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Two-phase olive mill waste (TPOMW) and dairy cattle slurry (CS) are two organic materials with low economic value and limited potential for reutilization despite their high concentrations of nitrogen (N) and organic matter. A laboratory incubation for ca. 100 d was performed to assess the short-term N and carbon (C) dynamics in a soil amended with TPOMW, CS and a mixture of both materials in order to: (i) explore the potential benefits of mixing TPOMW with CS to promote mineral N immobilization and avoid nitrate leaching, and (ii) assess the potential for increased soil C stocks after TPOMW, CS or TPOMW+CS application. Our results clearly showed that the combined application of TPOMW+CS caused N immobilization; hence, it contributes to tying up the applied N, resulting in a decrease of critical N leaching, which is usually observed after CS application. No clear N mineralization was observed in the TPOMW+CS treatment during the incubation period.It appears that an application of 30 Mg ha−1 of TPOM...

Modern olive (Olea europaea L.) mill extraction techniques generate a large amount of two-phase olive mill waste (OMW) containing up to 90% organic matter. Recycling OMW as a soil amendment may represent a solution for its disposal, especially in Mediterranean areas, where many soils are characterized by very low organic matter levels. A 10-yr field study was conducted to evaluate the long-term sustainability of raw OMW disposal as a soil amendment on an olive grove in Elvas, Portugal. The soil was amended with OMW at rates of 0, 30, and 60 Mg ha ―1 , dry weight equivalent, for 8 yr, with cumulative and residual effects being assessed in the last year and 2 yr after the last application. Long-term applications of OMW to soil led to cumulative and residual effects on soil physical [aggregate stability and bulk density (D b )], chemical [total organic carbon (TOC) and its humified fractions, total N, available P, and K], and biochemical [dehydrogenase (DH), urease (UR), 3-glucosidase (GLU), alkaline phosphatase (PHO), and arylsulfatase (ARS) activities] properties, and contributed to an increase in olive yields compared with the control (>17%, > 1.47 Mg ha ―1 ). However, electrical conductivity (EC) rose significantly with OMW application, especially in the residual year, ranging from 0.513 dS m ―1 for the unamended soil to 2.29 dS m ―1 at the 60 Mg ha ―1 application rate. Repeated addition of OMW to olive grove soils may be a useful strategy for recycling this organic amendment to improve soil fertility and increase yields. However, long-term use of OMW increases the risk of soil salinity, especially if application rates are >30 Mg ha ―1 .

Two-phase olive mill waste (TPOMW) is a by-product of olive oil extraction, contains up to 90% organic matter, and may be used as soil amendment. To investigate the impact of TPOMW amendments to soil on the fractionation, adsorption, and buffering capacity of P, experiments were conducted on soils collected from a typical olive grove amended for 5 yr with 0, 30, and 60 Mg ha -1 of TPOMW. A modified Hedley fractionation scheme evaluated the change in soil P forms while surface models were used to fit the data. The P fractionation results suggested and increase in HCI-P fraction. Other P pools, such as residual-P, NaHCO 3 -Pi, NaOH-Pi, NaOH- Po, soluble-P, and NaHCO 3 -Po increased to lesser degrees. A two-surface Langmuir model fit the adsorption data better than a uniform layer model and underestimation of the P adsorption was observed when the traditional Langmuir equation was used. The TPOMW amendments significantly decreased the P adsorption maxima (α = 0.05) and most of the P was adsorbed on low energy sites, independent of the amendment applications received. The TPOMW soil application decreased indices ofP-binding intensity at both high and low affinity sites, decreased the P equilibrium buffering capacity, and increased the equilibrium P concentration (EPC). Coupled with the low energy of P binding, results implied an increase in the readily soluble P, and thus runoff p losses could potentially increase in TPOMW amended soil.

A five-year field study was conducted to evaluate the potential use of oiled and de-oiled two-phase olive mill waste (TPOMW and DTPOMW, respectively) as soil amendment on a representative olive grove soil: a Cutanic Luvisol. Treatments included a non-amended control, TPOMW1, TPOMW2, DTPOMW1 and DTPOMW2 (30, 60, 27 and 54 Mg ha−1 dry weight equivalent). Significant increases (P

Semiarid Mediterranean soils under intensive continuous cultivation have a net deficit of C, and addition of organic wastes is becoming a common practice as a disposal strategy and an interesting solution to redress this deficiency. A 2-yr greenhouse study using wheat (Triticum aestivum L.) was conducted to evaluate the potential use of the final solid waste of the new technology of olive-oil extraction (de-oiled two-phase olive mill waste, DTPOMW) as a soil conditioner and amendment agent. Two representative Mediterranean agricultural soils, a Typic Haploxeralf (TH) and a degraded Lithic Xerorthent (LX) were used. Treatments included five DTPOMW rates ranging from 0 to 40 Mg ha -1 combined with mineral fertilizer. Significant direct and residual increases in organic C, total N, available K, cation exchange capacity, and aggregate stability were observed in both soils; however, available P decreased significantly. In the first year of the experiment, an application of 40 Mg DTPOMW ha -1 had a depressive effect on grain yield and on the N and P content in the wheat grain for the LX soil, while in the TH soil there was a positive effect on yield at the same loading rate. There was an increased residual fertilization and amendment effect of DTPOMW for both soils during the second experimental year, and the grain yields increased by 23 and 202% when 40 Mg DTPOMW ha -1 was applied to the TH and LX soils, respectively. For both soils, the best fits to grain yield vs. DTPOMW rates were with a quadratic regression (R 2 = 0.977, P < 0.001 for TH; R 2 = 0.983, P < 0.001 for LX). Raw DTPOMW may be a potentially valuable soil amendment agent and source of organic matter, N, and K because it maintains a positive, beneficial effect on wheat grain yield and soil properties for 24 mo following application.

This study was conducted under greenhouse conditions to evaluate the potential use of SPS as a fertilizer, amendment and/or liming agent for wheat (Triticum aestivum L.). Two representative Mediterranean agricultural soils, a Cambic Arenosol (cmAR) and a Cromic Cambisol (crCM) were used. Treatments included four sludge rates ranging from 0 to 40 g kg−1 (equivalent of 0, 38, 88 and 120 Mg ha−1). A significant increment in soil pH, organic carbon, N total, available P and exchangeable K were observed in both soils. Sludge application significantly increased N and decreased Zn, Mn and Cu concentrations in wheat. Wheat grain yields were reduced by 33% and 37% when 120 Mg SPS ha−1 was applied to cmAR and crCM soils, respectively, due apparently to unavailability of Mg. However, straw yields, with much lower Mg requirements, increased significantly with SPS rates. Secondary pulp mill sludge seems to be a potential source of organic matter, N, P, K and a potential soil amendment liming agent for acid soils, when appropriate supplemental fertilizer was provided. For grain crops grown in these soils, addition of Mg is required for proper nutrient balance.