You have arrived at an Earthchild webpage. Author: Choon Ming Tan.

An Argument for Artificial Canopy Protection in Tropical Farming

http://members.lycos.co.uk/earthchild77/p_canopy.htm

Last updated 8th Jun 2002

Below is an e-mail transcript, written by me more than a year ago, addressed to my bosses (who also are my friends) Mr Lim Tian Soo and Mrs Evelyn Eng-Lim when I was working for them at Green Circle Eco-Farm, Singapore during my university year-out. The e-mail was reformatted for web publication; no changes were made to its contents. If the reader has any opinions or suggestions regarding any issues raised in the e-mail, please feel free to e-mail me.

----- Original Message -----
From: Choon Ming Tan <choon_ming_tan@hotmail.com>
To: <soo@pacific.net.sg>
Cc: <s.m.hutchinson@salford.ac.uk>; <m.j.w.heyslop@salford.ac.uk>; <j.h.lippiatt@salford.ac.uk>
Sent: Saturday, April 07, 2001 8:14 PM
Subject: ARTIFICIAL CANOPY FOR ADAPTATION TO TROPICAL CLIMATE

Hello Soo and Evelyn,

(The following was put together in one long breath starting late afternoon on Fri until first light Sat. Some parts are a little cynical, sarcastic, especially the parts written in the early morning. Please take it with a light heart and a chuckle if I happen to tread on anyone's feet, including Salford lecturers.)

ARTIFICIAL CANOPY FOR ADAPTATION TO TROPICAL CLIMATE

A simple understanding and acceptance of the tropical forest ecosystem would tell us instinctively what is required in order to practice farming under such climatic conditions.

2 characteristics of the tropical forest demand our attention: multi-storied layered canopies and thin topsoil. Before I proceed further, I wish to emphasize that the tropical forest ecosystem has evolved over the centuries to reach the "stable" state it is today, a state which allows the biotic system to sustain itself in an abiotic environment of heavy rains and harsh sunshine. In another words, the vegetation structure is dynamically "abapted" to tropical environmental conditions. An understanding of this abaptation would allow us to use technologies (of least minimal interference with nature) to artificially mimic this abaptation to make farming in the tropics economically feasible.

Forest canopies serve 2 functions. The canopy intercepts rainfall, reducing the impact at which raindrops hit the ground. This function complements the role of leaf litter cover on forest ground to reduce topsoil erosion. The top canopy layer also protects lower layers from harsh tropical sunlight, creating a more benign (cooler and humid) environment for biological life. If a continuous canopy had not evolved, strong sunlight would have broken down the leaf litter and burnt up topsoil rapidly. Precious nutrients would be washed off at an inexorable rate and ecological recycling cannot take place.

Tropical forests have thin topsoil. Root systems are relatively shallow to absorb nutrients once they have mineralised into forms which roots can take in. Because of high annual rainfall and in particular sudden storms, soil nutrients are leached away nevertheless, regardless of soil organic matter's capacity to hold on to plant nutrients. In tropical agriculture, this nutrient loss has to be arrested or minimised to increase recycling efficiency. To farm the land in a biointensive manner, the nutrient input and output has to be prudently managed, ensuring that most if not all of our precious capital in the form of compost is directed towards plant growth.

We need look no further than the farms (both conventional and organic) in tropical Singapore to learn how they have adapted their farming techniques to make growing vegetables economically feasible in our tropical climate. If their techniques were not correct, these farms would not have existed at all. Therefore, there must be one or 2 lessons we can learn from them. These farms may not meet the high organic and ecological standards that we want, but at the least, they have made it possible to supply locally grown vegetables to Singaporeans. In view that they are able to overcome difficult local environmental conditions (heavy rainfall and harsh sunlight), using local resources, to grow leafy vegetables (which we already know are hard to grow), their techniques deserve our attention and respects. We should not eschew their techniques simply because they do not satisfy our environmental principles.

