Location: Sugarcane ResearchTitle: Nitrogen management research in Louisiana sugarcane production systems
|TUBANA, BRENDA - LSU Agcenter|
|VIATOR, HOWARD - LSU Agcenter|
Submitted to: Sugar Bulletin
Publication Type: Trade Journal
Publication Acceptance Date: 4/1/2015
Publication Date: 4/1/2015
Citation: Tubana, B.S., Johnson, R.M., Viator, H.P. 2015. Nitrogen management research in Louisiana sugarcane production systems. Sugar Bulletin. 93(7):17-18.
Technical Abstract: Nitrogen (N) is the most limiting nutrient in sugarcane production and is considered the biggest expense among fertilizer inputs. Nitrogen fertilizer remained expensive after a drastic price increase in 2008. The average cost of a ton of N as urea-ammonium nitrate (UAN) solution from 2003 to 2007 was $213/ton then went up $410/ ton in 2008. Implementation of on-a-need-basis application method can improve N fertilizer use efficiency in sugarcane production. Current Louisiana State University recommendations specify nitrogen application rates between 60 and 120 lbs N/ac. These recommendations were established from many years of field response trials and are further refined based on cane age and soil texture. The advent of technology has allowed the crop production industry to use optical sensors and fully automated laboratory instrumentation for quick or instant acquisition of field information that growers can use as N decision tools. This project was conducted to evaluate the performance of sensor and soil nitrate as tools for projecting sugarcane N requirement. The yields of sugarcane applied with UAN solution and granular N fertilizer were also evaluated. Three large-scale field demonstration plots were established in 2014, one at the LSU AgCenter Sugar Research Station and on two producers' field in Donaldsonville, LA. The treatments included farmer's standard practice (T1), and N recommendation methods based on soil nitrate test + sugar yield goal (T2), and optical sensor readings (T3). The results from the field demonstration plots showed that T2 and T3 consistently recommended lower N rate averaging only 55 and 58 lbs/acre compared with Tl at 120 lbs/acre. There were no evident differences on cane tonnage among the N recommendation methods for all three sites however, the lower theoretical recoverable sugar (TRS) obtained from T3 plots resulted in significantly lower sugar yield at two sites lowering net return from N fertilizer by an average of $70/acre. On the other hand, one site attained a $223/acre higher net return compared with Tl due to higher sugar yield and large saving from applying lesser N fertilizer. For T2, positive net return was observed for two sites only (average of $16/ acre). The field study on N source effect showed that only TRS was significantly different among the treatments (P<0.10). The average TRS of sugarcane applied with urea (204 lbs/ ton) and ammonium nitrate (201 lbs/ton) was lower than that of UAN knife-in (213 lbs/ ton) and dribble (218 lbs/ton); this was more evident in plots which received 80 and 120 lbs N/acre. The standard error among treatment means suggest that the highest cane tonnage and sugar yield were achieved using knife-in UAN and ammonium nitrate as source with the former requiring lesser amount of N to attain the observed highest yield. This adds veracity that UAN as a more effective source of N fertilizer in Louisiana sugarcane production system. The use of sensor and soil nitrate as N decision tools remains viable for the sugarcane industry in Louisiana. Work is under way to transform these decision tools into farm operational setting.