Soil Tests for Predicting Corn Response to Nitrogen Fertilizer in New York
2006
Klapwyk, Jonathan H. | Ketterings, Quirine M.
The presidedress nitrate test (PSNT) is currently the best tool available for Northeastern producers to determine if corn (L.) will benefit from sidedress N. The PSNT requires 0- to 30-cm soil samples, which can be difficult to obtain on stony soils, and samples need to be taken in late-spring, an inopportune time for dairy () farmers. Additionally, the in-season nature of the PSNT prevents its use by producers who apply preplant broadcast N. The Illinois soil N test (ISNT) is a simple test that estimates a potentially mineralizable fraction of soil organic N, amino sugar N. The test was able to identify sites that are nonresponsive to sidedress N fertilization in Illinois. From 2002 to 2004, 33 field trials were conducted to assess the effectiveness of the ISNT as compared with the PSNT in New York. Results confirmed the ability of the PSNT to separate responsive from nonresponsive corn sites. The ISNT was not an effective predictor by itself. However, when ISNT results and soil organic matter (OM) were considered, critical values could be developed that separated fields that were responsive to sidedress N from nonresponsive sites for corn silage dry matter yield, N concentration, N uptake, and estimated milk yield (kg of milk per ha predicted based on yield and quality of the silage). Further evaluation of the ISNT with consideration for OM could improve the accessibility of soil N testing to corn producers who apply N as sidedress as well as those who fertilize with preplant broadcast applications in the Northeast.
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