III. Early Proponents of Soil Health Concepts

12



J. W. DORAN E T AL.



soil that we generally allude when we speak of a farm as good or bad’ (after

Storr-Best, 1912, p. 28).

Maintaining a fertile soil, then, was of paramount importance to the philosophers. Practices suggested to maintain soil fertility included the use of rotations

that incorporated green-manuring or legume crops, application of livestock manure to soil, and fallowing. The Georgics of Virgil, translated by Lewis (1940),

outlined numerous methods for maintaining soil fertility. Regarding crop rotation

and fallowing, Virgil wrote: “So too are the fields rested by a rotation of crops,

and unploughed land in the meanwhile promises to repay you” (Book 1, I. 8283). On using livestock manure, he noted: “Whatever plantations you’re setting

down on your land, spread rich dung and be careful to cover with plenty of earth”

(Book 11, 1. 346-347).

Sensitivity to soil characteristics was evident in the cropping practices advocated by the philosophers. Cropping to the character of the land was the rule, not

the exception. This belief was expressed by Varro when he wrote: . . . the

same soil is not equally suited for all kinds of produce . . . for it is better to plant

crops that do not need much nutriment on thinner soil” (after Storr-Best, 1912,

p. 28, 63). Cropping to specific soils was suggested by both Cat0 and Varro.

Cato, in De Agriculturu, wrote: “Where the soil is rich and fertile, without

shade, there the corn-land ought to be. Where the land lies low, plant rape,

millet, and panic grass” (after Harrison, 1913, p. 42).

Using senses of sight, taste, touch, and smell, the philosophers set down

qualitative guidelines for evaluating soil and its suitability to promote growth of

particular crops. Soil color was used often in their treatises as an indicator of

productivity, with black soils considered the most productive and suitable for

corn production. Saline or acid soils were identified by a simple taste test recommended by Virgil: “The taste of fresh water strained through sour soil will twist

awry the taster’s face” (after Lewis, 1940, Book 11, 1. 246-247). The soil’s

physical condition was considered an important component for successful crop

production. In his classification of farmland, Varro found crumbling soils of

medium texture to be ideal for farming: . . . the kind of land which will repay

cultivation . , . easily crumbles when dug, and neither resembles ashes in texture, nor is very heavy” (after Storr-Best, 1912, p. 36). Similarly, Columella

classified “rich and mellow” soils best for crops and pasture (after Simonson,

1968). Pliny used his sense of smell to test soil. He considered the musty odor of

freshly plowed soil to be the most telling assessment of a soil’s quality: “It is the

odor which the earth, when turned up, ought to emit, and when once found, can

never deceive any person: and this will be found the best criterion for judging the

quality of the soil’’ (after Harrison, 1913, p. 91). Interestingly, this same criterion

is currently being considered by the USDA National Soil Tilth Laboratory for use

as a potential indicator of soil health (T. Parkin, 1995, personal communication).

”



”



SOIL HEALTH AND SUSTAINABILITY



B.



l ! h H AND



20TH



13



C E N T U R Y SCIENTISTS AND PRACTITIONERS



The nineteenth century brought widespread concern over a potential food

crisis caused by a rapid increase in human population. As the need to increase

food production was apparent, chemists sought to understand better relationships

between soils and plants. Initial work focused on the concept that plants fed

directly on soil humus. This theory, put forth by Wallerius in the middle of the

eighteenth century, was developed further during the first half of the nineteenth

century by Thaer and von Wullfen (Usher, 1923). They believed organic matter

in soils had to be kept at or near original levels to maintain fertility and avoid

reductions in crop yield. Humus, therefore, was considered a primary indicator

of soil quality. Research by these scientists indicated levels of soil humus to

decrease under cultivation. This finding resulted in predictions that, without

additions of organic matter, soils in central Europe would quickly be exhausted

causing significant declines in crop yield (Usher, 1923).

The humus concept, though profoundly important for its time, was considered

simplistic and limited in scope because of its theoretical basis in phlogiston

chemistry (Krohn and Schafer, 1983). Among its foremost critics was Justus von

Liebig. Liebig acknowledged the importance of hunius as a critical component of

soil fertility, but claimed that a number of key elements were essential for plant

nutrition instead. Relying on methodological advances in organic elementary

analysis, Liebig found plant nutrient requirements could be estimated by analyzing the elemental concentrations in plants and soils and striking a balance between the amounts in the soil and those in the growing plant.

Liebig’s thesis centered on the concept that maintenance of soil quality for

growth of plants required the establishment of natural, unbroken cycles of essential plant nutrients within the soil. These cycles, however, were perceived as

nonexistent in agricultural practices of the time. According to Liebig, the nutritionally extractive characteristics of agriculture could only be offset by addition

of essential plant nutrients to the soil in the form of artificial fertilizers. By doing

this, producers could claim to develop a nonexploitative relation to nature “like a

wave motion within a cycle” (Liebig, 1862, after Krohn and Schafer, 1983).

This new paradigm of plant nutrition caught on rapidly and by the turn of the

twentieth century, agriculture had evolved into a major production industry.

