Sorghum Nitrogen Rates: Comparing Recommendations From Standard Vs. Haney Soil

 

 

 

A field scale replicated trial testing different fertilizer nitrogen rates on sorghum was conducted in Stanley County during the summer of 2016.

 

The field selected was soil sampled in March 2016 and soil test nitrate-nitrogen level was determined by a commercial soil testing lab. The soil was calculated to have 13 lbs. of available nitrate-nitrogen in the top two feet of soil. Phosphorus and potassium levels were measured at 7 (Olsen test) and 381 ppm respectively.

 

 

In addition to the standard testing procedure, the laboratory also ran the Haney suite of tests. This is a set of procedures developed by Dr. Rick Haney. It is being promoted in some areas as being able to do a better job of predicting fertilizer requirements than traditional testing procedures when no-till and cover-crop techniques are being used. The traditional and Haney test gave different recommendations for nitrogen. The yield goal was 80 bushels per acre sorghum. Using SDSU calibrations the traditional soil test levels resulted in a recommendation of 80 lbs. of additional actual nitrogen per acre. The Haney soil test recommended 40 lbs. additional actual nitrogen.

 

 

One hundred pounds of MESZ (12-40-0-10-1) was applied to the field with seed using an 1895 drill. Additional nitrogen was applied at seeding in a midrow band at four different rates. Each rate was replicated four times. The nitrogen treatments were 0, 30 lbs., 70 lbs. and 120 lbs. of actual N applied as urea. This was the same at 25 (13 lbs. in soil and 12 lbs. from MESZ), 55, 95 and 145 lbs. actual N.

 

 

Yields were measured at harvest. Average yields for each treatment are listed in Table 1. Treatment 1 which had approximately 25 lbs. of available nitrogen yielded 71 bushels per acre. Treatment 2 which had approximately 55 lbs. of available nitrogen (and matched the Haney recommendation level) yielded 78 bushels per acre. Treatment 3 which had approximately 95 lbs. of available nitrogen (and matched the SDSU recommended level of nitrogen addition) yielded 96 bushels per acre. Treatment 4 which had approximately 145 lbs. of available nitrogen yielded 95 bushels per acre.

 

 

Statistical analysis of yield showed that yields of treatment 1 and 2 were the same but were significantly different from treatments 3 and 4. Treatment 3 and 4 were not significantly different from each other.