (unpuddled), two passes of tractor-drawn cultivator þ one planking (medium-puddling), and four passes of tractor-drawn cultivator þ one planking (high-puddling), each at shallow (5–6 cm) and normal (10–12 cm) depths. Percolation losses of water decreased with medium-puddling by 54–58%, but it remained unaffected by increased puddling intensity and puddling depth. Percolation rate (PR) decreased with time with both medium- and highpuddling but it increased with increased depth of ponding water. The PR of water recorded in infiltration rings was 1.8, 38.8 and 42.1% less than that recorded in the whole plots thereby indicating the role of under-bund losses. Seepage ratio (ratio of seepage plus percolation to percolation alone) increased with increase in puddling intensity indicating that the magnitude of under-bund percolation was a direct function of puddling intensity. The hydraulic conductivity of the puddled layer decreased with increased puddling intensity (0.064 cm h1 with medium-puddling to 0.009 cm h1 with high-puddling) whereas the hydraulic gradient between puddled and unpuddled layers increased with increase in puddling intensity (0.84 cm cm1 with medium-puddling to 1.86 cm cm1 with high-puddling) # 2002 Elsevier Science B.V. All rights reserved. Keywords: Rice; Percolation rate; Puddling depth; Puddling intensity; Under-bund percolation
1. Introduction Puddling rice (Oryza sativa L.) soils before transplanting reduces percolation losses (Sharma and De Datta, 1985; Humphreys et al., 1992) by eliminating large pores and * Corresponding author. Tel.: þ91-161-401-960; fax: þ91-161-400-945. E-mail address: [email protected] (S.S. Kukal).
0378-3774/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 7 7 4 ( 0 2 ) 0 0 0 3 7 - 9
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S.S. Kukal, G.C. Aggarwal / Agricultural Water Management 57 (2002) 49–59
thereby decreasing the hydraulic conductivity of soils. Puddling usually comprises plowing in 7–10 cm deep standing water followed by planking with the help of a wooden/iron leveler. The extent of percolation reduction depends on puddling intensity (Aggarwal et al., 1995), puddling depth (Sharma and Bhagat, 1993), time after puddling, soil type (Singh and Wichkam, 1977), ponding water depth (PWD) (Tabbal et al., 1992) and of course the experimental conditions. The percolation rate (PR) of a sandy loam soil decreased from 14 mm per day with low-puddling (one pass of plowing followed by planking) to 10 mm per day with high-puddling ( four passes of plowing followed by one planking) (Aggarwal et al., 1995). Sharma and Bhagat (1993) reported in a column study that there was a nonlinear reduction in water flux through soils with an increase in puddling depth. The PR decreased linearly with the thickness of the clay layer, whereas Sandhu (1995) in a column study concluded that puddling intensity was more effective than puddling depth in controlling PR in coarse to fine textured soils. However, information on effect of puddling depth on PR under field conditions seems to be lacking. Depth of flooding increased the percolation of somewhat porous, non-swelling soils but reduced the permeability of lowpercolating soils (Singh and Wichkam, 1977). Tabbal et al. (1992) reported a decrease in PR from 20 mm per day under 2–5 cm PWD to 9 mm per day in the continuously saturated regime (PWD ¼ 0 cm) in a clay loam soil whereas Ferguson (1970) reported only a slight increase in percolation loss with increasing water depth. Hardjoamidjojo (1992) reported PR of 2.8, 2.8 and 3.8 mm per day under PWD of 2.5, 5.0 and to 7.5 cm, respectively in a clay textured and fine structured soil. The diversity in research results is due to differences in experimental conditions. Because of high spatial variability of PR, interpretations and extrapolation of results becomes difficult (Wopereis et al., 1992a). Process-oriented research is thus needed to explain the differences in a mechanistic way. Most studies considered the loss through the puddled soil in the field within the surrounding bunds as the only source of percolation loss. Walker and Rushton (1984) reported field results where water balance could not be achieved if it was assumed that only evapotranspiration and vertical percolation through the puddled layer were contributing to water loss. If runoff and seepage losses from one field are a gain to the adjacent field, the only other possible water loss is leakage through areas under inter-plot bunds. This under-bund percolation (IRRI, 1987; Painuli et al., 1988) can be a very important factor adding to percolation losses in puddled rice fields (Tuong et al., 1994). The present study was conducted to observe the process of percolation losses in rice fields in relation to puddling intensity, puddling depth, PWD and under-bund percolation.
2. Materials and methods Field experiments on rice (Oryza sativa) were conducted for 3 years (1994–1996) at Punjab Agricultural University Research Farm, Ludhiana (India), with three puddling intensities i.e. unpuddled, medium (two passes of tractor-drawn cultivator followed by one planking) and high (four passes of tractor-drawn cultivator followed by one planking). Both medium and high-puddling were carried-out at shallow (5–6 cm) and normal (10–12 cm) depths, replicated four times in randomised block design in 22 m 1:8 m plots. The experiment was repeated at the same site and same layout for all the three years.
