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Why you should apply organic fertilisers
A farmer uses dry maize stalk for mulching his garden. PHOTO/MICHAEL J SSALI
What you need to know:
- Who never takes their children for vaccination? Do we really expect our crops to grow normally without any pest or disease attack?
It is quite common nowadays for some activist groups to tell farmers to avoid applying manufactured pesticides, herbicides, and fertilisers. They claim that the agro-chemicals destroy the soil and that they are dangerous to food consumers and the environment.
But is it really possible to carry out successful farming here in the tropics without the use of agro-chemicals? Who entirely keeps away from chemicals all their lives? Who never swallows pills or drinks bottled drugs from hospitals and pharmacies?
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How sure are they that the pills and liquids are not ‘chemicals’? Who never takes their children for vaccination? Do we really expect our crops to grow normally without any pest or disease attack?
Pests and diseases
The hard fact is that crops get attacked by pests and diseases that require medicine. Our soil fertility inadequacies must be addressed and put right for us to grow crops successfully.
The ultimate aim of commercial farming is to maximize output and profits, bearing in mind that the products must be safely farmed and entirely harmless to the consumers and the environment.
In the book East African Agriculture, (Ngugi D N, Karau P K and Nguyo W) it is written that to carry out successful farming farmers may use organic and inorganic agricultural inputs. It is not common to find land whose soil is naturally fertile and does not require fertiliser usage.
Organic manures
Organic manures include things such as farmyard manures – urine, excreta and droppings (poultry) plus their beddings. These manures, according to the book, are an important source of nutrients such as nitrogen (N) phosphorus, (P) and potassium (K).
In addition, farmyard manure adds organic matter into the soil. It has beneficial effects on soil structure. The quality of farmyard manure, says the book, varies according to method of preparation, amount and type of bedding material used, type and age of livestock among other factors.
Similarly, farmyard manure which contains nitrogen-rich plant litter such as that of leguminous crops will be richer in nitrogen and phosphorus than farmyard manure made using wheat straw as bedding material.
It is further mentioned in the book that mature cattle tend to excrete more nitrogen in their urine than young stock. Poultry manure is said to be richer in nitrogen than young stock. Poultry manure is richer in nitrogen and phosphorus than that of other common domestic animals.
Farmyard manure has to be applied on the land in large amounts owing to the low nutrient content compared with inorganic fertilisers. The effects on the plant growth are slow in coming. Farmyard manure should be stored under a rain and sun proof cover to prevent rapid rundown on quality through leaching and oxidation of nitrogen.
Compost manure
Another form of organic manure is compost manure. This is plant and other organic waste which has decayed. Compost is prepared by piling plant residues either in a heap or in a pit. The materials should be turned over at intervals to facilitate even decay.
The book goes on to say that with very dry, low nitrogen vegetable matter such as dry maize stalks it is sometimes necessary to add a nitrogen source, e.g. Ammonium Sulphate, to encourage bacterial decomposition.
Temperatures must be controlled during decomposition so as to come up with quality stuff. Too high temperatures can be dampened by sprinkling water on the compost. Once ready, compost manure must be protected from both rain and sunshine in order to conserve nutrients.
Green manure
Yet another form of organic manure mentioned in the book is green manure which is the incorporation of plant material into the soil while still green.
Upon decay green manure enriches the soil with organic matter and to a lesser extent plant nutrients, notably nitrogen and phosphorus.
Some period of time must elapse between the incorporation of the green manure crop in the soil and the planting. This gives time for the decomposition of the green manure crop. Sunflowers and various legumes have occasionally been used as green manures.
Mulches
East African Agriculture also mentions mulches among organic manures. This comprises plant materials such as straw, maize stalks, banana leaves or any other grasses and leaves which are used as soil cover mainly for conservation of soil cover mainly for conservation of soil moisture and prevention of soil erosion.
Farmers should also be free to use inorganic or manufactured fertilisers. These are artificial manures containing plant nutrients in high and definite concentrations. Inorganic fertilisers may be divided into two types --- straight fertilisers and compound fertilisers.
Straight fertilisers supply or contain one major nutrient such as nitrogen, phosphorus, or potassium --- while compound types supply more than one major nutrient. Compounds are often manufactured for specific crops whose nutrient requirements are known.
As can clearly be seen from the explanation in the book both organic and inorganic fertilisers contain the chemicals, nitrogen, phosphorus, and potassium. Whether a farmer uses organic or inorganic fertilisers the basic thing is that both use chemicals.
Why you must test your soil
At the recent PEWOSA Agri-Business Exhibition in Masaka, soil scientist Eseri Nankya of Naro emphasized the importance of soil testing before applying fertilizers.
She said farmers can seek guidance from their respective agricultural services extension officers about where to go to have their soil tested. “Land is different in many parts of the country and it has different deficiencies,” she said. “Soil samples should therefore be taken for testing for the farmer to get correct information about which fertilisers are suitable for his farm.”
A senior lecturer at the University of Hull, Mark Lorch, has said, “Chemicals are good for you. Manmade or natural, tasty or toxic, they are all chemicals. The terms ‘chemical’ and ‘poison’ have become interchangeable in the popular consciousness and as a result the whole subject of chemistry has become tainted with unpleasant connotations.”
He says that in many of the food crops that human beings consume –apple seeds, Irish potatoes, pears, and courgettes -- there are natural chemicals that are toxic to humans. However, they are usually present in very small amounts, far below the harmful dose. “Just because a chemical is present does not mean that it is harmful in the amount present,” he says.
EXPLAINED: Why farmers should apply organic fertilisers
According to a recent report of the Food and Agriculture Organisation (FAO) titled: “Crop losses due to disease and their implications for global food production losses and food security,” pathogens, wild animals, birds, rodents, and weeds are altogether responsible for losses ranging from 20 percent and 40 percent of global food productivity. The dictionary meaning of pathogen is “a thing that causes disease.”
For crops and farmed animals this may be in the form of pests, fungi, parasites, and bacteria. Farming is a constant battle between the farmer and weeds, pests, parasites, and bacteria. Often farmers also have to fight wild animals, rodents, and crop eating birds.
Manufactured agricultural inputs are an alternative, efficient, tool for farmers to use in the fight against different obstacles to successful farming. It is however very important that they are used carefully and according to manufacturers’ application instructions.
Organic manures
Organic manures include things such as farmyard manures – urine, excreta and droppings (poultry) plus their beddings.
These manures, according to the book, are an important source of nutrients such as nitrogen (N) phosphorus, (P) and potassium (K).
