Availability and Conditions of Agricultural Machinery in Public and Private Sectors of Borno State, Nigeria Arid Zone Journal of Engineering, Technology and Environment. October, 2004; Vol.4, 63-70 Copyright© Faculty of Engineering, University of Maiduguri, Nigeria. Print ISSN: 1596-2490, Electronic ISSN: 2545-5818 www.azojete.com.ng THE INFLUENCE OF ORGANIC MATTER ON SOIL COMPACTIBILITY AND AIR PERMEABILITY OF SOME SOILS IN BORNO STATE Mamman, E.1 and J.O. Ohu1 Abstract A laboratory experiment was conducted to determine the influence of an organic material (groundnut haulms) on the compactibility and air permeability of three most common agricultural soils (clay, sandy clay and sandy loam) in Borno state. The organic material was incorporated into the soils at three levels (2, 4 and 6% by mass of dry soil) and the soil-organic matter mixtures were compacted at three levels (5, 15 and 25 hammer blows). Incorporation of the organic material into the soils reduced their bulk densities and increased their air permeabilities. The bulk density for Ngala town clay, Nguma sandy clay and University sandy loam soils when incorporated with 2% organic matter and compacted using 25 hammer blows at 10% moisture content were 1.50, 1.59 and 1.74 Mgm-3 respectively. When the organic matter level was increased to 6% and compacted at 10% moisture content using 25 hammer blows, the bulk densities of the soils reduced to 1.41, 1.49 and 1.63 Mgm-3 for Ngala town clay, Nguma sandy clay and University sandy loam respectively. The air permeability for Ngala town clay, Nguma sandy clay and University sandy loam soils when incorporated with 2% organic matter and compacted using 25 hammer blows at 25% moisture content were 17, 23 and 37 μm² respectively. When the organic matter level was increased to 6% and compacted at 25% moisture content using 25 hammer blows, the air permeability of the soils increased to 28, 32 and 48 μm² for Ngala town clay, Nguma sandy clay and University sandy loam, respectively. For each level of organic material, air permeability of each soil decreased with increase in the number of hammer blows. Incorporation of the organic material into the clay soil increased its susceptibility to compaction and this resulted in much lower values of air permeability than in the sandy loam soil. Statistical models were generated to predict the air permeability of the soils in terms of silt and clay contents, moisture content, compaction and organic material levels. The implications of the results obtained in determining severity of compaction on these agricultural soils were discussed. 1. Introduction Soil compaction caused by increasing weights of agricultural machinery can affect the structure of arable soils either positively or negatively. The degree to which soil compaction affects soil physical properties and consequently crop yields is dependent upon soil type, the number of tractor passes, tyre contact pressure, soil moisture content at the time of compaction and crop type (Voorhees, 1977; Oni and Adeoti, 1986; Ohu and Folorunso, 1989). Soil compaction reduces soil porosity and thereby deteriorates soil aeration by curtailing the exchange of air from the root zone with air from the surface (Negi et al., 1980). Compaction can reduce the transmission of water and air through the soil profile, change the heat capacity, increase surface runoff and increase potential of erosion (Al-Adawi and Reeder, 1996). Soil compaction increased soil bulk density, soil shear strength, penetration resistance and reduced hydraulic conductivity and pore numbers in a vertisol (Boone et al., 1994; Radford et al., 2000). Lowery and Schuler (1988) reported that a soil compacted with a 12.5 to 18 Mg axle load reduced maize yield considerably in a rainy year and in a dry year (Voorhees, 1992) but not in years with normal precipitation. Besides grain and dry matter yield of crops, product quality can also be affected by soil compaction (Alakukku and Elonen, 1995). Soil compaction by a 5 to 20 Mg axle loads 1Department of Agricultural & Environmental Resources Engineering, University of Maiduguri. Nigeria. E-mail: mamman2002ng@yahoo.com