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Banding with Biochar in Established Orchards for Water Management, Water Retention, and Tree Nutrition

by Dr. D. Michael Shafer


Checking fill depth of a biochar band.This paper describes the start of a multi-year field experiment at Warm Heart Foundation in Phrao District, Chiang Mai Province, Thailand. The project is not a scientific experiment but, instead, simply a field assessment of whether biochar, applied as applied here, can accomplish important goals for the public and private farmers.[1] Specifically, it addresses the increasingly important problems of irregular/poor rainfall and high/extreme synthetic fertilizer costs and the consequences of heavy synthetic fertilizer use. It starts with two apparently well-established findings about biochar – that it improves water retention and crop yields, especially in badly degraded soils – and applies them in established longan and mango orchards planted on steep slopes. We seek to assess the efficacy of banding with biochar to create contoured, lemon grass-sprouting, run-off slowing swales as a means of improving yields as a result of the combined impact of greater retained moisture and biochar’s impact on soil fertility. This is done by establishing five conditions in each of three widely separated orchards in the same district: (1) control; (2) biochar banding on the contour with lemon grass planted on the raised swale; (3) contour plowing identical to the plowing for banding, no biochar, but lemon grass planted on the raised swale; (4) contour plowing identical to the plowing for banding, with biochar, but no lemon grass; and (5) contour plowing identical to the plowing for banding, no biochar, no lemon grass, just residual swale. Because water runs downhill and because we are limited to established, working orchards, we cannot use a proper randomized plot layout, but must content ourselves with five vertical strips in each orchard. In this case, the three separate orchards serve as a poor substitute for three replicates of each treatment.

It is critical to note what can and cannot be controlled in the assessment, how our findings can be used and, most important, what we hope to gain from this effort.

Filling with biocharClosing trench to create swaleThis is meant to be a field test, that is, to assess how well a technique will work when used by the average farmer based on instructions from a neighbor who heard about it from a friend. Farmers where we work are well educated – they have, on average, a 4th grade education – but most of the world’s poorest farmers are illiterate and, like our farmers, have no access to extension services. Because it is a field test, we use biochar made by local farmers from whatever feedstock is available using the lowest tech equipment possible, flame cap troughs. Because the biochar is quenched with water and kept wet for safety reasons, farmers have no exact way to know how much they are applying. Because farmers use “little buffalo” mini-tractors with different sized engines and different sized plow blades, or actually plow with water buffalo, the width and depth of the bands where biochar is put vary a lot such that measures such as “one bag every 3 meters” result in very different amounts of biochar being applied.

Given these possible sources of variation, our assessment cannot say anything about the underlying scientific data regarding biochar. And we are not interested in applying it in such a manner.

What we want to know is whether or not this simple, low-cost, low-effort technique can accomplish two things that have never been accomplished here before: a systematic effort to address the unimpeded runoff of rain and irrigation water from barren orchards and a systematic effort to address the problem of degraded and still degrading soil.


Hypotheses and Cautions


Before beginning: This is not a scientific paper and is written to describe the start of a multiyear program of testing by normal farmers using the proposed techniques as they would normally do so. The aim is to test whether or not biochar, applied as made by farmers using whatever biomass they have available, mixed as best they can and applied as best they can has results of the sort found in controlled laboratory experiments. As with all Warm Heart projects, this is highly public. Each participating orchard is identified by a banner and each treatment is identified by a banner. Friends and neighbors of the participating farmers are invited to offer their observations and suggestions. The participating farmers are routinely interviewed on video and Warm Heart posts summary videos on its website.

The paper explains the local context, public and private needs, and the proposed, partial solution that applies biochar.

The project is not framed as a piece of formal, scientific research; it is a self-conscious field application. Were it to be framed around specific hypotheses, however, they would be the following – each amended with the conditional phrase: “as applied here.”

  • H1:  When used at the rate of 62.5 MT/ha buried just sub-surface in bands laid out as contoured field swales, does biochar improve soil water retention in orchards on slopes?
  • H2:  When used at the rate of 62.5 MT/ha buried just sub-surface in bands laid out as contoured field swales, does biochar improve orchard tree yields?