Firstly, the application of chicken manure. Chicken manure has the highest NPK content compared to other farmyard manures. Although cow dung is also available in limited quantities in Singapore, local farmers have stuck to using chicken manure as a source of organic input to increase their soil fertility. I would postulate that the usage of chicken manure is necessary to grow nutrient demanding leafy vegetables because its high NPK content would assure the farmer that his soil contains adequate nutrients to support plant growth despite high nutrient loss through leachate and surface wash off.

It may be argued that local farmers' application of raw chicken manure to their fields is environmentally wrong and pose a health hazard on the basis that chicken manure contains pathogens, antibiotics, growth hormones and other artificial additives. We demand that they switch to using composted cow dung and beans, which we practice at Green Circle. Although our standpoint is ecologically and socially more beneficial, we should not let our pious principles overlook the fact that the high NPK content of chicken manure has made it possible for local farmers to grow vegetables intensively from limited land resources. If chicken manure is not utilised, a locally abundant critical organic resource would have been wasted and farmers may resort to more harmful artificial inputs.

Western organic practitioners advocate the use of cow dung. (India is also known to rely on cow dung as a primary organic protein source.) Cow dung's nutrient content is sufficient to sustain agriculture under their local environmental conditions. I would also assume that cattle make up most of their livestock. They recycle abundant locally available cow dung. Their recycling system works well under their local climatic conditions. However in Singapore, we have chicken dung and local farmers have already found that the use of chicken dung adapts well to our own tropical climate and soil conditions. Recycling may be considered a "technology" and any wise environmentalist or ecologist would tell us that technologies are to be locally adapted.

Composting may be an option other local farmers consider economically hard to implement within their farms. Precious planting space would have to be sacrificed to generate compost. A certain amount of know-how is also needed. For the uneducated local farmers whom I see living in ramshackle knock-down houses, and whose vegetables prices are dictated by a fluctuating market, their primary concern is to coax as much yield as possible from their leased parcel of land, using whatever farming techniques that work and this includes applying raw chicken manure. They should not be condemned outright for their seeming ignorance of the hazards. Larger external economic forces had to be addressed first before we can persuade local farmers to modify their farming techniques. At Green Circle, we are fortunate that resources are available for us to practice ecologically appropriate organic farming.

If the environmental issues pertaining to the use of chicken dung is of such utmost importance, then there are other farm practices at Green Circle that are also worth serious contemplation: does the timber from which our saw dust compost material is taken from, cut from a FSC certified source? Why use fibreglass rainwater storage tanks, is not the health of farm workers compromised? Why price organic vegetables out of the affordability of ordinary citizens, where is the environmental justice? Why is a treatment facility not build to ameliorate the BOD, nitrate and phosphate content of runoff that goes off the farm after every downpour?

Environmental considerations - comprising ecological, social and economics, are contentious and counter-arguments endless. I dread to tangle myself in such a discussion, as is the situation now. Whatever the case, a balance or compromise between the 3 central pillars of environment has to be accepted - ecological, social and economics. Most times, unfortunately, it seems that at the end of the day, economics is the key underlying deciding factor.

A rain impermeable plastic canopy over the planting beds is direct management of the soil erosion and nutrient wash off problem. This option intervenes at the source of the problem, which is rainfall. The canopy creates a semi-controlled growing environment that reins in 2 environmental factors: rainfall and sunshine (less control of the latter, more over the former). 2 rainfall related issues are eliminated in the process: loss of nutrients and topsoil erosion from the planting beds, and the water quality of runoff that goes off the farm (if this is a problem at all in our context).

At Green Circle, nutrient run off the farm creates no serious environmental consequences, or rather the high nutrient content of the runoff is neither monitored nor are there any users down the drain before it enters a reservoir. Runoff of significant volume occurs only during heavy precipitation. The drain is most likely to be devoid of life (at least not those visible to the naked eye), so would give no biological indication of pollution. Oxygen sag in the BOD curve is likely to be brief because high temperatures cause rapid breakdown of organic matter and oxygen replenishes quickly with storm runoff. By time it reaches one/two hundred meters down the drain, dilution would delete any trace of pollution. If algal bloom occurs at the reservoir, the authorities would not bat an eyelid because if they were to trace, all farms in the vicinity would have to be incriminated.

