Organic Farming Practices
Introduction;
Organic Farming is to copy natural cycles that support the healthy growth of plants. Natural systems rely upon diverse populations of living plants and organisms to complete the cycle from living plants to dead organic matter which is recycled to provide food for more living plants. This cycle also maintains soil structure, improving the soils capacity to capture and retain rainwater for the use of living plants.
This course is to teach the basic practices that will provide ideal conditions for these natural processes to take place. The desired result is that food will be provided for crops by natural means. Also covered are ways in which pests can be controlled, or managed to acceptable levels by introducing natural controls and the use of indigenous plants from which pesticides can be made……..
Mulching;
In nature, mulching occurs when leaves, twigs, branches, grasses etc fall to the ground. The roles played by this mulch are;
The soil is shielded from the direct sunlight resulting in regulated soil temperatures and reduced evaporation of moisture
The mulch provides food for soil dwelling organisms which help break down organic matter and ultimately provide food for plants. (This is natures way of making compost)
On the farm, mulching can be done by using crop residues, which can be cut down after a crop has been reaped, and left on the surface of the soil.
Using Compost;
We will cover how to make compost on another course, but here, we will look at how we can put to use the compost we have made, in the field;
Compost made at home using vegetable matter such as leaves, grass cuttings, twigs, wood ash and food scraps, and is made in a controlled environment that speeds up the composting process. So we can, in a controlled environment, manufacture plant food more quickly than the natural process. Compost can be used in the field in the following ways;
Compost can be turned into or mixed into the soil
It can also be applied by laying it under the existing mulch
Compost should not be applied directly onto the surface of the soil because it will be dried out by the sun and the decomposing process will be retarded.
Multi Cropping;
The practice of mono-culture, (Single crop farming systems) in which only one crop is planted in one field, is not natural and effectively interrupts the balance of natural systems. In order to imitate nature, diverse inter-cropping is required. This means that different crops are planted in the same field. Each crop must have a specific role in which they support the main crop, or in which the various crops planted support each other.
For example;
Main crops-Maize & Sorghum
Living ground cover crops-Pumpkin and Watermelon
Nitrogen fixers-Cow peas or Pigeon peas
The above example shows that we are planting pumpkin and watermelon to help the mulch shade the soil from direct sunlight, but these crops also help provide shade to the mulch, thus preventing the mulch from drying out. In addition we have planted a legume crop so that Nitrogen will be made available to the other crops during their growing period.
Rotational Cropping;
Rotational cropping can be used in conjunction with Multi cropping by growing a legume crop (Nitrogen fixing crop) as the main crop in one field this year followed by a Maize/Sorghum main crop the next year. This helps to condition the soils and the legume residue can be cut and used as mulch that still has a relatively high Nitrogen content after reaping and decomposes more rapidly than maize or sorghum residues.
Example of legume crop inter-planted with other crops;
Main crop-ground nuts
Living ground cover crops-Pumpkin and Watermelon
Inter-planted with a 10% population of maize
This example shows that our main crop of legumes is inter-planted with pumpkin and watermelon to provide living ground cover and with maize which helps to partially shade the groundnut crop.
Crop populations;
A farmer’s resource is the soil. If the soils are not cared for, they become barren of plant nutrients, they lack the ability to catch and retain rainwater and as a result they lack the capacity to support plants. However, even well cared for soil has limitations as to how much plant life it can support. So it is important that crop populations are controlled so that maximum crop yields can be achieved. If crop populations are too high, the plants are weak and produce small, inferior fruit resulting in reduced yields, if crop populations are too low too little fruit is produced per meter squared, also resulting in low yields. It is therefore important to plant at the correct density so that optimum use is made of the planted area.
For example;
We will work with an area of 10m x 10m because it is easy to mark out the area and count the plants within that area.
We are planting the following crops;
For example;
Main crops-Maize & Sorghum
Living ground cover crops-Pumpkin and Watermelon
Nitrogen fixers-Cow peas or Pigeon peas
| Crop | Recommended Population/100m sq | % of integrated planting | Recommended population |
| Maize | 500 | 55% | 275 plants |
| Sorghum | 750 | 30% | 225 plants |
| Pumpkin | 400 | 2.5% | 10 plants |
| Watermelon | 400 | 2.5% | 10 plants |
| Pigeon Peas | 750 | 10% | 75 plants |
|
|
| Total plants per 100 m square | 595 plants |
This table shows a total plant population of 595 plants in a 10m x 10m (100m sq.) area, this equates to a per hectare population of 59’950 plants which would be considered a suitable population for maize in an area with good rainfall, fertile soils and temperatures not exceeding 35 degrees Celsius. (Point out the obvious differences in climatic conditions to the students)
Integrated Pest Management;
Integrated Pest Management is to make use of natural resources to control pests in a responsible way.
The use of natural pest predators
Pest are drawn to fresh green crops or to the ripened fruit of crops. The pests use the crops as their habitat but the crops do not provide the habitat structure needed by pest predators.
The provision of a habitat for insects that prey upon pests will provide the following benefits;
A place in which pest predators can breed
This habitat consisting of indigenous shrubs and grasses can be avoided when spraying crops with pesticides so that breeding pest predators, their eggs and grubs are not killed by the application of pesticides, thus maintaining pest predator numbers.
The use of indigenous plants; (organise visit from mission @ Manica)
Pest Predator habitat
Plants with qualities that are repellent to pests;
Herbs-herbs such as garlic which give off strong odors help keep pests away from crops.
Plants such as the Marigold also keep pests away from crops.
Plants with properties that are toxic to pests;
There are many plants that have chemical properties that are toxic to pests. Infusions can be made, by soaking leaves, bark or roots in water and then spraying the infusion onto your crops to kill pests.
Scouting for pests (An expert should be brought in to teach what are pests and what are predators and produce a booklet specific to local pests and their predators)
Purpose;
To assess pest numbers
To assess crop damage
To assess Pest predator numbers and the impact they are having on the pest populations
How often to scout?
Once a week under normal circumstances
Two days after spraying
Scouting pattern;
Count pest and predator numbers on two plants every 10 meters, working diagonally through the field.
When to spray
Different pest problems will have different pest/predator thresholds (advice required from Zim Cotton Board)
When plant damage is obvious
When pest numbers are noticeably high
Controlled Spraying;
Spraying should be done when there is a significant pest challenge.
The application of pesticides should be controlled because the application of toxic chemicals not only kill pests, they also kill pest predators and surface and subsurface dwelling living organisms that play a part in the food cycle that provides the crops with nutrients.
Pest predator habitat should be avoided during spraying so that the pest predator populations can be maintained.
If the same chemical is used too often, pests can build up a resistance, so it is important to alternate between at least two different options.
Summary;
The basic practices used in Organic Farming are simple. They are also necessary in order to provide ideal conditions for the natural cycles to occur.
To re-cap, the basic practices are;
Mulching
Composting
Inter-cropping
Crop population planning
Integrated Pest Management
What we wish to achieve by using these practices;
Soil conditions ideal for;
The supply of plat nutrients for improved crop yields without the need of fertilizers
The ability of the soil to capture and retain rainwater
Additional plant nutrients by making and using compost as an organic fertilizer
A balanced plant community in which plants have specific roles
Improving and maximizing crop yield potential by ensuring we do not overpopulate or under populate fields
Responsible management of pests to ensure maximum yields are achieved
Making sure that our soil resource is cared for, to maintain fertility
Grant Norvall
9th June 2008
