Converting N requirement per year to per week

[spoon89]

Hello Everyone,

Terribly sorry to bother you,

I am on the verge of conducting a pot experiment which would make use of soils deficient in some nutrients.
According to literature, I will require about 300 kg/ha of N per year as the standard requirement for the plant I am working with.

The soil surface area of pot is 2.5434 cm2, the pot will be placed on a concrete block of area 741 cm2.
I do not know how to calculate how much fertilizer would be required for each plant in g/plant and how much I would need to put in each pot weekly in mL.

Thank you very much for taking your time to respond to my inquiry, I appreciate your kindness in this regard.

[JohnS]

Fertilizing plants in pots is different than fields. In fields, the assumption is made that the roots draw from about the first 12" or 30 cm of soil. The fertilizer is applied on the surface so the concentration is not uniform with depth, but that is treated as the effective depth. Since pots are usually not that deep, the problem is whether you should judge by surface area or volume.

Please check the surface area of your pot. That sounds unbelievable small (less than 2 cm in diameter).

300 kg/ha would be 300 000 g/10 000 m² or 30 g/m² as a surface rate. As a volumetric rate assuming a 30 cm effective depth, it is 100 g/m³ or 0.1 g per liter of soil. Since 1 m² = 10 000 cm², that surface rate of 30 g/m² is 3 mg/cm². You will have to decide between surface and volumetric application rates. Note that fields are only fertilized a couple of times in a season. If you are going to use weekly application, you should use much smaller doses. But I can only help with the conversions; I am definitely not a plant expert. I am much better at growing the weeds and killing the plants.

[spoon89]

Apologies! That area is ridiculous, that was a typographical error.
the surface area in question is about 200 cm2 and on further studies I’ve come down to deciding if surface area or volume should be considered when making calculations for N input.

Your reply has helped me a lot, thank you so much.