Effect of moisture regime on recovery and utilization of fertilizer n applied to corn

Environmental and economic concerns have resulted in renewed interest in the potential for N loss under various climatic conditions. Experiments were conducted over a three-year period at three locations in Illinois to evaluate the effects of soil type and soil moisture conditions on the fate of fertilizer N during the growing season. At each location, a factorial arrangement of four N rates (0, 100, 150, and 200 lb N/acre) and three soil moisture levels (ambient, ambient + 4 in. over a 3-d period, and ambient + 6 in. over an 8-d period) was established with corn (Zea mays L.). Isotopic ¹⁵N was used for the 150 lb N/acre plots. After the moisture treatments had been imposed, moisture levels were allowed to return to conditions drier than 0.33 bar and plots were split with one half receiving a supplemental application of 50 lb N/acre. Regression equations relating total recovered N and plant N uptake to soil moisture condition and N application were developed for each site. Fertilizer N recovery on a Drummer sicl (fine-silty, mixed, mesic Typic Haplaquoll) averaged 50 and 44% at the end of the growing season with the application of 4- and 6-in. excess water, respectively, compared to 83% with the ambient treatment. Fertilizer N recoveries of 61% with excess water application compared to 88% with ambient moisture were observed on a Cisne sil (fine, montmorillonitic, mesic Mollic Albaqualf). Excessive losses of fertilizer N were observed on a Plainfield soil (mixed, mesic Typic Udipsamment). Less than 25% of the N was recovered with the ambient treatment, with even lower recoveries (8-13%) associated with the application of excess water. Denitrification appeared to be the primary loss mechanism on the Cisne and Drummer soils, whereas leaching was the primary loss mechanism on the Plainfield soil.