|Stevens, William - Bart|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2007
Publication Date: 9/1/2007
Citation: Stevens, W.B., Blaylock, A.D., Hopkins, B.G., Ellsworth, J.W., Krall, J.M. 2007. Sugarbeet Yield and Nitrogen Use Efficiency with Pre-plant Broadcast, Banded, or Point-Injected Nitrogen Application. Agronomy Journal. 99:1252-1259. Interpretive Summary: 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 pre-plant N placement strategies on yield, quality, and N use efficiency (NUE). The findings of this study agree with those of previous research in support of the hypothesis that precision placement of N in close proximity to the seed row increases NUE by enhancing early N uptake and reducing the potential for N leaching. We conclude that (i) pre-plant PI application enhances sugarbeet root yield while having little effect on root sucrose content and (ii) placement of pre-plant fertilizer N in close proximity to the seed row improves NUE because N is more readily accessible for early uptake when sugarbeet yield is being determined and is less susceptible to leaching compared to broadcast application. Of the three application methods evaluated in this study, PI generally resulted in the highest yield and NUE. Knife-banding also improved NUE compared to BI, but resulted in lower overall root and sucrose yield. Because of increased productivity and more efficient N use, economic calculations based on the Powell data from this study predict an economic advantage for the PI. In spite of considerable equipment costs for the spoke-wheel injector, Van Tassell and others estimated that net profits were about $165 ha-1 more for PI than for BI and $232 ha-1 more than for KB. This study demonstrates the advantages of precision N placement in a furrow-irrigated system. A producer can apply N in any number of ways, but the spoke-wheel injector increases the options for in-row applications. Results show that PI in furrow-irrigated sugarbeet can improve productivity, NUE and grower profits by providing a means for more efficient N application. These results reflect only pre-plant N applications, but it is reasonable to expect that benefits to precision placement will be observed with post-emergence applications as well. It is likely that NUE and productivity would be further enhanced with a split application using precision placement methods for both pre-plant and post-emergence applications, especially where early season furrow irrigation is practiced. This approach would provide a portion of the fertilizer N during seedling development while the remainder is applied just prior to the midseason rapid uptake period.
Technical Abstract: 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 pre-plant N placement strategies on yield, quality, and N use efficiency (NUE). Nitrogen was applied at rates from 0 to 358 kg ha-1 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 (YMAX) in five of six N responsive site-years with an average advantage of 603 and 975 kg ha-1 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-1 less for PI than for other placement methods. In 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 closest to the seed row, 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.