Posted on Dec 01, 2009
Nitrogen fertilizer represents a significant investment for many sorghum growers. In Kansas growers will normally invest $15 to $60 per acre in nitrogen each year. Recent work shows that the current preplant N recommendations overstimate N needs by 26 pounds N per acre, if growers use a preplant soil test. Without soil tests that over recommendation can easily double. However, less than 10% of the sorghum fields grown in Kansas use current profile N tests as a base for N recommendations.
Sorghum is also normally grown in high risk environments. One too available to growers to reduce the risk and enhance return on their fertilizer investments is to delay N application until mid-season, when a better assessment of yield potential and N need can be made. By using crop sensors mid-season, together with well placed N fertilized reference strips, much more accurate N recommendations can be made.
The efficiency with which applied N is recovered by the sorghum crop, NUE, also varies dramatically. Past work in Kansas has shown N recovery to vary from <30 to >60%. This significantly impacts both yield and the N application rate required to reach maximum yield.
This project proposes to conduct a series of field experiments to address these three issues. Classical N response data will be collected to assist in the development of more effective N rate recommendations, both traditional preplant soil tests based and sensor based. In addition a NUE rate adjustment will be developed using both results found in the literature and new field data which will allow quantifying differences in NUE found between various N management practices.
The potential benefits to farmers will be much more accurate N fertilizer recommendations, reduced N application costs and potentially higher yields. This could result in a potential increase in net returns of $5 to $20 per acre from a combination of reduced N cost and/or higher yield.