Browsing by Author "Shober, Amy L."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
Item Assessing relationships of cover crop biomass and nitrogen content to multispectral imagery(Agronomy Journal, 2024-02-29) Miller, Jarrod O.; Shober, Amy L.; Taraila, JamieCover crops provide valuable roles in sustainable agriculture, provided they produce enough biomass. To accurately measure their services to field management, spatial estimates would be useful to producers. This study used multispectral drone imagery to produce maps of normalized difference vegetation index (NDVI), normalized difference red edge index (NDRE), and a digital surface model (DSM) of cover crop plots on sandy, Mid-Atlantic soils. Cover crops included cereal rye (Secale cereale), mixtures of rye and crimson clover (Trifolium incarnatum), and mixtures of rye and hairy vetch (Vicia villosa). Their biomass was sampled in the spring of 2019, 2020, and 2021, dried, weighed, and analyzed for total nitrogen (N) content. Measurements of NDVI became saturated (i.e., reached a linear plateau) at 3.86 Mg biomass ha−1, NDRE at 5.72 Mg biomass ha−1, and the DSM at 5.11 Mg biomass ha−1. The measured N content became saturated at 80.9, 139.1, and 75 kg N ha−1 for NDVI, NDRE, and the DSM, respectively. Based on log transformations, NDVI was a stronger predictor of biomass and N, but not C:N. The NDRE was important for biomass, N, and C:N, while the DSM interactions with cover crop species helped predict both the N content and C:N of cover crop tissues. Accumulated growing degree days was important as an individual variable for biomass and N and as an interaction with cover crop species. Abbreviations DSM digital surface model GDD growing degree days NDRE normalized difference red edge index NDVI normalized difference vegetation indexItem Improving targeting of farmers for enrollment in agri-environmental programs(Applied Economic Perspectives and Policy, 2023-05-18) Duke, Joshua M.; Johnston, Robert J.; Shober, Amy L.; Liu, ZhongyuanAgricultural cost-share research and planning tend to focus on one program at a time, and hence overlook additional efficiencies that might be obtained by considering the possibility that enrollment decisions are related across different programs. Models of multiple-program participation decisions enable these relationships to be considered as part of conditional enrollment predictions, providing more complete and accurate understanding of enrollment behavior. Analysis of data from farmer surveys in Maryland and Ohio show complementary drivers across program participation. Results are consistent with economies of scale and/or scope among different agri-environmental programs. The data also show the gains in prediction accuracy when the model accounts for participation in other programs, thereby enabling improved targeting and program design. For instance, enrollment in commodity-type programs causes a much larger marginal increase (12.6%) in the probability of Maryland cover crops participation than does the increase from Conservation Reserve Program enrollment (4.4%).Item Post-harvest drone flights to measure weed growth and yield associations(Agricultural & Environmental Letters, 2022-06-14) Miller, Jarrod O.; Shober, Amy L.; VanGessel, Mark J.Drone flights are often only performed during the growing season, with no data collected once harvest has been completed, although they could be used to measure winter annual weed growth. Using a drone mounted with a multispectral sensor, we flew small plot corn (Zea mays L.) fertility, cover crop, and population studies at black layer and 0–14 d after harvest (DAH). Yields had positive correlations to normalized difference vegetation index (NDVI) at black layer but often had negative correlations to corn yields 0–14 DAH. After harvest, NDVI could be associated with weed growth, and negative correlations to yield could point to reduced corn canopy allowing light to reach late-season weeds. In fertility studies, excess nitrogen appears to increase weed biomass after harvest, which can be easily identified through drone imagery. Flights should be performed after corn harvest as weed growth may provide additional insight into management decisions. Core Ideas: - Corn yields can be correlated to post-harvest weed biomass by using NDVI. - Drone flights efficiently mapped weeds and made correlations to yield and management. - Fall weed control can be prioritized using drone mapping. Abbreviations: DAH days after harvest LAI leaf area index NDVI normalized difference vegetation indexItem Soil health tradeoffs may be minimal in phosphorus-enriched Coastal Plain soils(Agricultural & Environmental Letters, 2023-03-31) Mosesso, Lauren R.; Shober, Amy L.Soil health practices can improve soil conditions and provide ecosystem services, but increased risk of phosphorus (P) loss can be an unintended consequence. We investigated conservation tillage and cover crops effects on soil P stratification, P accumulation at depth, and soil aggregation for sandy Coastal Plain soils from the Mid-Atlantic United States soil cores from 10 agricultural fields with 0–15 years of conservation tillage or cover cropping were analyzed for Mehlich-3 P and dry aggregate stability. We found no evidence that conservation tillage or cover cropping caused P stratification or accumulation in study fields that were already enriched with P prior to soil health implementation. Annual particulate, dissolved runoff, and leachate P loads decreased when estimated using the North Carolina Phosphorus Loss Assessment Tool assuming no-till and cover crops (soil health) compared to conventional till and winter fallow (conventional). We suggest that soil health practices are unlikely to exacerbate P losses from high P Coastal Plain soils beyond their initial risk profile. Core Ideas: - Soil health practices may increase the risk of surface and subsurface phosphorus (P) loss in P-enriched soils. - Soil P stratification in 10 fields with and without soil health practices were compared. - There is no evidence that soil health practices increased the risk for dissolved soil P losses. - Soil health practices may reduce P loads in fields with significant sources of dissolved P. Abbreviations: DP dissolved phosphorus NC-PLAT North Carolina Phosphorus Loss Assessment Tool PP particulate phosphorus