13 Dec

Impact of Sewage Sludge Compost Utilization on Chemical Properties of Olive Grove Soils

The United Nations Environmental Program has established that 23% of European soils are chemically, physically or biologically degraded by heavy metals, chemical fertilizers or pesticides, compaction and erosion, or loss of organic matter and biodiversity that may significantly change crop development.

By Beltrn, Eulalia M; de Imperial, Rosario Miralles; Porcel, Miguel A; Beringola, M Luisa; Et al

Field experiments were conducted for four years, between 1998 and 2002, in two olive grove soils of adult olive orchards (Olea europaea L. cv. Cornicabra) in a clay loam soil in Sesefta (Toledo, Spain) and in a sandy loam soil in Aranjuez (Madrid, Spain).

There were four treatments, sewage sludge compost (SSC), sewage sludge compost plus urea (SSC+U), urea (U) and control (C). Each treatment was replicated four times and two depths were studied (0-15 and 15- 30 cm).

Once a year, before spreading sewage sludge compost, soil samples were taken at depths of 0 to 15 cm and 15 to 30 cm. Organic matter, total Kjeldhal nitrogen, phosphorus availability, pH, and electric conductivity were measured. No differences were found between treatment on organic matter and electric conductivity after four years of application of sewage sludge compost to two olive grove soils.

In relation to nitrogen content, sewage sludge compost, only in Sesea, produced higher nitrogen soil content than the traditional urea treatment. Sewage sludge compost applied on olive grove soils improved the Phosphorus availability for the olive tree. In Aranjuez, the use of sewage sludge compost increased the pH of the soil with respect to Urea and Control plots. In Sesea, the reverse effect was found .

Introduction

The United Nations Environmental Program has established that 23% of European soils are chemically, physically or biologically degraded by heavy metals, chemical fertilizers or pesticides, compaction and erosion, or loss of organic matter and biodiversity that may significantly change crop development.

Alternative amendments to traditional manures are sewage sludge compost and municipal solid wastes (Beltrn et al. 2002). It is well documented that sewage sludge application to soils substantially increases nutrient content and crop growth (Smith 1996) as well as improves soil physical properties. Sewage sludge compost contains every nutrient for plant growth, especially N and P. The use of sewage sludge compost also avoids the accumulation of sewage sludge in the environment. (Garca et al. 1991).

Our objective is to study the effect of the addition of sewage sludge compost on the chemical properties of two olive grove soils.

Materials and Methods

Field experiments were conducted for four years, between 1998 and 2002. Two adult olive orchards (Oka europaea L. cv. Cornicabra) were established in a clay loam soil in Sesea (Toledo, Spain) and in a sandy loam soil in Aranjuez (Madrid, Spain) (Table 1). Four treatments were utilized, replicated four times and two depths were studied (0-15 and 15-30 cm). The applied treatments were sewage sludge compost (SSC), sewage sludge compost plus urea (SSC+U), urea (U) and control (C) (Table 2).

TABLE 1.

Classification of the soils

TABLE 2.

Characteristics of the treatments used in the trials

TABLE 3.

Composition of the sewage sludge compost used in the trials

TABLE 4.

Heavy metals on sewage sludge compost (mg.kg^sup -1^)

The sewage sludge compost utilized in the treatments was produced in an aerobic fermentation process utilizing a sewage sludge mixture from six wastewater treatment plants in Madrid. The fresh sewage sludge was dried to reduce the percent moisture. The dried sludge was piled into rows three meters high to develop aerobic fermentation and turned every two weeks for or three months.

All treatments were placed on the soil between the rows of the trees and incorporated by means of harrowing in spring in 1998, 1999, 2000 and 2001. Tables 3 and 4 show the chemical composition of sewage sludge compost used in the trials. The pH was obtained with a glass electrode, using a soil water suspension of 1:2.5 (w/v), electric conductivity was determined in conductivimeter (soil/water ratio, 1:5) at 25C, oxidable carbon by the Walkey-Black method (APHA, AWWA, WPCF, 1992), total Kjeldhal nitrogen by Kjeldhal method (Hesse 1971). P^sub 2^O^sub 5^, K^sub 2^O, CaO and heavy metals concentrations were determined by atomic absorption spectroscopy (AAS) after mineralization with HNO^sub 3^+ HClO^sub 4^ solution (Sims and Kline 1991).

Once a year, before spreading the sewage sludge compost, the soils were sampled at depths of O to 15 cm and 15 to 30 cm between the rows of the trees. Samples were air-dried and crushed to pass a 2 mm sieve. Organic matter, total Kjeldhal nitrogen, electric conductivity and pH were measured as described earlier with the sewage sludge compost. Phosphorus availability was determined by Olsen method (MAPA 1986).

Data were analysed by analysis of repeated measures based on the mixed model, with special parametric structure on the covariance matrices. The basic repeated measures study consisted of completely randomized experimental design with data collected in a sequence of equally spaced points in time. Treatments were assigned to experimental units, and data collected at a sequence of time from each experimental unit. The experimental units are often called subjects.