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Table 1 Physico-chemical characteristics of the study soil Soil properties
Sand (%) Silt (%) Clay (%) pH Bulk density (Mg m3) Electrical conductivity (m mhos) Water content (%, w/w) 0.3 bar Water content (%, w/w) 0.5 bar
Profile depth (cm) 0–15
15–30
30–60
60–90
78 13 9 8.0 1.50 0.28 10.7 6.2
76 14 10 8.1 1.52 0.20 10.2 6.8
68 18 14 7.9 1.54 0.18 14.4 8.6
68 18 14 7.9 1.57 0.18 14.4 8.7
The experimental site is located at 308560 N latitude and 758520 E longitude, is 247 m above mean sea level, and is characterised by a sub-tropical and semi-arid climate with hot and dry summers (March–June) and severe winters (December–January). The area experiences an average rainfall of about 700 mm of which 80% is received during July–September coinciding with the rice season whereas the remaining 20% is received during rabi (November–April) season. Maximum air temperature during three rice seasons ranged between 33:6 1:3 8C (July) and 31:5 1:4 8C (October), and minimum air temperature was between 26:6 0:6 8C (July) and 16:4 1:5 8C (October). Mean per cent relative humidity during rice seasons varied between 76 5:3 (July) and 63 4:1 (October). The soils of the area have developed from alluvium of Pleistocene to recent times under moisture regime. The experimental soil is deep alluvial sandy loam soil (USDA: Typic ustochrept) The physico-chemical characteristics of the experimental soil are given in Table 1. The soil is low in organic carbon (3.3 g kg1), low in KMnO4-extractable N (152 kg N ha1), medium in 0.5 N NaHCO3-extractable P (13.7 kg ha1) and medium in available K (145 kg ha1). The field was cultivated in order to remove the stubbles and the land was flooded with 8–10 cm water. Puddling was done in each plot as per treatments mentioned. Basal doses of zinc sulphate, superphosphate and one-third of total N fertilizer were applied in two equal installments at 3 and 6 weeks after transplanting. All the plots were kept flooded for the first 15 days. Ponded water levels were recorded daily with a hook gauge before applying measured amounts of water, to ensure 5 cm submergence. Afterwards, all the irrigations (each of 7.5 cm amount) were applied 2 days after the drainage of ponded water (Sandhu et al., 1980). Depth of water applied was also recorded with a hook gauge from a levelled and fixed platform in each plot. PR were monitored from data on water levels and evaporation from open pan located in the irrigated area surrounded by rice paddies. PR for various rice cropping seasons (1994–96) were estimated by the sum of total irrigation water applied (I) and cropping season rainfall (P) minus the cumulative pan evaporation (PE) divided by the duration of crop growing season (d). A metal ring with a diameter of 40 cm and a height of 35 cm was pushed into the soil at four points to a depth of approximately 15 cm in the centre of each plot to study the process of percolation losses in the absence of under-bund movement of water. The rate of infiltration into each column was monitored
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throughout a 24 h period. The water level inside the ring was maintained with that outside in the whole plot. The tensiometers were installed at 5–10 and 10–15 cm soil depths both in the centre of the experimental plots (under normal depth of puddling) and in the inter-plot bunds (at the same depths as in plots) to monitor soil water potential status. These were fabricated indigenously using ceramic cup at the bottom of a PVC pipe fitted with a mercury manometer. The whole system was made air-tight so as to maintain the continuity of water column in the system. The height of rise of mercury column (ZHg) was measured and related to soil matric potential (cm) as: cm ¼ 12:6 Z Hg þ Z0 , whereas Z0 is distance between center of ceramic cup to the surface of mercury in the reservoir. Using Darcy’s Law, the hydraulic conductivity of the puddled layer was calculated corresponding to PWD of 7 cm. Also, the hydraulic head gradient between puddled (5–10 cm) and unpuddled (10–15 cm) soil layers was determined. The hydraulic conductivity of puddled layers and the hydraulic gradient between puddled and unpuddled layers were determined for unpuddled, medium-puddling, high-puddling and under-bund conditions.
3. Results and discusion 3.1. Percolation rate The mean PR decreased with puddling during all 3 years of the study (Table 2). It decreased by 55, 54 and 58% in 1994, 1995 and 1996, respectively with medium-puddling from that in unpuddled plots. However, high-puddling intensity did not significantly decrease PR any further, compared to medium-puddling despite of the fact that sediment density of soil–water suspension immediately after puddling was more (0.271 Mg m3) with high-puddling than that with medium-puddling (0.169 Mg m3). This shows that finer particles at the top of the graded layers brought in suspension by medium-puddling were sufficient to decrease the permeability of the surface soil and thus decreasing the PR. Further increase in sediment density of the suspension did not affect the PR. Bouwer et al. Table 2 Effect of puddling intensity and depth on average PR during 1994–96 Treatments
PR (cm per day) 1994
1995
1996
Mean
Puddling intensity Unpuddled Medium-puddled High-puddled LSD (0.05)
2.96 1.32 1.30 0.38
2.98 1.36 1.25 0.38
3.10 1.31 1.16 0.20
3.01 1.32 1.19
Puddling depth Shallow Normal LSD (0.05)
1.21 1.34 NS
1.28 1.22 NS
1.28 1.22 NS
1.26 1.26
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(2001) observed in a column study that the graded sediment layer with coarsest particles on the bottom and the finest particles on top gives more seepage control than even a uniform compact layer. Although, well-controlled studies in microplots (Wopereis et al., 1992b) and in laboratories (Adachi, 1992) showed that puddling reduced PR by 500–1000 times, most field studies report a reduction of less than five times (Humphreys et al., 1992 ; Aggarwal et al., 1995). No significant differences were observed between PR of shallow and normal puddled plots. Thus, puddling done both at shallow and normal depths was equally effective in checking percolation losses. This confirms the observation of Sandhu (1995) in a column study that puddling intensity was more effective than puddling depth in checking percolation losses in coarse to fine textured soils. 