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Prepared by Tina Finesilver, B.Sc., R.D.
in collaboration with Prof. Timothy Johns and Prof. Stuart B. Hill
This report is based on a review of literature on the comparative quality of organically versus conventionally grown food. Copies of the materials reviewed in the study are stored at the Ecological Agriculture Projects office, Macdonald College.
1. High nitrogen application to plant foods can increase crude protein concentration but decrease the nutritional value of that protein. Because nitrogen from organic fertilizer sources is often released slowly and is therefore less readily available to plants than from chemical sources, conventional fertilizing practices could possibly result in higher crude protein content but poorer quality protein than organic practices. Sufficient data does not exist to support or reject this prediction.
2. The large number of variables affecting vitamin and mineral composition of plants have made it very difficult to draw conclusions on the effect of agricultural practices on these parameters of food quality.
3. There is considerable evidence from controlled experiments that some organic fertilizers result in lower nitrate concentrations in plants compared to conventional fertilization. It is probable that careful application of appropriate organic fertilizers could result in lower nitrate levels in vegetables than normally seen following conventional fertilization practices.
4. There is a positive correlation between dry matter and nutrient content, and a negative correlation between dry matter and nitrate content in plants. Therefore it is important that nutrient and nitrate levels are reported and compared on a fresh weight basis.
5. The ultimate test of the nutritional value of food is its ability to support health, growth, and reproduction over successive generations of animals or humans. Evidence for increased disease resistance, productivity, or fertility of animals feeding on organically grown fodder is largely anecdotal. Nonetheless, it is possible that carefully controlled studies might show real differences in the quality of organically versus conventionally grown foods.
6. The results in the scientific literature show no consistent pattern for sensory quality between organically and conventionally grown produce, although there is evidence that organically grown potatoes taste better than conventionally grown after a period of storage.
Peter Brenner, a Swiss journalist, wrote in a newspaper article (1973) that on average, organic produce contains 27-33 ~ more dry matter than conventionally grown produce (cited by Berlin, 1974). His sources of information, however, were not revealed. Most studies concerned with this issue have fauna organically grown food to be either higher than or not different from conventionally grown in dry matter content, with a small number of results showing them to be lower. The data in the literature are summarized in Table 1.
Nutrient and nitrate concentrations in plants are often expressed on a dry matter basis. However, non-significant differences between organically and conventionally grown foods on a dry matter basis may translate into significant differences on a fresh weight basis if there are (large enough) differences in the percent dry matter between the two types of products. This was exactly the case in a study comparing a number of organically and conventionally grown vegetables as purchased by consumers (Lairon et al, 1983). While there is a positive correlation between dry matter and nutrient content, that between dry matter and nitrate content is negative (Vogtmann et al, 1984). Thus, it is important that nutrient and nitrate levels are reported and compared on a fresh weight basis.
The influence of fertilization on protein production and quality has been studied by a number of researchers, with varying results. High N-application can increase crude protein concentration, but decrease the nutritional value of that protein. Although the specific proteins synthesized by a plant are determined by its genetic makeup, the rates at which the individual proteins are synthesized are influenced by the amount of nitrogen fertilizer (Schuphan, 1961). At high levels, proteins which accumulate have a lower content of essential amino acids. Thus there is a decrease in the proportion of essential amino acids and an increase in certain non-essential amino acids. For example, lysine and methionine the limiting essential amino acids in wheat and spinach respectively, decreased proportionately at increasing levels of nitrogen supply in studies by Schuphan.
Eppendorfer et al (1979) attribute the inverse relationship between N-content and the concentration in the crude protein of many amino acids to the effect of fertilizers on the concentration of free amino acids and amides. They showed that increasing N- fertilization (organic or inorganic) in potatoes resulted in increased total-N concentrations in dry matter, with concomitant decreased protein quality, expressed as essential amino acid index, chemical score, and biological value (BV) and net protein utilization (NPU) as measured in feeding experiments with rats. Similar results were reported by Syltie et al (1982) for wheat, and by others.
In contrast, Millard (1986) found that increasing nitrogen application from 0-250 kg N/ha not only raised nitrogen concentrations but also resulted in statistically significant increases in the amounts of essential amino acids provided by 100 grams of fresh potato tuber. The total N-concentrations of these potatoes were lower than those in the study by Eppendorfer et al (1979). Eppendorfer (1975) showed that increased crude protein levels in oats as a result of fertilization was not accompanied by a decrease in the biological value of the protein.
Because nitrogen from organic fertilizer sources is often released slowly and is therefore less readily available to plants than that from chemical sources, it might be predicted that conventional fertilizing practices would possibly result in a higher crude protein content but poorer quality protein than organic practices. There are some data to back this up, but unfortunately most studies showing higher crude protein concentration in conventionally grown produce neglected to test protein quality. In addition, other evidence has failed to reveal differences in crude protein between conventionally and organically grown plant foods.
A three year Swedish field study by Pettersson (1977) found significantly higher crude protein concentrations (% dry matter) in conventionally grown potatoes, spring wheat, and barley, corresponding with significantly lower EAA-indices in potatoes and wheat (not reported for barley). In coordinated and identical experiments, Dlouhy (1977) reported similar results but showed no statistical analysis.
As an average of all crops grown over a 12-year period, Schuphan (1974) reported 18 % higher relative protein (protein-N as % of total-N) for those fertilized organically, and an average of 23 % more methionine for organic potatoes and spinach at one harvest. However, the significance of these isolated results in terms of protein quality is impossible to assess.
Pettersson and Wistinghausen (1979) did not find a significant difference in crude protein for potatoes fertilized organically or chemically except at the highest of three NPK application levels over a 4 year rotation of a field plot study. Relative true protein was significantly higher in some of the three organic treatments compared to NPK, but the comparable NPK level showed no difference.
