Historical development in soil fertility and plant nutrition
The period in the development of the human raceduring which man began the cultivation of plantsmarks the dawn of agricultureThe exact time is not known, but it was certainly several thousands of years BCUntil then, man was nomadic in his habits
In all ages the growth of plants has interestedthoughtful manThe mystery of the change of an apparentlylifeless seed to a vigorous growing plant neverloses its freshness, and constitutes, indeed, nosmall part of the charm of gardeningThe economic problems are of vitalimportance, and become more and moreurgent as time goes on and populationincreases and their needs become morecomplex
We know now the facts about the needs ofessential nutrients and other factors of plantgrowthThese facts are the result of a few hundredyears of thinking and researchWe thus need to know how this subjectdeveloped historically
Ancient Records• Agriculture started when man became more of a settler than of
a wanderer. Families, clans, and villages developed and the skill of agriculture developed.
• Mesopotamia – situated between Tigris and Euphrates in Iraq- very early civilization
• Writings dating back to 2500 BC mention the fertility of the land
• It is recorded that the yield of Barley was 86x – 300x, i.e., for every unit of seed planted the harvested units were 86 to 300
• Some 2000 years later (500 BC) – Herodotus, the Greek historian- mentions the phenomenal yields obtained by the inhabitants of his land
• Well developed irrigation system and soils of high fertility• Around 300 BC- Theophrastus – richness of the Tigris
alluvium and stated that the water was allowed to remain on the land as long as possible so that large amount of silt may be deposited
• In time man learned that certain soils would fail to produce satisfactory yield when cropped continuously
• The practice of adding animal and vegetable manures to the soil to restore fertility probably developed from such observations – but how and when is not known
• Augeus – a egendary king of Elis, had 3000 oxen in his stable which was not cleaned for 30 years.
• Augeus contracted Hercules to clean the stable out and agreed to give him 10% of the cattle in return
• Hercules is said to have accepted the task by turning the river Alpheus through the stable
• This carried away the accumulated filth and presumably deposited it on the adjacent land – thus enriching the land.
• In the Greek epic poem The Odyssey (Homer ,900-700 BC) the manuring of vineyards by the father of Odysseus is mentioned.
• The manure heap, which would suggest its systematic collection that manuring was an agricultural practice in Greece during the 9 centuries BC
• Xenophon (434-355 BC) observed that “the estate has gone to ruin” because “someone didn’t know it well to manure the land”. And again “ …. there is nothing so good as manure”
• Theoprhastus (372-287 BC) – recommended abundant manuring of thin soils but suggested that rich soils be manured sparingly.
• Bedding in the stall – to absorb more of the urine and bulk and conserve it – humus value of the manure would be increased
• He suggested that plants with high nutrient requirements also had a high water requirement
• The truck gardens and olive groves around Athens were enriched by sewage from the city
• A canal system was used, and there is evidence of device for regulating the flow
• It is believed that sewage was sold to farmers.
• The ancients also fertilized their vineyards and groves with water that contained dissolved manures
• Manures were classified according to their richness or concentration.
• Theophrastus listed the manures in the following order of decreasing value:
human> swine > goat > sheep > cow > oxen > horse• Later, Varro, an early writer on Roman Agriculture, developed a
similar list but rated bird and fowl manure as superior to human excrement:
bird + fowl > human>swine>goat>sheep>cow>oxen>horse• Archilocus (ca. 700 BC) mentioned about the effect that dead
bodies had on increasing the growth of crops.• In Old Testament; in Omar Khayyam etc.
• The value of green manuring crops, particularly legumes, was also soon recognised.
• Theophrastus noted that a bean crop (Vicia faba) was plowed under by the farmers of Thessaly and Macedonia
• He observed that even when thickly sown and large amounts of seeds were produced, the crop enriched the soil
• Xenophon (ca. 400 BC) recommended spring ploughing because “the land is more friable then” and “ the grass turned up is long enough at that season to serve as manure”
• Cato (234-149 BC) suggested that poor vineyard land be interplanted with a crop of acimum. This crop was not allowed to go to seed and ir was turned under.
