Abstract
The use of deinking paper sludge (DPS) as a fertilizer instead of sending it to landfill could play a role in reducing greenhouse gases and improving soil properties. The objectives of this study were (1) to evaluate the changes in the physical (permeability and structural stability), chemical (particularly soil pH), and biological (microbial metabolic quotient (qCO2), microbial biomass soil CO2 emissions) of a calcareous agricultural soil following two successive annual amendments with three treatments (0, 30, and 60 Mg DPS ha−1—control, DPS30, and DPS60, respectively); and (2) to determine whether the addition of N-fertilizer to these treatments (controlF, DPS30F, and DPS60F, respectively) causes changes to soil fertility. The DPS application increased soil organic matter (+0.80%: DPS60 vs. control; and +0.35%: controlF vs. DPS60F), available phosphorus (+23.14 mg kg−1: DPS60 vs. control; and +14.34 mg kg−1: DPS60F vs. controlF), potassium (+0.6 g kg−1: controlF vs. DPS30F), and calcium (+0.28 g kg−1: DPS60 vs. control). The 60 Mg DPS ha−1 rate improved permeability and structural stability, regardless of the presence or absence of N-fertilizer. On the other hand, the 60 Mg DPS ha−1 rate without N-fertilizer lead to a decrease in total mineralization rate and qCO2, thereby indicating a reduction in CO2 emissions. The rate of 60 Mg ha−1 DPS could be effectively used to enhance the permeability and stability (soil restoration) and mitigate CO2 emissions, whereas the 30 Mg ha−1 rate could be used as fertilizer to improve the fertility of calcareous soils.
Highlights
The intensification of agricultural activities has led to serious environmental problems and one of the main issues is related to the maintenance of soil fertility at different levels [1]
The deinking paper sludge (DPS) has an alkaline pH and contains large quantities of nutrients, especially C, P, Ca, and Mg which are derived from wood chips and/or products used during the pulping process or pulp bleaching, whereas the C:N was high, showing the importance of N supply in maintaining soil fertility (Table 1)
The addition of organic fertilizer to the soil amended with paper sludge increased straw and ear yields [5,10,15]. These results show that DPS amendment increases or decreases soil biological activity depending on the N content and form of the raw amendment and on the N soil content, which is a good index of the mineralization process
Summary
The intensification of agricultural activities has led to serious environmental problems and one of the main issues is related to the maintenance of soil fertility at different levels [1]. The use of organic amendments (OA) instead of chemical ones improves soil fertility by slowly releasing nutrients to support soil quality and productivity [2]. The incorporation of OA leads to an increase in carbon dioxide (CO2 ) emissions from the soil as a result of rapid soil organic matter decomposition [3]. N2 O is generated by the microbial transformation of organic and inorganic N and is enhanced under wet conditions [7]. Nunes et al [8] showed that the addition of deinking sludge as an organic amendment with a very high C/N ratio in alkaline soil can cause N immobilization and reduce yield
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