SUGARBEET ROTATION STUDIES - 1971

Northwest Experiment Station
Olaf C. Soine, Soil Scientist

The first four-year cycle of this experiment was completed in 1970, and the data will be summarized. The fertilizer plan for beets was changed in 1971 to utilize soil nitrate-nitrogen test to determine nitrogen rates. One-hundred-fifty pounds of total nitrogen per acre was the desired rate, and if needed, ammonium nitrate was added to the amount of soil nitrate nitrogen in the 0-24 inch depth to reach this rate. The cropping plan of the original six 4-year rotations was continued.

Table 1 gives the average amount of soil nitrate-nitrogen (NO3-N) for the six rotations, amount of ammonium nitrate (NH4NO3) added, and total nitrogen. Soil samples were taken October 1970 from 0-24 inch depth and the replications were averaged. Beets always follow the last crop in the 4-year rotation as given in table 1.

The three different fallow rotations had a large supply of nitrate nitrogen in the soil 0-24 inch depth, ranging from 164 to 197 lb per acre. On the legume fallow plots, green material equal to 2,126 lb of dry matter per acre was plowed under about the last part of June. The first crop of hay on the alfalfa fallow plots, which averaged 2,140 lb per acre, was removed and the stubble was plowed under. These plots were fallowed the remainder of the year.

The amount of nitrate-nitrogen in the 0-24 inch depth on the three nonfallow plots were similar and about what could be expected after four years of cropping.

In the spring of 1971, the sugarbeet plots were divided and ammonium nitrate was added to one-half of the plots which were below 150 lb per acre of nitrogen. The other half of the plots received the same fertilizer treatment that was used during the past four years. This yield, percent sugar, and impurity index are given in table 2.

The addition of nitrogen increased the yield of beets on the three nonfallow plots. The largest increase of 3.75 tons of beets per acre was following oats.

There were no essential differences in percent sugars from the added nitrogen compared to no nitrogen.

The beets from the three non-fallow plots had the lowest impurity indexes.

The 1971 crop yields for all six rotations are given in table 3. The yields of wheat, barley and oats are good and above average. Potatoes and soybeans were above average in yield.

Table 3 gives the beet yields for each rotation without and with added nitrogen.


1971 Sugarbeet Research and Extension Reports. Volume 2, pages 79 - 80.


Red River Trade Corridor
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