Dr. Uwe Hofmann
ECO-CONSULT International Consultancy of Organic Viticulture
e-mail: uhofman@netart-net.de

Introduction

The soil, like water, air and energy, is one of our most important resources. Our future living conditions will depend most fundamentally on how well we manage these nourishing resources. A serious endangerment of ecological soil vitality, caused by the effects of pollution and high external input management systems, can be confirmed at a global level. The development and application of ecologicaly appropriate soil and land management systems represents an urgent challenge and is imperative because it allows the long term-maintenance of ecological soil functions. Organic viticultural practice aims at increasing a location`s natural soil fertility. The soil fertility is induced by a positive combination of soil organisms, soil condition, humus supply, soil structure, water conservation and plant growth and its stabilisation.

Cover Crop Management

Temporary or permanent green cover crop as a replacement of crop rotation of the permanent culture vine and orchards should fulfill additional tasks of Organic Viticulture besides the well-know functions like prevention of erosion, ground cover, dimunition of ground pressure.

• Improvement of soil structure and water conservation by permanent root spreading.
• Nutrient supply for soil organisms (earthworms, microorganisms) as basis for high biological activity and for the availability of soil nutrients.
• Nutrient supply adapted to the growth of grapes by a specific mulching management and seeding of herbs and nitrogen fixing plants.
• Support and stabilisation of the fauna in the ecosystem vineyard (canopy and green cover) with a mowing, cutting or rolling treatment in every alternative row to enable the blossoming of green manuring plants.

A prerequisite for successful green cover is subsoiling. For the Organic Production it is important to achieve plain turning and deeper soiling at the same time. This can be done in conjunction with seeding. In order to eliminate the danger of water and nutrient competition under local climatic conditions it is necessary in the first years after conversion to have a temporary green cover in the winter and to cultivat before the new vegetation in the spring.

A post harvest of cover crop seeding or summer seeding, after completing pest and disease control treatments, makes more sense than a spring seeding. After mechanicallly loosening the soil and seeding, the ground won`t be compacted for a longer time (over winter). The seeded plants can build roots in the loosening soil and stabilise it. The growing plants do not compete for water and nutrients with the grape-vines and they may preserve surplus nutrients in autumn and winter.

As diversification of plants is essential (Boller et al. 1997, Hofmann 1994). Organic vine growing basically use a multispecies plant mixture. The choice of seed mixture depends on the duration of green cover (annual, perennial), soil conditions, texture, reaction pH, humus supply, season of the seeding as well as the management of mowing, cutting or rolling.

Regarding the composition of locally required mixture, it should be kept in mind that:

• The mixture should consist different nitrogen fixing plants (legumes), herbs, flowers and grasses.
• The selection of green cover plants should include slow and fast germinating seeds as well as medium and high growing plants.
• At least half of the plants should be deeply rooting.
• The mixture is linked to the time of agricultural use and location.
• The amount of seeding should be at the lower level so that local wild herbs can germinate and grow together with the green cover.

Apart from pure melioration mixtures (annual, frost sensitive greening, winter green cover, vetch mixture) Organic Viticulture uses perennial plants for green cover (Tab.1 and 2) (Hofmann et al. 1995).

Tabel 1. Example of perennial cover crop mixture for heavy clay soil

Tabel 2. Example of perennial cover crop mixture for dry sandy soil

Meloriation mixture (sum up to perennial mixture):

The perennial melioration mixture is composed of annual and perrenial plants. The advantages of this mixture are quick germination of the annual plants, covering of the ground, ramifying roots and the conservation of nutrients by building a high biomass a short time after seeding. The nitrogen preservation in autumn and the reduction of nutrient-loss in winter is necessary by ploughing up a perennial cover crop in spring and a soil cultivation management in summer, if there is a lot of nitrogen in the soil. A quick germinating green cover, oil radish, phacelia, backweath, russian and chickling vetch may preserve and fixe nitrogen in the biomass. After death of the winter annual cover crop and the beginning of mineralisation in early spring the fixed nutrients are available for growing plants like grapes or orchards.

Figure 1 shows the preservation of nitrogen (kg/ha) in produced biomass in autumn and winter. The large volume of material (450 dt/ha fresh-mass) of the melioration multi-species mixture preservate 170 kg nitrogen/ha in the dry-mass.

