Evaluation of non-puddling under shallow water tables and
alternative tillage methods on soil and crop parameters
in a rice±wheat system in Uttar Pradesh
R.K. Bajpai
a,*, R.P. Tripathi
a,baDepartment of Soil Science and Agricultural Chemistry, Indira Gandhi Agricultural University, Raipur 492012, India bDepartment of Soil Science, G.B. Pant University of Agriculture and Technology, Pantnagar 263145, Uttar Pradesh, India
Received 8 July 1997; received in revised form 15 April 1998; accepted 16 March 2000
Abstract
The existence of a shallow water table (surface to 0.54 m from June to October) is common phenomenon in Tarai (foothills of the Himalaya) of Uttar Pradesh, India. Puddled rice (Oryza sativaL.) crop followed by conventional land preparation for the succeeding wheat (Triticum aestivumL.) crop is normal cultivation practice in the region. This shallow water table can be effectively utilised to avoid puddling operations for the seeding of rice and reduce the degree of tillage required for the following wheat crop. An investigation was made in silty clay loam (Chernozem), for two consecutive years (1992±1993 and 1993±1994) at Pantnagar, India, in a rice±wheat cropping system. The treatments for rice were puddling and non-puddling with two fertility levels (NPK: 120:40:40 and 180:60:60) and for wheat two tillage systems (conventional and zero tillage) in puddled and non-puddled rice ®eld with two fertility levels. Puddling signi®cantly reduced the bulk density of the surface (0± 0.06 m) soil at the tillering stage of rice, compared to non-puddling, whereas it was signi®cantly higher after harvest. The hydraulic conductivity of the 0±0.06 m soil depth also reduced to one-sixth and one-half due to puddling at tillering and harvesting stages, respectively. In®ltration rate was decreased from 0.68 to 0.46 mm hÿ1at tillering and 1.78 to 0.94 mm hÿ1 at harvest due to puddling. The puddling only in rice enhanced the root length density by 12% but affected adversely the wheat crop and minimised the root length density by 28%. Both puddling and non-puddling were found to be equally effective for grain yield of rice. However, non-puddling of rice produced signi®cantly higher wheat grain yield than that of wheat followed by puddled rice. Conventional tillage of wheat produced signi®cantly higher (25%) grain yield than that of zero tillage. This study indicated that in shallow water table conditions, direct drilling of rice in place of puddled rice and conventional tillage for wheat is an alternative cultivation practice in a rice±wheat system.#2000 Published by Elsevier Science B.V. All rights reserved.
Keywords:Bulk density; Hydraulic conductivity; In®ltration rate; Root growth; Rice±wheat system
1. Introduction
In India, rice and wheat occupy an area of 42 and 23 million hectares, respectively, and require different *Corresponding author. Tel.:91-771-422-149;
fax:91-771-424-532.
E-mail address: pankaj.oudhia@usa.net (R.K. Bajpai)
soil physical environments. Puddling is a common ®eld preparation practice to maintain wetland condi-tions for rice. Puddling is not only time consuming and capital intensive, but also alters the soil physical condition so that it is not conducive for the succeeding wheat. Rice grown after minimum tillage can produce yields similar to that under conventional puddling with minimised expenses on ®eld preparation (Sharma et al., 1988). Puddling for rice often causes subsurface compaction which may adversely affect the yield of the succeeding crop due to reduction in root growth and its distribution under poor soil physical environ-ment (Oussible et al., 1992). Reduced root growth limits water uptake and consequently plants may experience water stress. Amelioration of the soil compaction requires additional tillage and energy for succeeding crops. Minimum tillage was shown to have an advantage over puddling in a clay loam soil for maintaining physical condition and saving ®eld preparation time (Brown and Quantrill, 1973). Excessive wetness in puddled rice soil can delay the planting of the following wheat and result in yield reductions of 35±40 kg haÿ1 per day by a delay in planting after November 20 (Randhawa et al., 1981; Hobbs, 1987).
Traditional land preparation in India for wheat after rice consists of 5±7 cultivator operations followed by levelling with heavy wooden plank. Land is usually left for few days to dry after ploughing and then irrigated to allow rapid decom-position of residues to obtain a good tilth. In heavy soils, Majid et al. (1987) compared the traditional method of sowing of wheat with direct drilling in between the rice stubbles and found no signi®cant difference in grain yield and biomass pro-duction.
