Soil Organic Carbon Trends Over 100 Years in the Morrow Plots

Abstract

Emerson D. Nafziger and Robert E. Dunker Agron. J. 103:261–267 (2011) Calculation errors in Table 5 led to several other errors in the above article, which appeared in an earlier issue of this volume year. Following are the paragraphs or excerpts affected along with the corrected paragraphs. Corrected versions of Table 5 and Figure 4 are also shown here. Soil organic carbon (SOC) levels in 1955 and changes in SOC levels from 1955 to 2008 in the Morrow Plots. The four points within each cropping system represent different soil amendment treatments. The authors greatly appreciate the assistance of Dr. Ken Olson, University of Illinois, who found the errors in the paper and made suggestions for correcting them. The authors regret the errors and apologize for any inconvenience this causes to the readers. In the Abstract, the following sentence: Over all rotations and treatments, SOC loss averaged only 1.1g C kg−1 from 1955 to 2008. should be replaced by the following: Over all rotations and treatments, SOC loss averaged 1.8 g C kg−1 (8%) from 1955 to 2008. In the last paragraph on page 262, the following sentence: Instead, SOC levels were projected for 2007–2008 using the Phase 4 samples that ended in 2003, by extending the prediction line to 2007.5. should be replaced by the following: Instead, SOC levels were projected for 2007–2008 using the Phase 4 samples that ended in 1993, by extending the prediction line to 2007.5. The first sentence of the first paragraph on page 265: Corn yields during the 1999 to 2009 period were substantially higher than those during the 1968 to 1998 period, especially in rotated corn; in continuous corn, unfertilized, MLP, and LNPK following LhiNPK treatments did not produce higher yields than did the treatments they succeeded (Table 5). should be replaced by the following: Corn yields during the 1999 to 2009 period were substantially higher than those during the 1968 to 1998 period, especially in rotated corn; in continuous corn, unfertilized, MLP, and LNPK following MLP treatments did not produce higher yields than did these treatments during the previous period (Table 5). The last paragraph at the bottom of the first column on page 266: While limited sampling did not allow us to examine trends in SOC during the most recent period (1999–2009), the SOC values predicted by the trend for the three decades before 1999 and those found by averaging data from 2007 and 2008 samples showed no consistent differences (Table 5). Differences in SOC over the entire period from 1955 to 2007–2008 ranged from a loss of 4.6 g C kg−1 to a gain of 3.0 g C kg−1, with an average loss of 1.1 g C kg−1. Unfertilized plots lost about 1 g C kg−1 in all three rotations, LNPK treatments tended to gain SOC, and MLP treatment lost an average of more than 3 g C kg−1 over this period (Table 5). While it thus appears that soil amendment treatments have had some effect on SOC changes from the mid-1950s until now, the inverse relationship between SOC levels at the start of this period and changes in SOC levels during this period (Fig. 4), and the lack of correlation between current SOC levels and recent corn yields (Table 5) demonstrate that causes of SOC changes are complex, and may not be closely related to crop management. should be replaced with the following: While limited sampling did not allow us to examine trends in SOC during the most recent period (1999–2009), the SOC values predicted by the trend for the three decades before 1999 and those found by averaging data from 2007 and 2008 samples showed no consistent differences (Table 5). Differences in SOC over the entire period from 1955 to 2007–2008 ranged from a loss of 6.0 g C kg−1 to a gain of 1.9 g C kg−1, with an average loss of 1.8 g C kg−1, or about 8% of the SOC present in 1955. Unfertilized plots lost no SOC in continuous corn, but lost about 1 g C kg−1 in the other rotations. The only treatments that gained SOC over this period were the LNPK treatments in continuous corn and in corn-oat hay, while MLP treatment lost an average of 4.2 g C kg-1over this period (Table 5). While it thus appears that soil amendment treatments have had some effect on SOC changes from the mid-1950s until now, the inverse relationship between SOC levels at the start of this period and changes in SOC levels during this period (Fig. 4), and the lack of correlation between current SOC levels and recent corn yields (Table 5) demonstrate that causes of SOC changes are complex, and may not be closely related to crop management. The first paragraph on page 267: Changes in SOC levels in the Morrow Plots from 1955 to 2008 were relatively small in most cases, and were not very consistently related to rotation and treatment. Losses were largest in the corn–oat (to 1967)/corn–soybean (1968 and after) rotation, lowest in continuous corn, and intermediate in the corn–oat–hay rotation. Plots with moderate additions of nutrients (MLP) consistently lost SOC, unfertilized plots lost small amounts of SOC, and chemical fertilizer additions resulted in some increases and some decreases in SOC. should be replaced with the following: Changes in SOC levels in the Morrow Plots from 1955 to 2008 ranged from small to substantial, with the limited-nutrient (MLP) plots losing more than 15% of their SOC at the beginning of this period. Losses were largest in the corn–oat (to 1967)/corn–soybean (1968 and after) rotation, lowest in continuous corn, and intermediate in the corn–oat–hay rotation. Plots with moderate additions of nutrients (MLP) consistently lost SOC, unfertilized plots lost small amounts of SOC, and chemical fertilizer additions resulted in some increases and some decreases in SOC. The following section of the second sentence in the second paragraph on page 267: This possibility supported by the finding that a 2007 measurement of electrical conductivity, which incorporates SOC… should be replaced with the following: This possibility is supported by the finding that a 2007 measurement of electrical conductivity, which incorporates SOC… The corrected versions of Table 5 and Fig. 4 are shown below.