Brightsurf.com reports what Euopean farmers have known for years - that crop sensors are better at identifying what nitrogen (N) rates should be used for a particular crop than those chosen by farmers, and that their use can also reduce waste and cut costs. Trials conducted in Missouri showed that applying N at rates recommended by sensors increased maize grain yields by an average of two bushels per acre (around 125kg/ha) and in some cases up to 8 bushels an acre (c.600kg/ha). The same trials also showed that using these sensors reduced N wastage (i.e. N applied but not used by the crop) by around 25%.
The study's leader, Peter Scharf, a University of Missouri extension agronomist, said that although optimal N rates can vary substantially within and between fields, most U.S. corn growers still apply the same rates to entire fields or even entire farms. Many farmers in Missouri and elsewhere also spread N fertilizer months before planting, often the November before, increasing the chanvces of N being leached by winter rains and lost from the soil.
The sensors take advantage of what farmers know already from experience and common sense, Scharf says: Crops with enough N are darker green and taller, while N-deficient crops are lighter and shorter. After developing a technique for translating sensor output into a suitable N rate within a few seconds - work that was published in 2009 - Scharf and his collaborators began taking the technology to farms.
Despite the sensors' benefits, however, "the adoption numbers are still quite small," Scharf says. Complete systems currently range in price from $10,500 to $16,500, and learning to use them involves time and expense, as well. Still, these aren't the main hurdles to wider adoption, he adds. The bigger one is getting farmers to side-dress N during the growing season, rather than fertilizing in spring before planting or even the fall before.
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