Preparing the Soil for Planting a Lawn and a Garden

The soil is the medium within (and on) which lawn and garden plants grow, and accordingly it must supply the plants with nutrients, water and air.

In addition, in the case of lawn, the soil must provide a surface to walk on.

The storage capacity of a storeroom is determined by its volume, the number of shelving units it contains, and the spacing of the shelves in each unit, while the width of the passages between these units determines the storeroom’s handling rate and capacity.

The soil is composed of particles (‘shelves’) of various sizes carrying varying electric charges. The texture of the soil reflects its composition in terms of: the size of the particles and the particle size distribution; water content; nutrients (in the form of minerals) adsorbed on the surface of the particles. The greater the number of small particles in a given volume of soil (in other words, the greater its surface area), the greater will be the adsorption capacity of that soil.

Soil particles clump together to form aggregates (the ‘shelving units’). The stabler and the larger these aggregates, the larger the free spaces (pores) provided by the soil structure. Such pores promote free and rapid flow of water and gases and make it easier for roots to grow and reach the moisture and nutrients.

Hence it is desirable to have a soil with large aggregates – aggregates that in turn consist of smaller particles – because such a soil structure will have a large nutrient and moisture storage capacity and at the same time will allow free passage of air, ensuring a favorable exchange of gases (penetration of oxygen and other essential gases and removal of carbon dioxide and other harmful gases).

The volume of the ‘storeroom’ is determined by the following factors.

1.      The depth of the root zone. The root zone is the soil layer in which the plant’s roots are active. In most species and varieties of warm lawn grown in Israel, the root zone extends to a depth of 150 cm. The root zone of water-sparing shrubs and trees, on the other hand, reaches down to 7‑17 m (as measured at Nir Oz; see also the article entitled  Landscaping as a Basis for Harvesting Water Run-Off'.
and the illustration in the presentation “Our garden in the desert – an ecological success story

2.      The depth of the soil. As the storage capacity of the soil increases, so will the reserves of food and water available to the plant (provided we replenish them in time), and correspondingly the more infrequently these reserves will have to be recharged. Aside from convenience and labor savings, less frequent reloading also reduces damage and risks associated with errors in timing and volume delivered.

Most lawns are expected to serve as a surface to walk on, as well as for recreation, games, sports, or even parking. Treading exerts pressure on the soil, resulting in compaction of the aggregates, destruction of soil structure, and ultimately exclusion of air and water from the soil. To withstand the strong pressures due to walking, the soil must have a stable structure.

Sandy soil is composed of relatively large particles that lack electric charge. Sandy soil has a poor ability to store nutrients and water, but has a well aerated structure that is penetrable to water. Its structure is very stable and resists compression, and such a soil is therefore suitable for conditions of pressure and treading.

Heavy soil is composed of many small particles bearing an electric charge. Its nutrient and water storage capacity is very high. Its penetrability to air and water will be determined by its structure – the coarser the structure (larger aggregates) the better.

Light soil is a mixture of small soil particles and sand. Its properties are intermediate between those of sandy and heavy soils and are influenced by the proportion of each particle size class present.

It should be mentioned that the terms ‘light’ and ‘heavy’ refer to the ease or difficulty of cultivating the soil and have nothing to do with its weight.

Soil preparation is designed to enable cultivation over the long term. Any error or omission in the process of preparation will be very difficult to repair after planting. Therefore this is not the place to economize on materials and means. Every ‘savings' before planting will result in significant loss in terms of maintenance of the lawn and its quality.

1.       Clearing and shaping the topography to conform to the landscaper’s plan

2.      Deep plowing

3.      Applying compost or fertilizer

4.      Final grading of the surface

5.      Planting the lawn

From the Foreword it follows that if we wish to provide a uniform supply of nutrients, water and air throughout the lawn or garden, as well as enable uniform treatment in the future, we have to make sure that the soil composition and soil depth are everywhere the same. If the soil is especially shallow in a certain section, then in that section the supply of water will be limited and irrigation will have to be supplied more frequently than to the rest of the lawn; alternatively, the entire lawn (garden) will have to be watered abundantly to meet the needs of the shallow section. The same applies to a sandy spot surrounded by heavier soil.

Construction waste – All construction and other waste must be removed or buried at a depth of at least one meter (1.5 m is desirable).

Adding soil. When soil is added to shape the surface in accordance with the landscape plan, it is important to make sure that the thickness of the imported soil is the same throughout the lawn and garden. The local soil should be shaped ? graded accordingly, and any ditches and pits must be filled.

