University of Nebraska-Lincoln Extension

Furnas County, 308-268-3105

January 16, 2009

FOR IMMEDIATE RELEASE

Last week I discussed the benefits of crop rotation vs continuous cropping in winter wheat. This week I will discuss these same benefits in corn production. Keep in mind the benefits of crop rotation that were outlined last week. They include:

Despite the many benefits of crop rotation, growers are occasionally confronted with situations where for one reason or another they would like to grow the same crop in two consecutive years in the same field, that is, continuous cropping. Economics can often be the incentive for ignoring generally accepted agronomic recommendations for crop rotation, although other reasons such as machinery or labor constraints can also play a role.

Table 1 has the yields of corn, soybeans and oats as affected by crop rotation and nitrogen fertilization for corn in a report by Professor Antonio P. Mallarino et al. at Iowa State University, Northern Research and Demonstration Farm near Kanawha, Iowa. This study began in 1984.

The nitrogen fertilizer was granulated urea incorporated into the soil by plowing or field cultivating in the spring or fall for continuous corn and in the spring for the other rotations. Oats were always undersown with alfalfa. No hay was harvested after harvesting oats, but three harvests were made in other years. Hay yields for rotation 5 (one year) and rotation 6 (two years) are not shown.

In comparing the average continuous corn yield with fall and spring applied nitrogen (rotations 1 and 7) with corn yields in the corn/soybean rotation (rotation 3) over the recent 4 years, the benefit of including soybeans in the rotation was 8 bushels/acre (193 vs. 201) at the highest nitrogen rates and 37 bushels/acre (90 vs. 127) at the lowest nitrogen rate.

The corn yields during the recent 4 years in a corn/soybean rotation maxed out at 201 bushels/acre with 160 pounds of nitrogen in comparison with 195 bushels/acre for spring applied nitrogen at 240 pounds in continuous corn. Including alfalfa and oats with and without soybean further increased corn yields.

In an article in 2008 by Mahdi Al-Kaisi et al. (Iowa State Extension) featuring a corn following corn rotation they had the following comments:

Yields - what can we expect?

First remember why we rotate corn and soybean: crop rotation usually results in maximum yields of both crops. In the very best of years, corn following corn will yield as well as corn following soybean. In the worst of years lower yields occur when corn follows corn. These are years with climatic stresses - notably dry years and those with wet springs.

Over the last eight years, Iowa corn yields following corn have ranged from almost the same to 27 percent less than yield of corn following soybeans. The eight-year average is 14 percent less (Table 2). Crop rotation is an important tool for us to maximize yield and profitability. Planting corn after corn usually results in reduced yield which results from a less than ideal growing environment.

Professor Antonio P. Mallarino etal at Iowa State University, Northern Research and Demonstration farm near Kanawha, Iowa.

J.E. Sawyer and D.W. Barker, Iowa State University

The Furnas County 4-H Council will meet beginning at 7:30 p.m., Monday, January 26, 2009 at the Courthouse in Beaver City.