Title page for ETD etd-02102008-174038

Type of Document Dissertation
Author Spargo, John T
Author's Email Address jspargo@vt.edu
URN etd-02102008-174038
Title Continuous No-till Management: Implications for Soil Quality, Carbon Sequestration, and Nitrogen Conservation
Degree PhD
Department Crop and Soil Environmental Sciences
Advisory Committee
Advisor Name Title
Alley, Marcus M. Committee Chair
Evanylo, Gregory K. Committee Member
Follett, Ronald F. Committee Member
Phillips, Steven B. Committee Member
Zelazny, Lucian W. Committee Member
  • Nitrogen use efficiency
  • carbon trading
  • nutrient trading
  • soil organic matter
Date of Defense 2008-02-01
Availability unrestricted
No-till management for agronomic crop production is recognized as an effective practice to regain a portion of soil organic matter lost following decades of cultivation. Increasing soil organic matter sequesters C, conserves organic N and concomitantly improves soil quality. Objectives of this research were to: i) quantify C sequestration rate and N conservation with duration of continuous no-till; ii) measure C stratification with continuous no-till as an indicator of soil quality; and iii) evaluate the Illinois soil N test (ISNT) for its value to predict fertilizer N needs of corn in Virginia.

Objectives i and ii were achieved by collecting soil samples from 63 production fields in the Virginia Coastal Plain that were managed using continuous no-till from 0 to 14 yrs. No-till management resulted in sequestration of 0.308 ± 0.280 Mg C ha-1 yr-1 and conservation of 22.2 ± 21.2 kg N ha-1 yr-1 (0-15 cm). The C stratification ratio (0-2.5 cm: 7.5-15 cm) increased with increasing duration of continuous no-till (0.133 ± 0.056 yr-1) due to the accumulation of organic matter at the soil surface indicating improved soil quality with continuous no-till management.

Objective iii was addressed by conducting 29 on-farm fertilizer N response trials in major corn producing areas of Virginia with the duration of continuous no-till management ranging from 0 to 25 yrs. The ISNT values were significantly related to yield without fertilizer N (r2 = 0.57; p<0.001) and relative yield (r2 = 0.64; p<0.0001). We also found that the ISNT extracted a relatively consistent percentage of total soil N (16.3 ± 0.73 %) suggesting it is a poor indicator of labile N. Total soil N values did almost as well as the ISNT in predicting yield without fertilizer N (r2 = 0.53; p = 0.0002), and equally well predicting relative yield (r2 = 0.64; p<0.0001). Results do not suggest the ISNT is useful for measuring mineralizalbe N or improving fertilizer N recommendations in Virginia cropping systems.

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