Characterization of Corn Products for Their Response to Nitrogen Fertilization
Nitrogen fertilization is an integral part of corn production and is partly responsible for some of the drastic yield increases in corn production. Nitrogen is also the focus of a lot of the research in soil fertility and crop nutrition, with emphasis on finding the right rate, timing, source, and placement.
It is important to understand how corn products respond to nitrogen fertilization. Concerns with environmental safety have mandated provisions of just the right amount of nitrogen for crop use to minimize nitrogen losses to the water system. This has led to the development of such technologies as the Nitrogen Advisor from Climate FieldView™ to help farmers monitor and maintain the right nitrogen status throughout the growing season. Knowing a corn product’s demand for nitrogen may also help save production costs in the face of dwindling farm profit margins.
The objective of this study was to characterize corn products for their sensitivity to different nitrogen rates. Rates were selected to induce both nitrogen stress and luxury consumption.
Research Site Details
The nitrogen rates tested were:
— Low – 30 lb/acre for the corn-soybean rotations or 50 lb/acre for the corn-corn rotation
— Medium – 160 lb/acre (Huxley only)
— High – 230 lb/acre
All nitrogen applications were made before planting.
The trial was carried out in 30-inch row spacing, with four rows per treatment, and 45 ft long plots with two replications.
Weed management consisted of a pre- and post-emergence program.
Understanding the Results
There was clear indication of nitrogen extremes as shown in Figure 1. Plants in the low rate treatment showed chlorotic symptoms due to nitrogen stress, whereas those in the other treatments did not.
At all three locations, grain yields increased with increasing nitrogen rate such that the low treatment had the lowest yields and the high treatment had the highest yields, except for five products at Huxley in which the medium rate out-yielded the high rate. Also, at Marble Rock, the low rate out-yielded the high rate in DKC51-38RIB brand blend (Figure 2–4).
Even though yields were highest at the Victor location, the biggest nitrogen response was observed at Huxley, with an average of a 124 bu/acre yield difference between the low and high rates, followed by Victor with a 49 bu/acre difference and then Marble Rock with a 46 bu/acre difference.
The medium nitrogen rate at Huxley helped to identify products with very different nitrogen requirements, such as DKC57-97RIB and DKC62-20RIB brand blends (Figure 2).
What Does This Mean for Your Farm?
A corn plant’s yield response to nitrogen is a complex phenomenon and is substantially impacted by the weather during the growing season, the soil type, and the inherent soil fertility.
Wet conditions in May and June at the Huxley location may have led to substantial nitrogen loss, which can increase stress on the plants. This may explain, in part, the very low yields observed at the low nitrogen rate treatment.
The Victor location, on the other hand, presented a high inherent soil fertility which produced an average of 233 bu/acre with only 50 lb/acre of nitrogen. Such a field needs to be sustainably managed to avoid nitrogen loss to the water system.
At the current market trend of $0.23/lb of nitrogen and $3.75/bu for corn, a minimum of 12.3 bu/acre is required to pay for the difference between the low and high nitrogen rates. Thus, all but one product, DKC51-38RIB brand blend at Marble Rock, were profitable at all locations. A minimum of 4.3 bu/acre is required between the medium and high rates at the Huxley location.
Corn products respond differently to farm inputs and they should be tested on a small scale before they are deployed for the whole farm.