Soil physical environment as affected by double zero tillage in rice-wheat cropping system of north-west India

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1 An Asian Journal of Soil Science Volume 1 Issue 1 June, e ISSN Visit us : A Case Study DOI : /HAS/AJSS/1.1/ Soil physical environment as affected by double zero tillage in rice-wheat cropping system of north-west India RAJAN BHATT AND S.S. KUKAL MEMBERS OF RESEARCH FORUM: Corresponding author : RAJAN BHATT, Department of Soil Science, Punjab Agricultural University, LUDHIANA (PUNJAB) INDIA Co-authors : S.S. KUKAL, Department of Soil Science, Punjab Agricultural University, LUDHIANA (PUNJAB) INDIA Received : ; Accepted : Summary Highly productive rice (Oryza sativa L.) and wheat (Triticum aestivum L.) cropping systems are crucial for millions of rural and urbans in the Indo-Gangetic Plains (IGP) of south Asia. This intensive RWCS resulted in declining under groundwater table and degrading soil health. A number of resource conservation technologies are being propagated in the region to uplift declining water productivity and soil health. Among different propagated resource conservation technologies-double zero tillage (ZT-wheat) in both crops found to be adopted in the region at a large scale which lessens cost of cultivation with no-field preparation and no-pre-sowing irrigation factor. Further, as wheat sown in loose and anchored rice straw thus, emit burning of rice residues and finally, reduces air pollution and improves blank gold status (Soil organic carbon). Zero tillage supposed to improve the declining soil physical properties; crop and water productivity thought visible effects appeared after 4-5 years of adoption. The treatment included two tillage levels viz., conventional and zero tillage and three rice tillage viz., puddle, conventionally and zero tilled with two establishment methods viz., direct seeded rice (DSR) and mechanically transplanted rice (MTR). Objective of the present study was to delineate the effect of double zero tillage from on the soil physical environment and findings suggests that double tillage was not able to significantly effect of the physical properties of the soil as adaptation of CA based component technologies evolved over the time. Thus, best benefits of double zero tillage might be significant after 3-5 years of continuous adoption of the double zero tillage which further needs to be tested under different agro-climatic conditions under texturally divergent soils. Key words : Double zero tillage, Rice-wheat cropping system, Physical environment, Northwest India How to cite this article : Bhatt, Rajan and Kukal, S.S. (215). Soil physical environment as affected by double zero tillage in rice-wheat cropping system of north-west India. Asian J. Soil Sci., 1(1) : Introduction Rice wheat cropping system (RWCS) is the most important cropping system for food security in south Asia (13.5 M ha), providing food for more than 4 million people (Ladha et al., 23) but led to decline of underground soil water and deterioration of the soil health (Hira et al., 24; Kukal et al., 214) in the region. Conventionally, rice is established in puddle soils with heavy water and labour inputs (Dawe, 25), causes HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE

