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Soil physicochemical quality in contrasting tillage systems and its effect on nodulation and nodulation effectivity of groundnut, Bambara groundnut and soybean in a degraded Ultisol in Agbani, Enugu Southeastern Nigeria
Rhizosphere 1 (2016) 14–16
Contents lists available at ScienceDirect
Rhizosphere journal homepage: www.elsevier.com/locate/rhisph
Soil physicochemical quality in contrasting tillage systems and its effect on nodulation and nodulation effectivity of groundnut, Bambara groundnut and soybean in a degraded Ultisol in Agbani, Enugu Southeastern Nigeria M.A.N. Anikwe n, J.C. Eze, M.C. Chima, E.E. Ikenganyia Department of Agronomy and Ecological Management, Enugu State University of Science and Technology, Enugu, Nigeria
art ic l e i nf o
a b s t r a c t
Article history: Received 29 March 2016 Received in revised form 17 May 2016 Accepted 17 May 2016 Available online 11 June 2016
Soil health is an important factor that affects the efficiency of plant growth-promoting bacteria (PGPB) in the rhizosphere. A field trial was conducted at a Farm site in Enugu Southeastern Nigeria (6° 29′N; 7° 54′ E) to evaluate the effect of conventional tillage [CT] and no tillage [NT]) on soil properties, nodulation, and nodulation effectivity of groundnut (Arachis hypogaea), Bambara groundnut (Vigna subterranean L) and Soybean (Glycine max) in a Typic Paleustult. A Randomized Complete Block Design with six treatments and four replications was used. Soil quality attributes, nodulation and nodulation effectivity of the legumes were measured at 60 DAP. Results showed relatively higher bulk density (BD), gravimetric water content (GWC), Soil organic carbon (SOC), total nitrogen (N) and lower hydraulic conductivity in NT plots when compared to CT plots. A lower number of root nodules was found in NT plots when compared to CT plots depicting that soil compaction in the NT plots negatively affected nodulation. However, a higher number of effective nodules was found in NT plots indicating that NT plots provided better rhizospheric conditions for nitrogen fixation and therefore, improved soil productivity. & 2016 Elsevier B.V. All rights reserved.
Keywords: Tillage Nodulation Rhizobacteria Ultisol
1. Soil health, plant growth promoting bacteria and rhizosphere Soil health has been defined as: “the capacity of soil to function as a living system”. Healthy soils preserve a diverse community of soil organisms that form valuable symbiotic associations with plant roots, recycle essential plant nutrients, improve soil structure with positive repercussions for soil water and nutrient holding capacity, and ultimately improve crop production (FAO, 2008). No-till farming techniques have gained great popularity over the past two decades as growers seek new ways to protect and conserve their soil and save time and money (Soane et al., 2012). Conservation tillage reduces soil disturbances, protects the soil against degradation and improves sustainability (Meiero et al., 2009; Ibudialo and Anikwe, 2015). Soil compaction is one of the major problems facing modern agriculture. Compaction affects the activity of soil organisms by decreasing the rate of decomposition of soil organic matter and subsequent release of nutrients.
Plant-microbe interactions in the rhizosphere influence plant health, productivity and soil fertility (de Souza et al., 2015). The plant growth-promoting bacteria (PGPB) belong to a beneficial and diverse group of microorganisms that can be found in the rhizosphere, on the root surface or associated with it. Several important bacterial characteristics, such as biological nitrogen fixation and phosphate solubilization can be assessed as plant growth promotion traits (Carvalhais et al., 2013). Soil health is an important factor that affects PGPB efficiency, due to several characteristics such as soil type, nutrient pool, soil moisture, microbial diversity, and soil disturbances caused by management practices (de Souza et al., 2015). The objective of the study is to evaluate the effect of CT and NT systems on some soil properties and their effect on nodulation and nodulation effectivity of groundnut, Bambara groundnut and soybean in a Paleustult in Enugu area, southeastern Nigeria.
2. Soil characterization n
Corresponding author. E-mail addresses: [email protected] (M.A.N. Anikwe) [email protected] (J.C. Eze), [email protected] (E.E. Ikenganyia). http://dx.doi.org/10.1016/j.rhisph.2016.05.001 2452-2198/& 2016 Elsevier B.V. All rights reserved.