The following studies showed some differences in crude protein concentration between organically and conventionally grown plant foods, but none of them tested protein quality:
Eggert and Kahrmann (1984) found higher crude protein concentrations for dry beans under conventional soil management systems for four consecutive years, although results were not analyzed statistically.
In spinach and beetroot, poultry manure generally resulted in significantly lower total-N concentration (% dry weight) compared to the four inorganic fertilizers tested (Goh and Vityakon, 1986), due to the low availability of poultry manure nitrogen.
Peavy and Grieg (1972) reported higher total-N concentrations (% dry matter) in NPK fertilized spinach for the first and second of three crops grown over two years. At the cool temperatures required for spinach`.growth, the manure's nitrogen was released very slowly and therefore its availability was limited. Perhaps by the third crop, mineralized nitrogen had accumulated in the organic plots, thereby increasing the N supply.
Conventionally grown tomatoes were significantly higher in crude protein (fresh weight basis) for the first of two growing seasons, but no difference based on cultural practices was found for the second (Clarke and Merrow, 1979).
Barker (1975), comparing four different organic amendments to ammonium nitrate, found that only manure resulted in a significantly lower total-N concentration (% dry weight) in spinach; this corresponded to the availability of nitrogen from the various organic sources. Other studies have failed to show differences between organic and conventional methods either in controlled experiments or on working farms: Lairon et al. (1984) reported no differences in the protein (% fresh weight) or amino acid content of lettuce fertilized organically or conventionally in field plots.
Over a 6-year field study there were no differences detected in total-N or protein (fresh weight basis) in a number of vegetables or three varieties of apples (Reinken, 1986).
Nine pairs of matched organically and conventionally grown wheat samples showed no differences in crude protein on a fresh weight basis (Shier et al, 1984). However, a number of variables were not controlled, such as variety of wheat and planting date.
Lockeretz et al (1981) found no differences in crude protein for either wheat or soybeans raised on 14 matched pairs of organic and conventional farms in the western Corn Belt of the United States.
The results for maize reported by Lockeretz et al (1981) and by Wolfson and Shearer (1981) may point out an important issue. They found the crude protein concentration in conventionally grown maize to be significantly higher than that in organically grown maize. The amino acid composition (as % of grain protein) of the two types of maize differed: methionine, histidine threonine , and lysine were significantly higher in organically grown, while isoleucine, leucine, and phenylalanine were significantly higher in conventionally grown. (Some, but not all of these differences were similar to differences between N fertilized and unfertilized maize.) However, due to the significantly higher dry matter and crude protein yields of conventionally grown corn, the amino acid yield per unit area was significantly higher for all amino acids except methionine (no difference) on the conventional farms.
On the basis of a possible pattern of higher crude protein but lower protein quality in conventionally versus organically grown produce, the question arises: which will produce the greater effect on human health - the diminished quality of protein or the concomitant increased amount of crude protein?
Another of equal importance is: how does the possible decrease in protein quality affect the individual person, who eats the same quantity of food regardless of the yield of amino acids per unit area?
The conventional wisdom holds that fertilizers in general, either organic or inorganic, have little effect on the nutrient composition of a plant, particularly vitamin content. Rather, nutrients are believed to be influenced primarily by a plant's genetic makeup, its stage of maturity at harvest, and climatic conditions (dukes, 1977; A.D.A., 1975; Anon, 1974; Leverton, 1973; Stare, 1972; White, 1972). Fertilizers can, however, influence the mineral composition of plants.
The following studies support these conclusions:
1) The first study compared fertilizer treatments and did not fertilizers.
The 10-year field study at Michigan State University compared the composition of various feed crops grown on a depleted soil, and fertilized with either nitrogen alone to promote a yield response ("unfertilized"), or heavily NPK fertilized and limed; the crops' effect on the performance of dairy cows; and the nutritional quality of the cows' milk (Michigan State University, 1956).
The researchers concluded that climatic conditions had more influence on nutrient composition of crops than fertilization, as evidenced by yearly variations for protein, calcium, phosphorus potassium, and manganese. The study was restricted to a limited number of macronutrients and minerals, and vitamins were not tested. However, it did not compare inorganic to organic fertilizers.
Seasonal variations were seen for both fertilized and unfertilized crops, and phosphorus tended to be noticeably higher in fertilized and manganese in unfertilized crops. Statistical analysis of results should have been performed, but unfortunately were not. One of the crops, timothy, did respond to complete fertilization with increased levels of protein and minerals.
Although unfertilized and fertilized shelled corn were not different, unfertilized corn stalks were higher in manganese and iron. This shows that results can be different for different morphological parts of plants and emphasizes the importance of testing different morphological types depending on which organ of the plant is commonly eaten (Muller & Hippe, 1987; Swanson et al, 1940) -
Growth and milk production of cows fed from the unfertilized fields was not significantly different from those receiving fertilized feeds. There was little difference in the composition of the milks in four generations of cows, except for slightly higher manganese levels for the first lactations of first and second generation unfertilized-feed cows. Vitamin contents (niacin; pantothenic acid; vitamin A; carotene) were not different, except for higher riboflavin in fertilized 60-day milk and in unfertilized terminal milk.
While rumen micro-organisms can synthesize essential amino acids and vitamins, humans must obtain these in their diets. Because rumen digestion is different from human, results for cows should not be interpreted in terms of human nutrition.
There was no difference in the growth of weanling rats fed the two types of cows' milk over a 6-week period. However, a more stringent test of the nutritional value of the milk would have been to take the animals through at least one breeding cycle.
2) A field experiment compared plots which had received horse manure and/or mineral fertilizer for 25 years (Brands & Beeson, 1951). No significant differences were found for ascorbic acid or carotene in rye sampled on two different dates, for ascorbic acid in potatoes after 6 months' storage, or for iron or copper in potatoes. However, Linder (1973) suggests that horse manure is probably not a good fertilizer.
