Soils plant nutrition and environmental quality Chapter 15 of earth s surface is land Only of the land can be cultivated Is there any new land We must conserve and protect available land SOIL not dirt Possible definitions Weathered rock Surface earth layer where plants grow A blend of and plant nutrients Soil consists of 1 Minerals from parent material 2 3 4 Water and 5 Air Every soil has a profile O decaying plant debris humus duff A B accumulation zone less organic matter C Soil taxonomy provides a classification system for soil The soil type in the is an argic pachic cryoboroll profiles Accumulation of clay in B horizon Deep A horizon Mollisol prairie soil developed under conditions A soil type map Texture describes the of a soil Term Particle diameter 2 mm 2 0 02 mm 0 02 0 002 mm 0 002 mm is the ideal mix of sand A silt and clay for growing plants Relative sizes of soil particles Clay is 0 002 mm 2 m or 2 microns 35 m Clay particles are not just weathered rock but have been 1 m 8 m on clay crystals bind plant nutrients Pesticides and pollutants also bind Positively charged ions and minerals are bound to clay surfaces Clay mineralogy and geochemistry Soil texture classification triangle Most farm able soils Texture by feel Soil texture affects 1 Suitability for compaction crusting erodibilty water infiltration till abilty Soil texture affects 2 Texture Plant available water in ft3 Sand Loamy 1 5 2 2 Clayey 2 0 0 5 Capillary action Smaller pore sizes can Soil texture affects 3 Building and characteristics Soil fertility and nutrient cycling In natural ecosystems soil fertility plant growth and animal grazing exist in Also true for carbon cycle and other nutrient cycles The Nitrogen Cycle But in managed systems agriculture nutrients must be replenished because of Two sources of nutrients Fixed nitrogen from legumes Compost vs commercial fertilizer what s the difference Compost Low nutrient levels Improves tilth Not practical on large scale Fertilizer Nutrients Correct balance Efficient and economical Nitrogen is Nitrogen The Big Three Plant Nutrients N P K N P K Deficiency symptoms Nitrogen N Essential for protein content aids organic decomposition Phosphorus P Early and growth induces blooming and seed set Potassium K Important for disease resistance our most limiting resource in Montana Water and environmental quality Major pollution concerns 1 Loss of 1 32 of an inch of soil 5 tons per acre Soil can carry pesticide residues into surface waters Restricting can dramatically improve stream quality Preventing sedimentation No till farming cover crops Buffer strips Rice terraces in China Preventing sedimentation What can you do 3 Volunteer for trail crew 1 Stay on the trail 2 Show some respect 2 Fertilizer pollution Less than of the applied fertilizer is used by the crop is NO3 and is not bound to clay particles so it leaches easily cause eutrophication methemoglobine and mia Algal bloom Mississippi River drainage basin 930 tons yr 1 000 000 tons yr Conclusion we must use more efficiently Preventing fertilizer pollution Apply only enough for crop needs Precision Farming GPS and GIS GPS GIS Colors yield potential Apply fertilizer based on of 1 m2 field cells GPS GIS technology also used for weed mapping and pesticide applications Red wild oats 3 Salinization of soil All irrigation water contains some salts 20 of the world s irrigated cropland is affected by salinity A farm in the Imperial Valley CA using 5 acre feet of water from the Colorado River is adding 6 tons of salt per acre per year The only cure for salty soil is Water from coal bed methane wells contains a lot of salt Advanced civilizations in Sumeria and India collapsed by 1800 B C due to soil salinization Worldwide salinization destroys 3 hectares of cropland EVERY MINUTE 3 Saline seeps More than 80 million acres of land in the Intermountain West are susceptible to How do saline seeps form The driving force is Prevention and remediation of saline seeps 1 Implement flex cropping and crop rotations instead of continuous crop fallow 2 Locate the recharge zone and plant a to use the water 3 Plant salt tolerant species barley saltbush in seeps We did not inherit this land from our forefathers we borrow it from our children old Native proverb