Ask your Agronomist: Nutrients required to get best greenhouse tomato harvest

Bathlomew Rotich Kandagor, a farmer at Tugen Estate in Moiben, Uasin Gishu County tends to healthy tomato crops in one of his greenhouses. Tomato crops have a higher requirement for potassium than any other nutrient. FILE PHOTO | NATION MEDIA GROUP

What you need to know:

  • Its worth noting too that a tomato crop has a higher requirement for potassium than any other nutrient – almost twice as much as the requirement for nitrogen.
  • Nitrogen supplied both through calcium nitrate as well as the NPK fertilisers is critical in building the biomass required to support the crop throughout the growing period, thus increasing yield. In particular, for a tomato crop ,farmers should use the high K type of NPK, such as YaraMila WINNER.
  • At transplanting apply an NPK high in P such as UNIK 17; thereafter from beginning of flowering apply NITRABOR and WINNER ( or a soluble NPK with high K) once or twice a month till the crop begins to naturally senesce.
  • Therefore periodic application of NPK fertilisers during the growing season is important to ensure good productivity of high quality fruits.

Q : I have been growing tomatoes in the Isinya in an open field but I have now started greenhouse production. Kindly advise me on the best fertilisers for the green house production.

First of all, its important to note that a tomato crop whether grown in the open field or under greenhouse has pretty much the same nutrient requirement for the same target yield.

The only difference in this case would be the method of delivery of the nutrients.

Crop Establishment and Development

Like many other crops, a tomato crop requires phosphatic fertilisers with at least 30 per cent of the total nitrogen requirement at the transplanting stage to better develop the root system and aid in further nutrient uptake.

However, in the greenhouse system, given that the crop is on the ground for long period of time, application of P should not be a one-off affair but rather applied periodically, same as other nutrients.

It's worth noting too that a tomato crop has a higher requirement for potassium than any other nutrient – almost twice as much as the requirement for nitrogen.

Therefore periodic application of NPK fertilisers during the growing season is important to ensure good productivity of high quality fruits.

Influencing Yield and Quality
Fruit size, colour, texture and firmness are important attributes for a high yielding high quality tomato production. NPK fertilisers – soluble for fertigation or dry applied – containing secondary and micro-nutrients are recommended for tomato production.

At the beginning of flowering, application of calcium nitrate either though drip or soil is important to prevent blossom-end rot in the fruits and thus improve the total marketable yield.

Boron and zinc either supplied within the compound NPKs or separately as foliar fertilisers are important to improve flowering and fruit setting.

Nitrogen supplied both through calcium nitrate as well as the NPK fertilisers is critical in building the biomass required to support the crop throughout the growing period, thus increasing yield. In particular, for a tomato crop ,farmers should use the high K type of NPK, such as YaraMila WINNER.

This helps in improving the crops tolerance to moisture stress and even some fungal diseases, as well as improve the deep red colour and firmness of the tomato fruit.

The Fertilisation Regime

At transplanting apply an NPK high in P such as UNIK 17; thereafter from beginning of flowering apply NITRABOR and WINNER ( or a soluble NPK with high K) once or twice a month till the crop begins to naturally senesce.

For fertigated application take care not to increase the EC of the medium/Soil to more than 2.5 Ms/cm as tomato can be sensitive to saline conditions.

For crop specific fertiliser recommendations, please consult the following agronomists in your area:

Western and Nyanza: Daniel Muli, 0702466343

Rift Valley: Dennis Nyandaya, 0702466372

Central: Robert, Ngatia, 0702466318

Vitalis Wafula, Agronomist East Africa Regional, Yara