Different approaches to fertilizing can be used to produce a high quality crop of any species. Often despite major differences in fertilizer programs between two growers excellent results are achieved when the two crops finish. In this piece basic fertilizer programs are recommended for the most important crops currently grown in East African greenhouses. An individual grower may need to "fine-tune" these recommendations to fit his/her conditions.
"I have been growing tomatoes in the Isinya, in the open field but now started green house production. Advise me on the Best Fertilizers For The Green House Production please"
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.
However, remember too that the determinate tomato varieties produced in the open field will generally require less amounts of inputs as they mature within 3-4 months, while for the indeterminate varieties under Green house systems means a crop on the ground for more than 8 months, hence higher amounts of inputs including fertilizers are needed.
Like many other crops, a tomato crop requires Phosphatic fertilizers with at least 30 % 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.
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. Therefore periodic application of NPK fertilizers during the growing season is important to ensure good productivity of high quality fruits.
Fruit size, colour, texture and firmness are important attributes for a high yielding high quality tomato production. NPK fertilizers - 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 applied 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 fertilizers are important to improve flowering and fruit setting.
Nitrogen supplied both through Calcium Nitrate as well as the NPK fertilizers 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.
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.
By: Vitalis Wafula
East Africa Regional Agronomist - YARA