Effect of mulch and tillage system on soil porosity under wheat (Triticum aestivum)

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Abstract

Crop residues and reduced tillage become current tendency in modifying tillage due to better water management, organic and nutrient supply and increasing crop production. This study was carried out to quantify the effect of fodder radish mulching and different tillage systems in wheat production. In 2004–2006 the field trial was set up on Luvic Chernozems derived from loess. This experiment consisted of two factors: tillage system (conventional or reduced) and mulch (with or without). The air–water properties of soil with particular focus on macropore characteristics were investigated.

The tillage system and mulch application significantly influenced physical properties of investigated soil. Reduced tillage, without mouldboard plough, increased the soil density with respect to conventional tillage. However, in the upper soil layer (0–10 cm) with mulch residues the bulk density decreased and reached the similar value as those obtained at conventional tillage (1.25 g cm−3). The macroporosity of soil with conventional tillage (14.79%) was significantly higher in comparison with reduced tillage (6.55%). The mulch of fodder radish added at reduced tillage increased the macroporosity in pore diameter range of 50–500 μm. These changes referred to all shape classes: regular, irregular and elongated pores. The lowest transmission pores content (0.078 cm3 cm−3) was noticed at the reduced tillage without mulch at the 0–10 cm layer. Due to lack of differences in storage pores the tillage and mulching had no effect on both AWC (available water content) and PWC (productive water content) values. The higher value of AWC was noticed in the upper soil layer (0.198 cm3 cm−3 in average), whereas in the 10–20 cm soil layer it was 0.186 cm3 cm−3. Similar relation was recorded in PWC values, 0.165 and 0.154 cm3 cm−3, respectively. The results obtained in physical properties of soil reflected in wheat yields. The yields obtained at reduced tillage system without mulch (5.54 t ha−1) were significant lower with respect to treatment when mulch applied (6.79 t ha−1). The mulch residues did not affect yields at conventional tillage (6.53 t ha−1 without mulch and 7.00 t ha−1 with mulch). The main conclusion is that the mulching can help to avoid yield reduction in wheat production when reduced tillage is used.

Introduction

Mulching, when catch crop residues are spread and left on the soil surface between successive crops, is well-known and recommended practice for conserving soil and water (Becher, 2005, Lal and Stewart, 1995, Lamarca, 1996, Pabin et al., 2004). The main advantages of mulching are organic matter and nutrient supply. The slow release of nitrogen (N) from decomposing mulch residues is better synchronized with plant uptake than sources of inorganic N, increase N-uptake efficiency and crop yield while reducing N leaching losses (Cherr et al., 2006, Aulakh et al., 2000, Cline and Silvernail, 2001). Mulched catch crops approach also long-term increases of soil organic matter and microbial biomass (Goyal et al., 1999, Chander et al., 1997, Biederbeck et al., 1998), further improving nutrient retention and N-uptake efficiency. These favourable changes are the main reason for increase in plant yields (Lal, 1995, Unger, 1986, Wicks et al., 1994).

The other profits are favourable changes in microclimate within fields and reduction soil temperature variations (Stiger, 1984, Sharratt, 2002). Plant residues protect the soil surface against the splash effect of raindrops and crusting (Sumner and Stewart, 1992) and increases aggregate stability measured by wet-sieving (Gerzabek et al., 1995). It was confirmed by Le Bissonnais and Arrouays (1997) who stated that increasing the soil organic matter content increased its stability and decreased soil surface sealing. Martens and Frankenberger (1992) showed that organic matter addition increased macroporosity and water infiltration rates. Much research has shown that use of surface mulch can result in storing more precipitation water in soil by reducing runoff, increasing infiltration and decreasing evaporation (Ji and Unger, 2001, Smika and Unger, 1986). Cover crops can provide biological weed control by replacing an unmanageable weed population with a manageable cover crop species (Teasdale, 1996). Mulched cover crops also may provide favourable microhabitats for beneficial insects (Orr et al., 1997, Reader, 1991). Application of plant mulch combined with minimum tillage is known to be effective in reducing soil erosion, maintaining soil structure and conserving soil water in temperate as well as tropical regions (Unger, 1994, Thurston et al., 1994).

Legume species, as catch crops, are often preferable to nonlegumes because they supply their own N. However, nowadays in production systems where N is less limiting, a specific catch crop service other than high N supply (such as allelopathy) is considered, or where legumes do not perform well, nonlegumes or mixtures of legumes and nonlegumes are more advantageous (Cherr et al., 2006). One of nonlegumes widely used as a catch crop is fodder radish. Brassicaceae species plays important role in limit of N leaching losses in the 0–90 cm soil depth. They also increase C organic content (Martinez and Guiraud, 1990, Richards et al., 1996).

The aim of this study was to evaluate the effects of fodder radish, cultivated as a catch crop, residues in different tillage system (conventional and reduced) on air–water properties of soil. The main reason to use the reduced tillage with spring mulch incorporation (versus traditional fall plough tillage) was to protect the soil against erosion and physical degradation what is particularly important on soils derived from loess. In this experiment it was hypothesis that mulch may play favourable role in soil structure. The objective of the study was to evaluate morphometric characterization of soil pores in wide range of diameter from 0.005 to >2000 μm with special focus on macropores investigated by image analysis on soil sections. The field trial with mulch applied in two tillage systems, conventional and reduced, was established in 2004–2006 on silt loam Luvic Chernozems in South of Poland, Central Europe.

Section snippets

Experimental design

The field experiment was set up in Prusy near Krakow, Poland (N 50°07′10″; E 20°05′04″, elevation 271 m above see level) in 2004–2006. The experiment was laid out in split plot design replicated four times with a plot area of 11.2 m2 (1.4/8.0 m). Main plots were assigned to different tillage treatments and subplots to mulch application treatments. Tillage treatments consisted of (i) conventional tillage and (ii) reduced soil tillage. The following mulch and tillage treatments were assigned:

Dry bulk density and total porosity

The mean bulk density of investigated soil was 1.27 g cm−3 in the 0–10 cm and 1.31 g cm−3 in the 10–20 cm soil layer (Table 3). The values of total porosity were 0.50 and 0.48 cm3 cm−3, respectively. We expect that reduced tillage without mouldboard plough increase the soil density what is widely reported particularly in no-tillage systems (Singh and Malhi, 2006, Pidgeon and Soane, 1977, Van Ouwerkerk and Boone, 1970). This relation was confirmed in the 10–20 cm soil layer. However, in the upper, 0–10 

Conclusions

The present study showed that fodder radish crop left on the soil surface as mulch improved soil porosity. These favourable changes were noticed only in pores ranged in their diameter from 50 to 500 μm. The differences in macroporosity and some physical properties of soil were significant only when reduced tillage was applied. In technology with rotary tiller instead mouldboard plough soil was characterized by higher bulk density and lower macropores volume. Mulching increase participation of

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