Iowa farmers in test used soil sampling for Nitrogen reduced N Fertilizer 46% with 1% yield reductio

http://www.ewg.org/node/7715


Nitrogen Soil Tests

A vital tool to improve the timing and reduce the amount of nitrogen fertilizer applied are soil tests that can estimate how much nitrogen is available and needed in the soil at any given time. Among the most refined of these tests is the Pre-Sidedress Nitrogen Test (PSNT) for corn, which measures the amount of nitrogen available to plants in the top foot of soil in the late spring, when corn is 6 to 12 inches high. These tests are designed to help farmers sample early enough to apply additional nitrogen if it is needed but late enough to account for spring weather conditions. Armed with this knowledge, producers can fully account for all available nitrogen in their fields, and apply the amount of fertilizer necessary to obtain the optimal yields.

In Iowa, statewide surveys between 1987 and 1991 using the PSNT indicated that in 50% of corn fields, soil nitrate concentrations before the addition of fertilizer were equal to or greater than the critical concentration needed for optimal yields (Frable, et al. 1994). Nationally, farmers who use the soil test have reduced their nitrogen fertilizer application rates on corn by an average of 26 percent (Woodward, et al. 1995)

In Iowa, the nation's top corn producing state, three different studies under actual field conditions support the applicability of the PSNT (Frable, et al. 1994). All three found virtually no difference in yields between tested and non-tested fields, with yield changes that were non-existent or insignificant -- one to two percent at most. Growers using the test, meanwhile, reduced application rates by 36 percent, from 131 to 84 pounds per acre. And because they maintained yields while reducing their nitrogen use, farmers using the PSNT increased profits by $2.00-$16.00 per acre (Frable, et al. 1994). In the largest test, conducted by 70 farmers participating in an Iowa Natural Heritage Resourceful Farming demonstration project, fertilizer use was reduced by 46 percent, with less than a one percent decrease in yields. As a result, the producers who use the test obtained an average increase in profits of $5.75 per acre, with profits increasing for some farmers by as much as $46.00 per acre.

(used to make nitrogen fertilizer) but also significantly reduce Nitrogen emissions (as N2O) from farmlands. This is a not insignificant contributor to GHgs.

soil testing for Nitrogen is easy and not expensive either.

Clover ties nitrogen into ground (and can be used for many purposes), with wise (permaculture) use of clover nitrogen fertilizer is not needed at all.

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