Laboratory Soil Handling Affects CO2 Respiration, Amino-N and Water Stable Aggregate Results

Reduction of soil fertility and production efficiency resulting from excessive application of chemical fertilizers is universal in rapeseed-growing fields. The main objective of our study was to assess the effects of biochar combined with nitrogen fertilizer reduction on soil aggregate stability and rapeseed yield and to identify the relationship between yield and soil aggregate stability. A two-factor field experiment (2017–2019) was conducted with biochar (0 (C0), 10 (C10), 20 (C20) and 40 t·ha−1 (C40)) and nitrogen fertilizer (180 (N100), 144 (N80) and 108 kg N·ha−1 (N60)). Experimental results indicated that under N100 and N80 treatments, C10 significantly increased the macro-aggregates (R0.25), mean weight diameter (MWD) and geometric mean diameter (GMD) of soil water stable aggregate by 14.28%–15.85%, 14.88%–17.08% and 36.26%–42.22%, respectively, compared with C0. Besides, the overall difference of the soil water-stable aggregate content in 2–5 mm size range among nitrogen treatments was significant under the application of C10, which increased by 17.04%–33.04% compared with C0. Total organic carbon (TOC) in R0.25 of soil mechanical-stable aggregates was basically all increased after biochar application, especially in 0.25–1 mm and 1–2 mm aggregates, and had an increasing trend with biochar increase. C10 significantly increased rapeseed yield by 22.08%–45.65% in 2019, compared with C0. However, the reduction of nitrogen fertilizer reduced the two-year average rapeseed yield, which decreased by 11.67%–31.67% compared with N100. The highest yield of rapeseed was obtained by N100C10 in two consecutive years, which had no statistical difference with N80C10. However, the two-year yields of N80C10 were all higher than those of N100C0 with increase rate of 16.11%, and which would reduce 35.43% nitrogen fertilizer in the case of small yield difference, compared with the highest yield (2.67 t·ha−1) calculated by multi-dimensional nonlinear regression models. The regression analysis indicated R0.25, MWD and GMD had the strong positive associations with rapeseed yield, whereas percentage of aggregate destruction (PAD0.25) had a significant negative correlation with rapeseed yield. This study suggests that the application of biochar into upland purple soil could improve soil structure, increase the content of TOC in macro-aggregates under nitrogen fertilizer reduction as well as replace part of nitrogen fertilizer to achieve relatively high rapeseed yield.

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Impact of Effective Microorganisms (EM) Application on the Physical Condition of Haplic Luvisol

Agronomy ◽

10.3390/agronomy10071049 ◽

2020 ◽

Vol 10 (7) ◽

pp. 1049 ◽

Cited By ~ 1

Author(s):

Jacek Pranagal ◽

Sławomir Ligęza ◽

Halina Smal

Keyword(s):

Organic Carbon ◽

Carbon Content ◽

Physical Condition ◽

Total Porosity ◽

Organic Carbon Content ◽

Effective Microorganisms ◽

Water Capacity ◽

Water Stable Aggregates ◽

Water Stable Aggregate ◽

Stable Aggregate

The study set out to determine changes in the soil air-water properties, the water-stable aggregate share and organic carbon content as effects of a five-year application of effective microorganisms (EM-A). The hypothesis that long-term applied EM-A biopreparations have a positive effect on the soil physical condition has not been confirmed. Haplic Luvisols originating from silt were studied in a field experiment after EM-A biopreparation treatment. The soil samples with the natural structure preserved intact were collected three times each year. The properties of the soil determined in the study were: particle density, total organic carbon content, bulk density, total porosity, air capacity, air permeability, soil moisture at sampling, field water capacity, available water content, unavailable water content, and water-stable aggregate content. The ratio of field water capacity and total porosity (FC/TP) was calculated. It was found that EM-A application primarily leads to a decrease in the content of organic carbon and water-stable aggregates. This was an adverse effect. Total organic carbon (TOC) and water-stable aggregates proved to be very sensitive indicators for assessing the soil physical condition. However, changes in soil compaction and air–water properties did not show significant deterioration. Our research addresses the data gaps about EM application to soil.

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Physiological and molecular characterisation of microbial communities associated with different water-stable aggregate size classes

Soil Biology and Biochemistry ◽

10.1016/j.soilbio.2005.02.037 ◽

2005 ◽

Vol 37 (11) ◽

pp. 2007-2016 ◽

Cited By ~ 39

Author(s):

R.K. Väisänen ◽

M.S. Roberts ◽

J.L. Garland ◽

S.D. Frey ◽

L.A. Dawson

Keyword(s):

Microbial Communities ◽

Aggregate Size ◽

Molecular Characterisation ◽

Size Classes ◽

Water Stable Aggregate ◽

Stable Aggregate

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Stabilities of ant nests and their adjacent soils

International Agrophysics ◽

10.2478/v10247-012-0050-6 ◽

2012 ◽

Vol 26 (4) ◽

pp. 355-363 ◽

Cited By ~ 2

Author(s):

B.C. Echezona ◽

C.A. Igwe

Keyword(s):

Structural Stability ◽

Aggregate Stability ◽

Soil Surface ◽

Adaptive Mechanism ◽

Ant Nests ◽

Water Stable Aggregate ◽

Dispersion Ratio ◽

Stable Aggregate ◽

Termite Nest ◽

Relative Vulnerability

Abstract Nests habour ants and termites and protect them from harsh environmental conditions. The structural stabilities of nests were studied to ascertain their relative vulnerability to environmental stresses. Arboreal-ant nests were pried from different trees, while epigeous-termite nests were excavated from soil surface within the sample area. Soils without any visible sign of ant or termite activity were also sampled 6 m away from the nests as control. Laboratory analysis result showed that irrespective of the tree hosts, the aggregate stabilities of the ant nests were lower than those of the ground termite, with nests formed on Cola nitida significantly showing lower aggregate stability (19.7%) than other antnest structures. Clay dispersion ratio, moisture content, water stable aggregate class <0.25mm and sand mass were each negatively correlated with aggregate stability, while water stable aggregate class1.00-0.50 mm gave a positive correlation. Nest structures were dominated more by water stable aggregate class >2.00 mm but path analysis demonstrated that water stable aggregate class <0.25 mm contributed most to the higher aggregate stability of the termite nest than the other nest. Nest aggregates had greater structural stability compared to the control soil. The higher structural stability of termite nests over other nest and soil was considered a better adaptive mechanism against body desiccation.

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