Mulch For Weed Control, Moisture Retention And Thermoregulation

2024 Author: Sebastian Paterson | [email protected]. Last modified: 2023-12-16 13:47

About mulch without secrets. Part 2

Read the previous part of the article: Using mulch for plant nutrition

A mixture of different mulching materials - can be very effective as a plant nutrition source. The more diverse the composition of such a mixture, the more fully the composition of trace elements and other useful substances is presented in organic residues.

A good effect is achieved if dry plant residues are mixed with green parts of plants. In such a mixture, rotting will not occur, and it will decompose quickly enough. There are no places on my site where only one type of mulch is used: I always use "mixes".

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But they are not specially prepared, they are not mixed - they are simply layered on top of various non-crushed materials. All of the above assumes that favorable conditions have been created for microbiological activity in the mulch. These conditions are: favorable temperature and optimum humidity.

Here we will focus on the classic use of mulch without taking into account the above.

Mulch as weed protection

Weeds do not develop under mulch because the mulch cuts off sunlight. In this regard, the main requirement for mulch is its opacity, density. The denser the mulch is laid, the more efficiently it protects against weeds. In this regard, the undisputed leader is the foliage of trees and shrubs. Wet and caking, the foliage creates a very dense layer, completely impenetrable for the sun, and therefore leaves no chance for annual weeds. To control weeds, 3-4 centimeters of packed foliage is enough.

Hay falls tightly on the soil, but its layer should be slightly thicker than the leaves. More straw is needed. It is not advisable to use needles of coniferous trees. They create a loose layer, and weeds will easily germinate through such mulch. There is information that a layer of needles of at least 30 cm is needed to protect against weeds.

In my experience, the ten centimeter layer of needles did not serve as protection against weeds. Compost and humus are poorly protected from weeds, and more often they carry a large number of weeds. Newspapers and cardboard are effective for weed control. They need to be laid so that there are no gaps between the sheets, and pressed so that they are not blown away by the wind. You can press down with straw, hay, and other organic matter.

Sometimes it is recommended to thoroughly weed out before mulching. I never do that. I just trample annual weeds and cover them with mulch. If the weeds are very large, it makes sense to mow the greens, and only then cover with mulch. In some cases, powerful perennial weeds are worth weeding out. But weeding will not get rid of all the weeds, some will germinate again. For example, bindweed and sow thistle pierce the asphalt; none of the organic mulching materials will hold them back. Other perennial weeds should be removed in advance.

Some gardeners believe that straw is preferable to hay because the hay retains weed seeds. From my own experience I know that there can be no less weed seeds in straw than in hay. In my practice, I am not looking for a weed-free mulching material.

Non-fermented organic matter effectively suppresses the germination of weed seeds. If any weed breaks through, then it is very easy to remove it - the roots under the mulch are superficial, they are pulled out without effort. On the other hand, when mulching paths, I try to use seeded weeds. Weeds growing in the aisles in early summer are a free source of organic matter. You just need to pull out or mow them in time. I have already written about this in detail.

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Mulch as a thermostat

Soil's ability to absorb and retain sunlight is highly dependent on its color. By changing the color of the soil surface, we can regulate its thermal properties. Dark mulch on the soil surface quickly absorbs heat, partly warming up the soil.

Light mulch, on the other hand, increases the ability of the soil surface to reflect the sun's rays, which prevents the soil from overheating under the mulch cover. This must be taken into account when choosing a mulch for each specific case. In addition, the thickness and composition of the mulch must be considered.

Mulching materials protect the soil and plant roots from sudden temperature fluctuations: they do not allow it to excessively heat up in the sun or cool down sharply at night, during frosts and cold weather; they keep it slightly colder in hot summers and warmer winters.

But it is precisely this property of mulch that does not allow the soil to reduce the effect of frosts on the aboveground plant organs. Open soil heats up during the day. At night, heat from the ground heats up the surface air, reducing the effects of freezing. A loose mulching substrate is a poor heat conductor, therefore it prevents the soil from heating up during the day, and at night it insulates the heat accumulated in the ground.

Therefore, frost-sensitive plants should not be mulched in a thick layer in early spring and autumn. The thicker the coating layer, the lower its thermal conductivity, the more such areas are subject to the danger of night frosts. A thick layer of mulch will keep the soil from warming up quickly in spring. For the fastest possible heating of the soil, it is better to bare it. But this leads to a rapid loss of moisture. For arid regions, this option is highly undesirable.

Therefore, in the spring it makes sense to use a thin layer of mulch, dark mulching materials, but not remove it completely. This is how the issue of warming up and maintaining moisture is solved at the same time. Warming up the mulched soil can be accelerated in other ways, but this is a topic for another conversation.

In regions with hot summers, protecting the soil from overheating is an urgent problem. This problem is well solved by foliage, hay, straw, bark. Humus and compost have a loose structure, due to this, they protect the soil from overheating, but the effectiveness of these materials is much lower than that of foliage, hay, straw, bark. Compost and humus are dark in color, due to this they quickly heat up themselves. The needles weakly protect against overheating.

Mulch for moisture retention

Mulch helps to retain moisture in the soil at the roots of the plant. For this, the density of the mulch is also important. Here the places are distributed as follows: foliage, bark, hay, straw, compost. In this matter, you need to take into account the fact that when watering mulched ridges, more water will be required to wet the mulch layer and moisten the soil under it. The thicker the layer of mulch, the longer it retains moisture and the more water you need for watering.

