Sir Albert Howard in India

By Louise E. Howard

Chapter 3
Soil Aeration and Irrigation

A New Subject

Soils in the tropics are successively affected by burning sun and by heavy monsoon rainfall. The seasonal rise and fall of the subsoil water is another factor; the variations of levels greatly exceed the variations in temperate climates. The importance becomes obvious of paying the utmost attention to such factors, and it follows beyond dispute that the relation of the plant, especially of the plant roots, to its environment must be fully studied.

In dealing with these facts Sir Albert Howard had to be a pioneer. The subject was new to scientists. The soil investigator, from the days of Liebig trained almost wholly in soil chemistry, was, it is true, beginning to turn to soil physics. As Sir Albert later took occasion to point out, the most important aspect of the physical condition of the soil is that connected with the air in the soil. (Agricultural Journal of India, Vol. XIII, Part III, 1918, pp. 416-17.) It was on the vital question of introducing air into the soil for the use of the plant that his interest was focused. In other words, the physical aspects of soil texture were only a bridge to the biological aspect, i.e. to the needs of the growing plant in its call on the gaseous contents of the soil as material for its life processes. The plant rootlets are in permanent need of the oxygen dissolved in the film of water coating the loose soil particles, and this is lost if there is not plenty of crumb structure giving pore space; without such a supply the rootlets cannot breathe; the plant perishes. The increasing attention which Sir Albert gave year by year to the problem of soil ventilation proved an illuminating first phase in shaping his ultimate views on the requirements of plants. In his imagination the plant's need of air took precedence even over its need of water.

The years of intense work up to 1913 were the years of the experimental demonstration of the ideas proving the great need of securing soil aeration in India. In these years the Pusa system of the grading and shaping of fields, applied also at Quetta and subsequently with pronounced success at Indore, was perfected; an initial problem of aeration was solved on principles which could scarcely have been bettered. In 1914 appeared some observations on the need for aeration in the application of green-manures, while a full presentation of the conclusions to be drawn from all experiments was first published in the years 1914, 1915, and 1916, culminating in a lecture in 1916 to the Board of Agriculture at Pusa in which some startling suggestions were presented. The facts brought forward rested throughout on a double series of experiments, carried out alternately on the humid plains of Pusa and on the arid desert soils of Quetta, where, however, the work tended rather to illustrate the allied subject of irrigation. The two-fold basis had been widened by notes taken in the course of tours to other parts of India; thus the insight gathered during the nine years since the start of the experiments in 1905 ended in a comprehensive view of the whole problem.

The aims were throughout practical. The Howards realized that there was, indeed, an unexplored scientific problem awaiting investigation in the sorting out of the many intricate and still unknown interchanges in the gaseous contents of the soil. At that time no study had yet been made of these phenomena in India; even such a simple truth as that rain is superior to other waterings because of its dissolved oxygen supply was new. (Agricultural Journal of India, loc. cit., p. 424.) Much work would certainly have to be done, but there was no need to wait for it. By making use of field observations it was quite possible to advance in practice. Great improvements could be quickly effected by obvious methods within the reach of all the best cultivators. On this question, as on so many others, work was strictly adjusted both to the needs and to the capacities of the Indian peasant.

The Natural Soil Conditions

Broadly speaking, there are two quite distinct types of soil in India, the alluvium of the Indo-Gangetic plain, stretching right across the peninsula, and the black soils south of this belt. Pusa was situated on the Indo-Gangetic alluvium, and it was here that the problem of soil aeration was first brought home to the Howards.

But this 'vast oxygen filter' could only operate as such if the surface of the soil was kept open. There are innumerable references in the reports on the Pusa work to the crust which was so apt to form on these soils, and which, indeed, was known by a special term, the papri.

How necessary it was at all times not to interfere with aeration from the surface downwards was shown in the course of the experimental work itself.

If the impact of the human foot, but more especially of the heavy rains, on the surface of the soil constituted a problem to be dealt with by continual cultivation, in which the peasants were, as a rule, masters, there was another danger in the rise of the subsoil waters.

