Decomposition Of Corn Residues Research Articles

Short-Term Effect of Nitrogen Fertilization on Carbon Mineralization during Corn Residue Decomposition in Soil

The effect of N fertilization on residue decomposition has been studied extensively; however, contrasting results reflect differences in residue quality, the form of N applied, and the type of soil studied. A 60 d laboratory incubation experiment was conducted to ascertain the effect of synthetic N addition on the decomposition of two corn (Zea mays L.) stover mixtures differing in C:N ratio by continuous monitoring of CO2 emissions and periodic measurement of microbial biomass and enzyme activities involved in C and N cycling. Cumulative CO2 production was greater for the high than low N residue treatment, and was significantly increased by the addition of exogenous N. The latter effect was prominent during the first month of incubation, whereas N-treated soils produced less CO2 in the second month, as would be expected due to more rapid substrate depletion from microbial C utilization previously enhanced by greater N availability. The stimulatory effect of exogenous N was verified with respect to active biomass, microbial biomass C and N, and cellulase and protease activities, all of which were significantly correlated with cumulative CO2 production. Intensive N fertilization in modern corn production increases the input of residues but is not conducive to soil C sequestration.

Applied Liquid N Has No Effect on Corn Residue Decomposition

Applied Liquid N Has No Effect on Corn Residue Decomposition

Identification of labile and stable pools of organic matter in an agrogray soil

The intensity of decomposition of the organic matter in the particle-size fractions from a agrogray soil sampled in a 5-year-long field experiment on the decomposition of corn residues was determined in the course of incubation for a year. The corn residues were placed into the soil in amounts equivalent to the amounts of plant litter in the agrocenosis and in the meadow ecosystem. A combination of three methods—the particle-size fractionation, the method of 13C natural abundance by C3–C4 transition, and the method of incubation—made it possible to subdivide the soil organic matter into the labile and stable pools. The labile pool reached 32% in the soil of the agrocenosis and 42% in the meadow soil. Owing to the negative priming effect, the addition of C4 (young) carbon favored the stabilization of the C3 (old) carbon in the soil. When the young carbon was absent, destabilization or intense decomposition of the old organic matter was observed. This process was found even in the most stable fine silt and clay fractions.

Dynamics of soil amino sugar pools during decomposition processes of corn residues as affected by inorganic N addition

Identifying the impact of inorganic-nitrogen (N) availability on soil amino sugar dynamics during corn (Zea mays L.) residue decomposition may advance our knowledge of microbial carbon (C) and N transformations and the factors controlling these processes in soils. Amino sugars are routinely used as microbial biomarkers to investigate C and N sequestration in microbial residues, and they are also involved in microbial-mediated soil organic matter (SOM) turnover. We conducted a 38-week incubation study using a Mollisol which was amended with corn residues and four levels of inorganic N (i.e., 0, 60.3, 167.2, and 701.9 mg N kg−1 soil). The objective of this study was to examine the effects of inorganic-N availability on fungal and bacterial formation and stabilization of heterogeneous amino sugars during the corn residue decomposition in soil. The surface soil (0–20 cm) used for the experiment was taken from a site in Gongzhuling, Jilin Province of China (43°30′N, 124°48′E). The sampled soils were air-dried, mixed, and passed through a 2-mm sieve. The incubation experiments were carried out at 25 °C, and soil moisture was maintained at 20% gravimetric moisture content by regularly weighing the plastic containers and adding water to the plastic containers during the incubation if necessary. The incubation was destructively sampled at weeks 1, 2, 4, 8, 12, 18, 28, and 38 of the incubation. The whole samples were air-dried, ground (<0.25 mm), and analyzed for amino sugar composition and concentration. Amino sugars (d-glucosamine, d-galactosamine, d-muramic acid, and d-mannosamine) were determined by capillary gas chromatography (GC) after their conversion to aldonitrile acetates (Zhang and Amelung 1996). Soil amino sugar contents and their contribution to SOM accumulation were significantly enhanced by the incorporation of corn residues, and amino sugar concentration maxima were observed during the 38-week-incubation course. Inorganic nitrogen significantly affected the accumulation of amino sugars during the decomposition of corn residues which had a high C/N ratio. It was found that more amino sugars were accumulated with higher inorganic N addition rates. However, when very high N application rates were evaluated, excess inorganic N in soil could not be taken up by microorganisms and some remained as inorganic N in the soil at the end of the incubation. Moreover, the dynamics of the individual amino sugars were different in response to the level of applied inorganic N. Muramic acid, a constituent of bacterial cell walls, was more sensitive to inorganic N supply and showed a faster turnover rate, while glucosamine, a constituent of fungal cell walls, was less sensitive to inorganic N supply. Glucosamine accumulated during the decay process of corn residues, and it was eventually stabilized in the soil. When corn residues were decomposing, individual amino sugar pools were affected by inorganic N addition. Bacterial cell-wall residues played an important role in soil N transformation in the early stages of corn residue decomposition, however, bacterial residues were rapidly remineralized. In the later stages of residue decomposition, amino sugars were assimilated into fungal cell walls which accumulated in soil and contributed to the long-term maintenance of SOM. Therefore, when plant residues with a high C/N ratio are incorporated into the soil, sufficient inorganic N is required for microbial growth. The addition of inorganic N to soils which have received plant residues with C/N ratio ≥30:1 is required to sustain microbial rapid growth; however, oversupply of inorganic N may increase the risk of inorganic N losses from agricultural fields.

