ENABLE

In this 15^th issue of the Newsletter you will find some thought-provoking material, which I hope will stir discussion and provoke letters and articles for the next issue!

Both the beginning and the end of this issue are concerned with soil formation – from the top downwards, whether by tillage, or organic activity on organic materials, or both. Will Critchley’s Letter to the Editor contains an extract from his PhD thesis regarding soil formation in Indonesia; my photo from Malawi at the end (if it prints-out acceptably) illustrates my inversion of thinking on the subject. A quotation from Richard Feynman legitimises heretical suggestions such as this. What are your own thoughts on the matter?

At the AGM in London on 28^th June, questions were asked about the ‘A-Ha!’ Factor and why better land husbandry is needed. It got us thinking. Although these questions were not adequately answered at the meeting, they have elicited two responses, which are included as articles here.

A translation of an article about easy and difficult conditions for success with direct-drilling / no-till farming / conservation agriculture in Brazil indicates that weed-control may be more difficult on old ‘tired’ land than

on that newly-opened from formerly-undisturbed vegetation. It implies the

need for dedicated research on realistic options in weed-control for no-till systems on land that has been in cultivation for many years. The article mentions the use of specific species in rotations with allelopathic effects in suppressing weeds.

There is an article on sources of information on better land husbandry, which provides a lead-in, rather than any attempt to provide a comprehensive list of relevant references. Please contact me if you would like some more detail.

I have taken the liberty of taking an extract from a pre-1982 paper by Dr Geoff Downes to show the source of the phrase ‘Prolonging the life of resources’, a concept clearly allied with ‘sustainability’ and ‘husbandry’.

Notices of three useful books, and the new website of the recent global program on Direct Sowing, Mulch-Based systems and Conservation Agriculture, are included on the Bookshelf. If the photos are satisfactory, Part 2 of the boat-rocker of the Think-pic 2 (previous issue) precedes Think-Pic 3. If not, you will find a different diagram at the end. Take time to consider Richard Feynman’s thoughts on the scientific method, and apply them to the implications of Think-pic 2 of the previous issue.

Good reading! The Editor.

Congratulations on the last ENABLE (no.14) which I found most stimulating. May I add something to the debate on soil formation / soil as a self-renewing resource? The following piece – while not exactly approaching the issue from the same angle as your article (pp.4-9) – arrives at a similar conclusion: farmers are often busy forming soil at a higher rate than we assume. In this extract from my thesis I discuss tolerable soil loss in the context of [bench]terracing – with especial reference to Java[1].

“How much surface erosion is essentially benign, and at what level does it become malignant? This is an important question, which is poorly answered. Obviously, in the current context, we need to have some idea of whether terraces reduce erosion to an ‘acceptable’ level. High rates of surface erosion cause a reduction in soil productivity for various reasons including selective removal of fine nutrient-rich particles and organic matter (leading to the phenomenon of enrichment of sediment compared with source), reduction in rooting depth and destruction of soil structure (Stocking, 1984). There are negative downstream impacts also in rivers, reservoirs, irrigation schemes, and towns commanded by tropical steeplands. The focus here will be on the on-site impact of (surface) soil erosion, as that is where the economic damage is generally greatest (Doolette and Magrath, 1990). Soil loss tolerance levels (‘T-values’) denote the theoretical ‘maximum level of soil erosion that will permit a high level of crop productivity to be sustained economically and indefinitely’ (Wischmeier and Smith, 1978). What is extraordinary is that the T-value most frequently quoted and applied as a standard (11.2 t/ha/year) is simply the general maximum calculated for use in the USA when the T-value was first developed (Kral, 1982). It is applied, apparently, without any consideration of its local relevance, though it has to be said that the knowledge base for independent development of T-values for the tropical steeplands is extremely weak.