On the black soils, south of the alluvial plains, the conditions were quite different. There was a natural aeration process which was effective, though the continuation of the monsoon might bring risks.

Finally, the Howards had the advantage of being able to compare both sets of conditions with the widely different climate at Quetta, contrasting the moist plains with the dry desert: actually the aeration problem proved the same.

The Erosion Effects of the Monsoon

Such were the soil conditions. But they could not be understood except in the light of the tremendous effects of natural precipitation taking the form of the recurring monsoon.

The intense cry from the heart of the people for the longed for rains easily led them astray. It was part of Sir Albert Howard's work to point out that water itself could be, indeed, had been for centuries, a menace.

The Water-logging of Fields

To forestall these evils the population had from ancient times used systems of embankment.

Of the two connected evils, actual soil loss and waterlogging, the more persistent damage was to be attributed to the latter, which thus outweighed even the evil of the washing down of soils.

Waterlogging meant depriving the plant root of air, and that, in the opinion of the Howards, was the ultimate sin. The following short passage may be some explanation of Sir Albert Howard's criticisms in later years of official agricultural research. Certainly the folly of carrying out advanced variety trials without first mastering the elementary lesson of how to manage the soil which was to support the crop would have struck any intelligent observer.

The Remedy: the Shaping of Fields

What was to be the answer to these evils, which amounted to a kind of endemic disease of the soil, going back for centuries? The first thing which the two research workers had to do, if they did not wish to sink to the unfortunate level of their fellow workers of the old manurial trial plots just referred to, was to use their eyes. There were natural indications, full of significance, which could be noted at Pusa and could lead in the right direction.

The Indian peasants were not without their own faculty of observation. They had evolved more than one clever device. It has already been stated that they seemed to be born with an inherited 'papri-breaking sense'. They were ingenious also in taking advantage of the better aeration to be found on the borders of irrigated field, what was called 'the edge effect'. Plants thus located could reach a supply of air through the earth embankment and grew much better than those in the centre of a plot where the soil was waterlogged. It had become habitual practice for the ryots, when requiring patwa (Hibiscus cannabinus L.) or sann (Crotalaria juncea L.) for seed, never to sow in field patches, but always to have a few plants on the edges of the field, which were often slightly raised; experience had shown that only in this way would these plants come to maturity. It was interesting that Europeans, growing vegetables on the black soils, had copied this idea of sowing round the edges of plots in order to escape waterlogging.

Perhaps even more important was the widespread knowledge and use of the deep-rooting plant as a natural soil aerator. Many plants could act in this way by the thrusting nature of their root systems, rahar (Cajanus indicus) being one of the best examples. It was a well-known practice to grow rahar before tobacco, a crop requiring especially good aeration, and also usual to breakup soured airless packed soil under rough grass land (perti) by means of a first crop of the sweet potato, which managed to thrive in conditions which would choke other crops and whose swelling roots, acting 'like a mild explosive', shattered the soil for the next crop. In the Quetta valley local knowledge dictated the use of busunduk (Sophora alopecuroides), a common weed, among the peach trees or melons; this was a plant provided with thick underground stems bursting open the subsoil in all directions and with shoots coming to the surface and letting in extra air; where this was found there was seldom yellowing of the peach; it could well be called 'the subsoil plough of the Quetta valley'. Alternatively shaftal(Persian clover), a valuable fodder, could be cultivated and ploughed in, the organic matter thus added assisting the excellent aeration effects of the deep taproot and numerous laterals, which broke up the soil in all directions. (It was on a similar experience of the soil shattering work of local deep-rooting crops that Elliot, who had spent many years in the East, based his well-known Clifton Park system of using the deep-rooting crop as a natural aerator and fertilizer.)

Such practices were only palliatives for soil conditions which had slowly degenerated over the centuries. Something more definite was needed. The remedy was found by adopting the very old principle of 'divide and rule'. The rainfall was to be dealt with field by field, and in that way mastered: the monsoon was to be 'put in harness'.

