Balanced Nutrition of Soils and Plants Part One

Economic pressure, in terms of lower actual cash returns for the farmer’s crops, has brought a new element into the planning and thinking of some of our top agronomists. The grower’s pay for his year’s work is being considerably lessened through the toll taken by pests and diseases. So emphasis, at least in some quarters, is being shifted to the development of resistant plants and to biological controls instead of poisons.

Along with this trend there is just beginning to be a realization of the fact that increasing numbers of consumers are willing to pay top prices for really high quality foods. And in this regard the most advanced research shows that “high protein content” by itself is not necessarily the answer. Work with the amino acids has shown, among other things, that high protein brought about by excessive nitrogen fertilizing can actually lessen rather than increase the nutritional value of grains and vegetables. At the same time, scientifically managed organic fertilizing can give better results, in terms of food values, even with a relatively lower protein content.

It is the purpose of this article to show, in some detail, how and why these things are so. Their importance, both for the grower and the consumer, is obvious.

 

In general, the farmer, the commercial grower of fruits and vegetables, is only interested in top yields, for he is paid for the quantity of his products. Seed breeding, selection of varieties, any measures with regard to agriculture, soil fertilization, soil cultivation, are all geared to produce bigger yields.

The spreading of insect pests and plant diseases has brought a certain change into this quantity production concept, namely, there is now a demand for resistant plants. This is probably the only beneficial aspect of pests–that their existence calls for a change of agricultural thinking. It is obvious that the maximum possible yield is economically dubious if ten, twenty per cent or more of this yield is destroyed by pests. That much less yield, not attacked by pests, would be preferable because, while the total crop would be the same, spraying cost and labor would be saved, thus giving a bigger profit.

One approach to the problem has developed which is in tune with the demand for natural food production: the biological control of pests, instead of the spraying of so-called economic poisons, especially those of lasting effect and causing dangerous amounts of insecticide or pesticide residue on food plants. The health-conscious consumer is not so much interested in the yield per acre, but he demands a food of highest nutritional value, free from poison or irritating contamination. Biological control of pests is one answer to this demand. Biological control brings up one of the most important problems: that of biological balance in soil, in plants, in the environment of growing crops.

To maintain and to create balance is, therefore, the first step towards crop improvement with regard to quality. That we deal today with disturbed natural balances in the production of nutritional values is another conclusion which the facts press upon us.

Here the problem of food quality enters. If anything goes wrong in agricultural production, the first question should never be, “Which and how much fertilizer should one use?” but rather, “Which principle of balance has been violated?” The fertilizer use is only a small fraction of the entire balanced pattern. There are many other factors involved.

A little story from England illustrates the complex nature of the problem. The seed production of Kentish white clover in the area of a famous seed producing village in the south of England was reduced to near catastrophe. Everything was tried, more and stronger fertilizers–no result. The authorities and experts were stunned. Finally, the village blacksmith came up with an answer: “It is the cats here which reduce the seed production.” People thought the man himself was unbalanced until he finally explained: The cats had developed a liking for bumblebees, which they ate en masse, therefore interfering with the pollination of the clover, which is brought about by the bumblebee flying from blossom to blossom. The cats were removed, the bumblebee population increased and the seed production went back to normal. Here the cats were the limiting factor and the reason for a disturbed balance.

Unbalanced fertilization can be an important limiting factor. A basic law of plant nutrition says that that substance which is present in the minimum determines the issue. This law of the minimum, which was first hinted by the German agricultural chemical concept of Liebig and Mitcherlich, has a much more universal application than the chemists dream. In the above described story, the bumblebee was at the minimum. Many other factors can be at the minimum–Light, for instance, water, trace minerals, air in the root area, physical conditions of the soil, seed viability, etc.

The problem is made still more complicated by the fact that an excess of one fertilizer element may cause deficiency symptoms with regard to others, even though these others are theoretically present in sufficient amounts. Excess symptoms in soils and plant nutrition may not be recognized as such, but treated as deficiencies of something else. Again, it is the balance which creates conditions for maximum efficiency.