Johnson (1987) even questions the usefulness of T-values at all due to the ‘faulty premises’ on which they are founded. The fundamental weakness of T-values is that they are based on rates of pedogenesis: the development of soil itself from parent material. This is usually a topic of authoritative sounding, pessimistic statements. In fact little is known about this side of the ‘erosion equation’ generally, and even less about the specific situation in tropical soils under invasive cultivation into the soil profile, as occurs under terrace systems. Data on the subject are scarce (Walling, 1989; Hudson, 1992) – in contrast to the plethora of erosion data. Johnson (1987) points out that many of the published references to soil formation are traceable to two sources (one a ‘guess’ and the other a ‘speculative deduction’). General global rates quoted range from as low as 0.01 mm/year (0.13 t/ha/year, assuming an average bulk density of 1.3 t/m³) to 7.7 mm/year (90 t/ha/year) in exceptional cases (Morgan, 1995). Zachar (1982) quotes a global figure of 0.1 mm/year (1.3 t/ha/year). Walling (1989) takes the ‘frequently cited’ figure of 0.025 mm/year (0.3 t/ha/year) as a guideline. While Stocking (1994) points out that the rate of formation of topsoil ‘can easily reach ten times the formation of the subsoil’ (5-10 t/ha/year compared with 0.5-1.0 t/ha/year), this process will, self evidently, be supply-limited in the long run.

However there is good reason to suspect relatively high rates of pedogenesis in tropical steeplands. (Ahn (1993) lists the four environmental factors that, over time (the fifth factor), define the rate of pedogenesis. These are the parent material, climate, vegetation/soil fauna, and relief. But he adds a sixth, often ignored, factor. That is human activity. Hudson (citing Pimental et al., 1976) suggests that tillage can increase the rate of soil formation ‘something like ten times’. Johnson (1987) however finds this unsubstantiated assertion ‘puzzling’. Nevertheless, on a steep tropical hillside where terraces are in a constant flux of erosion and maintenance, it is not difficult to imagine that soil is being formed relatively rapidly. (Seckler (1987) supports the general estimates quoted by Hamer (1982) for Indonesia of 2.4 mm/year (30 t/ha/year), pointing out that formation may be ‘three times higher’ in the humid tropics than in temperate zones. The T-values developed for watersheds in Java, Indonesia from Hamer’s figures and Wood and Dent’s (1983) calculations, range from 36 to 56 t/ha/year (Ministry of Fortestry, 1989). These may well be more realistic than using the standard figure (of 11.2 t/ha/year) from the USA. Perhaps, in certain situations at least, rates of surface erosion previously held to be unsustainable are in fact more than matched by anthropogenically accelerated soil formation”.

Will Critchley, 12.4.02.

I think we are constantly confused by the question of scale. Of course in the long run we need an overview. We might seek to have a Government-supported philosophy with regard to land and its significance to the welfare of the community. In the long run we need a worldwide realisation of our relation to the environment and our dependence on the land and its productivity. Meanwhile though, we have to help those who are suffering severe deprivation at present.

Perhaps the best way to help is somehow to bring about sustainable increased productivity on the individual farm by the individual farming family. So, for the moment, let's not concern ourselves with policies of land use, the need for roads, or waste disposal or mining or recreation, or even what type of agriculture suits a particular area. Most rural development programmes now are involved with empowerment of local people and the creation of local organisations including those concerned with promotion, packaging, processing and marketing. Important as these activities may be to rural development, we cannot regard them as encompassed solely by the concept of land husbandry.

Let's think rather, about what a farming family can do for themselves on their patch. Let's set our time scale to this year next year and the year after. A vulnerable small farm family wants to reduce its outgoings and increase its income, i.e. with regard to its finances. With regard to production, it wants to reduce its inputs in relation to its output. We want to promote practices that let the soil regenerate or recuperate. We definitely want to avoid or prevent soil degradation - rather than have to correct degradation after it has occurred. The in-situ degradation we want to avoid includes compaction, capping, sub-surface panning, acidification, salinisaton, water logging and nutrient depletion. We want to improve the soil's structure, stability, available water capacity and porosity.

We confidently expect that in the course of achieving the desired result, we will inevitably have increased the organic matter content and biological activity in the soil. This does not mean we have only to add lots of organic matter and earthworms to every piece of land. But we should try not to treat the soil in such ways that will reduce its organic matter content and biological activity. Maintaining biological activity requires that we conserve and maintain soil moisture as far as possible within useful limits. The soil should not suffer extended periods of drought or water logging.