The experiment was carried out in the 2013 and 2014 planting seasons at the Faculty Research Farm of Faculty of Agriculture,
M.A.N. Anikwe et al. / Rhizosphere 1 (2016) 14–16
Enugu State University of Science and Technology, Nigeria. The farm is located in Latitude 6° 29′N and Longitude 7° 54′E; mean elevation 450 m above sea level). The area has an annual rainfall of 1700–2010 mm. The rainfall pattern is bimodal between April and October, and the dry season is between November and March. The soil is of shale parent material classified as Typic Paleustult and has a sandy loam texture with an isohyperthermic temperature regime (Anikwe et al., 2016). The pre-planting percentage organic carbon, nitrogen and available P were 0.18%, 0.056% and 15.64 C mol kg 1 respectively. The soil pH in KCl was 5.5, CEC 8.4, Mg þ 1.20, K þ 0.06, Na þ 0.09, and Al þ 0.27 C mol kg 1. The soil dry bulk density was 1.52 Mg m 3 while total porosity and saturated hydraulic conductivity were 46.04% and 21.72 cm hr 1 respectively. A total land area of 10.7 m 9.7 m (103.8 m2) divided into 24 experimental units of 1.2 m 1.8 m (2.2 m2) with 1 m alley was marked out using randomized complete block design (RCBD) with 6 treatments and 4 replications. The experimental beds were prepared manually with traditional hoes. The experimental units comprised three legume crops grown in the area- Groundnut (cultivar ‘Nwakara’), Soybean (cultivar TGX 1448-2E from IITA Ibadan Nigeria) and Bambara Groundnut (Cultivar TVSU 1061from IITA Ibadan Nigeria) and two tillage systems, namely: CT (tilled plots on 0.30-m raised beds) and NT plots on flat beds. The treatments used were CT þgroundnut, NTþgroundnut, CT þBambara groundnut, NT þBambara groundnut, CT þSoybean, NTþ Soybean. The legumes were planted at 5 cm depth using 0.75 m 0.25 m planting distance at one seed per hole giving a plant population of 55,000 plants 1Ha. Lost stands were replaced. One weeding regime was carried out manually using small hoe at 21 DAP. Subsequently, rouging was employed to reduce weed competition in each of the seasons. Soil samples (collected from 4 points at 0.30 m depth in each plot at 60 DAP) was analysed in the laboratory. Total N was determined by the macro-Kjeldahl method (Bremner, 1982). Available P was determined using Bray II method (Olsen (1982). Soil organic carbon (SOC) was analyzed by the Walkley/Black procedure (Nelson and Sommers, 1982). Soil pH in KCl was measured by the glass electrode pH meter (McLean, 1982). The exchangeable cations and cation exchange capacity (CEC) were determined by the method described by Thomas (1982). Particle size distribution was determined by hydrometer method (Gee and Orr, 2002). Dry bulk density was determined by the core method (Grossman and Reinsch, 2002). Total porosity values were derived from bulk density data. Saturated hydraulic conductivity (Ksat) was determined by the method of Klute and Dirksen (1986). Five plants were selected at random in each plot and measured, which was averaged to give the number of nodules and effectivity of nodules per plant. In determining the number of nodules, a spade was used to carefully scoop out the soil containing the plant roots. The soil with the roots was then immersed in a basin of water to remove the soil, the roots were recovered and the nodules counted manually. To determine the nodule effectivity, each nodule was cut into two; those that the internal surface was pink in colour were counted as effectively fixing nitrogen with indigenous rhizobia. The number of nodules and nodule effectivity counts were made at 60 DAP. The data collected from the experiment was analyzed using Analysis of Variance (ANOVA) for RCBD as outlined by Steel and Torrie (1980).
