Illinois soil nitrogen test for prediction of fertilizer nitrogen needs of corn in Virginia

John T. Spargo, Marcus M. Alley, Wade E. Thomason, Steven M. Nagle

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


Current N needs for corn (Zea mays L.) in Virginia are estimated based on expected yield and are adjusted to account for the estimated amounts of N mineralized from organic sources such as manures, biosolids, and legumes. The dynamic nature of soil N creates significant uncertainty in estimates of N availability from these sources. Accurate quantification of organic N mineralization during the corn growing season should improve the precision of fertilizer N recommendations. The Illinois soil N test (ISNT) has shown promise as a tool for estimating mineralizable soil N and predicting corn fertilizer N needs. Other research has found the ISNT to be poorly related to labile soil N and unrelated to corn response to fertilizer N. The objective of this study was to determine if the ISNT predicts the fertilizer N response of corn grown in a diverse set of Virginia agroecosystems. We conducted 29 on-farm fertilizer N response trials in major corn-producing regions of Virginia. The ISNT was significantly related to estimated yield without fertilizer N (R 2 = 0.57, P < 0.0001) and relative yield (R 2 = 0.64, P < 0.0001). We also found that the ISNT extracted a consistent percentage of total soil N (16.3 ± 0.7%), suggesting that it is a poor indicator of labile N. In fact, total soil N did as well as the ISNT at predicting yield without fertilizer N (R 2 = 0.53, P = 0.0002) and relative yield (R 2 = 0.64, P < 0.0001). The ISNT offered no more information about corn yield response to fertilizer N than did total soil N content.

Original languageEnglish (US)
Pages (from-to)434-442
Number of pages9
JournalSoil Science Society of America Journal
Issue number2
StatePublished - Mar 2009

All Science Journal Classification (ASJC) codes

  • Soil Science


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