Journal
CANADIAN JOURNAL OF SOIL SCIENCE
Volume 81, Issue 2, Pages 139-148Publisher
AGRICULTURAL INST CANADA
DOI: 10.4141/S00-035
Keywords
C sequestration; crop rotation; fertilizer; grain yields; total N; tillage
Categories
Ask authors/readers for more resources
Society's desire to sequester C in soils, thereby reducing the net loss of CO2 (a greenhouse gas) to the atmosphere, is well known. It is also accepted that the choice of appropriate agricultural management practices adopted by producers will affect this goal. However, quantification of the extent and rate at which it can be achieved is uncertain. A crop rotation experiment that was initiated in 1957 on a thin Black chernozemic clay soil at Indian Head, Saskatchewan, was managed using conventional tillage until changed to zero tillage in 1990. Soil was sampled (0- to 7.5- and 7.5- to 15-cm depths) in May 1987 and 1997 to determine the effects of treatments on soil organic C (SOC) and total N. The rotations were: fallow-wheat (Triticum aestivum L.) (F-W), F-W-W, continuous wheat (Cont W), legume green manure (GM)-W-W, and F-W-W-hay (legume-grass)-hay-hay (F-W-W-H-H-H). The monoculture cereal rotations were either fertilized with N and P based on soil tests or unfertilized, while the legume systems were both unfertilized. There was also a F-W-W (N+P) treatment in which the straw was baled and removed. When the experiment was changed to zero tillage management in 1990, the fertilizer protocol was changed to satisfy the moist soil criteria. Consequently, higher rates of N and P were added thereafter to the fallow crop, resulting in a positive yield response of wheat,grown on fallow, where before there was no response to fertilizer. Over the 10-yr period (1987-1997) fertilized soil gained C and N, but unfertilized soil did not. For example fertilized F-W, F-W-W and Cent W gained about 4, 5 and 2 Mg C ha(-1) in the 10-yr period. During this period, C emissions from manufacture and transportation of N fertilizer was 0.28, 0.53 and 0.90. Mg ha(-1) for these three rotations, respectively. These results suggest that without adequate fertility, conversion to zero tillage may not always result in an increase in soil C or N. By 1997, fertilizer increased soil C and N in F-W-W and Cent W, and soil C and N were greater in F-W-W-H-H-H than in GM-W-W and lowest in F-W-W tall unfertilized). Straw removal had no significant effect on C or N. The analysis showed that C inputs from crop residues was the main factor influencing SOC changes.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available