@article{williams_crozier_white_sripada_crouse_2007, title={Comparison of soil nitrogen tests for corn fertilizer recommendations in the humid southeastern USA}, volume={71}, ISSN={["0361-5995"]}, DOI={10.2136/sssaj2006.0057}, abstractNote={Environmental concerns about increasing NO 3 levels in watersheds in North Carolina and elsewhere indicate the need for better N fertilizer management. Nitrate levels might be reduced if N rates could be adjusted based on field- or site-specific knowledge of corn (Zea mays L.) response to N fertilization. Currently, there is no effective soil N test for the humid southeastern USA. This study was conducted to compare three soil N tests for practicality, precision, and ability to correlate with economic optimum N rate (EONR) and fertilizer response on southeastern U.S. soils. The soil N tests were the Illinois soil N test (ISNT), the gas pressure test (GPT), and the incubation and residual N test (IRNT). Soil samples were collected from the sites of 16 N-response trials from 2001 to 2003 where different mineralizable and residual N levels were expected. The ISNT was determined to be the most practical test because it was the easiest to perform and could be completed in 1 d. The ISNT and GPT had better precision (lower CV) than the IRNT (9 and 13 vs. 61%, respectively). All three tests were related to EONR; ISNT had the strongest linear relationship (r 2 = 0.90) when consideration was restricted to sites on mineral soils. The ISNT and GPT were related to delta yield (maximum yield minus check yield; r 2 = 0.49 and 0.60, respectively) and fertilizer response (r 2 = 0.31 and 0.51, respectively). These results indicate the potential of the ISNT and GPT to account for mineralizable and residual soil N levels and thus improve current corn N recommendations in the humid southeastern USA.}, number={1}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, publisher={Soil Science Society of America}, author={Williams, Jared D. and Crozier, Carl R. and White, Jeffrey G. and Sripada, Ravi P. and Crouse, David A.}, year={2007}, pages={171–180} }
 @article{maguire_crouse_hodges_2007, title={Diet modification to reduce phosphorus surpluses: A mass balance approach}, volume={36}, ISSN={["0047-2425"]}, DOI={10.2134/jeq2006.0551}, abstractNote={Diet modification to reduce phosphorus (P) concentrations in manures has been developed in response to environmental concerns over P losses from animal agriculture to surface waters. We used USDA-NASS statistics on animal numbers and crop production to calculate county scale mass balances for manure P production, P removed in harvested portion of crops, and the potential effects of diet modification. Although spreading manure evenly over all crop acreage within a county is unlikely to occur, these calculations give a good indication as to the impact diet modification to reduce P can have at a regional or national scale. There was a high degree of regional variability in manure P surpluses (e.g., with the large crop acreages in the grain belt leading to large P offtake in crops preventing most P surpluses). In 89% of counties, there was a deficit of manure P relative to crop P removal; therefore there was a manure P surplus in 11% of counties. Diet modification decreased the percentage of states with a manure P surplus from 11 to 8%, a decrease of approximately 27%. Diet modification decreased the percentage of counties with the greatest surpluses of manure P (>30 kg ha(-1)) from 3% of all counties to 1%. Diet modification to decrease manure P is an important part of strategies to alleviate environmental concerns associated with surplus manure P in many areas, but additional strategies to deal with manure P surpluses are needed in some areas.}, number={5}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Maguire, R. O. and Crouse, D. A. and Hodges, S. C.}, year={2007}, pages={1235–1240} }
 @article{williams_crozier_white_heiniger_sripada_crouse_2007, title={Illinois soil nitrogen test predicts southeastern US corn economic optimum nitrogen rates}, volume={71}, ISSN={["0361-5995"]}, DOI={10.2136/sssaj2006.0135}, abstractNote={An accurate and quick soil N test is needed for N fertilizer recommendations for corn (Zea mays L.) for the humid southeastern USA. The Illinois soil N test (ISNT) has been used to distinguish fertilizer-responsive from unresponsive sites in Illinois. We determined relationships between economic optimum N rates (EONR) and ISNT levels in representative southeastern soils in 35 N-response trials in the Piedmont (n = 4) and Middle (n = 8) and Lower (n = 23) Coastal Plains of North Carolina from 2001 to 