The water table in foothill soils may rise almost to the ground surface (to less than 0.3 m depth) in the rainy season and hence rice plants may directly utilise the water (Choudhary, 1979). This provided the basis for investigating possibilities of avoiding puddling operation by direct seeding of rice, which in turn would ease the sowing of the succeeding wheat crop. Objectives of the present investigation were to study the effect of different tillage practices on physical properties of soil, rooting pattern and grain yield of rice and wheat in rice±wheat system.
2. Materials and methods
2.1. Field experiments
The ®eld experiments were conducted at G.B. Pant University of Agriculture and Technology, Pantnagar, India, for 2 years (1992±1993 and 1993±1994). The mean annual rainfall of the area is 1364 mm. The total rainfall during the rice growing season from June to October was 772 mm in 1992 and 1327 mm in 1993. During the wheat growing season, the rainfall from November to April was 80 mm in 1992±1993 and 71 mm in 1993±1994. The soil is a silty clay loam mixed hyperthermic Aquic Hapludoll (Haplic Cher-nozem). The soil contained 150 g kgÿ1 sand, 530 g kgÿ1silt and 320 g kgÿ1clay, with a high con-centration of organic carbon (28 g kgÿ1) (Walkley and Black, 1934), a medium concentration of KMnO4 ex-tractable nitrogen (250 kg haÿ1), 0.5 M sodium bicar-bonate (NaHCO3) extractable phosphorus (15.3 kg haÿ1), and available potassium (225 kg haÿ1).
drilled plots, and at the time of transplanting in puddled plots. Nitrogen was applied in three equal splits (40 and 60 kg haÿ1) at transplanting, and at 3 and 6 weeks after transplanting. Nitrogen in non-puddled plots was applied at the time of ®eld pre-paration and at tillering and panicle initiation stages of crop growth. Anilofos was sprayed two days after sowing at the rate of 1.5 kg active ingredient haÿ1in non-puddled plots to control weeds.
Wheat (cv.``HD 2329'') was sown during 29 November to 2 December in the 2 years. Full rate of P and K was applied at the time of sowing and N was applied in two equal splits one at sowing and the other at 4 weeks later. Wheat was irrigated (three irrigations each of 60 mm were required) according to irrigation schedule recommended for wheat crop in theTarairegion.
2.2. Groundwater and soil measurements
To determine the ¯uctuation in groundwater table under natural conditions, piezometers were installed at six representative sites in the ®eld by drilling holes equal to the internal diameter of pipes with the bucket auger specially designed for this purpose. The pipes were driven 1.5 m into the soil with the help of heavy wooden blocks and hammer leaving 0.15 m above the soil surface. The measurements were made on alter-nate days.
Soil bulk density and saturated hydraulic conduc-tivity were each determined as described by Smith and Mullins (1991) on intact soil cores (three soil cores per plot). In the rice treatments, observations were taken at tillering stage and 2 days after harvest. For wheat, bulk density was determined at crown root initiation stage and at harvest. These observations were taken in both years. For saturated hydraulic conductivity and bulk density, aluminium cores (78 mm diameter, 58 mm high) were driven to a depth of 0±0.06 and 0.12± 0.18 m (compact horizon as per pro®le study). A constant water head was maintained on top of each core in the laboratory and the rate of water ¯ow through the soil was measured at steady state. Darcy's law was utilised to calculate the saturated hydraulic conductivity. The soil cores were then oven-dried to calculate bulk density. In®ltration was measured in situ with a double-ring (three rings per treatment) in®ltrometer (Mishra and Ahmad, 1990). The inside
ring, from which measurements were taken, was 300 mm in diameter and the outer guard ring was 500 mm. In®ltration rate was measured at tillering stage and at harvest of rice crop.
2.3. Root measurements
Rice root samples (three samples per plot) were taken at penicle initiation and at ripening stage. Wheat root samples were taken at 105 days after sowing, with a core sampler of 100 mm diameter and 150 mm height, from 0 to 0.10, 0.10 to 0.20, 0.20 to 0.30, 0.30 to 0.40, and 0.40 to 0.50 m depths in sequence. The soil from each depth was washed over a 0.1 mm screen and the separated roots were stored in bottles containing 5% formalin solution. Root length was measured by the Newman (1966) method modi®ed by Tennant (1975) using 0.01 m0.01 m size grid as follows:
Root length R 0:786number of intersections
grid unit (1)
The root length density of rice and of wheat were each calculated from the total root length and the sample volume.