2 RAJAN BHATT AND S.S. KUKAL sub-surface compaction because of repeated puddlings of coarse and medium textured soils (Sur et al., 1981; Kukal and Aggarwal, 23a) restricts the root growth of wheat in addition to creating aeration stress (Kukal and Aggarwal, 23b). Puddling deteriorated soil physical properties by breaking down soil aggregates, induced changes in pore size distribution; the cone index decreased after puddling and gained strength during the subsidence stage of the puddle soil, and the bulk density of soil increased and hydraulic conductivity decreased 3 and 6 days after puddling. Generally farmers burnt the paddy residues at their field for timely sowing of wheat seeds during Rabi season which cause loss of huge nutrients as about 4 per cent of the N, 3-35 per cent of the P, 8-85 per cent of the K, and 4-5 per cent of the S absorbed by rice remains in the vegetative parts at maturity (Dobermann and Fairhurst, 2) which lost on burning which ultimately detonating the soil physico-chemical health. To address these challenges of RWCS, conservation agriculture (CA) based alternative tillage and crop establishment methods viz., ZTW-DSRZT have been designed and tested in IGP (Malik et al., 214 and Jat et al., 213). The conservation agriculture (CA) involves a paradigm shift from intensive tillage to zero or reduced tillage, establishment of permanent organic soil cover with economically viable crop rotation that complement reduced tillage and residue retention. Change in the soil physical properties as affected by the double zero tillage (ZTW-DSRZT) had a profound effect on the productivity, profitability and sustainability of the rice-wheat cropping system (Bhaduri and Purakayastha, 214 and Dikgwatlhe et al., 214). However, the magnitude of benefits of CA based technologies tends to be site and situation specific and cannot be overly generalized across farming systems (Hobbs, 27) and realized after 2 3 years as the adaptation of CA based component technologies evolved over the time (Jat et al., 214). Generally zero tillage adopted only during wheat season but to get the full benefits of ZT, both rice and wheat need to be grown with a double zero-tillage system (Jat et al., 26b and Bhushan et al., 27). However, few studies present in literature showing the effect of double zero tillage in the RWCS on the physical environment and still doubts are there as within two years, some studies showed the significant improvement. Keeping this objective in view, present investigation was made to evaluate the impact of double zero till (ZTW- 167 DSRZT) practised for two years on the different soil physical properties as compared to the conventional methods (CTW-DSRP). Resource and Research Methods Site description : The field experiments were carried out at the research farm (3 54 N, E, 247 m above sea level) of Punjab Agricultural University, Ludhiana, India, during The experimental soil was sandy loam (sand %, clay 11-3%), neutral to slightly alkaline, nonsaline and medium in soil organic carbon (.44%) in the surface layer (Table 1). The soil had sub-surface compact layer (bulk density of 1.74 Mg m -3 at 15-3 cm). The available nutrients were in the medium range while moisture content (%, g g -1 ) on an average decreased to 71.5 per cent from field capacity to permanent wilting point. The depth to the ground water at the site was around 24 m and the quality of water was good for all crops (Table 2). The experimental site was under puddle transplanted rice for the last 2 years except that the field was under direct dry-seeded rice (DSR-CT) sown under tilled conditions during the immediate previous year (212). The climate is subtropical with hot and dry summers (March-June), wet monsoon season (late June to mid-september) and a cool dry winter (October- February). The long-term average annual rainfall is 734 mm, 85 per cent of which occurs during a short period of July-September. Treatments and experimental design : The treatments consisted of zero- (direct-drilling of wheat in standing stubbles of the previous crop, ZTW) and conventional-tillage (disked twice followed by 2 passes of tractor-drawn cultivator and one planking, CTW) for wheat in main plots (13.8 m 25.1 m) with three replications. In the following rice crop, the main plots were splited into two sub-plots for differential rice establishment viz., direct-seeded rice (DSR) and mechanically transplanted rice (MTR). These subplots were further splited into three sub-sub plots of 49.7 m 2 (13.8 m 3.6 m) for differential tillage treatments in rice viz., puddle (P), dry and (CT) and zero-till (ZT). The tillage treatments in rice were randomly allocated in subplots of both DSR and MTR. During wheat season, rice straw load of 4.4 t ha -1 retained on ZTW plots while during rice season all the straw load was removed. As per objective of present investigation, initial soil physical HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE Asian J. Soil Sci., (June, 215) 1 (1) :

3 SOIL PHYSICAL ENVIRONMENT AS AFFECTED BY DOUBLE ZERO TILLAGE IN RICE-WHEAT CROPPING SYSTEM properties analyzed before onset of the experiment and then after practising double zero till for two years same physical properties analysed again to delineate any significant change. Measurement of different physical properties : Bulk density was determined by using the core sampler method (Bodman, 1942). In situ bulk density was calculated after obtaining undisturbed soil samples in metallic cores having internal diameter of 5.3cm and depth of 5.cm from different soil depths [Fig. A(d)]. The fresh weight of soil samples was recorded. The soil fill cores were oven-dried at 15 C for 24 hours and were weighted to record dry weight of the samples. The bulk density was then calculated as the ratio of dry weight of soil samples to the internal volume of the metallic core. The infiltration rate of field was determined using infiltrometer method [Fig. A(a)] (Herman, 1986) while for the particle size distribution for delineating the textural class of the soil was calculated using international pipette method (Piper, 1966) while organic carbon (%) estimated by Walkley and Black s rapid titration method (1934). a b The moisture content at the field capacity and permanent wilting point in different layers of the soil profile was determined by Pressure plate apparatus [Fig. A(b)] (Richard and Weaver, 1943). The aggregate size distribution was determined using wet sieving technique (Yoder, 1936). To represent aggregation status of soil mean weight diameter was calculated as follow : diwi i1 MWD n W n i1 i where, di is the mean weight diameter of each size fraction in mm, n is the number of size fractions and Wi is the weight of aggregates in the corresponding size fractions. Saturated (using guleph permeameter) and unsaturated (using disk permeameter) hydraulic conductivities throughout the soil profile was calculated using the disk permeameter [Fig. A(c)]. Research Findings and Discussion Efforts were made to evaluate the impact of double c d Fig. A : Measurement of different physical properties of the soil viz., infiltration rate (a), hydraulic properties (b), Hydraulic conductivity and bulk density HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 168 Asian J. Soil Sci., (June, 215) 1 (1) :

