Effect of pre-planting tillage on crop yields and weed biomass in a
rice±wheat system on a sandy loam soil in Punjab
P.R. Gajri
*, K.S. Gill, Rachhpal Singh, B.S. Gill
Department of Soils, Punjab Agricultural University, Ludhiana 141004, Punjab, India
Received 29 December 1997; received in revised form 6 August 1998; accepted 9 June 1999
Abstract
In rice (Oryza sativaL.) culture the effect of puddling (wet tillage) on puddle quality, weed growth and yield of crop depends upon initial soil manipulations by pre-puddling tillage. However, the role of pre-puddling tillage on these aspects has not been studied adequately. These effects were studied for three years (1994±1996) in a ®eld experiment with a rice±wheat (Triticum aestivum L.) cropping system at Punjab Agricultural University, Ludhiana. Treatments included pre-puddling tillage treatments no tillage (PT0), one discing one harrowing (PT2) and one discing and three harrowings (PT4)) in rice in
combination with four tillage systems, varying in depth and intensity of soil disruption in wheat on puddle quality, weed growth and yield of rice and wheat on a sandy loam soil (Dystric Cambisol). Pre-puddling tillage improved puddle quality in terms of increased puddle depth and tended to decrease percolation rate. Weed infestation in rice decreased with increase in intensity of pre-puddling tillage. Mean dry weed biomass 35±40 days after transplanting was 1.6 Mg haÿ1
in PT0, 0.6 Mg haÿ1
in PT2and 0.5 Mg ha
ÿ1
in PT4. Leaving some area untilled between rows (strip tillage) in wheat resulted in a larger weed
biomass in rice, than with inversion of soil. Pre-puddling tillage did not affect rice yield during the ®rst two years but signi®cantly increased it during the third year when rice yield was 4.1 Mg haÿ1
in PT0compared with 5.8 Mg haÿ1in PT2and
6.1 Mg haÿ1in PT
4. Manual weeding at 40 days after transplanting masked the effect of pre-puddling tillage on rice yield. In
general, rice yield decreased exponentially with increase in weed biomass recorded at harvest of the rice crop. Pre-puddling tillage did not affect wheat yield signi®cantly. The results suggest that for effective weed control, high rice yield and water use ef®ciency, the ®eld must receive pre-puddling tillage at least once.#1999 Elsevier Science B.V. All rights reserved.
Keywords:Pre-puddling tillage; Weed infestation; Puddle quality; Rice yield
1. Introduction
Puddling is an integral part of rice (Oryza sativaL.) culture. Puddling controls weeds (De Datta and Bar-ker, 1978), reduces percolation losses, softens the soil
and reduces soil strength (Singh et al., 1995), and creates anaerobic soil conditions (Ponnamperuma, 1972). It also increases retention of soil water, helps in land levelling and maintenance of uniform water depth (Sharma and De Datta, 1986). The process of puddling is energy intensive and consists of primary (pre-puddling) and secondary (puddling) tillage. The pre-puddling tillage is aimed at mixing/burying stub-bles, amendments like lime and gypsum, manures,
*Corresponding author. Tel.: 401960; fax: +91-161-400945.
fertilizers, levelling the land and reducing weed growth.
Weed control has always been a major factor in rice production and is correlated with number of pre-puddling tillage operations (Barker, 1970). Manual weed control has gradually been replaced by chemical weed control. In general, tillage enhances herbicide effectiveness (Bhagat et al., 1996). However, inter-active effects of pre-puddling tillage and herbicide use in rice have not been investigated. Also the tillage (varying in depth and intensity of soil disruption) received by wheat (Triticum aestivum L.) in a rice± wheat system may also in¯uence weed infestation in rice. The effect of puddling/wet tillage on puddle quality in terms of puddling depth and percolation rate depends on initial soil conditions created by pre-puddling/dry tillage. Depth of puddling has been related to rice yields (Jo and Um, 1990), and excessive percolation loss increases the energy needed for pumping underground water for irrigation (Singh et al., 1990).