The “as applied here” condition is critical in both cases. As for H1, the efficacy of biochar banding and of contoured swales confound – and we lack the necessary test equipment to compare soil moisture differences between test and comparison plots. As for H2, the possibility of improved water retention improving yields confounds any efficacy attributed to biochar’s impact on yield improvement.

There is also no reason to believe that a failure of either hypothesis to show positive results contradicts well-established findings that biochar improves water penetration and retention, and plant nutrition. All that can be said is that the Warm Heart biochar banding technique did not improve water penetration-retention and/or plant nutrition in orchards on slopes.


Water as a Public Problem

Rainfall issues in north Tailand.Water – both its absence and its overabundance – is rapidly becoming a major issue in North Thailand, as in much of the developing world. Three problems combine to make the problem particularly vexing. Climate change is reducing overall rainfall, but increasing the violence of storms (rate and volume of rainfall) when they occur. Widespread deforestation has destroyed watersheds’ capacity to absorb and retain rainfall. Local political failure results in poor water management. The combined effect is to leave upstream farmers subject to drought and downstream populations subject to flash floods.

Public efforts to address the water issue have been ineffective, capital-intensive and impractical. No ideas regarding climate change risk mitigation have been articulated. Reforestation efforts have failed as a result of forestry policy and land tenure battles that go back more than a century. Traditional solutions to local water availability such as digging more ponds ignore local water management problems, and high tech solutions – such as using solar power to pump water from rivers to the top of mountains to then trickle down again – are capital-intensive, fail to address the fact that the water will still be wasted and that the river will run dry when the need is the greatest.


Plant Nutrition as a Public Problem

Grinding longan biocharAs a national survey of Land and Soil Fertility notes, “[m]ost of the soils in Thailand…have rather low fertility.” (Approximately 50% of Thai soils are acrisols, which are acidic, infertile, clays that are impermeable, do not retain water and lifeless.) The national solution has been massive application of synthetic fertilizers, which initially boosted yields but in many locations has reached its maximum utility. All synthetic fertilizers are imported, making fertilizer a major drain on foreign exchange and a food-national security issue for the current military government. The high cost of agrochemicals has also made Thai agriculture less and less competitive in ASEAN markets where Thai farmers earn less per unit of production than farmers from any other member state because of agrochemical costs.

Efforts to address the problems of increasing agricultural productivity while reducing synthetic fertilizer use have been ineffective. The problem is partly political: the fertilizer industry is well protected. But the reigning paradigm continues to be one of large-scale, chemical-intensive commercial agriculture which, whatever its relevance in the well-watered and fertile central plain of Thailand, is irrelevant in the mountainous North and semi-arid Northeast where the productivity challenge lies. Here the issue is building basic soil quality, something synthetic fertilizers cannot do, that the state could not afford if they could, and that poor farmers certainly cannot afford. In the North and Northeast, Thailand’s future source of staples, the issues are pH increase, soil structure improvement to improve water penetration and retention, C and OM content increases, the regeneration of soil life and erosion control. Neither the research nor the extension capacity to accomplish this exist and there is no evidence of a ground swell of change at faculties of agriculture where faculty and students continue to focus on factory agriculture in Central Thailand.Water as a Private Problem

North Thailand orchards are designed to suffer water problems. The soil is generally clay that dries to a brick-like hardness in the sun; no vegetation is permitted to grow under orchard trees; and orchards are situated on sloping foothills not appropriate for other crops. The result is fast runoff of passing rains and large quantities of irrigation water, and a lengthy period at the start of the rainy season before trees begin to absorb water. Where farmers pay for water, irrigation is a big production cost. Their best alternative is to install drip irrigation which is effective and also reduces fertilizer costs, but represents a major capital investment.


