The raspberry and blueberry season has come to an end. We bid farewell to months of sweetness and health and sadly say goodbye to the tiny and sweet fruits – until next year….
The end of summer is here, with slightly cooler mornings and breezier evenings. That is, they were like that until this heat wave descended upon us….
End of summer heatwaves take me back thousands of years, reminding me that crazy weather and global warming are not the sole cause of heatwaves. Thousands of years ago, the Talmud discusses a shockingly hot end-of-summer: “The heat of the end of summer is more oppressive than the heat of the summer itself.” (Yoma 29a)
But other than wearily griping about the heat, we at Chubeza try to harness the scorching sun’s power for soil solarization.
Why should we disinfect the farmland to begin with? For the same reason we wash our hands with water and soap – to prevent the transfer of and infection from viruses, fungus and germs. Pathogens exist in the ground as well, and they stress and harm the plants. One of the most infamous is the fungus that caused the Irish potato blight of 1845, devastating the crops and bringing on the greatest famine in Ireland’s history. Some one million people died of hunger, and a similar quantity emigrated to the U.S. Here at Chubeza, we meet soil-borne diseases every year. Fortunately, they are not on a large scale, and of course, they do not cause disasters of Irish potato-famine proportions. Sometimes the problem is manifested by non-uniform growth in the bed – some parts of the bed have hearty plants, while in other sections the growth is sparse. In such cases, we attempt to regain soil balance and renew the helpful organisms within by disinfecting the soil.
Soil solarization means taking a preemptive step. The idea is to cleanse the earth of pathogens before seeding, in order to prevent attacks on the plant. There are several methods to sanitize the earth. The first, developed at the end of the 19th century by German researchers, is to heat up the earth and disinfect it using steam. Subsequently, a chemical method was developed in which the earth is cleansed by volatile chemicals, particularly the strong, familiar (and extremely toxic) methyl bromide. Chemical fumigation was very popular and common in large agricultural settings, where it seemed essential and irreplaceable.
But chemical soil fumigation is also very problematic, to say the least. The immediate problem is clear: these chemicals are extremely toxic to humans, animals, insects and earth. Methyl bromide also injures the ozone layer and is therefore forbidden. But chemical fumigation has other disadvantages as well: unfortunately, the disinfectants are not so picky about who and what they disinfect. They frequently harm the beneficial natural enemies together with the pathogens, thus destroying the earth’s positive micro bacterial texture and violating the soil’s biological balance. The result is an ecological blight to the earth and the environment. Upsetting the balance can be a double-edged sword: the moment the “good soldiers” are destroyed, the earth and plants no longer have any protection against diseases or pests which swoop in after the disinfection.
In 1976, an alternative method was developed by Professor Ya’akov Katan and his colleagues: disinfection by heating the earth via solar rays. The idea is that the ground will reach a sufficiently high temperature to kill disease-causing organisms and cleanse the earth of future ills. Weed seeds are also destroyed by the heat, which is why this method can be used successfully to rid an area loaded with weed seeds, and start off “on the right foot” with fewer weeds-in-the-making.
Soil solarization is gentler towards the biological processes conducted within the soil. Research has shown that the temperatures reached by the earth (40-45 degrees Celsius) do not destroy all the pathogens and certainly do not kill the earth’s biological activity. Another development of the method, where compost is dug into the earth prior to the solarization, contributes to the increase of the microbial activity.
How is soil solarization conducted?
- Wait for the right season, i.e., summertime (July and August). Prepare the earth as you would prepare it for seeding and planting: clean remnants of previous plants, loosen the earth and add compost; form beds.
- Water the ground, usually with sprinklers. The moisture conducts the heat deeper and encourages biological activity. The earth should be saturated to a depth of 70 centimeters.
- After the earth is sufficiently wet, cover it with a clear plastic sheet to heat it up. This should be done very early in the morning, when there is no breeze and it is not too hot, and we are as patient and precise as possible. The sheet is pulled and stretched across the earth, then sealed by dirt along the sides to create a vacuum.
- Then wait. It is recommended to keep the sheet cover over the earth for four to six weeks.
- We use soil solarization to disinfect the growth houses, beginning by recycling the plastic that had covered the tunnels. It’s no longer entirely transparent since it’s second-hand, yet we prefer to recycle, even at the cost of a slightly-lower temperature for disinfecting. We removed the roof from several of the structures, thus the full power of the sunrays floods the soil with warmth. Others are still covered in plastic, with less radiation, but much, much hotter….
Here are some photos.
During this time, the earth heats up slightly more than the outside temperature, and strong gases accumulate within the vacuum under the cover. These materials are naturally secreted from the compost mixed into the soil, but thanks to the cover they do not evaporate. Instead, they convene in the earth at higher levels than usual, leading to an extermination of pathogens. The result is a weakening of the pathogens, and an induction of “soil resistance”- basically bolstering the earth’s immune system. Unlike other disinfections, no “biological void” is created with soil solarization, nor is the biological balance violated within earth. Of course, there is shock and a change from the previous condition. Instead, a different microbial deployment occurs in the earth, one that is still rather balanced.
At the end of the process, we remove the plastic sheets, give the earth a bit of time to recuperate, and let its positive microorganisms return to operation. Then it’s time to begin autumn seeding and planting. (Yes! There is an autumn on the horizon.) We shall report our progress in the near future.
At the end of the soil solarization process, we remove the plastic sheets, allowing the soil to recuperate and the positive microorganisms within it to resume their blessed activity once we soon begin our autumn seeding and planting. (Yes! Autumn is on the horizon!)
May we all have a breezy-sunny week. Good luck to all the students who are beginning the school year this week. (Amen!)
Alon, Bat Ami, Dror and the Chubeza team
WHAT’S IN THIS WEEK’S BOXES?
Monday: Red bell peppers/long red bell peppers, onions, parsley/coriander, corn, okra/Thai lubia/cherry tomatoes, eggplant/potatoes, slice of pumpkin, green soy (edamame), tomatoes, cucumbers, lettuce. FREE GIFT: New Zealand spinach/basil.
Large box, in addition: Butternut squash/spaghetti squash, sweet potatoes/zucchini, garlic, chili peppers.
FRUIT BOXES: Apples, mangos, grapes, peaches/plums. Large box, in addition: Larger quantities of all the above + pears.