Posted on August, 2, 2017 at 11:15 am
By Lominda Afedraru
Application of different types of fertilisers by farmers who are growing different varieties of plants is essential in the production of crops used for food, feed, fibre and fuel.
Most of these nutrients are absorbed by the crop but when applied in excess, they can be lost to the environment through volatilisation into the air, leaching into ground water, emission from soil to air, and runoff into surface water.
These losses can be reduced by adoption of best management practices that increase the nutrients’ accessibility for plant use, enhance plants’ ability to uptake nutrients and more closely match nutrient applications with agronomic practices.
There are different types of fertilisers on the Ugandan market for farmer application depending on the types of crops ranging from cereals, vegetative propagated crops and vegetables among others.
Fertiliser types
Simon Alibu, an agronomist majoring in cereals research at National Crop Resources Research Institute (NaCRRI) in Namulonge explains the various types of fertilisers farmers use to boost their yields include the complete fertiliser containing all the three nutrients namely nitrogen, phosphorus and potassium (NPK).
This type of fertiliser is mainly applied by farmers growing cereal crops such as rice and maize and it is advisable for farmers to apply it at the ratio of 17 per cent each usually during planting.
Farmers growing rice are advised to apply 50 kilogrammes of Nitrogen and 30 kilogrammes each for phosphorus and potassium.
Another type of fertiliser is Single Superphosphate (SSP) which contains 50 per cent phosphorus nutrient and Double Supper Phosphate (DSP) which contains 46 per cent prosperous.
Another type is Diammonium Phosphate (DAP) which is the world’s most widely used phosphorus fertiliser. It is water soluble and can be sprinkled on the plants.
Others are Urea which contains 46 per cent nitrogen and Muriate of potash containing 50 percent potassium chloride.
Farmers growing cereal crops can mix either of the fertiliser and apply the same in the farm but the ratio has to be 30 kilogrammes for each one of them.
According to Alibu, different types of crops demand different nutrients. In the case of vegetative crops like banana, cassava, coffee and sweet potato among others, fertiliser containing nitrogen is good to apply to the leaves of the plant to develop and phosphorus is good for root and stem development.
Farmers growing rice are advised to apply NPK at the planting time and the second application should be when the plants are two months old.
This is usually done by broadcasting the fertiliser in the entire farm.
Farmers growing maize are advised to apply DAP in its particle form at the time of planting where farmers are expected to make a hole and drop fertiliser in the hole, cover the it and plant the seed on top or on the side.
When the plants have grown for four weeks, then Urea can be applied using broadcasting method.
Maize farmers who use fertiliser coupled with good agronomy practices like prompt weeding will be able to harvest seven tons of maize per acre but most farmers usually harvest three tons per acre because they don’t follow the required.
For those growing rice they will be in position to harvest six tons of rice per acre with application of fertiliser.
Other types of fertiliser are folia types responsible for supply of micro nutrients to plants such as green vegetables, flower and passion fruits among others.
Farmers growing passion fruits and vegetables can apply folia fertiliser such as super green, super grow, veg max which is spread on plant leaves to avoid pest and disease infestation.
It is known that not many farmers in Uganda have adopted use of fertiliser application.
There are initiatives by scientists in encouraging farmers in minimum fertiliser application for increased production.
One such initiative is by soil scientists from the National Agricultural Research Laboratories (NARL) Kawanda where they are using the optimum fertiliser application in calculating what quantity of fertiliser to apply in a given land acreage.
Innovation
The scientists have come up with Uganda Fertiliser Optimisation Tool (FOT). This is a computer-based tool used to calculate the required amount of fertiliser as per the monetary fund allocated for a specific agricultural activity per unit hectare. It also indicates what a farmer will apply in a given hectare.
Dr Cranmer Kayuki Kaizi, from NARL, explains that what is considered is the land area the farmer wishes to plant for a particular crop and expected commodity value at harvest, the cost of fertiliser and the finance available for the farmer to purchase fertiliser.
FOT was developed for crops such as sorghum, beans, rice, groundnuts and maize.
Currently, the team is in the process of developing this tool to cover other crops.
It is availed to extension workers who show farmers how to calculate the fertiliser rate for a particular crop and estimate average yield and net returns using a mobile phone.
“The most important aspect is the land. We have always encouraged farmers on this issue,” said Kaizi.
Yields
Calculations are made with MS Excel, and a farmer will know that if he or she applies 50kilogrammes of Urea on one hectare, the yield will amount to 44kilogrammes of maize grain per hectare.
For the case of rice, if the fertiliser is purchased at $60 (Shs216, 900) per hectare, the farmer will be in position to reap $700 (Shs2, 520,500) per hectare.
Therefore, the tool enables farmers to apply fertiliser depending on the economic return.
The tool also helps guide the farmers on which crops to invest in and the fertiliser usage.
In Uganda, it has been tried in Kapchorwa, Aleptong, Arua, Tororo, Sironko and Apac districts and it is to be introduced in Kisoro, Kabale and Ntungamo districts.
Therefore, it is recommended that smallholder farmers should maximise fertiliser use alongside organic manure to improve soil nutrients.
Tips for fertiliser use
Fertilising pastures
Lawn fertilisers should be spread evenly and applied according to manufacturer’s instructions. Water is required if the weather is dry. To help the nutrients penetrate the soil, aerate the lawn before applying fertiliser. This also helps improve surface drainage and prevents compaction.
Apply more fertiliser for light soils
Light and free-draining soils, usually sandy in composition lose nutrients more quickly than other types, especially in rainy spells. Apply fertiliser more frequently on these soils, especially nitrogen fertilisers to maintain levels.
Apply less fertiliser for clay soils
Heavy clay soils and soils containing a lot of organic matter require less frequent application. This is because both substances act as reservoirs holding the nutrients and releasing them slowly over time to the plants.
Acidic or chalky soils
Phosphates and potash become more soluble in an acid soil, making them easier for rain to wash away. In chalky (alkaline) soils, phosphate becomes insoluble when mixed with the calcium present in chalky soils. In both cases, divide the application into two or three and apply over the growing season.
Trees
To feed a tree, apply fertiliser evenly in the area under the canopy. The tree’s feeding roots tend to be near the surface in that area. A gentle shallow aeration will improve penetration of the nutrients as well as improve surface drainage and reducing compaction. Avoid damage to the roots by keeping shallow.
Don’t keep lime and fertiliser together
Never apply or store fertiliser and lime together. There will be a chemical reaction between the lime and the nitrogen in the fertiliser, making neither effective. Especially when growing vegetables, check and adjust if necessary the pH (acidity) of the soil. Acid soils may contain nutrients but they are less available to the plants.
Feed at the right time
Only add fertilisers to plants before and during the growing season. Applications made after the season will just be washed out of the soil and not do any good unless you use an over-winter green manure crop to hold them for the next season.
Boosting failing plants
If plants are showing signs of nutrient deficiency then you can give a boost using liquid fertilisers that are absorbed more quickly by the plant. Sometimes the problem isn’t the amount of nutrient available but a lack of micro-nutrients preventing take-up by the plants. Try a spray of seaweed extract of a dose of Epsom salts to release the nutrients.
Make your own liquid feeds
If you have comfrey or nettles available you can make your own liquid fertiliser by adding the leaves into a barrel of water and allowing them to ferment for three to four weeks. This will make a fertiliser high in potash, great for tomatoes and hanging baskets.
Adopted from gardenfine
Source: Daily Monitor