3. Soil physical and chemical properties Table 1 shows significant differences in soil dry bulk density, total porosity, gravimetric water content and hydraulic conductivity between CT and NT plots. No significant treatment
15
Table 1 Effect of tillage techniques on selected soil physical properties at 60 DAP. Treatments
NTþ GN CTþ GN NTþ BG CTþ BG NTþ SB CTþ SB F-LSD(p ¼ 0.05)
Bulk density (Mg m-3)
Total porosity (%)
K-Sat (Cm hr 1)
Gravimetric water content (%)
2014
2015
2014
2015
2014
2015
2014
2015
1.53 1.42 1.52 1.40 1.66 1.50 0.10
1.54 1.40 1.54 1.40 1.60 1.44 0.11
42.26 46.42 42.64 47.17 37.36 43.42 2.10
41.89 47.17 41.89 47.12 39.62 45.67 1.89
24.25 26.68 26.42 29.10 22.25 26.67 1.80
24.00 29.40 24.00 29.40 24.54 28.54 1.25
29.25 20.32 29.78 20.85 24.84 15.91 2.30
29.78 21.62 24.28 16.9 17.25 11.28 2.15
NB: NTþ GN – No-Till þ Groundnut, CT þ GN –Conventional Till þ Groundnut NTþBG – No-Till þ Bambara Groundnut, CT þ BG –Conventional Till þ Bambara Groundnut NTþSB – No-Till þ Soya bean, CT þ SB –Conventional Till þ Soya bean
differences were found between the individual legumes in either CT and or corresponding NT plots. At 60 DAP, the soil in all the CT plots had significantly lower soil dry bulk density (1.42– 1.50 Mg m 3) than NT plots (1.53–1.65 Mg m 3). Tillage is known to enhance a suited soil environment for crop growth by reducing the compactness of the soil (Lal and Shukla, 2004). Higher soil GWC (17.25–29.79%) were found in the NT plots when compared to soil GWC of between 11.28-21.62% found in CT plots in both seasons. Tillage influenced saturated hydraulic conductivity (Ksat) at 60 DAP in both seasons, whereas the different legumes did not significantly affect Ksat (Table 1). At 60 DAP, Ksat in CT plots containing the 3 legumes was between 26.67 and 29.25 cm/hr. These values were higher (P ¼0.05) than those in the 3 corresponding NT plots (22.25–26.42 cm/hr). Tillage system can lead to reduced bulk density which has consequent effect on the soil's ability to function for water, solute movement and soil aeration (Anikwe and Ubochi, 2007). Tillage practices significantly affected SOC content, and no significant difference in SOC was found between plots planted with the different legumes (Table 2). At 60 DAP in both seasons, NT plots had 0.25–0.40% SOC content which was higher than that of CT plots (0.15–0.33%). The results show a 40% reduction in SOC content of CT plots when compared to the NT soil values. At 60 DAP, NT plots, with 0.056–0.085% total N content, had higher (P¼0.05) soil total N content than CT plots (0.044–0.076%) for both planting seasons. The NT plots, with 79–86% percent base saturation, had (P¼ 0.05) higher soil percent base saturation than CT plots (60–72%) for both planting seasons. Higher percent base saturation in the NT soils relative to CT plots imply the NT plots have more exchangeable cations which is a positive productivity indicator (Anikwe et al., 2007). Table 2 Effect of tillage techniques on selected soil chemical properties at 60 DAP. Treatments
NTþ GN CTþ GN NTþ BG CTþ BG NTþ SB CTþ SB F-LSD(p ¼ 0.05)
pH(KCl)
SOC (%)
Total N (%)
Base Sat. (%)
2014
2015
2014
2015
2014
2015
2014
2015
5.3 5.8 5.5 5.7 5.2 5.8 ns
5.3 5.7 5.2 5.5 5.4 5.6 ns
0.25 0.15 0.40 0.33 0.40 0.29 0.07
0.28 0.18 0.35 0.26 0.37 0.24 0.09
0.085 0.054 0.070 0.056 0.056 0.044 0.05
0.076 0.058 0.072 0.061 0.059 0.048 0.03
84.14 68.50 79.34 72.88 81.63 60.14 6.40
86.24 72.50 83.44 75.50 85.88 64.05 6.20
NB: NTþ GN – No-Till þ Groundnut, CT þ GN –Conventional Till þ Groundnut NTþBG – No-Till þ Bambara Groundnut, CT þ BG –Conventional Till þ Bambara Groundnut NTþSB – No-Till þ Soya bean, CT þ SB –Conventional Till þ Soya bean
16
M.A.N. Anikwe et al. / Rhizosphere 1 (2016) 14–16
Table 3 Effect of tillage techniques on plant height, leaf area index, number of root nodules and nodulation effectivity of groundnut, bambara groundnut and soya bean at 60 DAP. Treatments
NTþ GN CT þGN NTþ BG CT þBG NTþ SB CT þSB F-LSD(p ¼ 0.05)
Plant height (cm)
Leaf area index
No. nodules per plant
Nodulation effectivity (number per Plant)
2014
2015
2014
2015
2014
2015
2014
2015
44 40 48 32 52 37 1.2
49 42 54 30 58 39 2.3
63 44 76 59 37 18 6.0
70 50 79 65 43 22 8.0
207 220 203 227 111 117 16
204 230 210 248 122 140 17
108 91 113 102 73 55 10
158 110 130 98 82 60 12
NB: NTþ GN – No-Till þ Groundnut, CT þ GN –Conventional Till þ Groundnut NTþ BG – No-Till þ Bambara Groundnut, CT þ BG –Conventional Till þ Bambara Groundnut NTþ SB – No-Till þ Soya bean, CT þ SB –Conventional Till þ Soya bean.
Tillage accelerates mineralization (breakdown) of crop residue, loss of soil organic matter and major cations (Stubbs et al., 2004). The different tillage practices and legumes did not influence soil pH at 60 DAP in both seasons of the study.
