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A long-term study by Ray Lamond and Chuck Rice, K-State agronomists, at the North Agronomy Farm in Manhattan has compared the effect of tillage systems (no-till or conventional tillage), nitrogen sources (manure or commercial fertilizer), and nitrogen rates (0, 75, and 150 lbs N per acre) in a continuous corn system under dryland conditions. Data has been taken on carbon sequestration rates, crop yields, and net returns from the different management practices.


The 1991-1999 data from that study has been analyzed by Jeff Williams, Department of Agricultural Economics; Richard Nelson, Extension Energy Service; and agricultural economics graduate student Dustin Pendell. The economists wanted to find out how much money producers would have to get for carbon credits in order to encourage them to switch to either no-till or use of manure in a continuous corn production system in northeast Kansas. The authors summarize the results as follows:


1. Gross carbon (C) sequestration rates were highest for no-till, manure, and the highest N rates. This analysis began by comparing the soil organic C levels in the soil at the 6-inch depth under the different treatments.


Did no-till have higher rates of C sequestration than conventional tillage? Yes. Comparing the two tillage systems at the fertilizer rate of 150 lbs N per acre, the no-till treatments had an increase compared to conventional tillage.


* No-till sequestered 0.198 tons C/acre/year more than conventional tillage in manure plots.

* No-till sequestered a gross amount of 0.059 tons C/acre/year more than conventional tillage in ammonium nitrate plots.


Did N source affect C sequestration? Yes. Comparing the manure with commercial fertilizer (ammonium nitrate) treatments under the no-till system, the manure resulted in more C sequestration:


* No-till with manure had the highest gross C sequestration rate: 1.24 tons C/acre/year.

* No-till with ammonium nitrate was next at 1.09 tons C/acre/year.


2. Net C sequestration rates were then calculated. This was done by starting with the gross soil C sequestration rates and subtracting out the amount of carbon dioxide (CO2) released through the use and manufacture of inputs for each management practice. Carbon releases include the amount of fuel combustion used in field operations, the energy consumed in manufacturing inputs, and the energy released from the raw material of the inputs. The scientists found that:


* No-till had lower CO2 emissions from production inputs than conventional tillage.

* The use of manure had lower CO2 emissions than the use of ammonium nitrate.


As a result, no-till and manure treatments had higher net C sequestration rates, as well as higher gross C sequestration rates, than conventional tillage and ammonium nitrate treatments.


* No-till with manure had the highest net C sequestration rate, at 1.21 tons C/acre/year.

* No-till with ammonium nitrate had the next highest net C sequestration rate, at 1.03 tons C/acre/year.


3. Net returns for no-till were higher than returns from conventional tillage because of lower costs. Corn yields were about the same for no-till and conventional tillage. As a result, payments for carbon credits would not be needed in order to encourage producers in northeast Kansas to switch from conventional tillage to no-till in a dryland, continuous corn system


4. Net returns were lower for plots fertilized with manure than for plots fertilized with ammonium nitrate because of lower yield in the manure plots. As a result, payments of $27.22 per acre for carbon credits would be necessary to encourage producers to switch from ammonium nitrate fertilizer to manure.


For more information, contact Jeff Williams at jwilliam@agecon.ksu.edu



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