Research and Demonstration of Minimum Tillage and Optimum Water Management in Sugarbeet Production in Eastern Montana

Experiment 1. Tillage and nitrogen management

Analysis of variance showed that year had a highly significant effect on all measured variables, but no Year × Tillage and Year × Nitrogen interactions were observed. The greatest sugarbeet stand population (78,363 plants ha^-1) and the highest root yield (97.3 ton ha^-1) were obtained in 2017 which were significantly greater than the plant population and yield in 2016 and 2018 (Table 1). Nevertheless, the least sucrose concentration in the root (16.5%) was also recorded in this year. As a result, gross sucrose yield was significantly higher in 2017 (16,066 kg ha^-1) than in the other two years. Among the root impurities, the concentration of amino-N in 2017 was notably lower than that in 2016 and 2018. Consensually, Impurity Value and SLM were also lower in that year. The greatest extractible sucrose yield was also obtained in 2017 (15,283 kg ha^-1).

Sugarbeet plant stand, root yield, and root impurity values did not significantly differ among tillage systems. This happened regardless of the year or level of N applied. As shown in Table 1, root yield in ST and NT was about 7% greater than that in CT (averaged over years and N levels) despite fewer plant stands per ha in the ST and NT treatments. However, this yield superiority was not statistically significant. Sucrose concentration was the only variable that was significantly affected by tillage. The average sucrose concentration in CT was 17.3%, which is only slightly higher than 17.2 and 16.9% under NT and ST, respectively (Table 1). This variation in sucrose concentration was not large enough to cause a notable change in gross sucrose yield. No differences were found among three tillage systems in term of root impurities, thus no significant difference was found among them regarding Impurity Value and/or SLM. Consequently, all three tillage systems produced similar extractible sucrose yield (Table 1).

Nitrogen rate showed a significant effect on root yield, sucrose concentration, amino-N concentration, Impurity Value, and SLM. Response trend of root yield and sucrose concentration to increasing rate of N in the range of 56-224 kg ha^-1 were opposite (Table 1). While root yield linearly increased (y=4.9081X+63.718; R²= 0.9917), sucrose concentration linearly declined in response to increasing N rate (y= -0.273x+17.861; R²= 0.8166). Amino-N concentration, Impurity Value, and SLM also linearly increased when N rate increased (Table 1). Response trend to N rate was consistent among tillage systems as shown by the nonsignificant interactions of N by tillage. A journal article has been published in Soil and Tillage Journal in 2019 based on this study.

Experiment 2. Optimization of irrigation management

Total irrigation water used in each treatment is calculated. Results showed that 33 and 66% less irrigation water were used in ET66 and ET33 treatments, respectively. This can transfer to 33 and 66% less energy (diesel fuel or electricity depending on the power source of the sprinkler) being used for sugarbeet irrigation. 

Reducing irrigation water to 66 and 33% of the crop evapotranspiration tended to reduce the root yield slightly in 2018 (It is noted that the experimental site had a ground water table at about 1.5 to 2 meters deep during the irrigation season, and we suspected that the sugarbeet crop might be able to take up water from >1.5 meter deep soil in the late growing season. Therefore, the sugarbeet at 33% ET treatment did not suffer severe water stress), and withholding irrigation 30 days before harvest tended also reduced root yield slightly. Sucrose concentration responded to reduced irrigation and water withholding different from root yield; decreasing irrigation water to 66 and 33% tended to increase sucrose concentration slightly (Table 2). Farmers may optimize water management to increase sucrose concentration without significantly reduce root yield, especially by reducing the irrigation amount in the late growing season and withholding water at appropriate time prior to harvest. A journal manuscript has completed and been submitted to a journal for publication based on this study.

Table 2. Means of sugarbeet measured variables by irrigation treatment and year.

^† SLM = Sucrose Loss to Molasses. Within column and treatment, means followed by different letters are significantly different based on the LSD (0.05).

 Experiment 3. Development of a sensor-based nitrogen management system for sugarbeet

The prerequisite for a sensor-based nitrogen management system is a reliable, effective, and accurate algorithm that can effectively predict crop yield based on crop sensing during the crop growth. Accordingly, we continued working on collecting NDVI, plant height, GDD, and final yield (root yield, sucrose yield, extractible sucrose yield) in 2016, 2017, 2018, and 2019.

Based on the NDVI data, the in-season estimate of yield (INSEY) was calculated. We found a significant regression between INSEY at V10-V12 growth stage and sugarbeet final yield (R² = 0.60), and extractable sucrose yield (R²= 0.66)

Extensive statistical works are underway to carefully analyze data and to put together data of 2016, 2017, 2018, and 2019 in order to develop a reliable algorithm. Currently, we are working on a statistical analysis to perform a combined analysis of 2016, 2017, 2018, and 2019 data and relate the NDVI data to nitrogen rate, root yield, and sucrose concentration. A journal article is expected to be prepared and submitted by 2020.

Experiment 4. On-farm demonstration of no-till sugarbeet and foliar application of micronutrients

The no-till sugarbeet had very good seedling emergence and seedling establishment in the no-till sugarbeet fields (Fig. 1). The yields of the no-till sugarbeet ranged from 77 to 94 tones/ha, which are comparable to the conventional tillage beet growers achieved in the same area in 2019 (Table 3). Foliar application of different products showed some improvement to sugarbeet root yield compared to the untreated check in the no-till sugarbeet, but not statistically significant (Table 3). The foliar nutrient application study will be continued in 2020 and a extension publication will be published in 2020.

Two workshops and on-farm tour were organized on August 7, 2017 and June 25, 2019. Sugarbeet growers who attended the workshops were able to see the performance of no-till sugarbeet at the Eastern Agricultural Research Center and the operating farms at Sidney and Savage, MT.

Table 3. Plant density, root yield, sucrose concentration, and sucrose yield of no-till sugarbeet affected by foliar application of different nutrient products on Berwick and Steinbesser farms in 2019.