- Email: [email protected]
Soil structure under different land uses
CATENA
Vol. 1l, 197-200
Braunscweig 1984
SOIL STRUCTURE UNDER DIFFERENT LAND USES P.K. Sharma, Manila, and G.C. Aggarwal, Ludhiana SUMMARY Structural status of soils under different land uses, viz. aerable, nativegrass land, tea planting and native forest, was studied using different structural indices. Landuse showed a signifi.lcant influence on soil structure. Water-stable aggregates ( > 0.25 mm dia), mean weight diameter and total porosity were signiticantly higher, whereas bulk density was significantly lower in tea than in aerable softs. In general, tea soils showed better structural status than other soil groups. It was observed that use of one index alone is not a satisfactory approach to soil structure evaluation. ZUSAMMENFASSUNG Untersucht wurde die Beeinflussung der Bodenstruktur durch unterschiedliche Landnutzung. Ausgew[ihlt wurden Ackerbau-, nattirliche Grasland, Tee- und Waldstandorte in der feucht-warmen Bergregion des Kangra Distrikts (H.P.) in Indien. Ftir die Bestimmung der" Bodenstruktur wurden folgende Faktoren zugrunde gelegt: Aggregatstabili~t, durchschnittliche AggregatgrfBe (mean weight diameter), Bodendichte und Gesamtporenvolumen. Unterschiedliche Landnutzung zeigte einen signifikanten EinfluB aufdie Bodenstruktur. So waren die Aggregatstabftit/it verbessert, die durchschnittliche Aggregatgr6Be und das Porenvolumen erh6ht und die Bodendichte geringer. Die Untersuchung zelgte, dab zur Evaluation der Bodenstruktur ein Strukturmerkmal allein nicht ausreicht. 1. INTRODUCTION Soil structure is a dynamic soil property, altered by any stress on soil, natural or artificial. Extensive data are available in literature showing the influence of manures, fertilizers, tillage, cropping systems and natural forest vegetation on soil structure (WILLIAMS & COOKE 1961, LOW 1972, BHUSHAN et al. 1973, SHARMA & BISWAS 1974, YADAV & SINGH 1976, VISWANATH & PILLA11978, GRIEVE 1980, HEWITT& DEXTER 1980). But most of these data do not provide any understanding about the influence of land use on soil structure under similar environmental conditions. These informations are essential to protect lands, especially marginal ones, from degradation of their productivity by putting them under appropriate land use pattern. This report compares the structural status of soils under four land uses- softs under cultivation of mainly cereals (aerable soils), natural grasses (grass land), tea planting (tea soils) and native forest vegetation (forest soils).
2.
MATERIALS AND METHODS The sites, representing aerable, grass land, tea, and forest soils, widely scattered in the
ISSN 0341 - 8162 © Copgnght lg84 bg CATENA VERLAG. D- 3302 Cremhngen- Destedt. W Germang
198
SHARMA& AGGARWAL
warm and wet mountainous zone o f Kangra district (H.P., India), were selected for this study. This area lies between the latitude 32* to 32"15'N and longitude 76*20' to 77"20'E. Soils, mostly Alfisols and Ultisols, owe their origin to igneous and metamorphic parent rocks, consisting mainly of granites and gneisses. Annual rainfall is about 200 cm. Sixty surface soil samples (0-15 cm), fifteen from each o f the four land uses, varying in texture from loamy sand to silty clay loam, were collected to determine water-stable aggregates > 0.25 m m dia. (YODER 1936), mean weight diameter (VAN BAVEL 1950), bulk density (PRIHAR & H U N D A L 1971), total porosity and organic carbon (titration method o f W A L K L E Y & BLACK). Total porosity was computed from bulk density using actual values of particle density o f soils. All determinations were m a d e immediately after the collection of soil samples.
