**4.1 About soil quality**

*Tannins - Structural Properties, Biological Properties and Current Knowledge*

nins extracted from *Sedum takesimense* and *Sapium baccatum* [40].

**3.3 Tannins and their mechanisms for plant disease control**

deeper knowledge about their mode of action would be desirable.

the activation of plant post-infectional defense [33].

Secretion System and the Quorum Sensing, respectively [39, 43].

the Δ*hrpA* nonpathogenic mutant of Psn23 [39].

100 mM aqueous solution.

extracts were demonstrated to be able to give a statistical reduction of the hyperplastic symptoms produced by the inoculation of *Pseudomonas savastanoi* pv. *nerii* strain Psn23 on cuttings from 2-year-old twigs of *Nerium oleander*, in comparison to those untreated. In addition, a significant decrease of bacterial multiplication was observed on tannin-treated plants, which was comparable to the in planta growth of

A strong antibacterial activity against the destructive causal agent of tomato bacterial wilt *Ralstonia solanacearum*, both *in vitro* and *in vivo*, was found for tan-

The profiling of the phenolic compounds present in young leaves of the two apple cultivars "Enterprise" and "Idared," highly resistant and highly susceptible to fire blight, respectively, was estimated and evaluated both before and after *E. amylovora* infection. According to this data, the activity of 13 selected phenolics was tested *in vitro* against *E. amylovora*, at 10, 50, and 100 mM in aqueous solution. Gallic acid was among the most effective to suppress the bacterial growth. Moreover, its efficacy was confirmed *in vivo*, by significantly limiting the development of disease and *E. amylovora* infection on pear fruitlet slices when applied as

The biological activity of tannins strongly depends from their highly variable chemical structure, and tannins basically can act as metal ion chelating and protein complexing agents and antioxidants, in addition to their well-known antimicrobial properties. However, in view of their potential application in plant protection, a

Experiments carried on bacterial phytopathogen *Clavibacter michiganensis* with the ellagitannin HeT extracted from strawberry leaves demonstrated that its bactericide activity is related to a dose-dependent inhibition of the oxygen consumption rate and respiration, as a consequence of its interaction with cell membranes [41]. The absence of any toxicity was assessed for several tannins, such as epigallocatechin gallate and catechin, up to 1 μM by using as a target the membrane protein Ca2+-ATPase from the sarcoplasmic reticulum (SR). SR belongs to the ubiquitous and highly conserved proteins of the so-called P-type ATPase family, whose members are present in the cellular membrane of any living organism and involved in numerous transport processes. Conversely, copper suppresses almost completely Ca2+-ATPase activity at just 0.1 μM concentration

An alcoholic extract obtained from the peel of pomegranate, and mainly containing tannins, was found active as resistance inducer. This extract elicits defense responses when applied to harvested citrus fruits, expressed as an increase in reactive oxygen species and in the expression of five genes which are pivotal during

Tannins have been also shown to possess noticeable inhibition abilities on some enzymatic activities strictly related to the virulence of phytopathogenic bacteria. The virulence of the *Dickeya chrysanthemi* is mainly dependent from its production and secretion of several cell wall-degrading enzymes, such as pectate lyases and proteases. Tannic and gallic acid are efficient to give a total inhibition of *D. chrysanthemi* pectate lyase at concentrations of 400 and 800 μg/ml, respectively [42]. At last, tannins can also negatively interfere with other bacterial systems which are essential for their pathogenicity and virulence on plants, such as the Type Three

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Cu2+ ions [39].

Soil is a natural resource that we must conserve and protect. In this sense, we must ensure that various soil properties (physical, chemical, biological, microbiological, and biochemical), capable of maintaining the quality, sustainability, and functionality of soils, respond to the soil protection criteria. Soil properties effected by the size, activity, and the composition of the microbial biomass included water holding capacity, infiltration rate, erodibility, aggregate stability, nutrient cycling, nutrient capacity, and soil organic matter content (soil function). Soil quality cannot yet be defined in quantitative terms; however, it should be possible eventually to define soil quality and sustainability quantitatively by the appropriate integration of specific quantitative terms, so that the effects of management on soil quality can be determined. Soil quality is a dynamic character, and many significant indicators must be sensitive to small changes in key soil properties. However, tools to detect the impact of changes in soil functionality are needed. Soil enzymes are extremely important in assessing the status or the conditions of the soil environment. This is because enzymes' and microorganisms' activity and biodiversity are related with the most important elements for soil sustainability and functionality (C, N, P, and S). Many extracellular enzymes are absorbed to, complexed with, or entrapped within soil clays and humics, and they may have a long-term stability.

The demand for biofertilizers is increasing since the last decade owing to its ecofriendly characteristics and a worldwide trend to reduce the reliance on chemically derived fertilizers. The Asia-Pacific shared approximately 34% of the total demand in 2011. European and Latin American countries are the leading consumers of biofertilizers, owing to stringent regulations imposed to chemical fertilizers which would eventually be replaced by biofertilizers.

## **4.2 About biopesticides**

In the Evergreen Project, different experiments using polyphenol extracts as biopesticides were carried out. We show (only as an example) some results obtained on soils from a kiwi (*Actinida chinensis*) crop, where some polyphenol extracts were used as biopesticides. The bacteria (*Pseudomonas syringae actinidiae*) were used as pathogen agent, a vascular pathogen, whose most conspicuous symptom is the red-rusty exudation which covers bark tissues on trunks and twigs.

