Page 38 - 2019 Ag Mag

KMAland 2019
38 Integrated Pest Management

ISU, Conservation Groups Studying Extended Crop Rotations

Jason Johnson, partment, the study compares a 2-year
Public Affairs Specialist with NRCS in Des corn/soybean rotation, a 3-year corn/
Moines soybean/oat + red clover rotation, and a
F 4-year corn/soybean/oat + alfalfa/alfalfa

For the past several years the USDA-
rotation.
Natural Resources Conservation Service Eight years of findings indicate that
(NRCS) has promoted the adoption of diversifying the crop system and inte-
soil health improving conservation activi- grating livestock consistently boost pro-
ties. These principles include keeping the ductivity, profitability and environmental
soil covered, minimizing soil disturbance, health.
growing plants throughout the year, di- ISU research points to the following
versifying with extended crop rotations, important observations:
and incorporating livestock in the crop- Equivalent profits. Annual net re-
ping system. turns did not differ statistically among
Adding a third or more crop to a rota- the cropping systems. Numerically, the
tion to increase plant diversity has been 4-year rotation returned $413/acre, the
the most difficult principle for most Iowa 3-year rotation returned $409/acre, and
farmers to adopt. There are many reasons the 2-year rotation returned $384/acre.
for this, not least of which is finding mar- Better yields. Corn yields improved
kets for small grains or other potential 3 percent in a 3-year rotation and 4 per-
crops. cent in a 4-year rotation compared to a
For decades Iowa farmers included al- standard corn-soybean rotation. Soybean
falfa, oats, wheat, and other small grains yields improved 13 percent in a 3-year
in their corn and soybean rotation. By rotation and about 17 percent in a 4-year
growing a variety of plant species, past rotation.
generations more sustainably managed Improved soil health. Soils in extended
their soils. rotations tested higher for organic matter
Extended crop rotations help increase and microbial biomass and provide crops
nutrient cycling, better manage weeds, higher amounts of usable nitrogen.
disease and insects, reduce erosion, im- Reduced erosion potential. In a
prove infiltration, and allow more bio- 4-year rotation, estimated sheet and rill
logical activity in the soil. erosion fell about 35 percent compared
Can extended crop rotations to the corn-soybean rotation. In a 3-year
make a comeback? rotation, sheet and rill erosion fell about
An ongoing cropping system research 21 percent compared to a corn-soybean
study by Iowa State University indicates rotation.
that, with the right management, 3- and Reduced herbicide and N fertil-
4-year rotations can be just as profitable izer use. The 3- and 4-year rotations
as traditional corn-soybean rotations. used 88 percent and 92 percent less nitro-
Led by Dr. Matt Liebman, a professor gen fertilizer and 96 percent and 97 per-
in Iowa State University’s Agronomy De- cent less herbicide. Corn and soybeans