3.2. Temporal changes in percolation rate In unpuddled soils, the PR remained more or less unchanged with time but in puddled soils, it decreased with time (Fig. 1). The PR with medium-puddling was about 2.15 cm per day at 2 days after transplanting (DAT) and it decreased by 35% at 50 DAT in 1995 (Fig. 1a). With high-puddling, the PR decreased from 1.70 cm per day at 2 DAT to 1.0 cm per day at 50 DAT. During 1996, the corresponding values were 2.1 and 1.35 cm per day with medium-puddling (Fig. 1b) and 1.7 and 0.95 cm per day for the same days with highpuddling. Painuli et al. (1988) observed that the PR was high initially and decreased with the passage of time. This is attributed to the clogging of the pores in the top layer by the settling of fine particles in suspension, by algal growth and root effects (Prihar et al., 1976; Reddy, 1982). Almost no decrease in PR in unpuddled fields can be due to negligible suspension and hence settling of finer soil particles at the surface. It shows that settling and subsequent sealing by finer particles of suspension are mainly responsible for the decrease in PR with time. 3.3. Ponding water depth and percolation The change in PR during an irrigation cycle is depicted in Fig. 2. Immediately after applying irrigation water to a depth of 10 cm in 1995, the PR was 3.70 cm per day after the first day of ponding in unpuddled soil (Fig. 2a) and decreased to nearly 2.0 cm per day on the fourth day of ponding when the PWD was 2.1 cm. In the case of medium-puddling, the PR decreased from 1.6 cm per day after the first day of ponding (PWD ¼ 10 cm) to 1.0 cm per day on the fourth day when the PWD was 5.6 cm. With high-puddling, the PR decreased from 1.3 cm per day (PWD ¼ 10 cm) to 0.9 cm per day (PWD ¼ 6:2 cm) for the same days. A similar trend was observed during 1996 (Fig. 2b). Initially, when the PWD was 10 cm, the PR was high in all the puddling treatments. However, as the PWD decreased due to infiltration of water, PR also decreased. This indicates that a substantial amount of water can be saved if shallow PWDs are maintained in sandy loam rice fields. Tuong et al. (1994) observed that a 10-fold increase in PWD (from 1 to 10) changed the PR from 2.75 to 3.25 cm per day. Shallow PWD reduces the wetted area of inter-plot bunds and limits the amount of water infiltrating laterally into the bunds. Furthermore, if the PWD is kept very low or if the field is maintained at saturation point, the water loss is greatly reduced because
54 S.S. Kukal, G.C. Aggarwal / Agricultural Water Management 57 (2002) 49–59
Fig. 1. Effect of puddling intensity on seasonal changes in percolation rate in (a) 1995 and (b) 1996.
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Fig. 2. Effect of puddling intensity on percolation rate immediately after irrigation during (a) 1995 and (b) 1996.
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Table 3 Effect of puddling intensity on PR from whole plots and infiltration rings for all puddling intensities Puddling intensity
Unpuddled Medium-puddled High-puddled
PR (cm per day) Whole plot
Infiltrometer rings
Decrease (%)
Seepage ratio
2.81 1.47 1.33
2.76 0.90
1.8 38.8 0.70
1.02 1.63
the unevenness of the soil surface prevents water movement to the bunds and subsequent loss through under-bunds (Tabbal et al., 1992). 3.4. Under-bund percolation The PR recorded in the whole plot was more than that recorded in infiltration rings for all puddling intensities (Table 3). The PR recorded in infiltration rings were 1.8, 38.8 and 42.1% less than those recorded in whole plots for unpuddled, medium- and high-puddling treatments, respectively. This difference in PR recorded in rings and whole plots could be due to lateral movement of water from whole plots through inter-plot bunds which remained unpuddled (Fig. 3). This type of movement (seepage), however, was not possible from infiltration rings. Thus, the water loss from the whole plots consisted of two components, i.e. percolation (vertical) and seepage (lateral), whereas the water loss recorded in the infiltrometer rings was due to percolation only. This seepage water was lost as under-bund percolation despite of the fact that the surface of the bunds was plastered with puddled soil, which is a common practice with the farmers of the region. In fact, the puddled soil used for plastering is taken from inside the field (Fig. 3) in close proximity of the bunds. This exposes the unpuddled spots along the bunds inside the field and hence the water starts seeping laterally through these spots as shown in Fig. 3. Tuong et al. (1994) observed that a small area of non-puddled soil increased field percolation losses by a factor 5 and under-bund percolation caused a further 2–5-fold increase depending on the size of the field. This under-bund percolation is thus an important factor that determines percolation loss in puddled rice fields (IRRI, 1987; Painuli et al., 1988). Walker and Rushton (1984) identified under-bund percolation, which they called lateral percolation, as the main cause of low water use efficiency in certain irrigated rice fields. Wopereis et al. (1994) also attributed much of the 10-fold difference between seepage plus percolation and percolation in 30 m 15 m plots, to under-bund percolation. The seepage ratio (ratio of seepage plus percolation to percolation alone) increased from 1.02 in unpuddled plots to 1.63 in medium-puddling and 1.90 in high-puddling, thereby showing that relevant under-bund water losses increased with increase in intensity of puddling. It may be because of the fact that in high-puddled plots, decreased hydraulic conductivity of puddled layer (Table 4) resulted in accumulation of more water in the plot to be lost through the process of under-bund percolation. Puddling resulted in a decrease in hydraulic conductivity of the puddled layer. The hydraulic conductivity of the puddled layer decreased by 76% with medium-puddling and 86% with high-puddling compared to that of same layer in puddled plots. The
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Fig. 3. Cross section of an experimental plot showing the movement of under-bund percolating water and location of tensiometers.
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Table 4 Hydraulic properties of puddled layer (0–10 cm) under different situations Situation
Observations
Hydraulic conductivity (cm h1)
Hydraulic a gradient (cm cm1)
Unpuddled plots Medium-puddled plots High-puddled plots Under-bund areas
9 9 9 9
0.064 0.004b 0.015 0.002 0.009 0.002 n.a.d
0.84c 1.26 1.86 0.86c
a
Between puddled and unpuddled soil layers. Mean S:D: c Between 5–10 and 10–15 cm soil layers. d Not applicable. b
hydraulic gradient between the puddled (5–10 cm) and unpuddled layer (10–15 cm) increased with increased intensity of puddling (Table 4). It increased from 0.84 cm cm1 in unpuddled plots to 1.26 cm cm1 in medium-puddled and to 1.86 cm cm1 in highpuddled plots. In unpuddled plots, the movement of water through the surface layer was unrestricted whereas in puddled plots, the movement through the surface puddled layer became restricted thus decreasing the flow of water in the puddled layer and, hence, increasing the hydraulic gradient between puddled and unpuddled layers. In case of under-bund areas, the hydraulic gradient was about the same as that in unpuddled plots, thereby showing the free movement of water under the bunds.
