**3. Functions of permanent grassland**

Agriculture traditionally puts emphasis mainly on productive function of permanent grasslands. They are source of both livestock fodder and plant biomass used for alternative purposes. For productive purposes, however, only a part of permanent grassland can be used. In some regions, the requirements of grass fodder are lower than the amount that permanent grasslands are able to produce. Therefore, great deal of area can remain unused. Nevertheless the grasslands that are not used for production are also very valuable parts of landscape, as they hold broad scale of so-called non-productive functions.

#### **3.1 Productive functions**

Production of permanent grasslands is in a close relationship with amount and quality of produced biomass. Productive function of permanent grasslands is historically connected particularly with providing fodder for livestock. In this way, permanent grasslands significantly contribute to human diet by providing fodder for livestock and thus allowing production of human foodstuff (milk and meat). It is for this reason that the research of production potential of grasslands was for the major part focused on optimizing relationship between production of fodder, its quality and productivity of animals.

Permanent grassland is defined as a land used permanently (for five years or more) for herbaceous forage crops, either cultivated or growing wild (FAOSTAT, 2011). Under favourable conditions, the grass species prevail in grasslands. However varied ecological conditions allow expansion of large amount of different plant species, where legumes are, for many reasons, very important. The plant composition is the result of interaction of ecological factors of placement and the methods of cultivation. The mediation of succession, such composition of natural species is created on sites that in given ecological conditions and specific way of utilization thrives the best. Throughout the years this balance is also created on newly founded stands seeded with mix of grasses and

Depending on place of origin we can discern between two basic types of permanent

 **Natural grasslands –** were created without human intervention. They are situated on steppe, marshland and peat bog locality, in areas above high altitude tree-lines. Production of biomass is negatively affected by less favourable conditions of locality.

 **Semi-natural grasslands –** are situated in areas originally planted with trees. Their existence is dependent on continuous human intervention and cultivation such as grazing or/and cutting. They often have a potential for large yields and they can be used intensively. Among this group we can also find grasslands created by seeding of

Permanent grasslands belong to agricultural systems with very high environmental value. They are among the most biologically active and most productive vegetation types with fast cycle of growth and high capability of transferring chemical elements in biosphere. Their

Agriculture traditionally puts emphasis mainly on productive function of permanent grasslands. They are source of both livestock fodder and plant biomass used for alternative purposes. For productive purposes, however, only a part of permanent grassland can be used. In some regions, the requirements of grass fodder are lower than the amount that permanent grasslands are able to produce. Therefore, great deal of area can remain unused. Nevertheless the grasslands that are not used for production are also very valuable parts of

Production of permanent grasslands is in a close relationship with amount and quality of produced biomass. Productive function of permanent grasslands is historically connected particularly with providing fodder for livestock. In this way, permanent grasslands significantly contribute to human diet by providing fodder for livestock and thus allowing production of human foodstuff (milk and meat). It is for this reason that the research of production potential of grasslands was for the major part focused on optimizing

relationship between production of fodder, its quality and productivity of animals.

importance comes from two key aspects: productive and non-productive functions.

landscape, as they hold broad scale of so-called non-productive functions.

These grasslands are used mostly extensively.

mix cultural grasses and species of legumes.

**3. Functions of permanent grassland** 

**3.1 Productive functions** 

legumes.

grasslands:

The usage of biomass for animal nutrition is still dominant way of its utilization, but in the recent period the importance of this traditional relation has been reduced. The main reasons for this can be considered reducing the quantity ruminants, especially in the countries of Central and Eastern Europe. As a result of increasing milk and meat productivity of animals, in suitable regions there is an increase of amount of fodder being produced from arable land (legume-grass mixture, maize). Because of this and other reasons (for example political and financial support for renewable energy) there has been in last 10 – 15 years significant increase in usage of biomass produced from permanent grasslands for alternative purposes (Hohenstein & Wright, 1994; Prochnow et al., 2009a, 2009b; Rösch et al., 2009).

According to Prochnow et al. (2009b), the grassland biomass is suitable in many ways for producing energy. Currently it is used in practice as a feedstock for biogas production and as solid biofuel for combustion. Future pathways can include the production of lignocellulosic bioethanol, synthetic biofuels or synthetic natural gas. Feedstock from grassland will also be used as raw material for the bio-industry within Green Biorefineries (Kromus et al., 2006, as cited in Prochnow et al., 2009b).