• He also said that the best leguminous plant for enriching the soil were field beans, lupines and vetch
• Lupine was quite popular with the ancients• Columella listed numerous legume crops, including lupines,
vetch, lentils, chick peas, clover, and alfalfa that were satisfactory for soil improvement
• Virgil (70-19 BC) advocated the application of legumes• The use of what might now be called mineral fertilizers or soil
amendments was not entirely unknown to the ancients• Theophrastus suggested the mixing of different soils as means of
“remedying defects and adding heart to the soil”• This practice may have been beneficial from several standpoints• The addition of fertile soils to infertile soil could lead to increased
fertility, and the practice of mixing one soil with another may have provided better inoculation of legume seed in some fields
• Again, the mixing of coarse textured soils with those of fine textured or vice versa may have caused an improvement in the water and air relations in the soils o0f the fields so treated
• The value of marl was also recognised. • The early dwellers of Aegina dug up marl nd applied it to their
land• The Romans even classified the various liming materials and
recommended that one type be applied to grain and another type to meadow
• Pliny (62-113): lime should be spread thinly on the ground and that one treatment was “sufficient for many years, though not 50”
• Columella also recommended the spreading of marl on a gravely soil and mixing of gravel with a dense calcareous soil
• The value of wood ashes is recorded in the Bible• Both Xenophon and Virgil: burning of stubble to clear fields and
destroy weeds
• Cato: advice to the vine keeper to burn prunings on the spot and to plough in the ashes to enrich the soil
• Pliny: use of lime from lime kilns was excellent for olive groves• Columella: suggested the spreading of ashes or lime on lowland
soils to destroy acidity• Theophrastus and Pliny: saltpetre (KNO3) as useful for
fertilizing plants• Theophrastus reported the use of brine for palm trees• Even as soil scientists of modern times have been searching for
methods of predicting the fitness of soil for production of crops, so did the minds of the early agricultural philosophers and writers turn to such methods
• Virgil: believed that soil that was “blackish and fat under the deep pressed share, and whose mold is loose and crumbling is generally best for corn”. He also wrote about soil characteristics now known as bulk density
• Columella: measure the degree of acidity and salinity of soils• Pliny: bitterness of soils might be detected by the presence of
black and underground herbs• Many of the early writers believed that the color of the soil was
a criterion of its fertility• The general idea was that black soils were fertile and light or
grey soils infertile• Columella disagreed with this view point: black marsh land
soil –infertile; light colored soil from desert area –highly fertile• He felt that such factors as structure, texture and acidity were
for better guides to an estimation of soil fertility
• Much of the early writings regarding soil fertility consisted largely of descriptions of farm practices
• There seems to be little evidence of an experimental approach to farm problems, but many of these manuscripts do reflect a rather keen comprehension of certain of factors now known to affect plant growth.
Soil fertility during the 1st eighteenth century AD• After the decline of Rome there were few contributions to the
development of agriculture until the publication of Opus ruralium commodorum, a collection of local agricultural practices, by Pietro de Crescenzi (1230-1307)
• De crescenzi is referred to by some as the founder of modern agronomy
• He suggested an increase in the rate of manuring over that is use at the time
• Palissy (1563) made the observation that ash content of plants represented the material they had removed from the soil
• Around the beginning of the 17th century Francis Bacon (1561-1624) suggested that the principal nourishment of plants was water, the main purpose of the soil was to keep the plants erect and to protect them from heat and cold and that each plant drew from soil a substance unique for its own particular nourishment
• Bacon also maintained that continued production of the same type of plant on a soil would impoverish it for that particular species
• Jan Baptiste van Helmont (1577-1644) – a Flemish physician and chemist, reported the results of an experiment which he believed proved that water was the sole source of nutrient of plants
• 200 lb soil + water; shielded soil to prevent dust and only rain or d.w was used. A willow shoot weighing 5lb was planted. The plant was grown for 5 years. After 5 years the tree that grew weighed 169 lbs 3 ozs.