4. Plant growth, nodulation and nodule effectivity Results in Table 3 show significant differences in plant height, LAI, nodulation and nodulation effectivity of individual legumes between CT and NT plots. At 60 DAP, all the legumes in CT plots with heights of 44–58 cm, were significantly taller than their corresponding NT plots by 9–33% in both seasons. Similarly, the legumes in CT plots had significantly higher LAI than their corresponding NT plots by 22–51% respectively in both seasons. Table 3 indicates that tillage practice and legume species significantly affected the total number of root nodules and the total number of effective nodules per plant. At 60 DAP, NT plots, with 111-207 root nodules, had (P ¼0.05) lower number nodules per plant than CT plots (117-248) for both planting seasons. For nodulation effectivity, at 60 DAP, NT plots, with 73-158 root nodules per plant, had (P ¼0.05) a higher number effective nodules per plant than CT plots (55-110) for both planting seasons. These results depict that NT plots provided higher moisture content, organic carbon, total nitrogen and base saturation which are positive productivity indicators. The number of root nodules was higher in the CT plots depicting that soil compaction (higher bulk density) in the NT plots negatively affected nodulation but more number of effective nodules was found in NT plots indicating that NT plots provided better rhizospheric conditions for nitrogen fixation and therefore, improved soil productivity. Roots are able to capture plant nutrients and water and interact with a range of soil micro-organisms beneficial to soil health and crop performance (Allen, 2008).
5. Conclusion Results of the study showed that the tillage techniques affected the soil physicochemical properties of the study soil and invariably
the nodulation and nodulation effectivity of the legumes studied. Lower number of root nodules was found in NT plots when compared to that in CT. However, the number of effective nodules (nodules in active symbiotic association with rhizobium bacteria) was higher in NT plots. Results of the study depict that NT plots provided higher GWC, SOC, total nitrogen and base saturation which are positive productivity indicators. The number of root nodules was higher in the CT plots depicting that soil compaction (higher bulk density) in the NT plots negatively affected nodulation but a higher number of effective nodules was found in NT plots indicating that NT plots provided better rhizospheric conditions for nitrogen fixation and therefore, improved soil productivity. Soil health/ quality influence the efficiency of plant growth promoting bacteria in the rhizosphere of plants to obtain success in improving plant growth and productivity.
References Allen, R.C., 2008. The nitrogen hypothesis and the English agricultural revolution: A biological analysis. J. Econ. Hist. 68, 182–210. Anikwe, M.A.N., Ubochi, J.N., 2007. Short-term changes in soil properties under tillage systems and their effect on sweet potato (Ipomea batatas L.) growth and yield in an Ultisol in south-eastern Nigeria. Aust. J. Soil Res. 45, 351–358. Anikwe, M.A.N., Mbah, C.N., Ezeaku, P.I., Onyia, V.N., 2007. Tillage and plastic mulch effects on soil properties and growth and yield of cocoyam (Colocasia esculenta) on an ultisol in southeastern Nigeria. Soil Tillage Res. 93 (2), 264–272. Anikwe, M.A.N., Eze, J.C., Ibudialo, A.N., 2016. Influence of lime and gypsum application on soil properties and yield of cassava (Manihot esculenta Crantz.) in a degraded Ultisol in Agbani, Enugu Southeastern Nigeria. Soil Tillage Res. 158, 32–38. Bremner, J.M., 1982. Total nitrogen. In ‘Methods of Soil Analysis. Part 2’. In: Page, A.L., Miller, R.H., Keeny, D.R. (Eds.), Agronomy Monograph No. 9, 2nd edn ASA and SSSA, Madison, WI, pp. 915–928. Carvalhais, L.C., Dennis, P.G., Fan, B., Fedoseyenko, D., Kierul, K., Becker, A., Von Wiren, N., Borri, R., 2013. Linking plant nutritional status to plant-microbe interactions. PLoS One 8, e68555. FAO 2008. An international technical workshop: Investing in sustainable crop intensification: The case for improving soil health, FAO, Rome: 22-24 July 2008. Integrated Crop Management, 6,2008. Rome. Gee, G.W., Orr, D., 2002. Particle size analysis. In ‘Methods of soil analysis. Part 4. Physical methods’. In: Dane, J.H., Topp, G.C. (Eds.), Soil Science Society of America Book Series No. 5. ASA and SSSA, Madison, WI, pp. 255–293. Grossman, R.B., Reinsch, T.G., 2002. Bulk density and linear extensibility. In ‘Methods of Soil Analysis. Part 4. Physical Methods’. In: Dane, J.H., Topp, G.C. (Eds.), Soil Science Society of America Book Series No. 5. ASA and SSSA, Madison, WI, pp. 201–228. Ibudialo, A.N., Anikwe, M.A.N., 2015. Stratification of soil physicochemical properties as affected by tillage and NPK fertilization rates under cocoyam (Colocasia esculenta) in two agro-environment of southeastern Nigeria. Elix. Agric. 