2004. The ISNT was strongly correlated with EONR for well or poorly drained sites (r 2 = 0.87 [n = 20] and 0.78 [n = 10], respectively); data were insuffi cient for establishing correlations for very poorly drained or severely drought-stressed sites. Expressing ISNT on a mass per unit volume basis vs. EONR improved the correlations slightly (r 2 = 0.88 and 0.79 for well and poorly drained sites, respectively), but these improvements would not justify the necessary soil bulk density determinations. Regressions of ISNT vs. minimum, average, and maximum EONR based on different N-fertilizer cost /corn price ratios (11.4:1, 7.6:1, and 5:1, respectively) showed strong correlations with EONR for well-drained sites (r 2 = 0.77, 0.87, and 0.87, respectively) and poorly drained sites (r 2 = 0.84, 0.78, 0.70, respectively). The ISNT–EONR correlations were different among the cost/price ratios for well-drained sites, but not different for poorly drained sites. Because ISNT predicted EONR robustly to different cost/price ratios, ISNT has the potential to modify or replace current N recommendation methods for corn. Abbreviations: EONR, economic optimum nitrogen rate; HM, humic matter; ISNT, Illinois soil nitrogen test; RYE, realistic yield expectation.}, number={3}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, publisher={Soil Science Society of America}, author={Williams, Jared D. and Crozier, Carl R. and White, Jeffrey G. and Heiniger, Ronnie W. and Sripada, Ravi P. and Crouse, David A.}, year={2007}, pages={735–744} }
 @article{anderson_thompson_crouse_austin_2006, title={Horizontal resolution and data density effects on remotely sensed LIDAR-based DEM}, volume={132}, ISSN={["1872-6259"]}, DOI={10.1016/j.geoderma.2005.06.004}, abstractNote={Terrain analysis of digital elevation models (DEM) has become an important technique to assess landscape and watershed scale hydrologic and pedologic processes and the spatial variability of soil and ecologic properties. Light detecting and ranging (LIDAR) elevation data sets provide the flexibility needed to produce multiple horizontal resolutions of DEM from the same data source. A series of 61 LIDAR tiles (100 ha) were collected from the North Carolina Flood Mapping Program covering the spatial extent of the Hofmann Forest in the Lower Coastal Plain of Eastern North Carolina. The LIDAR data set was reduced to 50%, 25%, 10%, 5%, and 1% of the original density. We created 5-, 10-, and 30-m DEM with 0.1 m vertical precision for each density level and used paired t-test to determine if the true mean of their differences were equal to zero. Differences indicated that for the 30-m DEM, LIDAR data sets could be reduced to 10% of their original data density without statistically altering the produced DEM. However, the 10-m DEM could only be reduced to 25% of the original data set before statistically altering the DEM. Data reduction was more limited for the 5-m DEM with possible reduction only to 50% of their original density without producing statistically different DEM. Our evaluation provides some indication as to the minimum required LIDAR data density to produce a DEM of a given horizontal resolution. However, evaluation of additional horizontal resolutions and additional density reduction is required to provide a clearer understanding of the effect of LIDAR data density.}, number={3-4}, journal={GEODERMA}, author={Anderson, Eric S. and Thompson, James A. and Crouse, David A. and Austin, Rob E.}, year={2006}, month={Jun}, pages={406–415} }
 @article{crouse_sierzputowska-gracz_mikkelsen_wollum_2002, title={Monitoring phosphorus mineralization from poultry manure using phosphatase assays and phosphorus-31 nuclear magnetic resonance spectroscopy}, volume={33}, ISSN={["0010-3624"]}, DOI={10.1081/CSS-120003882}, abstractNote={Phosphatase enzymes are responsible for mineralization of organic-phosphorus (P) compounds in soil where they hydrolyze the organic phosphate esters to inorganic phosphate. One way to monitor the mineralization process in soils receiving poultry manure is by assessing the activity of phosphatase in a soil amended with poultry manure relative to a soil that is not amended. In a laboratory incubation, soil phosphomonoesterase activity and soil phosphodiesterase activity were measured 0, 1, 2, 4, 8, 12, 16, and 20 weeks after soil incorporation of poultry litter. Two soils, both Fine-loamy siliceous, thermic Typic Kandiudults, were used in the study. Both soils differed in their previous management. The first soil was from a conventionally tilled field that received annual poultry litter applications for 18 consecutive years. The