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NH 4 :NO 3 Ratio

NH 4 :NO 3 Ratio. Jessica G. Davis Jessica.Davis@Colostate.edu. It’s ammonium (NH 4 + ), NOT ammonia [NH 3 (gas)]. 1) How are NH 4 + and NO 3 - measured?. 2 M KCl extraction Colorimetric analysis. 2) How does Composting Affect the NH 4 :NO 3 Ratio?. We start with Manure Nitrogen

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NH 4 :NO 3 Ratio

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  1. NH4:NO3 Ratio Jessica G. Davis Jessica.Davis@Colostate.edu It’s ammonium (NH4+), NOT ammonia [NH3(gas)]

  2. 1) How are NH4+ and NO3-measured? • 2 M KCl extraction • Colorimetric analysis

  3. 2) How does Composting Affect the NH4:NO3 Ratio? • We start with Manure Nitrogen • Organic N • 20-80% • NO3-N • very little • NH4-N • 20-80%

  4. NH4-N Volatilizes as NH3 Immobilizes into organic N Could nitrify to NO3 NO3-N Denitrification to N2O (if it’s too wet) Could leach Organic N Mineralizes to NH4-N and then nitrifies to NO3-N OVERALL Volatilization and immobilization of NH4 in first 60 days followed by mineralization and nitrification The NH4:NO3 ratio drops during composting. 2) How does Composting Affect the NH4:NO3 Ratio?

  5. Classification System

  6. Length of Composting Period NH4 concentration decreases in first 60 days NO3 increases later Feedstock Selection Feedstocks with lower initial NH4 levels result in composts with higher NO3 levels Choosing feedstocks with lower NH4 levels could be helpful e.g., aged manure 3) How does Compost Management Affect the NH4:NO3 Ratio?

  7. 4) How does NH4:NO3 Affect Plants and Soil? • Plants can take up both NH4 and NO3 • BUT plants adapted to acid soils prefer NH4 • AND plants adapted to alkaline soils prefer NO3

  8. Some Plant Problems • Too much NH4, like in a fresh poultry manure, can burn plants • Too much NO3 late in the season can damage crop quality

  9. Excess NH4+ TroubleSome NH4 improves growth, BUT too much… • Inhibits uptake of other cations (positively charged nutrients) • Ca • Mg • K This is especially detrimental when pH > 7.5 • Diminishes root numbers and length • NH4+ uptake reduces soil pH in the rhizosphere (not in the bulk soil)

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