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Posted 24 October 2007. Crop Management. Review of Historic Aerial Land Photos Coupled with Grid Sampling Saves Money on Lime Applications University of Missouri. cafnr.missouri.edu Columbia, Missouri (October 19, 2007)--When applying lime, producers can save money by first taking a history lesson of land use, said a University of Missouri agronomy researcher.
"Farmers should go to their county Farm Service Agency office and request aerial photographs of how the land was managed back as early as the 1940s to find causes for field variability," said Harlan Palm. Information about prior land use helps in taking soil samples to determine proper rate of lime applications, he said. Many farmers today are farming land that they did not grow up on. They may not know where things were on the land, such as buildings, disturbances where a pond was dug out and filled in or where fencerows were bulldozed. These areas are atypical from the rest of the field, and their pH levels should be sampled separately, he said. Palm studied historical aerial photos showing a 147-acre farm near Farber in Audrain County from 1939 to 1995. Photos indicated locations of buildings, farmyard and two ponds prior to 1995. Current owners consolidated smaller fields, typically 40 acres, into larger fields for greater efficiency and use of larger equipment. The impact on the soil of these disturbed areas is real, whether it is soil pH or nutrients, he said. Palm took soil samples on a varying grid density based on a 1962 photo. Fields uniformly farmed for 75 years were sampled every 2.5 acres. Around pond areas, sampling was done at one sample per acre. Where buildings once stood, samples were taken in a denser 0.5 per acre grid. "You would expect spatial variability where the farmyard and buildings once stood," Palm said. Soil pH indicated on a prescription map showed great variability. About 40 percent of the land needed no additional lime at all. A truck equipped with a GPS guidance system used the map to apply various rates of lime. As a result, total lime application decreased from a range of 294-441 tons to 95 tons, a savings of $2,000 to $3,500 per acre. Some areas required 5 tons per acre where pH was low, he said. Other areas needed no lime. "The premise of precision agriculture is recognizing variability within a field and the causes of variability. Soil pH is one of the principle inputs that can vary across a field. Even if all other inputs are at ideal level, if the soil pH is not adjusted properly, there will be variability in crop production," Palm said. Contact: |
