Adjust the pH, the elements and the EC to avoid growth inhibition!
Do you adjust the elements in your well water and do you have a pH regulating system? With a good pH you will get a greener crop and 10-20% more growth.
Q. Which elements are useful in well/surface water?
A. These are; calcium, magnesium, sulphate and the micro elements. These elements are deducted from the feeding solution. For this reason some growers do not have to add calcium nitrate because the well water contains so much calcium.
Q Which salts are NOT useful?
A. These are sodium, chlorine and high amounts of sulphate. Above 1.5-3.0 mmol/l (40-100 ppm) growth inhibition can occur. Iron, manganese and boron can be high. Check if the amount is below the normal feeding solution concentration. High boron can cause leaf edges.
Q. Does well/surface water change?
A. Surface water is in summer often more salty because of low rainfall. Well water is more stable but can change in time in case the water comes from another layer. Check every 3-6 months with a handhold EC meter the EC if the value is still the same. You can also send a sample to the lab.
Q. Discuss pH lowering, acidifying of the water
A. The pH and bicarbonate are not comparable. A high pH without buffer, for instance in rainwater, is easily neutralised. Water with a high pH with a high concentration of bicarbonate, like in well water from calceolarias soils, needs more acid for neutralisation. So it is NOT possible to say how much acid is needed based on only the pH value of the water!!
Q. Discuss acidifying with combined fertilisers
A. You can buy fertilisers for “hard” water, water with a lot of calcium bicarbonate. The acidifying effect is based on two principles; direct or through ammonium. The direct acidifying depends on the fertiliser and ranges between 0.5 to 2 mmol bicarbonate at 1 g/l. Check how much bicarbonate has to be neutralised. Ammonium is in the substrate reduced to nitrate and then the acidifying effect starts. This cannot be controlled completely. Also a lot of nitrate is given which can cause excessive growth. High ammonium works antagonistic for the uptake of calcium. Ask your fertiliser supplier how high the acidifying effect is of the different fertilisers and let them calculate how much acidifying is necessary and possible.
Q. What do we see in practice?
A. A high pH in the substrate/soil Plants which appreciate a low pH like Erica and Camellia start with a low pH in the potting soil but the watering is done with a high bicarbonate amount. The consequence is that the pH rises in the pot and the plants do not grow optima. This shows as a light green crop and sometimes even brown necrosis. Fast growing crop which take up a lot of nitrate so pH rises and also get water with high amounts of bicarbonate often also become light green.
The uptake of iron and phosphate is difficult. In both cases the start is good with normal growth but the more water is given the pH increases. In case of a dry summer with continuous watering the problem shows earlier compared to years with more natural rainfall. To salty in dry periods a lot of surface water is used and the EC of the surface water is often higher. The top layer of the substrate dries out fast so an accumulation of salts occur. This excess of salts causes yellowing of the leaves which can lead till brown necrotic spots.
Q. What is your advice
A. An automatic pH regulation with acid is the best system to be sure to apply the right pH. If this is not possible choose acidifying fertilisers. In case of questions please ask your nutritionist.