David Peña

Cumulative and residual effects of de-oiled two-phase olive mill waste application to soil on diuron sorption, leaching, degradation, and persistence

Laboratory and field experiments were conducted to evaluate the influence of de-oiled two-phase olive mill waste (DTPOMW) amendments on the sorption-desorption, degradation, leaching, and persistence of the herbicide diuron in a representative olive grove soil. The soil was amended in the laboratory with DTPOMW at the rates of 5% and 10% (w/w), and in the field with 27 and 54 Mg ha(-1) of DTPOMW for 7 years. Cumulative and residual effects were evaluated in the last year and 2 years after the last DTPOMW field application (2005 and 2007, respectively). The results showed that the adsorption of diuron to the soil significantly increased in the presence of DTPOMW in the laboratory and field-amended soils, and that humic acid content was mainly responsible for this increase. The DTPOMW soil application only significantly increased the half-life of diuron in the laboratory-amended soils, ranging from 8.6d for the original soil to 51 d at the greater application rate. The DTPOMW amendments significantly reduced the downward mobility of diuron, and reduced the amount of herbicide leached in the laboratory and field-amended soils, and no residues of diuron were detected in the leacheate of the residual-amended columns. In the field study, DTPOMW addition increased the persistence of diuron in the upper 10 and 5 cm of the soils in the cumulative and residual years, respectively, decreasing the herbicides vertical movement through the amended soils with increasing DTPOMW rate. This study has shown that in olive grove soils DTPOMW amendment may be an effective management practice for controlling ground water contamination by diuron.

Sorption, leaching and persistence of metribuzin in Mediterranean soils amended with olive mill waste of different degrees of organic matter maturity.

Metribuzin is a widely used herbicide, and worldwide is one of the most important contaminants in ground and surface waters. The aim of this study was to evaluate the impact amendment with fresh, composted, and field-aged olive mill waste (OW, COW, and AOW, respectively) had on the behaviour of this herbicide in four typical Mediterranean soils. A batch equilibration method was used to determine metribuzin adsorption-desorption. Leaching experiments were studied in hand-packed soil columns. Half-lives were calculated with incubation studies. Soil dehydrogenase activity (DHA) was also monitored. Metribuzin adsorption in the soils increased not only with increasing amounts of amendment, but especially with increasing degree of organic matter humification. Compared to unamended soils, the adsorption capacity increased by between 81% and 216%, 135% and 193%, and by 363% for the OW, COW, and AOW amended soils, respectively, at a 5% rate of application. The addition of COW enhanced metribuzin degradation in all the soils. In contrast, OW addition increased metribuzin persistence, attributable mainly to the inhibitory effect of this amendment on microbial activity, especially in the acidic soils. The AOW-amended soils, which had the smallest labile fraction of soil organic matter and greatest degree of humification, showed the shortest herbicide persistence. The OW and COW amendments significantly reduced the amount of metribuzin leached. This was especially so in the latter case because of the higher sorption capacity and the faster degradation of the pesticide. The use of OW as organic amendment, especially when it has a high degree of organic matter humification, may be a useful management practice for reducing the risk of groundwater contamination by metribuzin in soils with low organic matter content.

Behavior of MCPA in four intensive cropping soils amended with fresh, composted, and aged olive mill waste.

An evaluation was made of the impact of olive mill waste and its organic matter transformation on the sorption, desorption, leaching, and degradation of the herbicide MCPA when the waste was applied to four Mediterranean soils. The soils were amended in the laboratory with fresh, composted, and field-aged olive mill waste (OW, COW, and AOW treatments, respectively). It was found that the greater the amount of OW applied to the soils, but especially the greater its organic matter maturity, the greater the adsorption of MCPA. Compared with unamended soils, at the 5% rate of application the adsorption capacity increased by between 9.8% and 40%, 148% and 224%, and by 258% for the OW, COW, and AOW amended soils, respectively. The hysteresis coefficients were significantly lower in the OW-amended soils than in AOW or COW-amended soils, indicating that the adsorbed MCPA could be easily desorbed in OW-amended soils if the amendment is not aged or composted. While the OW addition greatly extended the persistence of MCPA, the application of COW enhanced MCPA degradation in all the soils, as corresponded to the increased soil microbial activity indicated by the higher levels of soil dehydrogenase activity. Fresh OW amendment significantly increased the amount of MCPA leached (from 13.7% in the most alkaline soil to 36.7% in the most acidic, at the 5% rate of application), favored by the higher levels of water soluble organic carbon content. However, leaching losses of the herbicide were reduced by up to 39.9% and 55.3% in the COW- and AOW-amended soils at the 5% loading rate, respectively. The use of OW with a high degree of organic matter maturity may be regarded as a potentially useful management practice to reduce MCPA leaching in soils with low organic matter content. The application of fresh OW, however, could well increase the risk of groundwater contamination by this herbicide, especially in acidic soils.