A random survey conducted by the authors in Punjab, India, showed that, in absence of speci®c recommendations, the number of pre-puddling opera-tions by the farmers usually depend upon the avail-ability/ownership of equipment and a tractor. In the major rice growing area in north±west Indo-Gangetic plains, 67% of the farmers apply 4±8 pre-puddling harrowings and discings (Chatha et al., 1994). How-ever, information on the effects of pre-puddling tillage on weed control, ef®ciency of resource management and yield of rice is lacking. The objective of this study was to assess the effect of intensity of pre-puddling tillage on puddle quality in terms of puddling depth and percolation rate, weed growth and yield of rice as in¯uenced by mode of weed control and tillage system in wheat.
2. Materials and methods
2.1. Site characteristics
A ®eld experiment was conducted for three years (1994±1996) at Punjab Agricultural University, Ludhiana, India (30856'N, 75852'E and 247 m above mean sea level). Mean monthly temperature and monthly rainfall during given seasons of rice and
wheat are given in Table 1. The soil was a sandy loam (USDA: Typic Ustochrept; FAO: Dystric Cambisol) containing 100, 150 and 750 g kgÿ1 clay, silt (2± 20mm) and sand, respectively in the top 0.30 m depth.
The soil was non-saline and with a low concentration of organic carbon (4 g kgÿ1) (Walkley and Black, 1934).
2.2. Treatments
The experiment was initiated in July 1994 with rice crop after the harvest of sun¯ower (Helianthus annuus
L.). The treatments included three intensities of pre-puddling tillage for rice in the main plot, and four tillage systems for the following wheat in the sub-plot, in a split plot design with three replications. Each sub-plot measured 4.2 m10 m. The pre-puddling tillage treatments in rice were (i) no pre-puddling tillage (PT0), (ii) one discing one week after harvest of the
previous cropone harrowing with a tine cultivator one week prior to puddling (PT2), and (iii) one discing
one week after harvest of the previous cropthree
harrowings with tine cultivator at weekly intervals after discing (PT4). First discing operation was 4±5
days after the ®eld had been irrigated immediately after the wheat crop was harvested. Subsequent dis-cing operations were done when the top 10 cm soil was air dry having soil water content of approximately 40 g kgÿ1
soil. Puddling was done by harrowing twice
Table 1
Mean monthly temperature and rainfall during different growing seasons
Season Temperature (8C) Rainfall (mm)
1994 1995 1996 1994 1995 1996
Rice
June 32.7 33.0 30.4 57 43 168
July 30.1 30.3 29.9 154 164 100
August 29.3 28.3 28.7 488 405 258 September 27.5 28.1 27.7 74 468 123
October 23.2 24.9 23.8 0 0 76
Wheat
November 19.6 18.9 18.9 0 3 0
December 14.1 13.8 13.8 5 5 0
January 13.3 11.3 12.0 50 24 0
February 14.3 14.1 15.0 51 66 7
March 20.4 17.7 20.1 20 26 0
with a tine cultivator in ponded water followed by planking (cultipacking i.e., levelling with a wooden bar).
In wheat, the four tillage systems consisted of (i) conventional tillage (CT) ± tilling the soil to 0.10 m depth by one run of a disc harrow, two runs of a tine cultivator followed by planking and seeding the crop with a seed-cum-fertilizer drill (a machine for simul-taneous placement of seed and fertilizer at pre-set depth and distance), (ii) deep-tillage (DT) ± sub-soil-ing with a ssub-soil-ingle tine chisel down to 0.40 m depth, 0.35±0.40 m apart followed by the same operations as in CT, (iii) deep plowing (DP) ± tilling the soil to 20
4 cm depth with a disc plow followed by the same
operations as in CT, and (iv) direct seeding of the crop with a strip-till drill (ST), which rotavated the soil in the seed zone and simultaneously placed the seed with a seed-cum-fertilizer drill. The strip-till drill left about 60% of the area between rows untilled.
2.3. Crop management
Four-week-old seedlings of rice, cultivar PR-108, were transplanted in 0.2 m wide rows with a distance of 0.15 m between plants (33 plants mÿ1) on 3 July 1994, 20 June 1995, and 18 June 1996 immediately after puddling. Each year the crop received 120 kg nitrogen (N) as urea, 20 kg phosphorus (P) as super-phosphate, 20 kg potassium (K) as potassium chloride, and 5 kg zinc (Zn) as zinc sulphate per hectare. All fertilizers except N were broadcast before puddling, and N was topdressed in three equal splits, viz. at transplanting, at 3 weeks and 6 weeks after transplant-ing.