2.4. Crop yield
The net sub±sub-plot area (5 m4.6 m) was har-vested after removing the border rows and threshed. The grain yield was recorded after cleaning and drying at 140 g kgÿ1moisture and expressed in kg haÿ1.
2.5. Statistical methods
Analysis of variance (ANOVA) was performed to study the effect of puddling, tillage, and fertility levels on soil physical properties, root growth and grain parameters. The ANOVA was done in split and split± split plot design as described by Cohran and Cox (1957).
3. Results and discussion
3.1. Groundwater
3.2. Soil bulk density
Puddling performed for planting of rice signi®-cantly reduced bulk density of surface soil (0± 0.06 m) only at tillering stage (Table 1). At harvest, bulk density of puddled plots increased and was found to be signi®cantly higher than that of the non-puddled plot at both depths (0±0.06 and 0.12±0.18 m) during second year. The two fertility levels had no effect on bulk density at either depth or growth stage. The puddling and non-puddling operation in¯uenced sig-ni®cantly the bulk density at soil depth (interaction of puddling and soil depth). The puddling operation produced the highest bulk density in 0.12±0.18 m soil depth at both the stages, whereas the lowest bulk density was observed at 0±0.06 m soil depth under puddled plots at tillering and in non-puddled plot at harvest of the rice. Ghildyal (1982) and Rahman (1991) have also reported an increase in soil density below the puddled layer due to physical compaction during the puddling process. The interaction effect of puddling and non-puddling with different years indi-cated that puddling and non-puddling operations per-formed during both the years differed in response at the tillering stage of rice. The bulk density was
max-imum (1.55 mg mÿ3) under non-puddled condition during 1992, whereas it decreased (1.51 mg mÿ3) signi®cantly during the subsequent year. Bulk density remained unchanged due to puddling over these years. The puddling performed on rice also in¯uenced bulk density at the 0±0.06 m soil surface layer during the wheat growing period (Table 2). After harvest of wheat, bulk density was signi®cantly higher under puddled plot than non-puddled plots. The increase in bulk density may have been due to settling of soil particles. Similar observations were recorded by Sur et al. (1981) and Sawhney and Sehgal (1989). The tillage operation performed in wheat signi®cantly reduced soil bulk density. Conventional tillage bulk density was signi®cantly lower than zero tillage.
3.3. Hydraulic conductivity and in®ltration rate
The hydraulic conductivity of non-puddled plots in both soil depths (0.0±0.06 and 0.12±0.18 m) was sig-ni®cantly higher than that of puddled plot at both the tillering and at harvest stage of rice (Table 3). The decrease in hydraulic conductivity by puddling was probably due to destruction of soil aggregates and reduction of non-capillary pores (Sharma and De
Table 1
Effect of puddling and fertility levels on soil bulk density (mg mÿ3) at two soil depths during rice crop period
Treatment Soil depth (0±0.06 m) Soil depth (0.12±0.18 m)
1992 1993 Mean 1992 1993 Mean
Tillering stage
Puddling
Puddling 1.30 1.33 1.31 1.64 1.61 1.62
Non-puddling 1.42 1.41 1.42 1.61 1.58 1.59
LSD(0.05) 0.02 0.05 0.02 NS NS NS
Fertiliser
F1 1.35 1.38 1.36 1.62 1.59 1.60
F2 1.36 1.37 1.36 1.63 1.60 1.61
LSD(0.05) NS NS NS NS NS NS
After harvest
Puddling
Puddling 1.48 1.50 1.49 1.68 1.70 1.69
Non-puddling 1.45 1.44 1.44 1.66 1.64 1.65
LSD(0.05) NS 0.03 0.03 NS 0.05 0.03
Fertiliser
F1 1.46 1.45 1.46 1.66 1.65 1.65
F2 1.47 1.49 1.48 1.68 1.68 1.68
Dutta, 1985; Mambani et al., 1989). Two fertility levels had no effect on hydraulic conductivity.
The interaction of puddling and non-puddling operations with depths revealed that non-puddled plots recorded the highest hydraulic conductivity in the 0±0.06 m soil depth at tillering (3.3 mm hÿ1) as well as at harvest (2.11 mm hÿ1) stage of rice. The lowest hydraulic conductivity (0.45 mm hÿ1) was noted in the 0.12±0.18 m soil depth at tillering stage under the puddled plot. The in®ltration rate of the non-puddled plot was signi®cantly higher than that of the puddled plot (Table 4). The interaction effect of treatments with the years was signi®cant for in®ltra-tion rate at tillering as well as harvest stage.
