Submitted to: Journal of Sugarbeet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2011
Publication Date: 10/25/2011
Citation: Stevens, W.B., Evans, R.G., Jabro, J.D., Iversen, W.M. 2011. Sugarbeet productivity as influenced by fertilizer band depth and nitrogen rate in strip tillage. Journal of Sugarbeet Research. 137-154.
Interpretive Summary: Strip tillage provides a viable means to implement reduced tillage practices in sugarbeet production. Most strip till equipment currently available is equipped to apply fertilizer in a band at varying depths below the seed row. Banding N and P can improve fertilizer uptake efficiency because nutrients are close to the developing root system. However, band depth and fertilizer application rate are critical factors determining whether the maximum benefit of the fertilizer will be realized. If the band is placed too far away from the seed or the application rate too low, seedlings may suffer early-season nutrient deficiency and reduced yield. Conversely, fertilizer applied too close to germinating seed or in excessive amounts may result in salinity levels that cause seedling injury and reduce plant population. A field study was conducted by scientists at the USDA-ARS Northern Plains Agricultural Research Laboratory in Sidney MT to evaluate the effect of fertilizer placement depth and N application rate on sugarbeet seedling emergence, N uptake and yield under fall ST and sprinkler irrigation. Results indicated that fertilizer band placement between 7.5 and 12.5 cm deep (5 to 10 cm below the seed) resulted in the best combination of N uptake and seedling emergence. Results also suggest that caution is warranted when banding N at rates greater than 146 kg N ha-1, especially where conditions maximize the risk of fertilizer injury (e.g., dry climate, sandy textured soil, spring ST).
Technical Abstract: Strip tillage (ST) implements typically band fertilizer below the seed; however, for sugarbeet (Beta vulgaris L.) placement either too close or too far away from the seed may be detrimental. A field study was conducted at Sidney, MT to determine (1) the optimum depth of the fertilizer band for fall ST and (2) if the optimum band depth is affected by N fertilizer application rate. Strip tillage was performed in the fall using a shank-type implement that tills 30-cm wide strips spaced 60 cm apart in small grain residue. Nitrogen and P fertilizers were banded below the seed at depths of 2.5, 7.5, or 12.5 cm from the soil surface. Nitrogen was applied as dry urea [(NH2)2CO] at 78, 146, or 212 kg N ha-1. Plant population tended to be lowest when fertilizer was placed at 2.5 cm. In 2008 plant population was 7 to 13% less when placed at 2.5 or 7.5 cm compared to the 12.5-cm depth. Nitrogen content of above-ground biomass (AGBM) was greatest with the 7.5-cm depth. Plant population was consistently lower when N was applied at 212 kg N ha-1 resulting in a harvest population that was 7% less than when N was applied at 78 or 146 kg ha-1. Increasing N application rate led to increased N uptake, reduced root sucrose content and increased root yield. Optimum band depth did not depend on N application rate. It was concluded that fertilizer band placement between 7.5 and 12.5 cm deep (5 to 10 cm below the seed) resulted in the best combination of N uptake and seedling emergence. Caution is warranted when banding N at rates greater than 146 kg N ha-1, especially where conditions maximize the risk of fertilizer injury (e.g., dry climate, sandy textured soil, spring ST).