4. Conclusions Percolation losses of water in rice fields were reduced by puddling. However, increasing puddling intensity did not affect these losses to a significant extent. Puddling depth also had no significant effect on the percolation losses of water. The PR was high during the early growth period of the crop but decreased with the passage of time by 35–45% in puddled soils. In unpuddled plots, however, there was no significant decrease in PR with time thus showing that the settling of the finer fraction of sediments in suspension after puddling could decrease percolation losses by creating a semi-permeable layer at the top of the puddled layer. Initially, when the PWD was more, PR was higher but as the infiltration of water took place and PWD got reduced, the PR decreased. Thus, maintenance of shallow PWDs in rice fields can save a substantial amount of water not only by decreasing percolation but also by decreasing the under-bund percolation which is the most important component of water loss from rice fields. The seepage ratio which increased with increased puddling intensity needs to be decreased to decrease water losses. Since high-puddling did not significantly decrease percolation losses any further, the seepage ratio and thus the under-bund percolation can be decreased by avoiding high-puddling intensity. This will not only economise water use in rice fields but also prevent deterioration of soil structure by high-puddling.
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References Adachi, T., 1992. Effect of rice–soil physics: softness of puddled soils and percolation. In: Proceedings of the International Workshop on Soil and Water Engineering for Paddy Field Management. Asian Institute of Technology, Bangkok, 28–30 January 1992, pp. 220–231. Aggarwal, G.C., Sidhu, A.S., Sekhon, N.K., Sandhu, K.S., Sur, H.S., 1995. Puddling and N management effects on crop response in a rice–wheat cropping system. Soil Tillage Res. 36, 129–139. Bouwer, H., Ludke, J., Rice, R.C., 2001. Sealing pond bottoms with muddy water. J Ecol Eng 18, 233–238. Ferguson, J.A., 1970. Effect of flood depth on rice yield and water balance. Arkansas Farmer Res. 19, 4–6. Hardjoamidjojo, S., 1992. The effect of flooding and method of water application on water requirements and yield of wetland paddy. In: Murty, V.V.N., Koga, K. (Eds.), Proceedings of the International Workshop on Soil and Water Engineering for Paddy Field Management. Bangkok, Thailand, 28–30 January 1992, Asian Institute of Technology, Bangkok, pp. 63–71. Humphreys, L., Muirhead, W., Fawcett, B.J., Tounsend, J., 1992. Minimising deep percolation from rice, Farmers Newsletter (Griffith, NSW, Australia) 172, 41–43. IRRI., 1987. Annual report for 1986. International Rice Research Institute. Los Banos, Philippines. Painuli, D.K., Woodhead, T., Pagliai, M., 1988. Effective use of energy and water in rice–soil puddling. Soil Tillage Res. 2, 149–161. Prihar, S.S., Khera, K.L., Gajri, P.R., 1976. Effect of puddling with different implements on the water expense and yield of paddy. J. Res. 13, 249–253 (Punjab Agricultural University, Ludhiana, India). Reddy, Y.M., 1982. Optimisation of Inputs in Rice Production. Sai Venkateswara University, Tirupati, India, p. 98. Sandhu, B.S., Khera, K.L., Prihar, S.S., Singh, B., 1980. Irrigation needs and yield of rice on a sandy loam soil as affected by continuous and intermittent submergence. In. J. Agric. Sci. 50, 492–496. Sandhu, H.S., 1995. Puddlability and Puddling Indices of Alluvial Soils of Punjab. M.Sc. Thesis, Punjab Agricultural University, Ludhiana, India. Sharma, P.K., Bhagat, R.M., 1993. Puddling and compaction effects on water permeability of texturally different soils. J. In. Soc. Soil Sci. 41, 1–6. Sharma, P.K., De Datta, S.K., 1985. Effects of puddling on soil physical properties and processes. Soil Physics and Rice. IRRI, Los Banos, Phillipines, pp. 217–234. Singh, V.P., Wichkam, T.H., 1977. Water movement through wet soils. In: Proceedings of the Symposium on Soils and Rice, Vol. 2. IRRI, Los Banos, Phillipines. Tabbal, D.F., Lampayan, R.M., Bhuiyan, S.I., 1992. Water efficient irrigation technique for rice. Proceedings of International Workshop on Soil and Water Engineering for Paddy Field Management. Asian Institute of Technology, Bangkok, 28–30 January 1992, pp. 146–159. Tuong, T.P., Wopereis, M.C.S., Marquez, J.A., Kropff, M.J., 1994. Mechanisms and control of percolation losses in irrigated puddled rice fields. Soil Sci. Soc. Am. J. 58, 1794–1803. Walker, S.H., Rushton, K.P., 1984. Verification of lateral percolation losses from irrigated rice fields by a numerical model. J. Hydrol. 71, 335–351 (Amsterdam). Wopereis, M.C.S., Bouman, B.A.M., Kropff, M.J., tenBerge, H.F.M., Maligaya, A.R., 1994. Understanding the wateruse efficiency of flodded rice fields. I. Validation of the Soil–water model SAWAH. Agric. Water Manage. 26, 277–289 (Amsterdam). Wopereis, M.C.S., Stein, A., Woodhead, T., 1992a. Sampling number and design for measurement of infiltration in puddled rice fields. Agric. Water Manage. 21, 281–295 (Amsterdam). Wopereis, M.C.S., Wosten, J.H.M., Bouma, J., Woodhead, T., 1992b. Hydraulic resistance in puddled rice soils: measurement and effects on water movement. Soil Tillage Res. 24, 199–209.