3.4. Root growth
Root length density (RLD) of rice in the puddled treatment was signi®cantly higher than in the non-puddled treatment. The major portion of roots was concentrated in 0±0.10 m soil depth and hence recorded signi®cantly higher RLD than lower depth (Table 5). Ghildyal and Satyanarayana (1969) also reported that rice roots were mainly restricted to 0± 0.07 m layer in a sandy clay loam. Similarly, RLD was signi®cantly higher in 1.5 recommended fertiliser rate than in the recommended rate.
The third order interaction of puddling and non-puddling operations with fertility levels and depth of
Table 2
Effect of puddling, fertility levels and tillage on bulk density (mg mÿ3) of soil in 0±0.06 m depth during wheat crop period
Treatment CRIastage After harvest
1992±1993 1993±1994 Mean 1992±1993 1993±1994 Mean Puddling
Puddling 1.44 1.45 1.45 1.49 1.49 1.49
Non-puddling 1.42 1.39 1.41 1.45 1.44 1.45
LSD(0.05) NS 0.04 0.02 0.03 0.02 0.02
Fertiliser
F1 1.43 1.41 1.42 1.46 1.47 1.47
F2 1.43 1.43 1.43 1.48 1.47 1.47
LSD(0.05) NS NS NS NS NS NS
Tillage
Conventional 1.40 1.38 1.39 1.46 1.44 1.45
Zero 1.47 1.46 1.47 1.49 1.50 1.50
LSD(0.05) 0.02 0.02 0.02 0.02 0.04 0.02
aCrown root initiation stage.
Table 3
Effect of puddling on hydraulic conductivity (mm hÿ1) of soil at two soil depths during rice crop period
Treatment Soil depth (0±0.06 m) Soil depth (0.12±0.18 m)
1992 1993 Mean 1992 1993 Mean
Tillering stage
Puddling
Puddling 0.61 4.57 0.59 0.46 0.43 0.45
Non-puddling 3.35 3.24 3.30 1.24 1.40 1.32
LSD(0.05) 0.13 0.04 0.08 0.04 0.05 0.08
After harvest
Puddling
Puddling 1.04 1.03 1.04 0.97 1.16 1.06
Non-puddling 2.13 2.17 2.15 1.78 1.84 1.81
soil was signi®cant for RLD at panicle initiation and ripening stage of rice (Table 6). The RLD was higher in puddled plot than that of the non-puddled plot. The maximum RLD was obtained at 0±0.10 m depth fer-tilised with 1.5 recommended rate of fertiliser. In comparison, minimum RLD was observed at 0.40± 0.50 m soil depth fertilised with recommended rate of fertiliser in puddled plots. Almost similar interaction was observed at ripening stage. Higher root growth in the surface layer might have been due to lower bulk density in the puddled plot.
The wheat grown on non-puddled rice plot signi®-cantly increased the RLD (3.03 mm mmÿ3) at ripen-ing stage in 1993±1994 in 0±0.50 m soil depth (Table 7). The lower bulk density of non-puddled rice plot promoted the root growth of wheat. The conven-tional tillage produced a signi®cantly higher RLD
(3.11 mm mmÿ3) than did zero tillage (2.30 mm mmÿ3) treatment.
The interaction between tillage and depths was signi®cant (Table 7). RLD of 0±0.50 m soil depth under conventional tillage maintained its superiority over zero tillage, but at 0.40±0.50 m depth the differ-ences in RLD under these tillage operations were similar.
