Tillage and Nitrogen Fertilizer Influence on Carbon and Soluble Silica Relations in a Pacific Northwest Mollisol

Abstract

and in the tillage pan was maintained at a high level only when crop residue returns increased and soil pH Long-term experiments are ideal for evaluating the influence of was maintained above 5.6 (Pikul and Allmaras, 1986). agricultural practices on soil organic carbon (SOC) accretion. Little is known about the influence of tillage and N fertilization on SOC Long-term use of N fertilizer also reduced soil pH (Rasdistribution and silica (Si) movement in a soil. This study: (i) deter-mussen and Rohde, 1989), as a linear function of N mined the effect of tillage and N fertilizer on SOC accretion in a Walla applied, in both the MP and SW systems. Acidifying Walla silt loam (coarse-silty, mixed, superactive, mesic Typic Haploxeffects were concentrated in the upper 7 and 22 cm of eroll), and (ii) examined the subsequent influence of fine organic the SW and MP system, respectively. matter (FOM) on Si movement. A long-term wheat (Triticum aesti-The Walla Walla silt loam is one of many Mollisols vum L.)-fallow experiment was established in 1940, in a randomized in the Pacific Northwest that contains a high concentrablock with split-plot design. Soil cores (2-cm increments) from two tion of potentially mobile Si, ranging from 40 to 100 mg tillages (moldboard plow, MP; and sweep, SW) and two N rates (45 and SiO 2 kg Ϫ1 soil in the form of H 4 SiO 4 (Douglas et al., 180 kg N ha Ϫ1) were used to measure coarse organic matter (COM), 1984). Douglas et al. (1984) showed that the concentra-FOM, pH, bulk density (b), water-soluble C (C ws), and water-soluble Si (Si ws). The FOM fraction (6.6 kg C m Ϫ2) in SW was 14% higher tion of H 4 SiO 4 in these soils increased as pH decreased, (5.8 kg C m Ϫ2) than in MP for the 180 kg N ha Ϫ1 rate. After 44 yr when base cations were leached out of the soil profile. of N additions, the SOC storage (6.2 kg C m Ϫ2) for the 180 kg N ha Ϫ1 Measurements of Si ws , soil pH, amorphous Si, and total rate increased 3% above that for the 45 kg N ha Ϫ1 (6.0 kg C m Ϫ2). acidity in the same Walla Walla silt loam (Baham and Total Si ws in the B horizon were 34 and 39% greater than in the Ap Al-Ismaily, 1996) indicated that Si had leached from horizon for the MP and SW systems, respectively. Interaction of tillage the upper Ap layer, illuviated into the lower Ap, and and N with Si ws suggests that SOC provides a mechanism to suppress deposited in the boundary between the Ap and B hori-Si solubility, which impacts siliceous pan formation, reduces soil mezons. Higher mechanical (penetrometer) resistance, eschanical resistance, and enhances drainage and plant growth.

Nitrogen Affects Wheat and Canola Silica Accumulation, Soil Silica Forms, and Crusting

“…Destructive sampling occurred every 1, 3, 7, 10, 14, 21, and 28 d. Analyses included: surface resistance, water‐soluble Si (Si ws ), Si am , crust thickness, and scanning electron microscope (SEM) imaging. For these experiments, Si ws is defined as the Si extracted at a 1:5 ratio of soil/water (Gollany et al, 2005). Amorphous soil silica is operationally defined as the Si extracted by a 0.5 M Na 2 CO 3 solution (Follett et al, 1965).…”

“…Water-soluble silica was determined by shaking 5 g of soil and 25 mL of distilled water in 50-mL polyethylene tubes for 30 min, settling overnight, centrifuging for 10 min at 1500 rpm (480 g), and filtered with Whatman No. 42 filter paper (Gollany et al, 2005). Amorphous soil silica was extracted by shaking 1 g of soil and 25 mL of 0.5 M Na 2 CO 3 in an 80°C water bath for 10 min (Follett et al, 1965).…”

“…This process is responsible for the hardness of siliceous pans (Chadwick et al, 1987). Increased aqueous H 4 SiO 4 leaching with decreasing soil pH has been observed in multiple studies (Douglas et al, 1984;Brown and Mahler, 1987;Gollany et al, 2005), yet crop residue returns will recycle Si to the soil surface.…”

Poultry Manure Application Time Impact on Corn Grain Production in a Crider Silt Loam

“…Commercial fertilizer is known to cause a reduction in soil pH over time, because of its acidifying effects from nitrification of NH 4 + Gollany et al, 2005) and its P and N contents (Tisdale et al, 1999). Poultry litter was expected to increase soil pH slightly or cause no change, owing to its high Ca content (McGrath et al, 2010;Mitchell and Tu, 2006).…”

Effect of corn stover harvest and winter rye cover crop on corn nitrogen fertilization

“…Reasons for this are limited information and research evaluating these impacts in an integrated or long-term basis. Therefore, short-term experiments can show immediate effects of tillage and N fertilization on crop productivity and response to N rate, but long-term experiments are required to evaluate the lasting influence of such agricultural practices on soil C and other soil properties (Gollany et al, 2005).…”