Saturday, 15 July 2006

Effects of Long-Term Nitrogen Fertilization and Crop Rotation on Soil Quality in Westcentral Illinois.

Sindhu Jagadamma1, Rattan Lal2, Robert G. Hoeft3, and Eric A. Adee3. (1) Ohio State Univ, School of Natural Resources, 2021 Coffey Road, 210 Kottman Hall, Columbus, OH 43210, (2) Carbon Management and Sequestration Centre, School of Environment and Natural Resources, FAES/OARDC, The Ohio State Univ, 2021 Coffey Rd., Columbus, OH 43210, (3) Univ of Illinois, Turner Hall, 1102 South Goodwin Avenue, Urbana, IL 61801

Some intensive agricultural practices result in decline of soil's inherent production potential. However, through long-term adoption of Recommended Management Practices (RMPs) such as judicious rates of Nitrogen (N) fertilization and different cropping systems, it is possible to enhance soil quality and sustainable crop productivity. These practices lead to increased crop residue production, which ultimately results in improved soil quality and sustainable agronomic productivity through increase in Soil Organic Carbon (SOC) pool and the associated properties. However, the benefits and risks associated with different RMPs often vary with soil types, climate and other site-specific cultivation practices. Therefore, the present study was conducted with the specific objectives to assess: (i) long-term impacts of N fertilization and cropping systems on selected soil quality indices such as soil structure, pH and ft, (ii) effects of N fertilization and cropping systems on corn and soybean residue yields, and (iii) to develop pedotransfer functions relating selected soil quality indices and crop residue yield with SOC concentrations and pools in the 0 to 30 cm depth. Soil samples were obtained during May 2004 from a long-term experiment (23-yrs) at the Northwestern Illinois Agricultural Research and Demonstration Center, Monmouth, IL. The predominant soil type is Muscatune silt loam (Fine-silty, mixed, superactive, mesic Aquic Argiudolls). The experimental design was split-split plot within a randomized complete block with three cropping systems [continuous corn (Zea mays) (CCC), and two rotation plots with corn and soybean (Glycine max) grown in alternate years (CSB and SBC respectively)] as the main plot, presence or absence of cover crop [oats (Avena sativa)] as sub plot, and five N rates [0 (N0), 70 (N1), 140 (N2), 210 (N3) and 280 (N4) kg N ha-1] in the split-split plot arrangement. Soil structural indices [Water Stable Aggregates (WSA) and Mean Weight Diameter (MWD)], soil pH and ft for 0-30 cm depth were determined using standard methods. Both WSA and MWD increased with increasing rates of N, with mean WSA values ranging from 47 to 54 % and MWD from 0.44 to 0.71 mm. The soils under continuous corn had more WSA (52.1%), which was 3% higher than that of corn-soybean rotation. The MWD of different cropping systems ranged from 0.50 to 0.65 mm, with the highest value corresponding to continuous corn system. Soil pH decreased with increasing N rate, and ranged from 6.2 for N4 level to 7.0 for N0 level. However, Soil ft was the lowest (0.49 m3 m-3) for N0 and highest (0.53 m3 m-3) for N4 treatment. Both WSA (R2=0.23) and MWD (R2=0.32) were positively correlated with SOC concentration. Aboveground corn and soybean biomass yield for 2004 were estimated using the grain yield and the harvest index. The harvest index values used in this estimation were 0.59 for corn and 0.57 for soybean. The corn residue (stover) production increased with increase in N rate. The stover returned to the soil ranged from 4.3 to 9.0 Mg ha-1 in continuous corn system and 6.9 to 8.7 Mg ha-1 in rotation corn system. Regression analysis indicated a significant positive relationship of stover yield with SOC pool, but not with SON pool. However, the soybean residue production was not influenced by N rates and had no significant relationship with either SOC or SON pool. Therefore, long-term continuous corn system coupled with judicious N fertilization has significant influence on improving soil quality and agronomic productivity through the improvement in SOC pool.

Back to 4.1B Role of Organic Matter for Soil Properties and Consequences for Environmental Functions - Poster
Back to WCSS

Back to The 18th World Congress of Soil Science (July 9-15, 2006)