-Each sample is obtained by collecting small sample to a depth of 0-15cm using a hoe.
-The 5 soils are put in a basin and mixed thoroughly before 1 kg soils is removed and put in a clean container.
-These are taken for analysis in a laboratory. If however a farmer has access to the mobile soil scanner, he will simply call and the analysis will be done on the farm. The scanner also provides fertiliser application instructions.
Soil sampling and analysis starts from experts visiting the garden, where samples from all parts of the garden are taken. While this is happening such areas shouldn’t have any trace of organic manure like cow dung, chicken dung or any other fertilizer as these could compromise the final results.
Experts look out for the PH which is the acidity of the soil, organic matter, NPK, sodium, calcium and the proportion of sand clay and silt in addition to physical properties.
To maintain soil fertility farmers should apply both organic and inorganic fertilizers. Organic fertilizers can be got from cow dung, chicken droppings and goat droppings.
Soil evaluation gives levels of the following soil properties
Soil pH stands for, organic matter, nitrogen, phosphorous, potassium, sodium, calcium, magnesium and sand, silt and clay.
These are used to forecast soil management requirements
-pH: gives the levels of soil acidity. Currently, our soil is acidic requiring amelioration – using agricultural lime to pH6. Best material to use is dolomite, at a rate of 1-2 tonnes per acre or about 1/3 kg around each plant or a cup in a planting hole. Wood ash, or calcite may also be used. Application at least one month before planting, incorporated in soil using a forked hoe.
-OM – Organic Matter- also very low in our soil should be at least 3%- coffee husks, composts, crop residue, livestock manure- used at the rate of 5-10 tones per hectare- or 1-2 basins in a planting hole.
-N- nitrogen –also highly deficient in our soil – should be at least 0.2%- vital for vegetative growth. It is lost from soil through rain and high temperatures. Highly required at vegetative stage. At planting only 20-50g/hole but at vegetative stage – about 200-300g/hole. This can be got from NPK fertilisers and home processed manure.
-P- phosphorous – highly deficient in our soil due to high soil acidity, high temperature, global warming, also low organic matter. Highly required at planting stage, around 200-300g/hole. It promotes root growth.
-K-potassium. It is also becoming deficient as it is easily lost through rain and harvests. Required very much at fruiting stage to cater for quality of produce i.e cup taste or sieve size of coffee of fruits. Up to 300g around each plant for perennial crops. Get Potassium fertilizers from recommended agri-inputs stores.
-Ca and Mg – Calcium and magnesium – are also liming materials. Provided when putting the pH right. These can also be got from agri-input stores
-Sand, silt and clay: also influence plant growth regulate air and water spaces in soil – required for soil air, soil water and consequently root proliferation. Importantly – soil must breathe for life processes. Organic matter and soil tillage moderate the function of sand, silt and clay
Proper fertiliser usage
According to Kitungulu, to get the best out of fertilizer use, the following are important:
-Use the right seed variety, this can be known by consulting your seed supplier
-Good land preparation, this includes early ploughing before rains set in
-Appropriate weed management, this involves timely weeding
-Pest and disease control, because presence of pests affects the balance of nutrients in the soils
-Best post-harvest handling.
For appropriate nutrient use follow the 4R nutrient stewardship.
-Right source of nutrients
-Right time/stage of plant growth
-Fertiliser applications should be done at the beginning of rainy seasons.
-Not cost effective to irrigate without fertilization
-Not to fertilise in acid, compacted, dry soils.
-Use soluble fertilisers (N&K) in split doses.
-Intensification necessary when fertilizers are used (more plants per unit area)
-Farmers’ training needed in use of fertilizers and soil sampling for analyses.
Other fertility enhancers
-Practice crop rotation by changing seasonal crops grown on each block every season. For example, if you grow maize in the first season, grow legumes like beans the second season.
-Plant shade trees to reduce impact of the sun
-Mulch the soils to prevent over evaporation of water from the soils
-Dig trenches, contours and canals to help in water capture and retention, plus stopping soil erosion.