A new system was devised of the separate contouring and shaping of each field, so that it could absorb the maximum amount of water on the spot. This was something quite different from the ordinary practice of terracing. Each field was independently treated, sloped from the centre very gently downwards towards the edges to end in grass-covered drainage ditches. Thus every small area was trained to deal with its own rainfall and was also protected from the run-off from other areas, which is what is meant by the words 'divide and rule'. The idea seems to have been original, but a journey to north and central Italy while on leave in 1913 showed an almost identical system in use, and a few improvements were borrowed from what was seen in that country. (Report of the Imperial Economic Botanist for the Year 1912-13, pp. 17-18.)

There was no other piece of work done by the Howards in the early years at Pusa of greater usefulness than this device of the draining and shaping of fields. It was a straightforward practical reform which could be brought to the notice of the Board of Agriculture, when addressed at Pusa in 1916, as within the capacity of the peasants, capable of being carried out with existing tools, yet leading to immense benefits of a permanent kind.

The Use of Potsherds in Green-manuring

An entirely different attack on the problem of aeration was made after the fielding system had become well established. The new advance was made in an almost fortuitous way; yet not really so, for it came about, as did so much else, as a result of Sir Albert's acute and penetrating observation. It was in 1915, the year previous to his address to the Board of Agriculture, that in the course of one of his journeys Sir Albert noticed an effect near Jais in Oudh which led to an explanation of the aerating effects of using potsherds or brick to dress the land. This was an Indian practice, not an Experiment Station suggestion. In view of the revival of stone mulching in horticulture, this ancient practice is of interest.

A large sample of the irrigation water was sent for analysis to the relevant department at Pusa and was found to be exceedingly rich both in nitrates and in dissolved oxygen. (Potassium nitrate 34.57, sodium nitrate 16.55, dissolved oxygen 0.725, as contrasted with nil to 0.036 for both nitrates and 0.067 to 0. 153 of oxygen in Pusa water.)

It is not quite clear exactly at what point actual experiments in dressing soil with potsherds (thikra) were begun at Pusa, but they are referred to in several papers about this time. The rate of application was fifty tons of broken tiles to the acre, mixed with the upper six inches of soil. The results in conjunction with green-manuring are said to be 'exceedingly striking'. It was, in fact, in sorting out the erratic effects of green-manuring that the use of thikrawas to prove illuminating; the success or failure of green-manuring was found, like so much else connected with the soil, to depend on aeration.

Green-manuring is important in India because animal manure is so insufficient in quantity. But many failures in using green-manures, especially on the alluvium, were registered. It was not realized that the green-crop, while growing, used up the available oxygen supply in the soil and also released a large quantity of carbon dioxide; when subsequently ploughed in any remaining oxygen would be called on to assist decay. The crop thereupon sown, deprived of oxygen and choked by the presence of the carbon dioxide, instead of benefiting from the manurial operation, starved. This was less likely to happen in light porous soils where air could freely enter, such soils as those of North Germany where the original green-manuring experiments of Schultz-Lupitz had been carried out. But on the compacted alluvium of India, the lack of air was fatal for the growing of the succeeding crop.

That extra aeration, or special attention to aeration, was essential in a green-manuring operation had already been established in a special experiment on three tobacco plots green-manured with sann at Pusa in 1913. Green-manuring was carried out on successive dates in July and August and across all three plots a strip was subsoiled to a depth of twelve inches two days before the tobacco was transplanted at the end of September. The effect of the extra air supply given by the subsoiling was plain to see on all three plots; the first plot, where the green-manuring had been earliest carried out, gave the best results; the worst results were found where the green-manuring had been done last, thus showing that the decay of the green-manure was a process competitive with that of the growth of the crop.

The only cure was aeration and the Pusa experiments with potsherds were sufficient proof.

Provided, then, that soil aeration could be made 'copious' by surface drainage of the fields on the Pusa system, by subsoiling before sowing, and above all by the potsherd dressing, complete decay, in good time, of the green-manure could be ensured and its nitrification. This was the explanation of why the Jais water was so rich in nitrates. It was also found rich in potash, which Sir Albert attributes to the fact that much wood and cow-dung were burnt for fuel in rural centres. Such potash, together with phosphates, was, in the presence of adequate oxygen, collected by the soil fungi for the use of the higher plants; the cycle was thus complete.