We want to remove, avoid or reduce any negative factors for crop production. That is, we want to control pests diseases and weeds, but at minimal cost. We may want to protect the soil from rainfall impact to prevent surface capping and we may need to shelter the crop and the soil from extremes of cold, direct sun, wind and storms. We want to avoid nutrient deficiencies and toxicities.

If we have organic residues available, a lot could be achieved by adding them to the soil as compost or mulch. They should increase organic matter and most likely provide some nutrients for the crop. We would expect them to give some soil protection and help to suppress weeds, providing that we don't include active weeds or weed seeds in the mulch. We would expect mulching and composting to conserve soil moisture and in time, improve soil structure and available water capacity. Organic matter has other beneficial effects too, such as increasing the availability to plants of soil potassium and phosphorus, while ameliorating the affects of acidity and toxicities. It is also the main reservoir of available nitrogen in the soil.

Other specific measures to be adopted may vary from place to place. In some places shade trees or agroforestry may be appropriate for recycling nutrients, conserving moisture and suppressing weeds. In other places annual or perennial cover crops may be more suitable. Crop rotations and the use of legumes will have an important part to play. Inorganic fertilisers may supplement nutrients in the organic matter, so long as the other required soil properties are not impaired. Various corrective actions may be needed initially, such as breaking-up an existing pan, before a sustainable system can be established.

On the ground, in adopting the principles of better land husbandry the main objectives remain constant, in spite of variations in details of practice. We concerned with treating the soil itself as something that needs to be tended and improved, rather than as something to be used, abused, exploited or taken for granted. Focussing upon creating conditions that encourage continuous beneficial soil microbiological activity may give us a guide to a potentially universal concept.

At the recent AGM, someone asked “Why do we keep talking about better land husbandry? Surely everyone believes in good husbandry, and farmers do the best they can”. A good comment, but still a fair question.

As I see it, the answer lies in the fact that plant production depends not only on the husbandry skills of the farmers nor only on the genetic make-up of the varieties used, but also on the environmental conditions - above- and below-ground – where the plants are growing. The soil itself is often significantly and negatively affected by people’s methods of husbandry, no matter how well-intentioned, such that its condition falls away from the apparently rich physical x hydric x biologic x chemical condition of productivity that we would like to provide for roots.

Loss of soil organic matter in the first few years following the clearing and tillage of undisturbed land is an almost universal problem, which is often accompanied by decline of the condition of soil architecture due to loss of porosity, by increased runoff and erosion of soil, and by loss of productivity. Eventually the organic matter level reaches some sort of low-level equilibrium within the farming system, often of 1% or less.

Bob Stewart has pointed out that tilling the soil is like using a poker to stir-up a fire in your hearth. It exposes previously-sheltered organic matter to greater flows of air in the soil, resulting in oxidation of more of the organic matter and thus a faster rate of its decline. Therefore there is loss of organic compounds which hold soil aggregates together and enable the formation of divers pores, which facilitate both the passage and retention of water in the soil, which raise the CEC of the soil with benefits to retention and slow release of plant nutrients, and which represent the pool of plant-captured carbon serving useful purposes in the ecosystem.

As indicated in Figure 1 (page 9), poor land husbandry following the opening of land results in its ongoing degradation. Those people with a conscience about the condition of the land respond by undertaking conservation work to counter the signs of falling productivity, hopefully at least achieving some kind of ‘holding the door closed’ against further decline. But if the conditions of the soil around each plant (as a medium for its effective rooting) are not optimized with respect to productivity, the hoped-for yields of crops, pastures and forests will not be achievable.

If the ‘conservation-conscious’ farmer’s land husbandry actions are insufficient to improve (rather than just maintain) the soil condition, then better land husbandry is needed to improve soil conditions on a continuous basis, maximizing positive changes (in e.g. organic matter, organic activity, porosity and soil moisture, nutrient status, soil depth) and minimising negative changes (e.g. more rainfall partitioned to runoff, more erosion of particles, net decline in organic matter).

Well-managed, resilient and productive no-till systems based on principles of conservation agriculture are prime examples of good land husbandry, which farmers have reached by

achieving better land husbandry than they did before.

Much of the world’s agricultural land suffers from not-very-good husbandry at present. There’s still plenty of scope, and need, for a lot of better land husbandry.

