Nitrogen for Fodder Beet

Article provided by Ballance Agri-Nutrients

Fodder beet can provide a high yielding, high energy crop for late autumn and winter feed, but nutrient management and crop establishment practices can impact yields.

To develop better nutrient management advice, a Sustainable Farming Fund project researched the impacts of different rates and number of applications of nitrogen (N) on fodder beet yield. The impact of crop establishment and different rates of potassium and boron (other important nutrients for fodder beet) were also investigated. Trials were conducted over two years at sites across five of the main fodder beet production regions, including Canterbury and Southland.  Yield response to N fertiliser varied across sites in year 1 of the study, with responses seen between 100 and 200 kg/ha of added N at one site, and no response to added N at three sites. Year 2 showed similar results, with peak N response up to 100 kg/ha of added N.  

Results indicated N should be applied prudently to fodder beet, as it is a luxury feeder of N. In the trials, increasing N application rates increased crop N uptake and N concentration, but not yield. Overall, the project concluded that in most cases adding up to 100 kg N/ha should suffice to optimise yield. Splitting N applications between sowing and canopy closure helps to achieve optimal yields, as it drives canopy development and closure and supports subsequent growth. Splitting N inputs over three applications was shown to have little benefit in terms of additional yield.  In addition, splitting N inputs over two or three applications made little difference to end of season N leaf concentrations at two of the trial sites (see Table 1).  So according to the trials, a third N fertiliser application to enhance the N concentration/protein content of fodder beet by the end of the growing season is uneconomic.

Table 1 Impacts of different N application rates and number of applications on fodder beet leaf N concentration by season end at Canterbury and Southland trial sites:

The response to N fertiliser varies depending on the amount of available N already in the soil, highlighting the value of soil testing so as to avoid unnecessary application of N. The Ballance fodder beet profile test, taken before sowing to a depth of 150 mm, will determine levels of available N, potassium and boron, as well as phosphorus, pH, sulphur, sodium and magnesium. Land just out of pasture has higher levels of available N (up to 300 kg N/ha) whereas previously cropped land may have available N levels of around 100 kg N/ha, and fertiliser N requirements of around 100 kg N/ha. 

About half of the required N is best applied with the base or starter fertiliser before or at sowing. Some or all of the base or starter N can be applied as DAP or Cropzeal Boron Boost at drilling, in a separate box to the seed to avoid direct contact in the soil. If potassium is required, potassium chloride (potash) can be applied with the base dressing before sowing. The remainder of the required N can be applied as post-emergence N at canopy closure using SustaiN.

The Sustainable Farming Fund project involved Ballance Agri-Nutrients and other partners.