Assessing changes in soil microbial communities and carbon mineralization in Bt and non-Bt corn residue-amended soils

The effects of Bt corn ( Zea mays L.) residue on soil microbial communities and rates of C mineralization were investigated. The Bt corn residue had a higher lignin content (12%) and lignin/N (9.9) ratio compared with its non-Bt near-isoline (10% lignin; lignin/N = 8.6). We examined the relationships among the Bt/non-Bt residue properties, residue component, soil texture, sampling time, and tillage management in microcosm and field studies. Bt corn residue incorporated in soils of different textural classes (silty clay, silt loam and sandy loam) in microcosms affected bacterial substrate metabolism. Substrate utilization profiles (Biolog) of soils amended with Bt residue differed from those with non-Bt residue based on principal component analysis (PCA). Denaturing gradient gel electrophoresis (DGGE) patterns revealed only slightly altered microbial communities in the soils amended with Bt residue compared with the non-Bt isoline. Soil texture significantly ( P < 0.05) affected C mineralization and substrate utilization profiles. Carbon dioxide evolution rate constants ( k) of 0.085–0.087 for non-Bt and Bt corn leaf tissue added to silt loam indicated higher rates of soil CO 2 evolution compared with addition of roots and stems ( k = 0.06–0.07). However, cumulative CO 2 production after 73 days was similar regardless of residue component amendment. Significant ( P < 0.05) interactions between soil texture, residue type (Bt versus non-Bt) and residue component illustrated the influence of soil on decomposition. In the field study, sampling time significantly correlated with Biolog metabolic activity and DGGE profiles. The field study also confirmed the effects of Bt residue on total plate count and substrate utilization profiles. Based on the results of the microcosm and field studies, we concluded that incorporation of Bt residue with higher lignin content and lignin/N ratio in soil significantly affected the structure of microbial communities compared with the residue from its non-Bt isoline. Abiotic factors including soil texture and sampling time also influenced the soil microbial communities and the decomposition of corn residues.

Nitrogen Effects on Conservation of Carbon during Corn Residue Decomposition in Soil

AbstractNitrogen fertilization is widely recognized for its potential to help maintain soil organic matter (SOM) concentrations by increasing plant growth and amounts of plant material decomposed in soils. We studied possible mechanisms by which annual additions of more N than needed to maximize yields of corn (Zea mays L.) could cause losses of SOM. Various amounts of stover and NO−3 were added to a Galva silty clay loam (fine‐silty, mixed, mesic Typic Hapludoll), and NO−3 concentrations and CO2 evolution were monitored for periods up to 90 d at 24°C in the laboratory. The added NO−3 suppressed mineralization of C from SOM and stimulated mineralization of C from stover. Adjustment of rates of stover decomposition to temperature regimes normally encountered in Iowa fields after harvest showed that stover decomposition would not be complete within 1 yr and that increases in NO−3 availability decreased the amount of stover C remaining in the soil. This effect of NO−3 could explain how additions of unneeded N could decrease concentrations of SOM in long‐term studies in which residues and NO−3 are added in annual cycles. These observations suggest that practices that reduce unnecessary fertilization could help conserve SOM and reduce net amounts of CO2 released to the atmosphere.

Effects of Soybean and Corn Residue Decomposition on Soil Strength and Splash Detachment

AbstractAlthough field experiments have documented increased soil and water losses after soybeans (Glycine max L.) as compared with corn (Zea mays L.), a “soil effect” appears to be nondetectable by regular laboratory means. Because significant differences in quantity and quality of post‐harvest residues occur between soybean and corn, a laboratory incubation experiment was designed to assess the effect of the plant materials on soil properties. Analysis shows that laboratory incubation of disturbed soil with and without corn and soybean residues at 20°C, with optimal water contents of 25% v/v, decreases splash detachment, increases shear strength and aggregate size after 7 to 14 d. Additions of corn or soybean residues increase soil strength and decrease soil splash in a log‐linear fashion. The most pronounced effects were observed after 14 d. This corresponds to peak microbiological activity, indicating changes in stability are probably related to biological processes. Corn residue at typical field rates (20 Mg/ha) reduced soil splash by about one‐third and increased strength about two times as compared to the check after 14 d of incubation. Incubation with soybean residue for a similar time caused slightly greater soil splash than incubation with the same amount of corn residue, suggesting that small changes in stability are related to residue quality. No difference in soil strength relative to residue quality was detected after 14 d of incubation, indicating a subtle difference between splash and strength as measures of surface‐soil stability. Aggregate size measurements were less sensitive to plant residue treatment and time of incubation than splash or strength.