mailto:mamman2002ng@yahoo.com http://www.azojete.com.ng The Influence of Organic Matter on Soil Compactibility and Air Permeability of some Soils in Borno State 64 delayed the ripening of maize, raising the grain moisture content at harvest and thus the drying costs for several years (Gaultney et al., 1982; Voorhees et al., 1989). Similarly, soil compaction decreased the yields and nitrogen uptake of oats, wheat and barley and lowered seed moisture contents of these crops at harvest (Alakukku and Elonen, 1995). Kayombo (1989) stated that not all instances of soil compaction are necessarily harmful. It was noted that in some dry climates a rather heavy compaction of highly permeable sandy soils might improve the efficiency of scarce rainfall and irrigation. In a field experiment with a sandy loam soil, the highest grain yield of sorghum (Ohu et al., 1991) and millet (Mamman and Ohu, 1997; Mamman and Ohu, 1998) were at 15 tractor passes, while zero pass gave the least. Bicki and Siemens (1990) found positive response of corn and soybean yields to wheel traffic when rainfall was limiting and negative when rainfall was adequate. Compacted soils may recover naturally if compaction forces are no longer applied. Natural recovery is, however, a slow process and depends on geographical location (Al-Adawi and Reeder, 1996). Some of the factors considered to alleviate soil compaction are wetting/drying, freezing/thawing, biological activity and tillage (Hakansson and Reeder, 1994). A legume, stylosanthes guianensis was found to be suitable for restoring compacted and eroded Alfisols in West Africa (Lal et al., 1979). Ohu et al. (1991) also reported that groundnut haulms alleviated soil compaction and improved the hydraulic properties of some agricultural soils in Borno state. The incorporation of organic material into the soil can reduce its compactibility and thus improve its physical and hydraulic properties (Ekwue, 1990; Ohu et al., 1991). Stone and Ekwue (1995, 1996) reported that incorporation of peat and sewage sludge into some soils in Trinidad increased their compressibility due to increase in void ratio of the soils and hence their porosities. They concluded that the extent of increased compressibility with organic matter addition depends on the properties of the organic matter, particularly its dry density. Soil compaction is measured indirectly by studying the changes in one or more soil parameters such as cone index, bulk density, porosity, hydraulic conductivity and air permeability (Al-Adawi and Reeder. 1996). Many researchers use cone penetration measurements as indicator of soil compressibility because it provides a rapid, simple and economical means of indicating compaction (Perumpral, 1987). One of the most frequently used measures of soil compaction is bulk density. Within a given soil, the bulk density provides a measure of how close the soil particles are packed but does not yield any information about their geometric arrangement or the pore size distribution (Freitag, 1971). Measurements of fluid flow through a soil provide a meaningful description of compaction, because the fluid conductivity is related, generally, to the amount of pore space in the soil (Al- Adawi and Reeder, 1996). Air permeability, which is a measure of air flow through a soil has been observed to have a good physical basis to indicate changes in free interconnected pore spaces which in turn determines aeration limitation in soils (Bowen et al., 1983). In Borno state, little information is available on the behaviour of agricultural soils to air permeability when they are incorporated with organic materials, especially when subjected to different pressures. Due to lack of this information, enormous quantities of crop residues and animal wastes are either not properly utilized or wasted completely. The objective of this AZOJETE Vol. 4 2004 65 study was, therefore, to quantify the effect of an organic material on soil compactibility and air permeability of some agricultural soils. 