• He could account for all but 2 ozs of the 200 lbs of soil• As he added only water – so was the sole source of nutrient• The 2 ozs was attributed to experimental error.• The work was done when nothing was known about mineral
nutrition and photosynthesis
• Van Helmont’s work was repeated several years later by Robert Boyle (1627-1691) of England.
• He confirmed the findings of van Helmont plus one step further• He did the chemical analyses of plant samples and stated that
plants contained salts, spirits, earth and oil, all of which were formed from water.
• About this time, J.R. Glauber (1604-1668), a German chemist, suggested that saltpetre and not water was the “principle of vegetation”
• He collected the salt from soil under the pens of cattle and argued that it must have come from the droppings of these animals.
• He further stated that as the animals ate forage, the saltpetre must have come originally from the plants
• When he applied this salt to plants and observe the large increases in growth it produced, he was convinced that soil fertility and the value of manure were due entirely to saltpetre
• John Mayow (1643-1679), an English chemist, supported the viewpoint of Glauber.
• He estimated the quantities of niter in the soil at various times during the year and found it in its greatest concentration in the spring
• Failing to find any during the summer, he concluded that the saltpetre had been absorbed, or sucked up, by the plants during its rapid growth.
• About 1700, an Englishman John Woodward, grew spearmint in samples of water he had obtained from various sources: rain water, river water, sewage water, and sewage water plus garden mold
• He carefully recorded the weight of the plants at the beginning and at the end of the experiment
• Growth of the spearmint ∞ amount of impurities in the water• His conclusion: terrestrial matter, or earth, rather than water,
was the principle of vegetation • Jethro Tull (1674-1741): Englishman, Oxford educated, ill
health • Soil should be finely pulverised – soil particles were actually
ingested through openings in the plant roots – the pressure cased by the swelling of the growing roots was thought to force this finely divided soil into “the lacteal mouths of the roots” after which it entered the “circulating system” of the plant
• Around 1762, John Wynn Baker, established an experimental farm in England
• The purpose of this was the public exhibition of the results of experiments in agriculture
• Arthur Young (1741-1820): did pot tests to find those substances that would improve the yield of crops
• He grew Barley in sand and used the following materials charcoal, train oil, poultry dung, spirits of wine, niter, gunpowder, pitch, oyster shells and numerous other materials• Some produced plant growth, others did not. He published his
findings in Annals of Agriculture in 46 volumes. • Many of the agricultural writings of the 17th and 18th centuries
reflected the idea that plants were composed of one substance and most workers during this period were searching this principle of vegetation
• Around 1775 Francis Home said that there was not only one principle but probably many
• He included among them air, water, earth, salts, oil, and fire in a fixed state
• He felt that the problem of agriculture were essentially those of nutrition of plants
• He carried out pot experiments to measure the effects of different substances on plant growth and made chemical analyses of plant materials
• The idea that plats contained fire in a fixed state lingered in the minds of man for many years. There was also the belief that organic materials or humus was taken directly by plants and that it constituted their principal nutrient
• This idea persisted down through the years. It was difficult to dispel because the results of chemical analyses had shown that plants and humus contained essentially the same elements
• Between 1770 and 1800 work was done on the effects of vegetation on air that was destined to revolutionise the ideas of the function of plants in the economy of nature
• Joseph Pristley (1775) said that sprigs of mint purified air – plants, instead of affecting the air in the same manner with animal respiration, reverse the effects of breathing, and tends to keep the atmosphere pure and wholesome.