In our case, the experimental unit or subject was the interaction of Depth*Repetition(Treatment) and the structure of the covariance matrix was AR(1) that specifies a first-order autoregressive structure. The multiple adjustment was for the p-values and confidence limits for the differences of LS-means by the Bonferroni test. The software used was the Procedure Mixed of SAS/STAT 8.2.

Results and Discussion

Organic Matter. Tables 5 and 6 show the ANOVA results from the Aranjuez and Sesena data for organic matter.

In the two olive grove soils, significant differences between Year and Depth were found.

Treatment versus Year on organic matter is shown in Figures 1 and 2 for Aranjuez and Sesena respectively. In Aranjuez, there were no significant differences between treatments (p=0.999). The differences were found between the two depths (p=0.0001). Ranges from 0.80 to 0.2% of organic matter were obtained at 0-15 cm depth and ranges from 0.76 to 0.18% of organic matter at 15-30 cm depth. In Sesea, the ranges were higher. At 0-15 cm depth ranges from 1.3- 0.7% of organic matter and from 1.12 to 0.5% at 15-30 cm depth were found

TABLE 5.

Analysis of variance on organic matter in Aranjuez

TABLE 6.

Analysis of variance on organic matter in Sesea

FIGURE 2. Organic matter (%) in Sesea at 0- 15 cm y 15-30 cm depth

The degradation of the organic matter might be fast, and because of it, significant differences were not observed between treatments with sewage sludge compost (SSC and SSC + U) and treatments without sewage sludge compost (C and U). Depending on application rate, sewage sludge compost increases organic matter in soils, promoting the biological activity in degraded environments (Garca-Orenes, F. et al. 2002). Several authors have observed an increase on organic matter soil content even after two years of application, but an application rate higher in this experiment (Polo, M.J. et al. 2001).

Total Nitrogen. Tables 7 and 8 show the ANOVA results from the Aranjuez and Sesea data for total nitrogen.

TABLE 7.

Analysis of variance on total nitrogen in Aranjuez

TABLE 8.

Analysis of variance on total nitrogen in Sesea

On total nitrogen, in Aranjuez, significant differences were found in the interaction Treatment * Year. In Sesea, significant differences were found between Treatment, Depth, Year and the interaction Treatment * Year.

Figures 3 and 4 show Treatment versus Year on total nitrogen for Aranjuez and Sesea respectively. In Sesea, the interaction between 15 cm depth, SSC treatments and Urea treatments were significantly different in the first three years. The nitrogen content was 13% higher in plots treated with SSC than in those treated with Urea. Miralles de Imperial et al. (2003) in a greenhouse experiment with sewage sludge applied on rooted olive cuttings observed that the content of nitrogen in soil increased linearly in terms of rates. In Sesea 2002 year was significantly different (p<0.05) from 1999-2000- 2001 years. The interaction Treatment*Year was significant (p<0.005) too. The SSC + U treatment provided more nitrogen to the olive grove sou of Sesea in 1999 and 2000. In 2001 and 2002 the SSC treatment provided the most nitrogen. The SSC + U treatment provided the second amount of nitrogen in 2001 and the least amount in 2002. This trend was also observed at the 0-30 cm depth.

FIGURE 3. Total Nitrogen (%) in Aranjuez at 0-15 on y 15-30 cm depth.

FIGURE 4. Total Nitrogen (%) in Sesea at 0-15 cm y 15-30 cm depth.

Phosphorus availability. Tables 9 and 10 show the ANOVA results from the Aranjuez and Sesea data.

In Aranjuez, significant differences between Treatments, Depth and the interaction Treatment* Depth were found.

In Sesea, significant differences between Treatments, Year, Depth, and the interactions Treatment* Year, Treatment*Depth, Year*Depth, Treatment* Deoth*Year were found.

TABLE 9.

Analysis of variance on phosphorous availability in Aranjuez

TABLE 10.

Analysis of variance on phosphorous availability in Sesea

The SSC treatment provided more phosphorus availability in Aranjuez soils at 0-15 cm depth during all the years (Figure 5). This treatment was significantly different from the others (p<0.05). Ranges from 10 mg.kg-1 in C plots to 40 mg.kg-1 in SSC plots were found. Between Control treatment and Urea treatment there we\re no significant differences (p=0.999). At 15-30 cm it can be observed that SSC treatment is significantly different (p<0.05) from the other ones. The ranges of phosphorus availability were lower than at 0-15 cm, from 5 mg.kg-1 in C plots to 25 mg.kg-1 in SSC plots.

In Sesea at 0-15 cm (Figure 6), there was no significant differences between SSC and SSC + U treatments (p=0.99). The significant differences appeared between this two treatments and the other ones (C and U treatments) with a p<0.05. Ranges from 8 mg.kg- 1 in U plots to 50 mg.kg-1 in SSC plots were found. At 15-30 cm the higher concentration of phosphorus was found when SSC + U treatment was applied.

