Contents
    Summary
    Chapter One
    Chapter Two
    Chapter Four
    Chapter Five
    Chapter Six
    Chapter Seven
    Chapter Eight
    Chapter Nine
    Chapter Ten
    Appendices  
    Foot Notes    

A project facilitated by the Research and Development Group of the Bio Dynamic Farming and Gardening Association

3 Organic Dairy Pasture Systems – A Review

Introduction

The following report summarizes the findings of a literature review searching information on the effects organic manage-ment has on dairy pastures.

Germany and Switzerland in particular have a long history of biodynamic and organic production and research. Long-term farm trials and soils managed biodynamically for up to 70 years are available for research. Many institutes and universities are involved in research into organic production systems and some are dedicated solely to this field.

Most of the research reported on, however, has been undertaken on soil used for vegetable production, cropping or orchards, but not under permanent pasture. In European production systems, pasture provides only part of an animal’s diet; feed production for livestock is managed by a rotation of pasture and different fodder crops. Dairy cows are housed for most of the year, and are grazed only for brief periods; stocking rates are low and regulated to minimize surface and groundwater contamination. While the stocking rate in New Zealand varies mainly between 2 and 4 cows per hectare, depending on regional production potential and intensity of the farm management, Essen et al., (1990) report on biodynamic milk production in Sweden, where the researched dairy farm consisted of 100 ha and 40 dairy cows. This difference in production system is reflected in the research. Many fertilizer trials include different application rates of slurry and manure, researching the effects of different ways and periods of composting for slurry and manure and the effects of added biodynamic preparations. A main aim of the research is to identify production systems that minimize surface and ground water contamination with livestock production (Elsasser, 1995).

Soils Under Pasture

General

The literature included in this section summarizes findings of a general nature; although not all the research reported on is aimed specifically at dairy pasture, the findings on the effects of organic management on soil characteristics encompass all areas of agricultural production and are therefore also applicable to organic pasture management.

Production Potential and Product Quality

The emphasis of organic soil management is on maintaining the long-term production potential of the different production systems, rather than the short-term production increase of a particular crop. The following trials confirm the effectiveness of this approach:

The application of biodynamic preparations showed a positive effect after a relatively short period. Perez-Sarmentero et al., (1999) assessed up to 16 soil parameters after 3.5 years of applying biodynamic preparations. Results suggest these preparations have a positive influence on soil conditions, the response being better in more extreme environments.

Granstedt et al., (1997) report on three long-term experiments in Sweden, researching the effects of fertilizers and manures on soil fertility, crop yield and quality. They found that yields of grass/clover mixtures were highest in the organic treatments, and most chemical and biological parameters of soil fertility were increased by organic fertilization.

Raupp et al., (1997) evaluated the relative yield, product quality and soil life after long-term (17 years) organic or mineral fertilization. They found that production yields varied: yields of potatoes and rye were lower and yields of spring wheat were similar in the organic system. However, their evaluation also showed that humus content and biological activity in the soil were greater, that products from the organic system had a better storage quality and that vegetables had lower nitrate contents.

Apart from the quality of the product from different production systems, the production potential of organic in comparison with conventional production systems is important. Research findings seem contradictory as production yields are found to be lower (Raupp, 1997; Reganold, 1995), equivalent (Raupp, 1997), or higher (Granstedt, 1997; Colmenares et al, 1999). Simulating the production potential after long term differing management systems showed the following: Droogers et al., (1996) compared the production potential of two farming systems (biodynamic and conventional) by converting ‘static’ basic soil properties into a ‘dynamic’ assessment using simulation modelling. Soil conditions on two farms – one having been managed biodynamically for 70 years – were investigated with morphological and physical methods. A simulation model including 30 years climatic data was used to predict water-limited potato yields, showing that the simulated yields were significantly higher on the biodynamic fields.

Rhizosphere – Interaction with Plant Growth

No published research was identified in New Zealand on this topic. The international work published emphasized the influence that soil flora and fauna have on plant growth in an organic system. Scullion et al., (1998), for example, described how management before conversion can have an impact on soil fungi, that in turn will influence plant growth under the organic system. Yeates et al., (1997) described soil microbe and faunal diversity in Welsh soils, and while the soil types may differ, the message to enhance diversity is the same. This paper also described indicators that could be used to define soil "health" in an organic system. Eason et al., (1999) and Cook et al., (1995) both described how management can impact on soil microbe and fungi populations and how this in turn can influence plant growth.

Trace Elements

Condron et al., (2000) presented a comparison of soil quality under conventional and organic management in New Zealand. One area of focus in the paper was on trace elements in soils under organic and conventional pasture and their effects on animal health. Trace element impacts on animal health were also mentioned in some of the more generic animal health papers described earlier. Other than this work, there was very little information on trace elements in soils under organic pastures.