Cheap and simple devices always appealed to Sir Albert. In the Indian potsherd he had something after his own heart.

The theme of the vital need for allowing air to penetrate into the soil is repeated like a kind of leitmotif in almost every paper published about this time, 1910-16. From a very early date the Howards were impressed by the importance of the problem. Their field work was always directed to take it into account, and lysimeter experiments bore out the field work. Every trial told the same story, that the plant root needed air, but that air was not always easy to conduct into the soils of India by reason alike of the violent impact of the monsoon rains and the rise of the subsoil waters; unless prevented there would be the evil of waterlogging, to drown the plant roots, or the other evil of compaction of the surface, to choke off the air. On wheat, for instance, the verdict could not have been more decided: 'After growing wheat in Bihar for nine years, we are convinced of the importance of aeration for this crop and equally convinced that over-consolidation (of the soil) from any cause is very harmful.' A similar verdict was applicable to indigo and tobacco, to lucerne, gram, grass, and vegetables, while in the growing of fruit trees, both at Pusa and at Quetta, the aeration factor had given rise to effects of really startling definiteness. (See Chapter 5.) All results seemed to run together and even slight causes to lead to almost irreparable damage, so that to the general judgment that 'proper relations between air and water in the soil' are a necessary prerequisite for growing the best crops in Indian conditions could be added the stranger dictum that 'water, when it excludes air from the roots, acts as if it were a poison to crops'.

Irrigation: the Furrow System

This pre-occupation with the damage which water can bring was a view unusual in India, where water is valued as one of the most precious of commodities. The benefits conferred on India by the great canal systems built by the British administration, more especially in the Punjab, are a matter of common knowledge; vast new areas of land were opened up for settlement. Sir Albert was interested in the general theory of irrigation systems; as an agricultural botanist, he judged the benefits by the growth of crops and did not always agree that these had been as permanently useful as was supposed. There were risks involved, which were apt to be overlooked.

In local practice at Pusa an error was met with at the outset. This had to be put right, which was not difficult, but he might have argued that with so experienced a population it ought not to have occurred. However, the growing of fruit in India was always rather careless and deficient, possibly because fruit is never an essential subsistence crop. In arranging to water the peaches, loquats, almonds, etc., planted on arrival at Pusa -- these plantings were almost the first of the experiments -- he found a system in use among the local cultivators which might be called a small basin system. Shallow circular holes were excavated round the stems of the trees, connected by means of small trenches, and the water flooded in. Not only did this flooding invite collar-rot and the general waterlogging of young trees, but the water failed to reach far enough to benefit the further growing root-tips of the older trees; meanwhile manuring and drainage were interfered with in the monsoon.

It was therefore better to replace the basins by shallow rings corresponding to the outer spread of the branches. The water, conducted by a trench parallel to the lines of trees, was sent first into the furthest ring and after that into the nearer ones, one after the other, each inlet to a ring being controlled by a small earthen dam. This simple alteration carried a number of advantages. No more water was used: it reached the growing rootlets of the trees: there was no waterlogging. During the monsoon the rings were filled in to be re-made the following season, but the parallel trenches were left and acted as good drainage canals. This system was being adopted in the United States. (Furrow irrigation was so new in India that when introduced with pruning by Dr. Martin-Leake at Cawnpore for oranges he was challenged by the buyers of the crop in flower to offer compensation for expected loss of harvest; in the event the weight of the crop was so great that it nearly broke the branches.)

An adaptation of this same device of furrow irrigation was very successful in preventing losses in the transplanting of tobacco.

It is interesting to see in this example how a mistake in practice had opened the door to insect attack, and how easily such attack was afterwards prevented by attending to the state of the soil.

The Saving of Irrigation Water in Wheat Growing

Armed with these successes at Pusa the Howards proceeded to Quetta for the summers from 1910 onwards. There they found an elaborate system of irrigation applied to the growing of wheat.

There were, it is true, other methods of growing wheat without irrigation, on dry farming principles, but the crop was always precarious, and the best yields were undoubtedly obtained under irrigation.

