What happened at SoilFixer HQ over the long hot summer?
After relocating, we temporarily lost our test beds. However, we can report on a few things we grew at our new house.
We brought with us two 50-litre outdoor container planters. They used to sit by the front door and held lovely sweat peas. We planted up (using the three-year old SF60/Compost mix topped up with around 10% new SF60. Yes, the bulk of container mix is now three years old! The results were poor; each tub had stunted peas with few flowers. They were like everyone else’s in the area.
Normally, the compost/SF60 mix in the planters gives the sweat peas a huge boost as it retains water better than compost-only mix. Looking back, it’s evident we had a triple whammy. The seedlings were planted out too early when it was still a bit cold. They then got a hammering from the wind. It took a week or so to spot the new door location is actually very windy! Having got a poor start, the excessive heat was the final blow.
We will be using the reusing the SF60/compost mix in the planters next year. I’ll probably plant up boxes in the windy door spot and grow sweat peas out the back against the sunny but sheltered wall.
We also planted some green beans against a very sunny wall. Lovely! What a difference in taste fresh home-grown beans make. In August, the beans started to show signs of leaf chlorosis; this is yellowing between the veins.
Having looked at various gardening advice sites, the list of possible causes for leaf chlorosis include iron, zinc and manganese deficiency, which all tend to be associated with high soil alkalinity. Too little water and too little nitrogen.
My soil pH looks fine at pH 7.5. I treated the leaves with a both Iron and zinc foliar nutrient sprays to no avail. I concluded that the real problem was excessive drying out of the soil; this limits all nutrients, including nitrogen. Having added liquid fertiliser and recent rain they’ve perked up.
I was disappointed because I’d added biochar around the beans. The first beans we picked were from plants that I’d planted with some biochar, so it was a bit of surprise to see all the beans had leaf chlorosis later in the year!
As sometimes happens, looking back, I started off okay then got side-tracked. I dug out the grass and weeds from the section bordering wall, a nice and sunny position. I had about six runner bean plants and thought it might be interesting to pop some biochar into three holes and compare to those planted in clay. This bit was okay, then a week later when I was moving various half bags of compost and biochar around in garage I thought I’d put these on the clay soil I’d just dug over. I added a five-centimetre layer of the compost/biochar mix on top of the soil and around the beans.
Regular readers will know we don’t recommend using biochar/SF60 as a top dressing. Rather, we suggest digging biochar and SF60 into the soil, getting into down near the root zone to maximise the benefits.
What happened? The compost/biochar layer was in direct sun, it dried out and became very friable and loose. This confirms it’s not a good mulching layer. The beans gained no advantage from a top dressing. The beans will be dug out soon and making their way to the compost bin. I’ll fork in the biochar/compost into the clayey soil ready for next year.