The example of excessive nitrogen fertilization is at present probably the best known. Plants take up too much nitrogen and begin to show deficiency symptoms of phosphate and potash. The fertilizer-minded farmer then is advised to use more phosphate and potash, while the restoration of the balance with less nitrogen would bring about the same effect–better production.

This nitrogen situation, however, involves another problem: that of the protein quality versus protein quantity. It is a general occurrence that the protein production in a plant is reduced with the depletion of the soil. Many figures in nutritional textbooks with regard to protein content no longer apply. For instance, the protein content of wheat (red, soft) is given as 12%. In fact, most red wheats analyze today between 8% and 11% protein. In corn, it has been found that more nitrogen increases the protein content, but it has also been discovered that the protein quality is lacking. We speak of “unstable” proteins which are prevalent in grains in general. These conditions, at present, are much better studied in animal nutrition than in human nutrition.^1-2

What is protein quality? The protein is built up of amino acids, which perform the role of building stones. Some 22 amino acids, on the average, participate in the building up of protein, of which 10 are essential for the nitrogen metabolism and 17 more are important for nutrition. The amino acids which are most important are: alanine, arginine, aspartic acid, cysteine, cystine, glutamic acid, glycine, histidine, leucine, lysine, methionine, phenylalanine, proline, tryptophan, tyrosine and valine.

The functional role of these amino acids will be discussed in another article dealing mainly with human nutrition. Each amino acid has a definite functional role. Lysine is the limiting factor, for it sets the pace for the utilization of all others. Another limiting factor is tryptophan. It has been found recently that excessive nitrogen fertilization depressed the formation of lysine, so that the increased protein production is more than compensated for by the lowered lysine content, meaning that the nutritional value of said corn so fertilized is reduced.1 Since grain in general is low in lysine and tryptophan,2 excessive grain feeding with concentrates has caused chronic lysine and tryptophan deficiencies in livestock. It is for that reason that milking cows are frequently overfed with protein in order to keep up with milk production, which excessive unbalanced protein intake in turn increases the susceptibility to mastitis. The first advice given to the farmer in cases of mastitis usually is to reduce the grain feeding. Arginine deals with the synthesis of hormone protein. The many cases of sterility in livestock may be reduced to the fact of an unbalanced arginine in the protein supply in addition to tryptophan. We have seen high production milk herds with a balanced protein feeding of 14% grain mixture and no trouble as against others with not any better production but lots of troubles, and an 18% to 22% protein of an unbalanced structure.

The problem of protein quantity versus protein quality is quite fascinating. Its proper recognition may change all our nutritional standards. L. B. Nelson reports that feeding trials with animals indicate an inferior quality in the protein of high protein corn (¹ page 346; also page 347) and the quality of protein was poorer from better treatment because of higher zein content and lower lysine and tryptophan content. He reports that 24 lbs. of nitrogen per acre produced in corn a protein content of 6.8 to 8.2%, while 84 lbs. of nitrogen produced 9.3 to 12.0% protein, but arginine, glycine, lysine and tryptophan (these two being the limiting factor), also threonine and valine, decreased. Only leucine, alanine, phenylalanine and proline showed increases causing an entirely unbalanced and nutritionally defective protein. Soils high in nitrogen and phosphate produced a reduction of niacin in corn, while thiamin was increased. So-called better fertilizer practices can produce 30% more protein than unfertilized plots, but the protein quality is much poorer. By the way, phosphate and potash fertilizers have little influence upon the protein production.

We are now facing the situation that the fertilizer practices of the farmers have an important influence upon the nutritional quality of the crop but–and this is the decisive question–who lives up to the facts? A complete revision of our nutritional standards is needed. Just to say “protein” without knowing the actual composition of the protein can lead to severe errors in the calculation of a feed or food formula.

One reads, for instance, that 24% protein is needed for egg production. “What protein?” we must ask. Arginine, glutamic acid, histidine, isoleucine, tryptophan, valine, are essential for egg production.³ With the exception of glutamic acid, the removal of any one of the mentioned amino acids resulted in immediate disruption of the feed consumption and a 10-day pause in egg production, even when the incomplete diet was fed only for five days. Still, the hens were feeding lustily, being deceived as the poultry keeper was. The hen does not need glycine for egg production, but the growing chick is very dependent on glycine. Still, the label on the feed bag reads only X% protein. In human nutrition, from now on, we will also have to ask: “What kind of protein?” (About this in a second article.)

