Soil fertility physical

Borlaug N (1995) Fertilizer use in Sub-Saharan Africa - keynote address to the roundtable of science advisors for science-led development in Africa. Maputu, Mozambique Bulluck III LR, Brosius M, Evanylo GK, Ristaino JB (2002) Organic and synthetic fertility amendments influence soil microbial, physical and chemical properties on organic and conventional farms. Appl Soil Ecol 19 147-160... 

The transition from conventional to organic and low-input farming is accompanied by changes in an array of soil chemical properties and processes that affect soil fertility. Fundamental differences, both qualities and quantitative, in the flow and processing of nutrient result from the use of cover crops, manure and compost applications, and reduction or elimination of synthetic fertilizers and pesticides. These changes affect nutrient availability to crops either directly by contributing to nutrient pools or indirectly by influencing the soil chemical and physical environment. 

The soil s supply of organic matter plays a central role in the maintenance of soil fertility. Its environmental relevance is based on the capacity of soil organic matter to limit physical damage and to improve nutrient availability as well as biological activity. 

Table 2.2 Examples of differences in soil physical, biological and chemical characteristics of soil fertility in long-term field trials that include organic... 

Studies concerning soil fertility and plant nutrition usually involve the determination of the nutrient concentrations in a soil extract, which can be related to nutrient bioavailability. There is increasing interest in the chemical and physical characterisation of the different forms of nutrients in soils and a common approach is to fractionate the nutrient species according to their extractability by leaching reagents of increasing aggressiveness [38]. This provides relevant information on nutrient availability to plants, the nutrient capacity of soils and nutrient mobility. 

The soil pH considerably affects soil characteristics. It is important for many soil-forming processes and it also affects the biological activity of soil organisms. The soil pH directly affects particularly the solubility of many substances, ion adsorption and desorption, coagulation and peptization of colloids and chemical reactions. By its action on the soil structure it also affects most of the physical properties of the soil. Thus, the soil pH is an important parameter of the soil fertility. 

Soils of the humid region and Temperate Zone that were at one time productive often become comparatively nonproductive after several years of cropping if little attention is given to maintenance of soil fertility. Among the chief reasons for the decrease in yields are decrease in available nutrients increase in acidity lack of adequate organic matter poor physical condition build up of toxic substances plant diseases insects and weed competition. There are other possibilities, some of which are closely related to the above, namely inadequate aeration, hard pans, slow infiltration, and poor drainage. 

The type of soil, its chemical and physical properties are as equally important as the climate regarding the selection of crops and their yield. To maintain soil fertility and to prevent soil degradation are key factors for a sustainable yield. Although all management and harvesting operations should be soil-friendly, soil compaction due to heavy machinery and soil erosion due to unadjusted cultivation methods are still a problem in agriculture and forestry. 

Soil Science Society of America Journal. 1936- Madison, WI Soil Science Society of America (0361-5995). Online https //www.crops.org/publications/sssaj (1435-0661). Subjects include soil and water management and conservation, pedology, soil fertility and plant nutrition, soil mineralogy, soil physics and nutrient management, and soil and plant analysis. 

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