An Agricultural Testament

by Sir Albert Howard

Chapter 7
Developments of the Indore Process

Grassland Management

TWO very different methods of approach to the problems of grassland management in a country like Great Britain are possible. We can either study the question from the point of view of the present organization of agricultural research in this country or we can bring the world-wide experience of the grass and clover families to bear as if no institutions like the Welsh Plant Breeding Station, the Rowett Institute at Aberdeen, or the Rothamsted Experiment Station -- all of which deal independently with some fragment of the grassland problem -- had ever been contemplated. As the advantages of the fresh eye are many and obvious and as the writer has had a long and extensive first-hand experience of the cultivation of a number of crops belonging to the grass and clover families, the principles underlying grassland management in Great Britain will be considered from a new angle, namely, the conditions which practical experience in the tropics has shown to be necessary for grasses and legumes to express themselves and to tell their own story.

The grass and clover families are widely distributed and cultivated all over the world -- from the tropics to the temperate zones and at all elevations and under every possible set of soil and moisture conditions -- either as separate crops or more often mixed together. Everywhere the equivalent of the short ley, composed of grasses and legumes, is to be found. The successful mixed cultivation of these two groups of plants has been in operation for many centuries: in the Orient they were grown together in suitable combinations long before England emerged from the primitive condition in which the Roman invaders found it -- an island covered for the most part with dense forests and impassable bogs.

What are the essential requirements of the grass and clover families ? The clearest answer to this question is supplied by tropical agriculture; here the growth factors impress themselves on the plant much more definitely and dramatically than they do in a damp temperate island like Great Britain where all such reactions are apt to be very much toned down and even blurred.

Sugar-cane, maize, millets, and the dub grass of India (Cynodon dactylon Pers.) are perhaps the most widely cultivated and the most suitable grasses for this study. Lucerne, san hemp (Crotalaria juncea L.), the cluster bean (Cyamopsis psoralioides D.C.), and the pigeon pea (Cajanus indicus Spreng.) are corresponding examples of the clover family. The last two of these are almost always grown mixed either with millets or maize, very much in the same way as red clover and rye-grass are sown together in Great Britain.

The grass family must first be considered. A detailed account of the cultivation of the sugar-cane will be found in a later chapter. Humus and ample soil aeration, combined with new varieties which suit the improved soil conditions, enable this grass to thrive, to resist disease, and to produce maximum yields and high quality juice without any impoverishment of the soil. Maize behaves in the same way and is perhaps one of our best soil analysts. Any one who attempts to grow this crop without organic matter will begin to understand how vital soil fertility is for the grass family. The requirements of the dub grass in India, one of the most important fodder plants of the tropics, are frequent cultivation and abundance of humus. The response of this species to a combination of humus and soil aeration is even more remarkable than in maize: once these factors are in defect growth stops. The behaviour of dub grass, as will be seen later on, indicates clearly what all grasses the world over need.

Any one who grows lucerne in India under irrigation will court certain failure unless steps are taken to keep the crop constantly supplied with farm-yard manure and the aeration of the surface soil at a high level. When suitable soil conditions are maintained it is possible to harvest twenty or more good crops a year. Once the surface soil is allowed to pack and regular manuring is stopped, a very different result is observed. The number of cuts falls off to three or four a year and the stand rapidly deteriorates. When san hemp is grown for green-manuring or for seed in India satisfactory results are only obtained if the crop is manured with cattle manure or humus. These two leguminous crops do not stand alone. Every member of this group I have grown responds at once to farmyard manure or humus. But all this is not in accordance with theory.

According to the text-books the nodules in the roots of leguminous plants should be relied on to furnish combined nitrogen and this group should not need nitrogenous manure. Practical experience and theory are so wide apart as to suggest that some other factor must be in operation. It was not till January 1938 that I discovered what this factor was. On the Waldemar tea estate in Ceylon I saw a remarkable crop of a green-manure plant -- Crotalaria anagyroides -- growing in soil rich in humus. The root development was exceptional: an examination of the active roots showed that they were heavily infected with mycorrhiza. Other tropical leguminous plants growing in similar soils also exhibited the mycorrhizal association. So did several species of clover collected in France and Great Britain. These results at once suggested the reason why san hemp, lucerne, and many other tropical legumes respond so strikingly to cattle manure. They must all be mycorrhiza-formers.

