A Method for Measuring Incorporated Crop Residue and Associated Soil Properties

Abstract

Controlled placement and depth distribution of crop residues are major objectives for tillage management. Appropriate methodology has provided quality information about surface placement, but the distribution of buried crop residue has not been readily measurable. A method was developed to measure dry bulk density (ρb), incorporated coarse organic matter (COM), and organic carbon (C) concentration using one soil sample. Cores, each 0.3‐m long, were taken with a specially constructed sampler (19‐mm diam.); each 0.3‐m core was separated into 20‐mm increments for subsequent analysis. After air‐drying, COM was estimated as that crop residue retained on a 0.5‐mm mesh sieve; C concentration measurements and an associated conservation‐of‐C algorithm were used to estimate COM because the incorporated crop residue could not be completely separated from contaminant soil. These ρb and COM had a CV of 5 and 20%, respectively. A depth function of ρb distinguished primary tillage from secondary tillage and traffic; a tillage pan produced by the moldboard base was usually detected by ρb. Moldboard plowing vs. sweep or chisel tillage consistently produced different depth distributions of COM; at least 85% of the COM was above 0.1 m when tilled with a chisel or sweep and >45% was below 0.1 m when moldboard plowed. Total COM in the profile ranged from 68 to 23% of that measured at harvest, respectively, 28 wk earlier in a wheat‐peas rotation and 82 wk earlier in a wheat‐fallow rotation. Long‐term use of a moldboard plow vs. a chisel or sweep for primary tillage produced consistently different profiles of organic C concentration.

Carbon and nitrogen contents of different-sized light fraction organic matter as influenced by tillage and residue management

“…Magid and Kjaergaard (2001) separated particulate organic matter by size and found that the 0.4-mm fraction closely resembled LF organic matter (B1.4 specific gravity) in C and N contents. Allmaras et al (1988) proposed, in relation to measuring the recovery of crop residues from soil, a coarse organic matter fraction 0.5 mm and B2 mm. Therefore, it appears reasonable to suggest that a distinction between LF materials, on the basis of the lability of their C and N, can be made somewhere between 0.25 and 1 mm.…”

Wheat response and residual soil properties following subsoiling of a sandy loam in eastern Montana

“…Soil bulk density and gravimetric water were each measured on the same day and on the same transects used for CI sampling. Bulk density samples were taken with a tube sampler described by Allmaras et al (1988). The sampler had a cutting tip of 19.6 mm.…”

Infiltration and Soil Properties as Affected by Annual Cropping in the Northern Great Plains

“…Soil bulk density samples were taken with a tube sampler as described by Allmaras et al (1988). The sampler has a cutting tip of 19.6 mm.…”

“…Investigators using thin sampling increments of 0.02 m have successfully identified unique profiles of C and bulk density in long-term tillage and residue management experiments (Allmaras et al, 1988;Pikul and Allmaras, 1986;Pikul et al, 1993).…”