Microbial Activities and Biomass

Synthetic water soluble fertilizers are known to be detrimental to soil microorganisms and therefore to influence biological and physical soil characteristics negatively in the long term. Mader et al., (1995) studied the effect different fertilization intensities on different crops have on soil microorganisms at different soil depths. They compared organic and conventional farming systems in Switzerland and reported that soil microbial biomass was significantly higher under the biodynamic system. Wood (1995) reported on studies in the UK, that showed an increase in earthworm populations with additions of manure; and comparisons of conventional and biodynamic farms in New Zealand showed that the biodynamically farmed soils had better structure, lower bulk density, higher organic matter content and respiration rates, and higher earthworm populations.

Pfiffner et al., (1996) described a long-term trial (running since 1978) studying the effect of different farming systems (biodynamic, organic and conventional) on ground beetles. The number of species was consistently higher (193 %) in the biodynamic than in the conventional (100%) and organic (188%) plots. The number of species differed from 18–24 in biodynamic plots, compared to 19–22 in organic and 13–16 in conventional plots. In 1998 Pfiffner et al., (1998) reported on a long-term trial into the effect of different farming systems (biodynamic, organic and conventional) on earthworm populations. The earthworm biomass and density, and the number of juveniles and earthworm species were significantly higher in the biological than the conventional or organic plots.

Ryan (1999) reviewed studies with regard to the question ‘Is an enhanced soil biological community a consistent feature of alternative agricultural systems?’ Studies that examined four groups of soil organisms, comparing the soil biological community in conventional, organic and biodynamic management system were reviewed, and a case study of biodynamic and conventional dairy farms in Australia included. Ryan’s conclusion was that the enhanced soil community found on the biodynamic farms relative to conventional neighbours should not be considered as a definitive feature of alternative agricultural systems, but rather as an effect of the higher input of organic matter.

Lytton-Hitchins et al., (1994) came to the same conclusion after comparing the physical and chemical properties of biodynamically and conventionally managed pastures in NE Victoria, Australia. The more favourable properties found on the biodynamically managed soils are attributed to decreased grazing pressure, longer intervals between irrigations, reduced tractor traffic and intermittent applications of compost and hornmanure preparations.

Ryan et al., undertook a glasshouse experiment with soil samples from 3 biodynamic (without conventional fertilizers for 17 years) and conventional (regular inputs of soluble P and N fertilizers) dairy pastures. Plant nutrient uptake was examined by assessing the response of white clover, perennial rye grass and indigenous VAM fungi to the addition of 4 levels of soluble P and N. Their findings indicated that the soils had not developed substantially different processes to enhance plant nutrient uptake. The experiments did not examine the response of plant nutrient uptake to non-water-soluble fertilizer, which might have produced different results.

Oberson et al., (1995) studied the role of microbiological processes in organic P transformations in soils under conventional and organic (biological) farming systems during the 13^th and 14^th year of different cropping systems in the DOC (bio-Dynamic, bio-Organic, Conventional) long-term field experiments at Thervil, Switzerland. They found that soil ATP content was higher under the biological systems, resulting in greater amounts of P held in the microbial biomass. The activity of acid soil phosphatase was higher in biologically cultivated plots, indicating an increased potential to mineralize organically bound P in these soils. Organically bound P, especially the pool of microbial P, was greater in biologically than in conventionally cultivated soils.

Reganold et al., (1995) summarize from various studies that biodynamic farming systems generally had better soil quality and, despite lower crop yields in comparison with their conventional counterparts, were just as economically viable on a per-hectare basis.

Organic Pasture Systems

Pastures

Compared with crop production systems, there is very little information available on organic pastures for dairy production. This is primarily due to the intensive, housed nature of animal production systems in Europe, where the majority of organic research is undertaken. There is, however, increased interest in the use of pasture as a feed source, particularly in the United Kingdom. Topics identified in the literature under the heading of organic pastures included composition, herbal leys, nutrient management, grazing management, fertilization, legume content and grassland management before conversion. New Zealand has a wealth of information on conventional pasture management and many of the theories behind this are applicable to organic systems. What is lacking in New Zealand is specific research on organic pasture systems and the effect that organic practices will have on pasture production, quality and composition and interactions with other components of the systems (e.g., animals, soils).

