Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Chapter 7 Soil Fertility and Management Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Sixteen Essential Plant Nutrients Non-mineral: carbon, hydrogen, oxygen, nitrogen Mineral: macro: nitrogen, phosphorus, potassium secondary: calcium, sulfur, magnesium micro: boron, copper, zinc, iron, manganese, molybdenum, chlorine Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. The Importance of Nitrogen One of Earths most abundant and mobile nutrients Part of every plant cell, including chlorophyll, which gives plants their green color Subject to many physical, chemical, and biological processes that can result in significant losses of the nutrient Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Main Pathways for Nitrogen Loss Leachingnitrates are the type of nitrogen most subject to this kind of loss through movement of soil H 2 O Erosionnitrates move primarily in runoff H 2 O, while ammonium and organic forms of nitrate move with sediment, which can be reduced by using soil conservation Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Main Pathways for Nitrogen Loss (continued) Denitrificationsoil is saturated with H 2 O, bacteria convert nitrates to gaseous form of N 2, which is lost back to atmosphere Volatilizationurea is converted to ammonium carbonate, which in turn breaks down into ammonia gas, which is lost back to the atmosphere Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Nitrogen Cycle and Nitrogen Fixation Nitrogen cycleN 2 is converted to usable nitrogen and then back to N 2 (elemental or atmospheric nitrogen) Nitrogen fixationN 2 is removed from the atmosphere by rhizobia (soil bacteria) living in root nodules of legumes and converted to usable form Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Carbon:Nitrogen Ratios of Some Organic Materials Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil pH and Phosphorus Availability Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Potassium Second only to nitrogen in amounts used by plants Much of potassium found in soils is tied up by soil minerals Muriate of potash (potassium chloride) is primary source of fertilizer potassium; another source is potassium sulfate Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Nutrient Availability Nutrients in soil can be unavailable for plants to use because they are in insoluble chemical compounds Un-weathered or un-decomposed soil minerals or rock fragments organic matter or plant residues soil particles Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Function of Lime as Soil Additive Sweetens the soil (increases pH or alkalinity)most plants do not grow well in acid (sour) soil Improves availability of plant nutrients Increases effectiveness of applied nitrogen, phosphorus, and potassium Increases activity of microorganisms Improves plant growth and crop yields Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Choosing a Fertilizer Complete/mixedcontain three primary nutrients Should be selected based on economics, market availability, other factors, not solid versus liquid Placement is criticalGIS/GPS systems can help Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Choosing a Fertilizer (continued) Alternatives to commercially made fertilizers include manure: quality is affected by age/kind of animal, what it ate, amount/kind of litter/bedding used, way manure handled compost: especially good for improving soils low in organic matter Copyright 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Soil Management Concerns Erosionremoves topsoil and causes environmental problems; can be prevented by soil conservation Compactionusually caused by increased use of heavy farm equipment Drainagewell-drained soils can grow a wide variety of plants