Finding the Right Combination

How beets react to nitrogen inputs under different tillage systems

Published online: Jan 04, 2018 Feature

This article appears in the January 2018 issue of Sugar Producer.

The sugar industry in eastern Montana and western North Dakota contributes substantially to the regional economy. Dean Bangsund at North Dakota State University estimated total direct economic impacts of sugarbeet production, processing and marketing in Montana and North Dakota at $73.9 million in 2011. Tax collections generated by the sugarbeet industry from sales and use, personal income, and corporate income taxes in the two-state region exceeded $1.8 million in fiscal 2011.

Conventional tillage is a common practice in sugarbeet production, which consists of five or more passes across a field for plowing, leveling and hilling, all of which is expensive, labor- and fuel-intensive and has many unintended consequences for soils and the environment. The negative impacts include soil organic matter degradation, soil erosion by wind, and wind damage to sugarbeet seedlings.

In recent years, there has been increasing interest from beet growers to practice conservation tillage in sugarbeet production. Implementation of an appropriate conservation tillage system would result in lowering production cost and protect soils from erosion. However, it is not clear if conservation tillage, especially no-till, will reduce sugarbeet yield and sucrose concentration. Furthermore, beet growers want to know if the fertility requirements, especially nitrogen input, are the same under conventional and conservation tillage.

The objectives of this study were to: 1) test the feasibility of practicing conservative tillage and evaluate if conservative tillage can produce the similar yield and sucrose concentration as the conventional tillage; and 2) test if conservative tillage requires different amounts of nitrogen input to achieve an optimum application rate.

 

Materials and Methods

A field study was conducted at the Eastern Agricultural Research Center at Sidney, Mont., in 2017. The experiment was a split-plot randomized complete block design with four replications. Main plots were allocated to tillage treatments, including conventional tillage, strip tillage, and no-till. Subplots were assigned to nitrogen rates of 50, 100, 150, and 200 pounds per acre. Soil background nitrogen was measured in the fall of 2016 at 12.3 pounds of NO3-N per acre. Soil in the area is classified as Savage clay loam.

Sugarbeet were planted with a no-till six-row planter on May 1. Seedling establishment was evaluated after emergence. The crop was irrigated with an overhead linear sprinklers. Weeds were controlled with glyphosate. The beets were harvested Sept. 20. A harvester-mounted scale was used to measure the pre-wash weight of all harvested beets. A representative sub-sample of approximately 20 pounds was collected from each plot and sent to Sidney Sugars for soil tare and sucrose concentration measurements. After sucrose concentration measurement, a small juice sample was collected and sent to AgTerra Technologies for impurity analyses.

 

Results

Sugarbeets in the study showed good emergence, establishment and growth in all three tillage treatments. Statistical analysis showed no significant difference among the tillage treatments in root yield and impurity, but slightly lower sucrose concentration in strip tillage. Root yield was 42.8, 45.2, and 43.8 tons per acre in conventional, strip-till and no-till, respectively. Sucrose concentrations in conventional, strip-till and no-till were, respectively, 16.8, 16.3 and 16.6 percent. Impurity values measured 0.53, 0.54 and 0.52 percent; sucrose losses to molasses were 0.80, 0.81 and 0.79 percent, respectively.

Statistical analysis also showed no significant interactions between tillage and nitrogen treatment, but nitrogen showed significant effect on root yield, sucrose concentration and impurity. Root yield increased linearly from 37.8 to 49.6 tons per acre when nitrogen rate increased from 50 to 200 pounds per acre. In contrast to yield, sucrose concentration decreased linearly from 16.9 to 16.1 percent when nitrogen rate was increased from 50 to 200 pounds per acre. Furthermore, with nitrogen rate increased, impurity value and percentage of sucrose loss to molasses also increased.

 

Conclusion

In this study, there was no significant difference in sugarbeet root yield between conventional and conservation tillage. Although the sucrose concentration was slightly lower under strip tillage, it did not result in total sugar yield (root yield multiplied by sucrose concentration) differences among the tillage treatments. No significant differences in sugar yields among the tillage treatments suggests that no-till practices can be adopted to reduce the expenses of labor and fuel, as well as reducing the impact of soil erosion and soil organic matter degradation.

No tillage by nitrogen rate interactions indicates conservative tillage and conventional tillage have similar nitrogen requirements. Nitrogen application rate and timing need to be optimized for maximum economic returns, because higher nitrogen rate will result in higher root tonnage, lower sucrose concentration, and higher impurity value, thereby affecting sugarbeet price and transportation costs.

 

Chengci Chen, Reza Keshavarz Afshar, Abdelaziz Nilahyane and Ronald Brown are researchers with Montana State University’s Eastern Agricultural Research Center. Bart Stevens and William Iversen are based out of the USDA-ARS Northern Plain Agricultural Research Laboratory. Timothy Fine is an extension educator at MSU’s Richland Extension Office. All authors are based in Sidney, Mont.