Tab. 1: MEAN VALUES OF WATER STABLE AGGREGATES (W.S.A. >0.25 mm), MEAN WEIGHT DIAMETER (M.W.D.), BULK DENSITY, TOTAL POROSITY, AND ORGANIC CARBON AND THEIR CORRELATION COEFFICIENTS WITH ORGANIC CARBON IN SOILS UNDER DIFFERENT LAND USES. Land use Structural indices Aerable W.S.A. >0.25 mm (%)41.09 + 9.75 a r ~ 0.89** M.W.D. (mm) 2.44 + 0.51 a r ~ 0.56* Bulk density (g/cm 3) 1.54 + 0.08 b r = -0.63* Total porosity (%) 38.81 + 3.81 a r = 0.65** Organic carbon (%) 0.87 + 0.25 a
Grassland Tea 68.67 + 14.52 b 70.29 + 13.08 b r m 0.76** r m 0.76** 3.62 + 0.55 b 4.12 + 0.80 c r = 0.70* r = 0.90** 1.52 -I- 0.12 b 1.35 + 0.15 a r = -0.79** r = -0.74** 39.74 + 2.82 a 46.43 + 5.45 b r = 0.83** r = 0.67** 1.11 + 0.39 a,b 1.52 + 0.44 c
C.D. Forest (P = 0.05) 69.52 + 14.23 b 9.44 r = 0.75** 3.92 + 0.66 b,c 0.46 r = 0.63** 1.41 + 0.16 a 0.10 r = -0.74** 43.66 + 6.27 b 3.45 r ~ 0.62* 1.34 + 0.65 b,c 0.33
In a row, mean values followed by a common letter are not significantly different at 5% level. * Significant at 5% level (r = 0.514) ** Significant at 1% level (r = 0.641)
3.
R E S U L T S AND D I S C U S S I O N
Data in Table 1 reveal significant differences in the m e a n values o f all the structural indices of soil under different land uses. The variation in structural indices was significantly correlated with the organic carbon content o f soils. It accords well with most o f the published studies which exhibit significant dependence o f soil structure, especially aggregation, on organic carbon levels (BOEKEL 1963, Y A D A V & S I N G H 1976, GRIEVE 1980). According to G R E E N L A N D (1971) and H A M B L I N & G R E E N L A N D (1977), the type o f organic matter is as important as the a m o u n t in determining the structural stability of soils. Bulk density is negatively correlated with the organic carbon (CURTIS & POST 1964, SAINI 1966). The effect o f cultivation on soil tilth varies with the condition and moisture content o f soil and the type o f machinery used. Various reports indicate that the bulk density o f arable soils is higher than the soils under grasses, mostly due to the compaction caused by the harvesting machinery (WILLIAMS & COOKE 1961, L O W 1972, GRIEVE 1980). However,
SOIL STRUCTURE, DIFFERENT LAND USE
199
our results do not show any difference in the bulk density ofaerable and grass land soil. The reason could be the collction of soil clods for bulk density determination just after the cultivation of land. The determination of bulk density from core samples collected from cultivated soils after the crop harvest may show significant differences from those of grass land soils. The data in Table 1 further show that the structural status of soil is dependent on the structural index used for its evaluation. For instance, on the basis of water-stable aggregates and MWD, grass lands, tea, and forest soils had the same structural status, which was significantly better than those of aerable soils. But on the basis of bulk density and total porosity, only tea and forest soils had the best structure. BOEKEL (1963) and L O W (1972) also observed that in heavy clay soils total porosity was better structural index than the amount of water-stable aggregates obtained by wet-sieving. BRYAN (1971), while working on some English and Canadian soils, concluded that the efficiency of structural indices varied with the soil type. Hence, it is essential to use various indices simultaneously for the satisfactory evaluation of soil structure. In our study, on the basis of four indices the soil structure under different land uses follows the following trend: Tea = Forest > Grassland > Aerable soils
4.
CONCLUSION
These results clearly demonstrate the significant dependence of soil structure on land use" The land use which provides a continuous soil cover and avoids frequent soil manipulations, offers better opportunities for structural development. It is suggested to extend such studies to different agroclimatic zones in order to develop relation between soil structure and land use based upon different soil structural indices. REFERENCES
BHUSHAN, L.S., VARADE, S.B. & GUPTA, C.P. (1973): Influence of tillage practices on clod size, porosity and water retention. Indian Journal of Agricultural Sciences 43, 466-471. BOEKEL, P. (1963): The effect of organic matter on the structure of clay soils. Netherlands Journal of Agricultural Sciences 11, 250-263. BRYAN, R.B. (1971): The efficiency of aggregation indices in the comparison of some English and Canadian Soils. Journal of Soil Science 22, 166-178. CURTIS, R.O. & POST, B.W. (1964): Estimating bulk density from organic matter content in some forest soils. Soil Science Society America Proceedings 28, 285-286. GREENLAND, D.J. (1971): Changes in nitrogen status and physical conditions of soils under pastures. Soils and Fertilizers 34, 237-251. GRIEVE, I.C. (1980): The magnitude and significance of soil structural stability declines under cereal cropping. CATENA 7, 79-85. HAMBLIN, A.P. & GREENLAND, D.J. (1977): Effect of organic constituents and complexing metal ions on aggregate stability of some East Anglian soils. Journal of Soil Science 28, 410-416. HEWITr, J.S. & DEXTER, A.R. (1980): Effects of tillage and stubble management on the structure of a swelling soil. Journal of Soil Science 31,203-215. LOW, A.J. (1972): The effect of cultivation on the structure and other physical characteristics of grassland and aerable soils. Journal of Soil Science 23, 363-380. PRIHAK, S.S. & HUNDAL, S.S. (1971): Determination of bulk density of soil clod by saturation. Geoderma 5, 283-286. SAINI, G.1L (1966): Organic matter as a measure ofbulk density of soil. Nature 210, 1295-1296. SHARMA, J.S. & BISWAS, T.D. (1974): Role of different forms of phosphates in the mechanism of soil aggregation. Journal of Indian Society of Soil Science 22, 6-12.
