Arboriculture & Urban Forestry 37(6): November 2011 271 mined with the Bray P-1 extraction and analyzed colorimetri- cally at 882 nm on a spectrophotometer (Model UV mini 1240, Shidmadzu, Inc., Kyoto, Japan) (Olsen and Sommers 1982). Soil pH and electrical conductivity in µs cm-1 were measured in 1:1 (soil:deionized) water pastes (Model Orion 5-Star, Thermo Fisher Scientific, Inc., Waltham, Massachusetts, U.S.). Total soil C and N were determined by automated dry combustion on a CN ana- lyzer (Vario ELIII, Elementar Analysensysteme, Hanau, Germa- ny) (Nelson and Sommers 1996). The soil fumigation-extraction method (Brookes et al. 1985) was used to determine microbial biomass N (MBN) in mg kg-1 with ethanol-free chloroform for five days, extracted with 0.5 M K2 ler 1996). Potential N mineralization was measured as the net increase or decrease in available NH4 colorimetrically, as described (Sims et al. 1995). Carbon dioxide incubation. Nitrate in the 0.5 M K2SO4 NH4 using a Devarda’s alloy and 0.1 M H2 + extract was reduced to SO4 - over the 10 day and then read evolution was measured over a 24-hour period using Solvita CO2 respiration paddles and a digital color reader (Haney et al. 2008). Laboratory Assay II The second laboratory assay was a full-factorial experiment with the same two soil types, three treatments, and six replicates. The three treatments were: water, NPK fertilizer (30:10:7) at 195 kg N ha-1 the treatments the field-collected soils were dried and passed through a two-millimeter sieve. Sixty grams of each soil were weighed into 100 mL volumetric flasks. Liquid treatments (60 mL) were added to the soils bringing them to 100% water-filled pore space. The headspace of each volumetric flask was purged with helium and immediately capped with rubber septa to allow for gas headspace sampling. Sufficient acetylene was then add- ed to bring the headspace to a 10/90 acetylene/helium mix. The and ACTc soils were incubated in the dark at 25°C for a total of eight days. Gas sampling for denitrification followed the acetylene inhibi- tion method (Yoshinari and Knowles 1976; Drury et al. 2008). Gas samples were collected from each flask at 12, 24, 48, 96, and 192 hours. Prior to sample injection, 9 mL of 10% acetylene and 90% helium were added to10 mL vacuum vials. A 1000 µL sample was collected from the flask and added to the vacuum vial. A 1000 µL mixture of 10% acetylene and 90% helium was added to the flasks to replace the gas removed. A 500 µL subsample was extracted from the vacuum vials and concentrations of N2 termined using a thermal conductivity gas chromatograph (Hewlett Packard 5710A with Alltech Porapak Q 50/80 in series with Alltech Haysep Q 80/100 column, Agilent Technologies, Foster City, Cali- fornia, U.S.). The carrier gas used was helium, flow rate was 15 cm3 min-1 O and CO2 and N2 , and detector temperature 100°C. Peak retention times for CO2 O were 8 to 9 minutes and 11 to 12 minutes. Standards 3% Pennsylvania, U.S.) and 100 mg N2O kg-1 lyzed Gas, Micro MAT10, 100 mg kg-1 N2 CO2 (Scotty II Analyzed Gas, CO2 , 3%, PN 24035, Plumsteadville, (Matheson Tri-Gas Ana- 0, Item # GMT10346TK, Oak Creek, Wisconsin, U.S.) were tested daily with samples. ©2011 International Society of Arboriculture were de- at 224 kL ACT ha-1 . Prior to adding (Model ELx 800, Biotek Instruments, Inc., Winooski, Vermont, U.S.) (Sims et al. 1995). Microbial biomass N was the difference in N between the fumigated and unfumigated samples, using an extraction efficiency factor of k fate and Devarda’s alloy for NH4 SO4 EN = 0.54 (Joergensen and Muel- + and NO3 , and total extractable N was reduced to NH4 . Soil sub-samples were fumigated + with persul- + absorbance readings at 650 nm Table 1. Chemical and biological properties of A horizon silt loam, Bt horizon clay loam, deionized water control, dilute aerated compost tea (ACTd aerated compost tea (ACTc Parameter A horizon soil Bt horizon soil water treatment ACTd ACTc treatment treatment fertilizer treatment pH Ca2+ 6.20 (0.2) 8.01 (0.3) (1:1) (mg kg-1) (mg kg-1) (mg kg-1) (mg kg-1) (mg kg-1 4.91 1230 (32) 571 (8) 120 (4) 45.3 (6) 1922 (18) 7.52 (0.4) 7.57 (0.1) 4.88 (0.0) 4.91 (0.1) 1153 (13) 1886 (38) 1893 (9) 1401 (276) 319 (5) 225 (9) 509 (9) 534 (3) 528 (10) 200 (1) 126 (22) 154 (9) 164 (3) 117 (6) 48.8 (2) 48.1 (2) 48.8 (3) 42.2 (5) 42.2 (10) (1.0) 1.62 (1.1) (0.4) 2.21 (2.1) 4.83 (2.1) 4.82 (2.2) ), and 30-10-7 synthetic fertilizer treatment. Means with (SE) listed below are from three replicates. C N C/N NH4 2.58 0.261 10.3 Mg2+ K+ Na+ P ) (%) (%) (0.3) (0.03) (0) 1.87 0.073 26.8 (0.1) (0.01) (1) 0.601 0.50 0.001 512 (0.2) (0.01) (11) 5.14 0.903 5.91 (0.7) (0.20) (0.6) 10.3 (0) 84.1 8.16 (1) (1) organic N (DON), microbial biomass N (MBN), Solvita test respiration (RES), and potential N mineralization (PMN). (0.1) 36.4 29.7 (1) 1.22 (0.1) + 3.12 (0.8) 0.502 (0.61) (ratio) (mg kg-1) (mg kg-1) (mg kg-1) (mg kg-1) (mg kg-1 d-1) (mg kg-1 d-1 0.240 NO3 8.62 (0.7) 0.803 (0.41) 1.21 (0.1) 5.32 (0.1) 7.20 (0.2) 4.91 (1.1) 0.501 (0.01) 0.911 (0.31) 8.32 (0.2) 4.10 (0.2) 2.81 (0.2) 1.22 (0.4) 1.21 (0.0) 1.62 (0.7) 5.21 (0.1) 4.53 (0.9) 47.8 (3) 20.7 (5) 0.002 (0.03) 13.2 (1) 132 (4) 148 (45) 41.1 (1) 10.5 (2) 0.103 (0.01) 0.101 (0.04) 5.31 (1.1) 9.52 (4.2) Abbreviations: aerated compost tea (ACT), calcium (Ca), magnesium (Mg), potassium (K), sodium (Na), Bray P1 phosphorus (P), organic carbon (C), total nitrogen (N), ammonium (NH4 ), nitrate (NO3 + (0.02) 0.042 (0.08) 5.28 (0.3) 15.2 (6) 21.7 (2) 11.2 (6) -), dissolved - DON MBN RES ), concentrated PMN )
November 2011
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