88, 36230–36241. Klute, A., Dirksen, C., 1986. Hydraulic conductivity and diffusivity: Laboratory methods. Methods Soil Anal. : Part 1—Phys. Mineral. Methods, ((methodsofsoilan1)), 687–734. Lal, R., Shukla, M.K., 2004. Principles of Soil Physics. Marcel Dekker. Inc., New York, NY. McLean, E.O., 1982. Soil pH and Lime Requirement. In: Page, A.L., Miller, R.H., Keeny, D.R. (Eds.), 2nd ed. Methods of Soil Analysis. Part 2 No. 9. ASA and SSSA, Madison Wl, pp. 199–234. Meiero, R., Lopez-Garrido, J.M., Murillo, 2009. Conservation tillage: short and long-term effects on soil carbon fractions and enzymatic activities under mediterranean conditions. Soil Tillage Res. 104, 292–298. Nelson, D.W., Sommers, L.E., 1982. Total Carbon, Organic Carbon and Organic Matter. In: Page, D.R., Millers, R.H., Keeney, D.R. (Eds.), No 9. ASA and SSSA, Madison WI, pp. 539–579. Olsen, S.R., 1982. Phosphorus. In ‘Methods of Soil Analysis. Part 2’. In: Page, A.L., Miller, R. H., Keeny, D.R. (Eds.), Agronomy Monograph No. 9, 2nd edn ASA and SSSA, Madison, WI, pp. 403–430. Soane, B.D., Ball, B.C., Arvidsson, J., Basch, G., Moreno, F., Roger-Estrade, J., 2012. No-till in northern, western and south-western Europe: a review of problems and opportunities for crop production and the environment. Soil Tillage Res. 118, 66–68. de Souza, R., Ambrosini, Adriana, Passaglia, Luciane M.P., 2015. Plant growth-promoting bacteria as inoculants in agricultural soils. Genet. Mol. Biol. 38 (4), 401–419. Steel, R.G.D., Torrie, J.H., 1980, Principles and Procedures of Statistics, Second Edition, New York: McGraw-Hill Book Company, New York. Stubbs, T.L., Kennedy, A.C., Shillinger, W.F., 2004. Soil ecosystem changes during the transition to no-till cropping. J. Crop Improv. 11 (1/2).
Contents lists available at ScienceDirect
Rhizosphere journal homepage: www.elsevier.com/locate/rhisph
Soil physicochemical quality in contrasting tillage systems and its effect on nodulation and nodulation effectivity of groundnut, Bambara groundnut and soybean in a degraded Ultisol in Agbani, Enugu Southeastern Nigeria M.A.N. Anikwe n, J.C. Eze, M.C. Chima, E.E. Ikenganyia Department of Agronomy and Ecological Management, Enugu State University of Science and Technology, Enugu, Nigeria
art ic l e i nf o
a b s t r a c t
Article history: Received 29 March 2016 Received in revised form 17 May 2016 Accepted 17 May 2016 Available online 11 June 2016
Soil health is an important factor that affects the efficiency of plant growth-promoting bacteria (PGPB) in the rhizosphere. A field trial was conducted at a Farm site in Enugu Southeastern Nigeria (6° 29′N; 7° 54′ E) to evaluate the effect of conventional tillage [CT] and no tillage [NT]) on soil properties, nodulation, and nodulation effectivity of groundnut (Arachis hypogaea), Bambara groundnut (Vigna subterranean L) and Soybean (Glycine max) in a Typic Paleustult. A Randomized Complete Block Design with six treatments and four replications was used. Soil quality attributes, nodulation and nodulation effectivity of the legumes were measured at 60 DAP. Results showed relatively higher bulk density (BD), gravimetric water content (GWC), Soil organic carbon (SOC), total nitrogen (N) and lower hydraulic conductivity in NT plots when compared to CT plots. A lower number of root nodules was found in NT plots when compared to CT plots depicting that soil compaction in the NT plots negatively affected nodulation. However, a higher number of effective nodules was found in NT plots indicating that NT plots provided better rhizospheric conditions for nitrogen fixation and therefore, improved soil productivity. & 2016 Elsevier B.V. All rights reserved.