Other relationships in the soil treatment and plant nutrition enter the picture. We will quote a few.

High nitrogen fertilization increases the calcium content in plant tissue, therefore requiring a good supply of this element (lime). But excessive liming reduces the availability of boron and manganese.¹⁸ This is one of the most illustrative examples of the balance problem. High ammonia fertilization, however, depresses the calcium and potassium absorption and, to a certain extent, that of magnesium. Magnesium is essential for the chlorophyl production, the assimilation and photosynthesis and the efficiency of enzymes. The lush green nitrogen-rich foliage, therefore, can be quite deceiving. It can also mean that the plant takes up too much water, but the seed or fruit production and quality is lowered.

The protein balance and quality are frequently interfered with by trace minerals in the soil. Iron and zinc deficiencies increase asparagine and glutamic acid in tomatoes, while the level of all amino acids was low in molybdenum deficient plants.⁴ Beta-alanine accumulated with zinc, copper and molybdenum deficiency; histidine was absent with copper, manganese and iron deficiency; phenylalanine with copper and lysine with copper, manganese and molybdenum deficiencies. From this research, done in Australia, the importance of well balanced soils for nutritional quality production becomes quite apparent. Mulched or dry land potatoes in Nebraska⁵ had a higher vitamin C value as compared with non-mulched or irrigated potatoes.

The ascorbic acid content decreases rapidly during storage, curiously more so at low than at high temperatures.⁶ The highest vitamin C content was found in those parts of plants most exposed to light during growth,⁷ which points to differences in plants grown in sunny or shaded areas. In general, sunny seasons and cloudy, overcast seasons can change the protosynthesis and vitamin content considerably. That processing has a decisive influence is well known, but that copper-lined processing equipment reduces the vitamin C content of tomatoes is probably less known.⁸ Ascorbic acid losses during freezing and in frozen storage were greatest in unblanched and under-blanched vegetables, as observed in broccoli, green beans, lima beans, spinach and squash.⁹

Peat type soils reduce the vitamin C content of potatoes in comparison with loamy soils. Adequate moisture supply during the main growth period is most important¹⁰ a point for high organic matter and humus soils. The carotene content varies considerably. Carrots have been found with little or almost no carotene; nitrogen supply appears to increase carotene; lack of phosphate or potash decreases it, but above a certain optimal level, increased phosphate and potash did not cause a further increase in carotene.¹¹

Tangerines grown on the south or west side of trees had the highest content of vitamin C, while those grown in the center, north or east of the tree, had 25% less. Tangerines grown on lemon rootstock contained less ascorbic acid than those grown side by side on sour orange stock.¹² Tomatoes ripened without access to light contained 45% less ascorbic acid than those grown to maturity in full sunlight. Natural sunlight is a stimulant for the accumulation of ascorbic acid.¹³

The intensity of light during the growth of a vegetable is a great factor for many values. Thiamin, for instance, in tomatoes, beans, peas, corn and New Zealand spinach was found to be greater when grown in high light intensity as against lower. One exception was white corn, which behaved the opposite.¹⁴ Alas, very little is known yet about how to influence light absorption and efficiency.¹⁵ Seasonal changes in carotene content have been observed in lettuce in Puerto Rico, with an increase from December to February and a decrease during the summer months. Vitamin C, on the contrary, was highest in sun-exposed fruit and lowest in shaded fruit.¹⁶ Ascorbic acid in turnips and tomatoes decreased 20% with increasing boron supply and 25% with increasing manganese supply, while in tomatoes with copper trace mineral in the soil, an increase of 60% was observed. Seasonal fluctuations of boron content in alfalfa plants of 300% in one season have been observed, with a low during July and August.¹⁷

These phenomena unroll the problem of balance in trace mineral application. Trace mineral means what the word says: T-R-A-C-E. Due to the fact that trace amounts are difficult to mix with large amounts of other fertilizer material and due to an over-zealous concept of correcting deficiencies, many farmers apply much too much trace minerals. It should always be borne in mind that excess symptoms frequently mask deficiency symptoms of another element as soon as the balance is disturbed. We have seen cases where a farmer has, in one application, supplied as much trace minerals as to be sufficient for the next 1500 years.

