|
Improving Soil Fertility in the Pacific Jon Biloon is a sustainable farmer from Big Island, Hawaii. Here he presents his knowledge and experience of how to sustainably rebuild the health and fertility of soil after decades of damage from industrialised high input farming. Summary It is unfortunate that the proponents of conventional agriculture chose to exploit our fragile soils with high inputs of soluble fertilizers and toxic chemicals - exacerbating an already difficult situation. In response, successful sustainable farmers have come to recognise that the health of their communities are directly linked to the health of the soil. By having healthy soil we can grow healthy crops more easily and a healthy crop means greater economic returns to our farmers and of course a healthier population. Sustainable soil improving practices include cover crops, crop rotations, composting, mulching, living mulches and natural-source fertilizers. Fragile soils Soils of the Pacific Island Region are typical of the humid tropical and equatorial zones where chemical and mechanical decomposition of the parent rock (The rock from which the parent materials of soils are formed) is complete. Silica has leeched from the soil because of moisture and heat conditions and humus is deficient because of the rapidity of bacterial action in the prevailing warm temperatures. Losses of silicate clay minerals also result in damage to soil structure, making soils remarkably porous. Although soils in the Pacific Region can create luxuriant growth of broadleaf evergreen rainforest, once exposed by clearing the forest, the soils quickly lose their fertility because excessive leeching removes plant nutrients in all but a thin surface layer. In times of drought these exposed soils can be further degraded, becoming extremely hard and better used as building material (bricks) than for growing crops. The problem Soils of the pacific region are young and weathered, and because there is little natural renewal of natural minerals, the problem of low soil fertility in the tropics is centered on demineralization (the leeching of unrenewed silica and silicate clay minerals like the cations calcium, magnesium and potassium), and the lack of stable organic matter (humus). Instead of solving this problem conventional farming practices strive only to fix symptoms rather than the root causes. Conventional farming systems do not recognize soil as a living medium to be nurtured for future generations, and instead concentrate solely on making short-term financial gains. This conventional strategy involved feeding the plant and not the soil, leading to the use of soluble acid-based chemical fertilizers which quickly used up any remaining minerals. The focus of conventional agriculture then fell on the low pH (high acidity) levels that had then been created in their soil. Conventional liming was then recommended (without acknowledging the unique character of our tropical soils). In Hawaii, dolomite (because of its low cost) has been the ‘lime of choice’. In other parts of the Pacific, the lime is usually coral-based calcium carbonate, however these practices allow for, and in fact can require, increased use of soluble chemicals (again obviously good for the agrochemical salesman). Use of these products creates long-term problems for our farmers because the recommendations are made without recognising the importance of balancing the minerals in our soil. For example high magnesium levels relative to calcium can create the need for increased potassium, which conventionally is supplied by low cost muriate of potash (KCl) (a chemical deadly to beneficial soil bacteria). Another fertilizer that should be avoided is ammonium nitrate (NH3NO4). Increased use of soluble nitrogen fertilizers creates an increase in diseases like fungus problems that conventional agriculture then treats with extremely dangerous chemicals sold as ‘medicines’ to the unwary farmer. Fungicides kill all fungi - good and bad. This becomes a serious problem because beneficial bacteria and fungi are critical to creating humus (stable organic matter), developing healthy soils and growing a healthy crop. Because of this loss of fertility, increased use of chemical fertilizer is then recommended, which requires more lime, creating more imbalances and around we go on the chemical treadmill. Another problem that must be addressed in our Pacific Island Region is salt (sodium chloride) build up. This occurs from salt in the air getting into the ground, the use of manures that are high in salt such as seabird guano or steer manure, irrigating with brackish water and from the overuse of salt fertilizers. In the tropics the availability of phosphates is a problem, as this nutrient is easily tied up in our soils. Adding more acidified phosphates as is the conventionally practice is only an expensive short-term fix. We must keep in mind that less then half of all commercial fertilizers applied to our farmland are ever utilized by our plants. The rest contaminates our ground water and fouls our coastline. The solution In the Pacific Island region it is critical to use agricultural practices that can build humus and balance minerals in the soil. Below I have listed four methods that can help to sustainably increase soil fertility. 1) Testing the soil – this requires taking a soil sample and sending it to a laboratory where a complete analysis is performed. Tools necessary to take a soil sample include a clean shovel, and a soil sampling tube (stainless steel, chrome or a plastic pail). Sample Preparation
