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Title: Long-term manure impacts on soil aggregates and aggregate-associated carbon and nitrogen

item Mikha, Maysoon
item HERGERT, GARY - University Of Nebraska
item NIELSEN, REX - University Of Nebraska
item Benjamin, Joseph
item Jabro, Jalal - Jay

Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/16/2014
Publication Date: 3/13/2015
Publication URL:
Citation: Mikha, M.M., Hergert, G.W., Nielsen, R.A., Benjamin, J.G., Jabro, J.D. 2015. Long-term manure impacts on soil aggregates and aggregate-associated carbon and nitrogen. Soil Science Society of America Journal. 10.2136/sssaj2014.09.0348.

Interpretive Summary: Long-term studies are important in documenting the changes in soil quality and soil organic carbon (SOC) conservation due to different management practices. Evaluation soil aggregate stability is important in evaluation soil erosion and SOC dynamics. Improving our knowledge with soil aggregate stability is essential to understand soil resistance to erosion, SOC conservation, and consequently soil sustainability. In general, SOC, plant root, fungal tissue, and microbial byproduct act like glue that connects soil aggregates together. Also, soil resistance to water and wind erosion can be improved with good relationship between SOC and soil aggregates stability. The objectives of this research were to measure how the long-term (100 years) of tillage, organic amendment, and synthetic fertilizer affect soil quality parameters such as SOC, soil aggregate stability, and aggregate-associated C. The tillage in this long-term (Knorr-Holden) furrow irrigation continuous corn study site is a combination of moldboard plowing and disking with N applied as Manure (M), synthetic N fertilizer (F), and F+M. After 100 years of organic amendment and yearly plowing and disking practices, we found that Continuous M amendment and the combination of F+M increased SOC at all depths compared with the F treatment. Soil aggregation was also increased with M and F+M treatment. We also found that tillage practices in combination with M or F+M could be the management practices that sustain soil quality and soil sustainability.

Technical Abstract: Long-term studies document that soil properties influenced by management practices occur slowly. The objectives of this study are to evaluate 100 yrs of manure (M) additions and plowing on soil organic C (SOC) and soil total N (STN), water stable aggregate (WSA), and aggregate-associated-C and N. The Knorr-Holden furrow irrigation continuous corn (Zea mays L.) site was initiated in 1910 on Tripp sandy loam with M, commercial fertilizer (F), the combination of F+M, with continuous disking and plowing practices. Soil samples were collected from the 0- to 5-, 5- to 10-, 10- to 15-, and 15- to 30-cm depths. Soils were fractionated into four aggregate size classes (>1000, 500-1000, 250-500, and 20-53 micron) by wet sieving. Continuous M amendment substantially increased SOC at all depths compared with the F treatment. The combination of F+M further increased SOC at the surface 0- to 15-cm by approximately 36% for 80+M and by 16% for 160+M compared with 15- to 30-cm depth. Aggregate size distribution increased with M and F+M compared with F with the corresponding increase in microaggregate amounts associated with the F and control. At 0- to 30-cm, microaggregates were approximately 1.8 to 4.9 fold greater than the macroaggregates. Aggregate-associated-C masses were greater in microaggregates than macroaggregates reflecting greater amounts of microaggregates present in this sandy soil. A positive relationship was observed between SOC and aggregate-associated-C. Over all, tillage practices in combination with M or F+M addition could be a management practice that improves aggregate stability, SOC conservation, and soil sustainability.