3.5. Grain yield
The grain yields of rice from puddled or non-puddled treatments were statistically similar indicat-ing successful cultivation of rice even under non-puddled condition (Table 8). The variation of soil bulk density, hydraulic conductivity and in®ltration rate due to non-puddling and puddling operation did not
Table 4
Effect of puddling on in®ltration rate (mm hÿ1) of soil during rice crop period
Treatment Tillering stage After harvest
1992 1993 Mean 1992 1993 Mean
Puddling
Puddling 0.47 0.45 0.46 0.96 0.92 0.94
Non-puddling 0.64 0.75 0.69 1.75 1.81 1.78
LSD(0.05) 0.05 0.07 0.06 0.06 0.03 0.06
Table 5
Effect of puddling and fertility levels on RLD (mm mmÿ3) of rice at two growth stages
Treatment Panicle initiation stage Ripening stage
1992 1993 Mean 1992 1993 Mean
Puddling
Puddling 4.22 4.98 4.60 6.32 6.81 6.57
Non-puddling 4.03 4.23 4.13 5.60 5.97 5.79
LSD(0.05) 0.48 0.75 0.25 0.710 0.80 0.34
Fertiliser
F1 3.70 4.28 4.00 5.42 6.01 5.71
F2 4.46 4.93 4.70 6.48 6.78 6.64
LSD(0.05) 0.22 0.60 0.26 0.46 0.23 0.18
Depth (m)
0±0.10 14.42 14.81 14.61 21.67 23.00 22.34
0.10±0.20 2.20 2.74 2.47 3.47 3.56 3.52
0.20±0.30 1.95 2.50 2.23 2.20 2.54 2.37
0.30±0.40 1.30 1.70 1.50 1.48 1.74 1.61
0.40±0.50 0.77 1.12 0.95 0.97 1.13 1.05
affect the grain yield of rice. The RLD of rice due to puddling was mainly concentrated in surface layer but under non-puddled treatment its concentration was more lower in the pro®le (Table 6). This shows a potential possibility of raising direct seeded rice in non-puddled ®elds at these conditions.
Grain yield of wheat was signi®cantly lower in puddled rice plot than in non-puddled rice plots in both the years (Table 9). This may be due to subsur-face compaction. Similar results have also been reported in a clay loam soil by Oussible et al.
(1992). Conventional tillage for wheat produced sig-ni®cantly higher grain yield than did zero tillage. The higher fertility level produced signi®cantly higher grain yield than did lower fertility levels. The puddling and tillage interaction was found to be signi®cant. The zero tillage for wheat in non-puddled rice produced 23% higher grain yield than did the zero tillage in puddled rice. Conventional tillage in non-puddled rice produced 9% higher grain yield than conventional tillage in the puddled rice.
4. Conclusions
The tillage practices carried out for planting/seed-ing in a rice±wheat system under a shallow ground water condition revealed that rice grown under
non-Table 6
Interaction effect of puddling (P), fertiliser (F) and soil depth (D) on RLD (mm mmÿ3) of rice at two growth stages
Soil depth (m) Panicle initiation stage
Ripening stage F1 F2 F1 F2
Puddling
0.0±0.10 14.45 18.10 22.93 25.83 0.10±0.20 2.36 2.66 3.53 3.88 0.20±0.30 1.90 2.10 2.05 2.15 0.30±0.40 1.14 1.40 1.21 1.47 0.40±0.50 0.74 0.89 0.72 1.07 Non-puddling
0.0±0.10 12.13 13.77 18.13 22.45 0.10±0.20 2.40 2.47 3.25 3.41 0.20±0.30 2.34 2.58 2.48 2.80 0.30±0.40 1.59 1.83 1.78 1.98 0.40±0.50 0.94 1.21 1.07 1.34 LSD(0.05)
2 fertiliser at PD 0.49 0.67 2 depth at PF 0.36 0.70
Table 7
RLD (mm mmÿ3) of wheat in different soil depths (D) at ripening
stage as in¯uenced by tillage (T) practices of wheat Soil depth (m) Tillage
Effect of puddling and fertility levels on grain yield (kg haÿ1) of
rice over 2 years
LSD(0.05) 280 300 341
Table 9
Effect of puddling, fertility levels and tillage on grain yield (kg haÿ1) of wheat over 2 years
Treatment 1992±1993 1993±1994 Mean Puddling
Puddling 3075 4046 3560 Non-puddling 3558 4600 4079
LSD(0.05) 320 460 200
Fertiliser
puddled conditions produced similar grain yield to that of rice grown under puddled conditions. Puddling increased bulk density of surface and subsurface soil at harvest and caused a decrease in in®ltration rate and hydraulic conductivity in subsequent years. Increased soil bulk density adversely affected root growth and grain yield of the following wheat crop. The conven-tional tillage was superior than zero tillage for grain yield of wheat. More interestingly, the conventional tillage utilised for wheat after non-puddled rice gave a higher yield than that under puddled rice.
Acknowledgements
The ®rst author is grateful to the Council of Scien-ti®c and Industrial Research, New Delhi, India, for awarding a senior research fellowship and admissible ®nancial support to carry out this study.
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