Impact of oiled and de-oiled olive mill waste amendments on the sorption, leaching, and persistence of S-metolachlor in a calcareous clay soil

Agricultural practices based on periodic inputs of organic amendments are strongly recommended for Mediterranean agro-ecosystems. Such amendments can change the soils properties and transport characteristics, and hence affect the behaviour and fate of pesticides. S-metolachlor is an herbicide commonly used in intensive crops. The aim of this study was to investigate the influence of fresh oiled (OW) and de-oiled two-phase olive mill waste (DW) amendments on the sorption, leaching, and persistence of the herbicide S-metolachlor in a calcareous clay soil. The soil was amended in the laboratory with OW and DW at the rates of 2.5% and 5% (w/w). Significant increases in S-metolachlor sorption were observed in all amended soils. The addition of OW and DW increased the herbicide half-life from 27 d for the original soil to 41 and 47 d at the higher application rate of OW and DW, respectively. There was a significantly greater retention of the herbicide at the higher OW and DW loading rate. However, whereas the amount of S-metolachlor in the leachate was reduced by increasing the amount of OW, it was unaffected by increasing the amount of DW. The results lend support to the potential of OW and DW amendments as an effective management practice to increase S-metolachlor persistence in soils. This increase does not necessarily ensure decreased leaching of the herbicide but it could also increase the risk of surface water contamination at higher application rate.

De-oiled Two-phase Olive Mill Waste Application Impact on Phosphorus Sorption and Fractionation in a Mediterranean Soil Under Olive Production

Low phosphorus (P) availability is a critical impediment to agricultural use of P-fixing soils. De-oiled two-phase olive mill waste (DTOMW) may be used as a soil amendment that can increase P availability and consequently improve crop production. The aim of this study was to investigate the effect of DTOMW amendments to soil on the fractionation, sorption, and buffering capacity of P in soils collected from a typical olive grove amended in the field with 27 and 54 Mg ha−1 of DTOMW for 7 years. Cumulative and residual effects were evaluated in the last year of DTOMW application and 2 years subsequent to the last application. A modified Hedley fractionation scheme was used to evaluate the change in soil P forms, whereas the potential for sorption of P was evaluated by applying the surface Langmuir models to sorption isotherms. The P fractionation results indicated an increase in all P fractions (P < 0.05) in the studied samples. The order of the rates of increase in concentrations of P fractions was HCl-Pi > NaHCO3-Pi ≈ NaOH-Po > HCl-Po ≈ NaOH-Pi > H2O-Pi > NaHCO3-Po > residual P > H2O-Po in the cumulative year, whereas in the residual year, the order of increase was HCl-Pi > NaOH-Po > NaHCO3-Pi > H2O-Pi > NaOH-Pi > HCl-Po > residual P > NaHCO3-Po > H2O-Po. The DTOMW amendments significantly decreased the P sorption maxima (P < 0.05). Most of the total P sorption potential was attributed to low-energy sites, independent of the amendment applications received. The DTOMW soil application decreased indices of P-binding intensity at both high- and low-affinity sites, decreased the P equilibrium buffering capacity, and increased the equilibrium P concentration, indicating that P availability increased with increasing DTOMW rate and also with increasing humified organic matter fraction. This study has shown that in olive grove soils, successive DTOMW amendments may be an effective management practice for controlling their ability to fix inorganic P and increase P availability for the crop for at least 24 months after its application.

Behaviour of bentazon as influenced by water and tillage management in rice-growing conditions: Behaviour of bentazon in rice-growing conditions

Bentazon is a widely used herbicide in rice agroecosystems that has commonly been found in water resources. To assess how tillage and water regimes affect sorption/desorption, dissipation and leaching of bentazon in Mediterranean rice-growing conditions, field experiments were carried out using tillage and flooding (TF), tillage and sprinkler irrigation (TS), no-tillage and sprinkler irrigation (NTS) and long-term no-tillage and sprinkler irrigation (NTS7). After 3 years, the Kd values in TS were 2.3, 1.6 and 1.7 times lower than the values in NTS7, NTS and TF respectively. Greater sorption of bentazon was related to higher contents in total organic carbon and, although to a lesser extent, in humic acids and dissolved organic carbon. The persistence of bentazon was significantly greater under anaerobic (half-life DT50 = 94.1-135 days) than under aerobic (DT50 = 42.4-91.3 days) incubation conditions for all management regimes. Leaching losses of bentazon were reduced from 78 and 74% in TS and TF to 61 and 62% in NTS7 and NTS respectively. The mid- and long-term implementation of sprinkler irrigation in combination with no-tillage could be considered a management system that is effective at reducing water contamination by bentazon in Mediterranean rice-growing agroecosystems.

De-oiled two-phase olive mill waste may reduce water contamination by metribuzin.

The impact of de-oiled two-phase olive mill waste (DW) on the behavior of metribuzin in Mediterranean agricultural soils is evaluated, and the effects of the transformation of organic matter from this waste under field conditions are assessed. Four soils were selected and amended in the laboratory with DW at the rates of 2.5% and 5%. One of these soils was also amended in the field with 27 and 54 Mg ha(-1) of DW for 9 years. Significant increases in metribuzin sorption were observed in all the amended soils. In the laboratory, the 5% DW application rate increased the t1/2 values of metribuzin from 22.9, 35.8, 29.1, and 20.0 d for the original soils to 59.2, 51.1, 45.7, and 29.4d, respectively. This was attributable mainly to the inhibitory effect of the amendment on microbial activity. However, the addition of DW transformed naturally under field conditions decreased the persistence down to 3.93 d at the greater application rate. Both amendments (fresh and field-aged DW) significantly reduced the amount of metribuzin leached. This study showed that DW amendment may be an effective and sustainable management practice for controlling groundwater contamination by metribuzin.