Carbon stock and humification index of organic matter affected by sugarcane straw and soil management

Aline Segnini,Ladislau Martin-Neto,Isabella C De Maria,João Luís Nunes Carvalho,Marcelo Luiz Simões,Denizart Bolonhezi,Wilson Tadeu Lopes Da Silva,Débora Marcondes Bastos Pereira Milori,Heitor Cantarella

doi:10.1590/s0103-90162013000500006

Abstract

The maintenance of sugarcane (Saccharum spp.) straw on a soil surface increases the soil carbon (C) stocks, but at lower rates than expected. This fact is probably associated with the soil management adopted during sugarcane replanting. This study aimed to assess the impact on soil C stocks and the humification index of soil organic matter (SOM) of adopting no-tillage (NT) and conventional tillage (CT) for sugarcane replanting. A greater C content and stock was observed in the NT area, but only in the 0-5 cm soil layer (p < 0.05). Greater soil C stock (0-60 cm) was found in soil under NT, when compared to CT and the baseline. While C stock of 116 Mg ha-1 was found in the baseline area, in areas under CT and NT systems the values ranged from 120 to 127 Mg ha-1. Carbon retention rates of 0.67 and 1.63 Mg C ha-1 year-1 were obtained in areas under CT and NT, respectively. Laser-Induced Fluorescence Spectroscopy showed that CT makes the soil surface (0-20 cm) more homogeneous than the NT system due to the effect of soil disturbance, and that the SOM humification index (H LIF) is larger in CT compared to NT conditions. In contrast, NT had a gradient of increasing H LIF, showing that the entry of labile organic material such as straw is also responsible for the accumulation of C in this system. The maintenance of straw on the soil surface and the adoption of NT during sugarcane planting are strategies that can increase soil C sequestration in the Brazilian sugarcane sector.

Highlights

Brazil is the largest producer of sugarcane (Saccharum spp.), producing 571 million tons from an area of 8.34 million hectares in the 2011/2012 harvest
This study aimed to assess the impact on soil C stocks and the humification index of soil organic matter (SOM) of adopting notillage (NT) and conventional tillage (CT) for sugarcane replanting
Laser-Induced Fluorescence Spectroscopy showed that CT makes the soil surface (0–20 cm) more homogeneous than the NT system due to the effect of soil disturbance, and that the SOM humification index (HLIF) is larger in CT compared to NT conditions

Summary

Introduction

Brazil is the largest producer of sugarcane (Saccharum spp.), producing 571 million tons from an area of 8.34 million hectares in the 2011/2012 harvest. Due to the energy potential of sugarcane straw, the industry has shown interest in its use both for electricity generation and for cellulosic ethanol production Despite this growing interest in the industrial sector, the maintenance of the straw on the soil surface increases soil carbon (C) stocks (Galdos et al, 2009), promotes nutrient cycling (Oliveira et al, 1999), increases soil biological activity (Souza et al, 2012a), reduces weed infestation (Monquero et al, 2008), reduces soil erosion (Sparovek and Schnug, 2001) and increases sugarcane yield (Trivelin et al, 2002). The maintenance of large amounts of straw on the soil surface can result in some negative impacts (Magalhães et al, 2012)

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