PPM, soilless mixes, and flushing. Help me understand.

Hi,

I am growing in Sunshine #4 (sphagnum peat moss, coarse perlite, gypsum and dolomitic limestone) and using advanced nutrients, specifically B-52, voodoo and sensigrow (I am in the veg stage).

I have a chart that details the desired ppm of a nute solution for the various stages of growth. My question is, should I be measuring the run-off ppm? If I notice that run-off ppm is significantly higher than the solution I am watering with, does that mean there is salt build-up? Should I flush to correct this?

More generally, is it good practice to flush every few weeks regardless of ppm readings to prevent salt build-up? Right now my regimen is water-nute-water, and I expect that this is what I will keep throughout the grow.

If I am using mycorrhizae and other bacteria to supplement my nute regimen, will flushing destroy existing colonies?

Thanks.

Measuring the runoff won't really tell you that much unless your using RO water. Don't really worry about that, keep an eye on what your putting in. As far as advanced I use sensi bloom along with a few other things, I usually do every other watering until mid flowering and then it's every watering. I use promix also. Flushing will not effect them because they are actually living on your roots. If what I wrote sounds fucked up my applogies cause I just smoked a fattie of some ww and I am now fried.

You should measure your soil runoff (look for Pour Through Method at NC STate Extension link at bottom of this post ) to get a reasonable read on the nutrient profile within the soil solution. Generally, you don't measure the ppm's, you measure EC and pH of your sample. The EC is directly related to soluble salt concentration and EC levels are the indication used to determine when flushing is necessary.

Your nutritional application and water schemes should be looked at first. If you don't provide nutrients with each watering, your nutrients are applied at higher ppm levels than your plants need, but the ppms are reduced by the non-nutrient waterings. If you provide nutrients with each watering, you reduce the ppm levels to the average ppm level you would see with the nute/water/nute/water approach. So you will apply less nutrients per application, but the nutrient levels are kept close to constant with this approach and there is more control over the plants nutrition. When using this latter approach, you may also use about 10% more water in your nutrient solution to effect a little flushing with each nutrient application.

Flushing with water should not affect mycorrhizea.. flushing with a proprietary flushing agent may be a different story .. read your labels and warnings.

NC State Extension pour through method => http://extension.umass.edu/floriculture/fact-sheets/how-use-ph-and-ec-pens-monitor-greenhouse-crop-nutrition

Otoke Horticulture
www. otokehort.com

Thanks. Right now I apply AN at 1/2 strength every other watering as my plants are relatively young. Works out to me applying nutes every 7 days or so.

I will take your advice and begin applying at 1/4 strength every watering, allowing for a decent amount of run-off.

I have an EC meter so I can measure this variable.

Also, I do use RO water, with CalMag Plus (Botanicare) as a supplement.

Thanks!