Nitrogen fertilization is essential in most cropping systems to optimize crop yields and economic returns. Nitrogen fertilization generally increases N 2 O emissions from cropping systems, with a positive association between emission and N rate (Archer and Halvorson,

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Controlled release nitrogen (N) fertilizers have been commonly used in horticultural applications such as turf grasses and container-grown woody perennials. Agrium, a major N manufacturer in North and South America, is developing a low-cost controlled release urea (CRU) product for use in field crops such as grain corn, canola, wheat, and other small grain cereals. From 1998 to 2000, 11 field trials were conducted across western Canada to determine if seed-placed CRU could maintain crop yields and increase grain N and N use efficiency when compared to the practice of side-banding of urea N fertilizer. CRU was designed to release timely and adequate, but not excessive, amounts of N to the crop. Crop uptake of N from seed-placed CRU was sufficient to provide yields similar to those of side-banded urea N. Grain N concentrations of the CRU treatments were higher, on average, than those from side-banded urea, resulting in 4.2% higher N use efficiency across the entire N application range from 25 to 100 kg ha-1. Higher levels of removal of N in grain from CRU compared to side-banded urea can result in less residual N remaining in the soil, and limit the possibility of N losses due to denitrification and leaching.

Rising fertilizer costs and environmental concerns have heightened the need to improve N management in furrow-irrigated sugarbeet (Beta vulgaris L.) production. A study was conducted at two Wyoming locations to compare the effect of different preplant N placement strategies on yield, quality, and N use efficiency (NUE). Nitrogen was applied at rates from 0 to 358 kg ha 21 using three different placement strategies: broadcast and incorporated (BI), knife-banded (KB) 18 cm from the seed row, or point-injected (PI) 8 cm from the seed row. Placement had no consistent effect on root sucrose content. Point injection produced the greatest maximum predicted yield (Y MAX ) in five of six N responsive site-years with an average advantage of 603 and 975 kg ha 21 sucrose compared to BI and KB, respectively. The amount of N required for maximum sucrose yield ranged from about 10 to 100 kg N ha 21 less for PI than for other placement methods. For site-years where a response to N occurred, NUE was highest with PI, intermediate with KB (19% less than PI), and lowest with BI (28% less than PI). The advantage of PI, which placed N closer to the seed row than the other methods, was attributed to less leaching and greater uptake of N during early growth stages when the sugarbeet has little lateral root development. It was concluded that PI is an effective tool for maintaining high N concentration in the root zone for optimum early vegetative growth at lower N rates, thus improving NUE in sugarbeet production.

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