This defeats the purposes. While gross toxic symptoms may not always show up, as in the case when the soil contains more than 30 parts per million boron, it must be assumed that the nutritional structure of a plant can be considerably distorted. Trace mineral application as foliage spray in the proper dilution is a much safer way, inasmuch as it has recently been confirmed that leaves absorb minerals from sprays and air. The required amount of molybdenum per acre is so small that only a highly diluted application is necessary. Two ounces per acre will be sufficient, producing an effect that will last up to ten years. One-sixteenth of one ounce already results in noticeable reactions.

One other way is to feed the trace mineral through the livestock and to get it into the soil by way of manure. Sea kelp as feed supplement has proven to be especially valuable, for here we have the trace minerals in a natural balance as brought about by the living plant itself.

Manganese is important, but in highly acid and podzolic soils its availability is increased and easily assumes toxic concentrations. was shown that growth disturbances already occur when the soil content was 1 ppm on potatoes, 1.5 ppm on clover, 2.0 ppm on lespedeza and 3.0 ppm on soyabean.¹⁹ Liming can tie down manganese, while sulphur releases it and increases the absorption by plants; so does raw organic matter.

The colloidal structure of soils and, especially, the humus content (not raw, undecomposed organic matter) have a balancing effect because they can hold any excessive amount and plant roots will take up only as much as they need. Humus acts as a well guarded storage and contributes the most beneficial effects to the maintenance of the soil balance. But humus is a well digested form of microlife in the soil and not just plain organic matter. The emphasis is to be laid on the digested form of organic matter and the colloidal structure. No raw or insufficiently decomposed compost can produce the beneficial effects of humus. Even green manuring, for the first two or three months after being plowed under, can disturb nature’s balance, especially the nitrogen balance. The maintenance of a proper humus structure is, therefore, the only way under the control of the farmer or grower to avoid imbalances and to bring about the production of maximal nutritious values in his crops.

Much more could be said about this subject. We will continue to quote a few more balance problems. Sodium in higher concentrations is definitely a plant poison except for typical salt marsh plants. In vegetables, only spinach and asparagus thrive with salt. But salt applications on low potassium-containing plants increase the potassium content of such plants and decrease calcium and magnesium.²⁰ On the contrary, plants sufficiently provided with potash decrease the amount of sodium absorption, therefore are protected in a way. Broadcast application of lime on peanuts resulted in reduced potash assimilation. Row dressing with gypsum increased the calcium, magnesium and potassium content of peanuts.²¹

One of our most important findings was published by John C. Cain of the Geneva, N. Y., Experimental station.²² It was observed that typical leaf deficiency symptoms on apples appeared only when one of the two–potassium and magnesium–was high. We quote: “It would thus appear that the leaf injury or symptom normally attributed to a deficiency of one element (magnesium) might actually be a toxic effect produced by an excess of the other element (potassium).” When both were low, there was reduced growth but no leaf injuries or deficiency symptoms showed up. Bacterial leaf spot on peach increased with potash excess, but was reduced with calcium. Infection was related to a low vigor resulting from a low proportion of nitrogen in the N/K and iron/manganese balance. The authors conclude that this is associated with lack of organic matter in the soil.²³ The two limiting elements for phosphate fixation in soils are calcium in neutral and alkaline soils and iron in acid soils. Excess of manganese may include a deficiency of iron.

The phosphate recovery from fertilizers by plants is rather low–2 to 10%; in the case of corn up to 15%.¹ High potash application depresses the nitrogen level in the leaf and intensifies nitrogen deficiencies. Ammonia from ammonium sulphate (too quickly available) lowered the yield on soils high in potash, especially if potash was simultaneously applied. Again, boron and potash are closely related, increasing together. High sulfur application lowers the calcium intake and nitrates. Low sulfur in the soil increases the uptake of calcium and nitrates. High magnesium decreases the uptake of sulfur. Phosphates increase the uptake of manganese. Zinc deficient plants were too high in phosphorus, potash, copper, manganese. Absorption of sodium and potassium is low in the dark, but is high in the light.

