F.A.Q.

A fertilizer is any material, organic or inorganic, natural or synthetic, that supplies plants with the necessary nutrients for plant growth and optimum yield.

They are natural materials of either plant or animal origin,   including livestock manure, green manures, crop residues, household waste, compost, and woodland litter.

These are fertilizers mined from mineral deposits with little processing (e.g., lime, potash, or phosphate rock), or industrially manufactured through chemical processes (e.g urea).

Continued use of organic fertilizers results in increased soil organic matter, reduced erosion, better water infiltration and aeration, higher soil biological activity as the materials decompose in soil, and increased yields after the year of application (residual effects). Proper handling of organic fertilizers enhances their quality and effectiveness.

Mineral fertilizers on the other hand immediately supply nutrients needed by crops. Basal fertilizers contain elements required for good crop establishment and early growth while top‐dressing can be done through split applications depending on visible hunger signs and/or moisture availability. In risky environments, spot application of small amounts of N fertilizers improves fertilizer effectiveness.

Organic fertilizers support the growth of micro-organism like nitrogen-fixing bacteria, phosphorous solubilizing mychorrizae and bacteria among others. These Soil Microbes (Micro-organism) operate through multiple means to:

• Improve nutrient availability e. g fixed Phosphorous and Calcium
• Improve water penetration (heavy soils) & water retention
• Reduce root disease- The incidence and severity of root disease is an indirect assessment of soil health. Disease suppression is related to a global increase in soil microbial biomass. A large biomass creates a competitive environment deleterious for the pathogens.

Chemical fertilizers have high acid content like sulfuric acid and hydrochloric acid. This high acid content results in the destruction of the nitrogen-fixing bacteria, which is helpful in supplying the nitrogen to a growing plant. Generally, soils with low organic matter is characterized with low microbial activities. Organic matter is required by the micro-organism for them to thrive.

More often, both should be used in combination. This is because the best response to fertilizer use is obtained if the soil has a high inherent fertility level (high organic matter status). Mineral fertilizers may be used more efficiently by crops growing on soils with adequate amounts of soil organic matter supplied by organic fertilizers. Additionally, the effectiveness of Organic Fertilizers in specific nutrients supply can be improved by combining them with mineral fertilizers to attain the critical nutrients value for example as ammonium‐ nitrate or urea to enhance Nitrogen.

It’s therefore paramount that the grower does soil analysis at the beginning of the planting season to establish the nutritional status of the soil and avoid indiscriminate use of chemical fertilizers. This is because, more often than not, some elements are predominantly present in the soil that are have low soil organic matter content but are in forms that cannot be readily used by the crop. In such soils, increased use of the chemical fertilizers does not ameliorate the situation.

Also, if the soil has poor CEC ratio, more nutrients are lost through leaching to the deep soil layer, and are not accessed by the plants roots.

In summary:

• The amount of NPK supplied to the crop should be guided by the plant requirement and the soil nutritional status.
• Excessive use of chemical fertilizer does not always guarantee better crop performance due to fixation and leaching effect.
• Use of organic fertilizers will ensure that the crop is supplied with optimal conditions for growth in complementing the use of chemical fertilizers.
• Use of organic fertilizers ensures that the chemical fertilizers are used judiciously and not indiscriminately. This would ultimately lead to reduced use of the chemical fertilizers.
• Use of organic fertilizers ensures that the soil is sustainably productive.

Applying the correct amount of NPK is important for optimum growth and profitable crop production. The recommendations are therefore based on crop nutrients utilization and response to the applied rates, and will vary on the crop yield and variety.

1. Increased soil acidification e.g. from use of phosphate and nitrates.
2. Nutrients loss through leaching, nitrification e.g. nitrates, volatilization e.g. Use of ammonium.
3. Induced unavailability of specific elements e.g. Phosphorus , Calcium, Potassium.
4. Survival of soil micro-organism is compromised.
5. Reduced soil organic matter will cause poor soil structure, poor soil retention capacity for both water and nutrients.

Organic fertilizers: Soil fertility on smallholder farms is almost entirely dependent on locally available resources. Cattle manure, cereal and legume stover, and woodland litter are the commonly used organic fertilizers, but these are rarely applied in sufficient quantities to impact on crop yields. The use of high quality organic fertilizers is rarely practiced, although through research and extension activities in Africa, some farmers now include legume green manures or legume‐based fallows in crop sequences. The main advantage of using organic fertilizers is that, compared to mineral fertilizers, they are usually available on or near the farm at very little or no cost other than labor costs of handling, transportation, or opportunity costs of land used for their production.

Inorganic (mineral) fertilizers:   Mineral fertilizers need to be applied to crop at least two times within a growing season (split application), either basally at planting or top‐ dressed during vegetative growth. The amount of inorganic fertilizer used in most smallholder farming systems falls far below standard extension recommendations, due to poor purchasing power, risk aversion due to poor and unreliable rainfall, and lack of significant returns. When available, fertilizer use is not overly labor intensive, thus allowing time for other tasks (or for earning income elsewhere).

The method and timing of fertilizer application is an essential component of good farming.

For organic materials, decomposition rate and timing of application influence the release of nutrients to the crop. Organic fertilizer application methods include broadcasting, banding and spot application (or side‐dressing). Broadcasting requires less labor and helps to evenly cover the field surface before incorporation into soil through plowing or hand‐hoeing. Incorporation generally increases the fertility status of the whole plow layer. If the quantity of organic fertilizer is limited, it may be banded along furrows or spot applied, but the seed needs to be placed away from the fertilizer. Side‐dressed organic fertilizers are not likely to have much immediate effect due to delayed nutrient release.

Mineral fertilizers can be applied by hand or with application equipment. When hand applied, it is essential to distribute the fertilizers uniformly and at the recommended rates to avoid over‐ or under‐fertilization. Application equipment needs proper adjustment to ensure uniform spreading. Broadcast fertilizer should be incorporated after application to enhance effectiveness or to avoid evaporation losses of N. With banding or spot application, take care that no fertilizer is placed too close to either the seed or the germinating plant, to avoid damage to the seedling or roots.