2. Materials and methods Three soils representing some of the major agricultural soils in Borno state (Ngala clay soil, Nguma sandy clay soil and University sandy loam soil) were used for the purpose of this study. The soils were collected from the top 0.20 m depth of the soil profile, air-dried and ground to pass a 0.05 m screen. Particle size distribution was determined using the hydrometer method (Lambe, 1951) and organic matter content using the method described by Walkley and Black (1934). The organic material (groundnut haulms) was grounded and passed through a 0.05 m sieve. The organic material was added to the soils at the rate of 2, 4 and 6% by mass of dry soil. For the purpose of determining the physical properties of the soils, water was added to the soil- organic material mixtures to bring up their gravimetric moisture contents to 5, 8, 10, 12 and 15% for the sandy soil and 10, 15, 18, 20 and 25% for the clay soils. These moisture content values were chosen according to the consistency limits of the soils (Ohu et al., 1989). Thereafter, each of the soils was subjected to three levels of compaction energy using 5, 15 and 25 blows of a standard proctor compaction hammer in cylindrical moulds of 102 mm in diameter by 116 mm height, following the proctor compaction procedure (Lambe, 1951). The choice of the three levels of compaction was borne from the equivalent static pressures for soil compaction as determined by Raghavan and Ohu (1985). For each level of compaction, the air permeability of the soils were determined using the air permeameter designed, constructed and calibrated by Ohu et al. (1992). A randomized complete block design was used for the investigation. All the tests were performed three times on each soil. The data collected was subjected to statistical analysis to determine the effects of soil type, organic material, moisture content and compaction level on air permeability of the soils. 3. Results and discussion The results of the grain size analyses of the soils used and their consistency limits are shown in Table 1. The sandy loam and sandy clay soils are classified as Typic Ustipsament (Rayar, 1984) while the clay soil is classified as Vertisol (FAO/UNESCO, 1974). Table 2 shows the dry bulk density of the soil-organic material mixtures. The dry bulk densities of these soils without organic material incorporation, compacted at 10% moisture content using 25 hammer blows were 1.53, 1.62, and 1.80 Mgm-3 for Ngala clay, Nguma sandy clay and University sandy loam respectively (Ohu et al., 1989). The incorporation of 2% organic material into these soils at 10% moisture content and compacted using 25 hammer blows reduced their bulk densities to 1.50, 1.59 and 1.74 Mgm-3 for Ngala clay, Nguma sandy clay and University sandy loam respectively. The Influence of Organic Matter on Soil Compactibility and Air Permeability of some Soils in Borno State 66 10 20 30 40 50 5 15 25 5 15 25 Blows 5 15 25 5 15 25 Blows 5 15 25 5 15 25 Blows Moisture Content (%, w/w) Figure 1: Air permeability vs moisture content for Ngala clay soil at different organic matter levels and proctor number of blows 20 30 40 50 5 15 25 5 15 25 Blows 5 15 25 5 1 5 25 Blows 5 15 25 5 1 5 2 5 Blows Moisture Content (%, w/w) Figure 2: Air permeability vs moisture content for Nguma clay loam soil at different organic matter levels and proctor number of blows A ir Pe rm ea bi lit y, µm 2 A ir Pe rm ea bi lit y, µm 2 2% 4% 2% 4% AZOJETE Vol. 4 2004 67 35 45 55 65 5 15 25 5 15 25 Blows 5 15 25 5 15 25 Blows 5 15 25 5 15 25 Blows Moisture Content (%, w/w) Figure 3: Air permeability vs moisture content for University sandy loam soil at different organic matter levels and proctor number of blows Table 1: Particle size analysis and initial organic matter content of the soils Sample location Soil type Sand (%,w/w) Clay (%,w/w) Silt (%,w/w) Organic content Moisture content (%,w/w) LL PL PI Ngala town Clay 5 60 35 0.97 46.0 25.0 21.0 Nguma Village Sandy clay 47 46 7 0.14 28.5 17.0 11.5 University Farm Sandy loam 77 17 6 0.12 21.0 - - LL= liquid limit; PL= plastic limit; PI= plasticity index Table 2: Dry bulk density of the soil-organic matter mixtures at 10% moisture content and 25 hammer blows Soil type Dry bulk density at three organic matter levels (Mgm-3) 2% 4% 6% Ngala town clay 1.50 