Lack of air, soil compaction, excess moisture and water-logged soils decrease the uptake of (in the order given) potash, calcium, magnesium, nitrogen, phosphates in corn plants. Probably each plant species has its own behaviorism and should be studied individually. Aeration of the soil, therefore, is one of the most important means of making the mineral nutrition of the plant more efficient. Under drought conditions, a poor yield results regardless of the amount of fertilizer applied. The effect of soil moisture on phosphate is less than on nitrogen and potash. Magnesium, however, has been found highest in plants on soils of low moisture.

Temperature also plays an important role. In potassium, nine times as much is absorbed at 90° F. as compared with 40° F. Nitrate is more absorbed at lower and highest temperatures, while ammonia is best absorbed at warm temperatures between 65° to 100° F. Cold, wet, warm, dry seasons, therefore, have a great influence upon the nutritious value of a crop.

To make things even more complicated, we will now unfold another problem which has been overlooked so far: the differences in seed quality where the seed derives from different locations on the same plant.²⁴ The seed from the two lower quarters of the soyabean plant was found to be 0.5% higher in oil and 1% lower in protein than the seed from the upper half of the plant. The highest oil content was found on the central and lowest nodes. High yielding plants produced consistently a higher oil content. Even within the pod, differences from tip to bottom were observed. The paper referred to above24 contains the remarkable sentence: the data present indicate that a plant breeder must give careful attention to the part from which seeds are collected.

 

Part Two

Rudolf Steiner, the founder of the bio-dynamic farming method, had already in 1924 pointed out that seeding of winter grain close to the winter months produced entirely different quality from seeding closer to the summer. Nearer to the winter, seeding reinforces reproduction factors, while nearer to the summer seeding reinforces nutritional factors. Now, with recently developed analytical methods for protein quality, amino acids in the grain, we can demonstrate the differences not only in the protein-carbohydrate balance but can go a step further and demonstrate the difference between the reproduction genes and the nutrition genes. It will take only a few more decades for seed breeders to make conscious use of these newly discovered properties.

An unpublished work of a bio-dynamic seed breeder in Germany, which was shown to this writer several years ago, demonstrates that inherited factors in grain from a different location in an ear are quite different and entirely different growth patterns can be observed if repeated generations selected from a specific location in an ear are produced.

While through harvesting, combining, milling, these differences are completely suppressed so that the consumer gets an “over-all” mixed product, the seed breeder could make conscious use of the newly discovered principles in order to select plants with a higher nutritious and balanced protein structure.

The reader at this point will say: This is all very interesting, but so complicated that it will be difficult, if not impossible, to live up to the knowledge concerning all factors in soil nutrition and health food production. One would need the services of many laboratories to test soil and environment in order to practice correctly what we have learned about balances.

Our answer is simple–maybe with a grain of philosophy. The disturbances of nature’s balances have been brought about by one-sided development in nature, for instance, climate (polar and tropical), drought and flood, by the natural weathering of original, primeval rock with the final end that such extremes as clay (loam) or sand have resulted. Nature always has understood how to maintain life and to restore balance; that is, to adjust itself to circumstances. Sometimes the corrections and adjustments of nature follow a long, erratic path, but it always leads to survival.

To maintain life and growth is an inherent property of nature. Physics has taught us that, if there is a force which disturbs the equilibrium, immediately a counterforce will be created which tries to restore it. This is involved as a consequence in the second law of thermo-dynamics, which has a universal validity. The greatest disturbing factor in nature is man, because he creates conditions which are based on his limited knowledge and one-sided purpose of action. Man tries to understand and imitate nature but, after all, has not attained as yet the wisdom of the Creator, who has created nature. All his measures, therefore, are still incomplete and subject to correction, amendment. Since not any one single human being can concentrate upon himself the wisdom of all ages, of all nature, he can at least learn from and work with nature. If he wants bigger and bigger crops, he will eventually find means to achieve it. If he wants health, he has to include the principle of balance.