One could have supposed that scientific advice would take the direction of encouraging the application of water and of endeavouring to increase the scope and intensity of irrigation practices. This did not commend itself to the Howards. Instead, the problem was viewed from a revolutionary aspect, the previous investigations on soil aeration being the red line guiding their ideas.

These observations convinced Sir Albert that there was much that was wrong. Heavy watering disadvantageously prolonged the period of growth, delaying ripening, induced too great a proportion of straw to grain and a superficial rather than a deep-rooting system; above all, there was a criminal waste of the precious water itself, especially in view of the fact that the cultivators seemed quite ignorant of the uses of a dry mulch in preventing evaporation.

The experiments were conducted from 1912 to 1915. Some fair results were obtained in the first year by the use of the harrow to induce a dry mulch on an unirrigated crop, but this had to be discontinued as the wheat shot up and the late rains of March, April, and May formed a distinct surface crust allowing evaporation, with bad effects on the ripening of the ear, as described above. Some additional moisture was clearly necessary, but it was a triumph to prove that the needed supply could be given by means, not of seven, but of a single irrigation.

This difficulty was overcome by the introduction of a spring-tine cultivator followed by the beam. A pair of cattle could cover at least three acres in a day. Ploughing and sowing would follow, and the young crop was then lever-harrowed with a pair of cheap Canadian lever-harrows drawn by a pair of bullocks. By sloping the tines backwards this could be repeated several times. All this was well within the means of the local inhabitants. In the second year of these experiments (1915) the crop of the Experiment Station, thus treated, ripened about a month before the local crop and was far less affected by yellow rust; the full chaff colour, hardly ever seen in the country crop, was developed. The average yield for this and the preceding season was 17 maunds 29 seers per acre, or 4-1/4 maunds above the average yielded with six or seven irrigations (unmanured land in both cases).

These figures applied only to the desert. But, as had been stated, there was much land lying fallow through sheer lack of water, so that the contention that a saving of waterings would mean distribution of the water thus saved to other land, and therefore much larger harvests, is true. The description ends with a brief statement that the Experiment Station work had been carried out by an Indian staff on written directions only, sent from Pusa, thus proving that the innovations suggested were not only within the financial means of the zamindars, but also within their intelligence and skill.

There was really no need to go further, and the sufficiently dramatic results, when put before the Board of Agriculture at Pusa in 1916 and at Poona in 1917, had already resulted in three resolutions of the Board and even a recommendation proposing a special Experimental Station to enquire into the question. The Howards were clearly justified in speaking with authority when they demanded an overhaul of the systems governing the use of irrigation water and its payment.

The arrangements governing the distribution of irrigation waters were, in fact, revised by the Baluchistan Administration in consequence of the representations made. These were subsequently confirmed by three further years' work at Quetta itself, when excellent yields of wheat were obtained with a great saving of water. Similar results were arrived at in the Punjab, in Sind, and the United Provinces, while at Shabjananpur actually over thirty-three maunds were on one occasion reaped (1918-19). Elsewhere, the opposite effect, namely, the deterioration of the harvest by using too much water, was easily established.

The Supreme Importance of the Air Supply to Plants

The risks associated with over-irrigation directed Sir Albert's attention to the world-wide problem of alkali lands. The occurrence of these lands is much dreaded in India. The question was first discussed by him in a book published in 1924 (Crop Production in India, pp. 43-50), but as a further long discussion is available to all in An Agricultural Testament (An Agricultural Testament, pp. 147-55), it is not necessary to go into detail here. Briefly, the excess of sodium salts which kills plant growth is not to be attributed to lack of rainfall but to lack of air and is often brought about by perennial irrigation: once again, the four factors, soil, air, water, plant, are seen to be one problem. But if lack of aeration is the real cause of the degeneration of soils into the alkali condition, then not the washing out of the salts, which in any case is usually impossible in practice, but the opening up of the surface and the subsoil to the air by any and every means will be the only efficient remedy.

Thus in a curious and unexpected way drainage, irrigation, alkali lands, were found to be nothing but illustrations of the aeration problem. The results of surface drainage alone at Pusa had been staggering.