Keywords: Tillage Nodulation Rhizobacteria Ultisol
1. Soil health, plant growth promoting bacteria and rhizosphere Soil health has been defined as: “the capacity of soil to function as a living system”. Healthy soils preserve a diverse community of soil organisms that form valuable symbiotic associations with plant roots, recycle essential plant nutrients, improve soil structure with positive repercussions for soil water and nutrient holding capacity, and ultimately improve crop production (FAO, 2008). No-till farming techniques have gained great popularity over the past two decades as growers seek new ways to protect and conserve their soil and save time and money (Soane et al., 2012). Conservation tillage reduces soil disturbances, protects the soil against degradation and improves sustainability (Meiero et al., 2009; Ibudialo and Anikwe, 2015). Soil compaction is one of the major problems facing modern agriculture. Compaction affects the activity of soil organisms by decreasing the rate of decomposition of soil organic matter and subsequent release of nutrients.
Plant-microbe interactions in the rhizosphere influence plant health, productivity and soil fertility (de Souza et al., 2015). The plant growth-promoting bacteria (PGPB) belong to a beneficial and diverse group of microorganisms that can be found in the rhizosphere, on the root surface or associated with it. Several important bacterial characteristics, such as biological nitrogen fixation and phosphate solubilization can be assessed as plant growth promotion traits (Carvalhais et al., 2013). Soil health is an important factor that affects PGPB efficiency, due to several characteristics such as soil type, nutrient pool, soil moisture, microbial diversity, and soil disturbances caused by management practices (de Souza et al., 2015). The objective of the study is to evaluate the effect of CT and NT systems on some soil properties and their effect on nodulation and nodulation effectivity of groundnut, Bambara groundnut and soybean in a Paleustult in Enugu area, southeastern Nigeria.
2. Soil characterization n
Corresponding author. E-mail addresses: [email protected] (M.A.N. Anikwe) [email protected] (J.C. Eze), [email protected] (E.E. Ikenganyia). http://dx.doi.org/10.1016/j.rhisph.2016.05.001 2452-2198/& 2016 Elsevier B.V. All rights reserved.
The experiment was carried out in the 2013 and 2014 planting seasons at the Faculty Research Farm of Faculty of Agriculture,
M.A.N. Anikwe et al. / Rhizosphere 1 (2016) 14–16
Enugu State University of Science and Technology, Nigeria. The farm is located in Latitude 6° 29′N and Longitude 7° 54′E; mean elevation 450 m above sea level). The area has an annual rainfall of 1700–2010 mm. The rainfall pattern is bimodal between April and October, and the dry season is between November and March. The soil is of shale parent material classified as Typic Paleustult and has a sandy loam texture with an isohyperthermic temperature regime (Anikwe et al., 2016). The pre-planting percentage organic carbon, nitrogen and available P were 0.18%, 0.056% and 15.64 C mol kg 1 respectively. The soil pH in KCl was 5.5, CEC 8.4, Mg þ 1.20, K þ 0.06, Na þ 0.09, and Al þ 0.27 C mol kg 1. The soil dry bulk density was 1.52 Mg m 3 while total porosity and saturated hydraulic conductivity were 46.04% and 21.72 cm hr 1 respectively. A total land area of 10.7 m 9.7 m (103.8 m2) divided into 24 experimental units of 1.2 m 1.8 m (2.2 m2) with 1 m alley was marked out using randomized complete block design (RCBD) with 6 treatments and 4 replications. The experimental beds were prepared manually with traditional hoes. The experimental units comprised three legume crops grown in the area- Groundnut (cultivar ‘Nwakara’), Soybean (cultivar TGX 1448-2E from IITA Ibadan Nigeria) and Bambara Groundnut (Cultivar TVSU 1061from IITA Ibadan Nigeria) and two tillage systems, namely: CT (tilled plots on 0.30-m raised beds) and NT plots on flat beds. The treatments used were CT þgroundnut, NTþgroundnut, CT þBambara groundnut, NT þBambara groundnut, CT þSoybean, NTþ Soybean. The legumes were planted at 5 cm depth using 0.75 m 0.25 m planting distance at one seed per hole giving a plant population of 55,000 plants 1Ha. Lost stands were replaced. One weeding regime was carried out manually using small hoe at 21 DAP. Subsequently, rouging was employed to reduce weed competition in each of the seasons. Soil samples (collected from 4 points at 0.30 m depth in each plot at 60 DAP) was analysed in the laboratory. Total N was determined by the macro-Kjeldahl method (Bremner, 1982). Available P was determined using Bray II method (Olsen (1982). Soil organic carbon (SOC) was analyzed by the Walkley/Black procedure (Nelson and Sommers, 1982). Soil pH in KCl was measured by the glass electrode pH meter (McLean, 1982). The exchangeable cations and cation exchange capacity (CEC) were determined by the method described by Thomas (1982). Particle size distribution was determined by hydrometer method (Gee and Orr, 2002). Dry bulk density was determined by the core method (Grossman and Reinsch, 2002). Total porosity values were derived from bulk density data. Saturated hydraulic conductivity (Ksat) was determined by the method of Klute and Dirksen (1986). Five plants were selected at random in each plot and measured, which was averaged to give the number of nodules and effectivity of nodules per plant. In determining the number of nodules, a spade was used to carefully scoop out the soil containing the plant roots. The soil with the roots was then immersed in a basin of water to remove the soil, the roots were recovered and the nodules counted manually. To determine the nodule effectivity, each nodule was cut into two; those that the internal surface was pink in colour were counted as effectively fixing nitrogen with indigenous rhizobia. The number of nodules and nodule effectivity counts were made at 60 DAP. The data collected from the experiment was analyzed using Analysis of Variance (ANOVA) for RCBD as outlined by Steel and Torrie (1980).
