Microbial dynamics associated with the decomposition of coconut and maize residues in a microcosm experiment with tropical soils under two nitrogen fertilization levels

Abstract

Aims:The microbial dynamics associated with the decomposition of maize (Zea mays) and coconut (Cocos nucifera) residues were investigated to assess the feasibility of using them as mulch in tropical soils. Methods and Results: Phospholipid fatty-acid (PLFA) profiling, microbial biomass (MB-C), basal respiration, C-cycle enzyme activities and inorganic N dynamics were monitored in a microcosm experiment incubating soil samples with plant residues for 425 days. Maize stover (MS) showed a higher decomposition, respiration rate, MB-C, enzymes activities and shift in microbial community structure than coconut husk (CH), which was barely changed. In MS, the lower N level increased C losses and decreased N mineralization compared to the higher N level. Conclusions: Maize stover is suitable for mulching and has a high potential of increasing soil quality if the proper N fertilization level is used, avoiding excessive C mineralization and N immobilization. Coconut husk decomposition was mostly impaired, indicating that a pre-processing is necessary to improve the benefits of this residue. Significance and Impact of the Study: Tropical soils are prone to degradation. Mulching can promote soil conservation, but depends on residue type and soil chemistry. Our study showed that MS managed under the recommended N fertilization level is suitable for mulching while CH is highly inaccessible for microbial degradation. soil biodiversity, etc. (Labri ere et al. 2015;Lal 2015). Soil erosion can also affect the biogeochemical cycles, resulting in losses of nitrogen (N) and phosphorus (P) similar in magnitude to those induced by chemical fertilization and nutrient removal by crops (Quinton et al. 2010).Management of organic inputs is pivotal for achieving more sustainable agricultural systems (Liu et al. 2014). Crop residues left in the field after harvest contributes to formation of soil organic matter (SOM), which, in turn, can improve soil quality and the mineral nutrition of subsequent crops (Liu et al. 2014). Residues added as mulch also protect soil from physical damage due to rainfall, besides improving water infiltration and storage