“At present in Brazil we are making use of about 31 million hectares for annual summer crops, being part of the area planted twice per year which includes the ‘little harvest’ in autumn/winter (7.5 million ha.). The area cropped in summer has been shown to be stable in recent years, though with consistent increases in productivity.

In the international Congress ‘Conservation Agriculture’ which took place in Spain in the month of October 2001, the world of agronomy attested to the facts that cover of the soil with vegetation or plant residues, alongside the minimum disturbance of the soil, constitute the most appropriate technology yet developed for a sustainable agriculture. On this basis the Direct Drilling system is accepted in international circles.

But why are we limited to only 14 million hectares under direct-drilling? Why do we have only 45% of the of the area in annual crops effectively protected and improving, when we ought to have 100%?

Leaving aside the human aspects of the problem, it is worth analyzing this question in the light of the former use of the soil, subdividing this into two groups: old lands and new lands.

The ‘old’ lands, generally ‘from the forest’ and with good initial fertility, were cultivated over many years with coffee and/or annual crops which

required soil preparation to make possible the mechanical control of ‘forest regrowth’; or, put another way, of weeds. With the passage of time, the characteristics of the soil have been altered, as much by the reduction of stable organic matter (humus) as by the repeated operations of [disc-]ploughing and [disc-]harrowing.

The porosity and permeability have been diminished and there has been reduction in the proportion of aggregates accompanied by increases in dispersed clays. This dispersed clay has provoked the sealing of the soil, recompaction after soil-preparation and the formation of a less-permeable densified layer normally called a ‘plough-pan’. As a result, the slower infiltration produced greater runoff over the surface and consequent erosion. On the other hand, the ‘old’ land became replete with all sorts of weeds and their dormant seeds which persisted for years and years. At the end of a long period the lands were exhausted, leaving a necessity for replenishing nutrients.

The ‘new’ lands, generally of low [inherent] fertility, with the vegetation types of the cerrado [Brazilian savannas] or of native pastures, offered good original physical characteristics, principally in terms of permeability. Above all, they are yet free of weeds and their persistent seeds. It is clear that poverty in chemical characteristics and their acid conditions needed correction, and required the early supply of nutrients through liming, micro-nutrients and fertilizers.

In virgin lands the imposition of Direct Drilling has had rapid success and does not face great problems: there is no recompaction of the soil, and the use of herbicides is at only moderate level. Water infiltrates readily, there is little flooding, and no erosion, through the joint action of permeability and of dead vegetal cover. This early facilitation explains the rapid adoption of Direct Drilling in extensive areas of the cerrado.

In ‘tired’ lands, with degraded physical and chemical properties and large stocks of the seeds of various weeds, the implantation of Direct Drilling is more complex, requiring early measures for soil recuperation. These generally involve subsoiling, liming and the planting of species with intense branching root-systems which restructure the soil, provoking new aggregation and providing channels both those along roots which have

rotted away and those produced by insects and worms which are favoured by this new environment. Such recuperative species need also to have allelopathic action to minimize the weed problem.

In the South, Black Oats are unsurpassed for these purposes. In regions with dry warm winters other options are Eleusine, (a giant finger-millet) or Brachiaria brizantha which, when well-fertilized, and growing during summer and autumn, provides much straw, restructuring the soil and ‘holding back the forest regrowth’ in the subsequent crop. These species, to be established for the first time in the context of Direct Drilling, will be benefited by the recycling of nutrients earlier absorbed by the restorative vegetation.

This analysis explains the difficulties and the resistance to Direct Drilling encountered among farmers with ‘tired’ land in the State of Sao Paulo and even in Rio Grande do Sul”.

The basic principles of caring for the world’s soils were incorporated in FAO’s World Soil Charter of 1982. Since then, international meetings and publications have reconfirmed commitments and proposed steps to maintain and improve the protection and productivity of this basic resource on which, with water and air, our life on earth depends.

The world’s human population continues to expand, but this is not matched by expansion in areas of easily-usable land from which more food and other land-based necessities might come. There is therefore a rapidly-growing need to intensify production from lands already in use, and to achieve this in ways which are : (a) capable of maintaining and increasing productivity, (b) able to make more-efficient use of energy, nutrients and other inputs per unit of output, (c) effective in husbanding water, soil and its biotic communities, and (d) capable also of restoring to productive health those lands already degraded in various ways by unsuitable use and management in the past, whose decline has often and widely been manifested by excessive runoff and erosion losses.

