Yield is the top priority of every row-crop farmer. Many decisions are made based on how much yield increase a practise may provide. However, other considerations are also important.
For fifteen years my farm has planted corn in rows 20 inches apart, instead of the typical 30 inches for most of the US. This does not necessarily result in higher yield, but it is a more efficient use of fertilizer because there is less open space between the rows, allowing roots from plants in the row to access nutrients in the center 33% sooner. (In 30″ rows plants are 15″ from the center. In 20″ rows plants are 10″ from the center.) This advantage pairs well with my nitrogen plan of side dressing with 28% UAN (urea ammonium nitrate) applied when the corn is 6 to 14″ tall and has 3 to 6 leaf collars. Planned mid-season nitrogen applications give the crop this key nutrient just in time for when the plants need it the most and by not applying it all before planting we prevent early, excess nitrogen from running off in big rains, leaching into the subsoil, volatilizing into the air, and being converted by the urease enzyme.
My method of application is to spray this liquid nitrogen in streams between the corn rows. The sprayer makes quick work of this at 100 feet wide and 8 miles per hour; but it is tedious work keeping a big machine with 16.5″ wide tires between 20″ rows. Jonathan does a good job of it and puts in long hours in the peak season.
Every acre of every crop get sprayed with herbicide before planting. Corn gets sprayed again at about 6 weeks after planting and side-dressed at about the same time. Another big advantage of 20″ rows is that the corn plants will canopy much more quickly; that is, the leaves will entirely shade the middles between the rows, inhibiting the growth of weeds from lack of sunlight.
There is a window of about 4 weeks in which we can most efficiently apply both side-dressed nitrogen and post-emergence herbicide. Most herbicides work best in warmer temperatures and can even damage corn in cool, wet weather. This year we have been able to stay right on schedule with the number of acres that need to be covered, even though the cool weather has caused us to apply nitrogen instead of herbicide first.
It takes about 5 big days to spray herbicide on all our fields in 16 gallons per acre of water. But nitrogen takes longer because we apply 40-45 gallons per acre, depending on the quality of the soil, requiring us to travel more slowly and refill more often. At this point we are about half finished with each and the corn is not too tall, so we are in good time and are thankful to be this far along before yesterday’s 1″ rain.
Gentle rains are better for not washing away fertilizer, herbicide, and soil. So we pray for gentle, timely rains, all season long.