200
SHARMA & AGGARWAL
VAN BAVEL, C.H.M. (1950): Mean weight diameter of soil aggregates as a statistical index of aggregation. Soil Science Society of America Proceedings 14, 20-23. VISWANATH, G.K. & PILLAI, S.C. (1978): Influence of superphosphate on the formation of waterstable aggregates. Journal of Indian Institute of Sciences 60, 1-8. WILLIAMS, 1LJ.B. & COOKE, G.W. (1961): Some effects of farmyard manure and of grass residues on soil structure. Soil Science 92, 30-39. YADAV, J.S.P. & SINGH, K. (1976): Effect of forest plantations on water-stable aggregates of soil. Journal of Indian Society of Soil Science 24, 363-368. YODER, R.E. (1936): A direct method of aggregate analysis and a study of the physical nature of erosion losses. Journal of American Society of Agronomy 28, 337-351.
Addresses of authors: P.K. Sharma, Department ofAgronomy, IRRI, P.O. Box 933 Manila, Philippines G.C. Aggarwal, Department of Soils, Punjab Agricultural University Ludhiana- 141004 (Pb.), India
Vol. 1l, 197-200
Braunscweig 1984
SOIL STRUCTURE UNDER DIFFERENT LAND USES P.K. Sharma, Manila, and G.C. Aggarwal, Ludhiana SUMMARY Structural status of soils under different land uses, viz. aerable, nativegrass land, tea planting and native forest, was studied using different structural indices. Landuse showed a signifi.lcant influence on soil structure. Water-stable aggregates ( > 0.25 mm dia), mean weight diameter and total porosity were signiticantly higher, whereas bulk density was significantly lower in tea than in aerable softs. In general, tea soils showed better structural status than other soil groups. It was observed that use of one index alone is not a satisfactory approach to soil structure evaluation. ZUSAMMENFASSUNG Untersucht wurde die Beeinflussung der Bodenstruktur durch unterschiedliche Landnutzung. Ausgew[ihlt wurden Ackerbau-, nattirliche Grasland, Tee- und Waldstandorte in der feucht-warmen Bergregion des Kangra Distrikts (H.P.) in Indien. Ftir die Bestimmung der" Bodenstruktur wurden folgende Faktoren zugrunde gelegt: Aggregatstabili~t, durchschnittliche AggregatgrfBe (mean weight diameter), Bodendichte und Gesamtporenvolumen. Unterschiedliche Landnutzung zeigte einen signifikanten EinfluB aufdie Bodenstruktur. So waren die Aggregatstabftit/it verbessert, die durchschnittliche Aggregatgr6Be und das Porenvolumen erh6ht und die Bodendichte geringer. Die Untersuchung zelgte, dab zur Evaluation der Bodenstruktur ein Strukturmerkmal allein nicht ausreicht. 1. INTRODUCTION Soil structure is a dynamic soil property, altered by any stress on soil, natural or artificial. Extensive data are available in literature showing the influence of manures, fertilizers, tillage, cropping systems and natural forest vegetation on soil structure (WILLIAMS & COOKE 1961, LOW 1972, BHUSHAN et al. 1973, SHARMA & BISWAS 1974, YADAV & SINGH 1976, VISWANATH & PILLA11978, GRIEVE 1980, HEWITT& DEXTER 1980). But most of these data do not provide any understanding about the influence of land use on soil structure under similar environmental conditions. These informations are essential to protect lands, especially marginal ones, from degradation of their productivity by putting them under appropriate land use pattern. This report compares the structural status of soils under four land uses- softs under cultivation of mainly cereals (aerable soils), natural grasses (grass land), tea planting (tea soils) and native forest vegetation (forest soils).
