Agriculture Reference
In-Depth Information
in 1996 and most recently conducted in 2010—offers online data summaries for
tracking adoption of crop production practices (ERS 2012c)
Although over 80% of U.S. row crops are grown in rotations (Wallander 2013),
there has been a trend toward simplified crop rotations that focus on the most prof-
itable crops. In 1996-2006, the most recent decade for which preceding crop data
are available, the corn-soybean rotation was increasingly adopted at the expense of
both continuous corn and rotations with small grains. Over that period, corn follow-
ing small grains dropped from 10% to less than 8% of U.S. corn acreage. By con-
trast, corn following soybean expanded from 54 to 60% of corn area. That pattern
appears to have continued in the early 2000s, as corn and soybean displaced over
10 million acres of wheat and hay, in response to market price signals (Jekanowski
and Vocke 2013).
Winter cover crops such as clover and rye are planted in the fall following har-
vest and plowed under prior to the following summer's primary crop. Winter cover
crops are more common after soybean than after corn, mainly due to an earlier soy-
bean harvest that provides a longer planting time in the fall. In 1997 winter cover
crops were grown on 1% of U.S. corn land and 5% of U.S. soybean land (Padgitt
et al. 2000). As of 2010, 3 to 7% of U.S. farms planted cover crops, but the area
remained small, roughly 1% of cropland (Wallander 2013).
By contrast, acreage under conservation tillage increased from 26 to 41%
between 1990 and 2004 (Sandretto and Payne 2006). This is likely linked to the
availability and rapid adoption of herbicide-tolerant crop varieties that simplify her-
bicide decisions and reduce the need for tillage to control weeds. Between 1996 and
2006, the percentage of U.S. soybean acreage planted with genetically modified,
herbicide-resistant seed rose from 7 to 97% (ERS 2012c). Over that same period,
the mean number of tillage operations in soybean fell from three to one, and mean
number of herbicide applications from three to two.
Corn farmers consistently applied nitrogen fertilizer to 96-99% of planted acres
during 1996-2010 at annual average rates that grew from 151 to 160 kg N ha
−1
yr
−1
from 2000 to 2010 (134 to 143 lb acre
−1
yr
−1
) (ERS 2012c). Over that same period,
the percentage of corn land area that underwent soil nitrogen testing rose from 21%
in 1996 to 28% in 2005, and then fell back to 22% in 2010. Plant tissue nutrient
testing crept upward from 2 to 4% of planted area. Using the same USDA survey
data, Ribaudo et al. (2011) found that only 35% of U.S. corn land met best manage-
ment practice norms for rate, timing, and method of nitrogen fertilizer application
in 2006.
In summary, the adoption of conservation technologies like those used at KBS
LTER has occurred in the case of conservation tillage practices and (to a lesser
extent) small grains in the crop rotation, but not for cover crops or reduced nitrogen
rates (Table 13.1). Given the documented ecosystem service benefits from all these
technologies, it is important to ask what impedes adoption of the full set of them.
Attitudes toward Adopting Conservation Practices
Direct questioning of farmers can shed light on the motives behind their adoption
patterns. We gathered both qualitative and quantitative data on how Michigan corn
