Mulching Thornless Blackberries
The recent "mulch" post regarding fruit trees was quite interesting to read and got me thinking again about mulching my three new 300-foot rows of Natchez blackberry plants I planted last winter. To prepare the soil, I tilled the new rows periodically (down to maybe 7-8 inches) that previous spring and summer to initially minimize the weed growth and add organic matter to the soil to give the plants a fighting chance to survive the following spring. Then in November I got some organic compost and spread about an inch or two on top of my 5-foot wide 300-foot rows, then tilled that in and planted my 900 bare root Natchez plants 3 foot apart in December. In March, I walked down each row and threw a handful of 13-13-13 ammonium nitrate-based fertilizer (with micro-nutrients) around each plant and watered them every other day with drip irrigation. Then, periodically throughout this past year, I would use my weed-eater to knock the grass and weeds when they would start to get out of hand.
I have avoided using wood mulch as a weed/trash-grass deterrent when planting my berry plants because I've always heard fresh wood mulch will use the nitrogen to speed up the decomposing process instead of letting it pass through to the soil where it is needed.
If I were to put 4-6 inches of mulch around each my now one-year old Natchez berry plants, my questions are these:
1. Will the mulch use up all the nitrogen before it actually gets to the roots (about 2-3 inches below the soil)?
2. If so, any idea how old the mulch has to be before it will allow the nitrogen to pass through to the soil with the other nutrients? In other words, do I need to let the mulch sit idle for a year or two in a big pile before I lay it on top of the beds?
3. If the mulch only uses a partial amount of the nitrogen, should I just double the amount of N? In other words, after I throw the handful of 13-13-13 (with micros) on top of the mulch around each plant, should I then follow up with a handful of (urea-based) 33-0-0 to make sure my plants get some nitrogen too?
I've thought about using a fertigation approach laying my irrigation lines under the mulch, but it would be too costly at this point for me, based on my existing setup, to implement that strategy. But I am getting tired of weed-eating my 7200 row-feet (in total) of thornless blackberries and thought I might try using mulch on my 3 new rows of plants to see how well it does to minimize the weeds.
Any thoughts would be greatly appreciated?