3. Soil physical and chemical properties Table 1 shows significant differences in soil dry bulk density, total porosity, gravimetric water content and hydraulic conductivity between CT and NT plots. No significant treatment
15
Table 1 Effect of tillage techniques on selected soil physical properties at 60 DAP. Treatments
NTþ GN CTþ GN NTþ BG CTþ BG NTþ SB CTþ SB F-LSD(p ¼ 0.05)
Bulk density (Mg m-3)
Total porosity (%)
K-Sat (Cm hr 1)
Gravimetric water content (%)
2014
2015
2014
2015
2014
2015
2014
2015
1.53 1.42 1.52 1.40 1.66 1.50 0.10
1.54 1.40 1.54 1.40 1.60 1.44 0.11
42.26 46.42 42.64 47.17 37.36 43.42 2.10
41.89 47.17 41.89 47.12 39.62 45.67 1.89
24.25 26.68 26.42 29.10 22.25 26.67 1.80
24.00 29.40 24.00 29.40 24.54 28.54 1.25
29.25 20.32 29.78 20.85 24.84 15.91 2.30
29.78 21.62 24.28 16.9 17.25 11.28 2.15
NB: NTþ GN – No-Till þ Groundnut, CT þ GN –Conventional Till þ Groundnut NTþBG – No-Till þ Bambara Groundnut, CT þ BG –Conventional Till þ Bambara Groundnut NTþSB – No-Till þ Soya bean, CT þ SB –Conventional Till þ Soya bean
differences were found between the individual legumes in either CT and or corresponding NT plots. At 60 DAP, the soil in all the CT plots had significantly lower soil dry bulk density (1.42– 1.50 Mg m 3) than NT plots (1.53–1.65 Mg m 3). Tillage is known to enhance a suited soil environment for crop growth by reducing the compactness of the soil (Lal and Shukla, 2004). Higher soil GWC (17.25–29.79%) were found in the NT plots when compared to soil GWC of between 11.28-21.62% found in CT plots in both seasons. Tillage influenced saturated hydraulic conductivity (Ksat) at 60 DAP in both seasons, whereas the different legumes did not significantly affect Ksat (Table 1). At 60 DAP, Ksat in CT plots containing the 3 legumes was between 26.67 and 29.25 cm/hr. These values were higher (P ¼0.05) than those in the 3 corresponding NT plots (22.25–26.42 cm/hr). Tillage system can lead to reduced bulk density which has consequent effect on the soil's ability to function for water, solute movement and soil aeration (Anikwe and Ubochi, 2007). Tillage practices significantly affected SOC content, and no significant difference in SOC was found between plots planted with the different legumes (Table 2). At 60 DAP in both seasons, NT plots had 0.25–0.40% SOC content which was higher than that of CT plots (0.15–0.33%). The results show a 40% reduction in SOC content of CT plots when compared to the NT soil values. At 60 DAP, NT plots, with 0.056–0.085% total N content, had higher (P¼0.05) soil total N content than CT plots (0.044–0.076%) for both planting seasons. The NT plots, with 79–86% percent base saturation, had (P¼ 0.05) higher soil percent base saturation than CT plots (60–72%) for both planting seasons. Higher percent base saturation in the NT soils relative to CT plots imply the NT plots have more exchangeable cations which is a positive productivity indicator (Anikwe et al., 2007). Table 2 Effect of tillage techniques on selected soil chemical properties at 60 DAP. Treatments
NTþ GN CTþ GN NTþ BG CTþ BG NTþ SB CTþ SB F-LSD(p ¼ 0.05)
pH(KCl)
SOC (%)
Total N (%)
Base Sat. (%)
2014
2015
2014
2015
2014
2015
2014
2015
5.3 5.8 5.5 5.7 5.2 5.8 ns
5.3 5.7 5.2 5.5 5.4 5.6 ns
0.25 0.15 0.40 0.33 0.40 0.29 0.07
0.28 0.18 0.35 0.26 0.37 0.24 0.09
0.085 0.054 0.070 0.056 0.056 0.044 0.05
0.076 0.058 0.072 0.061 0.059 0.048 0.03
84.14 68.50 79.34 72.88 81.63 60.14 6.40
86.24 72.50 83.44 75.50 85.88 64.05 6.20
NB: NTþ GN – No-Till þ Groundnut, CT þ GN –Conventional Till þ Groundnut NTþBG – No-Till þ Bambara Groundnut, CT þ BG –Conventional Till þ Bambara Groundnut NTþSB – No-Till þ Soya bean, CT þ SB –Conventional Till þ Soya bean
16
M.A.N. Anikwe et al. / Rhizosphere 1 (2016) 14–16
