To use organic or inorganic manure – which one?

Cow dung is an organic fertilizer. Photo/Michael J Ssali

What you need to know:

  • There is a big debate among farmers and consumers about whether the farmers should use organic or inorganic fertilisers. Some consumers claim that it is healthier to consume food produced using organic fertilisers other than food produced with the use of synthetic or chemical fertilisers.

When we grow crops in the field they feed on soil nutrients and when the crops are harvested, they leave the field with the nutrients that they consumed. 

This is what Joseph Nkandu, a trained agriculturist and executive director of National Union of Coffee Agribusiness and Farm Enterprises (NUCAFE), said during a recent interview with Seeds of Gold. 

“When coffee is harvested and taken away from the farm, it goes off with the soil nutrients that it consumed to grow. Therefore some effort must be made to replenish the soil from where the coffee got its nourishment by applying manures and fertilisers.”

Organic or inorganic
Agriculturists describe fertilisers as organic or inorganic materials of natural or synthetic origin that are added to the soil in order to supply elements that are essential for good plant growth. 

Some soils are by nature very fertile and may support plant growth for many years without application of any fertiliser but with repeated cultivation of crops on the same land the soil is bound to degenerate after some time.

A farmer uses pigsty manure to fertilize his banana garden. Photo/Michael J Ssali

Why use fertilisers 
This means that farmers should enhance their garden’s soil fertility by continuous application of manures and fertilisers. There is a big debate however, among farmers and consumers about whether the farmers should use organic or inorganic fertilisers.  

Some consumers claim that it is healthier to consume food produced using organic fertilisers other than food produced with the use of synthetic or chemical fertilisers. They claim chemicals are not natural and that they could be harmful.

Nkandu says farmers may use organic or inorganic fertilisers as long as they have the soil in their gardens tested before applying them. 

“It is important for the farmer to be sure of what is missing from the soil first before deciding on what to use as fertiliser,” he says.

“When a soil analysis is made the farmer gets to know better what to do instead of applying fertilisers blindly. The problem with people who stick to using only composite or livestock manure is that they are not really sure of the right amount of the fertiliser to apply which is not the case with manufactured fertilisers. It is important to apply the right fertilisers and in the right amounts,” says Nkandu. 

Chemical fertilisers 
He further said it is not correct to say that chemical fertilisers are dangerous. “If they are correctly applied they are entirely safe. You see even us humans we go to hospitals and we are treated with manufactured tablets and creams which are all chemicals.

In fact some herbal concoctions made locally may be extremely poisonous, since quite often our local herbalists don’t prescribe a dosage,” he says.

Anthony Ssekaddu, a trained agriculturist and production manager of Kibinge Coffee Farmers’ Cooperative Society, which has chosen to use organic farming practices, told Seeds of Gold, “We opted to go organic because our consumers said they want organically grown coffee. We have been skilling our farmers in making composite manure, using livestock droppings, and how to make organic pesticides. We have also contracted a company, Vemipro Organic to supply our farmers with organic fertilisers, organic pesticides, and organic fungicides. We have to be sure that the products work and that they are certified by National Agricultural Research Organisation (Naro)”

He went on to reveal that when a product is obtained its efficacy is first tested at the cooperative’s demonstration garden at Kiryassaaka in Kibinge Sub-county. The cooperative society also grants loans to its members to purchase trucks of cow dung to apply as manure in their coffee garden.

Mulches are a form of organic fertilizer. Photo/Michael J Ssali

Use both types 
Eseri Nankya, a soil scientist who works with Naro has however told Seeds of Gold, “The best thing is to use both organic and inorganic fertilisers. Organic fertilisers like livestock droppings and composite are good for the soil but usually they have low nutrient content.

Apart from that their nutrients are slowly released into the soil with the result that in many cases it may take several months for some crops to begin using the nutrients which is not the case with chemical fertilisers whose action is direct and quick.” 

Her recommendation is that the organic fertilisers should be applied as a cover to the inorganic fertilisers. Nankya went on to say that as often as possible farmers should seek to have their soil analysed in the laboratories to find out how much and which fertiliser to use. 

“It is also good for the farmer to have the organic manure examined to establish its nutrient content. A lot depends on the grass or fodder that the animal ate. This is the same for those who use composite manure; some of the grasses and peelings used are not necessarily nutritive – like sweet potato peelings or other such rubbish may not be good manure.” 

She went on to warn farmers against random application of inorganic fertilisers. Too much of anything is bad and if too much inorganic fertilisers are applied they could poison the soil. “That is why it is necessary for the soil to be tested before any application of fertilisers, whether organic or inorganic.” She regrets that currently soil testing facilities are not yet easily accessible to the majority of farmers in the rural areas.

Organic fertilisers 
Agriculturists define organic fertilisers as materials derived from rotten plants or livestock residues such as chicken droppings, cow dung, composite manure, animal beddings or farmyard manure, and mulches.

On decomposition, they become part of the soil and add nutrients to it which are used for plant growth. They improve soil structure besides being food for micro-organisms that aerate the soil.

They are easily available to most small scale farmers who keep small animals like sheep, pigs, goats and rabbits. As has been stated by Nankya they have a long residual effect, taking several months in the soil.

If large scale farmers want to use organic fertilizers they must hire labour to apply them because they are bulky. 

Nankya has said that using organic fertilizers carries the risk of transferring crop pests, diseases, and weed seeds. Their specific nutrient content is not guaranteed and the farmer cannot be sure which nutrients are really applied to the soil.

Inorganic fertilisers 
On the other hand synthetic or inorganic fertilisers release nutrients quite fast and the positive effects are quickly noticed by the farmer. They are not so bulky and the farmer normally applies small amounts per crop since they have high levels of nutrients. In many cases they are mixed with irrigation water and applied together. 

They provide plants with specific nutrients as stipulated by soil test results. If the soil lacks nitrogen or phosphate it is the nutrient that the fertilizers provide in greater quantities. They are easy to store in a building and not like cow dung or pig droppings which usually smell.  

Inorganic fertilisers however must be applied very carefully, following manufacturer’s instructions. If they are not properly applied they can become toxic and kill the crops. They may kill useful organisms in the soil. They can be easily washed away by running water. 

They are made to last a few months in the soil and quite soon afterwards the farmer must go back to the shops for more.