It may be argued that a plastic canopy framework over the farm is disgustingly unnatural, yet farming itself is unnatural, the most fundamental way in which humans interfere with the natural environment. At least one other local organic farmer had this foresight and started off farming inside hangar like shelters with clear plastic canopy overhead and netting by the sides. While most conventional farmers (except 2, according to AVA) cover their fields with netting (primarily to keep insect pests out), they have unknowingly replicated the tropical forest microenvironment by putting up a canopy. An overhead netting although does not regulate the amount of rain falling onto the beds and hence nutrient loss, but it serves to break the rainfall. It also provides fragile leafy vegetables some protection from harsh tropical sunlight.

At this point, I wish to suggest that the parent stock of the conventional seeds that we use at Green Circle are probably grown in similar protected environments. The seeds are therefore selected to do well in such sheltered conditions. Unless we create a similar growing environment, the vegetables are unlikely to do well. And this applies similarly to the generous nutrient input practiced in conventional farms.

Acknowledging the aesthetic argument that a plastic or net cover looks artificial and unecological, but it is in fact actually applying an overlooked ecological principle by mimicking the canopy effect in tropical forest ecosystems. And if I may dare put forth a suggestion, this "technology" may be the key to successful farming in tropical areas with high rainfall, strong sunlight and poor soils. How then can we argue that an extensive canopy is unecological when we are merely adapting a simple tropical forest characteristic studied in secondary school geography classes? Yes, farms or planting beds covered in nets or plastic look ridiculous and absurd. But what other alternatives do we have when local farmers have already shown that the technique works well for growing leafy vegetables? And isn't it leafy vegetables that we have been striving to produce because only the "leafies" can give us the high returns per unit land area compared to fruit vegetables? If there had been a less environmentally less intrusive way of growing "leafies" without the construction of a canopy, which also is more likely to be cheaper, someone else would have suggested the idea long ago. We can always innovate but I would think the basic principles of the tropical forest ecosystem still have to be adhered to.

The initial investment is high, just as Green Circle invested in digging a 8/9 meters deep pond and fibreglass tanks with roof gutter system to collect and store rainwater. Now, the difference is that water is visible and a shortage of it is readily apparent. Loss of soil nutrients through leachate and wash off however is not readily observable. Moreover in Singapore, it seems that compost raw material (tree prunings, saw dust, manure etc) is readily available, a blessing we have taken for granted. Probably, the farm personnel who feels the loss most is the farmhand who tills the bed, applies the compost and broadcasts the seeds. Because our soil has not yet attained the crumb, nutty structure and uniform black colour of good agricultural soil, an untimely thunderstorm certainly can destroy a hard day's work. To grow leafy vegetables, it is inevitable that the bed has to be cleared and seeds broadcasted. A downpour washes away nutrients (and needless to mention, the minute seeds too) from surface layers which seedlings need for initial growth, leaving behind sandy particles. Raindrop impacts not only can kill fragile seedlings but also cause clay to splatter and fill up surface pores on the bed. Sunshine after the rain hardens the clay creating a hard crust hindering aeration and water infiltration, which is an overt indication of poor soil quality. Sometimes, the crust even cracks open indicating how hard it is. Nothing demoralizes the farmhand most when he wakes up the next day to see his bed obliterated, then he starts cursing the sky the rest of the day and what do you know, rain ceases to fall for the next few weeks...

Under natural circumstances, the capricious behaviour of nature can be condoned. But on the farm, chance and randomness can be reduced to at least guarantee a steady livelihood for the farmer. He lives by the land and some level of intervention is necessary and assuring, where possible, in managing the flow of water, light and air. Unless he has plenty of resources to accommodate nature's caprice, I think we can work the soil more efficiently with a little management or "intrusion". This is especially true in Singapore where compost is readily available, rainfall plentiful, and sunlight and warmth available all year round.