Plant Nutrition as a Private Problem

Biochar in trenchOrchard soils are generally extremely poor. Orchards are planted on what was once forest. The thin, poor forest soils degraded rapidly in the sun, leaving just an acidic clay behind. (Average pH 4.5 to 5.0.) Few farmers add organic matter because it must be added in such quantity, so regularly and because adding it requires turning very hard soil. (Organic matter decomposes in less than three months.) Farmers’ solution to orchard tree nutrition is massive doses of N in the form of 46-0-0 fertilizer. This is surface dressed and, not surprisingly, a large portion simply washes off with the irrigation water and rain or disappears as ammonia. Fertilizer is farmers’ largest single input cost.


Farmer Response

When asked about the future, farmers generally just shrug their shoulders. All of the orchard crops they grow are prone to boom-bust price cycles and it is not uncommon for farmers to suffer catastrophic losses when a poor harvest and/or price collapse leave them with extreme fertilizer debts. Diversification opportunities are limited and risk mitigation all but impossible with current resources. Farmers all hope to see a no fault government crop insurance program, but that is unlikely to materialize. When told that the means are at hand to mitigate the risks posed by increasingly unpredictable rainfall, improve their soil and reduce their input costs, they are all excited – and highly skeptical. The primary function of the highly visible banners and field tours that are part of the Warm Heart test program is fully to engage local farmers in a “believe your own eyes” campaign to improve soil quality and yields while reducing risk.


Aims of the Banding Program

In the context of Phrao, Chiang Mai Province and North Thailand as a whole, the banding program has “public” and “private” aims. In both cases, the program addresses concerns about water and plant nutrition.

Public Aims

  • Water
  • North Thailand and especially Chiang Mai Province are known for orchard crops: longan, lychee, mango, mangosteen, orange and rambutam. The hundreds of thousands of hectares of orchards, however, are largely located on cleared forest land on sloping foothills. Without any ground cover to ease water penetration, orchards are a big contributor to the North’s and the country’s growing water problems.
  • Nutrition
  • The poverty of the soil means that orchard crops demand huge applications of fertilizer, especially urea or 46-0-0. Orchards’ hard soils and slopes ensure that a large portion of applied fertilizer simply runs off without ever penetrating the soil, of that which does penetrate 50% leaches away or gases off. The orchard economy of North Thailand is, in other words, a major contributor to the country’s large and rising fertilizer bill.

Private Aims

  • Water
  • Orchard crops require water when they flower and set fruit, but few do so during the rainy season. Farmers, therefore, must irrigate most commercial orchards to produce good yields. Hard soil, high runoff rates and poor water retention all conspire to make irrigating orchard crops difficult under the best of circumstances. As climate change has made rainfall more irregular and produced a pattern of short deluges, not long, slow drizzles, farmers’ water problems have simply gotten worse.
  • Nutrition
  • Given poor soils and the high nutrition requirements of commercial fruit production, farmers feel compelled to apply fertilizers heavily. Because little of the fertilizer penetrates to the root system and provides nutrition to trees, they spend far more on fertilizer than they receive in value. Fertilizer is farmers’ biggest cost of production and it is not uncommon for repayment of fertilizer loans to account for two thirds or more of their gross, end of season sales. (It is normal for farmers to obtain their fertilizer from the buyer of their crop and to have their loan automatically deducted from their return.)


The Test Program

Schematic of treatmentsWarm Heart began the program described here in August 2016, approximately two thirds of the way into a normal rainy season. The 2016 effort aimed to test banding itself: whether banding damaged roots, how much biochar was required, the size and effectiveness of the swale. In May 2017 (just prior to the rainy season), the Warm Heart team and farmers will establish the test plots.

For each test plot, we have records of previous year crop yields; longan, however, is notoriously erratic from year to year. In each test orchard, we propose to assess average annual yield per tree using a common sampling system applied to each test section of each orchard. Otherwise, we have no knowledgeable soil scientist to design or implement tests of changes in soil quality or water retention over time, nor do we have any lab equipment. Our focus, therefore, is on the simplest variable of all and the only one that farmers care about, yield.

In three years, we would like to test whether the presence of banding reduces the required N application rate, a primary input cost for farmers. This, however, will follow a first round of results from water retention and the presence of biochar.