In the same study, pot trials comparing compost to NPK resulted in no significant differences in ascorbic acid or carotene for carrots, or in ascorbic acid for two harvests of beans. Small differences in ascorbic acid in potatoes were attributed to differences in maturity. A description of the compost was not provided, and as Linder (1973) points out, there are variations in the quality of different composts.
Other studies offer conclusions in variance from the general patterns listed above.
A number of studies that have specifically focused on differences in nutrient composition between organically and conventionally grown plants are listed in Tables 2 and 3. Only a few vitamins and minerals known to be of nutritional importance have been studied in order to judge nutritional quality of plant foods. Before chemical or micro-biologic means were developed, the big-assay method employing feeding tests on animals was the only procedure available for testing foods for their vitamin content.
Three of these early studies are summarized in Table 2.
Improvement in analytical methods over time has led to a number of comparisons of the vitamin and mineral composition of organically and conventionally grown foods. These studies are summarized in Table 3. It is difficult to point to a clear pattern, although the studies overall suggest that organically grown produce is higher in vitamin C. However, careful attention should be given to the comments included on each study.
In interpreting the data in Table 3 the issues of genetic composition and maturity at harvest must be carefully considered, as both relate to possible differences between organic and conventional practices. These are not necessarily controlled in the above studies. This is particularly an issue where comparisons are made between conventionally and organically grown produce collected directly from producers or post-shipment.
The variety of plant grown by conventional farmers is likely to be selected to maximize yields, for ease of harvesting. etc., and not on the basis of nutritional quality. Therefore, differences in choice of cultivar between the two systems might result in differences in nutritional quality.
Conventional produce is often harvested prior to peak maturity to allow for extended transportation and storage; organically grown food, if sold locally, is ripened before picking. Generally, vitamin content increases up to the ripe state (Linder. 1985). While some fruits will continue to ripen after picking, other fruits and most vegetables cannot ripen off the vine. Furthermore, the vitamin content in fruit ripened after harvest may vary from that of fruit ripened on the vine.
Differences in level of freshness because of differences in storage, transportation, and handling conditions between the two types of produce can also affect nutritional quality. For example, wilting (loss of moisture) is accompanied by loss of ascorbic acid, which is most rapid in the early stages of storage (Linder, 1985).
Nitrate levels in plants are determined by a number of factors, such as variety of plant, light intensity, climate, soil, and by the nitrogen supply. Nitrogen, specifically amount, availability during growth, and time of application to the plant, has been considered as the source of nitrate variability in most studies comparing organically versus conventionally grown produce. In many organic fertilizers, the organically-bound nitrogen is relatively insoluble and must be mineralized before it can be used by the plant. In contrast, the nitrogen in mineral fertilizers is soluble and in usable form as applied.
There is considerable evidence from controlled experiments that some organic fertilizers result in lower nitrate concentrations in plants compared to conventional fertilization. However, when conditions are as not carefully controlled, differences in nitrate levels between the two fertilization practices become less apparent, or the conclusions drawn less supportable.
The differences in nitrate concentrations described in the following controlled studies are based on differences in nitrogen availability between organic and inorganic fertilizers, but the influence of other variables is sometimes evident.
Barker (1975) found that only one of five organic fertilizers resulted in significantly lower nitrate concentration (dry matter basis) in spinach compared to mineral fertilizer, and this occurred for only one of the two cultivars tested. This reduction in nitrate was due to the low mineralization rate of cow manure as opposed to the other organic fertilizers , which are mineralized rapidly. When the average nitrate level for all five organic fertilizers is compared to ammonium nitrate across four levels of increasing N-application, it is significantly lower at one level only, due to the depressing effect of manure on the average organic value.
Controlled pot trials showed very little nitrate (% dry weight) in two spinach varieties treated with poultry manure. Nitrate did not increase at higher N-applications rates using the poultry manure as compared to three different inorganic fertilizers (Gob and Vityakon, 1986). Harwood (1982) reported similar results for celery cabbage fertilized with increasing levels of either chicken manure or ammonium nitrate, as did Vogtmann and Von Fragstein (1984, cited by Vogtmann and Biedermann, 1985) for head lettuce, although no details or statistical analysis were presented for either study. The fact that nitrate did not increase with increasing organic fertilization in these studies is explained by the low availability of nitrogen in poultry manure due to its slow mineralization. Lairon et al (1984) found significantly lower nitrate contents in butterhead lettuce fertilized with castor-oil seed cake compared to either ammonium nitrate or chilean nitrate of soda in a field plot trial, and although nitrate concentrations increased with increasing nitrogen application rates for the mineral fertilizers, they showed no response to the organic fertilization rate. Similarly, the addition of a vitrification inhibitor (N-Serve) to one of the mineral fertilizers tested by Goh and Vityakon (1986) led to less nitrate accumulation at higher levels of fertilization. Increasing N application did not consistently raise nitrate levels in beetroot for any of the fertilizers tested, and roots of both beetroot and spinach accumulated less nitrate than tops.
Organic manuring both with stable manure or Biodynamic compost lowered nitrate nitrogen in spinach by 51-99% below that of NPK, giving an average 93% reduction over three crops in plot trials using two types of soil (Schuphan, 1974). Stable manure is known to have a low N-content, which was also made evident by its poor yields in this study. However, actual nitrate concentrations were not specified, nor was statistical analysis performed.
Maga et al (1976) showed a reduction, though not significant, in the nitrate concentration (dry matter basis) of spinach fertilized with dried blood compared to ammonium sulfate at the higher of two levels of N-application in a 1-year field study. Again, this trend was due to the slow mineralization and availability of nitrogen from this particular undecomposed organic fertilizer source.
