High textbook cost is a major obstacle to affordable higher education. Open textbooks present one solution, but open laboratory manuals must be developed for lab-based courses to successfully reduce overall textbook costs. Here, we present the Soils Laboratory Manual , an open-source lab manual for undergraduate, introductory soil science courses. The manual facilitates the ability for instructors to develop their own editions of the manual customized for their specific course, teaching style, students, or even local soils. The manual was implemented in AGRON 305, an introductory soil science course at Kansas State University. During the fall 2016 and spring 2017 semesters, 213 AGRON 305 students responded to a survey that included questions regarding textbook costs, open textbooks, textbook format, and the Soils Laboratory Manual . Of students surveyed, 62% had forgone purchasing required textbooks due to cost, demonstrating a clear need for textbook alternatives. Overall, the Soils Laboratory Manual was well received. Based on student preferences, lab manual formatting should be optimized for printed copies, or for PDFs viewed using laptops. Adoption of the Soils Laboratory Manual saves AGRON 305 students a cumulative $12,410 per semester. Similar savings are expected as new editions are developed for other soils courses across the United States and abroad. The Soils Laboratory Manual serves as a model for developing open-source resources for natural science courses.

Corn (Zea mays L.) nitrogen (N) rate trials conducted in North Carolina over a recent 10‐year time frame (2001–2011) were reviewed to potentially adjust yield goals (realistic yield expectations [RYE]) and their associated N rate recommendations in the North Carolina RYE database. The analyzed trial data provided evidence that corn yields increased by 15, 18, and 31% in the Coastal Plain, Piedmont, and Mountain regions, respectively. To reflect these increases, realistic yield expectations in the database were adjusted upward by 20%. However, linear‐plateau regressions confirmed that the current N rate recommendations in the RYE database were appropriate for obtaining optimum agronomic yields and therefore were not adjusted. While our approach does not permit direct statistical comparison of different tillage methods or crop rotations, long‐term no‐till (>10 years) was the only tillage category with higher measured optimum yields and significantly lower calculated N factors (amount of N applied per unit of yield [lb N bu−1] at the optimum N rate) than the standard RYE database values. However, measured yields and optimum N rates between conventional and no‐till (>10 years) were similar. For corn following soybean [Glycine max (L.) Merr.] rotations (but not corn following corn), mean optimum yield was higher and the value of the N factor was lower than the standard values.

Every day, news relevant to Extension clientele is posted to the Internet from a variety of sources such as the popular press, scientific journals, and government agency press releases. In order to stay current with the information being published, an end-user must be following all of the possible sources of information. That task can be intimidating and impractical. The development and publication of an automated news-indexing blog provides readers with a single source for daily, even hourly, updates of current events related to a specific topic.

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.

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.

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 (r2 = 0.87 [n = 20] and 0.78 [n = 10], respectively); data were insufficient 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 (r2 = 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 (r2 = 0.77, 0.87, and 0.87, respectively) and poorly drained sites (r2 = 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.

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.

The soil amino sugar nitrogen (ASN) test has been developed to predict corn (Zea mays L.) nitrogen (N) need, but ASN varies widely within fields. This study examined the spatial relationships of ASN with soil and landscape properties to develop a better N management strategy. The study was conducted on a loamy sand field in North Carolina, USA. Amino sugar N was correlated with humic matter (HM; r(2) = 0.61) and soil texture (r(2) = 0.55 - 0.63). These correlations confirm that ASN can be used to create a variable rate N application, because it is spatial sensitive to soil properties that influence N availability Amino sugar N soil sampling zones can be created from maps of HM, soil texture, and soil type to reduce sampling costs and time.

Because of the wide variation in climate, crops, cropping systems, soil types, multiple losspathways, BMPs, distance to water, and many other factors, use of a P loss index is the option best suited forNorth Carolina. Although more difficult to develop, a robust P loss index that accurately accounts for thesevariations between and within fields is the only approach that can reasonably assess the potential for P deliveryto surface and groundwater through diverse pathways. The North Carolina P loss assessment tool (PLAT) willbe applied on a field-by-field basis as part of the voluntary NRCS nutrient management planning process.While the process is not complete at this writing, the basic components of the PLAT have been developed andare currently being field tested. Ultimately, PLAT will be used to assign each field or conservationmanagement unit a low, medium, high, or very high relative risk rating for excessive P delivery to nearby water.By assessing each potential P loss pathway independently, the PLAT will also help identify specific BMPs thatmay reduce the risk for P loss.

The traditional role of field days and tours has been to introduce growers and agricultural professionals to new technologies and techniques so that the audience could see how these technologies or techniques could be practically used and applied. Based on this concept, the use of field days or tours to demonstrate the radically new technologies and site-specific management techniques behind precision farming is a perfect application of these tools. Indeed, a survey of precision farming field days held in a number of states found that field days were beneficial in showing growers and agricultural professionals global positioning systems, yield monitoring systems, techniques for grid soil sampling, software for geographic information systems, vehicle guidance systems, variable-rate application equipment, and a host of other technologies and processes. In particular, hands-on experiences, such as field demonstrations, guided sampling activities, and combine harvesting demonstrations are extremely well received and valuable. Indoor seminars featuring farmer panels, side-by-side software demonstrations, and demonstrations of geographic information systems have received high marks by participants. The survey found that a field day must be centered on a well-defined objective and a thorough understanding of the needs of the audience. Survey respondents unanimously agreed that precision farming field days and tours will be even more important as future advances in technology and management techniques are discovered. However, future precision agriculture field days or tours must be coupled with other issues or topics where precision agriculture technologies can be used to solve a practical problem and enhance management practices.

The spatial variability of soil pH, Cu, Zn, and P was examined in four North Carolina fields that had received long-term applications of animal waste. Soil samples were collected to a depth and georeferenced with differential global positioning satellite for spatial analysis. All fields met current regulatory limits set for Cu, Zn, and P, however some areas within the field exceeded current design criteria for new animal waste feeding operations. Copper, Zn, and P can vary in each field due to the variability of the chemical parameters within the field; size, shape and slope of field; distance between sampling points; climatic factors; and method of animal waste application. Precision farming techniques such as grid sampling and variable rate manure application can extend the life of the land application fields by applying nutrients only in the areas necessary and avoiding areas of excess nutrients.