Effects of tillage and crop rotation on chemical phosphorus forms and some related biological activities in a Chilean Ultisol

Abstract

The effect of tillage systems and crop rotation on microbial biomass phosphorus (MBP) and acid phosphatase (P‐ase) activity, and the amount of different phosphorus (P) forms measured by 31P‐NMR spectroscopy were studied on a field experiment carried out in a temperate Ultisol from southern Chile. Two tillage systems, no tillage (NT) and conventional tillage (CT) and two crop rotations, oat–wheat (OW) and lupine–wheat (LW) were evaluated 4 yr after the start of the experiment to determine the effects of such management on some soil biological parameters and P forms at three depths (0–5, 0–10 and 10–20 cm). Microbial biomass P ranged from 6.5 to 22.6 mg/kg, whereas the mean total P (PT) was 1995 mg/kg for all treatments (OW and LW). Microbial biomass carbon (MBC) and surface P accumulation (at 0–5 cm depth), including Olsen P, MBP, orthophosphate monoesters (monoester‐P), were larger under NT than CT. Tillage effects were greater than crop rotation effects in enhancing P availability. The LW rotation showed enhanced P‐ase activity and increased monoester‐P forms (57 vs. 30% of the total integral area of the spectra, in average) compared with OW. Nevertheless, OW rotation increased orthophosphate (ortho‐P), especially at 10–20 cm. Microbial biomass carbon ranged from 532 to 2351 mg/kg, which represented 1.2–4.5% of total organic C (Co). Furthermore, MBP correlated positively with MBC (r = 0.80), Olsen P (r = 0.77), Co (r = 0.77), pH (r = 0.65), PT (r = 0.65) and P‐ase activity (r = 0.57), suggesting the importance of the microbial biomass on soil P availability.

Solution Phosphorus-31 Nuclear Magnetic Resonance Spectroscopy of Soils from 2005 to 2013: A Review of Sample Preparation and Experimental Parameters

“…A number of researchers also have treated their samples in various ways to remove paramagnetic ions. The most common method was with Chelex-100 (Colpo Gatiboni et al, 2005;Briceño et al, 2006;Turner, 2008;Redel et al, 2011;Turrion et al, 2010). Turner (2008) reported that Chelex treatment removed various P forms compared with NaOH-EDTA alone, as was also reported by Cade-Menun et al (2002).…”

“…Turner et al (2012) used bromination before NaOH-EDTA extraction to destroy all P forms except inositol phosphates. Other pretreatments in use are HCl (Briceño et al, 2006;Redel et al, 2011) and water and/or NaHCO 3 as part of a sequential fractionation (Turner et al, 2006b;He et al, 2008). Using 31 P NMR, He et al (2008) showed that the P in the NaHCO 3 extracts was 93 to 100% orthophosphate, as were the low concentrations of P in water used before NaHCO 3 in that study.…”

“…Since 2005, the majority of studies have used NaOHethylenediaminetetraacetic acid (EDTA) (0.25 mol L −1 NaOH plus 0.05 mol L −1 Na 2 EDTA) to extract P for 31 P NMR (Tables 3 and 4). There are only a handful of exceptions: 0.1 mol L −1 NaOH plus 0.4 mol L −1 NaF (Lehmann et al, 2005;Rückamp et al, 2010;Kovalev and Kovaleva, 2011);water (McDowell and Stewart, 2005); water followed by 0.4 mol L −1 NaOH (Shafqat et al, 2009); 0.5 mol L −1 NaOH after sequential fractionation with 0.5 mol L −1 NaHCO 3 and 1.0 mol L −1 HCl, using only the NaOH fraction for 31 P NMR (Turner et al, 2006b); NaOH-EDTA after water and 0.5 mol L −1 NaHCO 3 , analyzing all fractions by 31 P NMR (He et al, 2008); and HCl followed by NaOH and then the cation exchange resin Chelex (Briceño et al, 2006;Redel et al, 2011). Only Briceño et al (2006) compared their extraction technique directly to NaOH-EDTA; however, it must be noted that samples in their study were extracted with NaOH-EDTA only once but were extracted three times with NaOH.…”

“…The majority of studies used air-dried soils (e.g., Lehmann et al, 2005;Smith et al, 2006;Cade-Menun et al, 2010;Soinne et al, 2011;Turner and Blackwell, 2013). A few studies used soils that were oven dried at various temperatures (e.g., Turner 2006;Bol et al, 2006), while others extracted fieldmoist soils (Briceño et al, 2006;Turner, 2008;Hill and CadeMenun, 2009;Doolette et al, 2010Doolette et al, , 2011bRedel et al, 2011). Wetland soils were extracted field moist (Sundareshwar et al, 2009) or after oven drying at various temperatures (El-Rifai et al, 2008;Cheesman et al, 2010b;Hamdan et al, 2012), air drying , or after freezing and freeze-drying (Turner et al, 2006a).…”

Effect of Tillage and Phosphorus Fertilization of Wheat on Inorganic Soil Phosphorus Fractions under Wheat-Sorghum Cropping System

“…of the soil microbial community and enzymes, which in turn affects the concentration and composition of soil P (Redel et al, 2011).…”