Putting up a net or plastic canopy does not compromise on ecology. In fact may even enhance ecology. Because the land is farmed biointensively, soils are managed to enhance or help plant growth. At the initial stages of bed preparation, tilling in compost helps to loosen soil and aid root growth. If tilling is not required, why had farmers in the past and at present go through the trouble to dig their soils? Man is lazy. Who would willingly sweat out there in the sun all these decades and centuries if tilling does not help to increase productivity? There must be benefits in tilling. Yes, earthworms will be chopped and soil horizons overturned. Yes, I feel guilty every time I sink my hoe down and witness yet another earthworm wriggling with green fluid oozing from its torn body. But the topsoil at Green Circle is so shallow in most areas that barely one hoe blade's depth down, you hit hard clay. Letting nature do the work at soil formation takes a long time and if all farmers are staunch nature lovers, the lucky ones with good soils survive, whereas the unlucky ones with thin soils will curse themselves to their deathbeds. I suspect that Western practitioners who advocate no-till are either 1. lazy environmental bums who while do not want to use fossil fuel consuming tilling machines but refuse to lift a hoe, 2. converts from till to no-till and therefore advocate to others the advantages of no-till, or 3. have so much resources that they can afford to paint themselves eco-friendly by employing only nature's tillers.

The initial tilling and mixing in of compost is important regardless of how long that process may take to do manually. And here I quote 12 inches as recommended by Jeavons (1995), an American in his book "How to Grow More Vegetables (5th ed)." (Even his soil management practice is criticized by at least one reviewer on Amazon.com's on-line bookstore.)

The usefulness of a canopy cover comes in after the initial digging in. The soil is loose and has a raised bed effect. The plant needs not waste extra energy at pushing its roots through hardpans. A good root system translates to a healthy plant aboveground. Heavy rain falling on unprotected beds recompacts the soil, washes away precious organic nutrients and creates an impermeable surface crust that even weed seeds would not germinate. If a canopy is employed, recompaction would not occur so quickly and the bed need not be tilled to aerate the soil for the second and even third crop. Fertilization is carried out by slicing in compost into the top 1/2 inches and liquid fishmeal fertilizer (x5 dilution) applied. The soil is disturbed minimally - condition most favourable to earthworms and all other "wildlife" of the soil ecosystem.

Mulching is used to cover exposed surfaces of beds planted with fruit vegetables such as okra and eggplant. When "leafies" are grown, the crop itself creates a living mulch. But at seedling stage when the plants' leaves are too small to act as soil cover, the plants and the bed are most susceptible to rainfall. It is most disheartening to see seedlings sticking out on a dead hard surface crust.

Net or plastic canopies have their farming roles in tropical zones where rainfall although plentiful, their untimely downpour on exposed agricultural soil is ecologically, economically and socially undesirable. Because such an extensive canopy over farms is aesthetically intrusive, we should not dismiss it as unecological. An eco-farm need not be any less "eco" if it is covered by netting or plastic. The contrary may be truer because we are adapting a tropical forest characteristic to create a canopy, albeit artificial over tropical soils.

The multifunctionalities of farming must never be cast aside to pursue one's principles. While farming techniques should adopt appropriate ecological values, sometimes such values are not economically practical. The conscientious farmer not only has a responsibility towards nature conservation and environmental protection, he is also responsible for providing locally grown vegetables to the people. Other local farmers are doing precisely just that, albeit driven by economic pressures and with slightly dismal ecological stewardship. If the vision of plots and plots of organic farms with zero pesticide and artificial fertilizer input is to be realised in Singapore, farming techniques refined by local farmers, a systematic approach, light machinery and our environmental standards must be incorporated. Condemning outright their techniques as ecologically bad may be unjustified because if nothing else matters, these sun-baked, hand-callused farmers have actually made farming work in our tropical climate with poor soils all these years.

Regards,
Tan