1.46 1.41 Nguma sandy clay 1.59 1.53 1.49 University sandy loam 1.74 1.69 1.63 Figures 1 to 3 show the variations of air permeability with moisture content for the soils used. For all the soils, air permeability increased with organic matter but decreased with increase in A ir Pe rm ea bi lit y, µm 2 2% 4% The Influence of Organic Matter on Soil Compactibility and Air Permeability of some Soils in Borno State 68 the number of hammer blows. In Figure 1 for example, the air permeabilities of the soil compacted at 25% moisture content using 5 hammer blows were 31, 38 and 39 for 2 , 4 and 6% organic matter levels respectively. When the soil was compacted using 15 hammer blows at 25 % moisture content, the air permeability decreased to 27, 34 and 36 for 2, 4 and 6% respectively. This trend was the same for the other soil types (Figures 2 and 3). The increases in air permeability with organic matter were statistically significant at 5% level. This could be attributed to increase in porosity of the soils as indicated by the decrease in their soil bulk densities. The figures also show that irrespective of the soil type, organic matter content and moisture content at which the load was applied, the air permeability values peaked at specific moisture contents for the 5 and 15 hammer blows. The low bulk densities of the mixtures and the high values of air permeability at high organic matter levels indicate that the organic material has affected the soils positively. The significant differences recorded in air permeability were a function of not only the organic material but also of silt and clay contents, moisture content and number of hammer blows. To establish relationships among these variables, multiple regression equations were used. The relationships that best described the air permeability of these soils were as follows: A = 0.64 - 1.38M + 2.18X + 1.66S (R2 = 72 %) 1 A = 0.36 + 3.57M + 4.12X - 2.19C (R2 = 79 %) 2 A = 0.89 + 5.24M + 3.85X + 2.46G (R2 = 92 %) 3 Where A is air permeability (μm2), M is moisture content (%, w/w), X is compaction level (MPa), S is silt content (%, w/w), C is clay content (%, w/w), G is organic matter level (%). The inclusion of organic matter level gave the best correlation as revealed by Equation 3. It is therefore evident that the organic material incorporated into the soils cushioned the effect of compaction, and improved the structure of the soils. 4. Conclusion This study revealed that incorporation of groundnut haulms into the soils considered would reduce the problem of compaction and improve soil structure by reducing the dry bulk density and creating more voids for more air circulation. This is particularly beneficial in the area of study where tillage operations are carried out with heavy tractors and where large quantities of the organic material are available. Although this organic material is used to feed domestic animals, our survey indicated that the economic returns would be more when incorporated into soils. It is, however, recommended that further studies be carried out to determine the optimum quantities of this organic material that can alleviate compaction and improve the structure of these soils. References Al-Adawi, S.S. and R.C. Reeder (1996). Compaction and subsoiling effects on corn and soybean yields and soil physical properties. Trans. ASAE, 5: 1641-1649. AZOJETE Vol. 4 2004 69 Alakukku, L. and P.Elonen (1995). Long-term effects of a single compaction by heavy field traffic on yield and nitrogen uptake of annual crops. Soil Tillage Res., 36: 141- 152. Bicki, T.J. and J.C. Siemens (1990). Crop response to wheel traffic soil compaction. Trans.ASAE, 34 (3): 909-913. Boone, F.R., G.D. Vermeulen and B. Kroesbergen (1994). The effect of mechanical impedance and soil aeration as affected by surface loading on the growth of peas. Soil Tillage Res., 42: 237-251. Bowen, H.D., P. Ayers and M. Salyani (1983). Air permeability as an aeration criterion. In: Conf. Proc. 13-16 December. ASAE 56, St. Joseph, M.I. Ekwue, E.I. (1990). Organic matter effects on soil strength properties. Soil Tillage Res., 16: 280-288. FAO/UNESCO (1974). Soil map of the world, 1: 5000000. Vol.1, Legend sheet and memoirs, Paris, 59pp. Freitag, D. (1971). Methods of measuring soil compaction. In: Compaction of agricultural soils, K.K. Barnes et al.