Hi James,

A complete soil test is always a good place to start for determining, or at least ruling out, problems. What product have you been using to lower the soil pH? Soils in Colorado are typically alkaline and tend to have a lot of free lime in them which makes it very hard, and sometimes not feasible, to lower the pH. The free lime has a very high ability to buffer any attempts to lower the pH. CSU's Soil Lab in Ft. Collins is closed for the season but there are some other labs that I would recommend.  They all have instructions on their website or on the submittal form about how to take a soil sample. After you receive your soil test results, feel free to forward them to me at <personal data hidden> and I can take a look at them and give you more specific recommendations.

ServiTech

https://servitech.com/laboratories/soil-testing
Lawn & Garden Soil Test Form

• I recommend the Lawn & Garden Soil Analysis or the Complete Soil Test (they test the same things)
• The form above is for their Lawn & Garden test which includes the same information as CSU's Routine test except that it does not give you a soil texture estimate (amount of sand/silt/clay). If you would like to add that you will use this form , check box 7 for lawn & garden, and in the 'Other Tests Please List' box write Particle Size Analysis. I am not sure about the pricing for their samples though, I have not been able to find that information on their website.

MidWest Labs

https://midwestlabs.com/get-started/our-industries/agriculture
Lawn & Garden Soil Testing Guide
Soil Testing Overview
Soil Sample Submittal Form

• I recommend test S3C or the Garden Soil Testing Package

Ward Labs

https://www.wardlab.com/submit-a-sample/soil-health-analysis/traditional-sampling-procedure/
Soil Sample Submittal Form - With Fertilizer Recommendations
Soil Sample Submittal Form - Without Fertilizer Recommendations

• I recommend the Complete test (code S-5 on the submittal form)

Please let me know if you have any questions!

Best, 

Denyse

Hi Sandy,

Yes the thing I would be most concerned about is the salt content in the upper garden. The could definitely cause the decreasing size of tomatoes you've been seeing. The sodium levels are not bad so the salts are most likely calcium and sulfur salts (e.g. calcium sulfate/gypsum, magnesium sulfate/epsom salts). Since you said the soil drains well and the soil is not alkaline, you should be able to leach the salts out. I would add 8-10 inches to the upper garden over the course of a day or so (amount of time it will take depends how quickly it drains). For the next 2 years I would not add any fertilizer except a nitrogen and potassium/potash supplementation at the rate that is listed in the soil test. I would use a fast release nitrogen and apply it early summer or break it into 2 applications, one late spring and one mid summer. After 2 years of this I would get another soil test to see where you're at. I also would try to avoid any deep digging since you don't want to accidentally bring the salts back up to the soil surface. This should help get everything rebalanced. You also might want to grow more salt tolerant crops (beets, kale, spinach, squashes, broccoli, cauliflower, cabbage) in that bed next year to be on the safe side, or avoid the more salt sensitive crops like peppers, radish, green beans, onions, carrots.

The salt content in the lower garden isn't an issue but I would avoid any soil amendments high in sulfur or calcium for the next few years. I would also fertilize this bed with just a nitrogen and potassium supplementation at the rate listed on the soil test. You could add about an inch of plant based compost if you would like but it is not necessary for next year (the point of this is just for organic matter - you don't need a nutrient rich compost/amendment). Make sure to avoid manure based composts as they tend to be high in salts. 

Please let me know if you have any questions! Feel free to contact me directly at <personal data hidden> or <personal data hidden> if you'd prefer.

Best,

Denyse