Significantly higher levels of nitrate were found in organically grown cabbage and leeks compared to NPK in a field plot study, owing to the higher amount of available nitrogen in these plots at the end of the growing period (Nilsson, 1979).
Potatoes from 11 ecological farms contained 1/2 the amount of nitrate (mg/liter potato juice) compared to those from 9 conventional farms using both organic and inorganic amendments (Fischer and Richter, 1986). After interviews of the farmers concerning their fertilizing practices, At was calculated that the nitrogen available to the potatoes was on average 93.8 kg N/ha on the ecological farms and 152.3 kg N/ha on the conventional. Based on this information alone, it could be predicted that the conventional potatoes would be higher in nitrates due to greater nitrogen availability. Although the authors state that the significant difference in nitrates was due solely to cultivation method, the two types of farms were not matched for variety of potato, soil, climate, sunshine, etc., all factors known to influence nitrate levels. Therefore it is impossible to evaluate what part of the difference in nitrates is attributable to fertilizer practices, including the difference in nitrogen availability.
Other experiments show that studies are not necessarily results seen in controlled obtained in the field.
In controlled pot and container trials for leeks, carrots, turnips, and kale, farm yard compost and brushwood compost resulted in significantly lower nitrate contents (fresh weight basis) than NPK applied at conventionally-recommended levels (Lairon et al, 1886). On the other hand, blood-meal, a source of readily available organic nitrogen, was not different from NPK. In field trials, NPK showed significantly higher levels in 5 of 8 cases. Even more variable results were found when biological and conventional crops from paired farms were compared, although the number of farm pairs sampled for each crop was inadequate to give a valid comparison. As well, the farms were not adequately matched having "comparable" rather than identical soils and varieties. Conventionally grown carrots (fall-winter crop) had significantly higher nitrate levels in 4 of 8 cases, while organically grown were higher in 3 of 8 cases; the nitrogen supplies for both types of carrots were equivalent. For potatoes, lettuce, and leeks, the nitrogen supply was greater on the conventional farms. Conventionally grown potatoes showed higher nitrate levels in 1 of 2 cases, and lettuce in 3 of 5 cases (spring-summer crops). Organically grown leeks (fall/winter crop) were higher in nitrate than conventionally grown for the 1 farm pair sampled.
Although the authors conclude from these four experiments that organic fertilizers could significantly reduce nitrates, taken together they suggest that results obtained in carefully controlled trials will not necessarily be verified when variables that affect nitrate levels, and their interactions, cannot be controlled.
Controlled pot and field plot trials, as well as 3-year field experiments with two spinach varieties, Swiss chard, and head lettuce resulted in significantly lower nitrate (dry matter basis) levels for vegetables grown organically than those having received equivalent or even lower levels of NPK, while one lettuce and both corn salad trials showed no difference at the same level of N-application (Vogtmann et al, 1984). An interesting finding was that, in a number of the spinach trials, compost fertilization actually lowered nitrate concentrations below those in the control (O-fertilizer). The mechanism was explained in this way: oxidative degradation products in the composted farm yard manure temporarily inhibited Vitrification. This was supported by the fact that increasing compost application had an even greater effect.
Results from 7 paired biological and conventional farms showed significantly lower nitrate (fresh weight basis) levels for biological lettuce matched for variety on 5 of 8 sampling dates over 2 growing seasons. There were no differences on the remaining 3 dates, 2 of which corresponded to periods of low light intensity.
The latter two studies suggest that organic fertilizers might be more effective in lowering nitrate contents in spring and summer, corresponding to maximum solar radiation.
Less controlled studies have found few or no differences in nitrate levels based on fertilization practices.
Hansen (1981) reported lower nitrate content (% d.m.) for beetroot from 4 biodynamic growers compared to 4 neighbouring conventional growers, but no differences for potatoes, carrots, or curly kale.
During 6-year field plot experiments (Reinken, 1986), nitrate contents were higher only in single years with certain species of vegetables in the conventional plots compared with the biological plots. For 3 varieties of apples, there were no differences. This long-term study shows that results for one year cannot be extrapolated, and points to the importance of ongoing research.
Stopes et al (1988) found no distinct differences in nitrate contents of various vegetables and salad crops sampled from organic and conventional wholesale and retail outlets over two winters in England, although no statistical analysis could be done due to an insufficient number of samples. In some cases the organically grown vegetables were higher, while in others the reverse was true.
The authors state that the data suggest that peak nitrate concentrations may be lower in organically produced vegetables, based on the highest recorded levels having been found in conventionally labelled cress and lettuce. However, closer inspection of these results shows that 5 times as many conventionally as organically grown lettuces had been purchased, and that during the months of January and February, when the nitrate levels were very high, no organic samples had been obtained. In addition, no organic cress was available to compare with the conventional.
Although the study reflected the variable range of nitrate levels encountered by the consumer, in many cases the average monthly nitrate concentration was based on one sample only. Considering the wide range of values obtained for both conventional and organic produce, and that no variables (e.g. variety) were controlled, a great many more samples would have been required for any meaningful comparison.
Klett (1968, cited by Koepf, 1989) reported lower nitrate contents for organically grown spinach than that fertilized with NPK, the differences decreasing from light to half shade to deep shade. Field experiments carried out by Wistinghausen (cited by Koepf, 1989) showed that biodynamic manuring results in lower nitrate levels in carrots compared with NPK, the magnitude of the differences depending on the planting date.
Thus the interaction of a number of factors determines the final nitrate concentration in plants. However, in contrast to climatic and other environmental conditions, fertilization can be controlled by man.
It is evident that application of organic fertilizers with highly-available nitrogen can result in high nitrate levels. Therefore it is difficult to draw any general conclusions comparing the effects of different organic or mineral fertilizers on the nitrate levels in crop plants due to the different rates of mineralization of various organic materials. However, it is probable that careful application of appropriate organic fertilizers could result in lower nitrate levels in vegetables than normally seen following conventional fertilization practices.