If measures for the saving of irrigation water could be added to the field system evolved at Pusa it would seem that 'enormous progress' would be possible, and not merely in India, but in many other countries.

The subject of soil aeration eventually led in a direct way to the subject of disease. The idea that faulty soil aeration invites sickliness and failure in the plant runs through many papers, and is expressly discussed as part of the Presidential Address to the Indian Science Congress in 1926, by which time the argument had become definite. Aeration again plays its part in a consideration of the final topic, the laws governing decay. It is stressed again and again that the mixed heaps of organic waste must, if they are to break down naturally, be provided with ample air for oxidation. At a later stage, on his return to Europe, renewed aeration, by means of subsoiling, was ardently advocated by Sir Albert for English soils, as a remedy for the subsoil pans, which he strongly suspected to exist far more frequently than either the farmers or the scientists in Great Britain were ready to admit. Indeed, the immense role played by aeration in all Eastern cultivation made him impatient of the Western scientist's slowness to accept the view that plant growth must always be discussed in relation to environment: nothing in the plant could be considered by itself, it must necessarily be related to the surrounding conditions. Of these the first, even more important than water, was the air.

What was the explanation? What were the values derived from the air which made its presence in abundance so indispensable to all growth, so much so that the effects of any interference with the air supply could instantly be seen in the plant? Already in the important lecture delivered before the Board of Agriculture in 1916, when the results of the Quetta aeration experiments were being presented, Sir Albert put his finger on the crucial point. He was arguing on the subject of manuring, and in the light of his later views on artificial manures his words are prophetic. The passage is of great interest.


Agric. Journ. of India, Vol. III, Part III, July 1908: 'Furrow irrigation'.    

Ibid., Vol. IX, Part II, April 1914: 'Notes on Drainage and Green-Manuring'.

Indian Tea Association Scientific Journal, 1014: 'Soil Denudation by Rainfall and Drainage and Conservation of Soil Moisture.'

Bulletin No. 52 of the Agric. Research Institute, Pusa, 1915: 'Soil Ventilation'.

Bulletin No. 53 of the Agric. Research Institute, Pusa, 1915: 'Soil Erosion and Surface Drainage'.

Bulletin No. 4 of the Fruit Experiment Station, Quetta, 1915: 'The Saving of Irrigation Water in Wheat Growing' (reprinted in Agric. Journ. of India, Vol. XI, Part I, Jan. 1916).

Bulletin No. 61 of the Agric. Research Institute, Pusa, 1916: 'Soil Aeration in Agriculture'.

Agric. Journ. of India, Special Indian Science Congress No., 1916: 'The Importance of Soil Ventilation on the Alluvium'.

Ibid., Vol. XI, Part III, July 1916: 'The Manurial Value of Potsherds'.

Bulletin No. 7 of the Fruit Experiment Station, Quetta, 1916: 'The Irrigation of Alluvial Soils' (reprinted in Agric. Journ. of India, Vol. XII, Part II, April 1917).

Agric. Journ. of India, Special Indian Science Congress No., 1917: 'The Agricultural Development of North-west India'.

The Indian Forester, 1918: 'Recent Investigations on Soil Aeration with Special Reference to Agriculture' (reprinted in Agric. Journ. of India, Vol. XIII, Part III, July 1918).

Agric. Journ. of India, Special Indian Science Congress No., 1919: 'Drainage and Crop Production in India'.

Bulletin No. 11 of the Fruit ExperimentStation, Quetta, 1919: 'The Agricultural Development of Baluchistan, Section II, Agriculture' (reprinted as Bulletin No. 119 of the Agric. Research Institute, Pusa, 1921).

Agric. Journ. of India, Vol. XX, Part VI, Nov. 1925: 'The Origin of Alkali Land'.  

Crop Production in India, 1924: Part I, 'The Soil', pp. 11-49.

Indian Agriculture, 1927, Ch. II: 'The Factors underlying Production, pp. 13-16. (Extent of erosion in India.)

The Application of Science to Crop Production, 1929, pp. 43-6. (Irrigation by wells.)

Next: 4. Various Crops and Various Problems

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