2.
MATERIALS AND METHODS The sites, representing aerable, grass land, tea, and forest soils, widely scattered in the
ISSN 0341 - 8162 © Copgnght lg84 bg CATENA VERLAG. D- 3302 Cremhngen- Destedt. W Germang
198
SHARMA& AGGARWAL
warm and wet mountainous zone o f Kangra district (H.P., India), were selected for this study. This area lies between the latitude 32* to 32"15'N and longitude 76*20' to 77"20'E. Soils, mostly Alfisols and Ultisols, owe their origin to igneous and metamorphic parent rocks, consisting mainly of granites and gneisses. Annual rainfall is about 200 cm. Sixty surface soil samples (0-15 cm), fifteen from each o f the four land uses, varying in texture from loamy sand to silty clay loam, were collected to determine water-stable aggregates > 0.25 m m dia. (YODER 1936), mean weight diameter (VAN BAVEL 1950), bulk density (PRIHAR & H U N D A L 1971), total porosity and organic carbon (titration method o f W A L K L E Y & BLACK). Total porosity was computed from bulk density using actual values of particle density o f soils. All determinations were m a d e immediately after the collection of soil samples.
Tab. 1: MEAN VALUES OF WATER STABLE AGGREGATES (W.S.A. >0.25 mm), MEAN WEIGHT DIAMETER (M.W.D.), BULK DENSITY, TOTAL POROSITY, AND ORGANIC CARBON AND THEIR CORRELATION COEFFICIENTS WITH ORGANIC CARBON IN SOILS UNDER DIFFERENT LAND USES. Land use Structural indices Aerable W.S.A. >0.25 mm (%)41.09 + 9.75 a r ~ 0.89** M.W.D. (mm) 2.44 + 0.51 a r ~ 0.56* Bulk density (g/cm 3) 1.54 + 0.08 b r = -0.63* Total porosity (%) 38.81 + 3.81 a r = 0.65** Organic carbon (%) 0.87 + 0.25 a
Grassland Tea 68.67 + 14.52 b 70.29 + 13.08 b r m 0.76** r m 0.76** 3.62 + 0.55 b 4.12 + 0.80 c r = 0.70* r = 0.90** 1.52 -I- 0.12 b 1.35 + 0.15 a r = -0.79** r = -0.74** 39.74 + 2.82 a 46.43 + 5.45 b r = 0.83** r = 0.67** 1.11 + 0.39 a,b 1.52 + 0.44 c
C.D. Forest (P = 0.05) 69.52 + 14.23 b 9.44 r = 0.75** 3.92 + 0.66 b,c 0.46 r = 0.63** 1.41 + 0.16 a 0.10 r = -0.74** 43.66 + 6.27 b 3.45 r ~ 0.62* 1.34 + 0.65 b,c 0.33
In a row, mean values followed by a common letter are not significantly different at 5% level. * Significant at 5% level (r = 0.514) ** Significant at 1% level (r = 0.641)
3.
R E S U L T S AND D I S C U S S I O N
Data in Table 1 reveal significant differences in the m e a n values o f all the structural indices of soil under different land uses. The variation in structural indices was significantly correlated with the organic carbon content o f soils. It accords well with most o f the published studies which exhibit significant dependence o f soil structure, especially aggregation, on organic carbon levels (BOEKEL 1963, Y A D A V & S I N G H 1976, GRIEVE 1980). According to G R E E N L A N D (1971) and H A M B L I N & G R E E N L A N D (1977), the type o f organic matter is as important as the a m o u n t in determining the structural stability of soils. Bulk density is negatively correlated with the organic carbon (CURTIS & POST 1964, SAINI 1966). The effect o f cultivation on soil tilth varies with the condition and moisture content o f soil and the type o f machinery used. Various reports indicate that the bulk density o f arable soils is higher than the soils under grasses, mostly due to the compaction caused by the harvesting machinery (WILLIAMS & COOKE 1961, L O W 1972, GRIEVE 1980). However,
SOIL STRUCTURE, DIFFERENT LAND USE
199
our results do not show any difference in the bulk density ofaerable and grass land soil. The reason could be the collction of soil clods for bulk density determination just after the cultivation of land. The determination of bulk density from core samples collected from cultivated soils after the crop harvest may show significant differences from those of grass land soils. The data in Table 1 further show that the structural status of soil is dependent on the structural index used for its evaluation. For instance, on the basis of water-stable aggregates and MWD, grass lands, tea, and forest soils had the same structural status, which was significantly better than those of aerable soils. But on the basis of bulk density and total porosity, only tea and forest soils had the best structure. BOEKEL (1963) and L O W (1972) also observed that in heavy clay soils total porosity was better structural index than the amount of water-stable aggregates obtained by wet-sieving. BRYAN (1971), while working on some English and Canadian soils, concluded that the efficiency of structural indices varied with the soil type. Hence, it is essential to use various indices simultaneously for the satisfactory evaluation of soil structure. In our study, on the basis of four indices the soil structure under different land uses follows the following trend: Tea = Forest > Grassland > Aerable soils
4.