4 RAJAN BHATT AND S.S. KUKAL zero till (ZTW-DSRZT) on the different soil physical properties viz., bulk density, hydraulic conductivity, hydraulic properties (Moisture % w/w at FC and PWP), infiltration and aggregation. Following discussion covers the impact of double zero till technologies on the soil physical environment. Bulk density (mg m -3 ) : In the present investigation of two years (212-14), no significant effect of double zero till was observed on the bulk density throughout the soil profile upto 15 cm (Table 1) though surface soil (-15 cm) showed some increments. However, contrary to our study Jat et al. (29) reported that double zero till (ZTDSR-ZTW) had significantly higher bulk density in the 5 and 5 1-cm soil profile than with other tillage sys tems, wher eas it was higher under conventional-tillage (PTR-CTW and CTDSR-CTW) in the 1 15 and 15 2-cm soil layers compared with ZTDSR-ZT W. Published studies revealed that puddling induced high bulk density in subsurface layers (15 3 cm) in rice based systems (Sharma and De Datta, 1985; Hobbs and Gupta, 2). Hydraulic properties (Moisture content % w/w at FC and PWP) : The hydraulic properties throughout the soil profile (upto 15 cm) was not significantly improved as compared to the plots under conventional system (CTW- DSRP) (Table 1) and shorter time period might be one reason for that as the positive effect of conservation technologies realized after 2-3 years as the adaptation of CA based component technologies evolved over the time (Jat et al., 214). The moisture content almost reduced to half as the studied scenario shifted from FC to PWP. Table 1 : Physical properties as affected by double zero till scenario Bulk density (Mg m -3 Moisture content (% Moisture content (% ) w/w) at.3 bar (FC) w/w) at 15 bar (PWP) Soil depths ZTW- ZTW- ZTW-DSRZT DSRZT DSRZT Soil texture Sand %, (Clay %) ZTW- DSRZT Organic carbon (%) ZTW-DSRZT , (11.3) 64.8, (11.2) , (11.3) 66., (11.5) , (12.6) 66.6, (12.7) , (12.7) 68., (12.8) , (12.3) 68.4, (12.5) , (11.9) 68.9, (12.) (a) ZTWDSRZT 14 (b) ZTWDSRZT 2 12 Infiltration rate (cm hr -1 ) 15 1 Cumulative infiltration (cm) Fig. 1 : Cumulative time (minutes) Effect of double zero till plots on the infiltration rate (a) and cumulative infiltration (b) as compared to the conventional s ys te m 169 Cumulative time (minutes) HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE Asian J. Soil Sci., (June, 215) 1 (1) :

5 SOIL PHYSICAL ENVIRONMENT AS AFFECTED BY DOUBLE ZERO TILLAGE IN RICE-WHEAT CROPPING SYSTEM Organic carbon (%) : Organic carbon throughout the soil profile remained almost same and was not significantly affected by the double zero tillage of the wheat rice cropping system practised for the four seasons (Table 1) which might be because of retention of straw loads of 4.4 t ha -1 during wheat only. Further, it was observed that organic carbon decreased down the profile and after 3 cm almost no change observed in the double zero tilled plots as compared to the conventionally tilled plots viz., CTW- DSRCT plots. Soil texture : Double zero tillage technology in RWCS was not able to influence the soil texture at all after two years as per cent sand and clay remained almost same throughout the soil profile as it was before conduction of the experiment indicating that soil texture not influenced by double zero tillage (Table 1). Infiltration : Infiltration is the capacity of the soil with which it allowed the water to enter and the movement of the wetting front depends upon several pre-condition as texture of underlying soil, moisture content of the soil profile and it is an indicator of the soil health. At the end of our experiment, no significant improvement in the infiltration rate and cumulative infiltration was observed under the double zero till plots as compared to the conventional system (CTW-DSRP) (Fig. 1 a and b). However, slight improvement in the cumulative infiltration rate was observed in the double till plots. Jat et al. (29) also reported the similar infiltration rates in double zero till plots than the plots which were under CTW-PTR. Hydraulic conductivity : Hydraulic conductivity (cm s -1 ) is an important soil physical property and indicated the water intake conduction behaviour of the soil. During the current investigation hydraulic conductivities (both saturated and un-saturated) of the sandy loam soil reported to have non-significant effect by the double zero till viz., ZTW- DSRZT during the last four cropping seasons and it s range remained almost similar to that in the conventional system of rice-wheat establishment (Fig. 2). Hydraulic conductivity (cm sec -1 ) Fig. 2 : hydraulic conductivity After four zero till seasons Saturated Unsaturated Saturated Unsaturated Saturated and unsaturated hydraulic conductivity as affected by conventional and conservation tillage systems over the last four seasons Aggregation/mean weight diameter : The primary soil particles (sand, silt and clay) tend to cohere to form secondary particle called aggregate. The size distribution of aggregates in soils indicates retention of water as their size is important in determining the dimensions of pore space in cultivated soils. It was revealed that the mean weight diameter and percentage of weight retained in each size fraction remained almost similar and non-significant effect was observed in plots under conventional tillage and under conservation tillage (ZTW-DSRZT) from the last four seasons (Table 2 and Fig. 3). Contrary to result of present study, Jat et al. (29) double no-till (ZTDSR-ZTW) had significantly higher soil aggregates (>.25 mm) than conventional-tillage (PTR- CTW) which might be because of their retained straw load during both the seasons on to the soil surface in double ZT plots while in our study straw load of 44 t ha -1 retained only during the wheat season. Further, under conventional-tillage, soil aggregation was static across the seasons, whereas it improved over time under double Table 2: Per cent soil aggregates initially and doubles ZT plots from last four seasons Sieve size (mm) Per cent soil aggregates status ZTW-DSRZT > < HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 17 Asian J. Soil Sci., (June, 215) 1 (1) :