For the ®rst 3 weeks continuous ponding of water (6.03.0 cm depth) was maintained in the ®eld. The subsequent irrigations were applied for two days after the disappearance of ponded water (Sandhu et al., 1980). Weeds were controlled by broadcasting 3 l haÿ1Butachlor 50 EW (water ¯owable emulsion) mixed with sand in standing water for three days after transplanting (DAT) and by manual weeding at 35 DAT. The crop was well protected against pests through two sprays, one each of Endosulfan 35 EC (emulsi®able concentrate) and Deltamethrin 28 EC.
The wheat cultivar HD-2329 was seeded at 100 kg haÿ1
between 14th and 16th November each year. The wheat crop received 120 kg N, 26 kg P and
24 kg K haÿ1
. The ®rst irrigation was applied for 4 weeks after seeding and subsequent irrigations at IW/ PE ratio (IWirrigation water and PEcumulative pan evaporation minus rainfall since previous irriga-tion) of 0.90 (Prihar et al., 1974). The weeds were controlled by spraying 600 ml of 2,4-D (34% EC) and 500 g (75 wettable powder) isoproturon in 500 l water haÿ1, 35±40 days after seeding.
2.4. Observations
During 1995 the mud depth, to ascertain depth of puddling, was measured 24 h after puddling by gently pushing a 2.5 mm diameter steel rod in the mud until it hit hard ground. Total daily percolation loss and evapotranspiration were periodically recorded during 1995 by measuring depth of the ponded water between 24 h periods starting at 0800 h. Permanent scales were ®xed in each plot for measuring the ponded water depth. During the ®rst two years manual weeding of whole plots was done 35 DAT. Dry mass of above-ground weeds, from a net area of 30 m2was recorded after washing and drying the weeds at 608C. During the third year, the weeds were removed randomly from half the area of each plot at 40 DAT and their dry mass from a net area of 15 m2was recorded. The unweeded half plots were kept as such, and dry weed biomass from weeded and unweeded parts of the plot was recorded at harvest. The crop was harvested manually in the ®rst week of October and the grain yield was recorded from a net area of 30 m2in the ®rst two years and from 15 m2in each half of the weeded and unweeded plot during the third year. The grain yield was computed at 15% grain water content. The in®ltration rate was measured with a double ring in®ltrometer 15 days after harvest of rice crop. The data are reported as steady state in®ltration rate reached 6 h after ponding of water in all the treat-ments.
Resistance to penetration was recorded in wheat during 1994 with a cone penetrometer (13 mm base and 308angle). These measurements were made when the soil water content was at ®eld capacity as recorded 24 h after the ®rst irrigation to wheat. At this stage water content of the soil was 160 g kgÿ1
for 0±0.3 m depth and 156 g kgÿ1
length at three sites in each plot and also weed dry biomass was recorded 60 days after seeding. Wheat was harvested manually in the mid April and grain yield was recorded from a net area of 30 m2.
Statistical signi®cance of the treatment effects on different parameters was inferred from the least sig-ni®cant difference using analysis of variance for a split-plot design (Steel and Torrie, 1960). The data for the ®rst rice crop were not analysed because of fewer degrees of freedom.
3. Results and discussion
3.1. Puddle quality
Pre-puddling tillage operations increased the pud-dling depth and tended to decrease the rate of loss of ponded water (Table 2). Mean of seven measure-ments for the rate of loss of ponded water during the growing season was 3.3 mm hÿ1 in PT0
com-pared to 2.7 mm hÿ1 in PT2 and PT4. Steady state
in®ltration rate measured after rice harvest in 1994 was 5 mm hÿ1in PT0and 2 mm h
ÿ1
in PT2and PT4
(data not shown).
3.2. Weed biomass
Weed biomass at 35±40 DAT was signi®cantly affected by pre-puddling tillage operations (Table 3). Across years weed biomass in PT0plots was 2±4 times
of that in PT2 and PT4 plots. The dominant weed
species in the experimental ®eld wereCyperus rotun-dus,Cyperus iria,Cyperus difformisandEchinochloa crusgalli.