The ultimate test of the nutritional value of food depends on its ability to support health, growth, and reproduction over successive generations of animals or humans.
Evidence for increased disease resistance, productivity, or fertility of animals feeding on organically grown fodder has been reported via personal communications, and is largely anecdotal in nature. Thus there are few data and few controlled studies. Most reports go back several years.
Sir Albert Howard (1947) held that crops grown on organically manured soil are resistant to disease, and that animals and humans eating this food will similarly be resistant. An example from his personal experience in India is that of organically-fed oxen resistant to foot-and-mouth disease. However, no controlled comparison using chemically fertilized fodder was made. Greenwell (1939) reported that when grain raised from composted soil was compared with a similar market purchased grain on poultry, pigs, horses, and dairy cows, all the animals on the organic grain did better and became more resistant to disease, while requiring 15 % less food. However, no data were given. It was also observed that cows preferred grass growing on dunged plots over chemically-treated grass when given a choice. Sykes (1944) reported healthier livestock and disease resistant crops as outcomes of organic fertilization on his farm.
Lady Eve Balfour cites a number of examples of increased disease resistance or disease cure in crops, livestock, and humans when soil was fed with organic material, or animals or children were fed organically grown food, respectively (Balfour 1959). A particularly interesting observation was that pigs fed soil rich in humus were cured of white scour, while soil from a chemically treated field had no effect.
More recently, Dr. John Whittaker (1979) attested to the high quality of animals from organic farms.
Dr. Donald Collins (1961) reported that 5 patients, who had had metastasized cancers during their lifetimes and had subsequently begun to eat organically grown foods, showed no evidence of previous malignancy at autopsy after their deaths many years later from unrelated causes. However, most of the tumours had been surgically removed at the time of diagnosis, and Dr. Collins did not indicate if his patients received other therapies as an adjunct to surgery. In addition, these patients may have made other lifestyle changes. These and other questions indicate some of the limitations of this type of evidence.
Results of the 34-year Haughley experiment (Balfour, 1975) showed that cows on the "organic section" produced significantly more milk on 10-15% less feed than those on the "mixed section" as well as having a better breeding record (see Appendix II for explanation). There were unspecified differences in the fatty composition of the bloods between "organic section" cows and sheep and "mixed section" cows and sheep, which Long ( 1971) believes may prove to be important in the pathogenesis of coronary heart disease. This experiment has been criticized on the grounds that its scale was too great to allow statistical evaluation, with variables that could not be anticipated, let alone controlled, and is sometimes even cited as evidence that no difference in nutritional value between organically grown and conventionally grown food exists (dukes, 1977; Anon, 1974). However, Oelhaf (1978) cautions against dismissing any possibility of the superiority of organically grown food, based on the questions raised by Haughley. It must also be noted that Haughley did not duplicate today's modern agriculture, which has changed since its inception (Alther, 1972).
Matile (1973) reported milk production results similar to those obtained at Haughley in a comparison of one Swiss biodynamic farm with 11 conventional farms, and also claimed that the Biodynamic milk showed signs of an increase in quality, but did not elaborate further.
The sperm quality of bulls from a breeding station using compost applications was superior to that of bulls from a comparable station where pasture land had been treated with NPK (Aehnelt and Hahn, 1978). During the winter, when the diets of the animals on the chemically fertilized farm were supplemented with more diverse feed, the difference in fertility level was lessened. Differences in soil, climate, etc. between the two breeding stations, as well as the possibility that the cover of the chemically fertilized pastures was less diverse, must be considered.
The facts that only a few nutrients have been studied and that the results of food analyses have been inconsistent indicates that nutritional comparisons between organically and conventionally grown food should be made primarily on the basis of biological tests with animals (Hodges, 1978). Feeding studies relate more directly to health than do chemical analyses, and can reflect factors that may not be detectable by chemical means (Hill, 1978). According to Brandt and Beeson (1951), animals should optimally be carried through breeding for several generations.
The earliest work in the literature compared the effects of cattle manure and complete inorganic fertilizer ("chemical manure") on the nutritive value of millet and wheat grown in India (McCarrison, 1926). Soil analyses showed some differences between the two types of plots, but it is probable that these had come about at least in part due to the different fertilization methods which had been practiced continuously for 13 years. "Cattle manure millet" was more effective than "chemical manure millet" in preventing weight loss in adult pigeons fed an incomplete diet. Since all animals in both groups died in an average of 90-92 days, the most that can be said is that at the time of death, the pigeons in the "cattle manure" group had lost an average of 15 % less of their body weight than those in the "chemical manure" group. However, the "cattle manure millet" delayed death from polyneuritis in pigeons from an average of 33 days for the "chemical manure millet" group to an average of 50 days in a similar experiment.
Rats fed a basal diet supplemented with "cattle manure wheat" gained an average of 10-17% more weight than another group supplemented with "chemical manure wheat", and although differences between the groups were not great, they were significant in one of the two replicates.
A number of interesting experiments performed by Pfeiffer have been cited by Linder (1973), who implies that they were well-designed. The mortality rate at 9 weeks of age for 3 generations of mice fed biodynamically raised grain was 9% compared to 17% for those on minerally fertilized grain (80 mice/group). In a comparison with hens fed inorganically fertilized wheat, those given biodynamically grown grain began laying at an earlier age (166 days vs. 181 days) and produced more eggs over 9 months (192/hen vs. 150/hen) with a better keeping quality (27% vs. 60% spoilage after 6 months at room temperature). Mice, whether raised previously on minerally or biodynamically fertilized wheat (20 mice/group), overwhelmingly preferred the Biodynamic grain when allowed free choice. When 10-11 earthworms were placed in each of 4 adjacent boxes filled with soil plus various fertilizers, 50% had migrated from the boxes with mineral fertilizer and urea to those containing Biodynamic compost after 3 days.
