Low-Cost Chlorophyll Fluorescence Imaging for Stress Detection

Plants naturally contain high levels of the stress-responsive fluorophore chlorophyll. Chlorophyll fluorescence imaging (CFI) is a powerful tool to measure photosynthetic efficiency in plants and provides the ability to detect damage from a range of biotic and abiotic stresses before visible symptoms occur. However, most CFI systems are complex, expensive systems that use pulse amplitude modulation (PAM) fluorometry. Here, we test a simple CFI system, that does not require PAM fluorometry, but instead simply images fluorescence emitted by plants. We used this technique to visualize stress induced by the photosystem II-inhibitory herbicide atrazine. After applying atrazine as a soil drench, CFI and color images were taken at 15-minute intervals, alongside measurements from a PAM fluorometer and a leaf reflectometer. Pixel intensity of the CFI images was negatively correlated with the quantum yield of photosystem II (ΦPSII) (p < 0.0001) and positively correlated with the measured reflectance in the spectral region of chlorophyll fluorescence emissions (p < 0.0001). A fluorescence-based stress index was developed using the reflectometer measurements based on wavelengths with the highest (741.2 nm) and lowest variability (548.9 nm) in response to atrazine damage. This index was correlated with ΦPSII (p < 0.0001). Low-cost CFI imaging can detect herbicide-induced stress (and likely other stressors) before there is visual damage

Determining the Effect of Planting Date and Land Preparation Method on Seedling Emergence, Forage Mass, and Forage Nutritive Value of Forage Brassica

Forage brassicas are used as a forage in monoculture and multispecies mixtures, yet research defining best management practices is limited. Two studies were conducted to evaluate the effects of land preparation method and planting date on establishment, forage mass, and quality of two Brassica species, ‘Inspiration’ canola (Brassica napus L.) and ‘T-Raptor’ hybrid turnip (B. rapa subsp. rapa × B. rapa L.). Each experiment was a randomized complete block design evaluating four land preparation methods: (conventional till (CT), no-till after burning (NB), no-till after mowing (NM), and no-till without residue removal (NR)), and four planting dates: (1 September (S1), 15 September (S15), 1 October (O1), and 15 October (O15)). Significant differences were observed for the canola seedling emergence, but are not of biological significance. Hybrid turnip seedling emergence was the greatest for the CT treatment and consistently greater than NM and NR treatments. Forage mass in the canola study was greatest for the CT and NB. Hybrid turnip forage mass demonstrated similar trends to the canola. CT had the greatest mass and the NR and NM treatments tended to provide the lowest forage mass. Across both studies, earlier planting dates (S1 and S15) resulted in greater overall forage mass than the later planting dates (O1 and O15). Forage nutritive value overall was lower in earlier planted brassica; however, forage nutritive value was not reduced enough to negatively impact livestock

Interspecific and intraspecific interference of Palmer amaranth (Amaranthus palmeri) and large crabgrass (Digitaria sanguinalis) in sweetpotato

AbstractField studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and intraspecific interference of Palmer amaranth (Amaranthus palmeri S. Watson) or large crabgrass [Digitaria sanguinalis (L.) Scop.] in ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Amaranthus palmeri and D. sanguinalis were established 1 d after sweetpotato transplanting and maintained season-long at 0, 1, 2, 4, 8 and 0, 1, 2, 4, 16 plants m−1 of row in the presence and absence of sweetpotato, respectively. Predicted yield loss for sweetpotato was 35% to 76% for D. sanguinalis at 1 to 16 plants m−1 of row and 50% to 79% for A. palmeri at 1 to 8 plants m−1 of row. Weed dry biomass per meter of row increased linearly with increasing weed density. Individual dry biomass of A. palmeri and D. sanguinalis was not affected by weed density when grown in the presence of sweetpotato. When grown without sweetpotato, individual weed dry biomass decreased 71% and 62% from 1 to 4 plants m−1 row for A. palmeri and D. sanguinalis, respectively. Individual weed dry biomass was not affected above 4 plants m−1 row to the highest densities of 8 and 16 plants m−1 row for A. palmeri and D. sanguinalis, respectively

Interspecific and Intraspecific Interference of Palmer Amaranth (Amaranthus palmeri) and Large Crabgrass (Digitaria sanguinalis) in Sweetpotato

Field studies were conducted in 2016 and 2017 in Clinton, NC, to determine the interspecific and intraspecific interference of Palmer amaranth (Amaranthus palmeri S. Watson) or large crabgrass [Digitaria sanguinalis (L.) Scop.] in ‘Covington’ sweetpotato [Ipomoea batatas (L.) Lam.]. Amaranthus palmeri and D. sanguinalis were established 1 d after sweetpotato transplanting and maintained season-long at 0, 1, 2, 4, 8 and 0, 1, 2, 4, 16 plants m−1 of row in the presence and absence of sweetpotato, respectively. Predicted yield loss for sweetpotato was 35% to 76% for D. sanguinalis at 1 to 16 plants m−1 of row and 50% to 79% for A. palmeri at 1 to 8 plants m−1 of row. Weed dry biomass per meter of row increased linearly with increasing weed density. Individual dry biomass of A. palmeri and D. sanguinalis was not affected by weed density when grown in the presence of sweetpotato. When grown without sweetpotato, individual weed dry biomass decreased 71% and 62% from 1 to 4 plants m−1 row for A. palmeri and D. sanguinalis, respectively. Individual weed dry biomass was not affected above 4 plants m−1 row to the highest densities of 8 and 16 plants m−1 row for A. palmeri and D. sanguinalis, respectively