Table 3 Effect of tillage techniques on plant height, leaf area index, number of root nodules and nodulation effectivity of groundnut, bambara groundnut and soya bean at 60 DAP. Treatments
NTþ GN CT þGN NTþ BG CT þBG NTþ SB CT þSB F-LSD(p ¼ 0.05)
Plant height (cm)
Leaf area index
No. nodules per plant
Nodulation effectivity (number per Plant)
2014
2015
2014
2015
2014
2015
2014
2015
44 40 48 32 52 37 1.2
49 42 54 30 58 39 2.3
63 44 76 59 37 18 6.0
70 50 79 65 43 22 8.0
207 220 203 227 111 117 16
204 230 210 248 122 140 17
108 91 113 102 73 55 10
158 110 130 98 82 60 12
NB: NTþ GN – No-Till þ Groundnut, CT þ GN –Conventional Till þ Groundnut NTþ BG – No-Till þ Bambara Groundnut, CT þ BG –Conventional Till þ Bambara Groundnut NTþ SB – No-Till þ Soya bean, CT þ SB –Conventional Till þ Soya bean.
Tillage accelerates mineralization (breakdown) of crop residue, loss of soil organic matter and major cations (Stubbs et al., 2004). The different tillage practices and legumes did not influence soil pH at 60 DAP in both seasons of the study.
4. Plant growth, nodulation and nodule effectivity Results in Table 3 show significant differences in plant height, LAI, nodulation and nodulation effectivity of individual legumes between CT and NT plots. At 60 DAP, all the legumes in CT plots with heights of 44–58 cm, were significantly taller than their corresponding NT plots by 9–33% in both seasons. Similarly, the legumes in CT plots had significantly higher LAI than their corresponding NT plots by 22–51% respectively in both seasons. Table 3 indicates that tillage practice and legume species significantly affected the total number of root nodules and the total number of effective nodules per plant. At 60 DAP, NT plots, with 111-207 root nodules, had (P ¼0.05) lower number nodules per plant than CT plots (117-248) for both planting seasons. For nodulation effectivity, at 60 DAP, NT plots, with 73-158 root nodules per plant, had (P ¼0.05) a higher number effective nodules per plant than CT plots (55-110) for both planting seasons. These results depict that NT plots provided higher moisture content, organic carbon, total nitrogen and base saturation which are positive productivity indicators. The number of root nodules was higher in the CT plots depicting that soil compaction (higher bulk density) in the NT plots negatively affected nodulation but more number of effective nodules was found in NT plots indicating that NT plots provided better rhizospheric conditions for nitrogen fixation and therefore, improved soil productivity. Roots are able to capture plant nutrients and water and interact with a range of soil micro-organisms beneficial to soil health and crop performance (Allen, 2008).
5. Conclusion Results of the study showed that the tillage techniques affected the soil physicochemical properties of the study soil and invariably
the nodulation and nodulation effectivity of the legumes studied. Lower number of root nodules was found in NT plots when compared to that in CT. However, the number of effective nodules (nodules in active symbiotic association with rhizobium bacteria) was higher in NT plots. Results of the study depict that NT plots provided higher GWC, SOC, total nitrogen and base saturation which are positive productivity indicators. The number of root nodules was higher in the CT plots depicting that soil compaction (higher bulk density) in the NT plots negatively affected nodulation but a higher number of effective nodules was found in NT plots indicating that NT plots provided better rhizospheric conditions for nitrogen fixation and therefore, improved soil productivity. Soil health/ quality influence the efficiency of plant growth promoting bacteria in the rhizosphere of plants to obtain success in improving plant growth and productivity.
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