Percolation losses of water in relation to puddling intensity and depth in a sandy loam rice (Oryza sativa) field S.S. Kukal*, G.C. Aggarwal Department of Soils, Punjab Agricultural University, Ludhiana, Punjab 141004, India Accepted 19 March 2002
Abstract Percolation loss of water in rice fields is a major factor of low water use efficiency of irrigated rice thus threatening its sustainability. The process of water percolation was studied in a puddled sandy loam rice field with three puddling intensities—no puddling (unpuddled), two passes of tractor-drawn cultivator þ one planking (medium-puddling), and four passes of tractor-drawn cultivator þ one planking (high-puddling), each at shallow (5–6 cm) and normal (10–12 cm) depths. Percolation losses of water decreased with medium-puddling by 54–58%, but it remained unaffected by increased puddling intensity and puddling depth. Percolation rate (PR) decreased with time with both medium- and highpuddling but it increased with increased depth of ponding water. The PR of water recorded in infiltration rings was 1.8, 38.8 and 42.1% less than that recorded in the whole plots thereby indicating the role of under-bund losses. Seepage ratio (ratio of seepage plus percolation to percolation alone) increased with increase in puddling intensity indicating that the magnitude of under-bund percolation was a direct function of puddling intensity. The hydraulic conductivity of the puddled layer decreased with increased puddling intensity (0.064 cm h1 with medium-puddling to 0.009 cm h1 with high-puddling) whereas the hydraulic gradient between puddled and unpuddled layers increased with increase in puddling intensity (0.84 cm cm1 with medium-puddling to 1.86 cm cm1 with high-puddling) # 2002 Elsevier Science B.V. All rights reserved. Keywords: Rice; Percolation rate; Puddling depth; Puddling intensity; Under-bund percolation
1. Introduction Puddling rice (Oryza sativa L.) soils before transplanting reduces percolation losses (Sharma and De Datta, 1985; Humphreys et al., 1992) by eliminating large pores and * Corresponding author. Tel.: þ91-161-401-960; fax: þ91-161-400-945. E-mail address: [email protected] (S.S. Kukal).
0378-3774/02/$ – see front matter # 2002 Elsevier Science B.V. All rights reserved. PII: S 0 3 7 8 - 3 7 7 4 ( 0 2 ) 0 0 0 3 7 - 9
50
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thereby decreasing the hydraulic conductivity of soils. Puddling usually comprises plowing in 7–10 cm deep standing water followed by planking with the help of a wooden/iron leveler. The extent of percolation reduction depends on puddling intensity (Aggarwal et al., 1995), puddling depth (Sharma and Bhagat, 1993), time after puddling, soil type (Singh and Wichkam, 1977), ponding water depth (PWD) (Tabbal et al., 1992) and of course the experimental conditions. The percolation rate (PR) of a sandy loam soil decreased from 14 mm per day with low-puddling (one pass of plowing followed by planking) to 10 mm per day with high-puddling ( four passes of plowing followed by one planking) (Aggarwal et al., 1995). Sharma and Bhagat (1993) reported in a column study that there was a nonlinear reduction in water flux through soils with an increase in puddling depth. The PR decreased linearly with the thickness of the clay layer, whereas Sandhu (1995) in a column study concluded that puddling intensity was more effective than puddling depth in controlling PR in coarse to fine textured soils. However, information on effect of puddling depth on PR under field conditions seems to be lacking. Depth of flooding increased the percolation of somewhat porous, non-swelling soils but reduced the permeability of lowpercolating soils (Singh and Wichkam, 1977). Tabbal et al. (1992) reported a decrease in PR from 20 mm per day under 2–5 cm PWD to 9 mm per day in the continuously saturated regime (PWD ¼ 0 cm) in a clay loam soil whereas Ferguson (1970) reported only a slight increase in percolation loss with increasing water depth. Hardjoamidjojo (1992) reported PR of 2.8, 2.8 and 3.8 mm per day under PWD of 2.5, 5.0 and to 7.5 cm, respectively in a clay textured and fine structured soil. The diversity in research results is due to differences in experimental conditions. Because of high spatial variability of PR, interpretations and extrapolation of results becomes difficult (Wopereis et al., 1992a). Process-oriented research is thus needed to explain the differences in a mechanistic way. Most studies considered the loss through the puddled soil in the field within the surrounding bunds as the only source of percolation loss. Walker and Rushton (1984) reported field results where water balance could not be achieved if it was assumed that only evapotranspiration and vertical percolation through the puddled layer were contributing to water loss. If runoff and seepage losses from one field are a gain to the adjacent field, the only other possible water loss is leakage through areas under inter-plot bunds. This under-bund percolation (IRRI, 1987; Painuli et al., 1988) can be a very important factor adding to percolation losses in puddled rice fields (Tuong et al., 1994). The present study was conducted to observe the process of percolation losses in rice fields in relation to puddling intensity, puddling depth, PWD and under-bund percolation.
2. Materials and methods Field experiments on rice (Oryza sativa) were conducted for 3 years (1994–1996) at Punjab Agricultural University Research Farm, Ludhiana (India), with three puddling intensities i.e. unpuddled, medium (two passes of tractor-drawn cultivator followed by one planking) and high (four passes of tractor-drawn cultivator followed by one planking). Both medium and high-puddling were carried-out at shallow (5–6 cm) and normal (10–12 cm) depths, replicated four times in randomised block design in 22 m 1:8 m plots. The experiment was repeated at the same site and same layout for all the three years.
