Basics Of Fertilizer Applications

"Hi, I am a young lady who wants to start farming, but I understand very little about fertilizers. Please explain to me what influences the type of fertilizer to use, when, and why?"

 Anne, Rongai

Hi Anne, thank you for your inquiry. Several factors influence the type of fertilizer to use and they are the type of soil, the crop you wish to grow, and the weather of the location.

Soil

As you may know, soil is a reservoir of nutrients. But those nutrients are either depleted or not readily available – these contribute in the type of soil PH you have. The PH is and can be affected by the following:-

-Use of inappropriate sources of fertilizer that may lead to soil acidification.

-Use of unbalanced nutritional programs which supply excess nutrients resulting to poor growth and yields.

-Applying fertilizers based on seasonality either dry or rainy and not based on nutritional requirements of the crop. Thus nutrients are not applied in the optimal moment thereby losing effectivity.

-Applying lower doses than necessary.

Acid pΗ of 4.5-5 limits the availability of nutrients and reduces cation exchange capacity. Crop yield, root development and health improve with higher pH levels. Lower pH leads to malformed roots, low yields and high incidence of diseases. Higher pH contributes to healthier roots, low incidences of diseases, and higher yields.

Crop

There is a need to understand the crop you wish to grow and it’s nutrient removal requirements that will influence maximum growth and yield. There are several factors to consider while selecting your fertilizer use and application. These are:-

a). Yield – nutrient offtake during harvest

b). Soil (fertility/ pΗ/ CEC) – these determine the availability of nutrients in the soil.

c). Season – loss of nutrients due to leaching during rainy seasons. Nutrients are not available during dry season.

d). Shadow – lower yield potential in farms that have trees. Thus lower nutrient requirement.

e). Biomass recycling- input of nutrients from organic matter i.e crop residues, compost, litter etc.

f). Plant growth (stem, branches, and leaves) – nutrient fixation in the tree's structure.

A complete nutritional program considers that to sustain yield during the time; it will be necessary to apply more fertilizer and/or nutrients than what is removed with the harvest to ensure a continued supply of nutrients.