Can reduced tillage sustain sugarcane yield and soil carbon if straw is removed?

Sarah Tenelli,Ricardo De Oliveira Bordonal,João Luis Nunes Carvalho,Leandro Carneiro Barbosa

doi:10.1007/s12155-019-09996-3

Sarah Tenelli, Ricardo De Oliveira Bordonal + Show 2 more

Open Access

https://doi.org/10.1007/s12155-019-09996-3

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Abstract

Straw removal for bioelectricity, cellulosic ethanol, or other bio-products has become a common practice in Brazilian sugarcane areas, but long-term effects on soil organic carbon (SOC) and yield are unknown. Our objective was to quantify tillage intensity and removal levels on SOC stocks and sugarcane yield on contrasting edaphoclimatic conditions in Brazil. Conventional tillage-CT and reduced tillage-RT coupled with three straw removal levels (none—NR; moderate—MR; total—TR) were combined to create six treatment combinations: CTNR, CTMR, CTTR, RTNR, RTMR, and RTTR, respectively. Sugarcane yield was measured annually and soil samples to a depth of 40 cm were collected and analyzed before and after 5 years of treatments. Neither tillage practices nor straw removal significantly affected sugarcane yield on sandy loam soil, but CTMR, CTTR, and RTTR showed substantial yield reductions on clayey soil. SOC stocks for RTNR increased by as much as 1.64 Mg ha−1 year−1 on clayey soil, while CTMR and CTTR favored depletion of SOC stocks on both soils. Overall, each Mg of straw returned to the soil increased SOC stock by 95 kg ha−1 for clayey soil under both tillage practices and 55 kg ha−1 for sandy loam under the CT system. Furthermore, straw removal decreased microbial biomass C and b-glucosidase activity. These findings suggest that the adoption of RT attenuates the adverse impacts of straw removal on SOC stocks while ensuring sugarcane yields for a more sustainable bioenergy production in Brazil.

Highlights

Sustainable management practices have a major effect on sustaining soil organic carbon (SOC) while providing renewablebased energy resources to biofuel feedstocks and contribute to carbon (C) sequestration from the atmosphere [1]
After the normality verification according to the Shapiro-Wilk test at 5% of significance and homogeneity of variance by the Oneill and Mathews test, the data was subjected to analysis of variance (ANOVA) to assess differences among the six treatments of straw removal under tillage systems and the average results were compared using Tukey’s test (p < 0.05)
Can Reduced tillage (RT) be a feasible strategy to “prevent” SOC loss induced by straw removal while sustaining sugarcane yields? Conclusions drawn from this study suggest that RT system with a moderate straw cover in the soil could potentially provide sustainable use of parts of the straw from the field for bioenergy purposes while enhancing SOC stocks and sustain sugarcane yields over the crop cycle in both soils

Summary

Introduction

Sustainable management practices have a major effect on sustaining soil organic carbon (SOC) while providing renewablebased energy resources to biofuel feedstocks and contribute to carbon (C) sequestration from the atmosphere [1]. Sugarcane is a crop that is grown in a 5- to 6-year cycle of yearly harvests. With the historical replacement of sugarcane burning prior to harvest, a significant amount of straw (i.e., 10–20 Mg ha−1 of dry mass) is deposited on the soil surface annually [5]. Sugarcane straw ( known as trash) consists mainly of green tops and dry leaves [5]. The highenergy potential of sugarcane is very competitive in relation to fossil fuels and can be a consistent source of replacement to mitigate greenhouse gas (GHG) emissions [6]. The sugarcane stalk compartment is the raw material used for 1G ethanol

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