1. Overview and importance of soil fertility

2. A fertile soil is one that contains an adequate supply of all the nutrients required for the successful completion of plant life cycle 2 Soil Fertility Overview and importance of soil fertility The overall ability of a soil to support vigorous crop growth by ensuring adequate plant nutrients in balanced proportion and suitable conditions for water uptake, and by providing favorable conditions for root growth and development OR

3. 3 Better management of physical and chemical soil fertility improves soil biological fertility, which in turn can be further enhanced by good agronomic/ culttural practices. Hence, soil fertility is a key to sustainable agriculture (see next slide) Soil Fertility A fertile soil is essential for optimum productivity, profitability, protection of ground water quality and soil from erosion. Soil fertility is divided into 3 groups, i.e. Physical, Chemical and Biological Soil Fertility, which are inter-related with each other (see next slide). Overview and importance of soil fertility

4. Soil Fertility Chemical Physical Biological Bacteria (Living) plant roots Fungi,actinomycetes Other organisms Agronomic/ Cultural practices Improved soil fertility and productivity Sustainable agriculture Rhizosphere Soil Fertility Chemical Physical Biological Overview and importance of soil fertility

5.  Biological soil fertility: The capacity of organisms living in soil to contribute to the nutritional requirements of plants and foraging animals for productivity, reproduction and quality while maintaining biological processes that contribute positively to the physical and chemical state of the soil.  Chemical soil fertility: The capacity of soil to provide a suitable chemical and nutritional environment for the plants and foraging animals for productivity, reproduction and quality in a way that supports beneficial soil physical and biological processes, including those involved in nutrient cycling.  Physical soil fertility: The capacity of soil to provide physical conditions that support plant productivity, reproduction and quality without leading to loss of soil structure or erosion and supporting soil biological and chemical processes. Overview and importance of soil fertility

6. Components of soil fertility Soil depth (determining the volume of soil accessible to the root system). Most arable crops prefer about one metre without any obstructing layer. Soil structure (based on size distribution and aggregation of particles). This determines the distribution of pore sizes which is decisive for the supply of air and water to the roots. 6 Overview and importance of soil fertility

7. International size units used to classify soil particles in terms of their mean diameter are:  gravel (> 2.0 mm);  coarse sand (2.0–0.2 mm);  fine sand (0.2–0.02 mm);  silt (0.02–0.002 mm);  clay (< 0.002 mm). Components of soil fertility Overview and importance of soil fertility It designates the proportion of different particle size fractions in the soil. Of special importance to soil fertility is the percentage of soil particles of less than 2 mm in diameter, which constitute the fine soil. Fine soil is composed of particles in three size groups: sand, silt and clay. 1. Soil texture

8. Soil texture influences to a large extent several components of soil fertility such as the amount of nutrient reserves and their proportion to the available nutrient fraction. It also influences several properties such as aeration, pore space distribution, WHC and drainage characteristics. Components of soil fertility Overview and importance of soil fertility

9. 9 Content of nutrients with different degrees of availability. Storage capacity for soluble nutrients from the soil and fertilizers. Soil pH/ reaction (an indicator and regulator of chemical processes and equilibria). Components of soil fertility Picture shows the availability of nutrients at different soil pH Overview and importance of soil fertility

10. 10/15/201510 Content of detrimental or toxic substances, either naturally occurring (e.g. salts in saline soils, aluminium in extremely acid soils) or man-made (e.g. from pollution). Quantity and activity of soil organisms as agents of transformation processes. Components of soil fertility Overview and importance of soil fertility

11. Components of soil fertility Nutrient gain as a result of N fixation from the air. It influences promotion or retardation of growth through growth hormones. 2. Soil Organic Matter (SOM) It promotes soil structure improvement by plant residues and humic substances leading to higher WHC, better soil aeration and protection of soil against erosion. Helps in keeping the nutrients in available forms and protecting them against losses. Nutrient mobilization from decomposed organic nutrient sources and mineral reserves: N, P, S, Zn, etc. Overview and importance of soil fertility

12. 12 It is important to note: Soil productivity is the crop yielding ability of a soil from a unit area. Soil fertility is vital to a productive soil but, a fertile soil is not always a productive one. Poor drainage, weeds, insects, disease, drought and other factors can limit productivity even when fertility is adequate. Fertile soils are not always highly productive, but the productive soils are always fertile. Very fertile and productive soils are rarely found in nature Overview and importance of soil fertility

13. A highly productive soils with high fertility: mobilize soil nutrients from the reserves; transform fertilizer nutrients into easily available forms; store water-soluble nutrients in easily available forms, thus preventing leaching; offer the plants a balanced nutrient supply due to its self- regulating system; store and supply sufficient water; 10/15/201513 Overview and importance of soil fertility

14. A highly productive soils with high fertility: maintain good soil aeration for the oxygen requirements of roots; not 'fix' nutrients, i.e. convert them into unavailable form; Improve crop use efficiency of nutrients and resources such as water and light; and Provide nutrients throughout the growing season and especially during critical peak periods of plant development 10/15/201514 Overview and importance of soil fertility