Arnon et al (1947) reported no differences in the growth of guinea pigs fed solely on grass grown either in soil plots having a history of organic and inorganic manuring or without soil in a synthetic inorganic water-culture medium (i.e., free of all organic matter) over a 12-week period. The growth fluctuations that were observed were attributed to variability among the animals, although no statistical analysis was done. In any case only very few animals were included in each group, and it is questionable whether they represented a homogeneous population.
No differences were found in the reproductive performance of successive generations of rats fed wholemeal flours (supplemented with CaC03, NaCl, Vit A) prepared from wheat grown on experimental plots at Rothamsted, and fertilized with either dung or artificials (Miller & Dema, 1958). However, neither experimental design nor results were reported by the authors.
Greaves and Scott (1959) compared the nutritional value of wheat from the three sections at the Haughley experimental farm by testing its effects on the growth of weaned mice. The weight gain from greatest to least was: "stockless section" mice > "organic section" mice> "mixed section" mice (see Appendix II for definitions). Although the experiment was repeated 3 times with a large number of animals (150), results were of limited significance due to slow growth in all groups on this deficient ration.
When the mice were subsequently used in breeding tests (Scott et al, 1960), mice fed "mixed section" wheat gave consistently poorer results than the other two groups (number of live births; number of young surviving at 21 days). No statistical analysis was done, so it was not possible to assess differences between the "stockless" and "organic" section mice. Male mice receiving "stockless" section wheat were more often affected by degenerative changes in the testes, but only a very small number of animals was examined histologically. The authors conclude that reproductive performance indicated differences between diets, whereas comparative growth tests had barely done so. Despite the fact that there may have been compositional differences between the wheats, this study does not permit any conclusion about the relative nutritional quality of organically and inorganically grown wheat. It can be argued that any differences would be meaningless because, compared to mice on a control diet, all mice on the wheat diets performed poorly.
The overall reproductive performance, based on the total number of animals weaned, was superior for Dutch rabbits maintained on leys, wheat, and hay from the "organic" section of the Haughley experimental farm (see Appendix II) compared to those fed from the "mixed" section (McSheehy, 1975). The reverse was true for New Zealand white rabbits, which is at variance with the results obtained for mice by Scott et al (1960). It is interesting to note that a crossover experiment was performed in the case of the NZ white rabbits only. Milk-production, based on weights of 21-day old rabbits, was higher in rabbits on organic leys, but growth rate of litters did not favour either group. The fact that animals were fed ad libitum and amounts eaten were not measured makes it difficult to interpret this study. Because organic amendments as well as inorganic fertilizers were used on the "mixed" section, perhaps a comparison with "stockless" section feeds would have resulted in more definitive differences, although this was not the case in the previous study by Scott et al (1960).
In contrast to both Scott et al (1960) and McSheehy (1975), but in agreement with Miller and Dema (1958), McSheehy (1977) failed to detect any differences in the reproductive performance of mice fed either low protein or casein-supplemented diets based on wheat flour from the 3 sections at Haughley in a comprehensive study. However, the "mixed" wheat diet resulted in significantly greater weaning weights of the offspring, for both the low and high protein diets.
Aehnelt and Hahn (1978) reported that rabbits raised on hay from a biodynamic farm showed superior fertility characteristics (ovary weight; number of ovulations; number of egg cells found; per cent fertilized egg cells; number of uterine glands) compared to two groups of rabbits fed intensively fertilized hay from farms with sterility problems in cows. Parallel studies using carrots or kohlrabi yielded similar results for some, but not all of the fertility criteria. Only one of each trial was performed, and a small number of animals was used in each treatment, with no statistical analysis or indication of the fluctuation between animals of the same group.
Comparing diets based on raw materials grown under either conventional or biodynamic farming and equivalently supplemented with vitamins and minerals, Staiger (1988) reported that the birth rate for first generation rabbits in the two groups was not different, despite the fact that the biodynamic group was eating 25% less. The birth rate rose in the second generation in the biodynamic group only, thereby becoming statistically significantly higher. The number of embryos in sacrificed females of the first generation was equal, but was significantly higher in the Biodynamic does in the second and third generations. Conventionally-fed second generation animals suffered infectious illnesses significantly more often than biodynamically-fed. This study emphasizes the importance of conducting long-term intergenerational feeding studies to show differences in nutritional value. It also suggests that carefully carried out studies might show real differences in the nutritional quality of produce.
The quality of plant products is also based on their flavour, and texture, and therefore indirectly of chemical constituents contributing to these properties
The claim has been made that organically grown fruits vegetables and grains taste better than conventionally grown (Koepf, 1989; Feltman, 1974; Linder, 1973; Sykes, 1944). -concede only that they may be superior to the extent that they may be fresher: organically grown foods are usually harvested closer to peak maturity and sold locally, while commercially grown produce is often shipped many miles and may reach the consumer weeks after harvest. These sceptics deny that quality differences have anything to do with fertilizer practices. Still others (dukes, 1977; Johnson, 1975) conclude that organic foods are generally lower in quality than their conventionally grown counterparts, based on data reported by Appeldorf et al (1974), which compared "health" foods purchased from a health food store with equivalent traditional foods for sensory characteristics and overall acceptance. Jukes equated health foods with "organic" foods, and interpreted the results accordingly. This was in spite of the facts that it was not actually known whether these foods had been grown organically, and almost all had undergone some degree of processing. These probably could have been more accurately called "natural" foods. Contrary to all of these views, White (1972) believes that it is not possible to prove the validity of these claims for superiority one way or the other.
