A good friend of mine called me yesterday and requested me to give him some insight on fertilizer program for Tomatoes as I had done on maize. Because he is a good friend and I also have many good friends, I decided to report my findings to everyone who would be keen to read and follow.
Fertilizer Program On Tomato Production
From scientific research. I asked him how many tons he targets to harvest from 1 acre and his response was 50t !ย  This is a serious farmer and I believe he will achieve it because 50t is doable. I remember I harvested 20t of Tomatoes Assila variety in quarter acre green house =80 tons in an acre . So it’s not rocket science.
An acre is 4000mยฒ . Let’s assume its measurements are 80m by 50 .
Inter-row spacing =90cm and an intra row of 40cm .
What’s the tomato plant population per acre ?
80/0.9=88 rows .
Each row is 50m/0.4= 125 plants x88= 11,000
Let’s take 10% loss
Final population will be 9,900. Let’s take 10 000 for ease of calculations.
A tomato plant produces over 150 fruits .
Let’s just take 100 fruits of 80g = 8kgs per plant ร— 10,000 = 80,000kgs
Potentially, it is possible to produce 80t .
My friend is looking for 50t which according to our calculations its 62.5% of the potential yields
So it’s doable. Let’s now move to the next step and find out what fertilizer regime should he be on .
Luckily I was able to find a scientific evidence of Nutrients removal from the soil for Tomatoes and therefore I have good news for my friend and others .
To produce 50t of Tomatoes in an acre , the nutrients removal from the soil is
  1. Nitrogen 64.8kgs
  2. Phosphate 25kgs
  3. K2O 144kgs !
  4. S 34
  5. Mg 20
  6. Ca 5
Let’s assume his soil has nothing.
What fertilizer program does he require to adopt?
We look at the available fertilizer which are
  1. DAP
  2. 17.17.17
  3. C.A.N 26% N
  4. Urea 46% N
  5. MOP 61% K2O.
  6. Ammonium sulphate 21%N 23 S
  7. CaNO 3 N 15% Ca 18%
  8. Magnesium sulphate Mg 9.5% . S 12%
What is required most is Potassium!
P requirement is only 25kgs.
50 kgs of DAP has 23kgs of P2O5 and this will be enough to meet the requirements.
50kgs DAP has 9kgs of N and therefore N deficit will be 64.8-9 =55.8
Let’s take Mg requirements of 20kgs .
Our source has 9.5kgs and therefore we need 200kgs .
This will also give us 24kgs of S and our S deficit will be 10kgs .
We move on to Nitrogen. Since we have 10kg S deficit, we select a fertilizer with both N and S which is 1 bag of Ammonium sulphate.
This will give 11.5 S and 10.5 N and our S requirement is fully met .
Nitrogen deficit will be 55.8-10.5 = 45.3 .
We still need to meet Ca requirements of 5kgs which we can get from 50kgs of CaNO3 which will give us 9kgs Ca and 7.5N
N deficit = 45.7 – 7.5 = 37.8 kgs
We fill this by using Urea 82kgs .
We move on to Potassium which 144kgs and since our soils are rich in k, we work on 60kgs per acre .
100kgs of MOP will meet this requirement and our program is done .

Summary On Fertilizer Program On Tomato Production Per Acre

Base dressing .
  • 1 bag of DAP and 2 bags of MOP properly mixed with soil .
  • Topdressing.
  • Urea 82kgs
  • Magnesium sulphate 200kgs
  • Ammonium sulphate 50kgs
  • CaNO3 50kgs
Apply in 3 top dressing regime as follows.
  • 3wks after planting
  • At 2 months
  • At onset of harvesting.
Mix all the ingredients divide by 3 to apply in each application.
I haven’t checked how much the above fertilizers would cost but it should be on the range of ksh 80,000 per acre .
This might appear shocking but it’s acceptable for 50t per acre .
What’s the expected gross sale if my friend would sell his Tomatoes for 20 Bob per kg ?
50,000kg @ 20 = 1,000,000 .
What is the cost of 80k against 1million.
The fertilizer cost can be reduced if soil analysis is done and reduce on supplements.

Points To Consider on Fertilizer Program On Tomato Production Per Acre

Designing a fertilizer program for tomato production per acre requires considering the specific needs of the tomato plants at different growth stages. The following is a general guideline for a fertilizer program on tomato production per acre:

Pre-Planting Stage: Before planting, conduct a soil test to determine the nutrient levels and pH of the soil. Based on the soil test results, apply any necessary lime or sulfur to adjust the pH to the optimal range for tomato growth.

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Basal Application: At the time of planting, incorporate a balanced fertilizer with a ratio like 10-20-10 or 14-14-14 into the soil. Apply around 2 to 3 bags (50 kg each) of fertilizer per acre.

Side-Dressing: During the growing season, side-dress the tomato plants with a nitrogen-rich fertilizer to promote vegetative growth and fruit development. This is typically done 3 to 4 weeks after transplanting. Apply around 1 to 2 bags (50 kg each) of ammonium sulfate or urea per acre.

Fruit Setting and Development: During the fruit setting and development stage, potassium is essential for improving fruit quality and disease resistance. Apply around 1 to 2 bags (50 kg each) of muriate of potash (potassium chloride) per acre.

Calcium Supplementation: Tomatoes are susceptible to calcium-related disorders like blossom end rot. To prevent this, apply calcium nitrate as a foliar spray during fruit development. Dissolve around 2 to 3 kg of calcium nitrate in 100 liters of water and spray the tomato plants.

Foliar Feeding: To provide additional micronutrients and improve nutrient uptake, consider foliar spraying with a complete micronutrient solution every 2 to 3 weeks during the growing season.

Organic Matter: Incorporate organic matter like compost or well-rotted manure into the soil to improve soil structure and fertility. This can be done during land preparation or as a topdressing around the plants.

Irrigation Management: Proper irrigation is crucial for nutrient uptake by the plants. Ensure consistent and adequate water supply to avoid nutrient imbalances and stress-related issues.

Adjustments Based on Soil Test: Throughout the growing season, monitor the tomato plants for any nutrient deficiencies or excesses. Based on visual observations and additional soil tests, make adjustments to the fertilizer program if needed.

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Article Credit: David Ndegwa

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