This tip was provided by:
Ronnie Schnell, Cropping Systems, College Station, ronschnell@tamu.edu
Statewide
Will Grain Sorghum Respond to Starter Fertilizers?
Stater fertilizer is defined as the application of small amounts of nitrogen (N) and phosphorus (P) near the seed at planting. In-furrow or “pop-up” applications apply small rates, usually less than 6 gallons per acre, directly in the seed furrow. Another option is to place the fertilizer about 2 inches to the side and 2 inches below the soil surface. This is referred to as a 2×2 application. Application rates can be increased for 2×2 placement due to greater separation from the seed. Rates may need to be adjusted (lowered) in sandy soils to prevent seedling damage.
Starter fertilizers have been investigated extensively for corn in northern latitudes. Results in corn have been inconsistent, many showing a positive yield response in less than 4 out of 10 years. Will grain sorghum respond to starter fertilizer in Texas? Limited information is available for grain sorghum. Research from Kansas in the 1990’s shows an 18% yield increase and 6- to 7-day reduction in bloom date with a 2×2 application of N and P compared to broadcast application of the same rate. Another study from Kansas in 2002 showed a 26% yield increase for starter fertilizers compared to no-starter checks and a 11-day reduction of days to mid bloom. Trials are underway in central Texas looking at starter fertilizers in grain sorghum in combination with nitrogen rate and timing. During the first year, grain yield was increased 14% with the 2×2 application (22-73-0/acre) compared to no starter or a lower rate in-furrow starter application (7-24-0/acre). Earlier flowering was observed with 2×2 starter application in Texas as well, although only a few days earlier than plots without starter. There certainly could be advantages to earlier flowering in Texas. However, more work is needed to determine the actual economic response to starter fertilizers in Texas.
Soil sampling should be conducted to determine P requirements for grain sorghum production. Soils with low levels of extractable P are more likely to see a response to starter fertilizers. Depending on soil test recommendations, in-furrow or 2×2 application of starter fertilizers are a convenient and efficient way to apply needed P. Also, there are many different sources of phosphorus fertilizer available today that can be used in starter fertilizer solutions. Polyphosphates, orthophosphates and various ratios of the two are found in many products today. Given current grain prices, using the product that provides the most nutrient for the best price is likely the best option. Efficient timing, rate and placement will have greater impact than any particular source.