Tillage received by wheat also showed signi®cant effects on weed biomass in rice during 1996 (data not included). Where rice followed strip-tilled wheat and received no pre-puddling tillage, the weed biomass at 40 DAT (in rice) was more than double that where wheat received conventional or deep tillage. Tillage system for wheat had no signi®cant effect on weed growth where pre-puddling tillage was done. As dis-cussed above, the strip-till system left 60% untilled area between wheat rows.
During 1996, weed biomass at rice harvest was also signi®cantly in¯uenced by pre-puddling tillage, tillage system in wheat, manual weeding at 40 DAT and their interactions (Table 4). Mean weed biomass in PT0
(1.9 Mg haÿ1
) was signi®cantly higher than PT2
(0.6 Mg haÿ1
) and PT4(0.3 Mg ha
ÿ1
). However, weed
Table 2
Effect of pre-puddling tillage on puddling depth measured 24 h after puddling and rate of loss of ponded water in rice during 1995
Days after
Effect of pre-puddling tillage on dry biomass of weeds in rice 35± 40 days after rice transplanting
Pre-puddling tillage Weed biomass (Mg haÿ1)
1994 1995 1996
None (PT0) 0.4a 1.7 2.8
One discingone harrowing (PT2) 0.1 0.9 0.7
One discingthree harrowings 0.1 0.8 0.5
LSD0.05 b 0.7 0.8
biomass in PT2 and PT4did not differ signi®cantly.
Manual weeding signi®cantly affected weed biomass in PT0and PT2but not in PT4. Among tillage systems
in wheat, the highest weed biomass was observed with ST and lowest with DP which inverted the soil. Effects of tillage to wheat were signi®cant only in PT0plots.
Also effects of pre-puddling tillage in rice or tillage systems to wheat on weed biomass in rice were signi®cant only in the absence of manual weeding. The results show that adequate pre-puddling tillage in rice is needed to check weed growth in rice. A tillage system which leaves some area untilled encourages perennial weeds which may affect weed biomass in rice. However, manual weeding at 35±40 DAT reduces the effect of pre-puddling tillage and tillage system in wheat on weed biomass in rice.
3.3. Rice yield
Grain yield of rice was not affected signi®cantly by pre-puddling tillage during 1994 and 1995. However, in 1995 grain yield in PT0was 13% lower than that in
PT2and PT4(Table 5). Overall low yields during 1994
were caused by a severe attack of paddy stem borer (Scirpophaga incertulasWlk.) despite recommended plant protection. During 1996 the average yield of
4.1 Mg haÿ1 in PT0 was signi®cantly lower than
5.8 Mg haÿ1in PT2and 6.0 Mg ha
ÿ1
in PT4. Manual
weeding at 40 DAT masked the effect of pre-puddling tillage on grain yield of rice, and the yield in weeded plots averaged 5.8 Mg haÿ1against 4.7 Mg haÿ1 for the unweeded plots. However, the maximum increase of 70% in grain yield because of weeding occurred in PT0plots. The corresponding increase in PT2and PT4
plots was about 11%. Although the mean yield of rice in plots with strip-till drill in wheat was about 0.6 Mg haÿ1
lower than that in the other tillage sys-tems but the differences were not statistically signi®-cant. Rice grain yield decreased with increase in weed infestation. In general pre-puddling tillage decreased weed infestation and thus increased the rice yield. A plot of grain yield of rice in 1996 against the corre-sponding weed biomass at harvest showed that rice yield decreased exponentially with increase in weed biomass (Fig. 1).
3.4. Wheat yield
Pre-puddling tillage in rice did not affect the yield of the following wheat in each of the three years. In the ®rst year after introduction of paddy, viz. 1994, wheat yield was not affected by pre-sowing tillage
Table 4
Effect of pre-puddling tillage on weed biomass at rice harvest as influenced by tillage system in wheat and mode of weed control in rice (1996)
Tillage system to wheat
Weed biomass (Mg haÿ1) (pre-puddling tillage) Mean
None (PT0) One discingone
harrowing (PT2)
One discingthree harrowings (PT4)
W0 W W0 W Wa
0 W
CT 4.0 0.4 0.6 0.1 0.6 0.1 1.0
DT 2.2 0.2 1.3 0.4 0.4 0.1 0.8
DP 1.3 0.4 1.0 0.3 0.6 0.2 0.6
ST 6.1 0.7 0.8 0.2 0.5 0.1 1.4
Mean 3.4 0.4 0.9 0.2 0.5 0.1
LSD0.05
Pre-puddling (A) 0.4
Tillage to wheat (B) 0.4
Weeding (C) 0.3
AB 0.8
AC 0.5
BC 0.5
CT: soil disruption to 0.1 m depth; DT: sub-soiling 0.4 m deep followed by CT; DP: soil inversion to 0.2 m depth followed by CT; ST: disruption to 0.1 m depth in 40% surface area only.
