Elsevier

Soil and Tillage Research

Volume 89, Issue 2, September 2006, Pages 210-220
Soil and Tillage Research

Soil porosity and water infiltration as influenced by tillage methods

https://doi.org/10.1016/j.still.2005.07.012Get rights and content

Abstract

The relations between soil pore structure induced by tillage and infiltration play an important role in flow characteristics of water and solutes in soil. In this study, we assessed the effect of long-term use of various tillage systems on pore size distribution, areal porosity, stained (flow-active) porosity and infiltration of silt loam Eutric Fluvisol. Tillage treatments were: (1) ploughing to the depth of 20 cm (conventional tillage (CT)); (2) ploughing to 20 cm every 6 years and to 5 cm in the remaining years (S/CT); (3) harrowing to 5 cm each year (S); (4) sowing to the uncultivated soil (no tillage (NT)), all in a micro-plot experiment. Equivalent pore size distribution was derived from the water retention curve, areal porosity – from resin-impregnated blocks (8 cm × 9 cm × 4 cm) and stained porosity – from horizontal sections (every 2 cm) of column samples (diameter: 21.5 cm, height: 20 cm) taken after infiltration of methylene blue solution. The pore size distribution curves indicated that the textural peaks of the pore throat radius of approximately 1 μm were mostly defined under NT, whereas those in the structural domain of radii of 110 μm radius—under CT. The differences among the tillage treatments were more pronounced at depth 0–10 cm than 10–20 cm. At both depths, the differences in pore size distribution between the tillage treatments were relatively greater in structural than those in the matrix domain. CT soil had the greatest areal porosity and stained porosity. The stained porosity as a function of depth could be well described by logarithmic equations in all treatments. Cumulative infiltration (steady state) as measured by the double ring infiltrometer method was the highest under CT (94.5 cm) and it was reduced by 62, 36 and 61% in S/CT, S and NT soil, respectively. Irrespective of tillage method, cumulative infiltration rates throughout 3 h most closely correlated with stained porosity in top layers (0–6 cm). Overall, the results indicate that soil pore system under CT with higher contribution of large flow-active pores compared to reduced and no tillage treatments enhanced infiltration and water storage capacity.

Introduction

Measurements of pore characteristics are becoming more and more used to characterize soil structure since they influence numerous functions in soils. One important function of soil is transmission of water, which directly affects plant productivity and the environment. Infiltration of water increases water storage for plants and groundwater recharge and reduces erosion. The rate of infiltration is controlled by the pore size distribution and the continuity of pores or pathways (Kutílek, 2004). The role of macro-pores in rapid infiltration under ponded conditions (preferential flow) was stressed in numerous papers (Ehlers, 1975, Lin et al., 1996, Arvidsson, 1997, Guérif et al., 2001). Lin et al. (1996) reported that 10% of macro-pores (>0.5 mm) and meso-pores (0.06–0.5 mm) contributed about 89% of the total water flux. As shown by Ehlers (1975), the maximum infiltrability of conducting channels in untilled soil was more than 1 mm/min, although the volume of these channels amounted to only 0.2 vol.%. The preferential flow has also been observed in an unsaturated soil under non-ponded conditions (Deeks et al., 1999). Therefore, this flow has been increasingly recognised as a major component of water movement in many soils, particularly clays (Armstrong et al., 1999). Incorporating the preferential flow component into models that assume a horizontally homogeneous soil profile improves their performance in predicting water distribution and chemical movement in soil profile (Walczak et al., 1996, Borah and Kalita, 1999, Kumar et al., 1999, Ludwig et al., 1999).

In addition, a soil matrix with macro-pores will offer greater potential for undisturbed root growth because the roots can bypass the zones of high mechanical impedance (Gliński and Lipiec, 1990, Lipiec and Hatano, 2003). The structure and functions of macro-pores can be an effective measure of soil ‘quality’ as they are relatively resistant to vertical compression (Alakukku, 1996). Lin et al. (1999) proposed to incorporate macro-porosity as a criterion of soil structure in the soil morphological system.

Tillage largely influences pore size distribution. Soils under conventional tillage (CT) generally have lower bulk density and associated higher total porosity within the plough layer than under no tillage (NT). The changes in total porosity are related with alterations in pore size distribution. This relation can be different depending on soil type. Schjønning and Rasmussen (2000) reported that under the same site conditions, NT compared to CT resulted in lower volume of macro-pores (>30 μm) on sandy soil and silty loam, whereas the opposite effect was found on sandy loam. Kay and VandenBygaart (2002) reported in their review that converting from CT to NT generally results in an increased volume fraction of pores 100–500 μm and a decreased volume of pores 30–100 μm.

The effect of soil tillage and management on transmission properties is not uniform. The results showed that untilled compared to tilled soil had greater (Freebarin et al., 1986, Arshad et al., 1999, McGarry et al., 2000), similar (Ankeny et al., 1990) or lower infiltration rates (Gantzer and Blake, 1978, Gómez et al., 1999, Rasmussen, 1999). The inconsistencies can be associated with pore functioning. In NT soils, greater infiltration was attributed to greater contribution of flow-active macro-pores made by soil fauna or by roots of preceding crops (Tebrügge and Düring, 1999), whereas in tilled soils with stable structure—to preferential flow through interaggregate pores (Lin et al., 1999). However, the flow-active pores are not frequently quantified combined with infiltration due to the time-consuming measurements.

Understanding the relations between pore structure induced by tillage and infiltration is of crucial importance in predicting flow characteristics of water and solutes in the soil profile. In this study, we assessed the effect of long-term use of various tillage systems on pore size distribution, areal porosity, stained (flow-active) porosity and infiltration of silt loam Eutric Fluvisol.

Section snippets

Soil type and tillage experiment

The experiment was conducted on Eutric Fluvisol by the FAO legend at the experimental field of the Institute of Soil Science and Plant Cultivation in Puławy (51.25°N, 21.58°E), Poland. The soil has 25% clay (<2 μm), 62% silt (2–50 μm) and 13% sand (50–2000 μm) at the depth 0–30 cm. Long-term annual mean temperature and precipitations in the site are 7.7 °C and 588 mm, respectively.

The experimental design used randomised block with four replicates of micro-plots (1 m × 1.5 m). The treatments were as

Pore size distribution

The derivative presentation of pore size distribution curve (Fig. 1) indicates that the porous system of the studied soil is organized hierarchically with matrix (textural) domain and secondary (structural) domain consisting of two sub-domains. The domains can be separated by the minimum pressure head and the corresponding equivalent pore radii on the pore distribution curve (Kutίlek et al., 2006). The minima between matrix and structural domains in our study are similar among the tillage

Conclusion

Long-term application of various tillage methods (conventional tillage, reduced tillage and no tillage) on silt loam Eutric Fluvisol produced markedly different pore size distribution, areal and stained (flow-active) porosity. As shown by continuous pore size distribution curve, the peaks in matrix domain were most displayed under NT and those in structural domain—under CT. The differences in pore size distribution between the tillage treatments were relatively greater in structural than those

Acknowledgement

This work was funded in part by the Polish State Committee for Scientific Research (Grant No. 3 P06R 001 23).

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