Effects of litter source on the dynamics of particulate organic matter fractions and rates of macroaggregate turnover in different soil horizons

Abstract

Summary Soil texture influences the transformation of soil organic matter (SOM), and depletion and reduction in the number of macroaggregates. However, the extent of changes in SOM in response to its quality and mechanisms of stabilization in different types of soil texture is unclear. We evaluated changes in SOM during a 30‐week incubation experiment using seven soils mixed with two sources of litter; Vachellia karroo (Hayne) Banfi & Galasso leaf and Zea mays L. stover. We hypothesized that changes in intraparticulate organic matter (iPOM) are influenced by litter quality • soil type • time interactions, which affect rates of turnover of macroaggregates. A completely randomized design was used in arranging soil jars in the incubator. Free light fractions and coarse and fine iPOM within macroaggregates (>250 μm) decreased exponentially from week 1 to 30 and were significantly (P < 0.05) affected by litter source • soil horizon • time interactions. Trends of changes in fine iPOM fractions were the same in macroaggregates and microaggregates (P < 0.05). The greatest changes in POM fractions occurred 8 weeks after litter incorporation. Both V. karroo leaf and Z. mays stover stabilized macroaggregates during the first 8 weeks after incubation; thereafter they lost their influence. Therefore, we needed to reapply fresh litter after this period. Changes in iPOM fractions and macroaggregate turnover were specific to a soil type, suggesting that different sources of litter have different stabilizing effects in macroaggregates. Soil macroaggregate stabilization and changes in iPOM could be used as indicators to apply more appropriate management practices for soil protection or productivity. Highlights Does the source of organic matter affect transformation rates of different intraparticulate organic matter in the soil? Degradation of organic matter into very fine particulate matter also increases the rate of turnover of macroaggregates. Soil type • litter source interactions greatly influenced the rate of transformation from coarse to fine intraparticulate fractions. Effects of litter quality on dynamics of POM fractions in aggregates and macroaggregate turnover were horizon specific.

Visualizing the dynamics of soil aggregation as affected by arbuscular mycorrhizal fungi

“…This process is dynamic, and some breakdown of macroaggregates is necessary to allow inclusion of incoming labile organic matter into new microaggregates [13] and macroaggregates [14]. Soils with extremely long aggregate turnover times sequester little new carbon but stabilize the carbon in their interior for long times, while extremely short turnover times can potentially sequester a lot of new carbon but could also reduce overall soil stability if aggregates are not regenerated at the same rate that they degrade [12].…”

Use and Management of Animal Manure by the Communal Farmers, Seke District, Mashonaland East Province, Zimbabwe

“…The C & N in the manure were determined using a method described by Parwada and Van Tol (2018). The Olsen extractable P, exchangeable ammonium and nitrate and nitrite were determined as was described by Parwada et al (2018).…”

“…The manure contains important plant nutrients such as N, phosphorus (P), potassium (K), and other secondary nutrients and trace elements, with farmers all over the world having discovered its benefits and associated it with increased crop production (Efthimiadou et al, 2012). The animal manure, unlike synthetic fertilizers, also provides organic matter that can enhance soil infiltration rates, improve water holding capacity, increase cation-exchange capacity (CEC) (Parwada and Van Tol, 2018), and increase soil C (Wuta and Nyamugafata, 2012). Nevertheless, most communal farmers in the SSA e.g Zimbabwe lack recommended manure management practices, such as roofing animal housing, having a water-proof floor or covering manure during storage, causing large nutrient losses during manure storage, increasing greenhouse gas emissions, and reducing the quality of the manure as a fertilizer (AGRA, 2013).…”

Impacts of different prescribed fire frequencies on selected soil chemical properties in a semi-arid savannah thornveld

“…In soil ecosystems where above-ground biomass production is limited like in the arid and semiarid, the organic inputs are mostly from below-ground sources. Soil organic matter is also the most important indicator of soil quality as it generally modifies many soil properties including the soilhydrological properties (Parwada & van Tol, 2018).…”

“…Soil organic matter can significantly influence soil nutrient pools and control total cation exchange capacity (organic and clay mineral) of the soil (Parwada & van Tol, 2018). Fire transforms unstable SOM to a relatively stable form, e.g.…”