Pesticides

Mainly comprised of plant protection products and biocidal products, pesticides are designed to influence fundamental processes in living organisms. They may have the potential to kill or control harmful organisms such as pests, but can also cause unwanted adverse effects on non-target organisms, human health and the environment (EC 2007). Both the hazards and benefits of pesticides are well documented in published literature and have been reviewed most recently by Cooper and Dobson (2007).

Focussing on pesticide life cycles, there is so far only little information available regarding, e.g. the temporary storage of pesticides at farm level, the management and calibration of application equipment, the protection of operators, the preparation of the spraying solution and the actual application (EC 2007). In order to find a connection between crop and pesticide inputs, a survey based on randomly selected farmers in different agricultural soil-climate regions was conducted in Germany. For the main field crops, detailed information on the real use of chemical plant protection agents in agricultural practice was collected and evaluated (Table 5.5).

Although the results presented only reflect agricultural practices of a single year, findings confirm that herbicides are the most widely used type of pesticide, as weeds are the major constraint that limit yield in many crops in conventional crop cultivation systems. According to CropLife (2004), herbicides represent around 50% of all crop protection chemicals used throughout the world, compared with insecticides and fungicides that each account for around 17%.

In view of the major influence of weeds on yield in conventional cultivation systems, Karpenstein-Machan (2000) investigated the effect of low-input energy crop rotations in cereals (rye, triticale and barley). Considering thermal conversion, grain yield and total biomass yield (crop and weeds) in non-pesticide variants were compared with conventional pesticide programmes. Total biomass yields increased no more than 5%, whereas grain yields showed approximately 16% higher values, rye being clearly the most competitive crop after herbicide application. Consequently, in arable energy crop systems, it is possible to reduce herbicide application, as weeds contribute to biomass as well.

These results may be transferable for SRC such as poplar and willow, but practical experience is still lacking. However, in short rotation plantations weed control is only indicated as an important factor during the establishment phase (Scholz et al. 2007; Walle et al. 2007).

Table 5.5 Application index of different pesticide groups and growth regulators used in Germany, calculated within the project Neptun 2000 (Ro├čberg et al. 2002)

Total chemical

Pesticides

Number

plant protection

Growth

Plant species

of farms

measures

Fungicides

Herbicides

Insecticides

regulators

Rape

644

3.41

0.68

1.18

1.44

0.12

Winter wheat

790

3.74

1.39

1.37

0.36

0.62

Winter rye

332

2.61

0.90

0.85

0.14

0.72

Triticale

319

2.26

0.46

0.96

0.09

0.74

Maize

489

1.24

0.00

1.22

0.03

0.00

Potato

130

8.56

6.08

1.55

0.94

0.00

Sugar beet

382

2.93

0.15

2.59

0.19

0.00

Application index: number of pesticides applied, related to the authorised application rate and the crop-specific cultivation area. For calculating the application index, each application of a pesticide is considered as a single application, irrespective of whether or not it is applied within a tank mixture. The data collection is related to the vegetation period 1999/2000, containing all chemical plant protection measures including seed protection and growth regulator applications. The data set is based on voluntary cooperation of randomly selected farmers in the various agricultural soil-climate regions of Germany.

Application index: number of pesticides applied, related to the authorised application rate and the crop-specific cultivation area. For calculating the application index, each application of a pesticide is considered as a single application, irrespective of whether or not it is applied within a tank mixture. The data collection is related to the vegetation period 1999/2000, containing all chemical plant protection measures including seed protection and growth regulator applications. The data set is based on voluntary cooperation of randomly selected farmers in the various agricultural soil-climate regions of Germany.

Up to now no negative effect of weeds has been observable as long as harvested biomass was regarded as feedstock for the thermal conversion process. Focusing on anaerobic digestion, first results reveal that biomass consisting of higher amounts of weeds leads to a reduction in methane yield (Heiermann et al. 2001, Hermann et al. 2007). For example, the methane yield of total biomass (crop and weeds) was reduced by up to 20% in comparison with pure crop (sorghum). Thus, to exploit the full methane formation potential, special attention must be paid to the impact of weeds in biogas crop cultivation.

5.5.3 Water

In recent years water availability has become an issue of global concern due to natural variability in water availability (rainfall) and changes in Europe's climate which indicate severe stresses on water resources. On average, 42% of the total water abstraction in Europe is used for agriculture. In south-western European countries, agriculture accounts for 50-70% of the total water abstraction (Freshwater Europe 2007). The role of irrigation differs between countries and regions due to climate conditions. While in Southern Europe irrigation is essential to secure agricultural production, in Central and Northern Europe irrigation is usually applied to maintain crop production in dry summers. Focusing on crop-specific irrigation, EEA (2005) reported that in Spain, Greece and France, grain maize is the most frequently irrigated crop, whereby in France 40% of the irrigated area is used for grain maize cultivation. Also a significant acreage of wheat, sunflowers and potatoes is irrigated in the southern parts of Europe (EEA 2007). Up to now, no data are available with respect to irrigated crops for bioenergy production. However, expansion in energy cropping associated with increasing water consumption will clearly stress water resources (Berndes 2002).

Under European conditions water requirements are typically in the range of 200-800 g water per gram dry matter (DM) produced (Table 5.6). Determined by genetic characteristics, water consumption of C4 crops is less than that of C3 crops, although a wide variation exists between the plant species due to certain photo-synthetic mechanisms.

To assess the response of crops to irrigation, the reciprocal of the transpiration coefficient, the WUE, is applied indicating total biomass produced (above-ground DM) per unit mass of water taken up by the crop during the whole growth cycle (Manoliadis 2001; Nova et al. 2007). For conventionally cultivated crops, WUE values of harvested whole crops range between 1 and 9 gDM kg-1 evapotranspiration water, increasing in the following order: oil crops (rape, sunflower), sugar/starch crops (wheat, rye as C3 cereals) and potato, sugar beet, maize (C4) and ligno-cellulosic crops such as M. sinensis (C4) (EEA 2007). The WUE values for whole crop cereals are higher because usually the index is related to grain yield, which is approximately 40% of the whole plant biomass.

Table 5.6 Transpiration coefficients for energy crops under European conditions according to Geisler (1988), Schweiger and Oster (1991), Larcher (1994), Jacks-Sterrenberg (1995) and Hartmann (2001)

Crop species

Crop type

Transpiration coefficient (g H2O gDM 1)

Rape

C3

600, .

.., 700

Sunflowera

C3

500, .

, 600

Wheat

C3

250, .

, 550

Rye

C3

400, .

, 500

Maize

C4

300, .

, 400

Potato

C3

400, .

, 500

Sugar beet

C3

350, .

, 450

Sorghum

C4

200, .

, 300

Miscanthus

C4

250, .

, 350

SRC (poplar, willow)

C3

600, .

.., 800

aUp to the flowering stage aUp to the flowering stage

Owing to increasing water demand and a decline in water availability, irrigation of energy crops is a very critical resource issue. In Germany, the first research project has started to evaluate the efficiency of irrigation with special emphasis on suitability of selected energy crop species for local conditions.

Organic Gardeners Composting

Organic Gardeners Composting

Have you always wanted to grow your own vegetables but didn't know what to do? Here are the best tips on how to become a true and envied organic gardner.

Get My Free Ebook


Post a comment