ARS | Publication request: Nitrogen Availability for Sugarbeet affected by Tillage System and Sprinkler Irrigation Method

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 16, 2010
Publication Date: November 1, 2010
Repository URL: http://hdl.handle.net/10113/50546
Citation: Stevens, W.B., Evans, R.G., Jabro, J.D., Iversen, W.M. 2010. Nitrogen Availability for Sugarbeet affected by Tillage System and Sprinkler Irrigation Method. Agronomy Journal. 102:1745-1752.

Interpretive Summary: High fuel costs, damage to seedlings caused by wind-blown soil, and declining soil quality have increased interest in reduced tillage practices for sugarbeet. Strip tillage (ST) is a reduced tillage system that can reduce fuel and labor costs of sugarbeet (Beta vulgaris L.) production. Many shank-type ST implements band fertilizer below the seed without incorporating crop residue into the soil, potentially affecting N availability. Sprinkler irrigation method may also affect N availability due to its influence on water and NO3-N movement in soil. A field study was conducted at Sidney, MT to determine if petiole NO3-N concentration and soil available (i.e. mineral) N distribution differ under (1) conventional tillage (CT) and ST systems and (2) mid-level spray application (MESA) and low energy precision application (LEPA) irrigation methods. Petiole NO3-N concentration was lower for ST than CT for at least one sample date in two of three years and in-season available N in the top 45 cm of soil was lower with ST than with CT, particularly at sampling dates 80 DAP and earlier, in all three years. Post-harvest residual NO3-N was about 10% less with ST than with CT. Despite these differences, sugarbeet root yield and quality were similar for the two tillage systems. Plant N status and soil mineral N concentration were similar for MESA and LEPA irrigation methods. The only significant difference observed was a 10% increase in in-season soil mineral N with LEPA compared to MESA. This may be due in part to a possible reduction in NO3 leaching when LEPA, in which irrigation water is applied between alternating crop rows, is combined with strip tillage, where N is banded directly underneath the crop row. With the combination of these two systems N fertilizer is spatially separated from the downward percolating irrigation water. It was concluded that, while some differences in plant N status and soil N content were observed, these differences were not sufficient in magnitude or frequency to justify altering N application rate based on the tillage systems or irrigation methods evaluated in this study. In particular, N application rate should not be reduced with ST assuming that banding N will lead to higher N-use efficiency.

Technical Abstract: Strip tillage (ST) can reduce fuel and labor costs of sugarbeet (Beta vulgaris L.) production. Many shank-type ST implements band fertilizer below the seed without incorporating crop residue into the soil, potentially affecting N availability. Sprinkler irrigation method may also affect N availability due to its influence on water and NO3-N movement in soil. A field study was conducted at Sidney, MT to determine if petiole NO3-N concentration and soil available (i.e. mineral) N distribution differ under (1) conventional tillage (CT) and ST systems and (2) mid-level spray application (MESA) and low energy precision application (LEPA) irrigation methods. For ST, 30-cm strips spaced 60 cm apart were tilled in the fall into small grain residues with N and P banded 7.5 cm below the seed at the time of tillage. The same fertilizer materials, application rates and application timing were used in CT plots. Mid-season petiole NO3-N concentration was lower with ST than with CT in one of three years. In-season mineral N concentration in the top 45 cm of soil was lower with ST than with CT. Post-harvest mineral N was 10% lower with ST than with CT. There were few measurable effects of irrigation method except that in-season mineral N in the top 45 cm of soil was a 10% greater with LEPA than with MESA. Root yield and sugar production were reported to be similar with the two tillage systems. It was concluded that differences in petiole NO3-N concentration and soil mineral N content were not sufficient in magnitude or frequency to justify altering N application rate based on the tillage systems or irrigation methods evaluated. However, there were indications that NO3-N leaching may be reduced by combining LEPA, with which irrigation water is applied between alternating crop rows, with strip tillage, where N is banded beneath the crop row.