The mineral fertilizer concept, which was geared to bigger quantity production and looked upon nitrogen, phosphate, potash and lime as the only means of producing crops, had neglected the role of trace minerals, of humus, of water preservation, of soil conservation, of quality and nutritious food production, of balanced protein, etc. It took not even 100 years to learn more and to see the result of this one-sidedness, and it took not even 30 years to discover the role of deficiencies.

Now we stand at a turning point in history: the problem of health and balance has become paramount. From the mere mineral chemical concept, man has advanced to an organic concept. This is the one which fits the problem of growth and health. We learn that excess phenomena in any direction can be as disastrous as deficiencies. We are brought back to a golden middle way. The desire of man to restore the balance and to draw from natural resources has brought about such movements as the organic farming and gardening trend and, most recently, the Natural Food Associates. That these movements originate is only “natural”; it is a consequence of the previous trend to one-sided quantity production which demands the counterforce of quality and health production. In a way, man has overshot the goal and must now stress all research and aim to correct the situation. To learn once more from nature is the demand of the times. Actually, man now stands on the threshold of many new discoveries. All-embracing methods of crop production will be sought. In this lies progress.

Now, nature has designed a simple device by means of which it corrects excesses and deficiencies in soils: HUMUS. This is not merely organic matter, that is, the dead offal of life to be incorporated in the soil, but it is the result of a living process where decaying organic matter is readjusted to life, by the microlife in soil, by enzymes, by roots, etc. It can already be shown that the restoration of humus, the breeding of plants with a view to resistance and nutritious quality can improve the nutritious value.

The question should be asked: Which one-sidedness have we committed that the insect and pest problem has grown out of hand? That the spraying of economic poisons cannot solve the problem is already obvious. To kill–in this case to kill the bug–has never been a method for fostering life. It is an illusion if man believes that the poisoning of bugs will solve the problem. Nature, even in a humble insect, nasty as it may be to our utilitarian concept, has counteracted the poison and developed immunities and resistances. The insect is smarter than man. But since it is an inborn factor of nature, it can be trusted that she will answer to reason and behave as soon as nature’s principles of balance is appealed to. One-sided cultivation methods, especially of monocultures have made a field day for the bugs. This was effected because of a wrong concept of “economic production methods.”

I cannot see an economic advantage in monoculture if, at the same time, poisoning sprays have to be applied (and bought). I cannot see an economic advantage in the overall picture if deficient, unbalanced foods are produced and the money is spent on supplements, pills, the curing of diseases. It is true that this has helped many industries to come into being and it is only fair to transform these interests into a beneficial enterprise, for instance, by erecting composting plants, using all available wastes in order to produce humus. Or to find ways and means for developing non toxic, non-lasting, no residue producing organic sprays. Were all efforts concentrated on the production of a nutritious health food, less supplements would be needed. The sums which are invested in supplements, poison and war could be put to peaceful use.

The sincere reader will admit that the greatest imbalance is caused by human minds, interests and method of thinking. Here the first step of improvement has to be made. If our approach to nature tunes in with the demands and principles of growth, then there will be no difficulty in finding a proper way to amend the present dilemma of pests, deficiencies and malnutrition. To recognize that we have moved too far in the wrong direction is the first step. This is not a crackpot’s idea or faddism but the facts on farms and gardens have already proven that it is possible to produce nutritious crops (and still make a living in doing so) if one follows the principle of balance.

 

References Cited:

1. “The Mineral Nutrition of Corn as Related to its Growth and Culture.” Lewis B. Nelson. Advances in Agronomy–Vol. VIII. Academic Press, Inc., 1956, New York.
2. “Essential Amino Acid Content of Farm Feeds.” Carl M. Lyman, K. A. Kuiker, Fred Hale. Journal of Agricultural and Food Chemistry, December, 1956.
3. “Classification of the Essential Amino Acids Required for Egg Production.” D. Johnson and H. Fisher. Journal of Nutrition, 60, 26-273, 1956.
4. “Effect of Mineral Nutrition on the Content of Free Amino Acids and Amides in Tomato Plants.” T. V. Possingham. Australian Journal Biol. Science–9, 539-51, 1956.
5. “Vitamin C in Nebraska Potatoes.” H. O. Werner. Better Potatoes in Nebraska, 8, Nos. 1, 2-6, 1943. Expt. Sta. Record 95, 282, 1946.
6. Same as 5.
7. “Chemical Methods for Evaluation of Vitamin C (Ascorbic Acid) in Vegetables.” Carlos Alfageme Rubio. Reo Real Acad. Cienc. Exact. Madrid, 34, 370-439. 1940.
8. “The Retention of Vitamin C in Tomato Juice.” L. E. Clifcorn and G. T. Peterson. Continental Can Co. Res. Dept. Bull. No. 12, 1947.
9. “Effect of Blanching and of Frozen Storage of Vegetables on Ascorbic Acid.” E. R. Hartzler, N. B. Guerrant. Food Res. 17 (1) p.,15-23, 1952.
10. “Effect of Soil Condition, Storage and Climatic Factors on the Content of Ascorbic Acid in Belorussian Potato.” D. K. Shapiro. Acad. Nank, 1949. 6, 133-8 (quoted from Chem. Abstracts, 46 (20) 9669, 1952.
11. “Effect of Mineral Fertilizers on the Carotene Content of Plants.” K. Scharrer and R. Burke. Naturwissenschaften, 39, 238-39, 1952.
12. “Tangerines–Their Ascorbic Acid Content and Factors Affecting It.” M. D. Smith, E. Caldwell,, H. Wiseman, Arizona Agri.. Ext. Sta. Mimeo Report No. 72, 1945. Exp. Sta. Record 95, 137 1946.
13. “The Dynamics of Ascorbic Acid Content in Artificially Ripened and Over-Ripened Tomatoes.” B. S. Gologowski. Gigiena i Sanit. 12 No. 9, 1947.
14. “Influence of Light Intensity Upon the Concentration of Thiamine and Riboflavin in Plants.” F. A. Gustafson. Plant Physiol. 23, 373-78, 1948.
15. “Some Effects of Light Intensity, Temperature and Soil Moisture on the Growth of Alfalfa, Red Clover and Birds Foot Trefoil Seedling.” Gge. R. Gist, A. O. Matt. Agronomy Journal Vol. 49, No. 1, January, 1957.
16. “Influence of Seasonal Changes in the Vitamin Content of Some Vegetables in Puerto Rico.” M. del Capella de Fernandez. El Cirsol 2 No. 3, 5-10. 1948.
17. “Seasonal Variation in the Boron Content of Alfalfa.” F. B. Stewart, J. H. Axley, Agronomy Journal, Vol. 48 No. 6, 1956.
18. “Behavior of Manganese in the Soil and the Manganese Cycle.” C. K. Fujimoto Co., Donald Sherman. Soil Sci., 66, 131- 45, 1948.
19. “The Toxicity of Manganese in Strongly Acidic Soils.” A. T. Guellette. Agriculture (Quebec) 7, 319-22, 1950.
20. “Influence of Sodium on Growth and Composition of Ranger Alfalfa.” A. Wallace, St. T. Toth, Firman E. Bear. Soil Sci. 65, 477-86, 1948.
21. “Time and Method of Supplying Calcium As Factors Affecting Production of Peanuts.” J. Fielding Reed, N. C. Brady. J. Am. Soc. Agron. 40, 980-96, 1948.
22. “Some Interrelationship Between Calcium, Magnesium and Potassium in One-Year-Old McIntosh Apple Trees Grown in Sand Culture.” John C. Cain. Proc. Am. Soc. Hort. Sci. 51, 1.12, 1948.
23. “Foliar Diagnosis: Nutritional Factors in Relation to Bacterial Leaf Spot of Peach.” W. Thomas, N. B. Mack, F. N. Fagan. Proc. Am. Soc. Hort. Sc. 51, 183-90.
24. “Variability in Chemical Composition of Seed From Different Portions of the Soyabean Plant.” F. I. Collins, J. L. Carter. Agronomy Journal, Vol. 48, No. 5, 1956.