To date, it has proved difficult to achieve conservation of soils’ productive potentials using those commonly-recommended actions which, though widely demonstrated in temperate and tropical areas, have not found favour with either the farmers on whose lands they were implemented nor with the soils they were supposed to protect.

However, a growing number of experiences with no-till systems -- in conditions of both mechanised and un-mechanised agriculture, on small and large farms in both temperate and tropical zones, and totalling millions of hectares -- now strongly indicate that further and significant improvements in conservation-effective agriculture are indeed possible, and acceptable to farmers, in addressing these varied concerns.

Two key facts provide firm grounding for expanded successes in the future:

.1 The health and production of plants is intimately related with the health and functioning of communities of organisms in the soil which is the four-dimensional rooting environment (three dimensions of space and one of time). The nutrition and management of soil organisms is essential to sustaining and improving the productivity of soils;

.2 Keeping the appropriate porosity of a soil at every level is a key to its healthy functioning as a medium for roots and soil organisms, to its capacity to accept, retain and transmit water into and through the profile, to its resilience in the face of erosive or other damaging forces. If these architectural spaces are lost, soil functioning is damaged, and time and biotic activity are then needed before these robust many-sized pores have been re-formed.

Soil functions best as a rooting environment when appropriate dynamic balances are maintained between its physical, biological, chemical and hydric components. Where the outflow of plant nutrients is regularly balanced by their compensatory inflow from a combination of sources -- soil-weathering products, transformations of organic materials, and, where necessary, complementary inputs of mineral fertilisers -- intensified cropping may be supported on a sustainable basis. Where any land use can continuously maintain these prime conditions, the time and space needed to be set aside specifically for adequate soil self-restoration may be greatly reduced, without detriment to the soil’s productive capacity.

The encouragement of ‘Conservation Agriculture’ derives from experiences with reduced- and zero-tillage, but is set out as an umbrella term that connotes systems of plant production – whether from crops, pastures, trees alone or in combination – which aim to satisfy the above criteria on a continuing basis, achieving simultaneously both stable production as well as effective conservation and optimum use of water and soil components.. It anticipates synergistic benefits which arise from combining the dynamics of improved soil productivity processes with the latent skills and enthusiasms of farmers and their rural families, joint prime keys to sustainability into the future.

The term embraces systems of crop production in which (a) plant residues – whether of the previous commercial crop or of a cover-crop - are retained at the surface to serve the dual purposes of providing a food source for soil organisms at the same time as providing a permeable cover. This protects against extremes of rainfall, wind and temperature; (b) direct-seeding through the residues is used so that soils, once brought back to excellent condition, suffer minimal disturbance by tillage or by compaction; and (c) rotations of crops, which include legumes for N-fixation . The techniques which are involved minimise or avoid soil-damaging effects – notably excessively-rapid oxidation of organic matter, and undue loss of porosity - often associated with conventional tillage-based crop production methods, particularly in tropical zones.

In support of this means of intensification, conservation-specific works along the contour, whether vegetative and/or constructed in form, should still be considered as complementary physical back-stop insurances for protection against unavoidable runoff and erosional damage by very infrequent but severe climatic events of water and wind.

The benefits arising from Conservation Agriculture have caught the attention of individual farmers, groups within rural communities, and local authorities. They have noted greater security of agricultural production and livelihoods in the face of unpredictable variations in climate and markets, and improved availability – in quantity and duration – of groundwater and streamflow. At the same time this has reduced amounts of government funds – from local and national authorities – which have needed to be allocated for maintenance and repairs of infrastructures such as roads and bridges, for recuperation of flood damage, and for drought relief. A consequence has been that greater proportions of their limited funds can be applied to making positive improvements in other social services and infrastruture such as facilities for health, education and public transport.

