Impact of long-term wheat production management practices on soil acidity, phosphorus and some micronutrients in a semi-arid Plinthosol

Abstract

Farmers continuously remove crop residues for use as building materials, fuel and animal feed or bedding as well as to avoid difficulties during tillage operations. Therefore, demonstrations of the benefits of recycling crop residues are necessary. The aim with this study was to evaluate the influence of different wheat production management practices on acidity and some essential nutrients from a long-term trial on a Plinthosol in semi-arid South Africa. The trial was set up in 1979, and since then two methods of straw management (unburned and burned), three methods of tillage (no-tillage, stubble mulch, and plough), two methods of weed control (chemical and mechanical), and three levels of nitrogen (N) fertiliser (20, 40 and 60 kg ha–1) have been applied. Soil samples were collected in June 2010 at depths of 0–50, 50–100, 100–150, 150–250, 250–350 and 350–450 mm from plots that received 40 kg N ha–1 and were analysed for pH, phosphorus (P), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn). Results obtained showed that straw burning resulted in higher P and Mn but lower Cu than no-burning. No-tillage, and to some extent stubble mulch, suppressed soil acidification and increased P and Zn compared with ploughing, especially in the surface layers where crop residues accumulate. In contrast, mouldboard ploughing and stubble mulch increased Cu more than no-tillage, possibly due to the strong affinity of organic matter for Cu. Tillage effects on Mn were inconsistent and difficult to explain. Chemical weeding also improved P, probably because of the pesticide application, but resulted in lower pH and Cu values compared with mechanical weeding. Treatment combinations also had an influence on P and, to a lesser extent, on soil pH and Cu, which might be due to the higher organic matter present in no-tilled soils. Irrespective of straw management or weed-control methods, no-tillage resulted in higher P than did ploughing and stubble mulch. Nutrient concentrations and pH values were sufficient for wheat growth under all treatments. However, although the nutrients were highest under straw burning, no-tillage and, to some extent, stubble mulch, wheat yield was higher with unburned straw and mouldboard ploughing. Therefore, an integrated approach from various disciplines is recommended to identify and rectify yield-limiting factors under conservation tillage systems.

Availability and uptake of trace elements in a forage rotation under conservation and plough tillage

“…The tillage system has only a reduced effect on soil available Mn, with most part of significant differences being favourable to CT. Our results were partially consistent with those of some authors that reported either no differences due to tillage (de Santiago et al, 2008;Loke et al, 2013; or higher Mn availability under CT (Houx et al, 2011;Lavado et al, 1999), but contrast with other showing the opposite tendency (Edwards et al, 1992;Franzluebbers and Hons, 1996;López-Fando and Pardo, 2009;Martín-Rueda et al, 2007). Unlike the other studied trace elements, the concentration of available Mn was stratified both under MT and (to a lesser extend) CT as also found Franzluebbers and Hons (1996) and Wright et al (2007).…”

“…Singularly, Zn concentrations were never higher in CT than in MT, as also found most researchers (de Santiago et al, 2008;Edwards et al, 1992;Franzluebbers and Hons, 1996;Houx et al, 2011;Loke et al, 2013;Martín-Rueda et al, 2007;Wright et al, 2007). Agreeing with Franzluebbers and Hons (1996) and Wright et al (2007), extractable Zn was greater near the soil surface and decreased with depth in both MT and CT, leading to a stratification related with (but greater than) that observed for organic C (r=0.482, P< 0.01; n=212).…”

“…However, until present time, published studies on the effect of tillage on trace elements in soils and crops are scarce (Lavado et al, 2001;López-Fando and Pardo, 2009;Stanislawska-Glubiak and Korzeniowska, 2011;, and the few available reports showed contradictory results probably due to the interaction with soil type, crop species and fertiliser practices (Watson et al, 2012). While Westermann and Sojka (1996) did not find differences in soil trace concentration among tillage systems, other studies reported higher levels of Mn and Zn under conservation tillage than under ploughing tillage (Edwards et al, 1992;Franzluebbers and Hons, 1996;Loke et al, 2013;López-Fando and Pardo, 2009;Martín-Rueda et al, 2007;Rhoton, 2000) and the opposite tendency for Fe (López-Fando and Pardo, 2009;Rhoton, 2000) and Cu (Loke et al, 2013;Rhoton, 2000). Although tillage practice can modify trace element concentrations in crops (StanislawskaGlubiak and Korzeniowska, 2009), no differences on Mn, Cu and Zn concentration have also been reported for barley straw (Martín-Rueda et al, 2007), sorghum (de Santiago et al, 2008) and flax (Grant et al, 2010).…”

“…While some researchers found higher Fe availability under conservation tillage than under conventional tillage (Franzluebbers and Hons, 1996;Houx et al, 2011;Martin-Rueda et al, 2007), other authors observed the opposite tendency (Lavado et al, 1999;Rhoton, 2000) or no differences due to tillage (de Santiago et al, 2008;Loke et al, 2013). Like those of the former authors, our results showed that the available Fe levels were slightly affected by the tillage system, the effect being depth dependent as previously reported Martín-Rueda et al (2007), with no difference in the 0-5 cm layer and higher values under CT than under MT in the other soil layers.…”

Nutrient concentration and yield of maize (Zea maysL.) after vetch (Vicia sativaL.) in conventional and reduced tillage systems

“…However, published studies on the effect of tillage on nutrients in plants are scarce (Lavado et al, 2001, Stanislawska-Clubiak andKorzeniowska, 2009), and the few available reports showed interactions between soil and plant (Houx et al, 2011;García-Marco et al, 2014). Some authors did not find differences in micronutrient concentrations between tillage systems (Westermann and Sojka, 1996), others reported higher concentration of manganeze and zinc in reduced tillage than plough tillage -Rueda et al, 2007;Loke et al, 2013), and the opposite tendency for iron and copper (Loke et al, 2013). These contrasting results could be related to soil and plant characteristics, but also to meteorological conditions during the growing season.…”