Soil that has been disturbed at a depth exceeding the tilling depth must be lightly compacted (see next chapter). Compacting should be carried out in layers 30 cm thick. This step is intended to prevent future sinking of non-uniform soil and facilitate proper grading of the lawn.

Before choosing a source of new soil, the earth at the excavation site must be tested and a professional consulted. The added soil should be of the same type as, or lighter than, the natural soil of the garden. It must not be heavier than the natural soil. A heavy soil laid on top of a lighter one will mean excess moisture and lack of air at the interface between the two types of soil. Similarly, when the garden soil is sandy, a heavier soil must not be laid on top of it.

If the decision is nevertheless taken to lay a heavy soil on top of sand, two conditions must be met: 1) the added layer must be at least 50 cm thick, and from the perspective of the root zone the thickness of the soil must be taken to be 50 cm in all; 2) the added soil must be medium and must have a good texture and structure.

If the aim is to raise the overall level of a site allocated to lawn and the local soil is very heavy and impenetrable, it is recommended that a 20 cm-thick upper layer of sandy soil or sandy loam be added. This measure should reduce future problems of compaction due to treading on recently watered lawn. It should also benefit the garden as a whole by improving both runoff collection and the growing conditions of the plants in the garden (see also the article entitled“Landscaping as a Basis for Harvesting Water Run-Off”. and the illustration in the presentation “Our garden in the desert – an ecological success story”

When the work has been completed, the surface contours should conform precisely (accurate to within a few centimeters) to the landscaper’s plan.

The conditions that lawn plants need in order to thrive and the considerable depth of their root zone were noted in the Foreword. The same considerations apply to water-sparing garden plants. So the deeper we plow, the better.

On large sites where tractors can be used, cultivation should be carried out with a subsoiler to a depth of 60 cm and, where possible, even deeper. In small gardens that is impossible, of course, and we must be satisfied with cultivating with adigging fork to a depth of 25 cm. The practice of cultivating with a hand-held tool (rotevator)is to be avoided since this instrument can penetrate to a depth of 10 cm at most and for the rest just ‘throws up’ the soil.

When adding earth or sand to alter the contour of a site (see previous section), it is desirable to plow before importing the soil, then wait for the local soil to dry (this is important when heavy machinery is to be used), and only then add the soil – making sure to drive the tractor over the imported earth. This makes it possible to achieve a greater depth of cultivation.

The question of whether to use compost or rely on chemical fertilizers alone, and if compost then what kind, will be discussed in a separate article.

When applying compost (organic fertilizer) for the purpose of improving the properties of the soil, it is important to work in the compost (fertilizer) to a depth of 20 cm at least (use of a hand-held rotevator should be avoided since this tool can reach down to 10 cm at best and for the rest just blows up the soil). Shallower application will not result in significant improvement in terms of meeting the needs of the lawn and garden plants. However, when adding manure or fertilizer to provide nourishment, shallow tilling to a depth of a few centimeters is sufficient (except in the case of phosphorus, which does not percolate through the soil and must be buried at a greater depth). Here precise contouring of the surface prior to application of manure or fertilizer is especially important. Flattening of the surface and attendant shifting of earth, if carried out after shallow burial of manure or fertilizer, will cause the latter to slide down from the high spots, which will then be lacking in these materials.

In this step the site is graded to a precision of 1-2 cm. Over large areas this is done with the help of a tractor and leveller, but in a small garden a rake is used. There can be no compromises here, for any defect will be difficult to repair after the lawn grows. A section that is not properly smooth will be difficult to mow and will impair the appearance of the lawn.

Once all the steps outlined above have been carried out faithfully, the site is ready for planting. Now – assuming a species or variety of lawn suited to the conditions of the garden and pleasing to the eye has already been selected – all that remains to be done at this stage is to choose a planting method.

The main planting methods are:

a.       Planting sprigs using a planting awl

b.      Broadcasting sprigs

c.       Laying sod grass carpets

*       Lightly water the soil the day before so it will be moist during planting.

*       Placesprigsof the species or variety chosen in a damp, shady place till ready to plant.

*       Prepare sprigs 3-10 cm long and having at least threenodes, then proceed to plant. If the topsoil is loose and soft, insert the sprigs using your fingers, then tamp the earth down. If the soil is too hard use a planting awl. If the planting area is large, you can make a planting fork out of ¾" pipe fitted with four pointed tines of the same diameter with intervals of 20-30 cm between the tines.

