What you are dealing with is clorosis... The plant's roots are not getting enough oxygen and therefore cannot metabolize nitrogen and iron, become deficient, and turn yellow and don't thrive. Usually caused by too much rain or watering, and the resulting soil compaction. It is especially common in heavy clay soils without a lot of organic matter. In your case, the heavy cardboard takes time to break down, so it is creating a barrier that is preventing adequate evaporation, and also blocking air flow into the soil. The best treatment is, unfortunately a lot of work- aerate the soil by forking it up around the plants and making air pockets to get to the roots, without damaging them. Adding some organic matter and sand to improve drainage is good. Also, trying to slope the beds so they drain better can be helpful for the coming season. If you have a slight slope to your garden area, place the rows to run with the slope so they can drain. If you go perpendicular to the slope, the moisture will be trapped and stay. This is a good thing in arid climates or where water is limited, but in moist climates it is a liability. It is dramatic how quicky plants will perk back up and get healthy green again when this issue is resolved. It's a fair ammount of work, but so worth it! Another thing is allowing weeds with deep taproots to grow among the plants (within reason, not too many). They will suck up the excess moisture, and also draw up nutrients from deep in the soil to help the crop plants to thrive. It is synnergy!... weeds are not always "the enemy". The funny thing bout Permaculture... I'm learning that nature is the way it is for a reason! All my conventional gardening wisdom has been turned on it's head.
Amanda Montgomery wrote:I'm having some issues with slugs as well but really my big problem (other than voles) are ANTS. My goodness, so many ants. I've sheet mulched other areas of my yard on a smaller scale and not noticed an issue but now it's a real problem.
Something else I've been trying to figure out but haven't seen is an issue of soil compaction. I started with cardboard, then a layer of straw, leaves, then compost. My plants have been yellowing and have stopped growing. I aerated and the compost layer was solid. There are lots of worms and once you dig a little deeper things look pretty nice. We've had a ton of rain here in Central VA so I'm sure that has something to do with it but it's really frustrating!