(editors), 47-103. St. Joseph, Mich., ASAE. Gaultney, L., G.W. Krutz, G.C. Steinhardt and J.B. Liljedahl (1982). Effects of subsoil compaction on corn yields. Trans. ASAE. 25: 563-569. Hakansson, I. and R.C. Reeder (1994). Subsoil compaction by vehicles with high axle load- extent, persistence and crop response. Soil Tillage Res., 277-304. Kayombo, B. (1989). Soil compaction in the tropics and some means of alleviating it. Proc.of 11th Int. Congress on Agricultural Engineering, Dublin 4th – 8th September, Vol 3. Vincent A. Dodd and Patrick M. Grace (editors). Lal, R., G.F. Wilson and B.N. Okigbo (1979). Changes in properties of an Alfisol produced by various crop covers. Soil Science, 27: 377-382. Lambe, T.W. (1951). Soil testing for Engineers. John Wiley and Sons, Inc., New York. Lowery, B. and R.T. Schuler (1988). Effects and duration of compaction on soil and plant growth. Proc. of 11th Int. Conf. ISTRO, 11th – 15th July, Edinburgh, UK, pp.293-298. Mamman, E. and J.O. Ohu (1997). Millet yield as affected by tractor traffic in a sandy loam soil in Borno State, Nigeria. Soil Tillage Res., 42: 133-140. Mamman, E. and J. O. Ohu (1998). The effect of tractor traffic on air permeability and millet production in a sandy loam soil in Nigeria. Ife Jour. of Tech., 8 (1): 1-7. Negi, S.C., E. Mckyes, F. Taylor, E. Douglas and G.S.V. Raghavan (1980). Crop performance as affected by traffic and tillage in a clay soil. Trans ASAE, 23 (6): 1364- 1368. Ohu, J.O. and O.A. Folorunso (1989). The effect of machinery traffic on the physical properties of a sandy loam soil and on the yield of sorghum in north-eastern Nigeria. Soil Tillage Res., 13: 399-405. Ohu, J.O., E.I. Ekwue and J.B. Ndirmbita (1992). A simple air permeameter for agricultural research. Ife Jour. of Techn. In.press. Ohu, J.O., O.A. Folorunso and E.I. Ekwue (1991). The influence of tractor traffic on crop production in a semi-arid region of Nigeria. Proc. 12th Int. Conf. of ISTRO, IITA, Ibadan, Nigeria, pp. 238-245. Ohu, J.O., O.A. Folorunso, F.A. Adeniji and G.S.V. Raghavan (1989). Critical moisture content as an index of compactibility of agricultural soils in Borno State of Nigeria. Jour. of Soil Technology, 2:211-219. Oni, K.C. and J.S. Adeoti (1986). Tillage effects on differently compacted soil and on cotton yield in Nigeria. Soil Tillage Res., 8:89-100. The Influence of Organic Matter on Soil Compactibility and Air Permeability of some Soils in Borno State 70 Perumpral, J.V. (1987). Cone penetrometer applications - a review. Trans ASAE, 30 (4): 938- 944. Rayar, A.J. (1984). University of Maiduguri farm development planning report for Faculty of Agriculture, Annex A, soil survey details. Raghavan, G.S.V. and J.O. Ohu (1985). Prediction of static equivalent- pressure of proctor compaction blows. Trans. ASAE, 28 (5): 1398-1400. Radford, B.J., B.J. Bridge, R.J. Davis, D. McGarry, U.P. Pilai, J.F. Rickman, P.A. Walsh and D.F. Yule (2000). Changes in the properties of a vertisol and responses of wheat after compaction with harvest traffic. Soil Tillage Res., 54: 155-170. Stone, R.J. and E.I. Ekwue (1995). Compressibility of some Trinidadian soils as affected by the incorporation of peat. J. of Agric. Engn. Res., 60: 15-24. Stone, R.J. and E.I. Ekwue (1996). Soil compressibility as influenced by sewage sludge incorporation. J. of Agric. Engn. Res., 64: 227-236. Voorhees, W.B. (1977). Soil compaction: how it influences moisture, temperature, yield and root growth. Crop Soil Management, 29: 7-10. Voorhees, W.B. (1992). Wheel-induced soil physical limitations to root growth. Advanced Soil Science, 19: 73-95. Voorhees, W.B., J.F. Johnson, G.W. Randall and W.W. Nelson (1989). Corn growth and yield as affected by surface and subsoil compaction. Agronomy Journal, 81:294-303. Walkley, A. and I.A. Black (1934). An examination of the effect of the Degtjareff method for determining soil organic matter and a proposed modification of the chromic acid titration method. Soil Sci., 37: 29-38. Abstract 1. Introduction