Modifications of soil organic matter structure by long-term pig slurry amendment of tropical soil

Abstract

ABSTRACT This work aimed to study the impacts of long-term pig slurry (PS) amendment by soil organic matter (SOM) structural characterization. The study was conducted over 5 years in an experimental field with PS amendment. Two doses (50 m3 ha−1 and 100 m3 ha−1) of PS were applied to soil twice every year, once before planting the winter crop (Avena strigosa Schreb. + Lolium multiflorum Lam.) and once before planting the summer crop (Zea mays L.). SOM modifications were studied by compositional and spectroscopic analyses. Differences between the fractions were obtained using chemometrics methods. PS amendment of the soil caused increases in the amount of total soil carbon and the humic fraction depending on the duration of PS amendment. Humic acids (HAs) and fulvic acids (FAs) functional groups were modified under both rates of PS amendment. The PS amendment modified the HAs and FAs structure in the first year, and in the last year, the higher application rate (100 m3 ha−1) caused more intense modifications than in earlier years. The cluster and MCR analysis proved that carbohydrate and peptide structures (CAlkyl-O,N; CAlkyl-O; CAlkyl-di-O), lignin (CArom-H,R; CArom-O,N) and lignocellulosic carbon were incorporated into the soil HAs and FAs structures.