Integration of Conservation Tillage, Animal Manures, and Cultural Pest Control in Corn
Three farm technologies contribute greatly to the farm, social, and environmental cost of
agricultural production: 1) tillage, which consumes large amounts of energy and leaves the soil
open to erosion; 2) anhydrous ammonia, which embodies large amounts of energy and can
pollute water resources; 3) pesticides, which disrupt natural controls and are a human health
hazard. Corn production in the rolling topography and karst formations of southeastern
Minnesota highlights these costs. In this area conventional practices include chisel plow for
tillage, “disposal” of farm yard manures (hog and dairy) on alfalfa and fertilized corn land in the
fall and spring, widespread use of herbicides, and frequent use of corn rootworm insecticide on
second and third year corn.
The overall goal of this project is to explore, evaluate, and develop integrated low-input
management systems for corn production in southeastern Minnesota. Systems that will be
evaluated are ones that reduce tillage, minimize use of synthetic fertilizers, and reduce pesticide
use. One such potential system is ridge-tilled corn fertilized with manures. However, there are
three areas of questions about this system that will need to be answered.
1) Production related questions: a) What effects of manures on crop yield carry over form one
year to the next in ridge-till corn? b) Given these carry-over effects, what is the relation between
rates of manure application and corn production?
2) Soil and nitrogen questions: a) What is the rate of NO3 leaching in the ridge-tilled corn from
manures with different frequencies of application and how do they compare with synthetic
fertilizers? b) What manure treatments result in higher levels of soil organic matter and large
pools of potentially mineralizable N?
3) Pest control questions: a) Do reasonable rates of applications of manure affect survival of
corn rootworms or attack by European corn borer and do these relations change with tillage? b)
Do manures and tillage affect weed populations?
Experiments were conducted on farms in southeastern Minnesota.
Fertilization with synthetic nitrogen gave about 25 bu/acre more yield, but also gave 3-8 fold
greater nitrate leaching. There were no differences in rootworm injury. There was no difference
in yield among tillages, but ridge-till gave 1.5 – 2.0 fold greater nitrate leaching. Although data
from more years would need to be collected to substantiate these trends, the current data suggest
that chisel plow is superior to ridge-till at this site because it presents less of a threat to ground