Fig. 1 : Nitrogen preservation in the cover crop biomass (kg N/ha) in autumn and winter 1990/91 in germany (Hofmann, 1995)

The multi-species cover crop mixture has extended and ramifyed root systems which make them particulary useful in building mellowness with stabil crumb structure and improving water conservation. Root systems provide passages through the soil, increasing intake. Cover crop residue helps maintain organic matter in the soil which, in turn, increases infiltration.

Fig. 2 shows soil samples (spate diagnosis) of the same soil:

The compacted situation on the beginnning of conversion and the loosened soil after three years of soil preparation and cover crop management. The loosened soil is stabilised by deep roots, microorganismens with high biological activity. The practice of the spate diagnosis, developed by J. G?bing (1947) is to dig a "soil-brick" with the so-called flat spate out of the field. The soil brick is immediately examined with references to the conditions of soil structure (loose, medium, dense, possible existance of compaction layers) and other parameters (moisture: dry, less wet, medium wet, wet). In support of this method the conditions of soil structure, size, shape and arrangement of soil particles and aggregates as well as density, root growth, microbial activity, rhizobium development and soil moisture can be examined with little effort.

With the organic matter present, earthworms inhabit the soil, mixing the soil and developing tunnel systems which also aid in water and root penetration.

Under the multi-species plant mixture , seeded in the organic systems, more earthworm individuals have been found than under the grass-clover mixture (Tab. 3).

Table 3 : Development of earthworm in different cover crop systems (number of individuals/0,5 qm) (Hofmann, 1993).

Another benefit of the diversificated cover crop is supporting and stabilising the insectfauna in the ecosystem vineyard which can be useful in pest control (Bugg & Waddington 1993; Wyss 1994; Altieri 2000; Costello & Daane 1998). A prerequisite for a support of the fauna is blosseming cover crops. This is why an alternating mow- and cut-treatment has developed in the practice of Organic vine-growing. For the reduction of water competition or, respectiveley, to keep the growth under it is advisable to roll it several times. To maintain the diversificated growth it is important to cut it on a level of 15-20 cm, because many of the seeded plants have a raised vegetationpoint, so that a short cut over a long period may lead to a poverished green cover where only weeds like grass can be succecful. Alternating cutting or rolling may have good effect.

Fig. 3 shows a multi-spezies cover crop system with flowering plants (wild herbs).

Table 4 shows the positve effects of these melioration mixtures in comparison with a grass-clover mixture to the benefical insect population (predators) in the green cover depending of the intensity of cutting or mulching. The multi-species green cover, seeded autumn1990, presented itself in full bloom at the time of monitoring in July 1991 and `92. One row with grass-clover has also not been mowed. Additionally trials were taken also in a mowed row next to it. Within the green cover more predators were found than within the mowed ones (Tab. 3). The highest population were situated within the organic varians. The most part of the monitored insects were taken parasitic wasps, pirat bugs, lacewings, spiders and ladybird beetles. Between 80 - 280 different parastic wasps existed in uncutted rows.

Tab. 4 : Development of predators in different cover crop systems (cutting, without cutting).

Fig. 4 shows some predators in action.

1. Orb- wesp spider in the cover crop
2. Predatory mite Thyplodromus pyri feeds on spider mite
3. Orius minutus, minute pirate bug, nymph attack red spider mite
4. Larva of lacewing attack berry moth- larva

Soil preparation

On the beginning of conversion from Conventional to Organic Viticuture it is necessary to make a soil preparation plan. The emphasis of soil preparation is on the maintenance and improvement of the natural fertility of the soil structure, as well as on encouraging microbiological and earthworm activity ( Tab. 3). This is achieved by cover crops (legumes and grass crops) mowing, mulching, green manuring, organic fertilizers and soil preparation. Fig. 5 shows an example of a soil preparation plan under the climatic conditions of New Zealand. The analysis of the soil (spate diagnosis) has found that it was a compact soil with low biological activity, water conservation and availability of soil nutrients. The ratio of calcium to magnesium is satisfactory and so is the level of potassium.

It is a heavy clay soil.