• He had not yet discovered O2, so he could not give precision to his discovery
• Later on, when he discovered O2 and learned how to estimate it, he unfortunately failed to confirm his earlier results as he overlooked the necessity of light
• He was therefore unable to answer Scheele, who had insisted that plants, like animals, vitiate the air
• Jan Ingenhousz (1730-1799) said that purification of air goes on in light only, while vitiation takes place in the darkness
• Jean Senebier (1742-1809), a Swiss natural philosopher and historian, had also arrived at the same result
• He also studied the converse problem – the effect of air on plants
• In 1782 he stated that the increased weight in the van Helmont’s willow tree was the result of fixed air
Progress during the 19th century• Theodore de Saussure (1804) attacked two problems of Senebier
– the effect of air on plants and the origin of salts in plants• He grew plants in air or in known mixtures of air and CO2 and
measured the gas changes and the changes in the plant • De Saussure was able to demonstrate that plants absorbed O2 and
liberated CO2
• In addition, he found that plants would absorb CO2 with the release of O2 in the presence of light
• If, however, plants were kept in an environment free of CO2, they died
• De Saussure concluded that the soil furnishes only a small fraction of the nutrients needed by plants, but he demonstrated that it does supply both ash and nitrogen
• De Saussure effectively dispelled the idea that potash is spontaneously generated by plants and stated further that the plant roots do not behave as a mere filter. Rather the membranes are relatively permeable, allowing for a more rapid entrance of water than of salts
• He also showed the differential absorption of salts and the inconsistency of plant composition, which varies with the nature of the soil and the age of the plant
• De Saussure’s conclusion that the C contained by plants was derived from the air did not meet with immediate acceptance by his colleagues
• Sir Humphrey Davy in 1813, stated that some plants may have received their C from the air but major portion of it was taken through the roots
• He recommended oil as fertilizer because of its high C and H content
• The middle of the 19th to the beginning of the 20th century was a time during which much progress was made in the understanding of plant nutrition and crop fertilization
• Famous among the people during this period was Jean Baptiste Boussingault (1802-1882) – a widely travelled French chemist
• Established a farm in Alsace on which he carried out field plot experiments
• He employed the careful techniques of de Saussure in weighing and analyzing the manures he added to his plots and the crops he harvested
• He maintained a balance sheet that showed how much of the various plant nutrient element came from rain, soil, and air
• He analyzed the composition of his crop during various stages of growth
• He determined that he best rotation was that which produced the largest amound of O.M. in addition to that added in the manure
• Boussingault is considered by some as the father of the field-plot method of experimentation
• Many of the agricultural scientists of this period recognised the value of de Saussure’s observations
• However, there were many adherents to the old humus theory• It was such a natural theory that it was difficult to dispel• Many must have felt then, as some do today, that the decay of
plant and animal materials give rise to products that are best suited for the nutrition of growing plants
• The humus myth was very effectively disposed of by the German chemist Justus von Leibig (1803-1873).
• Since then, only a few scientists have dared to suggest that the C contained in plants comes from any source other than CO2.
• Leibig made the following statement:
• Most of the carbon in plants comes from the CO2 of the atmosphere
• H2 and O2 comes from H2O• The alkaline metals are needed for the neutralization of acids
formed by plants as a result of their metabolic activities• Phosphates are necessary for seed formation• Plants absorb anything indiscriminately from the soil but excrete
from their roots those materials that are nonessential• Acetic acid is excreted by roots• NH4
+ form of N is the one absorbed and plants might obtain this compound from soil, manure, or air
• Not all of Leibig’s ideas were of course not correct• Leibig firmly believed that by analysing the plant and studying the
elements contained one could formulate a set of fertilizer recommendations based on these analyses
• It was also his opinion that the growth of plants was proportional to the amount of mineral substances available in the fertilizer
• He eventually developed the law of the minimum ; the growth of plants is limited by the plant nutrient element present in the smallest quantity, all others being present in adequate amounts
• Leibig manufactured a fertilizer on his ideas of plant nutrition• The formulation of the mixture was perfectly sound• However, he made the mistake of fusing the phosphate and
potash salts with lime, as result the fgertilizer was a complete failure
• Leibig is considerd as the father of agricuktural chemistry
• J.B.Lawes and J.H.Gibert established in 1843 n agricultural esperiment station at Rothamsted, Herpenden, Herts, England
• Work here was carried out along the same line as tht carried out earlier by Boussingault in France
• Lawes and Gilbert did not believe that all of the maxims set down by Leibig were correct
• 12 years after the founding of the station they settled the folowing points:
1. Crops require both P and K, but the composition of the plant ash is no measurement of the amounts of these constituents required by the plant
2. Nonlegume crops require a supply of nitrogen. Without this element, no growth will be obtained, regardless of the quantities of P and K present
3. Nitrate and ammonium salts being lmost equally good. The amount of ammonium nitrogen obtainable from atmosphere is insufficient for the needs of crops
4. Leguminous crops behave abnormally5. Soil fertility could be maintained for some years by means of
chemical fertilizers6. The beneficial effect of fallow lies in the increase in the availabilityof
N compounds in soil• The water cultures of Knop (1861) and other plant physiologists
showed conclusively that K, Mg, Ca, Fe, P, along with S, C, H, N and O are all necessary for plant life
• For a long time, farmers were reluctant to believe that fertility could be maintained by the use of chemical fertilizers alone
• The early work at Rothamsted proved conclusively that it could be done
• In 1852, Thomas Way in England first demonstrated the phenomenon of cation exchange from the observation that a Yorkshire farmer was able to reduce ammonia loss from manure by the addition of soil. However, its tremendous significance was not immediately recognised.