Permanent Pasture Composition

There has been no published research carried out in New Zealand on the composition of pastures under organic management. Some research from overseas are applicable in New Zealand, however. A key factor highlighted in this literature is the use of legumes in pastures as a source of nitrogen. A difference between New Zealand and many European systems is that in Europe ryegrass/white clover leys are considered a fertility-building crop rather than permanent pastures. Le Gall et al., (1997) described typical pastures in France under organic dairy/beef grazing and how to maintain desired sward composition. The pastures described in this paper are very similar to New Zealand pastures, and the information is therefore transferable. Frieben (1997) highlighted the impact that pre-conversion fertilization has on pasture composition under the organic system. Studying the stand composition and species diversity on permanent pastures on 7 organic farms in Germany and comparing these with conventionally managed grasslands, she found the number of species in organic grassland was greater than in conventional grassland. Cook et al., (1995) described soil biodiversity and its interaction with grassland management, emphasizing the importance of balancing the whole system. In key research, van Elsen (2000) emphasized the importance of species diversity, in an organic farming system. Plant species diversity, genetic diversity within species, insect diversity and animal diversity are all important for an organic system to function efficiently. Padel et al., (2000) reported on forage field measurements undertaken during conversion of dairy farms to organic production in the UK. Herbage growth fell by 15% during the first year of conversion, but by year 3 had recovered to 93% of pre-conversion values. The white clover content of the herbage increased substantially throughout transition, from less than 5% to over 30% by year 3. Colmenares et al., (1999) observed the effects of the application of biodynamic preparations over a 3.5-year period on permanent grassland in Spain. The results indicated that the biodynamic preparations enhanced production and dry matter content.

Leys

In international literature there is much discussion on the use of leys, which are more often than not ryegrass/white clover swards incorporated into a crop rotation. The main purpose of these leys is to increase soil fertility. Petterson et al., (1998) collected samples of grass and clover swards from leys during one season on different Swedish farms converting to organic farming, to obtain a survey of general practical differences in the botanical and chemical composition of leys during such a conversion. The main difference of practical importance was a significantly higher percentage of clover in organically grown leys, and differences in botanical composition and with harvest times.

There is less discussion, however, about herbal leys, which are typically made up of a diverse range of species. Foster, (1988) published a key paper on this topic. It described research carried out on herbal pastures from 1850 to 1984. While this paper does not specifically discuss organic systems, much of the research described was carried out pre-synthetic fertiliser, and can therefore be applied to the organic system. Foster’s paper described species and their specific attributes, different mixes commonly used, management, dry matter production and animal production from herbal pastures. The main body of work carried out in New Zealand on herbal leys was not under organic management as such, but under conditions of nil synthetic fertiliser and herbicide/pesticide application. Ruiz-Jerez et al., (1991) described an experiment comparing production from a herbal ley sward with a low N and a high N ryegrass/white clover sward. This is a key paper on/for herbal ley production in New Zealand. Two subsequent papers (Ruiz-Jerez et al., 1995 and Ruiz-Jerez et al., 1994) described the nitrate leaching and denitrification, respectively, from the experiment discussed in Ruiz-Jerez et al., (1991).

Pasture and Grazing Management

Most of the conventional research carried out in New Zealand over the last 50 years on grazing management in particular would be applicable to organic pastoral systems. The key factor in a pastoral system is to utilise as fully as possible all pasture grown so that it can be converted into milk, regardless of whether a system is under conventional or organic management. Most of the international research on organic pasture/grazing management has been undertaken in the United Kingdom, with the Institute of Grassland and Environmental Research (IGER) being particularly active in this area. Stickland (1988) covered the topic of grassland management in an organic system and described species common in New Zealand. Watson and Philips (1997) looked at environmentally responsible management of grassland to avoid such problems as N leaching and erosion. Eriksen et al., (1999) looked at N leaching that can be caused when permanent pastures are ploughed up, and Conacher and Conacher (1998) identified management practices that can prevent some of the negatives of organic farming, such as mining of soil nutrients and elements.

Pest and Disease Management

While there is a vast amount of international research describing the specific treatment of a pest/disease, particularly in cropping systems, there was not much research (and no New Zealand research) dealing with pastures. A few generic papers have been identified that describe the importance of functional diversity in preventing pest and disease infestation of plant communities (including pastures and fodder crops). Finckh et al., (2000) discussed why pests and disease are likely to occur and the management of their prevention. La Torre & Donnarumma, (1999) emphasized the importance of prevention in organic systems, and Hopkins & Feber, (1999) described the technique of maintaining a high pest predator population in field margins, again emphasizing the importance of biodiversity.

Weed Management

An abundance of international literature was identified dealing with weed management in organic cropping systems. There was very little (and again no New Zealand specific research) particularly targeted at pastoral systems. A number of generic organic weed control papers have been identified (Leake, 2000; Christensen et al., 1999; Rasmussen & Ascard, 1994; Marshall, 1992; Stopes & Millington, 1991; Patriquin, 1988) that include methods such as tillage, timing of operations, sowing rates, cultivar selection, mulching, livestock grazing, composting, flame weeding and allelopathy for control of weeds.