6 RAJAN BHATT AND S.S. KUKAL Mean weight diameter Fig. 3 : Unsaturated After four seasons zero till Mean weight diameter as affected by four season zero till plots no-till and permanent beds. The mean weight diameter of aggregates (average of all size groups) was significantly higher under ZTDSR-ZTW and increased over time compared with conventional-tillage (CTW- PTR). Conclusion : Double zero tillage viz., ZTW-DSRZT from wheat to rice 214 observed to have nonsignificant effect on the improvement of the different soil physical properties from the initial values. This might be because of the reason that conservation agriculture technologies components including double zero tillage evolved over the time. However, after 3-5 years onwards, double zero tillage (ZTW-DSRZT) had a profound improvement in the soil physical environment and thus, favourably effect on the productivity, profitability and sustainability of the ricewheat cropping system. The soil physical properties in terms of soil aggregation, steady-state infiltration rate and compaction does not significantly improved under the double zero-tillage system compared with conventional RWCS. Further evaluation of double zero tillage in RWCS need to be re-evaluated after 5 years and afterwards, double zero tillage may improve the soil physical environment significantly. Further evaluation of double zero tillage viz., ZTW-DSRZT in RWCS is recommended at different agro-climatic conditions under texturally divergent soils for more than 3-5 years to have significant improvement in the soil physical environment. Acknowledgment : Authors are extremely thankful to Department of Soil Science, Punjab Agricultural University, Ludhiana, India, for providing necessary facilities to carry out this study. Literature Cited Bhaduri, D. and Purakayastha, T.J. (214). Long-term tillage, water and nutrient management in rice wheat cropping system: Assessment and response of soil quality. Soil Till. Res., 144 : Bhushan, L., Ladha, J.K., Gupta, R.K., Singh, S., Tirol-Padre, Saharawat, Y.S., Gathala, M. and Pathak, H. (27). Saving of water and labour in rice-wheat systems with no-tillage and direct seeding technologies. Agron. J., 99 : Bodman, G.B. (1942). Nomogran for rapid calculation of soil density,water content and total porosity relationship. J. Am. Soc. Agron., 34 : Dawe, D. (25). Increasing water productivity in rice-based systems in Asia, past trends, current problems, and future prospects. Pl. Prod. Sci., 8 : DOI:1.1626/pps Dikgwatlhe, S.B., Chen, Z.D., Lal, R., Zhang, H.L. and Chen, F. (214). Changes in soil organic carbon and nitrogen as affected by tillage and residue management under wheat maize cropping system in the north China plain. Soil Till. Res., 144 : Dobermann, A. and Fairhurst, T.H. (22). Rice straw management. Better Crops Int., 16 : 7 9. Herman, B. (1986). Intake rate: Cylinder infiltrometer. In: Methods of soil analyseer-part 1. A Kute (ed) Agron No. 9. American Society of Agronomy, Madison, USA pp. Hira, G.S., Jalota, S.K. and Arora, V.K. (24). Efficient management of water resources for sustainable cropping in Punjab. Department of Soils, Punjab Agricultural University, Ludhiana, Res. Bull., 2pp. Hobbs, P.R. and Gupta, R.K. (2). Sustainable resource management in intensively cultivated irrigated rice wheat cropping systems of the Indo-Gangetic Plains of South Asia: Strategies and options. In International Conference on Managing Natural Resources for Sustainable Production in 21 st Century, February 2, New Delhi, India, pp. Hobbs, P.R. (27). Conservation agriculture: what is it and why is it important for future sustainable food production? J. Agric. Sci., 145 : 127. Jat, M.L., Gathala, M.K., Ladha, J.K., Saharawat, Y.S., Jat, A.S., Kumar, Vipin, Sharma, S.K., Kumar, V. and Gupta, R.K. (29). Evaluation of precision land leveling and double zerotill systems in the rice-wheat rotation: Water use, productivity, profitability and soil physical properties. Soil Till. Res., 15 : HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE Asian J. Soil Sci., (June, 215) 1 (1) :

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