• George Ville (during 1867 and 1874-75)- a Frenchman of Viencennes, recognised the value of some of the early results from the Rothamsted experiments
• He maintained that the use of chemical fertilizers was the only method of supporting soil fertility
• He made recommendations for the fertilization of crops based on the results of field trials
• He drew up a simple scheme of plot tests that could be used by farmers to determine for themselves just what fertilizers were needed for their crops
• Ville’s view that chemical fertilizers were always better and cheaper than dung is too narrow and did not survive
• The problem of soil and plant nitrogen remained unsolved• Several workers had observed the unusual behaviour of legumes• In some instances they grew well in the absence of added N, whereas
in others no growth was obtained• Nonlegumes, on the other hand always failed to grow when there was
insufficient nitrogen in the soil• In 1878 some light was thrown on the confusion by two French
bacteriologists – Thodore Schloessing and Alfred Műntz• They purified sewage water by passing it through a filter made of
sand and liume stone – analysed the filtrate periodically for 28 days• Only NH4 – N was detected during this period
• At the end of this time NO3 began to appear in the filtrate
• They observed that the production of NO3 could be stopped by adding chloroform and that it could be started again by adding a little fresh sewage water
• They concluded that nitrification was the result of bacterial action
• Robert Warrington during 1878-1891, applied the results of these experiments to soil processes
• He showed that nitrification could be stopped by CS2 and chloroform and that it could be started again by adding a small amount of unsterilized soil
• He also demonstrated that the reaction was a two step phenomenon, the NH3 first being converted to NO2 and then to NO3
• He, however, failed to isolate the organisms by using gelatin method
• The organism was later isolated by S. Winogradsky in 1890 on silica gel plate
• As to the erratic behaviour of legumes with respect to N, the two Germans, Hellriegel and Wifarth in 1866 concluded that bacteria must be present in the roots of legume roots
• These organisms were believed to assimilate gaseous N from the atmosphere and to convert it to form that could be used by higher plants
• The organism was isolated by M.W. Beijerinck (1890) and named it Bacillus radicicola, later named as rhizobium and now known as Bradyrhizobium
• The general conclusion that bacteria are the real makers of plant food in soil, and are, therefore, essential to the growth of all plants, was developed by E. Wollny and M. Berthelott (1884)
• It was supposed to be proved by E.Laurent’s (1886) experiment• Further investigation of soil problems has shown that they are
more complex than was first supposed• Soils can no longer satisfactorily be divided into a few simple
groups: sands, clays, loams etc., according to their particle size; nor an alteration be confined to the surface layer
• It is necessary to take their history• Soil properties as enunciated by the Russian investigator V V
Dokuchaev (1883) are dependent on factors like climate, vegetation besides parent materials.
• This ushered the study of soil as a living entity and other aspects of soil uses
• Thus we study any soil on pedologic and edaphologic aspects• The advancement soil studies in the 20th and 21st centuries have
been tremendous• Soil chemical processes, physical processes, biochemical and
microbiological are now studied in both destructive as well as non-destructive methods
• Soils are now classed as per their suitability to specificcrop production or other uses
