Sand, biochar, zeolite and Actino

Establishing a lawn gives us the chance to provide good conditions for the roots from the start. Actino adds organic matter and nutrients that are released gradually into the soil. It makes the most sense where the soil is poor and has not had its organic matter replenished for a long time. Alongside sand and soil, we therefore add a material that soil organisms can continue to work on.

Actino is grape compost made from the pomace left after processing grapes. Controlled decomposition in the presence of air, known as aerobic humification, turns it into a soil amendment. Its origin and production method are described by the manufacturer. While sand changes the arrangement of soil particles, Actino adds organic matter and nutrition. It can be used during soil preparation and later when fertilising the lawn, following the product instructions.

In our examples, we give it the largest share in poor sand that dries out quickly. In heavy soil lacking organic matter, we use a smaller proportion; in a well-maintained loamy garden, we do not add it to the base mixture. Specific rates for each garden are given in the next article on mixture ratios. If the soil lacks organic matter, include Actino in the preparation before sowing, when it can easily be mixed into the future root zone. Account for the nutrients it supplies in the fertiliser plan.

We water, but light soil soon dries out again. This is exactly the kind of garden where biochar is worth considering. Its small pores can retain some water, and its surfaces can help hold some nutrients. Part of this store may therefore remain in the root zone for longer. For a lawn on poor sandy soil, this is a good reason to consider what we mix into the soil when establishing it.

Biochar is made by heating organic material with a limited supply of oxygen. Some of the carbon remains in a solid, porous material containing many small spaces. Once evenly mixed in, it can be thought of as small stores scattered among the soil grains. How well they work depends on the soil, the properties of the particular biochar and the chosen dose.

For straightforward preparation, choose biochar intended for soil, already charged with nutrients and ready to incorporate. Uncharged biochar can initially take up some nutrients from the soil, so prepare it before use, for example with moist compost. Water alone does not replace this charging. The next section explains what to check before buying and how to account for compost contained in the product.

Zeolite can capture some nutrients, hold them and gradually release them back into the soil, where grass roots can use them. For example, it helps retain potassium and some forms of nitrogen that might otherwise be washed out with water.

Think of it as a small nutrient store. Its capacity is not unlimited and it does not hold all nutrients equally well, but it can keep some nutrition within reach of the roots for longer.

In the next article on mixture ratios, we use clinoptilolite zeolite with a grain size of 0.5–⁠1 mm. The proportion needed differs from one garden to another.

The soil itself helps explain why. Clay particles and organic matter can already retain some nutrients on their surfaces. The technical term for this ability is cation exchange capacity. Poor sandy soil has fewer of these sites, so we give zeolite a larger share in it. For practical work, the implication is straightforward: start with a smaller dose in heavy soil and a larger one in light sand. Zeolite does not, however, replace loosening compacted soil or draining excess water.

A young lawn initially has small roots with a limited reach. Mycorrhizal fungi can form a partnership with them, in which their fine threads extend the area available for taking up nutrients. This can let the plant use some of the nutrients that its roots alone could not yet reach. This partnership is where the benefit of mycorrhiza lies.

For lawns, choose a suitable product containing arbuscular mycorrhizal fungi. The fungus helps the plant take up nutrients and receives carbon from it in return. We mainly consider adding a product after substantial reconstruction or when establishing a lawn in a predominantly new mixture containing little biologically active soil. Suitable fungi may already live in established garden soil, so adding a product may not provide the same benefit. The outcome depends on the particular soil, product and conditions for the partnership.

When establishing a lawn in a new mixture, have a suitable product ready before sowing, so that, following the instructions, it can be placed where young roots will encounter it. Mycorrhiza is not applied as a percentage of volume like zeolite: we are adding living fungi, not another share of the mineral mixture. The product’s composition, recommended application rate and correct placement matter, not simply the proportion of sand or clay. This gives the purchase a clear purpose: supporting the partnership in the new root zone.