Different mulching materials react differently to watering. For example, sawdust absorbs a lot of water, and until it is saturated, it does not let water through to the soil. The bark, on the contrary, almost does not absorb water, the water gets all the soil. During hot and dry periods, water the mulched areas less frequently, but more abundantly. If your main task is to save water, then it is worth considering an irrigation system under mulch.

Also, make sure the soil is well moistened before mulching. Light rains will not wet the mulch and the soil will remain dry, which means the plants will not receive nutrition. In areas where water stagnates in spring for a long time, you should not rush to mulch. Shaded areas are usually less prone to desiccation and a thinner mulch can be used.

Apparently, in regions with high rainfall, mulch is not required to retain moisture. In an arid zone, especially in a non-irrigated vegetable garden, it is extremely difficult to get a high yield without moisture-saving mulch, and this technique becomes decisive for an intensive vegetable garden.

By the degree of durability (time to complete decomposition)

In some regions, the need to use mulch is due to unfavorable climate factors: too hot or too dry. If you choose mulch based on these criteria, then it is desirable that the mulch last longer, without losing its properties. Such qualities are possessed by mulch, which does not decompose for a long time.

The leaders here are bark and sawdust, then in decreasing order of efficiency: foliage, straw, hay, compost.

According to the degree of accessibility and ease of use

Here everyone decides for himself, based on his conditions. Someone has the opportunity to prepare hay, someone has more access to straw or foliage. It is more convenient to use small organic material, for example, mulching the beds with root crops is more convenient with foliage than with hay or straw. If it is possible to grind organic materials, then this makes it easier to work with mulch.

In this matter, it is worth considering everything, studying the experience. It is possible that there is a way to get the right amount of mulch without much time, money and labor. Composting mulch is impractical. In this case, labor costs increase greatly, and the volume of raw materials decreases several times.

Beneficial or harmful effects on plants (allelopathy, acidity, etc.)

It has long been observed that plants react to their neighbors. Some of them stimulate growth, while others, on the contrary, depress. It is believed that litter and post-harvest plant residues have the same properties. For example, there is information that wormwood, wheatgrass, fire, feather grass do not allow other plants to grow next to them. It is possible that mulch from these plants will also have a negative effect on vegetable crops. Unfortunately, this topic has been little studied.

And it remains to be seen how mulch from a particular material affects specific crops. Applying different mulch on my site, I did not notice the oppression of plants by any kind of mulch. But this, of course, does not mean that there is no oppression or stimulation. There is a universal option that will allow you to avoid the strong influence of allelopathic plants: you need to make the mulch varied. The more ingredients the better. Then the influence of any one component will not play a role.

The constituent elements of the mulch can affect mulched plants through many factors. For example, such a fact is known. In the Main Botanical Garden in Moscow, wind-broken poplars and ash-leaved maples were passed through shredders, and then heathers were mulched with the resulting mass.

As a result, many valuable species of heather crops "fell out". For their full prosperity, they really need a layer of mulch, but only from coniferous pine litter, in which mycorrhizal cultures live and multiply, with which heather (like some coniferous crops) coexist in close symbiosis. Apparently, the wood and bark of poplars with maples contained substances poisonous for heather (or friendly mushrooms).

For different crops, you need to take into account the mulching time, the thickness of the mulch. For example, carrot shoots will easily overcome a centimeter layer of compost. But the same layer of straw, hay, leaves will be an insurmountable obstacle for tender sprouts - you will not wait for seedlings. But the seeds of mustard, radish, daikon centimeter layer of hay, straw pass.

Garlic shoots easily penetrate any organic mulch, but onion shoots are much weaker. Seedlings of beans and potatoes are very strong. You need to observe everything and use mulch based on these observations. So, it is better to mulch carrots after germination, and garlic, beans - immediately after planting. As a winter mulch for perennials, organic matter should be put after the ground is frozen.

The fraction of the mulching material also plays a role. Crops that develop slowly in the initial period of growth are best mulched with fine or chopped organic matter. It is necessary to take into account the preferences of plants for soil acidity. For example, facts are known when coniferous plants died after using deciduous tree chips as mulch under them.

By the degree of aesthetics

Here everyone has their own. For some, straw in the garden is not acceptable, while others easily put up with any organic matter. I think shredded organic materials always look better in the garden than whole ones. For example, bark mulch looks beautiful.

From all of the above, it is clear that no one type of mulch is ideal for both tasks. The material that is best suited for the first task - providing nutrition - is poorly suited for the second. And without solving the second problem, there will be no solution to the first. For example, compost mulch will dry quickly without watering. No water - no solutions - no food. You can, of course, make a layer of such mulch thick, then in the lower part of this layer we will get the necessary conditions. But thickening the layer will significantly increase labor costs.

The conclusion suggests itself that the ideal mulch should be flaky: on the bottom is the mulch that best solves the first problem (compost, hay), on top is the mulch that is more suitable for solving the second problem (foliage, straw). In nature, this is how it happens: fresh litter remains on top and solves the second problem, layers of organic matter are located below in varying degrees of decomposition, they solve the first problem, providing nutrition.

Read the next part of the article "About mulch without secrets":

Mulching - truth and fiction