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Table 1 Physico-chemical characteristics of the study soil Soil properties
Sand (%) Silt (%) Clay (%) pH Bulk density (Mg m3) Electrical conductivity (m mhos) Water content (%, w/w) 0.3 bar Water content (%, w/w) 0.5 bar
Profile depth (cm) 0–15
15–30
30–60
60–90
78 13 9 8.0 1.50 0.28 10.7 6.2
76 14 10 8.1 1.52 0.20 10.2 6.8
68 18 14 7.9 1.54 0.18 14.4 8.6
68 18 14 7.9 1.57 0.18 14.4 8.7
The experimental site is located at 308560 N latitude and 758520 E longitude, is 247 m above mean sea level, and is characterised by a sub-tropical and semi-arid climate with hot and dry summers (March–June) and severe winters (December–January). The area experiences an average rainfall of about 700 mm of which 80% is received during July–September coinciding with the rice season whereas the remaining 20% is received during rabi (November–April) season. Maximum air temperature during three rice seasons ranged between 33:6 1:3 8C (July) and 31:5 1:4 8C (October), and minimum air temperature was between 26:6 0:6 8C (July) and 16:4 1:5 8C (October). Mean per cent relative humidity during rice seasons varied between 76 5:3 (July) and 63 4:1 (October). The soils of the area have developed from alluvium of Pleistocene to recent times under moisture regime. The experimental soil is deep alluvial sandy loam soil (USDA: Typic ustochrept) The physico-chemical characteristics of the experimental soil are given in Table 1. The soil is low in organic carbon (3.3 g kg1), low in KMnO4-extractable N (152 kg N ha1), medium in 0.5 N NaHCO3-extractable P (13.7 kg ha1) and medium in available K (145 kg ha1). The field was cultivated in order to remove the stubbles and the land was flooded with 8–10 cm water. Puddling was done in each plot as per treatments mentioned. Basal doses of zinc sulphate, superphosphate and one-third of total N fertilizer were applied in two equal installments at 3 and 6 weeks after transplanting. All the plots were kept flooded for the first 15 days. Ponded water levels were recorded daily with a hook gauge before applying measured amounts of water, to ensure 5 cm submergence. Afterwards, all the irrigations (each of 7.5 cm amount) were applied 2 days after the drainage of ponded water (Sandhu et al., 1980). Depth of water applied was also recorded with a hook gauge from a levelled and fixed platform in each plot. PR were monitored from data on water levels and evaporation from open pan located in the irrigated area surrounded by rice paddies. PR for various rice cropping seasons (1994–96) were estimated by the sum of total irrigation water applied (I) and cropping season rainfall (P) minus the cumulative pan evaporation (PE) divided by the duration of crop growing season (d). A metal ring with a diameter of 40 cm and a height of 35 cm was pushed into the soil at four points to a depth of approximately 15 cm in the centre of each plot to study the process of percolation losses in the absence of under-bund movement of water. The rate of infiltration into each column was monitored
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throughout a 24 h period. The water level inside the ring was maintained with that outside in the whole plot. The tensiometers were installed at 5–10 and 10–15 cm soil depths both in the centre of the experimental plots (under normal depth of puddling) and in the inter-plot bunds (at the same depths as in plots) to monitor soil water potential status. These were fabricated indigenously using ceramic cup at the bottom of a PVC pipe fitted with a mercury manometer. The whole system was made air-tight so as to maintain the continuity of water column in the system. The height of rise of mercury column (ZHg) was measured and related to soil matric potential (cm) as: cm ¼ 12:6 Z Hg þ Z0 , whereas Z0 is distance between center of ceramic cup to the surface of mercury in the reservoir. Using Darcy’s Law, the hydraulic conductivity of the puddled layer was calculated corresponding to PWD of 7 cm. Also, the hydraulic head gradient between puddled (5–10 cm) and unpuddled (10–15 cm) soil layers was determined. The hydraulic conductivity of puddled layers and the hydraulic gradient between puddled and unpuddled layers were determined for unpuddled, medium-puddling, high-puddling and under-bund conditions.
3. Results and discusion 3.1. Percolation rate The mean PR decreased with puddling during all 3 years of the study (Table 2). It decreased by 55, 54 and 58% in 1994, 1995 and 1996, respectively with medium-puddling from that in unpuddled plots. However, high-puddling intensity did not significantly decrease PR any further, compared to medium-puddling despite of the fact that sediment density of soil–water suspension immediately after puddling was more (0.271 Mg m3) with high-puddling than that with medium-puddling (0.169 Mg m3). This shows that finer particles at the top of the graded layers brought in suspension by medium-puddling were sufficient to decrease the permeability of the surface soil and thus decreasing the PR. Further increase in sediment density of the suspension did not affect the PR. Bouwer et al. Table 2 Effect of puddling intensity and depth on average PR during 1994–96 Treatments
PR (cm per day) 1994
1995
1996
Mean
Puddling intensity Unpuddled Medium-puddled High-puddled LSD (0.05)
2.96 1.32 1.30 0.38
2.98 1.36 1.25 0.38
3.10 1.31 1.16 0.20
3.01 1.32 1.19
Puddling depth Shallow Normal LSD (0.05)
1.21 1.34 NS
1.28 1.22 NS
1.28 1.22 NS
1.26 1.26
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(2001) observed in a column study that the graded sediment layer with coarsest particles on the bottom and the finest particles on top gives more seepage control than even a uniform compact layer. Although, well-controlled studies in microplots (Wopereis et al., 1992b) and in laboratories (Adachi, 1992) showed that puddling reduced PR by 500–1000 times, most field studies report a reduction of less than five times (Humphreys et al., 1992 ; Aggarwal et al., 1995). No significant differences were observed between PR of shallow and normal puddled plots. Thus, puddling done both at shallow and normal depths was equally effective in checking percolation losses. This confirms the observation of Sandhu (1995) in a column study that puddling intensity was more effective than puddling depth in checking percolation losses in coarse to fine textured soils. 