Fig. 5 Soil Preparation Plan for conversion to organic viticulture

OPEN ROW COVERED ROW

Phase 1

After harvest

loosening every row to 15 cm with a chisal plough

seeding in annual cover crops seeding in perennial cover crops

50 kg Barley, 20 kg Rape 30 kg clover mixed ,10 kg luzerne,

30 kg vicia sativa - vetch 5 kg esparcet, 5 kg perennial rye

Winter

humus supply with compost

early spring

rotary tilling (vertical spreder, first cut (15 ?20 cm) of green cover

vertical rotary tiller)

Sept.- April

mechanical soil cultivation rolling the permanent green cover to with disc harrow or plough blossom- and seed production

Phase 2

After harvest

loosening to 25 cm rolling the cover crops during winter

seeding in annual cover crops

30 kg Sweet lupins,

20 kg Medics, 10 kg Oil radish

Winter

humus supply with compost

1 t dolomite lime, rock powder for soil conditioning

early spring

rotary tilling first cut of green cover

Sept.- April

mechanical soil cultivation rolling the permanent green cover to mulching with straw blossom- and seed production

Phase 3

After harvest

subsoiling to 40 cm rolling or cutting the cover crops

seeding in perennial cover crops

Winter

humus supply with compost

early spring

first cut of green cover rotary tilling and loosening to 20cm

IV. Mechanical Under-Vine Weed Control

Apart from the crop management the inter-vine cultivation plays an important role in the suppression of undesired competitors by an accompanying flora. The industry today offers a large range of different systems for the mechanical under-vine treatment from which the field manager can choose the best procedure according to the vinery structure, soil, soil condition and slope of the vineyards. The machines used can be divided into:

1. Vine clearing ploughs with ridging and summer share, hilling and ploughing back share, hydraulic operated vineyard body with flat share and rotary tiller clearer.
2. Under-vine rotor mowers or under-vine clearer with rotating brushes.

The ridging and ploughing shares operate a good under-vine treatment in connection with a hydraulik operated vineyard body - only few must be done by hand. The hydraulic operated bodies are good for under-vine cultivation in summer. In order to achieve a good quality the soil should neither be too compact nor the plant population be too dense. The flat share, which also belongs to the group of vine clearing ploughs, is one of the most interesting agricultural implements for the under-vine treatment in green covered vineyards, because it can be exactly adjusted and works at a good speed due to a hydraulic or electrical driven sensing wheel system.

The under-vine rotor mowers are mainly used in vineyards with a full green cover. It is advantageous if the green cover under the vines can be preserved and therefore no soil slacking can result, especially on slopes.

A disadvantage is the slow working speed and that unwanted grass, quackgrass and creeping thistles are not eliminated. It is also possible to eliminate these plants by using stem brushes or rotating brushes.

Fig. 6. shows the use of a new rotating brusher.

Summary

In Organic Viticulture systems, the green cover accomplishes an important job. The conditions at the location, especially climate and soil, are to be considered. Deep loosing, good humus supply before seeding, flexible mulch- mow and roll management, including a terminating cultivation, are of particular significance and important preconditions. The competition among vines and green cover under the vines may be reduced temporarily by mechanical work.

References:

ALTIERI, M.A. (2000): Manipulating plant diversity to enhance biological control of insect pests in northern California organic vineyards. Abstract IFOAM 2000 Conference Basel

BOLLER, E.F.; GUT, D.; REMUND,U. (1997): Biodiversity in three tropic level of the vineyard Agro-Ecosystem in northern switzerland. Ecological studies Vol. 130; Dettner et al (eds) Vertical Food Web Interaction ?Springer Verlag Berlin, 299 ?318

BUGG, R.; WADDINNGTON, C. (1993): Managing cover crops to manage arthropode pests in orchards. (via Internet—Sustainable Agriculture Newsletter ?SAREP ?Davis)

CASTELLO, M.; DAANE,K.M. (1998): Influence of ground covers on vineyard predators and leafhoppers (via Internet ?Sustainable Agriculture Newsletter - SAREP ?Davis)

G?BING, J. (1947): Die Grundlagen der Gare im praktischen Ackerbau. Landbuch-Verlag Hannover

HOFMANN, U. (1993): Green cover crop managemennt and mechanical weeding in viticulture; Proceedings of the fourth International conference IFOAM- Non chemical weed control Djon, 375-378

HOFMANN, U. (1994):Cover Crop in organic viticulture, Das Deutsche Weinnmagazin 13 ?8

HOFMANN, U. (1995) : ?o-Weinbau ?Abschlussbericht ?er achtj?ige Versuche zur Umstellung auf ?ologischen Anbau am Beispiel Mariannenaue ?Hessisches Ministerium des Inneren und f? Landwirtschaft, Forsten und Naturschutz

HOFMANN, U.; K?FER, P.; WERNER, A. (1995): Organic viticulture, Ulmer Verlag Stuttgart

WYSS, E.(1995): The effects of weed strips on aphids and aphidophagous predators in an apple orchard. Entomologia Experimentalis et Applicata 75, 43 - 49