• When we apply granular basal fertiliser such as compounds fertiliser like Compound D in maize we apply it per plant using fertiliser cups. Usually we divide the amount of fertiliser in grams per hectare by the plant population to get the amount of fertiliser in grams per plant.
e.g. 300kg per hectare of compound D in a maize crop spaced at 75 cm inter-row and 25cm within the row 300 000g/53 333 plants = 5.6 grams per plant. If I wanted to conduct a maize experiment in a pot I would just apply this amount of fertiliser per pot.
• However I could weigh the soil that the pot can carry and do a simple proportion as follows assuming that a hectare furrow slice weighs 2 200 000 kg of soil as follows:
300 000g fertiliser →→ 2 200 000 kg soil
X g fertiliser →→ 10 kg soil
= 1.36 grams per pot
In the first method a maize plant receives 5.6 grams whether it is growing in the field or in a pot with 2 kg soil or a pot with 10 kg soil. In the second method for a maize plant to receive the same amount of fertiliser as in the first method it has to be grown in a pot that carries 41 kg of soil. The amount of fertiliser increases with increase in pot size.
How can we reconcile this?? Which is the correct method for the determination of fertiliser per pot?
Your size pot should the same as volume and depth of maize root.and maize canopy in the field conditions. The amount of soil per pot depending on the volume of pot, soil bulk density. Then the amound of fertilizer is the same as applied in the field. If you use small pot you can calculate and apply the amound of fertilizer can be absorbed by maize at different maize growing stages as equivalent to the amount of soil in pot. The more you assume close to the fileld conditions the more good result you get.
Hi Sydney Mavengahama: If you are going to grow single plant in a pot than first method is OK. If some other crops such as paddy/wheats are being experimented than the soil weighing and application of fertiliser as per furrow slice weigh (second method is more appropriate.
Hi dear, an other approach that the previous answers did not tackle is to calculate the surface area of the soil in the pot and deduct the amount of fertilizer recommended on such area. (Fertilizer recommendations are mostly given Xkg/ha)
In potted studies, you always consider, the weight of the soil to calculate the quantity of fertilizer to be applied whereas for field studies, you calculate on area basis to apply the fertilizer. These are two different situations and conditions. Volume of the soil is constant in a potted study whereas it is unlimited under field conditions as there is no restriction for the roots to grow. In your case, 1.36 grams of fertilizer per pot is correct..
I have the answer but hardly any time, at the moment, as the answer is detailed.
In short, in pot culture, for attaining optimum plant growth the fertilizer requirements must be based on internal nutrient requirement of the plants rather than the weight of soil per pot or size of the pot. The approached is well tested and highly effective.
You have to estimate the population in acre first and then grow the calculated number of plants per pot according to the weight of soil in pot and then apply the second method for fertilizer calculation
The dosage to be used per area, for instance - hectare or acre, is related to the volume of the soil pots. Suggest macerate compost and mix it steadily with the soil, considering the small volume of soil that will be explored by the roots. Soon the driving period of the experiment should not be much long as this can negatively affect plant growth. Typically in an experiment in a greenhouse there is no limitation of water for the plant which favors the uptake of nutrients.
To get scientific and reliable results you need to do experiments in pots as well as in soils. First you need to calculate usual no. of plants in given area and similarly you have to divide and put the number in pots. Suppose in one acre of 2000 plants if u are applying 50 kg then divide it for single plants and apply in the pots as plants require standardized dose.
In addition to calculating the amount P to apply you also need to consider the P-fixing effects of the soil if you are using high amounts of soil.
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