3.2. Temporal changes in percolation rate In unpuddled soils, the PR remained more or less unchanged with time but in puddled soils, it decreased with time (Fig. 1). The PR with medium-puddling was about 2.15 cm per day at 2 days after transplanting (DAT) and it decreased by 35% at 50 DAT in 1995 (Fig. 1a). With high-puddling, the PR decreased from 1.70 cm per day at 2 DAT to 1.0 cm per day at 50 DAT. During 1996, the corresponding values were 2.1 and 1.35 cm per day with medium-puddling (Fig. 1b) and 1.7 and 0.95 cm per day for the same days with highpuddling. Painuli et al. (1988) observed that the PR was high initially and decreased with the passage of time. This is attributed to the clogging of the pores in the top layer by the settling of fine particles in suspension, by algal growth and root effects (Prihar et al., 1976; Reddy, 1982). Almost no decrease in PR in unpuddled fields can be due to negligible suspension and hence settling of finer soil particles at the surface. It shows that settling and subsequent sealing by finer particles of suspension are mainly responsible for the decrease in PR with time. 3.3. Ponding water depth and percolation The change in PR during an irrigation cycle is depicted in Fig. 2. Immediately after applying irrigation water to a depth of 10 cm in 1995, the PR was 3.70 cm per day after the first day of ponding in unpuddled soil (Fig. 2a) and decreased to nearly 2.0 cm per day on the fourth day of ponding when the PWD was 2.1 cm. In the case of medium-puddling, the PR decreased from 1.6 cm per day after the first day of ponding (PWD ¼ 10 cm) to 1.0 cm per day on the fourth day when the PWD was 5.6 cm. With high-puddling, the PR decreased from 1.3 cm per day (PWD ¼ 10 cm) to 0.9 cm per day (PWD ¼ 6:2 cm) for the same days. A similar trend was observed during 1996 (Fig. 2b). Initially, when the PWD was 10 cm, the PR was high in all the puddling treatments. However, as the PWD decreased due to infiltration of water, PR also decreased. This indicates that a substantial amount of water can be saved if shallow PWDs are maintained in sandy loam rice fields. Tuong et al. (1994) observed that a 10-fold increase in PWD (from 1 to 10) changed the PR from 2.75 to 3.25 cm per day. Shallow PWD reduces the wetted area of inter-plot bunds and limits the amount of water infiltrating laterally into the bunds. Furthermore, if the PWD is kept very low or if the field is maintained at saturation point, the water loss is greatly reduced because
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Fig. 1. Effect of puddling intensity on seasonal changes in percolation rate in (a) 1995 and (b) 1996.
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Fig. 2. Effect of puddling intensity on percolation rate immediately after irrigation during (a) 1995 and (b) 1996.
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Table 3 Effect of puddling intensity on PR from whole plots and infiltration rings for all puddling intensities Puddling intensity
Unpuddled Medium-puddled High-puddled
PR (cm per day) Whole plot
Infiltrometer rings
Decrease (%)
Seepage ratio
2.81 1.47 1.33
2.76 0.90
1.8 38.8 0.70
1.02 1.63
the unevenness of the soil surface prevents water movement to the bunds and subsequent loss through under-bunds (Tabbal et al., 1992). 3.4. Under-bund percolation The PR recorded in the whole plot was more than that recorded in infiltration rings for all puddling intensities (Table 3). The PR recorded in infiltration rings were 1.8, 38.8 and 42.1% less than those recorded in whole plots for unpuddled, medium- and high-puddling treatments, respectively. This difference in PR recorded in rings and whole plots could be due to lateral movement of water from whole plots through inter-plot bunds which remained unpuddled (Fig. 3). This type of movement (seepage), however, was not possible from infiltration rings. Thus, the water loss from the whole plots consisted of two components, i.e. percolation (vertical) and seepage (lateral), whereas the water loss recorded in the infiltrometer rings was due to percolation only. This seepage water was lost as under-bund percolation despite of the fact that the surface of the bunds was plastered with puddled soil, which is a common practice with the farmers of the region. In fact, the puddled soil used for plastering is taken from inside the field (Fig. 3) in close proximity of the bunds. This exposes the unpuddled spots along the bunds inside the field and hence the water starts seeping laterally through these spots as shown in Fig. 3. Tuong et al. (1994) observed that a small area of non-puddled soil increased field percolation losses by a factor 5 and under-bund percolation caused a further 2–5-fold increase depending on the size of the field. This under-bund percolation is thus an important factor that determines percolation loss in puddled rice fields (IRRI, 1987; Painuli et al., 1988). Walker and Rushton (1984) identified under-bund percolation, which they called lateral percolation, as the main cause of low water use efficiency in certain irrigated rice fields. Wopereis et al. (1994) also attributed much of the 10-fold difference between seepage plus percolation and percolation in 30 m 15 m plots, to under-bund percolation. The seepage ratio (ratio of seepage plus percolation to percolation alone) increased from 1.02 in unpuddled plots to 1.63 in medium-puddling and 1.90 in high-puddling, thereby showing that relevant under-bund water losses increased with increase in intensity of puddling. It may be because of the fact that in high-puddled plots, decreased hydraulic conductivity of puddled layer (Table 4) resulted in accumulation of more water in the plot to be lost through the process of under-bund percolation. Puddling resulted in a decrease in hydraulic conductivity of the puddled layer. The hydraulic conductivity of the puddled layer decreased by 76% with medium-puddling and 86% with high-puddling compared to that of same layer in puddled plots. The
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Fig. 3. Cross section of an experimental plot showing the movement of under-bund percolating water and location of tensiometers.
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Table 4 Hydraulic properties of puddled layer (0–10 cm) under different situations Situation
Observations
Hydraulic conductivity (cm h1)
Hydraulic a gradient (cm cm1)
Unpuddled plots Medium-puddled plots High-puddled plots Under-bund areas
9 9 9 9
0.064 0.004b 0.015 0.002 0.009 0.002 n.a.d
0.84c 1.26 1.86 0.86c
a
Between puddled and unpuddled soil layers. Mean S:D: c Between 5–10 and 10–15 cm soil layers. d Not applicable. b
hydraulic gradient between the puddled (5–10 cm) and unpuddled layer (10–15 cm) increased with increased intensity of puddling (Table 4). It increased from 0.84 cm cm1 in unpuddled plots to 1.26 cm cm1 in medium-puddled and to 1.86 cm cm1 in highpuddled plots. In unpuddled plots, the movement of water through the surface layer was unrestricted whereas in puddled plots, the movement through the surface puddled layer became restricted thus decreasing the flow of water in the puddled layer and, hence, increasing the hydraulic gradient between puddled and unpuddled layers. In case of under-bund areas, the hydraulic gradient was about the same as that in unpuddled plots, thereby showing the free movement of water under the bunds.