If suitable management of permanent grasslands regarding productive and nonproductive functions stays the same, the change in how the final product is being used will not have a negative impact on farming of permanent grasslands. Permanent grasslands also have an important function in relation with arable land. Ruminants transfer the biomass through digestion and partially use it for their need. The remaining 35 – 50 % of organic matter is excreted in form of excrements. Organic matter in form of farm fertilizer is then used primarily on arable land and there it is important factor contributing to its fertility. When we utilize grass biomass for energy, however, loss of organic matter is higher. Biogas fermentation can degrade cellulose to an extent of about 80 % (Ress et al., 1998). Usage of biomass for direct combustion leads to 100 % loss of organic matter. Energy utilization of biomass can therefore lead to reduction in return of organic matter into soil, in comparison with traditional system, where fodder is utilized by ruminants.

With reduction of return of the organic matter into the soil, there can be disruption in organic balance of the agricultural system, which can lead to number of negative consequences (reduction in fertility of the soil, increase in leaching nutrients into the underground water, increased hazard of erosion etc.). It is necessary to reduce hazards to arable lands such as these by applying effective countermeasures, for example by increasing the share of legumes in crop rotation or by growing catch crops (Brant et al., 2011). The risk is not significant in permanent grasslands. The root system of the plants creates sufficient amount of organic matter inside the soil, so it is not necessary to fertilize them organically at a regular base.

#### **3.2 Non-productive functions**

Permanent and semi-natural grassland are very important not only as a source of fodder, but they also play a significant role in environment (Stypiński et al., 2009). These nonproductive functions of permanent grasslands interfere in different fields such as:

Utilization of Permanent Grassland for Biogas Production 175

As far as energy flows in ecosystem are concerned, it is more apposite to monitor the amount of produced energy from specific area of land. Expressing primary production of stands in energy units allows considering the suitability of applied management from the point of view of expressed energy inputs and outputs in the system. To calculate these balances the energy requirements of individual applied arrangements must be known and it

The amount of energy in biomass is possible to determine on the basis of calorimetric measurement. The principle of calorimetric determination of the volume of gross weight is based on burning down a sample in oxygen atmosphere and recording resulting increase of temperature in calorimetric system. The gross calorific value of the substance that is being

*m*

Δ T – Increase in temperature of the calorimeter system during a combustion experiment (K)

It is possible to use acquired gross calorific value to determine other parameters, such as:

Heating value of biomass (the usage of biomass as a fuel for direct combustion).

Net calorific value (calorific value of combustible substance; the weight of sample

The usage of calorimetric method for studying plants has been already presented by Long (1934). The content of energy in plant material is given by the chemical composition in the plants and it can differ for individual plant species (Yajing et al., 2007). In mixed association, such as permanent grasslands, the content of energy is dependent on composition of species, but it can be changed during the vegetation (Neitzke, 2002). It depends on proportion of individual parts of plants (Sims & Singh, 1978), on ecological or climatic

As far as anthropogenic aspects are concerned, frequency of mowing and dosage of nutrients are considered to be the most important factors influencing the production of permanent grasslands. When appraising the significance of those as well as other ways of management on any of the indicators (the quality of the fodder, the content of energy in the fodder etc.), it is necessary to consider mainly experiments, where the chosen type of management is being applied on long-term basis. Permanent grasslands are dynamic associations, where stabilization occurs after long-term application of applied treatments. These experiments have higher testifying value then the short term

(1)

is also necessary to determine the amount of energy contained in biomass.

burned down is counted using the following formula (1):

Q1 – Extraneous energy from combustion of the cotton thread (J)

reduced by weight of ashes after burning down).

conditions (Long, 1934) and on other parameters.

The number of energetic balances when growing plants etc.

*CTQ* . -1 *<sup>Q</sup>*

Q – Gross calorific value of the sample (J g-1) C – Heat capacity of the calorimeter system (J K-1)

m – Mass of the sample (g)

ones.

**4.1 Calorific value** 


Permanent grasslands are able to fulfil these and other functions, provided that correct management is applied. Underutilized and neglected permanent grasslands are able to maintain these functions only in limited amount, or they can even contribute negatively in those areas, according many literal sources (Hopkins & Holz, 2006; Rychnovská, 1993; Rychnovská & Parente, 1997). Absence of regular utilization and grassland management cause degradation to fallow, and consequently, establishment of high number pioneer shrubs and trees. Planning of grassland management is necessary to conserve total diversity and retain its important functions in landscape (Moog et al., 2002).

Maintains of present status of grasslands and introduction of agro-environmental programs and agreements is one of the solution for sustainable development, it means the optimal and environmentally friendly utilization of nature resources like soil, water, plants and animals communities (Stypiński et al., 2009).
