First of all, I have to say I am sorry for the title. 😉 To make a living on the internet, you have to make use of proper keywords. But it makes it sound like we’re trying to get the soil pregnant… just had to laugh at that one. Seriously, soil fertility is concerned with the resident holding power of soil to provide nutrition in satisfactory amounts and in proper balance for the growth of your plants when the other growth factors like light, moisture, and temperature and the physical condition of the soil are appropriate. Soil fertility is one facet of the soil – plant relationship, namely plant growth, with reference to plant nutrients available in soil. A fertile soil is considered to be one that delivers plenty of food for harvest if there are also acceptable environmental conditions. Only a very small fraction of the total nutrient content of soil can be put to use by plants. To get a quick measure of nutrient availability let’s look at the following soil fertility evaluation methods…
- Visual evidence of nutrient deficiency or toxicity
- Plant evaluation
- Soil evaluation
Soil factors influencing nutrient availability
Soil reaction (pH) is the single most important consideration that regulates availability of plant nutrients in the soil. The pH range of 6.5 to 7.5
is the optimum for availability of most of the nutrient availability.
The ammonifiers and nitrifies are active at pH 5.5 to 6.0, below this level, nitrogen availability decreases.
Phosphorus availability is maximum in the pH range of 6.5 to 7.5. In red and lateritic soils
the phosphate availability depends on the amount of sesquioxides. Liming of acid soils increase phosphate availability.
Potassium availability depends on exchangeable potassium, potassium saturation of exchange complex, CEC and pH.
- Calcium, Magnesium
Calcium and magnesium are available in cationic form and their availability is decreased governed by the factors which control exchange equilibrium in soil at low pH (below 6.0) their availability decreases.
- Micro Nutrient Availability
These are also available at low pH range. Alternate drying and heating the soil increases the availability of manganese in the soil. Availability of boron decreases below pH 5.0 and above 7.0 but above pH 8.5 it again increases. (weird, huh?) Availability of molybdenum increases above pH 6.5. As an aside, Molybdenum is important no, essential for symbiotic nitrogen fixing bacteria in legumes. Molybdenum is the only micronutrient that has increased availability as the pH increases.
The end result of all this, what may initially appear as technical jargon is that instead of looking for places that have good soil, know you can work with what you have and easily improve almost any soil issue using good sustainable gardening methods.
Maintenance of Soil Fertility
Nutrients are progressively removed from the soil by plants in addition to losses by leaching and erosion. Nutrients you add can and do simply wash away. It is essential then that responsible soil nutrient practices are learned and implemented to improve and maintain soil a teeming soil life and a healthy soil condition for the purpose of sustainable food growing. Below are a few good organic, sustainable habits to adopt that will pay off in your garden in spades…
Increased organic matter, nitrogen supply and improved soil structure are the major benefits of basic organic gardening habits. Plant deep rooted legumes or crops capable of feeding themselves efficiently at a variety of soil depths. Deep rooted crops increase the ability of air and water to reach further into the soil.
Balanced fertilization with nitrogen, phosphorus and potassium fertilizers found naturally helps in maintaining soil fertility. Application of organic manures helps to improve and maintain soil fertility, soil productivity and healthy soil condition. Soil fertility and growing food can be sustained only by efficient
and consistent addition of nutrients to the soil from external sources.
Organic manures bind sandy soil and improve its water holding capacity. They open a clay soil and help in aeration for better root growth. They add basic plant nutrients and also add micro nutrients which are essential for plant growth. Microbial activity is increased which helps in releasing plant nutrients in the soil. Compost from organic waste, night soil, sludge, sewage, sheep folding, green manures, blood meal, fish meal, bone meal can be applied. Organic manures should be added to soil before planting because of the slow release of nutrients.
- Soil factors
Coarse textured soils are poorer in available nutrients than fine texture soils. Hence, it is necessary to apply nitrogenous, phosphatic and potassic fertilizers more frequently than in fine texture soils. The higher the soil fertility the lower the response of crops to it’s addition. Soil reaction is important in the selection of the right type of phosphatic fertilizer. Efficient use of fertilizers by the food you are growing is
greatly increased when the organic matter of the soil is in greater supply.
- Climate Factors
Climate affects both food growth and the life cycles of soil organisms. Hot, dry desert regions have sparse vegetation so there is a limited amount of organic material available to feed the soil. The lack of water (rain, snow or otherwise) inhibits chemical weathering which most often leads to a coarser textured soil in arid regions. Bacterial activity is limited in colder zones causing organic matter to build up. In the warm and wet tropics, bacterial activity is quick and thorough. In the tropical forest, available nutrients are rapidly taken back up by the trees. The great bit of annual rain fall here also flushes organic material from the soil. These factors combine to create soils lacking much organic matter in their higher areas.
In a more arid regions soil moisture is a limiting factor. If soil moisture is conserved efficiently soil amendments become very effective.
Reclaiming a Problem Soil
Problematic soils; acidic, saline and alkaline soils can be brought back into a healthy growing condition for growing nutrient dense food. Acidic soils can be corrected by liming.
Saline and alkaline soils can be reclaimed by improving drainage scrapping off surface soils and using gypsum, sulphur, molasses and adopting sustainable gardening practices like green manuring, adding organic manures, mulching and suitable crop rotation.