4. Conclusions Percolation losses of water in rice fields were reduced by puddling. However, increasing puddling intensity did not affect these losses to a significant extent. Puddling depth also had no significant effect on the percolation losses of water. The PR was high during the early growth period of the crop but decreased with the passage of time by 35–45% in puddled soils. In unpuddled plots, however, there was no significant decrease in PR with time thus showing that the settling of the finer fraction of sediments in suspension after puddling could decrease percolation losses by creating a semi-permeable layer at the top of the puddled layer. Initially, when the PWD was more, PR was higher but as the infiltration of water took place and PWD got reduced, the PR decreased. Thus, maintenance of shallow PWDs in rice fields can save a substantial amount of water not only by decreasing percolation but also by decreasing the under-bund percolation which is the most important component of water loss from rice fields. The seepage ratio which increased with increased puddling intensity needs to be decreased to decrease water losses. Since high-puddling did not significantly decrease percolation losses any further, the seepage ratio and thus the under-bund percolation can be decreased by avoiding high-puddling intensity. This will not only economise water use in rice fields but also prevent deterioration of soil structure by high-puddling.
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References Adachi, T., 1992. Effect of rice–soil physics: softness of puddled soils and percolation. In: Proceedings of the International Workshop on Soil and Water Engineering for Paddy Field Management. Asian Institute of Technology, Bangkok, 28–30 January 1992, pp. 220–231. Aggarwal, G.C., Sidhu, A.S., Sekhon, N.K., Sandhu, K.S., Sur, H.S., 1995. Puddling and N management effects on crop response in a rice–wheat cropping system. Soil Tillage Res. 36, 129–139. Bouwer, H., Ludke, J., Rice, R.C., 2001. Sealing pond bottoms with muddy water. J Ecol Eng 18, 233–238. Ferguson, J.A., 1970. Effect of flood depth on rice yield and water balance. Arkansas Farmer Res. 19, 4–6. Hardjoamidjojo, S., 1992. The effect of flooding and method of water application on water requirements and yield of wetland paddy. In: Murty, V.V.N., Koga, K. (Eds.), Proceedings of the International Workshop on Soil and Water Engineering for Paddy Field Management. Bangkok, Thailand, 28–30 January 1992, Asian Institute of Technology, Bangkok, pp. 63–71. Humphreys, L., Muirhead, W., Fawcett, B.J., Tounsend, J., 1992. Minimising deep percolation from rice, Farmers Newsletter (Griffith, NSW, Australia) 172, 41–43. IRRI., 1987. Annual report for 1986. International Rice Research Institute. Los Banos, Philippines. Painuli, D.K., Woodhead, T., Pagliai, M., 1988. Effective use of energy and water in rice–soil puddling. Soil Tillage Res. 2, 149–161. Prihar, S.S., Khera, K.L., Gajri, P.R., 1976. Effect of puddling with different implements on the water expense and yield of paddy. J. Res. 13, 249–253 (Punjab Agricultural University, Ludhiana, India). Reddy, Y.M., 1982. Optimisation of Inputs in Rice Production. Sai Venkateswara University, Tirupati, India, p. 98. Sandhu, B.S., Khera, K.L., Prihar, S.S., Singh, B., 1980. Irrigation needs and yield of rice on a sandy loam soil as affected by continuous and intermittent submergence. In. J. Agric. Sci. 50, 492–496. Sandhu, H.S., 1995. Puddlability and Puddling Indices of Alluvial Soils of Punjab. M.Sc. Thesis, Punjab Agricultural University, Ludhiana, India. Sharma, P.K., Bhagat, R.M., 1993. Puddling and compaction effects on water permeability of texturally different soils. J. In. Soc. Soil Sci. 41, 1–6. Sharma, P.K., De Datta, S.K., 1985. Effects of puddling on soil physical properties and processes. Soil Physics and Rice. IRRI, Los Banos, Phillipines, pp. 217–234. Singh, V.P., Wichkam, T.H., 1977. Water movement through wet soils. In: Proceedings of the Symposium on Soils and Rice, Vol. 2. IRRI, Los Banos, Phillipines. Tabbal, D.F., Lampayan, R.M., Bhuiyan, S.I., 1992. Water efficient irrigation technique for rice. Proceedings of International Workshop on Soil and Water Engineering for Paddy Field Management. Asian Institute of Technology, Bangkok, 28–30 January 1992, pp. 146–159. Tuong, T.P., Wopereis, M.C.S., Marquez, J.A., Kropff, M.J., 1994. Mechanisms and control of percolation losses in irrigated puddled rice fields. Soil Sci. Soc. Am. J. 58, 1794–1803. Walker, S.H., Rushton, K.P., 1984. Verification of lateral percolation losses from irrigated rice fields by a numerical model. J. Hydrol. 71, 335–351 (Amsterdam). Wopereis, M.C.S., Bouman, B.A.M., Kropff, M.J., tenBerge, H.F.M., Maligaya, A.R., 1994. Understanding the wateruse efficiency of flodded rice fields. I. Validation of the Soil–water model SAWAH. Agric. Water Manage. 26, 277–289 (Amsterdam). Wopereis, M.C.S., Stein, A., Woodhead, T., 1992a. Sampling number and design for measurement of infiltration in puddled rice fields. Agric. Water Manage. 21, 281–295 (Amsterdam). Wopereis, M.C.S., Wosten, J.H.M., Bouma, J., Woodhead, T., 1992b. Hydraulic resistance in puddled rice soils: measurement and effects on water movement. Soil Tillage Res. 24, 199–209.