Department of Horticulture and Landscape Design, College of Agriculture, University of Basrah, Iraq
Many researchers have pointed out the importance of the agricultural medium in the growth of seedlings, where the components of the medium from the soil, soil disintegrating materials and moisture preservatives play an effective role in this. The organic matter added to the soil has a significant impact on improving the physical, chemical and biological properties of the soil, so that the light sandy soil becomes more coherent and the clay soil more disintegrated, thus providing the oxygen necessary for the respiration of the roots and the activity of microorganisms. Atmospheric oxygen or dissolves in water, forming carbonic acid, and nitrogen turns into ammonium ion (NH4), and then turns into nitrate (NO3) and sulfur into sulfate ion.The organic media also contains several major and minor nutrients and other rare elements, where the organic matter is a source of supply for plants and microorganisms with these nutrients necessary for its growth, in addition to improving soil porosity, regulating water and air movement, the spread of gases, and increasing the water holding capacity of the soil. Increasing the cation exchange capacity of positive ions (C.E.C) and lowering the soil pH. The organic compounds work in mixing the nutrients and preventing sedimentation in the soil, thus increasing its readiness, especially the microelements. The slow decomposition of the organic matter will provide the plant with nutrients for a sufficient period of time.