aW
(Table 6). However, in 1995 wheat yield with ST was lower than with other treatments. Tillage treatments did not affect emergence of seedlings signi®cantly. Therefore, the yield decrease in ST may be attributed to the greater weed infestation of the untilled area. Compared with the other treatments, ST had double the weed biomass at 60 days after seeding. The highest weed mass in rice occurred where it followed wheat
sown with strip-till drill. Sub-soiling (DT) in wheat also resulted in signi®cantly higher grain yield than CT and ST, probably due to better rooting induced by reduced soil strength in 10±20 cm layer (Gajri et al., 1991). Soil strength in 10±20 cm layer in this experi-ment at ®eld capacity was 2.33 MPa in ST, 1.45 MPa in DP and 1.40 MPa in DT (data not shown). Strip-till drill treatment could not be included during 1996. Although in this year also DT had the highest yield, differences among treatments were not statistically signi®cant.
Table 5
Effect pre-puddling tillage on grain yield of rice as influenced by tillage system in wheat and method of weed control in rice
Pre-puddling tillage Mode of weed control
Rice yield (Mg haÿ1)
1994 1995 1996 (tillage system in wheat)
CT DT DP ST Mean
None W0 ± ± 3.2 3.4 3.7 1.8 3.0
(PT0) W 3.8 4.6 4.7 5.7 5.7 4.2 5.1
One discingone harrowing (PT2) W0 ± ± 5.8 5.4 5.3 5.6 5.5
W 3.8 5.3 6.3 6.3 5.9 6.1 6.1
One discingthree harrowings (PT4) W0 ± ± 5.7 5.9 5.8 5.4 5.7
W 3.8 5.1 6.9 6.2 6.0 5.9 6.3
Mean 5.4 5.5 5.4 4.8
LSD0.05
Pre-puddling (A) ± NS 0.6
Weeding (B) ± ± 0.4
AB ± ± 0.7
CT: soil disruption to 0.1 m depth; DT: sub-soiling 0.4 m deep followed by CT; DP: soil inversion to 0.2 m depth followed by CT; ST: disruption to 0.1 m depth in 40% surface area only.
W0: without manual weeding;W: manual weeding at 40 days after transplanting.
Fig. 1. Grain yield of rice as influenced by dry biomass of weed recorded at crop harvest.
Table 6
Effect of different tillage systems on weed biomass recorded at 60 days after seeding, and yield of wheat
Tillage system
Weed biomass (Mg haÿ1)
Grain yield (Mg haÿ1)
1995 1994 1995 1996 Mean
CT 0.4 4.7 3.7 4.6 4.3
DT 0.3 4.9 3.9 4.9 4.6
DP 0.2 4.8 3.8 4.4 4.3
ST 0.7 4.8 3.5 ± 4.2
LSD0.05 0.2 NS 0.2 NS
4. Conclusions
Pre-puddling tillage improved puddle quality in terms of increased puddle depth and decreased per-colation rate. Also it increased rice yield by reducing weed infestation. For effective weed control, higher yields and better water use ef®ciency, the rice ®eld must receive pre-puddling tillage at least once. How-ever, the intensity of pre-puddling tillage depends upon the method of weed control (herbicide alone or in combination with manual weeding) and tillage system in the wheat. From the results it may be conclusively stated that the pre-puddling tillage is crucial for weed management in rice. It increases the effectiveness of herbicide and negates the impact of the tillage system in the previous crop on weed growth in rice. The results further show that pre-puddling tillage also in¯uences puddle quality in terms of puddling depth and percolation rate of water.
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