second soil was from an adjacent recently cleared woodland that had no history of manure application. In the previously non-manured soil, soil phosphodiesterase activity following poultry litter addition increased from 4 to 66 μg p-nitrophenol g soil−1 hour−1 by the second week. However, in the same soil, after 8 weeks, phosphodiesterase activity resulting from poultry litter applications was not evident. There was a net increase in phosphomonoesterase activity from week 0 to 20 in the previously manured and previously non-manured soils that were amended with poultry litter. A simultaneous study was conducted to measure the relative concentration of organic P forms during the mineralization process using 31P nuclear magnetic resonance. Subsamples from the poultry manure-amended soil were extracted with 0.25 M NaOH+0.05 M EDTA following 0, 1, 2, 4, 8, 12, 16, and 20 weeks after manure addition and incorporation. The concentration of organic P compounds decreased from the time of poultry litter incorporation until week 20 whereas orthophosphate concentration increased during this period.}, number={7-8}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, author={Crouse, DA and Sierzputowska-Gracz, H and Mikkelsen, RL and Wollum, AG}, year={2002}, pages={1205–1217} }
 @article{heiniger_havlin_crouse_kvien_t._2002, title={Seeing is believing: The role of field days and tours in precision agriculture education}, volume={3}, ISBN={1385-2256}, number={4}, journal={Precision Agriculture}, author={Heiniger, R. W. and Havlin, J. L. and Crouse, D. A. and Kvien, C. and T., Knowles.}, year={2002}, pages={309} }
 @article{crouse_sierzputowska-gracz_mikkelsen_2000, title={Optimization of sample pH and temperature for phosphorus-31 nuclear magnetic resonance spectroscopy of poultry manure extracts}, volume={31}, ISSN={["0010-3624"]}, DOI={10.1080/00103620009370432}, abstractNote={Abstract Organic phosphorus (P) compounds can be characterized using nuclear magnetic resonance (NMR) spectroscopy provided conditions are suitable for detecting the NMR signal. The objective of the research was to optimize pH and temperature conditions for turkey manure extracts prior to analysis of organic P compounds using NMR. Samples of turkey manure were extracted with 0.25 MNaOH + 0.05 MEDTA. The extracts were lyophilized and resolubilized in distilled H2O before analysis on a General Electric GN500 NMR spectrometer. Initial 31P NMR experiments were run to determine the optimal instrumental parameters for 31P studies. Samples were titrated to seventeen pH values ranging from 4.0 to 13.2. Samples adjusted to pH 10.0 had the greatest spectral resolution. A seven‐by‐three factorial experiment was used to investigate the effect of seven temperatures (5,10,20,30,40,50, and 60°C) on three separate samples at pH 6.5,9.0, or 10.0. Spectra resolution was greatest at pH 10.0 and 20°C.}, number={1-2}, journal={COMMUNICATIONS IN SOIL SCIENCE AND PLANT ANALYSIS}, author={Crouse, DA and Sierzputowska-Gracz, H and Mikkelsen, RL}, year={2000}, pages={229–240} }
 @article{crouse_havlin_mcbride_white_heiniger_weisz_roberson_2000, title={Precision farming education at NC State University}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Crouse, D. A. and Havlin, J. L. and McBride, R. G. and White, J. G. and Heiniger, R. and Weisz, R. and Roberson, G.}, year={2000}, pages={1} }
 @article{jenkins_crouse_mikkelsen_heiniger_2000, title={Spatial variability of phosphorus retention capacities for various fields}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Jenkins, J. R. and Crouse, D. A. and Mikkelsen, R. L. and Heiniger, R. W.}, year={2000}, pages={1} }
 @inproceedings{robert_crouse_mikkelsen_heiniger_robarge_2000, title={Spatial variability of soil pH, phosphorus, copper and zinc in fields receiving long-term applications of animal manure}, number={2000}, booktitle={Animal, agriculture and food processing waste: 8th Symposium: American Society of Agriculture Engineers, 2000}, publisher={St. Joseph, Michigan: American Society of Agricultural Engineers}, author={Robert, B. and Crouse, D.A. and Mikkelsen, R.L. and Heiniger, R. and Robarge, W.}, year={2000}, pages={597–601} }
 @article{austin_crouse_havlin_hodges_2000, title={The Spatial Information Research Laboratory at North Carolina State University}, journal={Proceedings of the 5th International conference on precision agriculture, Bloomington, Minnesota, USA, 16-19 July, 2000}, publisher={Madison, WI : Precision Agriculture Center, University of Minnesota, ASA-CSSA-SSSA}, author={Austin, R. E. and Crouse, D. A. and Havlin, J. L. and Hodges, S. C.}, year={2000}, pages={1} }