First of all, potato cultivation has very strict soil requirements, and only soil with deep soil layer, loose structure, good drainage and aeration, and rich in organic matter is the most suitable environment for potato growth.

And that's not all, the growth and development of potatoes requires more than ten kinds of nutrients, and the demand for fertilizers is quite large.

If a plot continues to grow potatoes, because of the absorption of soil fertility by potatoes, soil fertility will be greatly reduced, and the yield of continuous cropping plots will be reduced in the second year, and the quality of tubers will also be reduced, especially diseases, insects, and weeds will occur more seriously.

Even the protagonist of "The Martian", when planting potatoes on Mars, reuses the vacuum-dried excrement saved by the astronauts before fermenting it into manure before planting potatoes.

What's more critical is that the stems and leaves of the potato plant are poisonous, and even the potatoes themselves are poisonous.

Potatoes mainly contain solanine and chitomycoline, which are generally decomposed when heated to 170°C.

Although the toxicity of artificially cultivated potatoes is not high, the amount of poison accumulated in the body will still produce toxic reactions when the consumption exceeds 1.4 kg.

As for the solanine produced after the potato sprouts, it is a toxin that will be seriously poisoned if ingested 0.2~0.4g.

Especially for pregnant women, if potatoes are consumed for a long time, the alkaloids contained in them are likely to accumulate in the body and cause fetal malformations.

Before the disaster, of course, everyone can eat potatoes and plant potatoes at will, after all, potatoes are indeed large and full, and as long as you pay attention to rotation and fertilization when planting, you can avoid many problems in planting.

However, the toxins in potatoes are an unavoidable problem, after all, the end times are not like before the disaster, people can choose a variety of foods, can eat many different foods, and the abundant supply of materials can also allow people to always eat fresh potatoes, greatly reducing the risk of poisoning.

But there are no such conditions in the last days, and the underground land resources are limited, and if you grow a staple food, there will basically be only one.

And this will cause people to eat potatoes for a long time.

Coupled with the fact that the shelter must not be planted and eaten, it is predictable that the harvested potatoes will mildew and sprout during storage.

Before the disaster, this must be thrown away, and no one will eat the sprouted potatoes.

But in the last days, this is an important food reserve, rats, cockroaches, earthworms are all taken to eat, a few spoiled potatoes? As long as you can't eat the dead, you can eat it when it's cooked!

So at this time, the toxins in potatoes are a problem that cannot be ignored.

At the national level, potatoes are obviously not the best choice if you need to choose a doomsday staple at this time, especially when you need a lot of light to grow potatoes.

It was also because of these factors that Chen Xin chose upland rice as the main source of food for his refuge.

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After sending Qin Lan and Ding Ning away, Chen Xin cleaned up the place and sat down in front of the workbench.

While taking out the pistol he had just exchanged from Qin Lan and putting it on the workbench and pressing the bullets into the magazine, he was also thinking about making an oxygen concentrator for Mo Qingyan.

Although when he got an oxygen concentrator for himself, he chose a very simple and crude production method, and later relied on system upgrades to obtain the oxygen concentrator, but this method was still too extensive.

And the kind of overly simple oxygen concentrator he made before is really not worth mentioning in terms of efficiency, and the utilization efficiency of light energy is still very low.

However, after upgrading the system, even Chen Xin's simple and crude oxygen concentrator is now decent.

Chen Xin chose the second solution to upgrade, the original square plastic box has been turned into a straight hollow tube, and the fill light is directly installed in the hollow part of the tube, which is directly irradiated from the inside to achieve the maximum efficiency of light energy utilization.

The algae, on the other hand, are raised directly in the round tubes to thrive, producing oxygen that is expelled from the top, while carbon dioxide is injected with stomata at the bottom.

The settled algae carcasses are filtered back from biomass during the water cycle, which is used to produce methane for fuel cell power generation.

The entire system has been upgraded to a two-meter-tall green cylinder with light coming through it, and the entire column is filled with algae.

The oxygen produced by such a device can sustain the survival needs of a normal person, and the electricity generated can maintain the energy consumption of the whole set of equipment except for the fill light, and there is a slight surplus.

After all, under normal circumstances, algae-to-oxygen power generation technology relies on sunlight to promote photosynthesis of algae, and now that there is no sunlight, this part of the energy consumption of the fill light must be supplemented by other energy sources.

Mo Qingyan's shelter has electricity and water supply in the city, and although it is supplied for a limited time, it is not a problem to maintain the operation of the equipment.

Pressing both bullets into the two magazines, Chen Xin inserted one of the magazines back into the pistol.

Holding the gun and feeling it, he couldn't help but take out the pistol he had made and put the two guns on the workbench for comparison.

Compared with the pistol made by Chen Xin himself, the caliber of the pistol Qin Lan gave him is obviously larger, but it is lighter in weight, which is due to the fact that Yan Guo used engineering plastics as the handle when manufacturing the QSZ92G semi-automatic pistol, which reduced a lot of weight.

As for other performance differences, Chen Xin can't compare the quality of the two guns without actually shooting out dozens of bullets, which requires his professional knowledge and experience in using firearms.

After a little consideration, Chen Xin decided to use the pistol he had obtained from Qin Lan as a weapon for self-defense, while the pistol he made himself was put on the bedside table in his bedroom as a backup.

It's also a safe strategy, and having weapons and equipment at the place closest to you is a great way to improve your ability to deal with danger.

Although in Chen Xin's opinion, as long as the gate is closed in his shelter and there is no heavy firepower, it is difficult for him to cause any security problems that need to be dealt with guns.

However, it is important to be prepared, and in case something goes wrong, it is still important to have a gun in hand.

After doing this, Chen Xin took his bow out of the weapon cabinet again.

Archery was just a hobby that Mo Qingyan had cultivated in the past, and it had no practical use.

And in the last days, the role of the bow and arrow is greatly reduced after the gun, and the existence of this bow has become a chicken rib in a sense.

What's more, as the outside temperature drops, if you take it out and use it, the maintenance of the bow and arrow itself will also become a problem.

So Chen Xin plans to see if this bow can be used for other purposes after upgrading, if he can, he plans to upgrade the bow into a crossbow, and then install it at the upgraded gate to be used as a defensive facility.

Maybe you can't backstab a bed crossbow, but you don't say you can't use a bed crossbow as a trap.