Role of Crop Rotations in the Dynamic of Soil Organic Matter Pools

Rodrigo Santos Moreira,Debora Marcondes Bastos Pereira Milori,Aildson Pereira Duarte,Marcio Koiti Chiba,Caio César Zito Siqueira,Isabella Clerici De Maria

doi:10.5539/jas.v10n8p341

Abstract

Soil organic matter is considered a key attribute for a sustainable agricultural production and is influenced by the quantity and quality of the crop residue deposited on the soil surface. Therefore, different crop rotations could change the soil organic matter pools. The objectives of this study were to evaluate the soil carbon pools obtained by chemical and physical fractionation methods and the humification index under different crop rotations in a no-till system. We test the following hypothesis: a) the distribution of C and N among the soil organic matter fractions depends on plant species rotation schemes and; b) labile fractions are more sensitive to the input of crop residues and therefore, more suitable for evaluating the impact of different crop rotations in the soil organic matter quality. We evaluated four crop sequences (corn/corn/corn; corn/wheat/corn; soybean/wheat/corn and soybean/corn/corn) in a no-till system. A five-year reforested area was used as reference. We determined the total C and N contents, the mineral-associated C and N, the light fraction of C and N, the labile carbon extracted with KMnO4 and the soil organic matter humification index. We found narrow differences between the crop rotation systems in the total C and N levels, the mineral-associated C and N fractions and the labile C extracted with KMnO4. The diversification of the agricultural system with soybean in crop rotation favored the accumulation of light fraction C and N in the soil that were more efficient to provide information about the changes in the soil organic matter quality.

Highlights

Soil organic matter (SOM) is a complex mix of plant and animal residues in various stages of decomposition and synthesis that plays an essential role in the chemical, physical and biological processes relate to soil ecosystem functions
At the 10-20 cm depth we do not found a significant difference to total soil organic carbon (TOC) and total nitrogen (TN) between the rotation SWC and the reference area, while in the layer of 30-40 cm there is no significant difference among all treatments (Figure 1)
Total C and N contents changed slightly between the crop rotations. These results indicate that five years were not sufficient for the crop rotation systems to promote a significant increase in TOC content when compared with monoculture and grasses succession systems (CCC and CWC treatments)

Summary

Introduction

Soil organic matter (SOM) is a complex mix of plant and animal residues in various stages of decomposition and synthesis that plays an essential role in the chemical, physical and biological processes relate to soil ecosystem functions. For this reason, maintaining the SOM status is important to preserve the capacity of soils sustain plant production (Favoretto et al, 2008). Labile fractions tend to respond faster to the crop management changes and by driving crucial soil processes, such as nutrient cycling and biological activity, these fractions can significantly influence the quality of an agricultural land (Chen et al, 2012; Duval et al, 2013)

Objectives

Methods

Results