Comparison of 2-Acetyl-1-Pyrroline (2AP) in Rice Leaf at Different Growth Stages Using Gas Chromatography

Aromatic rice lines were examined for 2-Acetyl-1-Pyrroline (2AP) content in leaf tissue at five different growth stages (tillering, panicle initiation, 50% heading, booting, and maturity). A small plot trial with plot size of 1.42 m × 4.88 m (7 row-plots) was arranged in completely randomize design with three replications. Dry-seeded, delayed flood cultural practice was used in this study. The experiment was conducted at three locations. The average 2AP concentrations in leaf tissue at tillering stages were higher than the other four growth stages. 2AP levels were declined when rice plant reached booting. AP levels decreased slightly at heading stage and decreased significantly at maturity. There was no significant different between 2AP in leaf at 50% heading from three locations as well as the 2AP content in rice grain. Correlations between 2AP in leaf and 2AP in grain were significantly in all five growth stages. The highest correlation coefficient was found between 2AP in leaf at booting and grain (r = 0.811**) and lowest was in the leaf at harvest (r = 0.564**). Results indicated that 2AP could be determined in leaf tissue at early growth stage.

Yield and uptake of bahiagrass under flooded environment as affected by nitrogen fertilization

Bahiagrass (Paspalum notatum) is one of the most important forage grasses in subtropical region of USA and other tropical regions of the world. Although tolerant to short term flooding, bahiagrass is classified as a facultative upland (FACU+) species that suggest yield and plant persistence might be reduced under periods of extended waterlogging. The objective of this greenhouse study (2008-2009) was to determine the effect of nitrogen fertilization (0, 100, and 200 kg·N·ha–1) on yield (DMY), crude protein content (CPC), and nitrogen uptake (NUP) of bahiagrass under varying flooded conditions (0, 14, 28, 56, and 84 days). Results disclosed an overwhelming effect of N application on yield and uptake component of bahiagrass. Averaged across flooding duration, results showed that DMY (R2 = 0.91**), CPC (R2= 0.96**), and NUP (R2 = 0.99**) were linearly related to increasing levels of N fertilization. Plants without N fertilization that were submerged between 14 to 84 days had significantly lower amount of DMY when compared with plants that were fertilized with 100 or 200 kg·N·ha–1. Comparable DMY and NUP were obtained between plants fertilized with 200 kg·N·ha–1) at 0 day of flooding (11.7 ± 5.0 ton·ha–1) and plants fertilized with 200 kg·N·ha–1 at 84 days of flooding (9.8 ± 2.7 ton·ha–1). The practical implication of this study is that waterlogging may hamper yield and uptake while nitrogen fertilization could improve yield and uptake of bahiagrass under waterlogged condition.

Nitrogen recovery and agronomic efficiency of forages with nitrogen fertilization under flooded condition

The cow-calf (Bos taurus) industry in subtropical United States and other parts of the world that depends almost totally on grazed pastures is facing several production constraints like changing climatic conditions and increasing cost of fertilizers, especially nitrogen (N). Particularly little is known about the response of forage species to the combined effect of water-logging and the addition of N. A two-year greenhouse study was conducted in 2008 and 2009 to determine i) the effect of flooding duration on N recovery and agronomic efficiency of bahiagrass (Paspalum notatum Fluegge) compared with two flooding tolerant forages, limpograss (Hemarthria altissima Poir), and maidencane (Panicum hematomon Schult) and ii) if N fertilization could mitigate the negative effect of flooding. Nitrogen recovery and agronomic efficiency varied significantly (P ≤ 0.001) among forage species. Averaged across levels of N, N recovery of bahiagrass and limpograss was reduced by about 41% and 56%, respectively after 84 d of continued flooding while N recovery of maidencane was slightly increase by about 5% between 0 and 84 d of flooding. Agronomic efficiencies of bahiagrass (41% to 26%) and limpograss (44% to 31%) were reduced by flooding while agronomic efficiency of maidencane was increased from 24% (no flooding) to 46% at 84 d of continued flooding. However, N recovery and agronomic efficiency of three forage species was positively affected by N fertilization. The overall N recovery of bahiagrass, limpograss, and maidencane ranged from 44% to 59%. Nitrogen fertilization could improve N recovery and agronomic efficiency of forage species under waterlogged condition.