Animal Management and Health

There is a huge range of international literature in the area of animal management and health; however, it is not targeted specifically at pastoral systems but rather all organic dairy production systems. Again, no New Zealand-specific research was identified. The focus of much of the research was the use of management practices to maintain good animal health, and most of these good management techniques would be directly applicable to New Zealand pastoral dairy systems. Topics included dairy cow fertility (Reksen et al., 2000; Augstburger et al., 1988), mastitis (Hovi & Roderick, 2000; Olesen, 1996), animal nutrition (Ebbesvik, 1993), rearing of young stock, parasite control (UK Organic Livestock Research Group, 2000; Younie, 2000; Krutzinna et al., 1996) and general papers covering animal health and husbandry. The paper by Sundrum (2001) was a key paper as it critically reviewed literature on animal health, welfare and organic product quality. Various publications confirmed that animal health, represented by expenditure on veterinary costs or incidences of diseases, is generally significantly better on organic farms than on conventional farms (Perellin et al., 1998; Olesen, 1996; Weller, 1996; Ebbesvik, 1994). Offerhaus et al., (1993) and Ebbesvik, (1993) reported on better fertility on organically-managed dairy farms.

Farm Management

Most of the papers described in earlier sections contain information on management of organic farm systems that may be useful to those converted or converting to organics. Austria Bundesanstalt fur alpenlandische Landwirtschaft Gumpenstein (2000) discusses managing high yielding cows and the effect of grassland management on milk production. MacNaeidhe (1992) and Younie et al., (1988) looked at management problems when converting to organics, Anon (2000) focused on whole-farm system management, and Disenhaus et al., (1999) looked at the role of extension in assisting managers. Again, there was no published research on this topic specific to New Zealand.

Milk Production Potential

There was no published research undertaken in New Zealand on organic dairy production potentials, and it was very difficult to find any data relating to organic production potentials that could be directly transferred into the New Zealand situation. Organic farming systems in Europe tend to have much larger animals that are fed high energy concentrate diets and therefore have greater yield than New Zealand animals. Milk production levels from organic systems compared with conventional were varied. In Pabst, (1994) and Weber et al., (1993) milk yield was lower on organic farms but in Jonsson (1996) was slightly higher. These contrasting results emphasize the overriding importance of good farm management on organic farm production potential.

Wider Environmental Issues

With farm management, it is important to consider the impact of any agricultural system on the environment and this is particularly so under the organic philosophy of farming. Several research articles were identified dealing with the issue of organic production and its relationship with the environment. Eriksen et al., (1999), Ruiz-Jerez et al., (1995), Ruiz-Jerez et al., (1994) and Watson et al., (1989) looked at the denitrification and nitrogen leaching that can occur from permanent pastures and herbal leys. Watson and Philips (1997) described environmentally responsible grassland management techniques, and Cederberg (1998) described key environmental differences between an organic and conventional milk production system.

Recommendations

The following questions, in relation to the New Zealand system of farming, are not answered by the current literature. Research in these areas needs to be undertaken for pastoral organic dairy farming to be economically, environmentally and socially sustainable in New Zealand.

• Soil quality under organic pasture management: Does organic management positively influence physical soil characteristics long term, e.g., the water-holding capacity of the soil in times of drought, or reduction of the damage occurring through animal treading on pasture in wet conditions?
• Pasture composition: Will pasture quality change under organic management? How? What composition dynamics are likely to occur during the conversion phase when conventional fertilisers are removed?
• Herbal leys: What is their value in New Zealand systems as an alternative forage (during drought, etc.)? What is their potential from an animal health perspective?
• Pasture/Soil Interactions: What are the key relationships? How is a healthy soil developed and maintained under intensive grazing pressure? How do soil/plant and animal interact? What is the role of trace elements in pasture production and animal health?
• Pasture systems: How much is actually grown in an organic system? How do organic dairy pastures need to be managed? Are grazing management techniques the same as on a conventional farm? How can a pasture system be managed so that it has minimal impact on the environment? How are pests, diseases and weeds specific to New Zealand controlled?
• Animal health: How do organic farms need to be managed to prevent diseases common in a pasture-based dairy production systems?
• Effluent: What are the effects of organic farm management on the wider environment? Does organic management with no input of water-soluble fertilizer and decreased stocking rates reduce the amount of detrimental nutrient leaching into surface and ground water?
• Evaluating the literature on research undertaken in Europe on the different treatments of slurry and the methods and timing of its application onto pasture – are some of these research findings applicable to New Zealand conditions?

These are a few of the questions that need to be answered, first to give farmers the confidence to convert to organic dairy production, and second to enable them to farm successfully and in a sustainable manner.

References

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