The results in the scientific literature show no consistent pattern of sensory quality between organically grown and conventionally grown plant foods, although there is evidence from more than one source that organically grown potatoes taste better than conventionally grown after storage. For many of the studies discussed below, experimental design is flawed or poorly documented, and conclusions difficult to draw.
Schutz and Lorenz (1976) compared consumer preferences for four vegetables grown under "commercial" and "organic" conditions using a 9-point hedonic scale. They found no significant preference based on fertilizer treatment for either lettuce or cooked green beans. The small but significant preference for cooked organic broccoli was seen for only one of the two replicated plots, with no difference apparent for the other. Finally, there was a significant preference for commercial carrots over organic. From these results, the authors conclude that the consumer would not be getting a preferable product by purchasing organically grown vegetables.
Although this study attempted to control growing conditions, postharvest treatment, and harvest time based on level of maturity, the crops of the various treatments were in fact harvested on different dates due to different growth rates. Lettuce was harvested on the same date. The problem of harvesting would have resulted in different storage times, possibly affecting freshness and therefore sensory quality of the vegetables. As details of the harvest dates in relation to fertilizer treatments are not given, it is unclear what effects, if any, this may have had on the results.
Another problem was the sensory panel: it is not reported if the members were adapted to, or even familiar with, organically grown foods. If this was not the case, it may have introduced a bias. Therefore these results cannot be generalized to all consumers.
Paired comparison tests for appearance, colour, texture and flavour performed by a 12-member panel revealed a highly significant preference for canned tomatoes from organic garden plots compared to NPK-fertilized tomatoes for all four sensory characteristics (Svec et al, 1976). The colour and texture of conventionally grown baked potatoes were significantly preferred. Their appearance and flavour were also preferred, but differences were not significant. There was no significant preference for either organically or conventionally grown boiled potatoes for any of the four criteria tested. As in the previous study, it is not clear if the sensory panel was accustomed to organically grown foods.
No significant sensory differences were found in raw, cooked, or frozen and cooked spinach by fertilizer type (undecomposed dried bloodmeal vs. ammonium sulfate) or level in subjective tests (Maga et al, 1976). Although the taste panel was trained, it is unspecified whether or not its members were adapted to organically grown as well as conventionally grown food. However, since this study employed difference (triangle) tests rather than preference tests, the importance of an adapted panel was not as great as for the first two studies described. Objective tests of overall flavour intensity of raw spinach using gas-liquid chromatography headspace analysis of total volatiles showed similar results for organic or mineral-N sources at equivalent levels of application, although the data were not analyzed statistically.
It should be noted that this was not a strict comparison between organic and mineral fertilization, as all treatments received treble superphosphate for sidebanding. Furthermore, the authors suggest that different organic fertilizer sources might yield different results.
Hansen (1981) conducted triangle and taste preference (lo oping numeric scale) tests for vegetables grown on 4 pairs of adjacent biodynamic and conventional fields over 2 years, although not all pairs were tested for each vegetable and year. The trained panel, 50% of whom were Biodynamic growers, detected significant differences for boiled cubed beetroots from 1 of 2 farm pairs for both 1973 and 1974, and for raw grated carrots from 1 of 2 farm pairs in 1973 and for both farm pairs tested in 1974. There were no differences for boiled chopped curly kale sampled from 2 pairs of plots in 1974. Biodynamically grown carrots were significantly preferred for the first of two farm pairs in 1973, while conventionally grown were preferred for the second. Although biodynamically grown beetroot and carrots tended to score higher for 1 of 2 farm pairs in 1974, the differences were not significant.
Reporting on a field study at a German agriculture experimental station comparing biodynamically and conventionally grown vegetables and fruits, Reinken (1986) states: "In popularity tests many results showed a preference for the products from Biodynamic plots". In fact, the sensory tests cited show results in favour of both types of products. For example, the sap of red beets at harvest and after 4 months' storage, and cooked savoy cabbage (after 4 months' storage) from the Biodynamic plots were judged better, while conventionally grown cooked white cabbage, grated raw carrots, both fresh and stored, and cooked bush beans were preferred.
There were no differences for three apple varieties either after harvest or after several months' storage (Reinken, 1984), nor did taste tests show differences in sweetness, texture or overall acceptability for organic and conventional peaches (Racer et al, 1985). However, few details of the procedures followed were described in the latter study, and none in the former.
Over three years of a 6-year field study, Pettersson (1977) found that, on a scale from 1 (poor) to 4 (excellent), biodynamically grown potatoes had a significantly higher ranking for taste than conventionally grown, especially after storage. Dlouhy (1977) confirmed these results in a parallel study with peeled but not unpeeled potatoes. No experimental detail given by either.
Pettersson and Wistinghausen (1979) detected no difference in taste between organically and conventionally grown potatoes after harvest during four years of testing. However, organically grown potatoes scored significantly better (4-point scale) than conventionally grown after storage.
Organically grown potatoes obtained significantly higher mean taste scores than conventionally grown after 6 months' storage when tested blindly by a panel (Goldstein, 1981; cited by Linder, 1985).
Nilsson (1979) found no sensory differences for carrots, cabbage, or leeks grown organically or conventionally for two consecutive years, and Schuphan (1974), during 12 years of organoleptic tests, obtained no "reliable results" Neither author provided any experimental detail whatsoever.
In summary, the evidence shows that for some products, organically grown can be demonstrated to be superior in flavour or overall sensory acceptability to conventional, but that indeed the opposite is also true. It seems clear. therefore, that results found for one product cannot be applied to others.
Although there were problems in experimental design and especially in reporting for the studies cited, all at least attempted to control some of the variables involved. However, it would be interesting and instructive to compare the sensory quality of organically and conventionally grown products as purchased at the retail level by consumers in a specific location. In this case, the product history probably would not be available, and variables other than fertilizer type, known to affect sensory properties and levels of flavour and aroma compounds (varietal difference; ripeness; temperature and amount of sunshine during growth; geographical location of growth) could not be controlled. From another point of view, since this is the manner in which consumers obtain these products, data generated in this way would yield valid evidence for comparison.
