The Garden Soil - Look After It If You Want To have A Garden In The Future! by Jonathan Ya'akobi

It is generally accepted by historians and geologists that a number of once flourishing ancient civilizations in different parts of the world, declined and disappeared, as it became increasingly difficult to grow sufficient plants for food, clothing and industry. This is known to have occurred for example in parts of the Middle East, India and California. Over time, not only did the soils' fertility decline, but they degenerated to the point where agricultural practice actually became impossible to sustain.

The culprit is believed to have been the ever increasing build up of salts in the soil, caused primarily by the practice of irrigation. The problem of rising soil salinity is liable therefore to become acute in any climate dry enough to require consistent and persistent irrigation. What happened in ancient Babylon, could and indeed will happen to you if common gardening tasks are carried out in a certain way.

Perhaps in 15 years time, some of your most treasured trees will start to show unusual signs of stress, while a number of years before, the flower beds declined. "Nothing grows in this bed anymore" is a common refrain. The soil, and therefore your garden could be saved however, if a holistic approach is adopted towards the soil, whereby the routine gardening tasks are performed not just to extract the most from the plants, but also to preserve, protect and develop the soil as well.

Why then is soil salinity a question of such paramount importance? The answer becomes apparent when the factors that determine a soil's health are understood in chemical, physical and biological terms.

*From a chemical standpoint, certain mineral salts, including trace elements required by the plants like iron, are poisonous when found in high concentrations. Furthermore, in accordance with the laws of diffusion and osmosis, increasing salinity decreases the plant's ability to take up water from the soil.

*Physically, the soil structure, that is the way the soil particles are arranged together, determines the amount of air available to the plants' roots. The soil structure can of course be damaged mechanically, such as by the affects of heavy traffic on wet, clay soil, known as compaction. However, certain chemical reactions, most notably when high sodium percentages are present, also destroy a soil's structure, and sodium percentages rise in accordance with the generally increasing salinity of the soil. Sodium soils are typified by "panned" layers which become impervious to the exchange of gasses and to water, meaning that they are soils chronically lacking in oxygen. They can take hundreds of years to recover.

*The soil's biology that is the quantity and variety of living organisms present, affects both the chemical and physical aspects, and is also affected by them. The more earthworms existing in the soil for instance, the better its aeration, as the earthworms' activities help to develop a healthy soil structure. While as the salinity increases the population of earthworms and other organisms declines. The extent and variety of life in the soil also has enormous implications as far as pests and disease are concerned. The more life, the more balance is created between the various organisms. In this way, the populations of potentially pathogenic organisms, whether they be insects, fungi or bacteria, are kept in check.

So what can we do to improve the soil? The answer as mentioned before lies in the way we carry out routine activities.

*Watering directly affects the salt concentrations in the soil. As irrigation water in dry climates is invariably saline in any case, it follows that each time we irrigate, we effectively add salts to the soil. If the irrigation schedule is based on small quantities applied frequently, then the salt concentrations will build up. It is necessary therefore, particularly in heavy, clay soils, to water infrequently, using large amounts each time. By so doing, excess salts are periodically leached out, leaving the winter rains to do the rest.

*Fertilizing of course entails the adding of mineral salts to the soil. Moreover, the regular application of chemical fertilizer, adversely affects the population of earthworms and other organisms. Thus although the plants may benefit at first from the ready supply of mineral nutrient, the long term implications for the health of the soil, are liable to be highly detrimental.

*The alternative to chemical fertilizers is the steady, consistent adding of organic matter to the soil, by way of compost or humus. Compost breaks down to release mineral salts slowly and in relatively small quantities. Except perhaps in the first year or so of a new garden, these quantities should be entirely adequate to supply the nutritional requirements of the plants. But the two principle benefits of compost are both related to the positive affects on the health of the soil. It directly increases the amount of oxygen available to the plants' roots, by improving the soil's structure, and by so doing improves the conditions for organisms like earthworms (which further in the development of good soil structure) and also provides them with the raw material necessary for their existence.

*The short term benefits of mulching, such as weed control, are well known. In the long term, an adequate mulch layer performs the vital function of protecting the top soil from rain and wind erosion.

About the Author

My name is Jonathan Ya'akobi. I've been gardening in a professional capacity since 1984. I am the former head gardener of the Jerusalem Botanical Garden, but now concentrate on building gardens for private home owners. I also teach horticulture to students on training courses. I'd love to share my knowledge and experience with you. So you're welcome to visit me on http://www.dryclimategardening.com