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Residue Particle Size Effect on Soil Properties

Managing crop residues during and following harvest is an issue that merits attention to ensure that maximum positive effects from that residue are fully realized. The effect of corn residue particle size on subsequent soil properties is addressed in an article (see below link) that appears in the May 3, 2018 online edition of Agricultural and Environmental Letters.

Major points from the article follow.

•   The premise of the study was that field operations may/will differentially influence crop residue size distributions, and thus potentially alter the decomposition rates of that residue as well as soil carbon [C] and nitrogen [N] dynamics.

•   Objectives of the reported study were to determine the effect of corn residue particle size on microbial respiration and soil C and N dynamics in a laboratory-scale experiment that modeled the 0- to 5-cm (0-2 in.) soil layer in a no-till production system.

•   Corn residue size classes of 1 (<0.4 mm), 2 (0.4-0.8 mm), 3 (0.8-6 mm), and 4 (>6 mm) were created from corn stalk and leaf residue collected from a post-harvest bale of corn residue.

•   Three amounts or rates of residue (0, low, and high) that were scaled to the highest and lowest residue amounts on the soil surface in a field study were mixed with topsoil.

•   Respiration (CO2 evolved/microbial activity) during incubation of soils was different among residue rates in the order of high>low>none at 30 and 60 days after treatment imposition. Respiration from size classes 1-3 were similar at these sampling times, but all were greater than respiration from size class 4, indicating greater microbial activity in the residue of size classes 1-3.

•   At 60 and 150 days after treatment imposition, soil C was similar across all size classes of residue, but all size classes had more soil C than the 0 residue control.

•   There was no effect of residue rate on soil N during the experiment period. The largest residue size class 4 had the lowest soil N at 150 days after treatment imposition, and all residue size classes except size class 4 (largest) maintained soil N at or above the initial soil N level.

•   All residue size classes had lower soil nitrate values than the no-residue control at 30, 60, and 150 days after treatment imposition, indicating net N immobilization by the residue. At 30 and 60 days after treatment imposition, the smaller-size classes (1 & 2) had less soil nitrate than the larger-size classes (3 & 4); however, at the 150-day sampling, the smaller-size classes had mobilized increasing amounts of N while the larger-size classes had progressively immobilized more N.

Take-Home Message

•   These results indicate that, in addition to residue quantity, residue particle size may also influence soil properties affected by that residue.

•   The various mechanical apparatuses that are used to shred crop residue at harvest likely will produce varying particle sizes of that residue, and that can affect soil properties that include soil C and N dynamics and microbial activities. Although this may not be an issue to producers (although it could affect timing of soil N availability to a following soybean or corn crop), it does indicate that residue particle size distribution should be documented in residue management studies so that accurate interpretation of data and results from these studies are forthcoming and relatable to unique conditions in producer fields.

Resource Reference: Stetson, Lehman, and Osborne. May 3, 2018. Corn Residue Particle Size Affects Soil Surface Properties. Agric. Environ. Lett. 3:180004.

For an up-to-date discussion of crop residue management, click here.

Composed by Larry G. Heatherly, July 2018, larryheatherly@bellsouth.net