The fact that leguminous plants and grasses respond to the same factors and that the former group are mycorrhiza-formers suggested that this association would also be found in the grasses. Sugar-cane was first investigated. It proved to be a mycorrhiza-former. The grasses of the meadows and pastures of France and Great Britain were then studied. The herbage of the celebrated meadows of La Crau, between Salon and Arles in Provence, was examined for mycorrhiza in 1938 and again in 1939. In both seasons the roots of the grasses were found to be infected with mycorrhiza. Dr. Levisohn's report on the samples collected in July 1939 reads as follows: 'Sporadic but deep infection of the long and short roots: coarse mycelium inter- and intra-cellular: digestion stages: the products of digestion seem to be translocated rapidly.' In the material from La Crau examined in 1939 the most remarkable example of the mycorrhizal relationship occurred in a species of Taraxacum which formed at least a quarter of the herbage. Here the infection of the inner layers of the long and short roots was 'very widespread and deep. The mycelium is of large diameter, thin-walled with granular contents. Distribution mainly intra-cellular. Digestion showing all stages of disintegration. Root hairs sparsely formed. The mycorrhizal regions of the roots are indicated macroscopically by beading, greater opacity, and slight yellowing of the infected zones' (Levisohn). This suggests that some or all of the so-called weeds of grassland may well play an important role in the transmission of quality from soil to plant and in the nutrition of the animal. Samples of the turf from two well-known farms in England -- Mr. Hosier's land in Wiltshire and Mr. William Kilvert's pastures in Corve Dale in Shropshire -- were then examined. They gave similar results to those of La Crau. Clearly the grass family, like the clover group, are mycorrhiza-formers, a fact which at once explains why both these classes of plants respond so markedly to humus.

This independent approach to the grassland problems of countries like Great Britain has brought out new principles. Grasses and clovers fall into one group as regards nutrition and not, as hitherto thought, into two groups. Both require the same things -- humus and soil aeration. Both are connected with the organic matter in the soil by a living fungous bridge which provides the key to their correct nutrition and therefore to the management of grassland. If this view is a sound one it follows that any agency which will increase the natural formation of humus under the turf of our grasslands will be followed by an improvement in the herbage and by an increase in their stock-carrying capacity. The methods which increase humus formation in the soil must now be considered. The following may be mentioned:

1. The bail system. The most spectacular example of humus manufacture in the soil underneath a pasture is that to be seen on Mr. Hosier's land on the downs near Marlborough. By a stroke of the pen, as it were, he abolished the farm-yard, the cowshed, and the dung-cart in order to counter the fall in prices which followed the Great War. He reacted to adversity in the correct manner: he found it a valuable stimulant in breaking new ground. The cows were fed and made to live out of doors. They were milked in movable bails. Their urine and dung were systematically distributed at little cost over these derelict pastures. The vegetable residues of the herbage came in contact with urine, dung, air, water, and bases. The stage was set for the Indore Process. Mr. Hosier's invisible labour force came into action: the micro-organisms in the soil manufactured a sheet of humus all over the downs: the earthworms distributed it. The roots of the grasses and clovers were soon geared up with this humus by means of the mycorrhizal association. The herbage improved; the stock-carrying capacity of the fields went up by leaps and bounds. Soil fertility accumulated; every five years or so it was cashed in by two or three straw crops; another period under grass followed, and so on. Incidentally the health of the animals also benefited; the prognostications of the neighbourhood (when this audacious innovation started) that the cows and heifers would soon perish through tuberculosis and other diseases have not been fulfilled. (Mr. Hosier has done more than solve a local problem and provide evidence in support of a new theory. His work has drawn attention to the potential value of our downlands -- areas which in Roman and Saxon times supported a large proportion of the population of Great Britain.)

2. The use of basic slag. On many of the heavy soils under grass the limiting factor in humus production is not urine but oxygen. Everything except air is there in abundance for making humus -- vegetable and animal wastes as well as moisture. Under such turf the land always suffers from asphyxiation. The soil dies. This is indicated by the absence of nitrates under such turf. About fifty years ago it was discovered that such pastures could be improved by dressings of basic slag. As this material contains phosphate, and as its use stimulates the clovers, it was assumed that these soils suffered from phosphatic depletion as a result of feeding a constant succession of live stock, each generation of which removes so many pounds of phosphate in their bones. When, however, we examine the turf of a slagged pasture we find that humus formation has taken place. If the application of slag is repeated on these heavy lands after an interval of five or six years there is often no further response. When we apply basic slag to pastures on the chalk there is no result. There is phosphate depletion on strong lands only at one point; none at all on light chalk downs. These results do not hold together; indeed they contradict one another. Are we really dealing with phosphate deficiency in these lands? May not the humus formed after slag is added explain the permanent benefit of this manuring? May it not prove that the effect of slag on heavy soils has been in the first instance a physical one which has improved the aeration, reduced the acidity, and so helped humus manufacture to start? We can begin to answer these questions by studying what happens when the aeration of heavy grassland is improved by an alternative method -- subsoiling.