Under this method of agriculture, soil had acquired the status of a “nutrient bin”

for plant roots (Simonson, 1968). In opposition to this form of agriculture was a

group of scientists and farmers of “privilege” who regarded soil as a living

resource. Sir Albert Howard, J. I. Rodale, Lady Eve Balfour, and William

Albrecht represented a handful of individuals who believed soil vitality (i.e., soil

life) to be a fundamental component of successful and socially responsible agriculture. By their standard, soil was a form of biological capital: capital that could



14



J. W. DORAN E T AL.



be used wisely by adoption of agricultural practices that relied on balanced

natural fertility, or unwisely through continued use of practices that relied on external inputs of artificial fertility. They accordingly held the view that the health

and prosperity of society depended upon the condition of the soil.

Agricultural systems that promoted soil vitality were strongly advocated by

this group. In their view, soil vitality was achieved by maintaining a balance of

growth and decay in the soil. This balance was considered to be absent in

conventional agricultural systems as a result of a disproportionate emphasis on

production (Howard, 1943). Sustainable agricultural systems were regarded as

balanced by relying upon vast natural reserves of decaying material. In terms of

agricultural management, this implied replenishing organic and mineral matter in

the soil.

Application of compost to soil was generally accepted as the primary method

to maintain soil organic matter. J. I. Rodale, in Pay Dirt (1945), outlined 36

advantages of using compost, 15 of which were directly related to improving soil

health. Rodale strongly believed the value of compost could not be estimated by

chemical composition alone. In his view, the greatest value of compost was in its

potential to improve the biological and physical condition of the soil.

Although emphasized less than organic matter application, addition of mineral

constituents to the soil was encouraged. Howard regarded the success of Hunzan

agriculture to be partly due to the silt-size glacial material found in the irrigation

water (Howard, 1947, p. 177). Albrecht and Rodale both stressed the importance

of renewing the soil mineral fraction by suggesting the application of lime, wood

ash, and even rocks to soil.

Primary to the philosophy of this group was the belief that soil quality impacted plant, animal, and human health. Diet was considered to be the primary

determinant of good health, and nutrition for all terrestrial organisms began

“from the ground up” (Albrecht, 1975). So strong was this belief that they

claimed soil quality to be an important element of public health. Lady Eve

Balfour, in The Living Soil (1948), declared issues of soil management and

public health to be inseparable. In fact, she proposed that agriculture should be

looked upon as one of the health services, if not the primary health service.

Attainment of this status, however, depended on the need to clearly identify a

relationship between soil quality and public health using rigorous scientific methods; a difficult or impossible task.



IV. SOIL HEALTH AND HUMAN HEALTH

For much of modern agricultural history, the value of new farming techniques

and products was judged primarily, if not solely, on their ability to increase food



SOIL HEALTH AND SUSTAINABILITY



IS



production. As discussed earlier, warnings of potential environmental damage

associated with modem agriculture were largely unheeded until recent decades.

The concept that the method of food production can have an additional direct

impact on animal and human health has recently developed, but only tentatively

in scientific circles. The proposal that any definition of soil quality or soil health

needs to incorporate the soil’s effect on human health as a component of equal

importance with productivity and environmental impact was perhaps first publicly articulated at the Conference on Assessment and Monitoring of Soil Quality

held at the Rodale Institute, Emmaus, Pennsylvania in July, 1991 (Papendick and

Parr, 1992; Rodale, 1991). Little headway has been made since then in defining

the indicators of soil quality and associated effects on human health.



A. DIRECT

AND INDIRECTEFFECTS

There are three general avenues through which the soil may interact with and

affect the health of higher animals. First, there is the potential for direct poisoning of animals and people from contaminated soils. This is most likely to be

highly localized and may be the result of industrial accidents or improper use or

disposal of agrochemicals, industrial chemicals, or radioactive waste products.

While the seriousness of such toxic encounters with the soil is not to be taken

lightly, the likelihood of the general population being exposed to soils so highly

contaminated as to seriously affect health is very small, There are numerous

well-documented occurrences of pesticide poisoning (Hodges and Scofield,

1983; Culliney et al., 1992), but most acute farm chemical poisonings occur

before the chemicals are applied to the soil, generally during mixing, or during

the spray process itself when chemicals are air-borne (Soule and Piper, 1992;

NCAMP, 1990). Recent dramatic increases in certain fungal diseases, often

fatal, seen in patients suffering from immunodeficiency diseases such as AIDS

can be traced to soil origins (Sternberg, 1994). Although naturally occurring, and

not normally associated with unhealthy soil conditions, it appears that soil disturbances, whether natural, as from earthquakes, or human initiated, create the

conditions necessary for the spores to be propelled into the atmosphere in numbers sufficiently high to infect the human population.

A second, more widespread degree of interaction between soil health and

animal/human health occurs indirectly, through the soil’s influence on the quality

of water and air. It is well-recognized that there are serious public health concerns related to contaminated groundwater, streams, and other surface water

supplies, occasionally including acute toxicity, but more often associated with

development of cancer and other long-term debilitating diseases. Nitrate in

drinking water can cause the potentially fatal methemoglobinemia, or blue baby

syndrome, but can also have more insidious carcinogenic effects if transformed