CONCLUSION
These results clearly demonstrate the significant dependence of soil structure on land use" The land use which provides a continuous soil cover and avoids frequent soil manipulations, offers better opportunities for structural development. It is suggested to extend such studies to different agroclimatic zones in order to develop relation between soil structure and land use based upon different soil structural indices. REFERENCES
BHUSHAN, L.S., VARADE, S.B. & GUPTA, C.P. (1973): Influence of tillage practices on clod size, porosity and water retention. Indian Journal of Agricultural Sciences 43, 466-471. BOEKEL, P. (1963): The effect of organic matter on the structure of clay soils. Netherlands Journal of Agricultural Sciences 11, 250-263. BRYAN, R.B. (1971): The efficiency of aggregation indices in the comparison of some English and Canadian Soils. Journal of Soil Science 22, 166-178. CURTIS, R.O. & POST, B.W. (1964): Estimating bulk density from organic matter content in some forest soils. Soil Science Society America Proceedings 28, 285-286. GREENLAND, D.J. (1971): Changes in nitrogen status and physical conditions of soils under pastures. Soils and Fertilizers 34, 237-251. GRIEVE, I.C. (1980): The magnitude and significance of soil structural stability declines under cereal cropping. CATENA 7, 79-85. HAMBLIN, A.P. & GREENLAND, D.J. (1977): Effect of organic constituents and complexing metal ions on aggregate stability of some East Anglian soils. Journal of Soil Science 28, 410-416. HEWITr, J.S. & DEXTER, A.R. (1980): Effects of tillage and stubble management on the structure of a swelling soil. Journal of Soil Science 31,203-215. LOW, A.J. (1972): The effect of cultivation on the structure and other physical characteristics of grassland and aerable soils. Journal of Soil Science 23, 363-380. PRIHAK, S.S. & HUNDAL, S.S. (1971): Determination of bulk density of soil clod by saturation. Geoderma 5, 283-286. SAINI, G.1L (1966): Organic matter as a measure ofbulk density of soil. Nature 210, 1295-1296. SHARMA, J.S. & BISWAS, T.D. (1974): Role of different forms of phosphates in the mechanism of soil aggregation. Journal of Indian Society of Soil Science 22, 6-12.
200
SHARMA & AGGARWAL
VAN BAVEL, C.H.M. (1950): Mean weight diameter of soil aggregates as a statistical index of aggregation. Soil Science Society of America Proceedings 14, 20-23. VISWANATH, G.K. & PILLAI, S.C. (1978): Influence of superphosphate on the formation of waterstable aggregates. Journal of Indian Institute of Sciences 60, 1-8. WILLIAMS, 1LJ.B. & COOKE, G.W. (1961): Some effects of farmyard manure and of grass residues on soil structure. Soil Science 92, 30-39. YADAV, J.S.P. & SINGH, K. (1976): Effect of forest plantations on water-stable aggregates of soil. Journal of Indian Society of Soil Science 24, 363-368. YODER, R.E. (1936): A direct method of aggregate analysis and a study of the physical nature of erosion losses. Journal of American Society of Agronomy 28, 337-351.
Addresses of authors: P.K. Sharma, Department ofAgronomy, IRRI, P.O. Box 933 Manila, Philippines G.C. Aggarwal, Department of Soils, Punjab Agricultural University Ludhiana- 141004 (Pb.), India