3. Sub-soiling. The effect of sub-soiling heavy grasslands was described by Sir Bernard Greenwell, Bt. in a paper read to the Farmers' Club on January 30th, 1939, in the following words:

Poor aeration was obviously the limiting factor at Marden Park. Once this was removed humus formation started and the herbage improved. It will be interesting to watch the results of the next stage of this work. Half of a sub-soiled field has been dressed with basic slag and the reaction of the animals is being watched. If they graze the field equally, basic slag is probably having no effect: if the animals prefer the slagged half then this manure is required. (The Marden Park results suggest a further question. Will sub-soiling at 2s. 6d. an acre replace the ploughing- up campaign recently launched by the Ministry of Agriculture for which the State pays £2 an acre? If, as seems likely, the basic slag and ploughing-up subsidies are both unnecessary, a large sum of money will be available for increasing the humus of the soils of Great Britain, the need for which requires no argument.)

4. The cultivation of grassland. One of the recommendations of the Welsh Plant Breeding Station is the partial or complete cultivation of grassland. Partial cultivation is done from the surface by various types of harrow: complete cultivation by the plough. In both cases aeration is improved; the production of humus is stimulated; generally speaking the result obtained is in direct proportion to the degree of cultivation; ploughing-up and reseeding is far better for the grass than mere scarification with harrows. In this work we must carefully distinguish the means and the end. The agency is some form of cultivation; the consequence is always the manufacture of humus.

It will be evident that the various methods by which humus is manufactured under the growing turf itself or by ploughing up and rotting the old turf agree in all respects with what is to be learned from the grasses and the legumes of the tropics. Sir George Stapledon's advice as regards Great Britain is supported by the age-long experience of the agriculture of the East. No stronger backing than this is possible. There is only one grassland problem in the world. It is a simple one. The soil must be brought back to active life. The micro-organisms and earthworms must be supplied with freshly made humus and with air. Varieties of grasses and legumes which respond to improved soil conditions must then be provided. In this way only can the farmers of Great Britain make the most of our green carpet. Our grasslands will then be able to do what Nature does in the forest -- manure themselves.

The order in which improvements should be introduced in grassland management is important. Soil fertility must first be increased so that the grasses and clovers can fully express themselves. Improved varieties should then be selected to suit the new soil conditions. If we study the variety by itself without any reference to the soil and develop higher yielding strains of grasses and clovers for the land as it is now, there is a danger, indeed almost a certainty, that the farmer will be furnished with yet another means of exhausting his soil. The new varieties will have a short life: they will prove to be a boomerang: the last state of the farm will be worse than the first. If, however, the soil conditions are first improved and the system of farming is such that soil fertility is maintained, the plant breeder will be provided with a safe field for his activities. His work will then have a permanent value.

How are we to test the fertility of grassland? Mr. Hosier has supplied the answer. Grassland can be tested for fertility by means of a complete artificial manure. If the soil is really fertile, such a dressing will give no result, because no limiting factor in the shape of shortage of nitrogen, phosphorus, or potash exists. Mr. Hosier has summed up his experience of this matter in a letter dated Marlborough, April 6th, 1938, as follows:

The value of this experience does not end with the testing of soil fertility. It indicates the very high proportion of the grasslands of western Europe which are infertile and which need large volumes of humus to restore their fertility. Most of the fields under grass will respond to artificials. All these are infertile.

The consequences of the improvement of grassland in a country like Great Britain can now be summarized. The land will carry more live stock. The surplus summer grass can be dried for winter feeding. The stored fertility in the pastures can be cashed in at any time in the form of wheat or other cereals. A valuable food reserve in time of war will always be available. As Mr. Hosier has shown, there will be no damage from wireworms when such fertile pastures are broken up and sown with wheat.


Greenwell, Sir Bernard. 'Soil Fertility: The Farm's Capital', Journal of the Farmers' Club, 1939, p. 1.

Hosier, A. J. 'Open-air Dairying', Journal of the Farmers' Club, 1927, p. 103.

Howard, A. Crop Production in India: A Critical Survey of its Problems, Oxford University Press, 1924.

Stapledon, R. G. The Land, Now and To-morrow, London, 1935.

Next: 8. Developments of the Indore Process, Cont.

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