Tillage and Manure Effects on Soil and Aggregate‐Associated Carbon and Nitrogen

Abstract

In agricultural systems, maintenance of soil organic matter (SOM) has long been recognized as a strategy to reduce soil degradation. No‐tillage and manure amendments are management practices that can increase SOM content and improve soil aggregation. We investigated the effects of 10‐yr of different tillage systems and N sources on soil aggregate‐size distribution and aggregate‐associated C and N. The study was a split‐plot design replicated four times. The main plot treatment was tillage (no‐tillage, NT; conventional tillage, CT) and the subplot treatment was N source (manure, M; NH4NO3 fertilizer, F). The experiment was established in 1990 on a moderately well‐drained Kennebec silt loam (Fine‐silty, mixed, superactive mesic Cumulic Hapludoll) with continuous corn (Zea mays L.). In 1999, soil samples were collected (0‐ to 5‐cm depth) from the field treatments and separated into four aggregate‐size classes (>2000, 250–2000, 53–250, and 20–53 μm) by wet sieving. Labile C and N content of all aggregate‐size fractions were measured using 28‐d laboratory incubations of intact and crushed aggregates. No‐tillage and M treatments significantly increased total C and N and the formation of macroaggregates. Conventional tillage in comparison with NT significantly reduced macroaggregates with a significant redistribution of aggregates into microaggregates. Aggregate protected labile C and N were significantly greater for macroaggregates, (>2000 and 250–2000 μm) than microaggregates (53–250 and 20–53 μm) and greater for M than F indicating physical protection of labile C within macroaggregates. No‐tillage and M a lone each significantly increased soil aggregation and aggregate‐associated C and N; however, NT and M together further improved soil aggregation and aggregate‐protected C and N.

Influence of 20–Year Organic and Inorganic Fertilization on Organic Carbon Accumulation and Microbial Community Structure of Aggregates in an Intensively Cultivated Sandy Loam Soil

“…Previous studies have suggested that OC is more effectively protected and more stable in microaggregates, whereas macroaggregates provide a niche for the storage of labile C [3], [5], [10]. Fertilization, a common agricultural practice, has been found to significantly influence aggregate formation and OC distribution in aggregates [11], [12].…”

Organic Amendments to a Wheat Crop Alter Soil Aggregation and Labile Carbon on the Loess Plateau, China

“…External organic amendments as well as increased fine root inputs provided more organic sources compared with the unfertilized treatment. Mikha and Rice (2004) reported that aggregate-protected labile C and N fractions were significantly greater for 0.25-to 2-mm aggregates in manure treatment than microaggregates (<0.25 mm) in chemical fertilization treatment and that 0.25-to 2-mm aggregates contribute more to relevant nutrient cycling. Mikha and Rice (2004) reported that aggregate-protected labile C and N fractions were significantly greater for 0.25-to 2-mm aggregates in manure treatment than microaggregates (<0.25 mm) in chemical fertilization treatment and that 0.25-to 2-mm aggregates contribute more to relevant nutrient cycling.…”

“…Maintaining high stability of soil aggregates is essential for improving crop productivity, preventing soil degradation, and minimizing environmental pollution (Mikha and Rice, 2004). Maintaining high stability of soil aggregates is essential for improving crop productivity, preventing soil degradation, and minimizing environmental pollution (Mikha and Rice, 2004).…”

Influence of Composted Dairy Manure and Perennial Forage on Soil Carbon and Nitrogen Fractions during Transition into Organic Management

“…To evaluate soil mineralizable (active) forms of C and N, a short-term aerobic laboratory incubation was conducted for 28 days at 25 • C under a soil water content of −0.033 MPa [26,27]. The 8-mm sieved and air-dried soil was conditioned to a water content of 0.21 g H 2 O g −1 soil (approximately −0.033 MPa) by gradually adding an appropriate amount of deionized (DI) water before the incubation [28].…”

“…Mineralizable C was determined using the static sealed chamber method to evaluate CO 2 evolution for the 28-day incubated soil [26,27]. In short, 40 g of recently wetted soil (0.21 g H 2 O g −1 soil) associated with each treatment was added to a 170 mL specimen cup and placed in an approximately 1-L (the volume of each canning jar was measured precisely) wide mouth canning jar containing 20 mL of water.…”