FANR 3060 1st Edition Lecture 18Outline of Last LectureI. MacronutrientsII. Secondary ElementsIII. Micronutrient CationsOutline of Current LectureI. Micronutrient AnionsII. Soil OrganismsIII. Roles of Soil OrganismsChapter 6I. Micronutrient Anionsa. MoO4(-3), BO3(-3), Cl-b. Chloride: never deficienti. Toxic in saline soilsc. MoO4 and BO3i. Similar to PO4 (covalent)ii. Strongly absorbed by Fe oxides at love pHsiii. Soluble at high pH, insoluble at low pHiv. Deficient in acidic sandy soils in Eatern USv. Toxic in alkaline soils of Western USThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.d. Contaminantsi. Arsenic/arsenate (ASO4(-3)) and selenium (SeO4-)1. Arsenic is soluble in alkaline conditions, insoluble in acidic conditionse. Fig 6.6i. 6 is the best pH to have soil at1. Everything is mostly in balanceii. Generally, pH doesn’t affect N muchiii. On the phosphorus curve1. Becomes insoluble again at high pHs/high base saturation because apatite reforms and becomes insolublef. Pb3(ASO4)2i. Lead arsenateii. Fertilizer in late 60s1. Added a lot of lead and arsenate to orchard soilsChapter 7II. Soil Organismsa. Macroorganismsi. Insects (ants, termites), earthworms, moles, etc1. Earthworms eat an acre furrow slice (2 million pounds) every 30 yearsii. Important burrowers and mixers1. Initially decompose residue in O horizon2. Mix organic material in A hroiza. Essentially make the A horiziii. 300 lbs/acre, 100s of millions/acre1. Especially in forestb. Microorganisms (microbes)i. Bacteria, fungi, actinomycetes, algae, protozoa1. Bacteria = aerobic and anaerobicii. Most important decomposers in the soil1. Break down plant residues into CO2 and residual humusa. Nutrient cyclingiii. LOTS of these in the soil1. Bacteria multiply rapidly a. 1020/acrei. This is a millimol2. Fungi decompose ligninsa. 1016/acreb. Don’t mind acidic soil3. Total biomass/acre = 10 tons fresh weight, 2 tons dry weightIII. Roles of Soil Organismsa. Important effect on many soil processesb. Soil formationi. Mixers: create A horizon (humus)ii. Modify soil to make it more favorable for their growth1. Granular structure, tilthc. Decompostitioni. Mostly just the carbon cycle1. Glucose + 6O2  6CO2 + 6H2O + energyii. Aerobes1. Need oxygen2. Efficient decomposersa. Change most of carbon to CO2, which leaves little left for humusiii. Anaerobes1. Don’t use ovygen2. Fermentationa. Much less efficient, most C remains in soil as humusiv. Type of plant residue affects decomposition1. Fresh: proteins, fats, waxesa. High in nutrients2. Old/woody: cellulose, ligninsa. Low in nutrients3. Table