The Conservation Agriculture approach is already put into practice on such a scale that it is possible to see that increased resilience of the land and soil systems have several other positive effects:

.1 By improving land’s capabilities, it permits greater flexibility of land use in the present while also maintaining wide options for varied land uses in the future;

.2 By increasing security of rural livelihoods, it has also reduced the despair-driven rate of rural-to-urban migration;

.3 Infrequent climatic events of a given severity cause considerably less damage in such areas than they would have done under conventional tillage systems.

.4 The need for (often ineffective) restrictive and punitive legislation concerned with land use and management at national level becomes much less apparent, while those laws which assist local communities in framing and formalising their own encouragements and regulations become positively effective.

.5 It enhances local capacities to do better what they are already doing, at the level of communities , both those of people above-ground and of soil organisms below-ground.

6. It prolongs the useful life of carbon within agricultural systems and diminishes its unduly-rapid recycling back into the atmosphere as CO₂;

.7 It achieves effective conservation of water and soil more by stealth within production systems than by frontal attack independently of them.

The development of common-interest groups around the concepts and practices of Conservation Agriculture has already served to provide encouragement and mutual support to members as they make the changeover. For example, they have become action-groups for facilitating infrastruture development – notably of roads and conservation-specific works -- which benefit many contiguous farms, in conformity with landscape conditions; they have become very effective in farmer-to-farmer spread of the beneficial ideas and practical technologies which they have favoured; and have begun to develop into significant local pressure-groups for improvements in the policy and institutional ‘environment’ so as to have political and legal support for their own initiatives in Conservation Agriculture.

Accumulation of results of farmer-favoured local actions in Conservation Agriculture now offers the chance of producing positive impacts having global reach and effects. Such an achievement will ultimately derive firstly from the dynamic interactions of the soil and its organisms; secondly from the interests, skills, desires and decisions of farmers and their families, and thirdly from the more-appropriate institutional and political assistance and support which the wider society can provide. When these come together in profitable combination, the essential

improvements are likely to spread widely and rapidly through farmers’ own networks and linkages.

The framework of basic principles and developing practices which comprise Conservation Agriculture commend themselves to national Governments because it offers practicable ways of reaching agronomic, social, economic and environmental objectives more rapidly, holistically and securely than in the past.

When well managed, Conservation Agriculture represents fine examples of good land husbandry.

.oOo.

A SEVERE RAINSTORM TEST OF NO-TILL CORN,

(A 1:100 year storm, which fell in 7 hrs.)

Coshocton, USA, 1970.

Tillage type	Slope %	Rain mms.	Runoff mms..	Sediment yield kg/ha
Plowed, clean tilled, Sloping rows	6.6	14.0	11.1	50,781
Plowed, clean tilled, Contour rows	5.8	14.0	5.8	7208
No-till, contour rows	20.7	12.9	6.4	71

“No-till was helped by very good sod residue”.

(metricated from a note about: Harrold L.L. and Edwards, W.M. 1971. ‘A severe rainstorm test of no-till corn’ in JSWC (USA), mid-1971, vol.? p.30)

.oOo.

WHERE CAN I FIND INFORMATION

ABOUT BETTER LAND HUSBANDRY ?

T.F.Shaxson

Information about better land husbandry – concepts, background, approaches, thoughts, research, applications, results etc. – can be found in many places, here categorized under three main headings: in the writings of others, in the field, in your own mind.

In writings of others:

Background concepts:

- Perceptions of, and reactions to, the land itself

- Ecological dynamics in landscapes

etc

Research reports

- New information

- Reviews by area, by topic. etc.

etc.

Implications

- For policies

- For programmes

etc.

In the field

Technical observations and records

- Records of your own surveys

- Effects of interventions

etc.

Farm-families’ perceptions and reactions

- How they perceive their world

- What they may not be aware of

etc.

In your own mind

Prior influences on your own thinking and approach

- Upbringing

- Technical training

- Subsequent experiences

Own views and perceptions

- Ranking of different aspects

- Convincements / own convictions

- Preferred ways of spread of your understandings

- How you perceive farmers’ world

etc.

Motivations to help to improve land husbandry:

- Own livelihood as e.g. farmer

- Ecological conscience

- Interest/mental challenge

etc.

Questioning:

- Lateral thinking – other ways of interpreting available information?

- Do the observations really fit the ‘received wisdom’?