Discussed below are three methods that have been used to evaluate quality differences between organically and conventionally grown foods. Each must be considered as indirect measures since it is not clear what, if anything, the observed phenomena have to do with the effect of the food on human health or preference. In addition, in the latter two cases the lack of understanding on the mechanism of the phenomena and the subjectivity possible in interpreting them, make it difficult to draw conclusions on what the reported results indicate.
After the percentage germination of unblemished seeds of grains is recorded, seeds from the same lot are heated to 100° C for 10 or 30 minutes in order to determine the percentage germination after heat treatment. The variable capacity of grains to germinate is considered to be based on differences in seed protein quality.
Biodynamically and organically raised wheat seed showed smaller losses of germination power after 30 minutes heat exposure compared with minerally fertilized seed (Pfeiffer 1958). For example, the average germination rate for 5 samples (100 seeds/sample) of Biodynamic wheat was 91% compared to 57% for 9 samples of chemically fertilized wheat (tinder, 1973). Among the latter group were some seeds which gave very good results and others which gave very poor results. All wheat samples came from New York, New Jersey, or Pennsylvania, but no other details concerning their origin were available.
The average germination rate for 6 samples of minerally fertilized corn from Indiana or Florida decreased to 2 % after heating, compared to 98% for biodynamic corn. However, this test was based on only 2 samples of Biodynamic corn originating from the eastern United States.
A pre-determined quantity of an appropriate dilution of a plant extract is added to cupric chloride and crystallized on a glass plate under conditions of controlled temperature and humidity. Each type of biological product produces a typical crystallization picture which can be reproduced.
The specific morphological pattern formed (assessed under a microscope) is thought to be determined by the kind and quality of protein present in the extract, and certain zones within the crystallization picture are "protein specific", showing changes influenced by proteins. Structural differences or changes in patterns signify differences in protein quality (e.g. denatured proteins) that may not be detected by chemical analysis, but are of biological importance.
This "representational" method has several problems. Its mechanisms are not yet fully understood, and its results show variability and therefore poor reproducibility (Knorr and Vogtmann, 1983). The plate material is classified visually according to the kind and intensity of signs which differentiate one fertilizer treatment from another. This can be a very subjective process, especially if the researcher knows the origin of the specimen beforehand.
In reporting results all the studies cited rely on description of crystallization patterns rather than on reproduction of the actual plates, which would require too much space.
Pettersson and Wistinghausen (1979) evaluated crystallization pictures of potatoes grown in a field plot experiment over a 4-year period. Organically grown potatoes had statistically significantly fewer defects in their patterns and therefore better quality than conventionally grown potatoes. The crystallization pictures of fresh organically grown cabbage juice produced well-organized needle ramifications as opposed to those of chemically fertilized cabbage (Engqvist, 1962). Differences were statistically significant. After 6 days' storage, the patterns for organic cabbage juice showed fewest morphological changes, with increasing disintegration for those grown conventionally. Based on this observation, the author implies that the organically fertilized cabbages have a slower rate of breakdown than those minerally fertilized, and are therefore of superior quality. Four years of crystallization tests on wheat, brown beans, white cabbage, beets, potatoes, cucumbers, spinach, and red clover after harvest and during winter storage revealed that crops receiving Biodynamic or organic fertilization ranked ahead of those receiving NPK (Engqvist, 1965). Klett (1968, cited by Koepf, 1969) used cupric chloride crystallization to show a better crystallization standard for organically grown spinach and wheat in a 3-year field trial. In addition, the patterns of organically grown plants deteriorated more slowly during storage in comparison with NPK fertilized.
Klein (cited by Koepf, 1969) found that freshly prepared extracts from NPK fertilized plants frequently produced crystal patterns resembling decomposed extracts from organically grown.
Koepf and Selawry (1963) found that extracts from seeds of minerally fertilized oats, wheat, and peas grown in a 3-year field experiment produced more irregular crystallization pictures than those fertilized organically. The amount of specimen required for producing typical effects was half as much for seeds fertilized with manure, thus showing higher "forming" effects of organically fertilized seeds, which was retained for a longer period of time. This was attributed to different contents of enzymes in the extracts and therefore levels of enzyme activity.
Only those morphological characteristics obtained regularly over the study period of three years were compared, while others were not considered. This raises questions, considering that it is not known precisely what crystallization patterns indicate.
Individual comparisons between 4 pairs of matched Biodynamic and conventional growers resulted in a significantly better crystallization value for 1 sample of biodynamic and 1 of conventional potatoes after 4 months' storage, with no differences for the two remaining farm pairs (Hansen, 1981).
A sodium hydroxide plant extract is eluted into a filter paper disc which has been treated or "sensitized" with silver nitrate. Patterns and colours develop in several hours to days after the paper is dried.
Pfeiffer has interpreted the small round holes and the light coloured ring which sometimes appear in chromatograms as signs found only in live material, although their chemical nature has not yet been established.
He attributed the spokes which extend from the outer area of the chromatogram towards the center to the`;quality as well as to the quantity of proteins present in the extract. However, Knorr (1982a) found linear and highly significant correlations between the area of lowest optical density in the center of the chromatogram and the protein concentrations of model solutions. Differences between the chromatograms of organically grown and NPK fertilized collards detected by a panel and based primarily on differences in the pattern of the spokes were thought to be due to the effect of nitrate concentrations (Knorr, 1982b).
Thus, the difficulty in evaluating the various components of the chromatographic patterns is clear. The mechanisms of both this method and the crystallization method must be more fully explored before conclusions about food quality based on these evaluations can be made.
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