Organic Farming – A Sustainable Alternative
By Samuel D.D. Jang
In my previous publication on the subject-matter – ‘organic farming,’ attention was focused primarily on organic manures, how plants grow naturally because of the events that take place in the organic circle as a result of the relationship between fauna and flora (plants/animals). In this edition, attention is focused on the control of weeds, pests and diseases.
WEED CONTROL UNDER ORGANIC FARMING
Plants, which grow in places they are not desired and whose growth at that material time constitutes a nuisance to man, his livestock or crops, are termed weeds.
To carry out an effective control of weeds, knowledge of their characteristics is very crucial. A.C. Anyanwu et al, (1999: 357), enumerated the characteristics of weeds:
- Weeds have wide adaptation. Can survive in both adverse and good condition.
- Weeds have modified parts – leaves, stems, roots and seeds that help them to survive very adverse environmental conditions.
- They are aggressive and persistent. They can regenerate from roots, broken stems, seeds etc, hence it becomes difficult to eradicate them.
- Weeds have long periods of viability.
- Many weeds are specially provided with structures that facilitate their dissemination.
- They have minute reproductive structures, which make it easy and possible for them to reproduce and spread unnoticed.
- They can produce a large number of seeds making it easy for them to spread.
In addition, weeds have a fast growth rate and mature faster than some cultivated crops. Some can complete two cycles during the life of the cultivated crop. Some are resistant to heat. They can regenerate after being burnt or the seeds cannot be destroyed by the temperature of the gastro-intestinal tract of animals, hence a lot of weed seeds are passed along with the waste products of animals.
Farmers often face a number of problems with weeds such as:
- Competition with the cultivated crop for nutrients, water, space and sunlight.
- Some serve as secondary hosts to pests of crops.
- Weeds reduce the quality and quantity of yields.
- They reduce the market value of crops or produce.
- They increase the cost of production.
- Some weeds have harmful effects on livestock. They have toxic effects when fed on by the animal.
The effort in weed control is to limit or reduce drastically, their effects on the cultivated crop. Chemical control could be effective but it has some limitations and implications to the users, especially small-scale farmers.
- Chemical weed control is not environmentally friendly.
- They are costly to purchase.
- There is danger of using a wrong herbicide or application of irregular doses.
- They require a technical know-how, which is not readily available to rural people.
- Where precautions are not taken, they can kill because of their toxic effects.
- They have a residual effect on soil and water sources.
Because of the attendant problems of chemical control of weeds, their subscription to rural farmers, especially in small holdings, becomes irrelevant. The following approaches will provide a sustainable alternative to chemical weed control:
- Weeding should be done when the weed-plants are still very tender before they start to produce seeds. This will reduce their rate of spread; at the same time they can be allowed to decompose on the farm to increase the nutrient level of the soil during that cropping season. Weeding by hoeing or hand-picking is much easier when they are still tender. At this stage, their roots are not well established in the soil and therefore they are less likely to choke the roots of planted crops.
- Weeding should be done at regular intervals to track down their spread. Soft grasses that can decompose easily could be used at the base of planted crops to prevent weed seeds from receiving sunlight to enhance their growth. These grasses when decomposed will add up to the fertility of the soil. This practice can be adopted with crops like tomato, pepper, and other plants that grow erect.
- Inter-planting a major crop with other crops will create a shady environment at the surface of the soil to disallow weeds any access to sunlight. The sunlight is the main source of energy to plants. Thus, all efforts should be made to disallow weeds or deprive them of this energy from the sun.
- Close but adequate spacing should be used where sole-cropping is practiced. This will facilitate the formation of canopies along the furrows and in-between plants to overshadow the weeds.
- Weeds with underground stems or rhizomes are difficult to control. These groups of weeds are better controlled by cultivation to expose these rhizomes to sunlight. The best time to carry out this control is shortly after the cropping season before the soil become hardened when cultivation becomes difficult. At this period, there is no rainfall to facilitate their growth.
- Floating of furrows can destroy broad-leaved weeds like goat-weed (Ageratum conyzoids).
- Since weeds are associated with specific crops, crop rotation can be employed in controlling them. A tremendous success can be achieved in reducing the buildup of weeds by this method. In addition to this, allowing land to lie fallow for a year or two can reduce the growth of weeds.
- A common practice of weed control is by handpicking and hoeing. The success of this method will depend on the regularity of the practice and timely operation.
- Early planting of crops can be useful in control of weeds like striga (wuta wuta – Hausa name). In addition to this, an understanding of the life cycle of both the crop and weed is vital in this method of control. Knowing the stage in the life cycle of the weed when it constitutes a nuisance to the crop is important. This will suggest early or late planting of crops. Deep-cultivation can also be employed in weed control. Tiny weed-seeds can be buried beyond germination.
- The biological method of weed control where animals may be used to feed on weeds in a crop field is available but not very feasible. Its practice could be adopted in orchards and plantations. But care must be taken to study feeding needs of the animals, lest you introduce animals on your land, which will destroy your crops.
MANAGEMENT OF ORGANIC MANURES
Organic manures, especially farm-yard manures, could be used directly without any processing. However, the attendant problem of weed emergence from some of them – especially cow dung – must be considered; and because of this, most farmers using cow dung burn them before use, in order to get rid of the weed-seeds. This practice destroys the Nitrogen content of the fertilizer.
Rather than burning them, they should be allowed to ferment for a long period so that weed-seeds are destroyed, or the farmer could take fresh dung to the piece of land to be cultivated before the cropping season. On this land, round-shallow holes should be dug deep enough not to disrupt cultivation. The fresh dung will be placed in these holes and covered with earth and remain there during the dry season. With the onset of the raining season, the first few rains will induce heat on the dung to facilitate their decomposition. The heat generated will kill the weed-seeds in the dung. During the cultivation, the holes should be opened and the decomposed dung scattered or sprayed all over the piece of land, as it is being cultivated or the manure fetched and applied to stands.
Where fresh unfermented dung must be used on the farm, they should be sprayed on the farm before the land is cultivated. This will help to bury the weed-seeds deep to prevent them from germination and will also accelerate the decomposition of the materials.
The following precautions are necessary when using these manures:
- Do not apply fresh or raw organic matter on plants to avoid scorching of plants from the heat they generate and the toxicity of urine.
- The application should be timely for adequate utilization and periodic growth of plants and to minimize leaching of nutrients.
- Split application in small successive doses that plants can absorb at once will reduce leaching.
- The amount to be applied must fit each phase of the life cycle of the plant.
Disease and Pest Control
A remarkable achievement in minimizing pest and disease infestation under this system of farming can be through cultural practices such as crop rotation, bush fallowing (this helps to reduce the build-up of pests and diseases); other measures include: –
– Use of indigenous varieties, which have high resistance.
– Use of improved disease and pest-resistant varieties.
– Use of ashes to control pests and/or neem-seed preparations.
– Fencing can reduce the menace of rodents.
– The use of scares and predators can be used for pests.
We can make a remarkable success in organic farming if, in addition to what has been highlighted, we adopt with it a good choice of land for every crop that would be produced, considering the topography, methods of land clearing and cultivation.
The foundation of a sensible set of production practices is the consideration of local natural production factors, for optimal exploitation of them, but with minimal adversities on the environment.
An optimal soil tilt will promote and conserve soil fertility. Minimum tillage operations are preferable. Organic farming may not be easy, but is sustainable.
Culled from Our VISION magazine, Vol. 4: No.2, 2003