-Anchors plant -Basic physical properties of soils and-Fertilizer the factors that govern soil qualities.-Helps retain water -Why certain inorganic nutrients are-Holds nutrition for plants essential for plant function. -Nutritional adaptations that have evolved in plants, often in relationships with other organisms.
Soil particles are classifiedby size from largest tosmallest:-Sand-Silt-Clay-Soil is stratified intolayers called soilhorizons.A type of topsoil calledloam is the most fertile.
Organic ComponentsHumus retains water andmineral nutrients. Also itincreases the soilscapacity to exchangecations.Topsoil contains manyorganisms that helpdecompose organicmaterial.
The goal of sustainable agriculture is to use faming methods that are conservation-minded, environmentally safe, and profitable. Irrigation Fertilization Adjusting Soil pH Controlling Erosion Preventing Soil Compaction Phytoremediation
-Plants & soil have two-way relationshipMany of the soil bacteria are calledsaprobes-lives on decaying organic material-Rhizobacteria-soil bacteria w/especiallylarge population in rhizosphere (soil layerbound to plant roots) Some are called plant-growth-promoting rhizobacteria then enhance plant growth by a variety of mechanisms
-Nitrogen Cycle-describes transformations ofnitrogen & nitrogenous compounds in nature-Nitrogen-fixing bacteria converts atmospheric N2to nitrogenous minerals that plants
•Plants absorb nitrogen as either NO3–or NH4+•Bacteria break down organic compounds or use N2to produce NH3, which isconverted to NH4+•Nitrification is carried out by bacteria that convert NH3 into NO3–
Nitrifying bacteriaadds free nitrogen or nitrates to the soil by the process ofnitrification.Ammonifying bacteriaconverts ammonia into nitrates which is convertedinto free soil nitrogen by nitrifying bacteria.Denitrifying bacteriareduces nitrates or nitrogen gas; most are found in soilNitrogen fixing bacteriahas an association with bacteria which infect theirroots and in return for sugars from the plant, fix nitrogen which can be used bythe plant for growth.
-Nitrogen fixation: conversion of nitrogenfrom N2to NH3-The agricultural perks of mutualisticnitrogen fixation underlies most types ofcrop rotation
-Mycorrhizae: mutualisticassociations of roots & fungi -The fungal hyphae of both ectomycorrhizae and arbuscular mycorrhizae absorbs minerals and water to which they supply to their roots.
Epiphytes Absorb water & minerals from rain, mostly through leaves not roots. Ex: staghorn fernParasitic Plants Absorb sugars & minerals from living hosts, although some species are photosynthetic. Ex: mistletoeCarniverous Plants Photosynthetic, but they obtain some of the minerals by killing & digesting insects & other small animals. Ex: venus fly trap