Small farmers approach to Fertilizing in greenhouse tomatoes Kenya.

Fertigation is combining the application of water and fertilizers through the irrigation drip system.A good fertility program ensures that all the 14 elements needed by plants are supplied. However there is a challenge in doing that; the cost involved since the various fertilizers required are rare and at times due to the different constitutions of fertilizers it is very difficult for farmers to know the appropriate amount and type of fertilizer to apply.

The suitable approach is to examine the locally available fertilizers to determine if a balanced nutrition is possible. After a lot of consideration, I identified the following fertilizers that have closely and after using them they met my expectations.The recommendation of scientists all over the world is that by the end of a growing season, 1 hectare of tomatoes will have utilized an average of ; 450kg of Nitrogen, 65kg of phosphorus and 710kg of potassium. These three elements are major elements since they required in huge amounts compared to other elements. This creates a special challenge for farmers especially in sub-Saharan Africa who lack technical skills how to mix fertilizers and who do not take the soil for testing.  

I have developed this simple strategy that solves this problem. It involves supplying greenhouse grade NPK fertilizer through fertigation combining it with foliar sprays and soil application of a specialty fertilizer known as Dolmax. This strategy utilizes locally available fertilizer mixes to achieve the above result while taking care of the required essential micro-elements. 

Why fertigation?

It is possible to apply the nutrients exactly and uniformly only to the wetted root volume, where the active roots are concentrated, therefore increasing the efficiency in the application of the fertilizer reducing fertilizer usage. This fertilizing method prevents under-fertilizing or over-fertilizing since it is adapted specifically to the crop throughout the growing season.  The other advantage is reduction of groundwater pollution caused by fertilizer leaching and finally actual nutritional requirement is easily met.

It is paramount to know the most favorable the daily nutrient consumption rate that results to maximum yield and production quality at the same time saving as money.

Dolmax fertilizer

This fertilizer has 9 elements out of the 14 required by tomatoes. So we need to get other fertilizers that provide most of the remaining elements because if we were to purchase single element fertilizers the total cost will be too high. If you carefully examine the above fertilizer, you will notice the major elements required by plants i.e. N, P, and K constitute a very small percentage of the total constitution of the fertilizer. We therefore need the following additional fertilizers.

 

Mixing the fertilizers

I have tried this combination of fertilizers giving me excellent results the figures for fertilizer requirement given here represent the amount of mix required for 1m2. Therefore to find the exact requirement for you greenhouse, multiply by the floor area covered by your greenhouse.

 

Requirements

NPK [19:19:19] – Buy a greenhouse grade NPK fertilizer that is highly soluble. I recommend that you buy from Osho industries Nairobi. Sold in from of 15 Kg bag, and the fertilizer is pink in color.

Agro-feed [12:10:8+ TE] 

This fertilizer is manufactured by Osho industries. It is sold in 5 litre container packs. The advantage of using this fertilizer is that it supplies elements like boron, cobalt, molybdenum and copper those are not supplied by Dolmax or NPK.

Method of applying the fertilizer Step1. Amount of N.P.K required by 1m2 is 0.24Kg. To get the amount your greenhouse will require multiply the floor area of your greenhouse by 0.24
For example Mr. Koech's greenhouse has the following floor area measurements length 30 meters, width 20 meters. Find the amount of NPK fertilizer required.

Solution area= L x W

               =30X20

               =600m2

Therefore to get fertilizer required will be 

                   600x0.24= 144 kg 

This is the amount of fertilizer required for the full season of 120 days. To get the daily fertilizer requirement we divide 144kg with 120 days to give us 1.2 Kg/day. This is what you will put in the irrigation tank every day for fertigation for 120 days. The solution is pumped by a moneymaker pump to the drip lines that supply every plant.

Step2. Apply two tablespoon of Dolmax fertilizer to every plant. The purpose of this fertilizer is to supply calcium, magnesium and micro elements to the plants. This should be repeated after every one month and should be stopped when the fruits have attained a diameter of 3 cm.

Step3. Apply Agro-feed [12:10:8+ TE] after every 2 weeks after the crop attains the age of 2 months. Put 40-50ml in a knapsack sprayer and add 20 litres of water and 10 ml of a wetting agent spray the leaves. 

Once the crop has started fruiting and fruits have attained a diameter of 3-5 cm discontinue all fertilizer application.