Questions Background EC

@skbud welcome to Percy’s mate. I’m also a coco grower using rainwater and might be able to answer this. When you look at EC related to nutrients, you don’t count the first 300 micro Siemens/sq meter related to your background if you are using municipal water or well water. If your tap water has a background of 250 you subtract that from your final value to get your actual nutrient load (600-250= 350 for example). Similarly, if the background is 400, you dismiss 300 of that value and use 100 in your nutrient calculations. In this case when you measure the EC of 600 the EC used in your calculations/diary would be 300 (600-300=300). In general you only subtract 300 max for background EC and absorb the rest of the value. This is a reason plants fed with rainwater grow faster, lower background so you can add more of what they like. I’m not sure what your tap water EC is, but subtract that value from that 600 number you are considering and aim at that for a starting EC.

Ok thank you for your help 

+1 for what @monkeydo said, I use rain water and in coco and the plants thrive and tend to grow faster and healthier, one tip though is that you need to add more calmag than you would otherwise need as rain water lacks calmag compared to tap water. in full flower with pk boosters I can see up to 2ml per litre in the calmag department to keep the ship steady.

Good catch @bubblehok

They look a little pale

@skbud Yes they do mate.... you watering these every day yes? making sure the pH is 5.8?

@skbud what’s the nutrient mix that you are feeding these. Remember that there’s no calcium in your rainwater so cal/mag is a must

Yes, my ph in is 5.8 runoff is 6.0.  My EC in is .450 runoff is .380 adding 1ml per gal of calmag and I buffered my coco prior.  Thinking I may be too low on nutes