It as been a long while since I last reported on the progress of the farm, so it's time for a brief recaps of how last years growing season turned out.
I had bountiful harvests of squash, pickles, eggplants and occasionally tomatoes up until end of September. Then Berlin got hit by a wave of unusually wet and cold weather. The tomato plants where loaded with fruits, ready to ripen, but a funghi called Phytophthora infestans spread though the farm like a wildfire. Within 10 days or so all plants turned brown and died. I harvested all tomatoes at once, hoping they would still ripen by themselves, some did, most didn't. Phytophthora infestans developed out of a pathogen that originally only infected potatoes. A mutation which occurred sometime during the mid eighties in Mexico made the pathogen able to spread also to the closely related tomato. Since then it has become very difficult to grow most tomato varieties outdoors, at least in wet and cold weather conditions as these help the fungi to spread and thrive. Tomatoplants basically may not get wet, how pathetic !
Of course tomatoes didn't evolve to grow in a cold wet climate in the first place, humans made them able to do so. And tomatoes have become so dependend on humans that they in fact have even developed human characteristics. Domesticated organisms spread, replicate and survive through the help of humans in exchange for being eaten. In many cases they also sacrifice the ability to survive on their own. Dairy cows die within days, sometimes even hours, if they don't get milked. Corn isn't able to reproduce without the help of humans. Tomatoes need shelter. Maybe I will build them a roof this year.
How did the SIPs work out ? About every plant was thriving, but if I had to start all over again I would do things different. SIPs are a one size fits all solution. They are perfect for getting the most out of the space you have. But they are also a rather complicated, restrictive and input intensive form of farming. They are especially suited for level grounds and places where there has to be a clear seperation between soil and ground, like balconies, indoors or on contaminated grounds.
In my case I had to build a wooden platform for the SIPs to stand on, to cope with the slanting roof.
I think there is a better, more minimal way of farming in this kind of situation. Next season I will keep the already existing set up, but add an experimental area of sandbags filled with dirt and compost. These won't need a platform to stand on, since their shape is flexible. They also minimize the risk of hurting the roof because they are soft and distribute weight evenly. The slanted roof is actually a big advantage for watering: excess water can run off and be collected again in a rain barrel. My plan is to time the pump to water the plants for a specified period during night, when evaporation is minimal. If the sandbags are punctured, there is no danger of overwatering. The water is recollected in a rain barrel, so are the nutrients that will be washed out by excess water. By using only organic, non soluble fertilizer, such as compost, there will be also less nutrients washed out. If the soil drains properly there will be also less danger of fungi pathogens developing and thriving. I could also imagine that the constant cycle of wet and dry soil will let the plants grow more vigorously. One thing that really bothered me, what i think is the biggest downfall of using SIPs, is their ultraspecific soil requirements. The soil in SIPs has to support capillary action and must be rather sterile. This leaves just a few options such as peat or coir as the main ingredient of the mix. For example: people using rich compost in SIPs reported having huge problems with fungi. I believe that is because the soil in a SIP is moist at all times. It is also not possible to use straight local dirt, since it usually doesn't wick very well.
By being able to use only local dirt and compost for growing you are able to close the nutrient loop and to grow plants that over time adapt to local soil conditions. By using sand bags, you also vastly reduce the material input, the whole farm can be folded into a small pile of fabric, if necessary. And you can avoid using plastic altogether, for example by using 100% compostable jute sand bags. I'll see how it goes.
A few other brief updates:
The cabbage station didn't work out, none of the plants matured, I guess it was just too late in the season.
I will try again this year.
The chickens where killed by a fox.
The coir vs peat experiment left peat as a definite winner.
The peat vs compost experiment ended undecided, both versions produced lush and healthy eggplants.