The three real test plots are located within the Phrao valley.

Research Design

Schematic of test planWe wish to assess the separate and combined contributions of biochar to yield improvements in three separate test orchards that we are using as proxies for replicates. To accomplish this, we will establish five separate sections in each orchard, arrayed next to one another, each running from the high side of the orchard to the low side. Because there is no way to isolate these test strips from each other in a working orchard, sampling will take place from trees located at the middle of each strip.

The five sections will be:

  1. Control: No treatment
  2. Test 1 (BC + LG): banded on the contour with biochar placed in the furrow and lemon grass planted on the raised swale
  3. Test 2 (LG): banded on the contour without biochar but with lemon grass planted on the raised swale
  4. Test 3 (BC): banded on the contour with biochar but without lemon grass planted on the raised swale
  5. Test 4 (S): banded on the contour but without either biochar or lemon grass, just residual swale

“Test” Plot 1

We started at Warm Heart where we have small mango and longan orchards in order to develop the basic banding technique.[2] In learning how to band, how much biochar to use (based on total band length per rai (local measure of area) and cost per kg, and how to refill, we “treated” the entire Warm Heart site, leaving no opportunity for comparative performance testing.

Test Plot 2

Test Plot 4Test Plot 3Band running across newly planted area of Test Plot 220 rai plot of 500 longan trees planted on a 5⁰-10⁰ slope. (One rai = 1,600 m2; 6 rai = 9,600 m2 or approximately 1 hectare, 10,000 m2.)

Plot divided in half top to bottom to mimic water flow; one half banded, the other not.

Test Plot 3

10 rai plot of 250 trees planted on rolling land.

Test Plot 4

10 rai plot of 250 trees planted on land varying from flat to 20⁰ slopes.


The Warm Heart Technique

Harvesting farmer 8's plotsThe Warm Heart technique uses locally available technology and was developed by local farmers. In Phrao valley, farmers use “kwai lek” or “little buffalo” – hand operated plow/tillers that mount a 6 or 9 hp motor.[3] (In the mountains, farmers use water buffalo because the slopes are too steep for a kwai lek.) Using a kwai lek with a single blade plow, the farmer cuts a single band between each row of trees to create, as best as possible given orchard layout, a contour. Depending on horsepower, blade and the farmer’s strength, the band is approximately 20 cm (9”) deep and 20 cm (9“) wide. The band is filled with crushed biochar (2-5 mm) (up to 1/8, approximately the size of a corn kernel) to a depth of 8-10 cm (2-3”). The band is then refilled, leaving a low (10 cm/4”) swale along which lemon grass is planted.[4]

At 20 cm x 100 cm, the band is 0.2 m2. The biochar applicate is 1.25 kg/m. The resulting application is therefore 5 x 1.25 kg/m or 6.25 kg/m2 or the equivalent of 62.5 MT/ha.


Biochar Employed

Ground Longan BiocharThis program uses biochar produced locally from bamboo and longan orchard tree prunings pyrolyzed in locally manufactured 500 l. and 2,000 l. Warm Heart Trough Ovens (flame cap) operating at between 450⁰ and 750⁰ C for approximately one hour.[5] The biochar is crushed by driving a tractor or truck over it until the largest pieces are approximately the size of a dried corn kernel (5 mm). The biochar is then saturated with pig urine one or more times depending on time and availability of pig urine.[6] The biochar employed was made variably by half a dozen local farmers, some more experienced than others. Trough temperature and smoke production, as well as biochar yield and ash content vary considerably among the different “burn masters.” How much pig pee a given lot of biochar ab/adsorbs is a function of time, the amount of water used to quench it and whether it is raining or not.



Farmer acceptance is a function of perceived value and cost. As our tests go forward, we hope to be able to demonstrate value to individual farmers. (We place no faith in the possibility of government acceptance of the program and its replication with government support. The discussion of the public utility of the program is simply for the benefit of an interested public.)

As for costs, they are low but highly variable depending on whether or not a farm family wishes to undertake the project themselves or a larger farmer wishes to outsource the project.