The high content in phosphorus availability in plots amended with SSC is due to the amount of organic matter of SSC that makes phosphorus available to the soil. (Sabater, M. and Boluda, R. 1999). The phosphorus availability increasing in soils by SSC application agree with Tsadillas C.D. et al. (1999) who found in a pot experiment, the application of sewage sludge significantly increased available phosphorus, soil pH, Zn and Cu.

FIGURE 5. Phosphorus availability in Aranjuez at 0-15 cm and 15- 30 cm depth.

FIGURE 6. Phosphorus availability in Sesena at 0-15 cm and 15-30 cm depth.

Sastre Conde, I. et al. (2003) found that the application of sewage sludge compost amendments to a olive trees in a greenhouse increased the content of nutrients (P, N and organic matter). The application of organic wastes to the soil improve the phosphorus availability in soils and their content increases as the rate of application increases. (Blzquez, R. et al. 1999; Burgos, P. et al. 2001).

Tables 11 and 12 show the ANOVA results from the Aranjuez and Sesea data for pH.

In Aranjuez, significant differences were found between Treatments, Year, and in the interaction Treatment * Year. In Sesea, significant differences were found between Treatment, Year, Depth and the interaction Treatment * Year.

TABLE 11.

Analysis of variance on pH in Aranjuez

Treatment versus Year on pH is shown in Figures 7 and 8. In Aranjuez, significantly (p<0.005) higher ranges of pH (2%) were found in SSC treatment than in Control and Urea treatments. Miralles de Imperial et al. (2002) in an emergence test in pots under greenhouse conditions with two types of sewage sludge compost found that the use of sewage sludge compost increases pH. Significant differences were also found in every year (p<0.005). In Sesea, pH in plots treated with SSC + U were significantly (p<0.005) lower than in plots treated with Urea. This result agrees with Sastre-Conde et al. (2003) that in a greenhouse experiment with nursery olive trees and two types of sewage sludge compost found a decrease in soil pH in pots treated with sewage sludge compost. In 2002, there were significantly (p<0.005) higher ranges (3%) of pH than in the other years.

Electric conductivity. Tables 13 and 14 show the ANOVA results from the Aranjuez and Sesea data.

In Aranjuez, significant differences were found in Year and in the interaction Treatment * Year. In Sesea, significant differences were found between Control and Urea treatments and the SSC and SSC + U treatments.

Figures 9 and 10 show Treatment versus Year on electric conductivity for Aranjuez and Sesea respectively. In Aranjuez, there were no significant differences (p=0.999) in the first three years (1999-2001). The differences were found between the first three years and the last one (p<0.005). The interaction Treatment*Year was significant (p<0.005) too. In Sesea, although SSC and SSC + U treatments provided higher electric conductivity to the soils than Control and Urea treatments, the differences were not significant (0.235

<0.495). This agrees with Guidi et al. (1982) that observed a slight increase of electric conductivity after application of sewage sludge compost.

FIGURE 7. pH in Aranjuez at 0-15 cm and 15-30 cm depth.

FIGURE 8. pH in Sesea at 0-15 cm and 15-30 cm depth.

TABLE 13.

Analysis of variance on electric conductivity in Aranjuez

TABLE 14.

Analysis of variance on electric conductivity in Sesea

FIGURE 9. EC (dS/m) in Aranjuez at 0-15 cm and 15-30 cm depth.

FIGURE 10. EC (dS/m) in Sesea at 0-15 cm and 15-30 cm depth.

Conclusions

No increase in organic matter was found after four years of application of sewage sludge compost to two olive grove soils. Possibly there was not enough time for the organic matter to build up in the soil or the amount applied was too small and what was applied may have oxidized and disappeared.

In Sesea, sewage sludge compost produced higher nitrogen soil content than the traditional urea treatment.

Sewage sludge compost applied on a olive grove soils improved the Phosphorus availability for the olive tree at two depths. In Aranjuez, the increase of phosphorus availability is related with the rate of application.

With respect to pH, two different behaviors were found. In Aranjuez, the use of sewage sludge compost increased the pH of the soil with respect to urea and control plots. In Sesea, the reverse effect was true.

No differences were found between treatments with respect to the electric conductivity.

Differences were found in all the parameters between the two depths.

Acknowledgements

The authors are grateful to the FEGA-FEOGA for financing this work through the Project CAO-097-017-C5-1.

The authors wish to thank Mr. Jess L. Garca Ibaez for the agricultural labour and Mrs. Ma Isabel Gonzlez, Mrs. Ma Luisa Surez, Mrs. Esmeralda Surez and Mr. Arturo Amro for their help in analytical work.

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Eulalia M. Beltrn1, Rosario Miralles de Imperial1, Miguel A. Porcel1, M. Luisa Beringola1, Jos V. Martin1, Rosa Calvo2 and M. Mar Delgado1

1, Environment Department, INIA, Madrid, Spain
2. Biometry Department, INIA, Madrid, Spain

Copyright J.G. Press Inc. Autumn 2006

(c) 2006 Compost Science & Utilization. Provided by ProQuest Information and Learning. All rights Reserved.

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