The polyphenol extracts used in this experiment were the following:

Form 1 (liquid): chestnut polyphenol 2%, olive polyphenol 1% in water (1:10). Form 2 (liquid): chestnut polyphenol 1,5%, olive polyphenol 1%, and grape seeds 0.3% in water (1:10).

In addition, CuSO4 has been used to compare a possible conventional treatment and another way to combat some pathogen microorganisms (biopesticides as polyphenol extracts). The total treatments in this assay were (1) control− (without bacteria), (2) control+ (with bacteria), (3) CuSO4− (CuSO4 without bacteria), (4) CuSO4+ (CuSO4 with bacteria), (5) form 1, and (6) form 2.

In this study, some biological and biochemical parameters measured on soil treated with polyphenol extracts have been shown. The use of biochemical parameters (soil enzyme activities) can be important to know the possible effect of polyphenols on the cycle of the important elements such as C, N, and P.

Application methods for polyphenols and pathogen:


Results were the following.

#### *4.2.1 Total organic carbon and total N*

One of the most interesting parameters for soil quality is the organic carbon content, indicative of the organic matter content of the soil. The organic C induces fundamentally the productivity and fertility of the soil. Its presence in the soil is of great interest from two points of view: environmental (fixation of C in the soil) and agronomical (soil fertility).

In our experiment (**Table 1**), no significant differences were observed for organic C between the control soil and the soils treated with polyphenols. We know that polyphenols are organic products, and they should be implied in mineralization and humification processes; they could alter soil organic C. However, the addition of polyphenols to the soil did not alter organic C content in the soils studied. This confirms that the doses used for polyphenols in this study are not high enough to affect this type of parameter.

Nitrogen enhances plant growth, improves the quality of crops, and increases seed and fruit production. Nitrogen in the soil is usually supplied by decomposition of organic material, commercial fertilizers, and nitrogen-fixing bacteria. The desirable amount varies between crops; however, too much nitrogen can have adverse effects especially on the environment.

The differences found in soil total N in our experiment (**Table 1**) can be attributable to the variability of soil and our technical analyses; for this reason, it can be


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**Table 2.**

*Hydrolysable Tannins in Agriculture*

polyphenols' addition.

*4.2.2 Enzymatic activities*

compounds.

*4.2.3 Phosphatase*

*DOI: http://dx.doi.org/10.5772/intechopen.86610*

several measurements based on soil enzymes.

synthesized only when available P is deficient.

**Phosphatase activity (μmol PNF h<sup>−</sup><sup>1</sup>**

indicated that the variations observed in this parameter cannot probably be due to

Enzyme activities related to the cycle of elements (carbon, nitrogen, phosphorus, or sulfur) are of paramount importance in soil quality. Among these enzymes we propose the study of phosphatases, ureases, proteases, and different enzymes related to C cycle such as β-glucosidases. Indicators of the microbial population activity (dehydrogenase activity) will give an accurate notion of the impact of the addition of these products on microbial activity. For a general assessment of the functional and structural changes in microbial community, we have carried out

Most enzymes found in the soil, in particular the hydrolases, are extracellular and have a great environmental interest. In addition, these extracellular enzymes may be free and exposed to rapid denaturation or immobilized together with mineral or organic colloids. Generally, those immobilized enzymes in mineral and/or organic colloid change in their status, nature, and properties (such as kinetics, stability and mobility of enzymes) and are less prone to proteolytic denaturalization, since they are physically and chemically associated with other surrounding chemical

The agronomic and biotechnological importance of phosphatase is that it activates the transformation of organic P into inorganic forms of P available to plants. We have determined alkaline phosphatase since we have worked with basic soils (**Table 2**). Phosphatases are inhibited by inorganic P, the final product of their enzymatic reaction. This is due to a feedback inhibition, so phosphatases are

In our study, no statistical differences between treatments were appreciated in this enzyme activity. This indicates that the addition to the soils of polyphenol products does not change the phosphorous cycle in the soil. Some differences in this enzyme activity were noted throughout the experimental period, greater phosphatase activity being detected at the start than at the end of the experiment. This fact could be due to P mobilization from organic to inorganic forms, in order to make it available to plants. The P cycle, studied by phosphomonoesterase activity, seems not to be affected by the polyphenol addition to the soil since little differences were observed as regards phosphatase activity between the soils treated with polyphenols

Control− 6.779 b 4.028 a Control+ 7.118 b 5.197 a CuSO4− 6.072 ab 5.373 a CuSO4+ 6.206 ab 5.560 a Form 1 6.391 ab 5.886 a Form 2 5.349 a 5.324 a *The same letter for each parameter indicates no significant differences between treatments (Tuckey's method, p < 0.05).*

 **soil) T0 Tf**

 **g<sup>−</sup><sup>1</sup>**

*Evolution of soil alkaline phosphatase activity in kiwi soils (initial, T0, and final Tf).*

#### **Table 1.**

*Total N, total C, and total organic carbon, measured in kiwi soils at the end of the experiment.*

indicated that the variations observed in this parameter cannot probably be due to polyphenols' addition.