On-farm costs (small, family farm, 2 rai of orchard)

Biochar production

Bagged Longan Biochar

Fruit orchards generate approximately 1.25 MT per rai of prunings annually; if a family has 2 rai, they will have 2.5 MT of feedstock. Using a Warm Heart 2,000 l. Trough Oven (cost $200), a family can make .625 MT (625 kg) of biochar in less than 2 days. Crushing takes a matter of hours at most. If the family has access to pig, cow or horse urine, saturation is more a function of collection time than activity time. If the family does not have access to urine, sloppy pig pen mud or chicken coop floor litter can be mixed in as a replacement. The amount of time required depends largely on the number of hands available. (Total, 10 person days)


A rai is 40 m x 40 m. The way orchard trees are planted, each rai requires 4 bands of 40 m for a total of 160 m/rai. A 2 rai orchard will require 320 m of banding. Using a kwai lek, a farmer can do this in a few hours. (0.5 person days)

Biochar filling, in-filling and planting

Filling at the rate of 1.25 kg per m, the family will require 320 x 1.25 or 400 kg of biochar. This should not take more than a few hours working from a farm cart. In-filling can happen at the same time if there are two people. Planting will take just a few hours, although preparing the lemon grass for planting may also take several hours. (4 person days)

Total cost: No cash; 15 person days

Out sourced costs (small, commercial farmer, 20 rai)


Depending on local availability, biochar can be purchased for $0.14 to $0.29 per kg, pre-saturated. Cost for the required 4,000 kg = $560 - $1,160


Assuming that owner has kwai lek, 3 days of work, one laborer at Thai minimum wage (unrealistically high) = 3 x $10 = $30

Biochar filling, in-filling and planting

Assuming large scale-economies, 60 person days at Thai minimum wage = 60 x $10 = $600

Total project cost:  $1,190 - $1,790

[1] We understand scientific experimentation to require the complete control of all relevant variables and the capacity to measure variation in relevant variables in their isolation with a very high degree of accuracy. Furthermore, we understand scientific experimentation not to be subject to human interest, but to be undertaken at “neutral” sites fully controlled by the experimenter. On the other hand, we conduct our assessments in working orchards subject to every conceivable, uncontrolled and even unknown variability. Likewise, our “lab assistants” are the farmer’s day laborers and our instruments are the field scales they use to weigh fruit yields. And, of course, unlike a proper test plot, the orchards we work on are often farmer’s sole source of income, which gives them a powerful interest in our “experimentation.”

[2] Warm Heart’s land is flat (there is no runoff problem); Warm Heart has never irrigated (there is no water cost problem, but Warm Heart lost the entire 2016 crop because of drought); and Warm Heart has never fertilized with either synthetic or organic fertilizers (there is no input cost as the orchards have been neglected).

[3] The Warm Heart program has experimented only with lowland areas because this is where orchard crops are grown. In the mountains, farmers plow with water buffalo. The next project will be to test water retention-soil nutrition providing banding in steep mountain corn fields plowed with water buffalo.

[4] Depending on the age of the orchard, the lemon grass may thrive or just survive. If the orchard is young, the farmer gets a small crop; if it merely survives, it has fulfilled its primary mission which is to absorb water and slow runoff.

[5] Temperature varies during pyrolysis with feedstock loading; pyrolysis time depends on whether char is from feedstock loaded early or later. Char from each burn and subsequently char from many burns is mixed. Average residence time is approximately one hour.

[6] Warm Heart has the good fortune of being located within 2 km of a commercial piggery that permits us to collect urine from its biodigester overflow free. We collect it in a 1,000 l. pickup truck tank and use it liberally on our biochar. Field tests show that pig urine charged biochar outperforms local farmer’s normal NPK applications.

  • Dr. D. Michael Shafer
  • President, Warm Heart Worldwide, Inc. (USA); Director, Warm Heart Foundation, CM273 (Thailand)
  • 434 Cedar Avenue, Highland Park, NJ 08904, USA
  • 61 M.8 T.Maepang A.Phrao 50190, Chiang Mai Thailand