By Ruth Vaughan

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In my line of work I visit hundreds of flower farms a year; the flourishing, the ticking over, and the ones in dire straits. A lot of my hard work is dealing with farms that suddenly run into problems. “Ruth, please come and visit our farm as soon as possible, our production has suddenly dropped to half” is a common call.. 

Flower Farming

Ruth visiting a client’s flower farm

My advice to flower farmers on the critical issues in plant nutrition in floriculture would be as follows:-

Start With The Basics

Start with the basics and know what you are dealing with. A solid ‘risk’ assessment before you even buy the farm is recommended. Dig soil pits to look for soil layers, compaction zones, soil depth, underground water or solid rock. Is the soil type even across the farm? Where does the water go when it rains? Does it hail in this area? What are the day/night temperatures and what is the annual rainfall? Look at the aspect and slope of the farm, will you need special drip lines? Do a complete soil analysis, nematode count, pathology screen and irrigation water analysis. Now you know what you are dealing with and can work out the economics. It’s better to get a shock now than after your investment.

Know Your Soil

Before planting in the soil, balance the cations with the soil recommendations from the complete soil analysis and add organic matter, deep rip the soil to break up compaction zones, do not turn the luscious topsoil over and bury it.

This will hold you in good stead further on down the line, when your beginner’s luck is over. Buy a fertigation system that can handle your water volumes and your water quality. Plan a proper irrigation program based on the plant size, plant type and production. Take quarterly samples for a 1:2 soil grown flowers analysis so that you know what’s happening in the soil and can deal with it before it becomes a problem. Back this up with some leaf analysis to make sure there is no ‘hidden hunger’ in the crop limiting your production. Identify problems early before they hit your bank balance.

Media, Nematode & Pathogen Analysis

Before planting in media do a media analysis, nematode count and pathogen screen. The nice certificate of testing that comes with your coco-peat does not account for the conditions the coco-peat has traveled or been stored in. The fine pumice or gravel from your neighbour’s quarry could have toxic salts, silts and nematodes.

Do bi-annual nematode counts. You can’t see nematodes with the naked eye, and by the time your plants go yellow, you will have lost much of your production and quality. It is also easier, cheaper and more environmentally friendly to treat low nematode levels. Once levels get out of control you have to resort to the big guns, in the red and orange zones of your audit guidelines. Nematodes severely affect plant nutrition.

Know Your Water

Water testing is crucial. Borehole water tends to have a more constant quality and tests are advised twice a year. Surface water quality can vary dramatically depending on rainfall and evaporation. Rain water is best – plan to catch as much of this as possible. Water quality has a major impact on your plant production and health and the way you manage your irrigation.

Irrigation water analysis

Irrigation water quality has a major impact on your plant production and health

Water can have high sodium, you might opt for a reverse osmosis system or mix with rain water to bring this down. You have to monitor the sodium levels in the soil. Plants can tick along happily with a small amount of sodium in the soil but when it reaches a critical levels you will get a rapid decline in production and plants will become very susceptible to diseases. Work with humid acids and calcium products in conjunction with leaching to flush the sodium out. If you didn’t follow the initial guidelines you might find this a problem. Water saturated underground soil, bedrock, compaction layers and unbalanced cations will all impede the leaching.

High Bi-Carbonates In Water

Water can have high bicarbonates – these ‘lock’ up phosphorous and micronutrients in the soil, creating a free lime deposit that raises the pH. Once the free lime has built up in the soil, it is very hard to deal with. Much better to treat the problem at source and acidify the water. Acidification can result in an increase in nitrates from nitric acid or phosphates from phosphoric acid and the fertigation program has to be adjusted to balance these. Quarterly drip analysis will check the Electrical Conductivity (EC), pH, nutrient, and bicarbonate levels of your drip water and ensure that everything is going to plan. On-farm daily EC and pH measurement are advised.

14 Irrigation Water Analysis Report
Sample Irrigation Water Analysis report showing high levels of Bi-Carbonates in water


Many a farm has ‘tripped up’ due to fertigation system faults that were not picked up soon enough. High levels of carbonates (hardness), in the water may interfere with the acidification due to a buffering effect and you will find that the pH goes up after the fertigation system. If this is a hazard, then a laboratory controlled acid titration is recommended, and you may have to put a pre-acidification unit into your farm.

Irrigate Sensibly

Get a soil water meter, or go around the farm often with an auger to check soil moisture levels. Water you see on the surface is not what the roots see underground. Over and under watering affect nutrient uptake and production.

Be Aware Of Changes

Recently, Kenya has been in a major drought situation and rain water reservoirs are emptying. These are being topped up with borehole water. The reservoir water quality is changing weekly, and should be monitored through this transition period until water quality stabilizes. Borehole water may have a high pH and EC and high levels of some nutrients and toxic ions. An increase in EC means that the ‘space’ between water EC and the irrigation EC shrinks and you don’t get so many fertilizers on your crop. You will see a decline in production and leaf yellowing. A rapid increase in pH due to what I call ‘the bouncing bicarbs”, can have two negative effects:

1) Your machine cannot handle this and high levels of bicarbonates hit the soil causing phosphate and micro-nutrient lock up.

2) Your machine can handle it and you suddenly have a deluge of nitrates or phosphates going into in the crop. Both results in production collapse, soft growth and leaf drip. Some borehole water have high magnesium or potassium and if you do not adjust your feeding program, your soils will tighten up and oxygen and water infiltration will stop – again yellow leaves and leaf drop. Monitor water quality regularly and adjust your fertilizer program.

Take The Guess-Work Out Of Farming

Analyze, analyze, analyze. It will save you money in the long run. Plan the analysis that you need in advance and budget accordingly. Read and use your analysis results. Don’t file them in the drawer until the next audit. Audits are meant to guide you and there is a reason they recommend you do these analysis! If you don’t understand anything, just ask! Or get a professional consultant in.

Seek Independent Analysis And Advice

The man selling iron chelates will most probably find an iron problem in your crop. The man selling nematacides will always find a few nematodes that need treating. That’s their job.

Read And Follow Dosing Instructions

The suppliers have done extensive tests on their products before they write the labels and go to market. A little bit of something, used properly can have a brilliant result. Don’t be tempted to over-use or over apply products. I have seen some catastrophic results from product over use.

If all goes well – analyze so that you know what you are doing right and can replicate it. If all goes wrong – don’t over complicate things, go back to the basics, call in the professionals, and recover faster!

Till next time,

Happy farming!


About Ruth

Ruth vaughan cropnuts


Ruth Vaughan is the Technical Director at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). Ruth is also a contributing author to Kenya’s leading horticulture magazines such as the HortFresh JournalHortiNews and Floriculture. Ruth is a great believer in soil health, organic matter, biochar and carbon sequestration as a way to alleviate climate change and increase food security. Loves visiting farmers and seeing all the different farming methods