Phosphate availability and pH adjustment should be made using silicate lime like DiCalcium Silicate. When we use carbonate limes CO2 is released into the atmosphere and we are adding to the green house effect as only the calcium remains in the soil. Carbonate limes are only soluble up to pH 5.8 - creating wide swings of acidity during our wet /dry cycles - so use of carbonate lime is inappropriate in a tropical sustainable agricultural system. Silicate based limes like DiCal are much more soluble and penetrate the soil more efficiently. These limes remain, adding silicates to the soil which are sorely needed 3) Making Compost in the tropics Layered hot (Bio-Dynamic) compost This is the classic compost that utilizes a variety of bacteria that heat a pile - killing pathogens and seeds. Fungal “cold” compost This is a compost method that uses fungal action to turn high cellulose waste into soil using molasses. 4) Cover crops, ground covers, green manure and mulching Because of high rainfall it is imperative to protect fragile soils from the elements. If we don’t protect the soil nature will, and when nature does it on her own, she does it with fast growing, deeply rooted plants that can also be called weeds. Use of herbicides only encourages this type of growth and is not cost effective. The true cost of herbicides If the true environmental cost of herbicide use where calculated no one in the Hawaii would or could resort to a regular herbicide program. The true costs of regular herbicide use include contamination of ground water, loss of soil to erosion, loss of beneficial soil organisms, increased fungal, disease and insect damage, health problems associated with herbicide exposure and the development of “super weeds”. It is therefore imperative that we help nature by establishing plants that will act as companions to our primary crops. Cover crops Cover crops are plants that protect our soil and can actually build soil; they discourage the growth of unwanted weeds and are easily cut down and turned into the soil when time comes to plant a crop. Cover crops are often legumes like glycine that add nitrogen to the soil. In a vegetable garden a cover crop may be squash/pumpkin as this plant grows quite easily, discourages other plants and can easily be mulched when it is time to replant the garden. Sweet potato can be grown as a cover crop in orchards. The nice thing about using plants like sweet potato or squash/pumpkin as cover crops is the extra food they bring to the table. Ground covers Ground covers are a bit more permanent and can be legumes or grasses that act as companions in orchards, they are chosen because they grow slowly like paspallum grass or fix nitrogen like certain species of desmodium. Cover crops, can also be controlled by grazing animals such as sheep, geese or horses, with their manure adding valuable humus to our soil. Green manure Green manure are grasses and legumes grown to be cut and used elsewhere on a farm. In a perfect world one third of our farm should be devoted to growing green manure crops. They are fast growing plants that produce lots of bio-mass like soya/desmodium, alfalfa, sunhemp and sudangrass. Mulching Mulching is a wonderful method to suppress weeds in an orchard or garden around established plants. Any fine shredded green waste or compost will slow down weed growth and add humus to your plants (mulching with green compost can remove a bit of nitrogen from the root zone while it breaks down, but will give it back when break-down is complete). You can also mulch with cinders or crushed rock. Mulching will also conserve moisture so resist during dry periods unless the plants you are mulching have first been thoroughly watered. Conclusion Improving soil fertility is the key to success in sustainable agriculture. Recognizing what good soil structure (tilth) is critical for developing successful farming operations. Science has always illustrated that a healthy ecosystem of soil organisms is necessary to grow healthy crops. Unfortunately the conventional agriculture establishment has chosen to ignore nature as a partner in the growing business, and as a consequence we have all subsidized their profitable, toxic and environmentally disastrous experiments. It is a relief to recognise that these diverse beneficial soil organisms, from earthworms to mycorrhizae, perform as unpaid biological fertilizing machines, putting the profits from their work into farmers pockets. It is also heartening to realize that as one toxic chemical after another is removed from the conventional farmers arsenal, there are natural, low-cost alternatives that can protect our farms from erosion and droughts, insects and disease. This approach is leading to improved yields, greater economic wealth, healthier plants, a healthier population and a safe environment for future generations. Source: Jon Biloon, ‘organic agriculture for the pacific’ - presentation to agricultural conference, Thailand, July 2003
<< country/story review |
|