*       Planting intervals should be from 10 x 10 cm to 30 x 30 cm depending on the growth rate of the particular variety and the desired surface covering rate.

*       Go over the planting site with a roller (the roller should not be excessively heavy; we are not building a road); a barrel one third or one half filled with water may be used for this purpose. The task of the roller is to press the sprigs into the soil and to give a final grading to the surface.

*       Water thoroughly to a depth of about 15 cm. Make sure to water before the sprigs dry out. Depending on the weather, the entire process from start of planting to watering should take 20 to 60 minutes. Subsequently, irrigate several times a day, providing enough water to keep the soil surface damp; however, do not over-irrigate – water must not run along the surface. The sprigs will strike root within a week or two (depending on the variety and the weather), and the frequency of irrigation can be reduced gradually, finally reaching the regime recommended for the particular soil and garden location (see article Planting in furrows is not advisable: it involves more labor, and the soil surface does not remain flat.

b. Broadcastingsprigs

In this method, sprigs removed with a verticutter are broadcast. This method calls for a greater degree of expertise than shoot planting, and also for a special irrigation system and a timer (and water meter).

In general, the order of operations is as follows:

*       Install the special irrigation system the previous day and check that the timing device is working properly. If the sprigs are to be scattered by hand, apply light watering to produce a moist soil. Ifscattering mechanically by broadcasting, the operation should be done on dry soil.

*       Scatter at least 3-4 times as many sprigs as is the practice in planting sprigs by hand (because not all the sprigs will take root). The maximum number: enough to completely cover the surface without overlapping.

Note: beside sprigs, the material scattered also contains many leaves and other dry material that should not be included when calculating sprig numbers. In warm, dry weather it is desirable to plant in the afternoon or even towards evening. The planting material must be kept moist and should be stored in the shade. Take care not to compress the pile of seedlings once they are taken out and until planting; this is to avoid generating heat that could kill the seedlings.

*       Press the sprigs into the soil with a roller (see previous section).

*       Water generously so as to wet the soil to a depth of about 10 cm. It is important to plan the planting stage so that not more than 15-20 minutes elapse between scattering of the sprigs and subsequent watering. Large plots should be sown section by section.

Irrigate in the morning when the dew begins to evaporate and continue until dew fall in the evening. On particularly dry nights (hamsin), watering should be continued throughout the night. The irrigation should be applied in pulses of 2 minutes separated by 5 minute breaks on hot dry days, and in pulses of 3 minutes separated by 10 minute breaks on cool humid days. In all cases, make sure the seedlings (not the soil) do not dry out. For more detailed instructions consult a gardening expert and read the article entitled 'Suggestions for pulse irrigation during mechanized lawn planting' by Arnon Toubi in Gan ve Nof (35:8, May 1980).

Planting should be carried out according to the instructions of the nursery supplying the grass carpets. A number of rules should be followed:

*       Do not spray anti grass-germination products on the surface prior to planting, as these compounds penetrate into the plant via the roots. This is to prevent injury to the roots contained in the grasscarpets placed over the sprayed surface.

*       Do not plant carpets removed (together with a thin layer of soil) from a nursery with a heavy soil in a plot with a light or sandy soil (see earlier explanation about the inadvisability of placing heavy soil on a light soil). If there is no other option and you must transfer carpets from a heavy to a light soil, then cultivate the plot after planting with an aerator (removes small cylinders of soil) and fill the holes with sand. The depth of cultivation should be slightly greater than the thickness of the carpets. For precise instructions consult a gardening expert or nursery.

*       Before purchasing a given species or variety of lawn grass from a suitable plant nursery, be sure to consult a gardening expert. The importance of seeking professional advice before making a choice cannot be overly emphasized.

The soil must be prepared for cultivation over a period of many years. Any error in carrying out the various steps that precede planting will impair the development of the lawn and garden plants and will be difficult to rectify at a later stage.

In particular, errors are prone to arise in connection with the following recommendations, which are crucial:

*       Make sure that the type of soil is uniform throughout the garden and (especially) the lawn. When laying different soil types one on top of the other, make sure the thickness of each layer is uniform, with the lighter soil always overlaying the heavier one. (The special circumstances in which this rule may be infringed are given above.)

*       Plow as deeply and as thoroughly as possible.

*       Grade the sited perfectly prior to planting.

*       Make sure the garden plants and the species or variety of lawn chosen are appropriate to the conditions of the region and of the garden in which they are to be planted.

*       The different methods of lawn planting are described in detail.